1988 Rx-7 Turbo, running a 60 trim Garrett T4 with an HKS external wastegate. I plan to run about 20psi... currently have a 10psi spring but I guess the 40mm HKS is too small b/c it already creeps to about 13-14psi.

So I had planned on getting an electronic boost controller (Greddy Profec B Spec II), but now I'm thinking about going with a high quality manual one to save money and reduce the amount of wires and hoses I would need. The car will mostly run race gas anyway. My standalone can control boost but the solenoid it needs is $200 and I've been told it's not that great of a controller anyway, plus the wiring would be a pain because I do not have a 93-95 car. I know you can make an MBC out of home depot parts, and I used to have one, but I was not happy with it. It looked cheap in the engine bay and I didn't like the adjustability.

I am considering the Hallman boost controller. http://hallmanboostcontroller.com/Pro%20Series%20Installation%20Instructions%20ld.pdf . One of the issues here is that I am currently running a 4AN stainless line to my HKS external wastegate. Reading through the instructions, I am not sure if I can remove the barbed fittings and install an AN fitting. Or I could just clamp the hose on the barb I suppose. I just want ANY chance of these line popping off.

Also, when running an MBC, what would make it less likely to spike--hooking it to the compressor outlet of the turbo or drilling and tapping the intercooler piping right near the throttlebody? I know on an EBC you want a source near the throttlebody.

Anybody have any experience with the Hallman or another MBC? I tried the Turbo XS MBC before but I didn't like it. It spiked pretty bad, worse than the home depot one, but maybe the one I had (it was used) was defective.

2/16/2008 8:04:21 PM

Close to the throttle body would give you the best part throttle response, I'd go with compressor outlet instead. Try to minimise volume of the lines, make sure there's an adequate vent between mbc and wastegate, and you should be fine. I prefer the response of an all mechanical boost control system however keep in mind a proper electronic system should have superior drivability.
Ahmet

2/17/2008 9:44:11 AM

What do you mean by the response of an MBC? I presume if you have a decent midlevel MBC (not taking an AVC-R,E-01, or even more expensive than that) you could get the gain, crack pressure, etc set well enough that you should be equal or more responsive than an MBC. Currently I have a 4AN line running from the compressor outlet straight to the side port of my external wastegate with no boost controller. The wastegate (10psi spring, genuine 40mm HKS standard series) cracks at about 6psi but under WOT so far it creeps to about 13-14.

See, I keep going back and forth in my mind between the nicest Hallman MBC ($140ish, comes with ceramic ball, two springs, and a cable to accurately control it from the car), the Greddy Profec B Spec II ($300ish), and the AEM Tru Boost ($270).

The Hallman would be easiest installation and would keep down the cost of stainless steel lines and fittings. The AEM gauge-type EBC would be nice because it would replace my shitty autometer boost gauge. Yet I have had HORRIBLE experiences with AEM's customer service when I had a problem with another gauge I bought from them. The Greddy needs to have its own external MAP sensor (as opposed to the internal MAP sensor in the AEM gauge) installed plus it has a separate box I have to mount. It will have the maximum amount of bullshit and clutter of all the setups.

Assuming the Greddy and the AEM have similar capabilities, I guess the only reason to get the Greddy is because I am pissed off at AEM. The Greddy is a little more expensive and would be a more complicated install.

2/17/2008 4:31:30 PM

I am not familiar with most of the models you're talking about. The last boost controller I've used/tuned with was on a 4 cylinder 2.5 liter 8 valve motor pushing 420whp, and it was a $15 ebay manual boost controller, very simple, small bleed line. I've always used the shortest plumbing possible (1/8 inch hydraulic hose from diesel injection), and had absolutely no boost creep. It was on a T04E, custom plumbing, large tial wastegate.

As long the plumbing is done properly, especially wastegate piping away from the turbine inlet (no gas flow reversion when wastegate's open), and the wastegate is big enough, there should never be boost creep with almost any boost controller. I prefer manual, for the same reasons you cited, simplicity, but also response.

Anyway, is the wastegate internal?
Ahmet

2/17/2008 5:09:51 PM

it is external, 40mm. I don't think I've even heard of a .96 T4 hotside with an internal wastegate... biggest internally wastegated turbo I know of is the GT3076.

The real problem is that the HKS cast manifold I am using isn't the best for running low boost, although it almost never cracks and is proven to 500whp. It simply won't flow enough exhaust out the wastegate to keep the boost that low I guess--so even a bigger wastegate won't help that much. The manifold/wastegate combo is undersized, but I didn't have the extra $1500 to spend so I could run a few psi less even though the thing is designed for race gas.

I'm leaning towards the AEM EBC now... I just gotta hope it never breaks on me.

[Edited on February 17, 2008 at 5:35 PM. Reason : .]

2/17/2008 5:34:39 PM

I would think rx7 forums or something would give you not only much better response, but also pointers thats specific to your car.

[Edited on February 17, 2008 at 8:20 PM. Reason : ,]

2/17/2008 8:20:07 PM

trust me, i've looked on there... just wanted a different perspective. I guess there aren't many people running external wastegates on tdub. oh well.

2/18/2008 8:29:19 AM

that hallman is the exact same design as a $10 ebay special.

If your stainless line is the right size and has enough slack, you can slip it over the MBC barbs and use worm-gear clamps. Yes, it seems ghetto, but it's actually an approved connection

If you want the fancy anodized look, then you can spend a couple bucks here
http://store.summitracing.com/partdetail.asp?autofilter=1&part=SPE%2D2260&N=700+115&autoview=sku

I have this one trying to do 18psi. On first attempts last Friday, it would spike to 20ish, come down to 15, then settle on 18. It all happens within a second but it's still unnerving. It doesnt seem to have a bleed hole like the hallman knockoffs, though it claims so
http://tinyurl.com/2m5cqo


[Edited on February 18, 2008 at 8:59 AM. Reason : ]

2/18/2008 8:38:19 AM

you can get a nice adjustable valve for compressors from the paint store. it looks better and is easier to measure adjustments than a plain old home depot ball valve. they're something like ~$20

2/18/2008 1:17:08 PM

Forge UNOS is a nice piece
http://forgemotorsport.com/content.asp?inc=product&cat=&product=FMUNOS

[Edited on February 18, 2008 at 2:13 PM. Reason : i have an account with forge, btw..]

2/18/2008 2:13:37 PM