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Discussion Starter · #1 ·
wehats up..recently i have been having some trouble boosting properly with my stock twins...i am just bpu 6 spd....anyway my friend had the tool to stick in the intake piping and fill the system with compressed air to check for vacuum leaks and things like that...

now we didnt cap off anything like pcv hoses or anything...we jst simply pressurized the system to listen for leaks which we found some and repaired but strill i wasnt sure what else i should hear...basically i am pretty sure i have a problem with my pressure tank becasue my sequential operation is a little screwy still...and do not tell me to go TTC becasue that is a waste of time and i hate it...car literally feels liek shit..and my turbos are very healthy...anyway..once we fixed the leaks that we heard by the turbos we pressurized it again with about 6 to 7 psi of compressed air...basically my question is..where if any would i hear air escaping that is normal...i was pretty sure that since we didnt clamp down any pcv hoses or anything that there would be some air escaping./..i took off the oil cap and it released some pressure...also i heard some air coming from the rear part of the engine closer to the intake manifold...i could not pinpoint this..i was thinkin this was either normal or the pressure tank which i have no clue on how to get at...i had the car on the lift and could barely touch the thing..what is the best way to get this...

ok sorry for the dcomplicated post ..any questions ask...

to put it in simple terms...where should i hear air coming out of if any when i pressurize my system??

thanx
anthony
i searched also
 

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TTC may feel like shit but it is an excellent temporary diagnostic tool. If you perform the TTC mod without check valves and your stock twins are not boosting properly then you have a problem with your EGCV, IACV, or presure tank. Next, If you go ahead and perform TTC with the check valves and the stock twins suddenly begin to function properly then it is clearly a problem with your pressure tank.
 

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Discussion Starter · #4 ·
all we did to pressurize the system was take the intake filter off and put the circular tool in it with the buage attached to it and used a regular air hose to pressurize the system to about 7 psi ..thats it...we didnt cap off anything..we wanted to see if i had any vacuum leaks and found nothing on the turbo side of the engine..i heard hissing from the intake manifold side near the back of the engine...couldnt pionpoint where it was coiming from..this is the area of the pressure tank but i cannot get even close to uit...i even put the car on the lift and went from underneath anmd could barely feel the tank..i felt hoses and they seemeed connected but thats not good enouhg for me since i copuodnt even see the damn thing...

my problem is i get no boost right around 2900 -3500 rpms...like rioght where the second turbo is supposed to prespool and come online it seems like it doenst do that..

what happeneds is i will floor it from about 2k rpms..the 1st turbo will boost strong and normal and fast to about 10 psi..then just when the sequential system gets that normal drop in boost about 2 or 3 psi when the change opver happends about 2900-3000 rpms it drops alot of boost like to maybe 4 psi and then it will climb back up to full boost..my turboes are strong and they dont smoke at all...plus if i want to i can set my BC to well over 20 psi and i will reach that easily..so i ruled out blown turboes right off the bat...its very hard for me to explain whats happeneding unless you come for a ride with me and watch my bost guage and listen to my car...its almost like the car goes into ttc mode automatically at like 2900 rpms or so...my exhaust note even changes at that rpm...this happeneds in every gear its just way more noticeable in the higher gears...also if im crusing on the highway in 6th gear and i am at say 2500 rpms..i can floor it and the first turbo will spool to like 10 psi and then once i hit that certain rpms the exhaust note changes and the boost drops and rises gradually...when this happends once the rpms get a little higher like above 4k the turboes spool normal...this is really pissing me off but the best explanation i can give is that my second turbo doesnt get prespooled enough or something...ok hope this helps alittle bit..please help this has been happeneing for a while and it sucks...this all hbappened one day out of the blue..my car ran fine..then i took it for a ride one day went aorund the corner..was in second gear..pressed the gas the first turbo spooled then i heard liek a thud noise and the enxhaist note changed and it sounded like a vacuum line popped off and it has been this way ever since...it doesnt really hurt the performance casue if i need too i just make sure when i downshift that my rpms are over 4k and i can get normal boost from both turbos...


ok please help..this is confusing me ..i cant imagine what this looks like to the peopel reading this...

thanx
anthony
 

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You are either having a problem with your pressure tank, IACV, IACV VSV, or the vacuum hoses leading to any of the aforementioned. Leaks in any of these would cause exactly the problem which you are experiencing. I would check the hoses first, as this is the most likely culprit and easiest to replace.
 

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Anthony,
So boost drops at 3k rpms and starts back up at 4k correct?

If this is true I know EXACTLY what your problem is.
 

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correct me if i'm wrong - but from my understanding you shouldn't be pressurizing your "intake system" by removing the air filter and pressurizing from there - you should place the pcv/hose whatever yer using to pressurize, over the intercooler piping that connects to the Y outlet for the twin setup. this test's your intercooler and piping up to the TB for air leaks.

I've also read that going temporary TTC mode will help in diagnosing other potential problems, such as the pressure tank, iavc, egvc - just as Crossways was saying.

hope you get the problem fixed out, man. and keep us updated on the fix!!

-jim
 

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If you were hearing leaking from the back of the intake manifold, you may have a leaky EGR. (If you haven't already done so) Get some block off plates or just make your own out of sheet metal along with doing the regular EGR mod. (cap hose and resistor)
 

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so normally you would be getting the second turbo coming online at 3k rpms and hitting full boost? Isnt that well too soon?
 

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IcedSuPrA said:
and do not tell me to go TTC becasue that is a waste of time and i hate it...car literally feels liek shit..
You are never going to want to go single turbo.

Pressure tank is a likely culprit, or the IACV. Also check the vacuum hoses to make sure they haven't cracked or poped off. Also, the best way to check for leaks is to do a section at a time. Trying to pressurize the whole system makes it hard to pinpoint a leak. I would also cap off the PVC line, since that usually won't seal completely as it is usually seeing a vacuum even when under boost.
 

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IcedSuPrA said:
what happeneds is i will floor it from about 2k rpms..the 1st turbo will boost strong and normal and fast to about 10 psi..then just when the sequential system gets that normal drop in boost about 2 or 3 psi when the change opver happends about 2900-3000 rpms it drops alot of boost like to maybe 4 psi and then it will climb back up to full boost..my turboes are strong and they dont smoke at all...plus if i want to i can set my BC to well over 20 psi and i will reach that easily..so i ruled out blown turboes right off the bat...its very hard for me to explain whats happeneding unless you come for a ride with me and watch my bost guage and listen to my car...its almost like the car goes into ttc mode automatically at like 2900 rpms or so...my exhaust note even changes at that rpm...this happeneds in every gear its just way more noticeable in the higher gears...also if im crusing on the highway in 6th gear and i am at say 2500 rpms..i can floor it and the first turbo will spool to like 10 psi and then once i hit that certain rpms the exhaust note changes and the boost drops and rises gradually...when this happends once the rpms get a little higher like above 4k the turboes spool normal...this is really pissing me off but the best explanation i can give is that my second turbo doesnt get prespooled enough or something...ok hope this helps alittle bit..please help this has been happeneing for a while and it sucks...this all hbappened one day out of the blue..my car ran fine..then i took it for a ride one day went aorund the corner..was in second gear..pressed the gas the first turbo spooled then i heard liek a thud noise and the enxhaist note changed and it sounded like a vacuum line popped off and it has been this way ever since...it doesnt really hurt the performance casue if i need too i just make sure when i downshift that my rpms are over 4k and i can get normal boost from both turbos...

i'm not very familiar with PSI #, but what you describe is actually the behaviour of a BPU supra, you can check some dyno charts of bpu cars and compare them to what you feel. On mine pressure drop starts at ~3400rpm and i hit (my) full boost (1.1bar) somewhere over 4000rpm.
 

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You should try and find someone with a "bong" aka "smoke machine" this way you can see exactly where the leaks are.

jeff
 

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Discussion Starter · #13 ·
cwtt said:
Anthony,
So boost drops at 3k rpms and starts back up at 4k correct?

If this is true I know EXACTLY what your problem is.
yess this is exactly whats going on with my car.....since it might be the pressure tank can someone show me the easiest way to get at it to check the hoses..also can someone posty a pic ora good diagram of the other hoses that i should check for vac leaks..all the ones on the turbo siude of the engine i checked and rechekced over and over again and they are good...i just dont know where to start with the vac lines on the intake side of the engine like the pressure tank and the egr hoses...i also plan on getting the egr plates and doing the mod casue toi me the egr system doesnt seem to casue anything more then bad things...

cosmic chaos..i know exactly what your talkin about..i know about the normal drop but this is more..my cars system worked perfectly until out of the blue this happend...it had the normal drop about 2 or 3 psi but this is alot more and lasts for a lot longer ..it drops around 5 or 6 psi then builds back normal after 4k...

and 97 twin turbo....you are right..i really dont have any plans for the future to go single...i love the reliability of a bpu car and honestly its fast enough...ive seen bpu++ cars on race fuel put a few cars on some singles on pump gas...plus there isnt much more a car can do ont he street with over 500rwhp...my goals are around 450 rwhp with twins if possible and if they blow ill just put another set on..but thats a different story...

i n eed to fix my prob..i cant wait to hav my ride back to normal again

thanx
anthony
 

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cosmic chaos..i know exactly what your talkin about..i know about the normal drop but this is more..my cars system worked perfectly until out of the blue this happend...it had the normal drop about 2 or 3 psi but this is alot more and lasts for a lot longer ..it drops around 5 or 6 psi then builds back normal after 4k...

i n eed to fix my prob..i cant wait to hav my ride back to normal again

thanx
anthony[/QUOTE]


This is EXACTLY what is going on with mine right now so Ill be following this closely. Yes, there is supposed to be a boost dip. However, mine (and I think ice's) will dip, then get a quick secondary dip to about 4psi or so, and then start building to peak boost after 4k rpms. My culprit might be the iacv vsv, when I bought the car that little filter that goes on it was missing. Not sure if that would affect anything but I will replace the vsv, I tested it and it works though :-( Also, when people say the pressure tank is the culprit, do they mean it is BAD or leaky? After driving if I pop the hose off the vsv's I can hear a whoosh.
 

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Discussion Starter · #16 ·
yeah can someone else chime in here...also can someone post up or send me some good diagrams of these parts i am supposed to check..i am kind of new to the supra turbo setup so these valves and stuff sometimes confuse me..

thanx
anthony
 

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Discussion Starter · #18 ·
im in central nj....

monmouth county....

i did the test with a freind who is a good mechanic but he really doesnt know much about supras..hes got fully built 300zx tt.i think it makes close to 600rwhp and now he wants a supra since he drove mine..anyway thats a different story...

he doesnt know much about supras turbo setup so he couldnt help me much...maybe u could meet up with me and help diagnose this extremely annoying problem'


anthony

also i followed the diagram and its all good as far as i can see but the pressure tank is the only th9ing that i have not been able to fully check..i cant even get near the freakin thing even from under the car on a lift...


thanx
 

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do you know how to test the vsv's? test those and make sure they work, it tells you how to test them on mkiv.com, make sure they are working, its pretty simple and would probably cause your problem if one or more of them were not functioning properly.
 

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rte. 17 said:
correct me if i'm wrong - but from my understanding you shouldn't be pressurizing your "intake system" by removing the air filter and pressurizing from there - you should place the pcv/hose whatever yer using to pressurize, over the intercooler piping that connects to the Y outlet for the twin setup. this test's your intercooler and piping up to the TB for air leaks.

I've also read that going temporary TTC mode will help in diagnosing other potential problems, such as the pressure tank, iavc, egvc - just as Crossways was saying.

hope you get the problem fixed out, man. and keep us updated on the fix!!

-jim
Do you have a pic of this method? I need to check the turbo side for leaks before I dyno next week.

Jason
 
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