Kyle Donley

A poll to help settle a dispute in this thread: '86 Turbo Dyno ...again

Hopefully we will hear from some people who have some credibility and that most of us trust to give us accurate information. I find that a lot of the information flying around on Rennlist lately is flawed or provided by people who know nothing about these cars. And most of all maybe we can help the guy out who posted the original thread and is running way too rich in the midrange.

If you haven't read the thread here is the synopsis:

Hey I'm running rich. Here are my dyno sheets. Help please.
Your boost is trailing off at the redline, I can hold 16psi at redline. You have a boost leak.
You can hold 15psi? I can't
Neither can I.
I'm sweet too, I can hold 15psi all the way.
I don't think it's possible to hold 15psi with a k26/6.
It is possible and me and all my friends do. If you can't your car is broken.
I really don't think that it is possible, why would Porsche put a k26/8 in the Turbo S cars if the k26/6 could.
I can't hold 15psi at the redline.
You're an idot you don't know what you're talking about.
POLL

Kyle Donley

Please feel free to elaborate on your vote, a simple yes or no is not likely to win anyone over.

special tool

is there an arguement about this??

Of course a k26/6 can hold 15 psi to redline - I have done it many times.
The k26/6 is starting to be off its map, however at 15 and a little higher- so you really don't want to run it much higher.

You will have a hard time doing it with the factory wastegate, however.
The factory wastegate is a safety valve, not a real wastegate.
You won't find any other wastegates that open OUT to relieve pressure.
This was done in conjunction with the k26 (which makes HUGE backpressure) as a fail-safe measure.

If you put a real wastegate like a Tial on the car, you can make 30 psi to redline- I have by mistake when an AN line came unscrewed and numerous other times above 20 psi on the dyno looking for more power - there was none.

Jeremy Himsel

Well, I can't speak for anyone else, but I have (had) 3 26/6 cars that could not hold 15psi until redline. Two of them were a shimmed factory WG (junk if you ask me), and the second was a TIAL.

The one with a tial is the Vitesse 26/6 AFM chips dyno chart and it dropped to about 13.5 by redline. It was a fresh motor and turbo and there were no air leaks. Yes, I used a real gauge.

special tool

What spring on the Tial, Jeremy?

Keithr726

I believe they can only with a LR or tial wastegate. Lets see what poorrsshh951 has to say because hes the one that dynoed 301rwhp with a k26/6.

Jeremy Himsel

.8 bar. First with a black **** MBC and then with a Profec B. Both run in dual port. I can get them to overboost below 5K but in the 5.5K range they've always dropped off for me.

Techno Duck

At 15-16psi, what should a K26/6 be able to put out in terms of horsepower? Assuming decent chips and a 3-inch exhaust?

95ONE

Mine Did not. WIth a stock wastegate, A 38mm Delta gate, or a 44mm. Tial. I have many dyno runs Staring at the Boost gauge in 4th gear.

I ran 12, 15, 18 psi. All attempts dropped boost to 12-13psi by redline. still making power in the 255-270RWHP range. (Depending on intercooler)

'86 with 165K miles.

gt37vgt

I set up the boost enhancer and waste gate on the bench at about 15 psi my car hits 19 to 22 psi at 3800 then hovers around 17 psi this works ok but i'm sure to be risking lean out i think around 300 atw is the best this would be 19 psi at redline and every other bolt on and maybe water injection .
I let mine over boost as 20psi at 4000 rpm would be close to max flow of the turbo and max flow of a standard fuel system i then don't mind it falling of to 16 17 psi as i dont think all the gear is up to it

JE_951

I have tial 38, black ****, B&B exhaust, MAF, MAfturburner and hit 15psi daily in 4th (dunno bout 5th), and have hit up to 16.5 at redline in 4th gear. Both dyno guage and my boost guage on car were dead even.

Dont know why I was "able" to but those are hard facts that its possible. Once my engine is back in the car I will be glad to prove it...

175k original miles, no refreshing.

JE_951

and to add...

This is a poll for holding 15psi to redline WITH WASTEGATE, AND BOOST CONTROLLER!!!
Not a stock car with chips and boost controller..

If I am wrong about this then I will agree that a stock car with exception to boost controller will NOT hit 15psi.

sawood12

I failed to hold 15psi for much more than 1000 revs. The boost pressure peaked at about 3.5k rpm and held it for maybe just under 1krpm then steadily blead off as the revs increased to about 10 or 11 psi at 6500 rpm. I have an LR DPW wastegate and a black **** MBC (I know the black **** MBC can also bleed boost), but I know of others with the same setup but with EBC's who had very similar results to me. I think the limits to the turbo being able to hold the boost is it's sheer size - it cannot flow the volume of air required to hold the pressure to the red line. It's a physical restriction rather than an issue of boost control. If small turbo's can hold high pressure at high RPM then there would be no need for big turbos would there?

I'm not even convinced a K26/8 could hold pressure to the red line either.

2bridges

26/6 rock solid 15psi to redline.

tial 38 - 1 bar spring

easy peasy

sawood12

Are you establishing this via a boost gauge? I find that boost gauges are not quite 100% effective. My boost gauge (and others i've tried) shows me holding boost however the dyno equipment clearly shows it bleeding off as the engine revs rise and it showed this on all K26/6 and K26/8 cars that were tested that day with a variety of mods, wastegates and boost control systems.