Mike1982

Yea, with a stock turbo you should get your max boost much sooner then 4.4k or am I wrong? Looks like you see 12psi at 3.2k, isn't the stock turbo suppose to be up full by 2.8k in a stock car?

NZ951

Danno not a day or two ago said he can get boost holding in all gears at 18psi (IIRC). Even if the spool is later, it should still hold, unless something is wrong or it is not setup correctly I guess. Something to look into anyway.

Danno

The higher-boost levels take longer to build. You'll notice that 15psi hits at 3500rpm which is correct for a K26/8 TurboS. Then 18psi takes a while longer. This is similar to what Jason in WA experienced with his turbo and wastegate upgrades. Using the GURU then the Tial wastegate yielded the same boost-curve; similar to the one above. I suspect this is partly a turbo issue and partly a mechanical control one. Most people can't see the actual boost-drop on the mechanical gauges, it really shows up when you datalog the manifold-pressure. With an RPM-programmable elecronic boost-controller, you can vary the duty-cycle with RPM to generate a flat-boost curve overall. Like with the AVC-R or the EBC upgrade to the MAP-computer.

I also think it's a turbo issue because our GURU-364 beta-tester with the exact same configuration (GURU MAP-2, larger-injectors, Reliaboost, GURU wastegate), ends up with a dyno-chart like this at 18psi:

You can still see the kink when 15psi boost hits at 3500rpm and is caught by the boost-controller (18psi develops about 700rpms later). And the torque-peak occurs 1000rpm later with the effect of stretching it out over a wider powerband. Over 90% of the peak-torque is available from 3400-6300rpm. In fact, by redline, its only lost 12% of the peak-torque number. Maximum-HP is made right at redline, a sign of good high-RPM breathing.

I think we can replicate this type of a torque-curve with the stock K26/6 and K26/8 turbos, but we'll need to use an electronic boost-controller to get a flat boost-curve. That's the only way I've been able to get the stock turbos to hold 18psi max-boost in all gears and all RPMs.

NZ951

I know you can adjust boost levels by 500rpm in the link, but how does that make for a flat curve?

tazman

With the AVC-R I reach 18psi before 4500rpm. The pic below shows my boost curve in third gear and I have not done anything with the AVC-R yet except let it learn the duty cycle. I am pretty sure once I mess with it I will see 18psi by 3500rpm. But it's still not enough I just got my a$$ whopped by a Mustang Cobra

toddk911

"But it's still not enough I just got my a$$ whopped by a Mustang Cobra "

That would have to have been a brand new CObra with the super charger making 400+ hp.

I have the GURU wastegate with an aftermarket turbo and it makes and holds 18psi no problem and holds to redline. It is his stock turbo running out of steam. As Danno said, when compared, the GURU wastegate is just as good as a Tial, just a whole lot cheaper.

"I know you can adjust boost levels by 500rpm in the link, but how does that make for a flat curve?"

Not the Link, an electronic boost controler will give a flatter boost curve compared to a manual boost controler.

NZ951

Todd, the link controls the EBC... its just a venting solenoid hard wired to the link.

tazman

Look at my post again I don't think my stock turbo is running out of steam. I can tell you last time I looked at the AVC-R's duty cycle it is running 55% around 3500rpm and 86% around 6000rpm.

NZ951

Just a note, even if it isnt running out of steam, how far out of its efficiency zone does someone want to run? I would have thought not much without some other significant mods to cool the charge down.

Jake951

I've found from previous dyno runs that it's better to run a little lean (like 13:1 to 13.5:1) in the boost rampup phase because it makes more power there. I think Danno has said the same thing. Once into full boost, 12.5:1 to 12:1 makes maximum power. I run 12:1 to be safe.

The exhaust probe was inserted directly into the tail pipe.

toddk911

"I can tell you last time I looked at the AVC-R's duty cycle it is running 55% around 3500rpm and 86% around 6000rpm."

Duty cycle of your injectors??

Jake951

The off-idle stumble is reduced from the earlier chips. I can provoke it if I really try hard, but normally I don't notice it all. While cruising there is still a bit of an abrupt transition from off-throttle to on-throttle if you are riding the throttle very lightly, but once the throttle is open, it runs smoothly without any stumbles all the way to redline.

No, the flapper box (stock AFM if that's what you mean) is gone completely and replaced with a cone filter, just like in the pictures on the Guru Web site.

I'm running 93 octane (street gas).

Jake951

The CV is bypassed so that should not be a factor.

Jake951

I'm wondering if the factory catalytic converter is a factor here in causing the boost rolloff on the high end. Thoughts, anyone?

tazman

No the duty cycle for the solenoid that lets pressure to the waste gate to open it.

John sorry to highjack your thread here! Since you bypassed the CV the only other thing I could think of that would make the waste gate open would be exhaust pressure caused by a clogged cat. Maybe Danno will have some other things you can check??