Which Camshafts?

[TiTAN]

A worked motor with fuel economy and low down drivability, I would like to see that.

RB30 twin cam with 9.2-9.4:1 compression and a GT35 on the side of it, happily plods around in traffic at 1500rpm and gives ~12l/100km city driving

low gown driveability and response are the things to cling to for satisfaction when a combo just doesn't cut the numbers.

thats why we have twin cam forklift engines because you can have your response and 400kw

[Fastrotor]

Hmm interesting topic for sure.

Since head porting is a major part in making big cams work, i think this should be ok to ask in this thread.

I was doing an excel spreadsheet of all the different rb26 head flow numbers i could get my hands on. Some were better than others in the mid range, some a bit better in the top end, to be expected , with differences in machine measurements and job expectations (we don't know they were all for a 'max' flow job etc. Anyhow point is, they were pretty close to each other with nothing HUGE standing out...... EXCEPT ......

Endyne......... and only the exhaust ports..... they were on top in the intake too but only by a small amount. On the exhaust flow results, most topped out at 190 odd cfm ................. there's was around 230+ cfm !!!!!!!!!

Im peeved i seem to have deleted the xlsx spreadsheet else i would post. I guess i could redraw it if anyone was keen to see.

So i'd like to hear from the guru's what they think.

Paul, you being the RS guru, do you have flow numbers for your head please ?

[djr81]

Be interested to find out what the stock cams lift & duration are. The numbers in the R32 manual don't make much sense.

[NickR33]

its my understanding that lift and duration have different effects too... duration refers to where in the rev range they are most efficient and increased lift means more airflow at that rpm (which usually means more power)

I've got 260º 10.8mm cams but engine builder reckons he would just go back to standard cams for my car, no real gain to be had in his opinion... but I like the sound lol

[livicuru]

im sorry but yours sounds like one of the worst setups i've ever heard of on a rb

You reckon? well according to my tuner my high mounts with the slighty down sized rear housing come on boost the same time as Rs's but only much harder. Anyway, you have no idea about the overall setup i have and how it compliments the remainding engine mods, hence your narrow statement.

All the best Jam; dont sell your Rs's.

[JAGR33]

Lol I completley agree with you there. but isnt this guy building a street car...id be willing to sacrifice some top end in a street car for better (in theory) fuel economy and low down drivability.

Hit the nail on the head!!!

Interesting thread, guaranteed to get people fired up!!

I did run 260/9.15 lift poncams with -5's on a built motor, but reverted back to standard cams under instructions from my tuner/mechanic.

One major difference I noticed was pulling into my driveway at home and driving up into the garage (very slight incline). With Poncams my car used to be lethargic. Travelling 10km/h up the driveway my car felt like it needed revs to get into the garage. Once the standard cams were put back in the car it would pretty much idle up the driveway into my garage without a sweat. Now what does this mean? Maybe someone with more technical knowledge than me can explain...

I also felt my on/off boost transition more responsive aswell.

The car made just as much power and similar response (maybe slightly favourable with standard cams) to the Poncams..

Just my 2c....

[N1GTR]

Step Zero;

Suits Stock turbos or GTSS, 8000rpm.

Quite a rare crank though, id be suprised if there was many more step zero's than kakimoto's or apexi highdecks.

Anyway, here's a PDF from HKS about this kit:

HKS_Step_Zero.pdf

[djr81]

Hit the nail on the head!!!

Interesting thread, guaranteed to get people fired up!!

I did run 260/9.15 lift poncams with -5's on a built motor, but reverted back to standard cams under instructions from my tuner/mechanic.

One major difference I noticed was pulling into my driveway at home and driving up into the garage (very slight incline). With Poncams my car used to be lethargic. Travelling 10km/h up the driveway my car felt like it needed revs to get into the garage. Once the standard cams were put back in the car it would pretty much idle up the driveway into my garage without a sweat. Now what does this mean? Maybe someone with more technical knowledge than me can explain...

I also felt my on/off boost transition more responsive aswell.

The car made just as much power and similar response (maybe slightly favourable with standard cams) to the Poncams..

Just my 2c....

It means that longer duration cams work less well at low rpm.

Here is a rough chart showing the durations of stock versus Poncams. Pretty obvious but I don't know what the lift is on the stock cams.

[Beer Baron]

stock lift is around 8mm. maybe 8.5mm.

edit, stock are 240 in with 8.58 lift and 236 ex with 8.28 lift.

[bigslick]

All the best Jam; dont sell your Rs's.

I wish you all the best with your setup too, Jamtime, but your step 0 kit is going to be significantly outpowered by the GT-RS's.

Even the crank in the step 1 wouldn't be able to use them to their potential.

Personally I think -5's make a great street turbo, with a 2.8 stroker even better, but not that one.

[R.3.2.G.T.R]

great thread, been reading other poncam discussions however nothing similar to my setup, rb26 with gt-ss with no headwork but with cam gears, I read -5 guys using the popular 260 9.15mm combo (type b) but not a lot of info with gt-ss

What bout tomei type a which is staggered setup?? Must be of some benefit for smaller turbos.. Type B surely isn't more suitable as it will move the powerband higher.. Is stock cams still best with gt-ss?? Btw car is street driven as a daily

Type A

Duration(IN)- 260°

Duration(EX) - 252°

lift(IN) - 9.15

lift(EX) - 9.15

Type B

Duration(IN) - 260°

Duration(EX) - 260°

lift(IN) - 9.15

lift(EX) - 9.15

Edited January 21, 2010 by BWRGTR

[djr81]

great thread, been reading other poncam discussions however nothing similar to my setup, rb26 with gt-ss with no headwork but with cam gears, I read -5 guys using the popular 260 9.15mm combo (type b) but not a lot of info with gt-ss

What bout tomei type a which is staggered setup?? Must be of some benefit for smaller turbos.. Type B surely isn't more suitable as it will move the powerband higher.. Is stock cams still best with gt-ss?? Btw car is street driven as a daily

Type A

Duration(IN)- 260°

Duration(EX) - 252°

lift(IN) - 9.15

lift(EX) - 9.15

Type B

Duration(IN) - 260°

Duration(EX) - 260°

lift(IN) - 9.15

lift(EX) - 9.15

A -5/Poncam B combination will put your maximum torque at 5000rpm or higher depending on what boost you run.

The inlet cam on the type A & B is the same cam.

The exhaust cam on the type A is, in duration, very little different to the stock cam, just with higher lift & very slightly less advance.

Curiously I have seen very few people running -5's with the type A's. I really cannot find a good reason not to use this in place of teh type B's.

Also Tomei will sell you inlet cams with a 252, 256, 260, 270, 280 etc etc durations. You can mix & match & don't have to select a type A or a type B set up.

[Roy]

Dont std RB26s make peak torque at something like 6,000rpm...cannot see how bigger duration/lift cams are going to dramatically bring it down?!?!?!

[djr81]

Dont std RB26s make peak torque at something like 6,000rpm...cannot see how bigger duration/lift cams are going to dramatically bring it down?!?!?!

About 4200rpm.

[Roy]

LOL, they sure dont feel like it to drive

[djr81]

LOL, they sure dont feel like it to drive

Should feel like a turbo diesel compared to RB20 powah.

At the end of the day it is a turbo motor & when you start running anything like a sniff of boost (1 bar or better) the peak torque is going to move up the rev range. The issue is, I guess, how to make good torque in the midrange (say 4000rpm) without it dieing in the arse up the top end.

[Piggaz]

Whats a "GT RS" head worth?

Rough spec list Paul? (PM if you like)