Stu Hagen

OK, Here is what you need to do to get adjustable boost on your #1 wastegate (EBV) I am not sure what I paid for the Turbo XS MBC (manual boost controller) It wasn’t much. You will see it in the pics.
Many reasons why I did this mod, but the driving force was I wanted "some" pre-spool, yet increase the stock boost from 11.7 PSI. The famous "EBV" mod that a lot of people do, closes off the #1 wastegate totally, no pre-spool at all. This is somewhat harmful to the #2 turbo, because when the IACV and the EGCV open at 3800 rpm, the #2 is somewhat at idle. So all the blast of air "jump" starts #2 which eventually can cause premature breakage, or most likely a bent shaft. I have seen dyno charts of people who have this, and they actually get 20+ PSI on there #1 turbo! The curve really falls off with that high of boost, but it is a "rush" to get 350whp at 3000rpm.

So what I did, was dig down into the EBV actuator itself. It is buried deep down by the firewall. You have to take the metal loom off, except you keep the 2 EBV hoses and the 2 Pressure tank hoses still attached. You have to remove the rear turbo coolant hose and the coolant hose from the head. This is very simple. It just helps to get a pair of long needle nose pliers down the actuator.

You pull off the pressure side hose from the EBV actuator, It is the hose on the right. You must cap-off this hose you pulled. 2 ways to do this. Either push on a vacuum "cap" on the metal loom pipe, or stuff a bolt into the hose you pulled and tie wrap it on. Keep in mind this all is done in fairly tight quarters, not much room to deal with. So whichever seems easier. The goal here is capping of the pressure supply so you have no leaks.

Now you cut a piece of vacuum hose about 3 feet long. You install one end on the EBV actuator where you just pulled the hose. You then run this hose up front to the "Y". This is the main pressure source that feeds the Pressure Tank AND (use to) EBV.
This where you attach the other end to the "output" of the MBC.

You pull off the vacuum hose in the "Y" that attaches to the metal loom. This is where you need to install a "Y" vacuum adapter. One goes to the "Y" one goes to the "loom" and the other goes to the "in" of the MBC. That’s about it!
You also need to "cap-off" the VSV since that is the OEM EBV controller. You are not using it anymore. This is the one close to the fire wall on the Turbo side of the car. It is easy to see, because it has like 3 hoses running parallel. See diagram.

You can set the MBC wherever you want. I have mine set at 16psi on the "in" and 12 psi on the "out". This basically means I have a 4psi differential. So when I see 16psi of manifold pressure, the EBV will see about 11.7psi, or "pre-spool" since the EBV is designed to open precisely at 11psi. The higher you set the MBC the more psi you need to open the EBV. Make sure that you pretty much close off the "bleeder" side of the MBC.

The goal was more HP and TQ at lower rpms. I have 4 dyno runs back to back showing the different HP/TQ based on the MBC settings. The one graph is "stock", which is obvious. The others are only "slightly" different because I was trying to set the MBC right at 16 psi. So the variance was only +/- 1 psi. So not a lot of HP/TQ to see on the dyno. I know If I cranked it up to 18+ I would see maybe 350 whp at 3200 rpm.

BTW, It took me about 2 hours, and really the cost of a MBC only.

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__________________
1997 TT 6 Sp
Jewell Green Pearl
BPU++++ 491 whp 543 tq (513 whp 567 tq uncorrected)
1/4 mile 12.34--1.99-60'--119mph (street tires-S0-3's) Best Run: ET 11.67 Trap 125.22 1.89 60' M/T Radials


Technical Info/Scans & Specs @ http://www.97supraturbo.com/

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Stu Hagen

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Stu Hagen

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Stu Hagen

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toyotafan

Nice work Stu, this seems to be a better method than the EBV mod because you can use the MBC to dial in somewhat higher boost on #1 and still maintain some prespool.

__________________
95 Black/Black 6spd
BPU+++ 450rwhp 474rwtq SAE

Steve Theodore

We need to promote this into the Tech FAQ. I'll work on that after more people get a chance to see it. Great mod Stu...I'm hopeful for a ride in your car soon to feel the difference.

Steve T.

Steve Theodore

Temporarily moved back to MKIV section for Stu to upload more pics/descriptions.

Steve T.

::MySTiK_[SuPRa]::

Nice work Stu.

Better have some good tires under there with 350rwhp @ 3200rpm


-Phu

__________________
-Phu Bui
1994 6spd TT
"BPU++" (FMIC, SFC Untuned)
402rwhp / 400rwtq @ 1.25 kg/cm^2 SAE Corrected

Stu Hagen

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Stu Hagen

Once you pull off the hose on the EBV and install the 3' hose back onto the EBV, you can run it underneath the metal loom and tie wrap it so you really don't see it. You can instal the MBC wherever, but I chose to put it up front for easy access.


You can see where I put one of the 4 hose caps in the lower left hand side of the last picture. 2 go to the metal lines, and 2 go on the VSV itself, just so dirt and stuff does'nt collect in the VSV relay.

If you are real motivated, you can install a Mechanical Boost gauge onto the metal loom where I said you see the cap in the lower left. This is where you can pick up your pressure readings of the opening of the EBV. That capped off line is where the left side of the EBV actuator goes to. This is the "relief" side of the actuator that normally is opened and closed by the VSV switch.
I have my Defi Boost Gauge installed there temporarily so I can monitor the opening of the EBV vrs. RPM vrs. Boost Pressure.

Stu Hagen

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x X CLoud X x

nice pics, very detailed as well.... im sure many can benefit from this

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my avatar is too big i need to read what size it should be asap! :D

rwsupra.com

Stu you are the man of the hour, I must say......

crossways

Since most assume that when both turbos are pushing past 18psi they are overspun past their efficiency, what would you think is the efficiency point of just the first turbo alone?

Stu Hagen

I should mention a good thing to do prior to installing the MBC, and that is to calibrate first. The bad deal is that you really need two gauges to do this. I have a MityVac ($58) that has both pressure and vacuum abilities. I attach this to the pressure side of the MBC, and put a mechanical gauge on the output. I pump up the "in" to your setting you want. Like if you want 16psi, you slowly turn the set screw until you see 16psi, then you will see 10 psi+/- on the out. Or in other words, you pump up the pressure side until you see 10psi+/- on the "out". Then by adjusting the set screw, you slowly increase the "in" side to your desired boost level. For every 1/4 turn, you increase the "difference" by 1 psi. This is how you would make the fine tuning of the transition. If you wanted a bit less boost on #1, then I would recommend 13 psi "in" to see 10 Psi "out". I wouldnt go any less because that is getting pretty close to "stock" under load. I know this sounds confusing, but you will figure it out once you get to doing it.

I can also take a pic of both gauges showing both settings so you can have a better Idea of what it looks like, settings wise.

PS This MityVac tool is an awesome tool to own! It is a good investment because of all the lines/actuators on the Supra.

supratter

will these work if I'm running TTC??

Stu Hagen

NO....>> TTC runs "all" actuators open, so both turbos spool simulataniously.

supratter

just what I thought!!

Thanks alot for clarifying that