Completely stumped with Boost creep problem, what else can it be????

[antnicuk]

I have now come to the end of my teather with this boost creep problem.

Since i fitted the new turbo (GT35/40) i have been unable to control the boost.

I initially had a small manifold and it was thought that might be causing the problem, so i changed it to a nice new HKS cast manifold.  No difference whatsoever.!!! :xconfused

It was then thought it may be the cheap XS power wastegate which is a copy of the HKS 50mm racing wastegate.....  I checked it thoroughly and was doubtful weather it opened enough.  Gord from Jap scene was kind enough to lend me another wastegate which was the same as mine and didnt seem to open that much either but i stuck it on and tried it but again no difference :reallymad

Memski was then kind enough to lend me his Original HKS 50 mm Racing w/g, which i had a look at and the piston does seem to open more than the XS Power one by about 1/4 of inch.   I put it on and it didnt make any difference!!! :reallymad  :reallymad

I have also changed the feed pipes to the w/g, disconnected the boost controller,  run it without plumbing in the exit of the w/g to the exhaust.

The turbo has been run on an rx7 (Eds car) with the same wastegate and no problems, the exhaust is 3inch all the way until it splits into 2  2 1/2 inch rear boxes.  It wont run less that 1.1 bar in the higher gears.   I cant even stick the boost controller on it to run that boost all the time cos when i increase the boost with the contoller to try and get to reach the maximum boost and hold it it just goes even higher.

I really dont know what else to try anymore and am getting thoroughly p***ed off !

Now would be the time to make me offers for all the new parts, (ecu,  NOS, Turbo, manifold, W/Inj, clutch, brakes, engine, etc)!!!!! before i set fire to the bl00dy thing!!!!!! :flamed  :flamed

Any help or ideas would greatly appreciated.

Regards
Tony

[Timrxmotors]

Make the pipe to the wastegate 50mm,and if your manifold is divided,have 2 50mm pipes spliced together at the wastegate,then it will work.
If not,I\'ll bid £50 on the turbo.

[bnaellis]

Make the pipe to the wastegate 50mm,and if your manifold is divided,have 2 50mm pipes spliced together at the wastegate,then it will work.
If not,I\'ll bid £50 on the turbo.

Do as Tim has mentioned above if not I\'ll bid £60

[nikp]

I\'ll go for £70! :p

[antnicuk]

Cheers for the response

the w/g is bolted directly to the manifold and the hole is 50mm in the manifold.  The manifold is the stock HKS FD cast one,  so its divided but the turbo isnt.  The branch off for the w/g is all moulded from the outside.  so its not just as simple as cutting of the pipe that goes to the w/g and putting one from each runner.  i was contemplating making a Y piece from the stock manifold w/gate flange and running two wastegates but they will still be fed from the stock wastegate hole in the m/fold so not sure if it will work.

As for the turbo,  its done 200 miles since it was rebuilt and has all the goodies so a bit more than 70 quid. Its the TO4 f/print FYI.  

This m/fold comes with the TO4 R kits etc so should work, my exhaust ports arnt that big!

[cjr]

Alright £80. watched a hks wastegate open today whilst putting onto car and it open right up. I don\'t mean 1 inch move I mean it went as far back as it could!
Make a thin metal plate up with a smaller hole than the exhaust bore put it in the exhaust system and see if you get boost control! trust me I have thought about this for a while. This way you can see if restricting the exhaust helps. Try it and call

[antnicuk]

Alright £80. watched a hks wastegate open today whilst putting onto car and it open right up. I don\'t mean 1 inch move I mean it went as far back as it could!
Make a thin metal plate up with a smaller hole than the exhaust bore put it in the exhaust system and see if you get boost control! trust me I have thought about this for a while. This way you can see if restricting the exhaust helps. Try it and call

I checked the wastegate before i fitted it,  the piston goes all the way up when i stick air into it.

I try blocking one of the rear silencers to see if that makes any difference
cheers
Tony

[strange_days_uk]

I cant even stick the boost controller on it to run that boost all the time cos when i increase the boost with the contoller to try and get to reach the maximum boost and hold it it just goes even higher.

What boost controller are you using ?  If ball and spring, is the spring getting stuck open somehow ? Is it on the right way around ?  Real noob questions I know but you never know.
If Electronic, is it broken somehow?  Try removing the boost controller and check what base boost level is., see if you still get the creep.

Simon..

[antnicuk]

I have disconnected the boost controller as i just want the boost stable on the waste gate.

[BlitzBoy]

You dont think maybe you might have too small a hotside A/R? what size A/R is it?
What size Spring are you using in the wastegate?
HAve you got the signal vacumm hoses on the right way round to the wastegate?

Or you could try taking the wastegate spring out completely from the wastegate and see what happens

[antnicuk]

You dont think maybe you might have too small a hotside A/R? what size A/R is it?
What size Spring are you using in the wastegate?
HAve you got the signal vacumm hoses on the right way round to the wastegate?

Or you could try taking the wastegate spring out completely from the wastegate and see what happens

The hot side is 0.96,  the turbo was used on Ed\'s car and performed well.  

I have put a really week spring, its about 0.4 bar

The hose comes straight from the turbo outlet to the w/g inlet under the diaphram and i have left the top one at the moment.

I have taken the dump pipe off, that goes back into the down pipe and it has made a bit of difference,  i think the turbo creates boost so easily that i need to bypass as much gas as possible round the turbine and the pressure in the down pipe is to great to allow the gasses coming out of the wastegate to get back into the exhaust (shame, i much prefer having the wastegate plumbed back in to the exhaust) .  I can now hold 0.8 bar with the boost controller,  

now all i need is an original HKS 50 MM wastegate or bigger,  anyone?

[royston1xx]

Put a 10psi spring in the wastegate. To run 0.4 bar you are diverting a lot more exhaust gas through the gate than you would be at higher boost pressures. Also you should only run up to around 1.3 times the spring rate or you will get other control issues. What boost range do you want to run?

[antnicuk]

i had a 0.8 spring in it to start with and then put the lower one in tosee if it helped.

If i get it sorted i will go back to the 0.8 spring as i want to run 0.9 low boost and 1.2 high boost

The problem is that because is already higher when the w/g opens, the boost ends up higher at the end of the revs.   If it opens sooner it starts climbing from a lower boost level, the low the point that it opens the lower it reaches at final boost..

[cjr]

I have seen t51 engined car reduced to .5 bar boost by restrictor plates at full throttle. Give it a try! you have tried everything else. At least this if it works shows up a prob.

[Gord.R]

Ah Dear..still not sorted...sounding as bad as my Supra lol...

IS there much else ypu can try!!... I know you say you had the E.B.C disconnected... take it this means you had the port venting so to speak and were reliant on the wastegate spring?

Hope you get it sorted soon...if you need a hand with any bits..give me a shout..

Cheers

Gord