Just got back from the track once again and still can't get a clean pass due to this boost issue. Please give your input/ideas to what it could be.

Problem
car will build boost when it leaves the line but it seems like everything it gets up into rpm/boost it loses it and loses it all. If I let off of it and coast for a few then get back into it boost come back on strong but then does the same thing again. I've done boost leak tests and nothing anywhere. I've tried it on boost by gear,set boost %, and turned boost control through kpro completely off to run gate psi. No change it still does it.

Kseries on billet 6768
2 precision gates
hondata bbg on kpro

on the dyno the car doesn't act up a bit on 4th gear pulls at set duty cycles from wg spring to 30psi it's holds perfectly steady. I even made a pass at track tonight no burnout coming out of the hole like you would from a stop light then 100% throttle and as soon as it hit 16-17psi in lost it again.

My ideas that I can think of next is bad map sensor???bad wastegate(s). This whole setup has probably 20 passes on it but none of them have been full passes really

 

I dont know the answer to the question, but just out of curiosity, what kind of dyno?

 

Dynapak

 

be a bit more specific..
When you say your losing boost is it going from 16~17psi and then to 0?
Where are you watching boost from?
And are you sure it's losing boost and not something else going on?

 

Check your brake booster check valve

 

cams?? did ya check the injector seals

 

Time for a new wastegate spring?

 

Yes it's going from 16-17 psi gate psi back down to zero instantly. Off the launch it leaves strong but as soon as it gets up in boost...seems like once it reaches gate psi it drops off fast. Shift to 2nd gear quickly full throttle and there's no boost there. Datalogging all runs so I know exactly what it's doing just don't know why

 

I remeber checking the valve a long time ago for some reason but I'll check again today thanks

cams are prayoonto stg 2's. Injectors don't leak.


New wastegate spring...that was one idea I had that somehow one or both of my gates are opening at spring pressure and sticking open. That's my only thoughts how it could just lose every bit of boost so quickly with no boost leaks when I test

 

did you check your turbocharger?

 

It was a thought yes. But the turbo is almost new. Shaft/seals have little to no play. I can do dyno pull after dyno pull and the turbo spools great and pulls hard with no fluctuations at all every time.

I've almost norrowed it down to a wastegate problem. Even if one of my two gates went bad the air is going to take the path of least resistance. Anyone ever had a problem with there gate sticking open? It does seem as when I launch and it reaches the gate psi to open it stays stuck open

 

it is very possible that it is ur wastegate....force air from the side and on top and see what happens if it leaks or not, maybe the diaphram is no good

 

I had a similar issue and it was my gm 3 bar had a bad connection. But it wouldnt go from 20psi to zero instantly. It would sputter

 

my buddy had a similar problem. went through everything 10x. turned out it was a hole on a 90deg elbow....we couldnt see the hole cause it was resting against the bumper... it would build(15 psi) boost then lose it all in a flash...over and over again. only found it cause he took off in frustration and i heard the gush of air coming from the front of the car as it hit boost...

 

You saying one on top gate and one on bottom at the same time. I just opened the gates up and the diaphram looks new. I've also done boost leak test and found nothing.

 

Where was the 90 fitting going? To the gate?

 

i wonder if under acceleration the motor movement is causing an intercooler pipe to move and lose its seal. What are you using for coupling the piping? Only thing i can think of that would be hard to emulate on the dyno.

 

Are you useing some kind of v band or other parts in the intercooler set up. I have seen a v band clamp get really old and the car on the leave would lose boost. It was a old clamp that come off a big truck. Would not do it on the dyno but would do it a track.

 

I thought the same thing John which makes perfect sense but it's got solid mounts now vband off the comp housing and a coupler on the Intercooler side. I've checked that out too. Usually when a boost leak like that happens you can hear the whoosh of air and I've never heard it once. I've ruled that out. It's just weird that it will lose it at the line then build again once I let out for a bit

 

17psi to 0 is pretty drastic. I've only seem that when one of the turbo wheels hits the housing. If a gate was wide open it would still make some boost. Very interesting.

Maybe its a duty cycle thing. The load on the dyno is not the same as on the track. Try running it without the boost soleniod; once with a boost source on just the bottom port and then just the top port. See if that changes it.

Are you logging emap?

 

Yeah Andy I log all of my passes. I agree 17psi-0 is drastic I can email you the log if you want. i've never seen anything like that especially without a boost leak. It's hard to explain especially when it happens because it's never really consistant to a certain rpm or gear.

I did what you said and tried running it with boost by gear, changing to set duty cycle, then turning boost control completely off and it made no change. I left all the vac/boost lines hooked up though. should i pull the solenoid/top gate lines off to just run the bottom? I'll also try to post up a drawing later of how I got the source lines running for everything which that shouldn' be an issue but someone may see something i don't. it's just getting frustrating I can't figure it out I think I've been overthinking everything to be honest

 

Pressure test the system?

 

yes numerous times. Nothing leaking at all. no couplers have moved at all i've marked everything to see if anything is moving even a tiny bit and it's not. If anyone wants to look at a log let me know it's weird for sure.

took the gates off and apart a little bit ago and everything looks great inside the gate. diaphram looks like new etc. only thing I noticed was a some black around the edges of the gates where a small amount of exhaust came around the edge. If that was the case and it was leaking around there wouldn't it just cause the turbo to spool slower and not lose the boost?

 

Do this, take off your vaccum line (infinite boost) and set your boost cut at xx psi at the track. If the problem still occurs, inspect the turbocharger. I have a really good feeling it's the turbo it self. I might be wrong but hey I did see few turbos did that out of no where.

 

What year car? Drive by wire throttle?