gt4088r install......

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89supra7mgte

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Sep 20, 2009
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Ok so i i just got done installing my new gt4088, upgrade from the 57trim ct i had. (supporting mods, 560s, lex, lc1, safc, aem tru-boost, full exhaust, ic kit, walbro, afpr) I have my safc zeroed, need help with a basic tune (just drivable to dyno). I noticed that my vac has dropped as well from 14 to 10, is that due to bigger turbo? I ran the boost solenoid according to aem manual, bottom can with turbo psi on port 1 and top can can on port 2.

My idle afrs are 15.7, gonna sort out the cause for low vac, before making any adjustments.

So any and all help will be greatly appreciated thanks
 
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89supra7mgte

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Sep 20, 2009
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it was prior to this setup, now it is at -10. just wondering if the turbo is causing this or if i have the wastegate hooked up backwards? i am going to pinch off the lines and see tonight. it idles fine and doesnt seem to have issues. have not driven and wont until i get it sorted out.

Also the inlet of the new turbo is 4inch where the old ct was around 2.5inch will that make a difference?
 
leftynridge

leftynridge

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Aug 30, 2009
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-14 still seems to me kinda low. My car would sit and idle at -20.8 which is a little on the high side, but I would expect at least -18 to -19. You must have a vacuum leak somewhere. You might want to do a pressure test on it and see if you can find any leaks.
 
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89supra7mgte

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Sep 20, 2009
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my old setup was 14 at idle 18-20 on decel. the only thing that has changed is turbo, exhaust and exhaust manifold. only pipes i had off were the charge pipe from turbo, and cold pipe to tb. all couplers and clamps are tight. idle is smooth and doesnt seem to hesitate when bringing the rpms up?

When i get off work i am going to check the wastegate and do a triple check on the ic pipes. along with pcv tubing see if one split or something stupid.

Also would anyone know of a good settings on safc just to get it to the dyno? or should i just monitor it by afrs? also noticed that on the lo th settin if i add fuel at the 1k mark the afrs drop back down to 14.7? on the setup i have lo th starting at 65% and hi at 70% (what i was told in older posts) I am settin something up wrong for it to be correcting at 0% throttle?
 
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mkIIIman089

Supramania Contributor
Mar 30, 2005
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The only way to lose vac like that is from a leak AFTER the throttle plate. IC pipes, wastegate hookup (providing youre still using compressor housing as a feed) and PVC have absolutely nothing to do with vacuum at idle, which should be at least -16in. 15.7:1 A/F is lean however I have seen a lean condition occur at low idle (no lights, low electric load) with a lex AFM so there is potential that even after you fix the vac leak that wont change.

You should have left the SAFC alone, but if you no longer have the old settings, leave it alone for now. Your issue has nothing to do with it.

From memory my car is -17 at idle, and -24 at decel, for reference.
 
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89supra7mgte

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Sep 20, 2009
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I have rechecked for leaks none found. after letting the car warm up the afrs went rich then stabled around 14.6 safc all zero. i can reset it back to my old settings with the ct turbo but do believe that i would have lots of issues right?

My vac is not at 11. there is no port on turbo for boost so i have it ran to manifold, not what i would like but have no choice in the matter right now. car seems to idle fine. just a little nervous to take it out on the streets without knowing for sure that ill be safe and tune from there. when giving it rpm my vac stays the same unless a quick pedal to 3k.

If the car is safe to take in a professional opinion i will turn the boost down and street tune from 0 correction. then take to the dyno
 
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mkIIIman089

Supramania Contributor
Mar 30, 2005
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Was it only set for tune at the hi throttle setting? If so, no issues, the bigger turbo at the same or higher boost should just trigger the ECU to run a tick richer.

There has to be a leak, either in that line you ran from the manifold to the wg, or a stuck vsv (VERY unlikely) or something. Vacuum doesn't drop unless something that was air tight... isn't any more. Running the WG like that shouldn't hurt anything but you'll need to start from scratch on wg duty cycle and gain settings.
 
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89supra7mgte

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Sep 20, 2009
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I took it out!!! Damn i dropped the boost to 8psi to be safe and watched the afrs as close as i could with only me in the car. with the tuner at zero i run way rich which is good, for now. My buddy said he was adding fuel? He was also running a bone stock 7m with an emange (no fuel mods or lex)

As far as the tune goes it was set for hi and low.

Back to the basics on the safc, initial setup so i know i have that set right? And should i keep the hi and lo throttle setting at 65% and 70%? and why does the safc start to take affect if i adjust fuel at idle? i can hear the change in engine tone.

Bad thing about this turbo is the lag. but i am impressed with it either way. son of a bitch screams.
 
leftynridge

leftynridge

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Aug 30, 2009
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dayton, ohio
Well I can tell you when I first purchased my 88 I went through and checked for leaks and cracks on the intercooler piping, couplers, vacuum lines you name it an I thought that I did everything but the car was still sitting at like -16 at idle. Then I took it over to a friend house and did a pressure test and boy did the leaks start to come out. There were tiny pin needle cracks in the intercooler piping, couplers not tight all the way, and vacuum lines that needed to be replaced. It then went from like -16 to -20 at idle. So even if you think that you have checked every nook and cranny you should check again. It my not be an obvious fix. It could be a tone of little small leaks. After all these cars are 20 years old. What are you doing to check for leaks? If you are not pressure testing the system then you will never figure out where all the leaks are located.
 
leftynridge

leftynridge

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Aug 30, 2009
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dayton, ohio
One thing to think about is when you are sitting at idle there is no positive pressure in the system but as soon as you start to boost you are now in positive pressure and this when the leaks will begin to expose themselves. However, you will be in the car and will not be able to locate them. I bet if you had a camera under the hood while under boost you would here hissing snakes everywhere. This is why its important to do a pressure test so the hissing noises can be located. Another thing that you would want to do is pressurize the system to at least the amount of boost that you will be running. If you are only running at 8psi with this turbo you are not even cracking into what this turbo is able to do. Plus if the air is escaping somewhere its going to feel very laggy. But a quick spool valve will most defiantly help with this turbo. Fix the leaks first and then make the call.
 
8

89supra7mgte

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Sep 20, 2009
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colorado
where can i find a qsv? also what would be the best way to psi test this system? have heard of a few ways but the inlet on this turbo is rediculous big. Also would it be possible to get the car up in the air and have some run it maybe break boost it and search for leaks that way?
 
leftynridge

leftynridge

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Aug 30, 2009
401
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dayton, ohio
Do you have replacement intake pipe for the accordin hose. If so just take the filter off and cover the end with a piece off strong plastic and clamp. Insert a hose with pressure gauge through the plastic and begin to pressurize. It will work for what you are trying to do. I did the same thing and it worked like a charm. You probably wouldn't want to try this with the car running and boost it because the noise of the engine will keep you from locating the leaks. Cause even with silence it will still be hard to locate all of them. It will take a little time depending on where the leaks are located and how many there are.
 
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89supra7mgte

New Member
Sep 20, 2009
797
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colorado
what about the air going in to intake through engine? i think i can work something out maybe just take accordion off and pressure the turbo inlet pinch off the pcv and iscv lines. just worried about the air going into the engine trhough open valves
 
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