As soon as I get a damn serial to usb adapter, or on old *** laptop (can anyone help with either?) I'll get some datalogs!
~Eyal

 

Turbo Tommy: The factory wastegate is not bad, it just wasn't designed to hold boost to redline. As a matter of fact, almost all turbocharged cars have this set-up (wastegate not holding boost to redline).

Heck i know several people who shimmed the stock wastegate to hold boost to redline, as much as 20.5psi as well, and datalogged. The issue of dual port wastegate vs single port is another discussion though........

 

should i shim the guru wg?
~Eyal

 

From 12-18 yes, it will make more HP. Once you are at about 15-16 it will only make more tq.
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NZ,
to answer your question; yes, I have run both boost levels with k26/6. That's why I'm able to state this observation, which also led me to dig deeper into the physics of turbochargers.
This was like ten years ago; there's still so much bull$#%t flying around!
Don't get me wrong; you can always squeeze out the last ounce of hp by upping boost with a k26/6, but one shouldn't think that just because you can hold higher boost to redline that doesn't mean you now have that much faster of a car.

So Matt H, yeah, of course you will have more torque with the higher boost. But only in the mid RPMs where the turbo can still pump with reasonable efficiency. This discussion is about high boost to redline, and no, there you will not have more torque (or very little increase) at 18 psi boost.

 

Tommy, I concur. However, I thought I read you say the car wont be faster which is false. If you are saying the car wont be faster after 5K RPMs then again, I would agree.
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Thats what I was thinking as well Matt... I am perhaps a little confused as to the point Thomas is making. I certainly went a lot faster at 18psi and with my tial than stock when I had a K26/6.

 

Yeah, guys; wasn't this a discussion about "boost to redline"
"Why is boost dropping off" was the question and "what can we do about"
There's lots of talk that it's the wastegate and I'm saying it's not.

Yes, of course, if you run more boost in general your area under the curve will be a bit fatter, therefore your car will be a bit faster.
But someone with a bigger turbo and still the stock wastegate will easily pass you as the RPMs creep up even if he's only running 14 psi boost to redline.

 

I drop to 11ish psi in 3rd.

 

another issue I noticed, especially today, is that sometime it isnt quite as quick as others. Like today, it was not quick, not slow, but not quick. Tonight, it was much quicker, almost impressive for a K26. still lots of boost drop off, and both times its seeing the same amount of boost (from my limited view time of the display) could the TPS be bad? something? its more then just temperature changes. something is robbing me of a good 15-20 horses everyonce and a while.
Further, I often get a slight hesitation while building boost. Very noticeablle when the engine is still cold, but pretty slight when warm. any ideas?
~Eyal

 

Eyal, tonight = cooler and more dense air = faster than day time where its less dense and warmer. You know that extra kick you get on cold days, water injection!!!

 

Andrew, I thought of that, but it was too much of a difference. Besides, there was a varience during the day too. Seems almost like the DME is retarding timing a bit or something.
~Eyal

 

I've got Vitesse chips with a Tial 38mm wastegate, and a Lindsey manual boost controller... I'm having similar occurances, where boost goes up to 15psi (what i'm aiming for) but then quickly drops back by a few psi (maybe down to 11 or so) and also I have a similar problem where some times it doesn't feel as quick as others. Since i've upgraded both the chips and the wastegate, doesn't that suggest that it probably isn't the wastegate itself and is maybe the boost controller?

-Jeff

 

Would a cracked exhaust header or crossover cause a drop off in boost?

 

Yes and no. A big enough turbo can over come leaks. But will loose efficiency.