Boost Spikes, Even After The Waste Gate Porting?!

[Gazza]

Hello xr6turbo.com members

I am reaching out for your help as I am at my wits end with my car....

First some details on my car.... it is a 03 BA and the mods that I have done to the car are;

Xforce 2.5" cat-back exhaust (no cat - I live in NZ)

HDI Intercooler kit

42lb injectors (I think that's what they are, they are green if that helps?)

K&N filter (if that counts as a mod)

Ported waste gate and bigger swing valve (and im sure this is where my issue lies)

I recently had it re tuned and it made 280kw at the wheels on 10lb.

The issue I have is that the boost seems to be uncontrollable in the sense that it spools up so quickly that the car doesn't have time to regulate the pressure and the amount of fluctuation I have (if I was to accelerate through the whole rev range) is ridiculous and extremely annoying. The strange thing is that once I got it back after being re tuned, it seemed fine. However, this issue is not since I had the tune done.

I had the vehicle re tuned by another tuner that I was not happy with about two years back and one thing I noticed was once I start driving the car hard, for an extended period of time was that the boost seemed to spool up so quickly and the car could not manage to stop the boost at the set pressure. I did not do anything with this for a long time but now its just driving me mad. I figure that is because the intake cools down a bit when you're driving on the motorway etc vs when you're driving round town the intake is hot?? Not sure....

I figured this was the standard waste gate showing its flaws so to test it I connected the turbo directly to the factory actuator and took it for a drive. What I noticed with the boost was that as the RPM increased, so did the boost pressure. By the red line it would be at ~12lb (my old tune was for ~14lb so no stress). So I asked the guy who has just re tuned my car what I should do and he advised that I didn't need to have the waste gate ported. When he told me this I was convinced that was the wrong answer, I am no car expert but I cannot see a way to tune around the boost spikes. Sometimes it would be fine and not spike (when the car is really hot) and when its cold it seemed uncontrollable. So I went against the tuners will and had the waste gate ported and had the bigger swing valve fitted. I thought that my issues would be over at this stage. So I fit the turbo back to the car with a Turbosmart actuator that I purchased (7lb I think) and take the car for a test drive. I encounter the same issue of boost increasing with RPM (this is with the turbo connected directly to the actuator still). I figured it was the actuator so another time I pulled the turbo back off the car and fitted the factory actuator again. I take the car for a drive again and I get the same problem of boost increasing with RPM. After this I figured I would connect the boost solenoid back in and see how it went (this is on the old tune). The car seemed to hold the boost pretty flat at about 12lb (I think from memory) so I figured I could take the car for a tune again.

Once I had the car re tuned by another tuner, the car felt wonderful and I was really pleased with the results. But about a month down the track now, it seems like my boost issue has come back to haunt me and I am convinced that the waste gate was not ported correctly and this is why I am posting my issue on here. The car will build up to the desired boost pressure so quickly that it goes past a little and the boost cut, cuts in and causes massive fluctuations all the way through the rev range. If it is really hot, it seems to be fine but once I start driving it round a bit and its getting good air flow through the front of the car, I am back to this issue...

Also, I feel like there is nobody around in NZ that really knows these cars inside and out which is the other reason I am asking for your input.

I know its a long post, but I am trying to give all the facts so its clearer what my issue could potentially be.

Any assistance would be greatly appreciated

Cheers

Gaz

[hawlass]

Does this happen in all gears or just the taller gears (3rd &4th)?

[Freight Train]

How long are you on the throttle for before it starts playing up?

[Gazza]

hawlass - this happens in 2nd and 3rd. I notice it more in 2nd because I am not usually travelling fast enough to use 3rd... I have used 3rd a few times and it feels the same... ie its the same issue and the magnitude of the issue is about the same...

freight train - it happens almost instantly, as soon as it builds up boost I encounter the issue. The other day I took it out, put it in second and floored it from about 2k rpm. It built up to 6lb pretty quickly, then the boost cut came in and then spooled very quickly to 12lb and the the boost cut came in again and then I stopped. It feels to me like it spools up so quickly that it cant stop at the desired pressure and 'overshoots the mark' then the boost cut comes in causing the fluctuation??

[Freight Train]

Is this with traction control off? And have you got stock inter cooler piping?

[45T-XR]

Tune related. Get your tuner to change the ramp rate on the dyno to replicate what it sees on the street and tune it properly or take him for a drive on the street and get him to touch it up, fairly common for boost levels to overshoot on the street, when its tunes in open loop boost control.

[Freight Train]

He said he bypassed the boost controller and it was the same

Edited 11/08/14 11:00 AM by Freight Train

[45T-XR]

Bypassed how? Plumbing the boost signal directly to the actuator? Or turning it off in the tune? If it is a professional shop using HP tuners to tune a falcon I'm assuming he doesnt do many?

[45T-XR]

You mentioned you have a 7lb actuator, did you test? Need to know how much preload is on the gate flapper and and at what psi the actuator os fully open. Who did the port job? Wouldnt be the first time we've seen sh*t port jobs just have the hole enlarged with a bigger flapper with know thought put into the flow characteristics of the wastegate path

[ratter]

when I got hp tuners I was told some BA's needed an aftermarket boost controller which did not make sense to me as the factory item normally works well