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arghx
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The last generation Honda Prelude Type SH uses what Honda calls the Advanced Torque Transfer System, or ATTS. This is a front wheel drive vehicle, and front wheel drive has a tendency to understeer. To address this, ATTS uses clutches to engage a planetary gearset in order to transfer torque between the two axles and increase the speed of the outside wheel in a turn. The system uses a lot of elements you find in an automatic transmission.



You can see its location in the front of the vehicle and the hydraulic lines to cool the fluid for the wet multiplate clutches (similar to what's in an automatic trans).



Here you see the two half shafts, a set of planetary gears, the pump used to generate hydraulic pressure, solenoid valves and fluid pressure sensors like you would see in an automatic transmissions' valve body.



Here's a basic diagram of a planetary gearset. In the middle is the sun gear, then the planetary gears connected to a common gear carrier, then a ring gear on the outside. For purposes of this discussion, the ring gear is irrelevant for understanding how this system transfers torque between axles.

A simplified way to explain it is that, if you think 3 dimensionally, there are 3 sun gears next to each other: left, right, and central. There are two sets of pinion gears, left and right. The clutches will engage the left side with the central, or the right side with the central. If I engage the left clutch, I transfer torque/driving force from the left wheel to the right wheel, and vice versa. Due to carefully-chosen differences in the number of gear teeth, it works out that the outside wheel in a turn will be able to spin at ~1.15 times the speed of the inside wheel when the clutch is fully engaged. This transfer of torque and rotation to the outside wheel reduces the understeer tendency.



The above diagram shows the basic structure of the control system. This generation Prelude came to market as a 1997 model, and these are pretty advanced controls for back then. A basic engine torque model and wheel driving force/torque model are used to determine how to engage the clutches. The system also had a yaw sensor and a G sensor to better understand the current driving maneuver. These sensors are more likely to be found in the more advanced AWD or other vehicle dynamics systems of today.

3/1/2015 12:56:22 AM

arghx
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Compare the timing and accessory drive of the Audi 4.0 liter twin turbo V8 engine (420hp), which is a dual overhead cam engine, and the GM Gen V 6.2 LT1 engine (450hp) with pushrod valve actuation. Both engines have cylinder deactivation and variable valve timing.

Here's the Audi chain drive:



So you've got 4 chains, labeled A-D

Chain A - connects from the crank to intermediate gears on the two banks
Chain B - driven by Chain A, drives the cams on Bank 2
Chain C - driven by Chain A, drives the cams on Bank 1
Chain D - drives all accessories except for the alternator

You can see the system of accessory gears connected to Chain D:



The alternator is the only accessory with conventional serpentine belt and tensioner:



Why the complexity? I would think that the use of intermediate gears and separate chains for the cams reduces noise and doesn't have the stress of one big chain driving all the gears, especially with the variable valve timing cam phasers and high pressure fuel system.

For the chain driven accessories I can only speculate that it may have been a packaging issue of some sort--reduces the number of pulleys. Or maybe the chain drive as implemented here was quieter.

Now, look at this cutaway of a GM Gen V LT1 engine:



You can see on the left a small chain driving a single camshaft in the valley, with a simple dual-equal phaser (retards both intake and exhaust valve timing at the same time). The high pressure fuel pump is cam driven but not shown here. Then you have a simple serpentine belt system to drive the accessories. This is a less expensive and less complex design than what Audi uses, especially since it is a large displacement naturally aspirated pushrod V8.

5/10/2015 11:00:03 AM

arghx
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Porsche was the first manufacturer to have a turbocharged engine for racing. The 1973 Porsche 917 was a 5.4 liter flat 12 cylinder rated at 1100 horsepower. It used a setup that may be familiar to many of you with flat engines: an external wastegate controlled by a manual boost controller.



An external wastegate bypasses exhaust gases from the turbocharger wheel to control boost. A spring-loaded poppet valve controls flow. The stiffness of the spring indirectly controls the amount of boost pressure to the engine. The diaphragm chamber is divided into an upper portion and a lower portion. The lower portion can receive boost pressure to left the poppet valve off its seat and bypass exhaust from the turbo. The upper portion can be open to atmosphere, or it can receive pressure to push the poppet valve closed and raise boost.



When the valve lifts off its seat, it sends exhaust back into the main exhaust stream. Porsche originally used a physical screw to set preload in the spring in order to raise boost pressure. Then they used a manual valve to regulate additional air into the upper portion of the diaphragm chamber.

Wastegates of course are standard now on turbochargers, but at the time it wasn't always the case. The Chevrolet Corvair Monza for example, a turbocharged flat engine, had no wastegate, and neither did a lot of diesels. Not all wastegates were controlled with boost pressure; some were actually controlled by letting exhaust backpressure push the poppet valve open by overcoming the force of the spring. So technology and systems we take for granted today had to be discovered by earlier generations of tinkerers.

5/11/2015 10:58:59 PM

arghx
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These days most new mass production gasoline engine designs with dual overhead cams have phasers on the intake and exhaust cam. This means they can move the valve events earlier or later with continuous variation, rather than a "2 step" on/off system. This type of system can be called things like VVT, VTC, VCT, VANOS, i-VTEC, etc.



The cams default to a locking position, typically with no overlap or very little overlap between intake and exhaust events. Then the exhaust cam can be retarded (moved to the right in the image above) and the intake cam can be advanced (moved to the left in the image above), and in some systems the intake cam can be retarded as well.

Usually the cam phasers have some range of authority, usually anywhere from about 30 to 70 degrees. Newer engines tend to have cam phasers a wider range of authority, and require a piston design that doesn't allow the valves to contact the piston. Fully optimizing for fuel economy requires extensive studies on an engine dyno to measure the brake specific fuel consumption, combustion stability, residual gas fraction, etc.

The thread below, which I mentioned on the previous page, has more explanation about cams and what happens when you move cam centerlines around. http://forums.nasioc.com/forums/showthread.php?t=2687550

So here's an example of a full detailed study ("full factorial" is the jargon) at a specific speed and load point:



Take an engine with a 60 degree intake cam advance authority and a 50 degree exhaust cam authority. The four corners of the map above represent four different cam phasing strategies. At the bottom left is the cam running with the phasers at their locking position. This is equivalent to a fixed cam engine. Whatever the default centerlines, lobe separation angle, or whatever term you want to use, is what you get. Since it's a continuously variable system, you can change the cam setpoint to whatever you want (whether it will hold precisely is another matter), but typically 5 degrees is a good step to move during these kinds of studies. A certain amount of time needs to be averaged at each combination, as this is a steady-state analysis. Now you can start moving cams.



Keep the exhaust cam locked and step the intake cam toward the bottom right corner of this chart and you get primarily an early intake valve closing scenario with higher effective compression. There's also a small amount of residual gas (internal EGR).



Move to the upper right corner by retarding the exhaust cam and you get a high overlap and high residual gas fraction (internal EGR), assuming that scavenging isn't going to come into play under these conditions.



At the upper left corner you have a locked intake cam and a fully retarded exhaust cam. With this particular set of cams you get a small amount of residual gas and minimal overlap. With a different design though you may have more overlap. You also have late exhaust valve opening, which increases expansion ratio. With this particular cam design your default position has a somewhat late intake valve closing.

Note that this image above is somewhat similar to what "dual equal" phasers do, that is variable cam phasing on pushrod engines and SOHC engines (Ford 4.6 3 valve, GM and Chrysler pushrod V8). They can only retard the intake and exhaust cam together, and the overlap is fixed.

If you look back at our cam phasing mapping plan you'll see a bunch of diagonal arrows and numbers. That's one possible way to step through all the combinations when testing on an engine dyno. This can be controlled manually or it could be automated. Now that we've illustrated the 4 corners of the map, let's show what a resulting map might look like:



Each set of numbers represents the brake specific fuel consumption (grams/kwh , lower is better), the location of 50% mass fraction burn (crank angle degrees ATDC firing, ~8ish is considered minimum spark advance for best torque), and the amount of combustion instability (coefficient of variance of indicated mean effective pressure in %, lower is better).

So in the example shown here, the engine seems to like the upper left corner the best in terms of fuel economy (red numbers). This is late intake valve closing, late exhaust valve opening, and could also be considered Atkinson Cycle. Under other conditions, maybe the engine likes the upper right corner better. Notice that the edges of the map, especially the upper left corner in this case, have the highest gray number. The combustion can become unstable from overlap or late intake valve closing. If it's bad enough, a driver could feel vibration in the vehicle. Generally 3% is a rule-of-thumb limit, but it depends on the application. Maybe under other conditions your most unstable point will be the upper right corner of the map rather than the upper left.

The black number is the location of 50% burn. It's between 8 and 9 degrees ATDC here. The reason this moves around is that the combustion speed changes as we change the valve events. The spark timing needs to change with it. A slower burn requires more spark advance, which has to be adjusted by whoever is running the engine or by the automation program running.

5/16/2015 6:01:24 PM

arghx
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Back on page I talked about how twin scroll turbos separate exhaust gas pulses on an I4 engine to reduce residual gas in the engine and give better low end torque:



There are a few drawbacks to twin scroll turbos though. The divider in the middle and overall design of the turbine housing causes more restriction and backpressure at high speed. These housings also must be run at lower exhaust temperatures than monoscroll turbos of similar material, and can be more of a thermal sink to inhibit catalyst light off.

So there's another way to accomplish the same effect without some of the drawbacks of twin scroll turbos. By reducing the exhaust cam duration and retarding the exhaust valve opening event, the blowdown pulses will not flow back into subsequent cylinders. Audi uses this principle on some of their newer I4 turbo engines, and advertise it under the umbrella term of Audi ValveLift System.



The diagram above shows conventional valve timing during overlap. The exhaust pulse from an earlier cylinder firing event travels to this cylinder, causes a rise in exhaust port pressure. When the intake valve opens, the exhaust travels into the combustion chamber and results in hot residual gases remaining in the cylinder. That increases the chance of knocking and reduces volumetric efficiency as fresh air is displaced.



In the image above, the top pane overlays the short duration exhaust cam profile with the standard profile. The short profile opens the valve a lot later and closes later here. In the bottom pane, the short profile's cam results in the exhaust pulse not reaching the subsequent cylinder until after the exhaust valve is closed. The result is similar to a twin scroll turbo at lower engine speeds and high load, but without the drawbacks described above, especially at peak power speed where monoscroll turbines are advantageous due to less backpressure.

5/28/2015 4:22:55 PM

Hiro
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I miss these posts...

6/1/2016 6:05:31 PM

sumfoo1
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i'm not going to lie... i really feel that all of the downsides to twin scroll compressors can be made up with other options, turbo blankets shorter exhaust runners etc.

i think fucking with your timing like that would become more of a maintenance issue than anything.

arghx is there any other way we can stalk your intelligence and harass your moving over to the O.E. darkside?

also do you guys do any "engineered to fail" parts.

6/1/2016 8:40:49 PM

arghx
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Quote :
"I miss these posts..."


absence makes the heart grow fonder

Quote :
"i'm not going to lie... i really feel that all of the downsides to twin scroll compressors can be made up with other options, turbo blankets shorter exhaust runners etc."


If you bolt the turbo right to the head on an I4 with integrated exhaust manifold like many/most new turbo engines, you can't shorten the runners, or put much of a turbo blanket on it.

Quote :
"arghx is there any other way we can stalk your intelligence and harass your moving over to the O.E. darkside?"


I don't know if it's the dark side. It's a lot more difficult and challenging in some ways, and much easier in other ways. More difficult because of government regulation, having to adhere to engineering standards that some retired guy came up with in the 80s, that kind of thing. Much easier because if you want to know how a part works, you can literally call the guy. If you need a simulation, you can do it. If you want to know how something is calculated, you open a block diagram. If you want to study something, you run it in a lab with equipment that costs more than your house.

Here's an example. On a port injected engine I've been working on, during warm up the tip-in fuel has to not only drive well but actually pass emissions. On a turbo direct injected engine, some of the features for knock reduction or better fuel economy had to be constrained because it could create noise or vibration and nobody wants to spend the money for something to address that.

Quote :
"also do you guys do any "engineered to fail" parts."


You don't need to intentionally engineer something to fail. That just happens naturally. What if someone told you that you had to design something and it better work great for 10 years on a million cars running around in the real world? All you get is an Excel spreadsheet for quick calculations, maybe one or two rounds of modeling, and if you're lucky some accelerated testing in a lab. By the way though, you won't be able to test it in the real world until a year from now. And if it doesn't meet your requirements, you will encounter extreme resistance to change because it will delay launch and cost millions and millions in discarded tooling.

7/8/2016 8:54:48 PM

sumfoo1
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it wasn't meant to be accusatory as an engineer myself i know life cycle design.

But sometimes cost cutting things that don't fall in line with the life cycle or the rest of the part or assembly seem to be "engineered to fail"

for example water pumps, oil gerotors etc seem to be made of weaker materials that everything else.

7/10/2016 12:27:42 AM

arghx
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Since I work in gasoline engine performance and emissions system development I'm usually bitching at the hardware design guys for making a piece of shit, so I understand where you are coming from

7/12/2016 11:27:53 PM

sumfoo1
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ok so can bus, is it pretty much a universal protocol or?

I'm trying to figure out if engine swaps could get easier or since they're tied to effing everything it's just going to be a giant pain in the genitals.

7/29/2016 7:52:33 PM

arghx
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there are different CAN versions, and the network messages vary with manufacturer and sometimes with model year. Despite all the media hype, CAN networks are not fast and easy to reverse engineer, even though in current models they technically don't have any kind of encryption. Those proof of concept stories where one guy made such and such car hit the brakes took a LOT of work and specialized tools & knowledge.

The OEM has the full CAN database and will give pieces of it to suppliers on a need-to-know basis. Then you need a dictionary of what the messages mean and what they do, and how the commands are issued.

All that being said, over time the knowledge will accumulate. Considering the aftermarket can barely handle electronic throttle, which has been in production for about 20 years, it's going to take a while.

8/1/2016 10:55:13 PM

sumfoo1
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Are speedometers/tachs some digital signal or a simple analog controls voltage/ amperage like the 0-10v or 4-20ma commonly used in building automation

Kinda want to swap a coyote into another obdII ford but am trying to figure out how hard harness splicing will be.

From what i read it's relatively easy with only a couple changes in the pin-out (sohc modular to coyote)

Using the coyote control package so that includes the DBW pedal maf and ecu for the coyote.


[Edited on August 2, 2016 at 12:05 AM. Reason : .]

8/2/2016 12:02:59 AM

Hiro
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Dakota Digital has plug and play options, but they can be $Texas

8/2/2016 11:42:28 AM

arghx
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I don't know the specifics of the application, but on modern cars the speed comes over CAN message from whatever module(s) is controlling vehicle dynamics (ABS, stability control etc). There are individual wheel speed signals, torque reduction requests, transmission input shaft signals, all that stuff.

Early 90s through early 2000s typically have an analog signal for speedometer. Before that you have a lot of cars using an oldschool speedometer cable.

8/2/2016 9:54:06 PM

sumfoo1
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Cat before or after turbo for faster spool?

If the cat re ignites the mixture it seems like it would help spool but choke the turbo sooner.


I don't deal well with emissions voodoo halp!

11/1/2016 12:37:28 PM

arghx
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Quote :
"Cat before or after turbo for faster spool? "


After. The cat absorbs thermal energy from the exhaust, and you will have to run richer to protect it, or it will melt and blow up your turbo. Cat before is like the last resort (ie, some Subarus) when the OEM couldn't meet emissions and didn't want to do much redesigning of the engine. You can only do that on an engine with a crossover pipe (usually 2-bank engines) where you can actually fit it in there.


[Edited on November 9, 2016 at 2:17 PM. Reason : .]

11/9/2016 2:11:31 PM

arghx
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Today I want to talk about torque converter torque multiplication. There are gazillions of sites and videos about what a torque converter is and what it does. The torque multiplication effect deserves some extra attention. Here's a Youtube video called "How does a torque converter stator work?"



It shows how the stator, the fixed part in between the spinning engine side and spinning transmission side, directs fluid in such a way as to add torque. This happens when the engine side is spinning faster than the transmission side which ultimately connects to the wheels. To illustrate this relationship, we can use data from a relatively modern but still basic 6 speed front wheel drive auto transmission mostly found in frumpy sedans.

Test Bench



In this case, the transmission is being spun on a test bench where the input and output shaft speeds can be independently controlled, with the converter clutch open (converter is not locked up, top pane of image). The input shaft speed is fixed at 2000rpm, while in 6th gear with a fixed hydraulic line pressure. With the gear and final drive applied we have a fixed difference in speed (speed ratio is 1). Then the test bench can lower the output shaft speed, reducing the speed ratio and raising the multiplication effect. The baseline relationship with closed torque converter can also be measured (bottom pane of image). By running output shaft speeds we can build a map of the torque multiplication relationship.

Data



The bottom x axis is the ratio of speeds between the input and output shaft. Remember, the input shaft speed is held fixed by the test bench, and the output shaft is affected by the gear ratio (around 2.2:1 here). So a 1.0 ratio is not going to have the input and output shaft spinning at the same speed. If the ratio is less than 1, it represents the torque multiplication effect of the converter, not any kind of gearing change, when the torque converter clutch is open.

When the torque converter clutch is closed, the input shaft speed needs to be varied to get the output shaft speed labeled on the top of the X axis.

The Y axis is torque. The test bench dyno motors can apply torque on the input side, and absorb torque on the output side. So looking at 1.0 on the graph, starting with the engine and transmission side spinning at the normal (gear related ratio), we look left at the green line and red lines. That increasing separation shows the multiplication effect. The increase in the red line (input shaft torque) reflects reactionary forces from the output shaft as a result of the torque multiplication effect.

As a reference, look at the blue dotted line and the top X axis. This is just varying the input shaft speed with the converter clutch locked.

Now look at the efficiency plot (lower ratio efficiency can be extrapolated).



This number is a comparison of the power put into the system vs the power put out. The output torque is going up but the output speed is going down. From the perspective of overall efficiency you can see why you would want to run at a speed ratio of 1.0 (torque converter locked), and that's why the newest autotransmissions have a locked torque converter in most areas of operation.

From the perspective of getting more torque to the ground through multiplication effect, you want to expand that gap between the green and red lines in the second image. That's what changing the design of the torque converter stator does, and it's a frequent change used in drag racing applications.

[Edited on November 9, 2016 at 3:03 PM. Reason : .]

11/9/2016 3:03:00 PM

arghx
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the youtube embed works for me if you are having trouble pulling up the torque converter video here is the link

https://youtu.be/vp_tHMkOjB8

11/10/2016 9:47:49 AM

arghx
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per a request via PM about a transmission concern, the inspection procedure for synchros on a manual transmission Acura Integra:



I've disassembled a manual trans before but never rebuilt one myself, although I've had a shop build one. You can see there are clearances and inspection procedures. I'm not sure if having out of spec clearances would correlate to gear grinding or not, but it's certainly food for thought.

[Edited on November 10, 2016 at 10:00 AM. Reason : or maybe they were barely in spec at the time of rebuild and through wear are now out of spec]

11/10/2016 9:56:26 AM

Dr Pepper
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Quote :
" per a request via PM .... manual transmission Acura Integra:"


C'mon Teg, we know it's you

11/10/2016 11:38:57 AM

Hiro
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^TROLOLOL CALLED OUT. PWNT!

Quote :
"or maybe they were barely in spec at the time of rebuild and through wear are now out of spec"

Yeah. Definitely this. Synchro rings are trivial in cost vs function/effort later to fix (kits about $200ish for all gears).


[Edited on November 10, 2016 at 3:36 PM. Reason : .]

11/10/2016 3:31:41 PM

arghx
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You know all that nasty black soot stuff that comes out of your tailpipe on these newer gasoline direct injection engines? The newest emission regulations are trying to reduce that, not only in situations that occur in controlled lab tests, but also for real world engine speeds and loads.

One of the ways to do this is to optimize the start of injection timing (SOI), the number of injection events, and the mass split between them. The images below show an optimization test at 1200 rpm, wide open throttle. That exact condition is not too common in the real world, but you can see some interesting trends.

In the example below the engine is run in a lab, running 20 seconds steady state (sitting there at WOT using systems to cool the engine) at each point with a fixed spark at TDC (0 degrees advance). The points in the scatterplot have different injection timings and mass splits. The Y axis is the injection mass split %. 100% would correspond to a single injection event. The other points have two injection events, where 80% on the Y axis would mean 80% of the injection pulsewidth is allocated to the first event, and 20% is in the second event, and 50% would be an even split.

The x axis is the start of injection timing in degrees BTDC firing, the same units we normally associated with spark timing. As you look towards the right, the injection timing is earlier. As you look towards the left, the start of injection timing is later. The black numbers are the brake mean effective pressure (proportional to measured brake torque, higher number = good), the red are the soot (higher number = bad), and the gray are the combustion instability (higher number = bad). Most of those numbers (black, red, gray) should be compared in a relative sense to the other points in the matrix. You want the highest BMEP, the lowest Soot, and the lowest combustion instability, or some compromise among those choices.




So in the upper right corner is a baseline condition, running a single injection event. We know it's a single injection event because the mass split is 100% --> 100% of the injected fuel is in the first event. The injector starts firing at 260 degrees before top dead center. Although the combustion instability of 2.7% is acceptable it is not great. If it's over 3.0% as a general rule you can feel vibration or torque fluctuation in a car. That's a general rule of thumb.

Then in the rest of the matrix you see two injection events. The first injection timing is still fixed at 260 degrees BTDC, while the second is varied from 220 to 80 degrees BTDC. We don't fire the second event earlier than that so the injector has enough time to respond, as this engine doesn't have expensive piezoelectric injectors. When the second event starts much later, we get lower torque, and what's not pictured here are the high exhaust temps as so much combustion is pushed out the exhaust valve (similar to what is done during a cold start). The later injection also has higher soot, as the fuel is impinging on the piston top or cylinder wall.

An even 50/50 split with the second injection firing 60 degrees after the first shows the most optimized point of stable combustion, low soot, and high brake mean effective pressure/brake torque. This is circled in blue.



This chart shows the soot and combustion instability, but also shows the location of 50% burn instead of the brake mean effective pressure. The units are in degrees ATDC firing. Considering these all have a fixed spark at top dead center, a higher number corresponds to a slower burn (which is generally not good) and a lower number corresponds to a faster burn (which is generally a good thing).

We can see from this chart that the highest torque point with the most stable combustion and low soot-producing impingement also is the fastest burning. We know this because the number "22.4" is the lowest among the points, meaning that half the mixture is burned 22.4 degrees after top dead center, with the spark fixed at TDC. In contrast, the upper left corner of that matrix with a low mass late second injection has a 50% burn location of 33.3 degrees. So it's burning much slower. Meanwhile the baseline is 27.8, meaning we've advanced the combustion about 5 degrees (almost like advancing the spark 5 degrees).

12/14/2016 10:13:36 AM

arghx
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If any of you have ever seen the Youtube series Engine Masters, you may have been curious to know more about the engine dyno facilities used at West Tech performance. In the show several guys do before-and-after wide open throttle power and torque runs, usually swapping around parts on an engine.

Engine dyno work is a very "insider" thing as it is not as widely used for home projects and aftermarket performance. It can be a lot more expensive to set up than a new shop trying to find a used Dynojet, setting it above ground and being able to take any customer's car. Doing work on an engine outside of a vehicle is a more narrow application.

You'll see in the Engine Masters series they are always working on older American engines, almost always with a carburetor. This is no accident. Carburetors are cheap and simple, and suit the clientele for that kind of work (drag racers and such). With a carb you don't have to worry about the ECU freaking out because it's not seeing the normal inputs it gets from running down the road in a real car. Pretty much any OBD II engine's stock ECU is going to be unhappy running on a dyno, but as you get into the era of electronic throttle controls (past 10 years) and integration with stability control systems they are even more difficult to get working on a dyno with a stock ECU. So that explains the kind of engines you see on the show.

Now, it still IS possible to make a modern stock ECU work on an engine dyno. However this is done in a few ways that are not straightforward:

1) reprogramming a stock ECU (perhaps modified for additional memory used for testing) with a special tune to turn off all the check engine lights and disable certain self learning functions so that it doesn't freak out. For the most part only the OEM can do this.

2) literally taking the engine out, putting it on the dyno, and extending a bunch of wiring harnesses from the vehicle into the engine dyno test cell so that the ECU still sees all the connections. Then you have to simulate certain other signals such as vehicle speed and G sensors so that the ECU doesn't freak out and go into limp mode. This method is very expensive and time consuming; only a few labs in the world know how to do this method for the newest, most complicated engines. OEMs will pay for this kind of testing when they want a report on their competitors' engines, using their competitors stock ECU.

1/15/2017 11:59:36 PM

arghx
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Now I want to go through the above ^ video discussing the engine dyno facilities. I'm going to give timestamps and insert comments.

0:46 First, I'll make some comments about the engine and equipment shown on the screen. The engine isn't actually hooked up to run, so there are a bunch of loose wires hanging around. Looking on the rack in the middle of the screen, it looks like some 12V power supplies and electronic ignition boxes (the kind of thing you expect on a carb + distributor engine). Also, I find the Autometer style analog needle gauges surprising. What are those there for? Are they just for reading while the engine is running and there is someone in the test cell at low rpm? You can't see them from the control room. Maybe all those measurements are going into the computer system digitally, and the analog needles in the test cell are just there for convenience.

1:32 He's talking about the brand of Dyno (SuperFlow) and explains that it is a water brake dyno rated for a lot of power. The other kind of dyno is an electric motor dyno. That kind of dyno actually generates electricity when the engine is firing and can return that electricity back to the power grid. It is a much more expensive and versatile type of dyno. It can spin an engine all through its rpm range and measure parasitic losses (motoring friction). The engine doesn't require a starter for example, so you don't have to tune the cranking of the engine to get it going. You can also spin the engine without it firing in order to check for leaks. However, electric dynos typically aren't rated for that kind of power. The dyno they have meets their needs.

3:00 he's talking about "the old days" of 30 years ago. Now I wouldn't know firsthand how things were, but you've got to figure that labs for aftermarket use are decades behind what R&D labs are doing. A bunch of guys standing around looking at needles on gauges and writing stuff down, well that's probably what Henry Ford was doing when he was developing the flathead V8. You still had analog chart recorders and other crude methods to record data, starting at least in the 1970s. So what he's describing is a reflection of his experience, but not a reflection of how all engine dyno labs worked in the mid 80s. They were using computers back then.

4:10 the actual dyno load cells and other components can last a really long time if you do the maintenance. However, other stuff in the lab tends to go out more frequently. Anything involving heating and cooling will fail more frequently, and the really sophisticated labs with sealed environmental chambers will nickle and dime you to death with broken air pumps, chillers, etc.

5:50 "We don't actually simulate atmosphere, we correct." That means they didn't have the money to put in a combustion air system. The combustion air system is a separate HVAC system that supplies air directly to the engine inlet via a hose or sort of external manifold. These systems control temperature, humidity, and pressure. So SAE standard temperature is 25C and pressure is 99 kPa. That's basically a June day in Detroit. The link below can calculate what your ambient pressure is at different altitudes.

http://www.mide.com/pages/air-pressure-at-altitude-calculator

Now of course you can "correct" for being non standard, but if you actually read SAE J1349, the correction factor should be within 3%, and there are acceptable tolerances. The STD correction factor he is talking about is from a different document (j607?) and is based on 103kpa atmospheric pressure and 15.5C/60F , so pretty much winter in death valley (very low altitude below sea level which is 101kpa, and thus not a realistic condition). Only lab combustion air can get to 103kpa.

Now only in rare cases do you have a test cell that is completely sealed and can raise and lower the ambient pressure of the whole room. See above comment about how hard those are to maintain. We're only talking about the supply air.

Another thing he doesn't mention is control of water and oil temperature. If you look very closely in some of the dyno videos, you can see their display in the control room showing water temperature at around 160F/71C, which is way cooler than a car is going to run. They're doing this because either they want to reduce engine knock (understandable) or their control system can't maintain a more realistic temperature (at least 180F/82C) without a lot of oscillation, or they haven't taken the time to tune the water temperature control system to something realistic.

The only real torque is the kind you actually measure. Correction factors get real sketchy, real fast. Look at any high altitude runs reported on a Subaru forum.

6:45 "For a lot of the OE's, SAE [correction] is where it's at." Yes, but only if they do a certified witness test can you somewhat trust those numbers. And that's mostly the big 3 who do that. There are a lot of tricks for overrating your engine in an engine dyno environment for advertising purposes that the OEM's use. That's the subject of another post I think.

6:58 This is a pretty old school control panel. Notice the analog needles and the lever at the left to control throttle. Later you will see a single computer screen. Most R&D labs have a small control panel like this and up to 5 computer monitors. 1 will be just for the ECU, 2 will be for the dyno control system, 1 will be for the cylinder pressure/combustion analysis/oscilloscope system, and 1 will be for the emissions measurement system.

7:40 On that screen are basic temperature and pressure measurements, plus measured air fuel ratio and exhaust temperature. There are a few analog looking gauges on there and digital readouts. What you don't see are second-by-second strip charts. Also as I mentioned, there are no measurements from an engine ECU, emissions measurement, or anything from oscilloscopes and combustion pressure. However since they are mostly doing WOT pulls for power you don't need a lot of that stuff.

8:05 He says the computer is taking 100 measurements per second. That depends on what the bottlenecks are for individual measurements. For example, if his wideband oxygen sensor system (the "ECM" box you saw earlier) is sampling at a slower rate than that, he's limited. Much of it will be buffered and averaged as he mentions.

8:30 60 channels (including actual measurement and calculated values) sounds like a lot, but it all depends on the context. Like he said, half of them he doesn't use. Since there is no combustion, emissions, or ECU parameters, yeah 60 a significant amount. However with more equipment hooked up it's more like 200-300 is going to be common on a modern engine, depending on number of cylinders and the nature of the testing plus complexity of engine hardware. If they were doing detailed thermal testing for example it could be an additional 100 or more channels just for the temperature measurements. With that amount of data you need special tools to process everything and get something useful out of it quickly, and it's really easy to get disorganized.

8:45 he mentions trimming cylinders for fuel and spark. I would be interested to see how they have their test cell configured when they do that. Are they running something like a Fast XFI standalone ECU's control software on a different PC and then sending the data to the main dyno control PC?

8:52 he says an "older way" is to look at exhaust temperature. I think he was referring to 10 or 20 years ago when wideband o2 sensors weren't available and you couldn't measure air/fuel ratio cheaply, without an emission measurement system (they dont have one). In those cases a richer mixture will make a cooler exhaust temperature, and a leaner mixture will make a hotter temperature, all things held equal. But exhaust temperatures still matter because you can damage components if you get too hot (valve seat etc).

9:37 I totally agree that being able to acquire all that data on a dyno saves so much time compared to his customers again and again testing on a track without enough measurement. There's a specific kind of customer who wants that though. It's not the broke college student with a 2003 WRX.

11:12 He's talking about safety when the engine is running. Some people are IMO way too reckless about being inside a dyno cell while the engine is running. Union rules in one lab I can think of was that you couldn't be inside the cell if the engine was over something like 1700rpm, and you couldn't be in there if it was at wide open throttle. Whatever is wrong with the engine isn't worth risking your life over, and whoever is pressuring to get the work done can chill the fuck out.

11:30 "We can actually run open headers" That means they didn't spend the money for an exhaust system vent. There could/should be a system in the building suctioning out the exhaust into the atmosphere.

12:00 He's talking about how the cell was designed to run full exhaust systems, which from his perspective is unusual. It's unusual for performance tuning shops maybe, but larger labs at component suppliers, R&D facilities, and OEMs as I mentioned are going to run full exhaust systems all the time and evacuate the gases into the atmosphere. The test cell in the video does have an air handler in the cell moving air out, which is normal. They rely on that exclusively to prevent leaks of carbon monoxide into the rest of the building, rather than a dedicated exhaust vent.

[Edited on January 16, 2017 at 12:04 AM. Reason : .]

1/16/2017 12:00:25 AM

arghx
Deucefest '04
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13:05 He brings up good points about the physical feedback of being connected to the throttle valve through cable, and how it helps him feel if there is something wrong with the engine. Keep in mind though that you can't get precise control over engine load if you are relying on the operator to physically move the throttle open and closed. On newer engines the dyno computer will send a signal emulating an accelerator pedal input to the ECU. Then control loops can set a specific speed and torque target, so that you can optimize part throttle for driveability, fuel economy, etc.

He refers to a servo motor for a manual throttle cable. Well if you're only doing WOT pulls then yeah I can see how that wouldn't add much value. However if you need to optimize other areas of engine operation using a physical cable is just a hassle. More advanced test cells will let you script a series of actions and optimization tests so that you can press a button, go home for the night and come back to a bunch of data in the morning.


Overall, great video. Hopefully my comments will give more context to how his dyno setup compares to others.

1/16/2017 12:03:56 AM

arghx
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Let's talk about camshafts and low end torque. Bigger isn't always better. We know that, but it's interesting to see it illustrated.

Long duration cams with the intake valve closing long after bottom dead center is not good if your goal is trapping the most air in the cylinder. One way to find the best theoretical valve timing is by measuring the volumetric efficiency of the engine with different cam centerlines and different lift/duration profiles. Below illustrates a fixed intake centerline with varying intake cam duration/lift profiles and a fixed exhaust. Notice that with the different intake profiles, the opening and closing timing of the valve will vary, but the centerline (a straight line through the point of peak lift) doesn't change. Now let's move on to the different combinations of intake centerline and cam profile:



Here is test bench data from a gasoline V8 engine using 7 different cam lift/duration profiles with the intake same centerline, shown here on the Y axis. Exhaust valve timing remains the same in each case. With each profile the intake cam can be at a baseline position optimized for higher rpm or the centerline can be advanced up to almost 50 degrees. Engine speed is 2400rpm, which is realistic for "stump pulling, get off the line" scenarios. The engine is operating as an air pump here; it is not firing, so exhaust gas dynamics (scavenging effects etc) are not a major concern. This method isolates the effect of the intake-side valve timing.



The cylinder filling % is calculated by taking the engine control unit's measured mass airflow (from a hotwire type mass airflow meter) and dividing it by the theoretical pumping according to engine displacement etc.



The peak pressure in the cylinder is calculated by taking the peak pressure measured within a 200 cycle window from a cylinder pressure transducer located in the spark plug.


So what can we learn from these graphs? Well, when the engine is only pumping air, the valve timing of best pumping also has the highest cylinder presssure. At an engine speed like 2400 rpm, the biggest duration with the latest valve timing really sucks for pumping --> compare the 69% volumetric efficiency in the upper left corner with the 93.4 % volumetric efficiency circled in green.

Also, notice that on the far right column with the most advanced cam centerline, the longest duration cam is still too long--the upper right corner is at 93.0%, while the circled green is 93.4% with 16 degrees shorter duration (and thus the closing and opening timing are affected from this despite the same centerline).

In this case, the pumping efficiency (motoring condition) of the engine is more sensitive to change in intake cam centerline than it is to change in profile.

What does that mean to you? Well, there's more to a cam than its lift/duration profile. Those big numbers thrown around for marketing purposes aren't everything. The timing of the valve events has a huge effect, especially the centerline of the cam (or lobe separation angle depending on the context).

2/6/2017 8:26:17 AM

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