WERK-I

jhunt,
Thanks for the dyno chart. It illustrates clearly what I am experiencing. The torque curve is rapidly falling off it's peak after 4600-4800RPM. Since Torque has a direct relationship with volumetric efficiency(VE), all other factors being constant(stroke, cam timing, etc.), something is amiss. Ideally, I would prefer a relatively flat torque curve and I would think that would be the case in turbocharged engines since VE is increased as boost increases.
We must have miss-matched our cams to our turbocharger's profile, yes? I don't think we have reached the point of diminishing returns on fueling, since we are still within the limits of the CIS(.7bar).

Cobalt,
I am assuming you are using the factory 964 grind. Is that right?

Kevin

PT;

Is your HF from a 7200 or 7006? Do your have damage to your turbine wheel? Cam timing and camshaft selection will effect your torque curve... I prefer the 964 grinds for higher torque curves when running CIS.. However, there are other camshaft selections when one considers the switch to an EFI system.

PT

Kevin,
You rebuilt my HF from a 7006 last year. When I took off the muffler to look at the turbine wheel, it looks fine to me - no chipping/missing pieces/etc. When I timed the CAM last year, I set it to 1.578mm, which is within spec for the SC cam. Does this all sound reasonable to you? The torque certainly feels that it peaks around 5200 & stay flat till about 6,000.
The car does not mind revving right to 6800, its just that there's no point as the torque doesn't seem to support revving that high. Do you think a 964 cam will help? Boost-wise, I'm running .9 bar according to my VDO gauge.

Randy

Here's a 3.4, 964 cam, Kevin's HF K27/7200 at .8 bar.

PT

Thanks for sharing Randy... but looking at your torque curve, it doesn't seem a whole lot different than my case based on my seat of the pants. Kinda surprising...

PorschePhD

Actually I would bet that the raw numbers show close to 5500 drop in peak tq. Honestly this is about par for the SC cam. The 330 and the 964 both move above that.

PT what was your timing side to side?

WERK-I

PT,
Actually, Randy's torque curve is what I would desire in my engine. It has a nice relatively flat curve from 3000-5800RPM. Shifting at 6K with our wide-ratio 930 gears would keep the engine in the "sweet spot" of the torque curve. The engine seems to suffer a bit below 2800RPM which would be somewhat aggravating driving around town, but for me, I'm not driving a cruiser. :-)
For the sake of clarification, could everyone on this thread provide the engine mods/specs for their respective powerplants? Here's mine:
Kokeln IC
Tial Wastegate (.7bar)
K27-7006 Turbocharger(factory)
Factory CIS
WebCams SC grind
Crankfire/TwinPlug Ignition
Andial Fuel Enrichment
B&B headers/muffler(single out)
C2 cylinders
Compression-Stock (heads flycut once)
Powerflo Intake/Cleaner

PT

Dave, I had an unsuccessful dyno run last year (the dyno incorrectly said my A/F is lean so we didnt complete it) so don't have concrete #s but my torque curve & feel is less flat than Randy's but rise very linearly after the hump/jump (mine occurs at ~2700 rpm).

Steve - my timing side to side was exactly the same before the engine went back into the car. I double check the timing after 1000 mile when I redo my valve adj & found that the timing had moved from 1.578 to 1.46 (cylinder 4) /1.40 (cylinder 3). I didn't readjust it but it does bug me if a) its normal, b) is it still close enough that I can ignore it?

My engine spec - stock everything except K27HF/Euro CIS/Garretson IC/GHL header/Borla muffler/Andial fuel enrichment (off)/Powerflow/Tial WG .6 bar/Profec B EBC

Kevin

Patrick you have to remember that you have the 7006 (larger turbine wheel).. Randy has larger cylinder head ports! His engine is flowing more air.. If you are running rich, dial the boost to 1bar..

PT

Hi Kevin, yes, understand that nothing beats displacements & good head porting... And will definitely try cranking up the boost this season now that I'm quite sure the engine is holding up well.

I'd really like to extend the torque range by another 500 rpm or so hence curious if the 964 CAM will do that for me. From an absolute # perspective, my premature dyno session said I'm seeing 330 rwhp and 300 ft-lb based on .6 bar w/ EBC off. So I have a feeling its in the right range?

Kevin

Making the switch to 964 cams will increase your torque.. If you are thinking of a EFI conversion, I'd install EVO cams or the RS grind..

PT

Thanks for the advice Kevin. Sounds like I should wait till the next overhaul, decide on EFI or not then change the CAM.

BTW - how's your EFI system coming along?

JBrown

Randy is that dyno with CIS, if so what is done to the motor, i have a 3.5 turbo and put a k-27 hf from kevin and never dynoed with new turbo yet. Thanks John

Kevin

Randy's car runs the CIS, 3.4ltr Mahle's, twin plug, 964 cams, 38mm cylinder head inlet ports..

bogey1

Sorry not to respond, been out of town.
Werk1: my build is pretty similar, not sure if you bumped the compression of not? The HF k27 run's all the way to redline, period. I think the cost for the build was $750-$800 from Imagine/Evergreen. I think they pretty well gut the turbo and replace everything with lighter wheels with more blades. My cams were listed on my work invoice as a "custom grind SC". Stephen at ImagineAuto could tell you more. Its the third turbo in 5,000 miles because I felt like you each time; close but no cigar. The HF is perfect, and the dyno will show a great HP/Torgue curve. In terms of driving the car, it still has a great kick when the boost spools, but in general it has better throttle response, and is much easier to drive fast as it builds power. The dyno show's peak horsepower at 5500 rpm, but the fall off is very small to redline. I also run the car at 1.0BAR most of the time.