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The mkiv Supra Owners Club

Boost issue, no boost in first.


marc_p

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Hi Guy's, I have had an issue that is getting more and more common and now I am full BPU, it's just irritating.

 

First up, when I put my foot down in first, it doesn't boost, nothing, nadda, you just get the really deep exhaust tone and a very slow accelleration away.

 

Secondly, when I drop a gear(e.g. into 3rd at 70) it won't boost, it will never boost if you drop into a gear at 4k+.

 

Thirdly, since fitting my new Boost controller(HKS EVC-S) the boost with the first turbo seems to be rubbish, the boost reading doesn't seem to be bad(around 0.8 bar) but it definetly doesn't feel like it used to when you put your foot down on the first turbo, also, when I switch the BC off, it is still the same.

 

Fourthly, will just going TTC ease my pain of these issues?

Edited by marc_p (see edit history)
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The small VSV at the top is fooked. That's the reason you aren't getting boost when you drop a cog.

 

At least I think it's that one lol.

 

If you have a look in the technical section IanC did a great FAQ on the turbo setup and the problems that people see, oh and of course the solutions. Everything you need is in there for the first issue.

 

As for the 2nd issue I'm not sure. Why not take the solenoid out of the equation and see what happens?

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The small VSV at the top is fooked. That's the reason you aren't getting boost when you drop a cog.

 

At least I think it's that one lol.

 

If you have a look in the technical section IanC did a great FAQ on the turbo setup and the problems that people see, oh and of course the solutions. Everything you need is in there for the first issue.

 

As for the 2nd issue I'm not sure. Why not take the solenoid out of the equation and see what happens?

 

I broke the old VSV (the one on the top between the turbo's and cam cover) by accident and replaced it with a new one when I did the valve stem seals and BC, so that might be faulty?

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Your bearings might be shot, so the blades are rubbing agenst the turbo housing thus locking them upp and won´t spool.

I just fitted second hand twins becaus the ceramic bearings were shot on my Jspec.

Does your second turbo spool as usual?

TTC might get around the issues.

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Your bearings might be shot, so the blades are rubbing agenst the turbo housing thus locking them upp and won´t spool.

I just fitted second hand twins becaus the ceramic bearings were shot on my Jspec.

Does your second turbo spool as usual?

TTC might get around the issues.

 

Second turbo spools perfect, aslong as you don't drop it down a gear so the revs are at 4k plus, then it won't spool, you have to slow right down, get the revs to drop and the exhaust note to quieten down, then you can boot it.

 

I might just put it into TTC and see what happens.

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Second turbo spools perfect, aslong as you don't drop it down a gear so the revs are at 4k plus, then it won't spool, you have to slow right down, get the revs to drop and the exhaust note to quieten down, then you can boot it.

 

I might just put it into TTC and see what happens.

 

Sounds 2 me like a faulty bypasvalv. ?

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When you replaced the valve you did put the pipes back on correctly, they should overlap, seen many a car fitted incorrectly when replacing the pipes for silicon pipes etc..

 

Yup, I had a picture of 'before' that I copied(unless that was wrong aswell:blink: ), maybe I'll post up a pic of how it is now and see if it's right.

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Have the problems started since fitting the boost controller? Was the boost controller new?

 

I'd start by removing the boost controller hoses and putting the hoses back to stock. Check you have all the hoses connected up correctly and check that there are no splits in the hoses - may be worth replacing with new hose to be sure. If you only get problems when the boost controller is fitted then either it's installed wrongly or the boost controller solenoid may be faulty.

 

These threads may help.

 

http://www.mkivsupra.net/vbb/showthread.php?35924-Sequential-turbo-hoses&highlight=sequential

http://www.mkivsupra.net/vbb/showthread.php?35926-The-sequential-system&highlight=sequential

http://www.mkivsupra.net/vbb/showthread.php?27904-Sequential-turbo-problems&highlight=sequential

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Have the problems started since fitting the boost controller? Was the boost controller new?

 

I'd start by removing the boost controller hoses and putting the hoses back to stock. Check you have all the hoses connected up correctly and check that there are no splits in the hoses - may be worth replacing with new hose to be sure. If you only get problems when the boost controller is fitted then either it's installed wrongly or the boost controller solenoid may be faulty.

 

These threads may help.

 

http://www.mkivsupra.net/vbb/showthread.php?35924-Sequential-turbo-hoses&highlight=sequential

http://www.mkivsupra.net/vbb/showthread.php?35926-The-sequential-system&highlight=sequential

http://www.mkivsupra.net/vbb/showthread.php?27904-Sequential-turbo-problems&highlight=sequential

 

Thanks for them Nic, reading through, I think I have found my problem in regard to low boost from the 1st turbo, the problem appears to be that when I switch the boost controller off, the stock solenoid isn't on either(as this is disabled by blocking the pipes off when fitting the EBC) so there is no pre spool on the first turbo and the car boost lower, then when I switch the boost controller on it probably just feels slower compared to the rush of the second turbo.

 

In regard to the no boost issue, I'm going to try and find another VSV and see how I go.

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Check the 2 black pipes on intake side of turbos, the ones joined to the Y piece from air filter. One of mine had closed down inside to about 25mm (first turbo)

I changed my IACV vsv and checked the other EGBV and EGCV vsv's which were working ok according to Toyota manual.

I got boost in TTC mod but boost was still coming in too late. Changed the intake pipe and now back to normal at 1.2 bar.

Edited by markssupra (see edit history)
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I tried running high boost on the 1st turbo once years ago and the car felt very much slower. I think much past 0.6 bar on #1 = overheating the air and losing power. Someone do a back to back test :)

 

Of all the things I agree with, I will always disagree here. I had a mines ecu and a strange boost issue that meant 1.0 to 1.1 boost from the first turbo and my car was noticeably stronger than any bpu I have driven. this includes my own when running normal boost on the first.

 

The difference was unreal imo.

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