Van

I was racing this last weekend at NJMP Thunderbolt, and on Sunday, my car developed a problem. After a few laps on the track, boost would fall off as RPM's build.

First, a little about my setup - it's stock chips, stock AFM, stock cycling valve, and a Lindsey Club-gate. I do have a Lindsey boost enhancer on it.

Normally, on the stock boost gauge, it beautifully builds boost to almost 2 bar, and then it drops down to about 1.75 bar all the way to red line.

But, what's started happening is, again, this happened after the first few laps of the session (happened in 2 sessions), the boost would spike up to 2 bar (like normal), but then it would steadily drop off (as the RPMs climb) to 1.2 bar. Which, let me tell you, feels like driving an NA (no offense to NA drivers. ).

As soon as I change gears, boost goes back up to 2 bar, but then smoothly drops down to 1.2 bar.

Some things to note:

• There is no ignition or fuel cutout (like a safe mode) - just a smooth decrease of boost
• It's not the cycling valve (I put in a new one and the same thing happened)
• The wastegate is 2 years old
• The wastegate line and diaphragm holds vacuum (from a hand pump - so there are no tears)
• It's not the BOV - that tests good
• It was running well prior to this condition

Has anyone had a similar situation? I'm hoping to do some testing on Friday to: a) try and replicate the problem; and b) try to diagnose what's causing it.

My thoughts are, either the charge pressure is leaking out of the intake, or the wastegate is being actuated (or stuck?) which is reducing charge pressure.

xupkid2

Hey Van

I had a similar situation last year at Road America. It ended up being my 2 pc crossover leaking as well as my headers being cracked. Not sure if that is your problem but might be worth checking. Hope it helps

fast951

Van, I would start by checking vacuum/pressure leaks in the intake. Check the BOV.

Next I would look at the exhaust, a leaky header or X-over pipe will hurt it. Also, a collapsed X-over pipe or Downpipe will do the same. Of course a malfunctioning WG is another possibility.

If you have a second well known KLR (box & chip), I would try it as well. Might be the easiest to try.

jasonlp

I had similar problem-ish for me it was rubber boot at the IC cracked.

Van

Great ideas, guys. Thank you.

MM951

If you want on friday we can swap some parts or I can bring a spare set of headers/cross over if you want em

Van

Awesome! Please bring them - they're one of the few spare parts I don't have.

reno808

i have a cross over and down pipe that are good. let me know

Willard Bridgham 3

+1 on the KLR.....got a known good?

MM951

Ok, I'll bring em. I also have a spare Dme/klr I can bring if needed?

ehall

Van, wasn't like 800 degrees there last weekend? You sure the IC didn't just get heat sinced?

Van

Oh, the heat played a roll... it was hotter than a half fu**ed fox in a forest fire on Saturday, and the RS America in my class would pull on me in every straight. But, on Sunday, it was totally different. The boost gauge was reading low and the power I had Saturday really wasn't there.

Mike, bring the computers along - they'll be good to have on hand in case we run out of ideas.

TurboTommy

On hot days, the underhood temps can play havoc with some of the electrical components.
A tired old TPS (or frequently exposed to high heat) won't give the KLR the proper full throttle signal, which then the cycling valve/ wastegate combo will only allow the minimum limp mode boost which is exactly the 1.2 bar absolute pressure which you described.
This is what happened to me once.