Custom Cams For 3 Litre

[rob82]

It seems that fairly stock-type (head porting + cams + manifolds) 30DET builds can go this way too. Pretty streetable and a step forward from the short stroke bottom end, but not a particularly wide useable rpm range where it makes best torque.

The better builds of those using a 25DET head seem to go with decent fabricated exhaust manifolds and open out those exhaust port restrictions. Mine is a mild build with OEM cast manifold but holds peak torque from 3400-7000 with Tighe cams 8.9mm lift and 265 duration. Might not be best for everyone's needs but it suits mine.

Thats a pretty usable torque range. I had peak torque around 3400rpm and it held to about 5400rpm then started falling away. It wasn't a very usable torque range when its paired with 4.11 diff gears and an rb25 gear with fairly narrow gear spacing.

[bubba]

Thats a pretty usable torque range. I had peak torque around 3400rpm and it held to about 5400rpm then started falling away. It wasn't a very usable torque range when its paired with 4.11 diff gears and an rb25 gear with fairly narrow gear spacing.

That's why I went to 3.9:1 diff gears, the small turbo was only letting me rev to ~5500-5800rpm and with the stock gears (4.3) I was slower than an RB20 32GTSt because I was changing gears so often. Even with the 3.9:1 gears, there was so much torque you could roll on in 5th from 80kmh and still pull like a freight train.

Edited March 23, 2011 by bubba

[Scooby]

I've been looking for some 3.5 front and rear ratios from an R34 GTR, as soon as I can find them they're going in. I reckon 2nd with an 8k redline would be excellent.

Edited March 23, 2011 by Scooby

[bubba]

Wonder what 3.5:1 would be like.. should be plenty of torque to use them but wow.. top end would be phenominal! lol

[Scooby]

Yeah did some calcs on 3.5 diffs, top speed at 8000 would be 366k/hr but pretty sure it wouldn't get there unless it was 700rwkw.

What did you get the 3.9s from, assuming Stagea is awd?

[BoostdR]

260 9.15 for up to 850hp on a 26/30. Any longer duration we found just lost response(at the same lift)...and did nothing to max power. Having said that some will argue a longer duration cam will reduce lag(on a Rb26), but I feel that would be related to the associated lift and porting. I for one would love to try the Mines-wave Shore Pro II Cams 252/252 10.05mm. They are designed for a RB26. Tells you something about duration and lift relation to acheiving a responsive engine. I have had some Gibson cams dialed and the told a similar story, although being staggered by a reasonable amount.

After all we are after max average power, having a cam come into its zone from 5000-10000 is not going to be as quick as 3000-8000 on a rb30 that revs to 8000-8500rpm

Matt

[Scooby]

Where did the 850hp engine produce it's torque and power Matt?

Does anyone know if there's a typical correlation of cam characteristics on long/er stroke motors in terms of lift and duration ie does a longer stroke generally mean more lift, or more duration? For good reasons in terms of the respective effect of lift and duration there may not be a typical correlation, just wondering.

Not sure what the LS boys do when they go from 5.7 to 6.3 using a stroke rather than bore increase, presumably with a lot of street-built strokers due to mechanical limitations the rpm doesn't increase hugely, suggesting duration stays relatively mild but the extra capacity has to be filled somehow during the longer period of the stroke.

[bubba]

Yeah did some calcs on 3.5 diffs, top speed at 8000 would be 366k/hr but pretty sure it wouldn't get there unless it was 700rwkw.

What did you get the 3.9s from, assuming Stagea is awd?

3.9s are in my 32gtst, came out of an auto S13.

AFAIK the only 4WD ratios are 3.5 (34gtr), 4.08 (Stagea), 4.11 (32/33gtr), 4.36 (32GTS4, not sure what the 33GTS4 and 34GT4 used).

I wonder what the 4WD Cimas used? One would think with a v8 and an auto they would be pretty tall gears..

[BoostdR]

Where did the 850hp engine produce it's torque and power Matt?

Does anyone know if there's a typical correlation of cam characteristics on long/er stroke motors in terms of lift and duration ie does a longer stroke generally mean more lift, or more duration? For good reasons in terms of the respective effect of lift and duration there may not be a typical correlation, just wondering.

Not sure what the LS boys do when they go from 5.7 to 6.3 using a stroke rather than bore increase, presumably with a lot of street-built strokers due to mechanical limitations the rpm doesn't increase hugely, suggesting duration stays relatively mild but the extra capacity has to be filled somehow during the longer period of the stroke.

It made 823hp

3000rpm 406nm

5000rpm 879nm

7500rpm 759nm

8300rpm 698nm 823hp @ 22psi

BP98 Fuel with 10% methanol

Matt