R34 GTT Cams project

[Bass Junky]

Hey ppls.

I've been thinking for a long time about Poncams for the R34 GTT.

Currently making 200 rwkw with intercooler, intake, PowerFC, Boost kit at 11psi.

I've got that busted R34 GTT turbo in my office which will be highflowed soon enough.

I have always planned to buy cams as well, and have also always wondered (along with a few others) about the effect of Cams on a stock turbo.

SO, insted of doing turbo first, I'm going to do Cams first and do a report for the forums on the effect along with dyno charts and all that.

I have the option of either 252 duration Poncams or 260 duration Poncams.

Both have the 9.15mm of lift.

How much difference is there between the two?

Am I going to loose torque anywhere with either?

Am I going to loose driveability with the 260 cams over the 252s?

What are the standard durations?

Do you think I will be making much more power or will I just pick up grunt until the stock turbo runs out of puff??

All help appreciated.

BASS OUT

[Binky1970]

Will the cams mess with the VVT on the Neo engine ?

[Bass Junky]

Nope.

The Poncams are designed to work with the VVT

[NJR 34GTT]

Very interested in your results. Keep us posted.

[Cubes]

I'm keen to see the results.

Its similiar to doing cams. I had the stock rb20det turbo tuned up on the RB30DET.

The RB25 head thats been ported/polished, inlet valves deshrouded obviously flows more than the rb20det head. So theoretically its similiar to the rb20det with a really BIG set of cams.

It made 176rwkw on 9psi. Boost could not be held from the std actuators pressure on 11psi.

With the wastegate wired completely open it makes 6.5psi from 4000rpm.

The RB20DET to make that sort of power (170rwkw) needs around 14psi.

So 176rwkw lets say 15-16psi considering the turbo is out of puff by that power level.

My guess is you will make more power on the same boost.

Providing the turbo can keep up with airflow which it should as i've seen up to 220rwkw's on higher boost levels (15-16psi) with the rb25.

But dyno figures are dyno figures.

It will be interestering to see before/after results.

[Bass Junky]

Yeah, I've got a feeling I will make more power through the guts of the curve and make pretty much the same power up top. Once the High Flow goes on however, I will make up the top end better.

So theory goes like this....

Boost is only the restriction made in the system.

If the system can swallow, lets say a figure of 100 unit of air (UOA), with stock cams.

Drop the cams in and the car can then then swallows 120 UOA, as the turbo blows into the cylinder for a longer period of time. This air is also lower in temperature because it is pushing the same amount of air, but at a lesser restriction.

BUT, say the turbo just runs out of puff at 7000 rpm without cams pushing 100 unit of air....

I make higher power then before at 1,2,3,4,5000 rpm.......

Then at 5950 the turbo reaches its efficiency level of 100 UOA. Intake air starts to heat more than is good and the power curve levels off.

Between 5950 and 7000 rpm, the turbo is inefficient and pumping heat, although hopefully not too much because the restriction is less.

Power curve looks meatier then before, makes better power all the way to 5950 rpm at which point it flattens out.

Torque curve looks better all the way to 5950 also. Possibly better in the top and worse in the bottom then before, but not sure.

Boost graph looks a little laggier in the initial stage, because as the turbo spools up (at it's fairy tale linear rate) and the restriction is less, it makes less boost at the same UOA level. Power is still up at this point as the same air at less temperature is in the air (cos of the lower boost level)

Once at 11psi however, the boost stays flat.

Does this all make sense or am I miles off???

I know that the standard turbo is making heat at the top end of my engine range, as when on the dyno, we upped the boost to 12psi and the power didn't change.

SO.... My theory is that I will make more grunt where the engine is 90% of the time, between 2000 and 5000 rpm, and simply flatten out after that, making about the same max power.

Area under the curve however will me improved.....

As I said above, this is very arbitary, but I think its looking in the right direction....

BASS OUT

[Bass Junky]

Actually, after reading Cubes' review on his RB30 with the RB20 turbo, it would be much the same......

Making good grunt early, but dropping off high up...

[dojobi]

I've always wanted to see how a set of Poncams went in an R34. The Neo engine and it's continously variable valve timing will really take to the extra lift I think. I mean the R34 already comes with a bit extra over an R33 because it can compensate by twisting the cam a bit, so I don't think you'll lose that much down low, but you'll really gain in the mid range.

[infected flow]

Hey ppls.

I've been thinking for a long time about Poncams for the R34 GTT.

Currently making 200 rwkw with intercooler, intake, PowerFC, Boost kit at 11psi.

I've got that busted R34 GTT turbo in my office which will be highflowed soon enough.

I have always planned to buy cams as well, and have also always wondered (along with a few others) about the effect of Cams on a stock turbo.

SO, insted of doing turbo first, I'm going to do Cams first and do a report for the forums on the effect along with dyno charts and all that.

I have the option of either 252 duration Poncams or 260 duration Poncams.

Both have the 9.15mm of lift.

How much difference is there between the two?

Am I going to loose torque anywhere with either?

Am I going to loose driveability with the 260 cams over the 252s?

What are the standard durations?

Do you think I will be making much more power or will I just pick up grunt until the stock turbo runs out of puff??

All help appreciated.

BASS OUT

first of all what are u planning with turbo side of things....? just hi-flow..?

then ill answer the rest

about your theory its wrong ...ill explain when u respond.....

[Cubes]

It will definitely be interestering.

Overlaying the torque/tractive effort curves will also tell an interestering story.

Are you running an RB20T actuator or is boost controlled via an EBC/Bleeder?

I don't think the boost curve will react like the larger motor with a superior flowing head (rb20det vs rb30det). i.e dropping off dramatically as mine does.

The power curve will look more like a round curve, making more power earlier, possibly even making the peak power slightly earlier but holding that peak power for longer. Area under the curve.

Not sure really. Will be good to see.

Bass. Any chance of heading down the drags to get a 1/4 time after?

[Bass Junky]

Okay, Infected Flow.

I'll be highflowing the Standard R34 GTT Turbo.

What is wrong with my theory....

Cubes...... Damn straight I'll be off to the quarter.

Although my last effort wasn't really crash hot. 13.9 @ 101 was the best I could muster for the night.

[Cubes]

Bass,

Some good info on turbo and cam selection.

http://www.grapeaperacing.com/GrapeApeRaci...rbochargers.pdf

[Sydneykid]

As most poeple know we have had an R34 GTT (for over 2 years now) with 265 rwkw at 1.3 bar. It uses the Tomei 260 degree Poncams and a GCG ball bearing hi flow. It makes more power EVERYWHERE than when it was standard, that's from idle to rev limiter. The best 1/4 time (I am not a drag fan, so very few runs) was an 11.9 at 120 mph.

We have had similar results from 3 X RB25's running the Poncams, 256's in hydraulic applications (non Neo) and 260's in solid applications (Neo). Bottom line, if I did another one tomorrow, I would put the Poncams in again, they are a very worthwhile upgrade.

[infected flow]

hahaha looks like SK said it for me ...makes power everywhere even with standard turbo...the tomei 260 /9.15mm lift cams are good for top end as well ...with stock turbo with stock boost.... 260 is perfect duration the difference is wether they will be overlapping or not... and since u are hi-flowin turbo go the 260's.

didnt mean to be rude sorry..

[Downforce]

Nice one Pete, good thread. I will be fitting some Tomei 260 poncams in my R34, will let you know the results =)

[Abo Bob]

What turbo do you have GTTR34?

[Bass Junky]

Infected Flow.

I didn'y think you were being rude. Beleive me, if I did, you'd know about it.

Can you explain your take on my theory please.

I would really like the normal, non ultra technical version of the document Cubes posted.

I did read it, but I losts concentraction half way through thinking about those damn cams!!

Cheers

BASS OUT

[NickR33]

not trying to highjack your thread bass;)

my car has just had the 256 Tomei poncams for R33 RB25 installed and will be tuned tomorrow... car is running stock turbo, ecu, and cooler, but has just been rebuilt with forgies etc...

not expecting any major gains was just sick of looking at them sitting on my floor! (they were delayed getting here from Japan and I had the motor was back in the car by the time they arrived)

I am hoping the cams will have more and more of an effect as I increase the amount of air being forced into the motor as I modify it more... my eventual aim is a super tough and responsive motor somewhere between 250 - 300 rwkw ...one day

I will post before and after dyno results tomorrow... I am assuming the result would not be dramitically different to a NEO RB25 so it may shed some light on your plans bass

[IanH]

I was going for the PonCam B set (260' in/ex) to get me around 280rwkw (up from 250rwkw) on my Trust turbo but it all went wrong before I had the chance.#

The Tomei site reccomends them for aftermarket turbos. There's a lad in the UK with them fitted and his mid/high rev-range was alot better than mine.

[Bass Junky]

NICKR33

Extremely keen on seeing your results.