Paulyy

I've done a few searches but havn't found what im looking for.
The question came while me and a few mates where talking cars while having coffee.. That is it possible to get the 26/6 to hold 15psi at redline with out dropping down to 12-13psi with out modding the turbo its self.

if its even possible but have 1:1 exhaust pressure and 'boost' to hold more boost at redline?

I have no idea.. Hope i can learn something from this.

86 951 Driver

I think it has been determined as no. The turbo itself becomes the restriction in the exhaust. I know on the older DSM's people would port the turbo to get some more flow out of them. I don't see people here do that too much. I don't know if its not effective or what.

lee101315

The k26/6 is good for longevity and reliablility, and that's it. I could never get it to hold a steady 15psi from 3k to redline, and that was with multiple wastegate setups, the last of which was a mbc with a 38mm tial wastegate. If you want 15-16 psi at redline, you have to crank it up to 18-19psi.

That goes for the k26/8 as well.

I have a k27/8, and it holds 16psi from just over 3krpm to redline... No spikes or dips.

Paulyy

Thats what i was looking for, did you see any power difference when you crancked it up or it was the same because of the hot air the turbo was producing?

Black51

I agree on this at least from experience with the 26/6. I haven't really noticed much power increase when cranking the boost up to 18 psi in say, 3rd gear. I certainly don't think the car gains along the lines of the generally accepted ~10hp/psi with the 26/6. Looks cool though!

lee101315

Many say that you shouldnt run more than 15 psi on the k26/6 because it creates too much back pressure.

I ran 18-19 psi, with autothority chips, 3 bar fpr and a straight pipe exhaust for over a year without any problems. I never spent much time over 6000 rpm, though. I did notice a huge increase in midrange torque jumping to 18psi, but the top end remained boring as usual....

racerxrick

I ran 17-18 psi on the 26/6 most of this year and the PO did for almost two years (I finally popped the headgasket this fall). I used a 2 1/2" exhaust w/test pipe, DP WG, MBC, etc.

I agree that the mid range was GREAT but boost dropped like a rock after 6k...like from 17psi to 12psi.

Black51

well racerxrick, you got that problem taken care of!

minho78

Pauly I just took my car apart and I have a k27/6 to go in there now. THe K26/6 is small and that's why it runs out of breath. From what it looks like the K27 compressor is almost double the K26. I believe the K26/6 can hold 15PSI to redline if everything else is Ok, but it will kill the turbo faster.

brrgrr

I don't think a k26/6 can hold more than 12 psi or so to red line, regardless of how high you set the midrange. They spool pretty quick and hit hard but the compressor just isn't big enough to flow the air at the top end, and the the air you do get will be very warm.

Paulyy

yeah i have the top half of my engine apart because of some oil leak. just looking at the turbo it is small, but always think it could of been better for its size to flow more.

i was thinking before, what if you close the wastegate at 4k and let the turbo over spin, would it have enough to push through 15 psi. regardless if its bad for the turbo just in theroy.

i guess thats why they had the stock boost at 10 psi would of been quite a punch back in 86 i guess.

Paulyy

I've got another question for you all i know im pushing the limits with the 26/6 but i've upgraded my intercooler (as shown on my avitar) and also put in a test pipe and also data logging A/F ratios and Boost with my Innovate LM-2

I've been told by boostin the turbo over 15 psi just creats more back pressure and a warmer charge. since i've got a larger core intercooler, it should cool the charge down and more "Power" -said in Jeremy Clarkson voice-

What do you guys think ?

Thom

It actually works the other way around - removing the restriction on the intake side by fitting a free-er flowing intercooler means that the stock exhaust becomes even more of a restriction.
The exhaust and the IC are designed to work in balance.

Fitting a free-er flowing intercooler should be always done in conjunction with installing a free-er flowing exhaust, otherwise it will makes things such as back pressure & knock worse.

Fitting a bigger exhaust with the stock IC is fine, doing it the other way around is a no-no.

Paulyy

hmm okay. so your saying a 2.5 straight pipe isnt free enough?

Thom

No it's not. You want at least 3" exhaust tubing right away from the downpipe.