MBC how much PSI???
 

Hey I am new to this forum and new to tuning but all my friends have been for years and years but I want to learn on my own because everyone of my friends is different and drives different cars so i want to know what other supra drivers do not mazada and honda guys do... Any who my questions is i just got my boost gauge in and running fine. Now I want to put a MBC in which I just got in the mail. I understand how to install it but how much PSI should I run on a stock turbo with new down pipe, full 3in HKS cat back, H&K intake, hard charge pipe and Greddy type S BOV? Currently at 6.5 pounds. Heard of head gaskets going at 12-14 psi. So I was thinking 10psi. Will that be safe???

it doesn't work that way ,
MBC = FCO
try RTFM

um again i am new to this wat is FCO and what does not work that way? I just want to know how much boost is safe with the mods i have.

fco = fuel cut off. its when the ecu kills kills ignition to protect the motor. i cant explain any better at the moment, maybe someone else can explain it a little better. basicly its when the motor reaches the peak of the fuel system and cant match the amount of air coming in, so it kills ignition to protect the motor. a mbc will likely make you hit fco, so just turn it down till you dont hit it. if you feel like turning up the boost more you will need to look into getting rid or around fuel cut

got it so how do you get around the FCO is there an easy bolt on like the MBC and i just ordered brand new OBX plugs and wires will this help?

HKS Fuel Cut Defencer (FCD).
It's a pretty easy install. Plugs into your ECU.

I have it, and an electronic boost controller. I believe however that the stock wastegate actuator can't handle boost pressures over 11 PSI or so. That's a problem I'm dealing with now. (Any suggestions out there??)

I have also heard boosting over 12 PSI is risky to our engines. I have set boost at 12 PSI but it wont hold. Boosts very briefly to 12 then drops back down to about 8.

Anyway, with what your doing this HKS FCD will help and at least boost you to 8 PSI. (At 8 PSI you shouldn't even need the PCD as that is the factory boost max level)

If you want to boost higher get the FCD and I would HIGHLY recomend a metal head gasket with ARP head studs. If you don't do that now you will eventually (probably soon) blow your head gasket and then do it.

We do need to find out what's up with this wastegate actuator. Maybe we need to by-pass it and go with an external blow off valve (BHV). Anybody, anybody?????

I run into the fuel cut problem on stock boost with my current set up. TAking care of other problems before i address the FC one. Would suggest fixing the problem as in lexus AFM mod + 550cc injectors and a good tune rather than putting a FCD on it and turning up the boost

mkiiisupra...what is this 'divorced wastegate' you list in your mods?

I have the lexus AFM, took off my JC 550cc's because the performance shop who installed my AEM EMS and dyno tuned couldn't get them to work correct. He claims that the stock injectors are more than enough. My problem that he can't figure out for sure is my boost wont hold above 8 PSI. (modified turbo to 47 trim good to about 22 psi if I want to blow up my engine) He suggests a 3" downpipe may do the trick (I have stock still, but a big HKS drager cat-back over 3.5 inch diameter) but I'm not convinced. My feeling is the stock wastegate actuator I am running may be the culprit.
(I'm sure the downpipe and a good intercooler with hardpipes will be a great help but I'm not sure that's the root of this boost cut.)

Dyno'd at 252 hp and 318 lbs torgue at 4000 rpm when the turbo boost drops off, dropping HP and torgue a little before rising up again and leveling off at about 252 HP and 252 torgue around 5k through 6k rpm before slowly declining.

Any ideas?

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Current Engine Mods as of July 08

1) Metal HG with ARP studs
2) Turbo rebuild/upgrade by Majestic Turbo, TX to 48 trim.
3) K&N intake/filter
4) Flex-a-lite electric engine cooling fan
5) Lexus MAF (with stock Supra sensor)
6) HKS Super Drager Catback exhaust (95 mm or 3.75 inch piping)
7) Blitz SBC i-D (boost controller)
8) AEM EMS (Dyno tuned)

spudboy: replace your downpipe and turbo elbow with a downpipe with the elbow integrated into it. the stock elbow is quite restrictive and maybe what is hindering you.

a divorced wastegate is referring to the downpipe. basicly it splits the wg and exhaust flow to allow a smoother flow. in stock form the flow is quite turbulent. look here to see a divorced down pipe

also if you have a standalone, why even use a afm? that is limiting you're airflow. and you're tuner said the stockers are adequet? for what? what are your goals? try replacing your downpipe and see if that fixes your boost problem, it will also net you a few ponies and spool your turbo quicker

Thanks j3pz...my tuner said exactly the same things as you: downpipe and get rid of the afm. He said the stock injectors seem to be adequate. We had a seperate problem with the injectors and mutually decided to go back to the stock for now. Still need to figure out the problem with the injectors but one thing at a time.

Did you notice great boost and power improvements with this divorced wastegate downpipe? What boost levels are you running and do you have the stock actuator?

My goal is a good fast street/track road course machine that can compete with modern 350z's, STi's, EVO's, S2000's, et al. A big part of that goal is to also learn about my car and others while doing as much of the work myself as possible. A big part of the fun is showing up at the track with a clean 20 year old car and 50 year old driver (not so clean) and surprising the others.

I've had 5 track days in the last 2 years with the car and driver (me) improving each time but can still do much better I'm sure.