having a weird issue with my setup, car was tuned on s300 with boost by gear it ran ok for about a week. I was low on funds so a couple of months later I took the car back to the tuner because it spikes really bad, it was tuned at 13psi but spikes to 15psi and up. so my tuner turned the boost down to around 7psi(wastegate spring)and did not charge me it fixed the issue but the car feels really slow now. I have already replaced the boost Solenoid (used mac). Don't know if its related to this but the p28 ecu board was bad (reading low and high voltage) so its been replaced, all vacuum lines are new and I took apart the wastegate (hks gt 1 I think) diaphragm is worn down but no rips.



Any help would be really appreciated.... thanks

 

What manifold and what turbo. How big is the wastegate?

 

You could of also targeted a lower boost level to accomodate for the spikes unless they're huge.

 

lowering boost to 7psi means less power, so it's obviously expected the car would be slower

 

garrett gt2876r ball bearing, old school log style manifold with a 38mm hks wastegate



any little extra boost and the car spikes





I know it sucks considering all the money I put into this car

 

What are the boost reference points? Meaning? where are the vacuum lines that are coming from the wastegate going to? , Compressor housing? Intake manifold? vacuum manifold through the brake booster?

If the boost reference is too strong, (for example if side port of wastegated is hooked up to the turbo compressor outlet), that could easily be the cause of the spike (in addition to the bad circuit board and solenoid).

Any possibility of a rough sketch of your vacuum line layout?

 

 

posted the pic hope it makes sense, thanks.....

 

Double check your vacuum lines first. Then check your setting in your software normally open/ normally closed and make sure it's set up correctly. The cold weather could allow more boost pressure also. What happens if you turn down the duty cycle to the solenoid?

 

All new vacuum lines, the boost was turn down by the tuner( 7psi originally was at 13psi) and the car does not spike anymore but at a cost of a lot of horsepower. That's the reason I post this question here for some help. Thanks

 

I'm assuming you have a 7 psi spring in the gate and the tuner turned off the solenoid control and it's now running straight off the gate?

 

If I'm seeing this right, along with lsturbo33's suggestions, it would be best to run the 'yellow line' (based from your illustration), after the intercooler for the boost pressure source. It may be spiking because like some that have their boost reference source at the turbocharger (Yes, I know many turbos have it there for a reason) or a source pre-intercooler, it reference actually may be a bit too strong in which a spike would more than likely occur. Even if the boost controller is trying to regulate that reference.

The line going from the side wastegate would be a bit better at the intake manifold or vacuum source that's from a vacuum block off of the brake booster to the other end of the solenoid, and not at the turbocharger or intercooler.

This is just from what I'm seeing here at first flush.

 

My tuner switched them thats the reason its like that now, the car spikes in high boost both ways..

 

Pull the wastegate off and put some compressed air into it on the side port

cap the top and add pressure to the side. If the valve doesnt stay open then you have a leak and will most likely hear it.

(TURN DOWN THE COMPRESSOR BEFORE YOU TEST IT) dont add 70 psi thinking nothing would rip.

Ive seen leaks come from the screw holding the cap of the wastegate and from the inside that hold the valve. I usually put some honda bond on all the screw and never have spike problems.

 

Then one of the lines may also be collapsing. Turbohatchd16y7's suggestion is solid to check the wastegate itself.. Although older HKS's don't fail, checking the state of the wastegate is the next logical step.. If the valve is sticking, that also presents problems.

 

FTFY

 

My apologies, all these combined chassis/year/engine screennames can at times be confusing.

(I had no idea what FTFY meant until about 5 minutes ago...)

 

Yeah I hate it. To late to go back now..

 

Am going to try to go to my buddies shop and try this, how many psi do I have to run threw the wastegate to test it? Thanks for the help guys....

 

If its creeping at 15........... I would guess 15 psi.... 20-25 is fine too.

 

Thanks, I will try it this weekend

 

based off the photo of your manifold. (greddy with an added external wg) I've located your issue.

the Greddy manifold is divided, runners 1&4, 2&3, stay divided until the turbine flange. so by having that wastegate arm where it is you're only bleeding exhaust gas from cylinders 2&3, not all 4. that is more than likely your issue as gt28 based turbines don't need a lot of exhaust gas to make decent boost pressures. and only bleeding from 2 cylinders certainly won't give you solid boost control... and this cold weather won't help your situation at all

I suggest you ditch the external and hook the internal wg back up, you'll have much better performance and boost control.

 

and are we sure that's a real HKS gate? unless HKS is cast on the unit, then it is just a Chinese copy. and we all know what kinds of issues low quality wastegates can cause

 

It's fine. I've run that same setup for years on other cars. he's not creeping over that becuase of the runner split up, because he's not running enough exhaust energy to cause that kind of overboost issue. even the right boost controller can solve that. He's got a vacuum line and boost reference issue....

Keep what you have, and check with your boost reference source and boost controller. It may be that be that the spring is old and not allowing the ball to seat.

As for whether or not it is a "real" HKS Race gate. Only the OP can do that.

 

Its a real hks wastegate, today one of my buddies lend me another real hks wastegate to try out.. btw when I opened my wastegate to check for a diaphragm tear the spring seem to offer very little resistance. But I don't know if that's normal for a 7lb spring?