Which cam for efi?

Ken911 · 08:08 AM

ok I am still collecting parts for my EFI conversion sometime in the dark distant future. I have a 3.2 intake and a set of heads that will be port matched and twin plugged. It is a 3.4 with 7.5 to 1 JE pistons. My question is should I go with 964 cams or GT-2 cams? i am currently running ssc cams.

rodolf · 03-02-2011, 05:57 AM

Hi,

Camshafts order by power :

SC < 964 < GT2

964 cams are great for 500HP and less (better torque, street engine)

GT2 cams are better for peak power, 550HP and more ! (i hope

)

pkracer21j · 03-02-2011, 06:00 AM

Ken, talk to Reaper, he has a custom grind for big HP

Ken911 · 01:16 PM

i was looking for best i could get with my existing turbo which is a k-27 hfs without going whole hog and twin turbos. I still drive it to work every day and use the AC which is mandatory for any hot looking blondes half my age who happen to be sitting in the passenger seat.( I do have my priorities lol)

totle · totle's Garage

Hi Ken,

Have a improved GT2 cam in mine. Running efi and Garret GT35 turbo.

rodolf · 03-02-2011, 11:34 AM

Quote:

Originally Posted by totle

Hi Ken,

Have a improved GT2 cam in mine. Running efi and Garret GT35 turbo.

Could you tell me please how many HP do you have ? And torque ? At 1.2bar boost ? Thanks !

totle · totle's Garage

Hi Rodolf,

According to previous owner.
At 6200 rpm and 1 bar, 448 lbs torque and 529 HP

I have not had the chance to take it to the dyno yet. Waiting for snow to go away and roads to be clean of salt.

David · David's Garage

My opinion is Garrett GT35 or 37 or K27HF2 would make use of the higher end of the GT2 cams otherwise 964 would be fine. I'm running 964 cams with a K27HF2 and my power curve is very linear from before boost up to about 6400 and then it starts falling off but still easily pulls to over 7000 rpm.

Ken911 · 03-02-2011, 05:16 PM

Quote:

Originally Posted by David

My opinion is Garrett GT35 or 37 or K27HF2 would make use of the higher end of the GT2 cams otherwise 964 would be fine. I'm running 964 cams with a K27HF2 and my power curve is very linear from before boost up to about 6400 and then it starts falling off but still easily pulls to over 7000 rpm.

my k-27fs is like that now pretty much

David · David's Garage

Quote:

Originally Posted by Ken911

my k-27fs is like that now pretty much

Maybe I should clarify that a little: It feels like it pulls hard until you shift gears. The dyno readout shows power falling off at 6400 (I don't feel it because I'm trying to change gears before I bounce off the rev limiter.)

I'm making 475 at the wheels so about 550 at the crank and it pulls hard all the way through the rev range. So up to that power level the 964 cams work well. If you want more peak power than that then the GT2 cams may be for you.

rodolf · 03-03-2011, 04:51 AM

Quote:

Originally Posted by totle

Hi Rodolf,

According to previous owner.
At 6200 rpm and 1 bar, 448 lbs torque and 529 HP

I have not had the chance to take it to the dyno yet. Waiting for snow to go away and roads to be clean of salt.

Ok thanks totle, i've just read this into the web link of your dream car :

"the engine produces approximately 525 hp and 496 lb ft of torque... from .4 to 1.4 bar of boost"

"Only" 525HP at 1.4bar should be surprising with GT35 and GT2 cams, but 529HP at 1bar boost is great !

I hope i will have same power as you

TurboKraft · 03-03-2011, 11:33 AM

We've made nearly 600rwhp on 964 cams with a flat 930 manifold.
Some power numbers at different psi levels (built engine, of course):
91-octane
- 465rwhp/409rwtq @ 12.5psi / 0.8bar
- 515rwhp/457rwtq @ 15.8psi / 1.1bar
100-octane
- 560rwhp/518rwtq @ 18.8psi / 1.3bar
- 596rwhp/556rwtq @ 20.3psi / 1.4bar
Power peaked by 6,000rpm -- no need to rev it to the moon.
Those cams work well for a high performance street Turbo.

rodolf · 12:31 PM

100-octane is for racing and 1.3bar or more is not serious with 930 engine.

With 964 cams (at 1.26mm) and 1.1bar boost, standard octane, i've got 496HP. With different setting of 964 cams (maybe 1.5mm?) you can have 530HP..

But for more power (+550), with reasonable boost and octane, you need GT2 cams.

JFairman · 12:42 PM

Quote:

Originally Posted by rodolf

With 964 cams (at 1.26mm) and 1.1bar boost, standard octane, i've got 496HP. With different setting of 964 cams (maybe 1.5mm?) you can have 530HP..

1.5mm would be advancing the cam timing and would theoretically move the power band down a little.

Retarding the cam timing would move the powerband up the rpm range a little and that would be setting them to a lower number than 1.26mm.
Don't know what would be best, maybe around 1mm and the motor would be really lazy and boring to drive around town below 4000rpm.

1.25-1.26 is best for these cams.

TurboKraft · 03-03-2011, 12:48 PM

Quote:

Originally Posted by rodolf

100-octane is for racing and 1.3bar or more is not serious with 930 engine.

100-octane is available at many filling stations, not necessarily a race fuel.
Why is 1.3bar "not serious" with a 930 engine? The "safe" boost pressure for a 930 engine is not a fixed value. Many variables affect this.

Your results at 1.1bar are pretty similar to what we got at 1.1bar on 91-octane pump gas.

rodolf · 03-03-2011, 01:31 PM

Quote:

Originally Posted by JFairman

1.5mm would be advancing the cam timing and would theoretically move the power band down a little.

Retarding the cam timing would move the powerband up the rpm range a little and that would be setting them to a lower number than 1.26mm.
Don't know what would be best, maybe around 1mm and the motor would be really lazy and boring to drive around town below 4000rpm.

1.25-1.26 is best for these cams.

1.26mm is the best timing for 400 to 500HP (street engine, great torque).

What's the difference between 964 cams at 1mm and GT2 cams at 2mm ? Which settings will be the best for more power ? (i think it's difficult to know...)

RarlyL8 · RarlyL8's Garage

Ken, for daily driven street cars we use 964 cams with the K27HFS turbo. CIS tune yields 400WHP and EFI tune 500WHP. Idle is mild and cars drive better than stock.

rodolf · 03-03-2011, 01:55 PM

Quote:

Originally Posted by TurboKraft

100-octane is available at many filling stations, not necessarily a race fuel.
Why is 1.3bar "not serious" with a 930 engine? The "safe" boost pressure for a 930 engine is not a fixed value. Many variables affect this.

Your results at 1.1bar are pretty similar to what we got at 1.1bar on 91-octane pump gas.

Yes race fuel is >100-octane, in france, we have 95/98-octane at filling stations.

I know that boost pressure limit depend on temperatures, AFR, advanced ignition... but i think up to 1.2bar boost, air engine is reliable, and with 1.4bar from 4500 to 6700rpm, it's difficult to be knockless and with correct temperatures.

Ken911 · 03-03-2011, 06:43 PM

I have 93 octane here in florida, Rodolf the 93 octane in the us is the same as 98ron in europe. Looks like maybe just the 964's then a stock pair can be picked up pretty cheap these days.

Jonty · Jonty's Garage

Quote:

Originally Posted by TurboKraft

We've made nearly 600rwhp on 964 cams with a flat 930 manifold.
Some power numbers at different psi levels (built engine, of course):
91-octane
- 465rwhp/409rwtq @ 12.5psi / 0.8bar
- 515rwhp/457rwtq @ 15.8psi / 1.1bar
100-octane
- 560rwhp/518rwtq @ 18.8psi / 1.3bar
- 596rwhp/556rwtq @ 20.3psi / 1.4bar
Power peaked by 6,000rpm -- no need to rev it to the moon.
Those cams work well for a high performance street Turbo.

What AFR's do you try to achieve?