carreracoupe997

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

Black51

I have heard the stock AFM can only support up to 320hp, iirc. Can't remember if that's whp or bhp, but I've heard that number before. After that, it runs out of snorkel room. So perhaps a k26/8, k27/6, or an upgraded Evergreen turbo might work well.

cannon1000

Article - might help. http://ducati.itgo.com/pictures/944/

Oddjob

I picked up a track car last year that came w/ a powerhaus K27DR (modified K27/6) still using the stock AFM. Had dyno'd in the 320-325 hp range at 17 psi on race gas. Did not have the stock airbox, instead had a K&N cone routed up near the driver side headlight location (headlights had been removed).

Reimu

I have the stock afm on my 60-1 which has a 3" inlet. Just had to be a bit inventive, I'm also using a cone filter in place of the snorkel/airbox that goes near the driver's headlight.

Granted I did this as more of a temporary thing

carreracoupe997

Oddjob, How did the car do on the track?

Oddjob

That same engine was 7-8 mph avg faster (by GPS data logger) at the end of the 1 mile front straight at my home track w/ the K27 at 15 psi, compared to a K26/8 at the same peak boost level (unfortunately I had to replace the 27 w/ a 26/8 for stock class rules).

Previously I did not think a K27/6 would signficantly out perform a 26/8 at the same boost pressure, especially when running a moderate boost level. But the 27 held 15+ psi flat to redline, where the 26/8 dropped to about 13 by redline. It didnt run out of breath above stock boost levels like the k26s do when nearing redline in 4th gear.

You can send your K26/6 to a guy like Charlie at Evergreen and he can build it into a modified K27/6 for very reasonble money.

The compressor inlet is 2.75" (k26 is 2") so you need to modify the intake j-boot to work (there are a few ways of doing this) and a couple fitment issues w/ the water pipe and temp sensor. But otherwise its pretty straight forward installation. A lot of threads on here related to this. Should be able to be setup to run w/ the stock airbox.

67King

Steve, just because you CAN run a big turbo does not mean you SHOULD run a big turbo. PM on the way about what some of your fellow Peachstate Track Committee folks experienced in Roebling.

333pg333

Jim, just out of curiosity, even though the k27 pulled 7mph faster down the straight, did it also translate into faster tracktimes with what I assume might have been a tad more lag?

Oddjob

I have only used the data logger a couple of times, so I do not have a ton of lap data to compare. For the two specific events comparing the K27/6 to the 26/8, I cannot make a fair/equal comparison of lap times, since the condition of the tires was not the same. Also, the original setup on the car was not exactly to my liking - too much oversteer.

For a 3 mile track w/ lap times in the range of 1:50 – 1:55, I would guess the extra power to equate to maybe 1 to 1.5 seconds a lap faster time.

I would also guess the power difference between the K27 vs the 26/8 at 15 psi to be maybe as much as 20-30+hp. Definitely more than 10-15hp.

The long. accel. (from the data logs) was stronger everywhere on the track, and speeds and rpms into braking zones were equal or higher w/ the K27. Shift points were noticeably earlier.

I did not notice any difference in lag or feel when the boost came in. The only difference I could tell by seat of pants was that the car pulled hard well into the redline w/ the k27, and the same engine really started running out of breath w/ the 26/8 above 5500 or so in 4th.

carlege

i guess i would have thought that the 8 hot side would hold boost longer than a 6. or is this because the bigger k27 dosent have to spin as much to produce the 15lbs of boost

racerxrick

Give Dave at LR...he'll give you some great options that will work well with your parts combo! My car runs nice and crisp with one of their Super Series turbos.

Have fun!

95ONE

I ran my 11 sec 1/4 mile run with the Stock AFM. Max chips and required fuel. So.. no limit.. at all.

JustinL

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%).

67King

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!