100% Track Car....What Turbo can I run with stock AFM?
12-12-2011, 08:19 PM
#16
Rennlist Member
I have that same K27DR turbo. I've found it to be stronger across the range compared to the 26/8. No big difference in lag at all. I think the #6 turbine chokes up the exhaust a bit more and crossover pipe pressure/temperature has to be higher. I am running a Lindsey 4" exhaust, very free intake, and megasquirt for fueling. My laptimes dropped quite a bit going to this turbo (probably 2%).
I have measured backpressure in the crossover, EGTs, and intercooler temps on 26/8 cars, but I never tested that car while it had the K27 on it. Kicking myself for not doing so, because it has come up in conversation a couple times since I removed it from the car. I am curious how much effect on backpressure and EGT there is, and what the corresponding intake temps would be at equal boost levels between a 26/8 vs 27/6 vs 27/8.
FWIW, said driver I mentioned at Roebling went 0.25 seconds slower than his previous best when going to the bigger turbo (to K27 from K26, I think 8's on both hot sides). He also went from E to SP3. Another driver who was there who also went from E to SP3 went 1.8 seconds faster. Class record for SP3 is 1.3 seconds faster than for E. Roebling is a pretty tight track, though. Other tracks may show the opposite results. And I haven't talked to him, so there may have been other things about which I don't know, but I did talk to the other driver who is a good friend of his and they always pit together. He didn't mention anything funny, other than running a lot closer to him than he usually does!
Wait......I'm trying to move up to Club Racing next year. No, y'all go put on the biggest turbos you can find!
Wait......I'm trying to move up to Club Racing next year. No, y'all go put on the biggest turbos you can find!
PCA E cars are limited to 26/6 turbos, and SP3 allows 12.5 psi max boost - so there is some reason to install a different turbo if jumping from a stock E car to SP3 (since a 26/6 wont hold 12.5 flat to redline w/o an EBC setup). But I don't think there would be much of any benefit to go w/ a K27 over a 26/8, as a 26/8 should have little problem w/ holding 12-12.5 psi to redline, and I am not sure how responsive a K27 compressor is at those lower boost levels, even w/ a -6 hotside.
12-12-2011, 10:23 PM
#17
Race Car
PCA E cars are limited to 26/6 turbos, and SP3 allows 12.5 psi max boost - so there is some reason to install a different turbo if jumping from a stock E car to SP3 (since a 26/6 wont hold 12.5 flat to redline w/o an EBC setup). But I don't think there would be much of any benefit to go w/ a K27 over a 26/8, as a 26/8 should have little problem w/ holding 12-12.5 psi to redline, and I am not sure how responsive a K27 compressor is at those lower boost levels, even w/ a -6 hotside.
Of course, if one weren't limited to the boost they could run, it might be a different story, but in the context of SP3 (as Steve is targetting), the 26's are fine. I wonder if a 26/6 may be better at some tracks, too. But I will say that the 26/8 that Charlie built me is every bit as responsive as the old 26/6 I took off (though I've lost about 300 pounds in the process).
12-12-2011, 11:42 PM
#18
Rennlist Member
I have a 1986 951 Track Car with stock K26/6. I am running 3" open exhaust, MSD, 951 Max chip set, manual boost control, Lindsey adjustable fuel pressure regulator, Lindsey dual port WG. What is the best (larger) turbo I can run using the stock barn door AFM? I do not mind changing injectors or downpipe if I need too. I simply do not want to go to a MAF or MAP system. I know I can run a K26/8 but by the time I purchase and rebuild it I would be close to the price of something that might be better. Again I am speaking of turbos that will be compatible with the stock AFM only. Thanks
12-13-2011, 07:49 AM
#19
I have heard the stock AFM can only support up to 320hp, iirc
12-13-2011, 01:57 PM
#20
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IICR Josh (Rogue Tuning) mentioned that his C-Tune (stock afm) is good for 350 rwhp. so with the right chips and turbo you could have a good amount of power.
12-13-2011, 09:05 PM
#21
I'm one of the drivers 67King mentioned. There are really too many variables to be able to make a firm comparison. I will say, my initial observation, was quicker spool and power on the K26 and more power further down the straight with the K27. Qualifying times were within 1/2 second. But, too many variables, like tires, weight, gearing, to say for sure. Also, both turbos, the K27/8 and the K26/8 recently underwent a rebuild, courtesy of Charlie at Evergreen. All and all, the performance was pretty darn close. Slight correction to one previous comment. Both driver posted their fastest times ever that weekend. The K26/8 top speed was 5 to 7 MPH faster than with the stock 26/6 turbo the previous year. No other major change with the car except the turbo. After market boost gauge is showing around 12.5 PSI with the 26/8. It falls back to around 11 PSI at just under 5500 RPM.
12-14-2011, 01:42 PM
#24
Race Car
I've wondered how that is interpreted. "Exhaust systems are free after teh exhaust port." I have generally seen turbos as part of the exhaust sytem, but the impeller side could certainly been seen as induction. I hear most people fall back to the allowable power when 944 Cup is run with NASA.
