![Wink ;)](./images/smilies/icon_wink.gif)
But I would like a jury of opinions. You already know the situation. But if you want to interject.....well that's fine too!
Anyway, I am getting ready to turbo my M20, 1988 SuperETA mfr'd 3/87 and wanted to get some thoughts on how my current cam setup will fare with the turbo selection.
I am currently considering a GT28RS and a GT2871R like Dan's. The motor was originally built to simply be an e to i swap, and has a 325i 885 head with 325i TB and a ported 325i intake on the stock bottom end.
My current cam is an ireland engineering re-grind - 272/272 with 50 degrees of overlap. This much overlap is a negative for FI from what I've learned, but in my extensive searches, i cam across this thread http://www.mye28.com/viewtopic.php?t=26596 where Duke's and Russc's comments lead me to believe that it won't be such a bad thing.
In an effort to avoid pulling the head at this time, I wanted to keep my current cam. I plan to shoot for 10lbs of boost on the stock internals. My headgasket is new.
I have an extra stock e30 cam i can use if the 272 doesn't work out. But assuming the 272 will be the cam of choice on the first turbo attempt, as it relates to turbo choice, Dan is pretty much set on the GT2871R with a .86 turbine housing and IMHO, there is very little reason to question anything Dan suggests as I have found his every decision on equipment to be supremely well thought out. However, my tuner has come up with the GT28RS as being more appropriate. The GT28RS is geared more to the low end of the powerband, albeit just a hair.
here’s a good thread on the GT28RS vs. the GT2871 vs. the GT3071. Different car obviously, but i would think many of the same principles apply.
http://www.audiforums.com/archive/threa ... 010-1.html
Do you guys have any opinions on this turbo choice given my current cam setup? I have no idea how it feels for power to "fall off a little" at the top end so there is no frame of reference.
My goals:
This will be a daily driver with 6-10 track days per year. I would like to acheive approximately 275 HP and have a respectable track car (as respectable as a SuperETA can be of course).
The way I look at it is like this: The more I can do to shore up the low end, the better. As TCD once told me, the M20 is never going to be torque monster. However, my agressive cam will need to breathe even more at the top end which may push the smaller sized turbo over the edge.
So i have no idea what to expect if I choose a turbo that's "more geared toward the low end' and whether this blower will simply offset the low-RPM weakness of my aggressively CAM'd motor...OR...if the "falloff" at higher RPM will be dramatic to the extent that it is annoying and/or problematic
Keep in mind that I am running a 3.73 LSD, so i can keep the RPM up in the range most of the time. The problem areas are, for example, at VIR, on the North Course, when you go under the bridge and take a left around the corner, up the hill - my car had NOTHING in that turn. It was completely anemic. I had to climb the hill with momentum only. It did very well on the rest of the course, as long as i could keep the RPM up.
Final note: Catcams.com offers an M20 'turbo cam' with attributes that seem drastically different from both the stock 325i cam (which TDan has proved works VERY well) as well as my IE re-grind, . Any thoughts on the effects of this cam on the turbo and how it relates to turbo selection, and whether its worth pulling the head to swap, would be greatly apprecaited.
clearance [cl] I/E 0.25mm 0.40mm
duration [0.1mm+cl] I/E 272° 248°
duration [1.0mm+cl] I/E 234° 214°
valve lift [cl=0] I/E 10.80mm 9.90mm
cam lift I/E 6.90mm 6.35mm
peak angle I/E 110° 120°
timing [1.0mm+cl] I/E 7/47° 45/-11°
lift at TDC [cl=0] I/E 1.90mm 0.70mm