Largest Set Of Factory Located Twins On Rb26 R32?

[Marko R1]

I can't comment on that ash BUT I'm sure I can ask rob what afr he uses...shall I ask him

[Marko R1]

Paul - answer me this...did my rb30 have a truck load of torque with 280's? U drove it so why not share your experience haha (yes it was a 3ltr BUT it had big cams)

[Piggaz]

Paul - answer me this...did my rb30 have a truck load of torque with 280's? U drove it so why not share your experience haha (yes it was a 3ltr BUT it had big cams)

Yes it made more grunt down low and it had more torque then mine (as you would expect for the longer stroke) but having driven Steve's his definitely came on earlier again.

[R31Nismoid]

Steve must have 290s then

[Marko R1]

I stand corrected HAW HAW HAW!

[bigmikespec]

It is funny how pople blindly believe what people tell them without any understanding as to why certains things occur. It is no magic Racepace trick that stock camshafts work well with small internal wastegate turbocharghers like any of the common low mount upgrades on a GTR. Exhaust manifold back pressure is significantly higher than boost pressure is most of these scenarios... big duration camshafts would cause reversion of the exhaust due to the pressure differential and overlap that the camshafts give. Thus very short duration camshafts are ideal for small (ish) low mount turbocharger upgrades because of the compromised turbine housings, internal wastegates, etc.

On the other hand tubular single turbo manifolds with large external wastegate turbine housings create a much lower exhaust manifold back pressure. Once the ratio of exhaust manifold back pressure and boost pressure get close to 1:1 then is the time for big duration camshafts with appreciable overlap. What will occur is almost a scavenging of the exhaust ports as both inlet and exhaust valves are open at the same time; in short, with a sacrifice lower in the rpm range higher power is achievable and it will come on earlier as guys like Red R Racing have proved.

I would be measuring exhaust manifold back pressure before choosing cams.

Also, instead of people choosing small cams with the belief that it will bring on bigger turbochargers earlier they should be getting more head work, extrude honing OEM manifolds and get a decent twin 3" exhaust!

[DVS JEZ]

^^^ what he said. Paul did explain it to me but waaaay to long to write especially on my phone.

Well said bigmike

[Marko R1]

Thanks for sharing Mike and its about time we have an educated response on this thread...in other words, small turbos run with small cams and large turbos run with big cams - for optimum results which makes sense.

Now with your last paragraph on the belief of running smaller cams to bring on power earlier, I was advised exactly what you wrote and I did that (only because i was running larger turbo's, -10's) i.e. Head and oem manifold work. Obviously my power band was also dependent on my tune and how the cams were dialed in (my clear instruction was to crack over 400awkw which I did). it was not tuned for mid range, although, was still more than a handful

I dont 'intimately' understand the mechanics of what combinations work best as I don't have the experience of building and tuning 100's of cars and its obvious that most ppl here are in the same boat hence it is a sigh of relief reading your post

[R31Nismoid]

lol not tuned for midrange?

[Marko R1]

lol not tuned for midrange?

u have never been asked what type of tune would u like?

i.e. street tune, race tune, is your goal peak power or mid range drive-ability? i guess my tuner is more thorough...what can i say

[R31Nismoid]

You really should just put the shovel down sometimes dude.

[Marko R1]

i am biting my tongue

im not stooping to your level ash, however, i will commend you on your approach - good work

[WARLORD]

lol i told you marko !!

[Ryan1200]

It is funny how pople blindly believe what people tell them without any understanding as to why certains things occur. It is no magic Racepace trick that stock camshafts work well with small internal wastegate turbocharghers like any of the common low mount upgrades on a GTR. Exhaust manifold back pressure is significantly higher than boost pressure is most of these scenarios... big duration camshafts would cause reversion of the exhaust due to the pressure differential and overlap that the camshafts give. Thus very short duration camshafts are ideal for small (ish) low mount turbocharger upgrades because of the compromised turbine housings, internal wastegates, etc.

On the other hand tubular single turbo manifolds with large external wastegate turbine housings create a much lower exhaust manifold back pressure. Once the ratio of exhaust manifold back pressure and boost pressure get close to 1:1 then is the time for big duration camshafts with appreciable overlap. What will occur is almost a scavenging of the exhaust ports as both inlet and exhaust valves are open at the same time; in short, with a sacrifice lower in the rpm range higher power is achievable and it will come on earlier as guys like Red R Racing have proved.

I would be measuring exhaust manifold back pressure before choosing cams.

Also, instead of people choosing small cams with the belief that it will bring on bigger turbochargers earlier they should be getting more head work, extrude honing OEM manifolds and get a decent twin 3" exhaust!

Very detailed post mike looks suspiciously like something dirtgarage would have posted back in the day....

[DVS JEZ]

U would almost think they know what they are talking about. And have proven it

[R31Nismoid]

It is funny how pople blindly believe what people tell them without any understanding as to why certains things occur.

No better example of this than ole mate Marko really.

i am biting my tongue

im not stooping to your level ash, however, i will commend you on your approach - good work

About time you did, everyone will benefit.

I mean you supposedly asked for a tune without a midrange...

And are firmly on the big cam bandwagon this month:

Good point and why I had 280 degree kelfords in my 2630

Yet only 2 months ago you come out with this?

Hi all,

My rb30dett is now fitted in my mates circuit GTR ...

The 280degree cams are too big and power comes in too late for circuit so will swap them out for 264/11mm lift to bring turbos on 1000rpm earlier.

Says it all really.

[WHITER33GTS-T]

I have 280s in my 26/30 cause I wanted a lumpy idle

[bigmikespec]

Very detailed post mike looks suspiciously like something dirtgarage would have posted back in the day....

Ryan give me a call man happy to discuss. I do my own research... I am disappointed you think that. Might just keep the information to myself in future.

[rob82]

It is funny how pople blindly believe what people tell them without any understanding as to why certains things occur. It is no magic Racepace trick that stock camshafts work well with small internal wastegate turbocharghers like any of the common low mount upgrades on a GTR. Exhaust manifold back pressure is significantly higher than boost pressure is most of these scenarios... big duration camshafts would cause reversion of the exhaust due to the pressure differential and overlap that the camshafts give. Thus very short duration camshafts are ideal for small (ish) low mount turbocharger upgrades because of the compromised turbine housings, internal wastegates, etc.

On the other hand tubular single turbo manifolds with large external wastegate turbine housings create a much lower exhaust manifold back pressure. Once the ratio of exhaust manifold back pressure and boost pressure get close to 1:1 then is the time for big duration camshafts with appreciable overlap. What will occur is almost a scavenging of the exhaust ports as both inlet and exhaust valves are open at the same time; in short, with a sacrifice lower in the rpm range higher power is achievable and it will come on earlier as guys like Red R Racing have proved.

I would be measuring exhaust manifold back pressure before choosing cams.

Also, instead of people choosing small cams with the belief that it will bring on bigger turbochargers earlier they should be getting more head work, extrude honing OEM manifolds and get a decent twin 3" exhaust!

Why does wastegate orifice size matter? If the boost is stable then there is no difference in exahust backpressure between a 38mm gate and 60mm gate.

If manifold backpress is approaching 1:1 a smaller profile camshaft will always spool earlier in almost all applications if both are timed to deliver maximum response. This is due to the fact that smaller profiles generally mean smaller lift which increases port velocity therefore increasing the scavenging effect.

But then what is the point of a large turbo on a displacement that is only going to be useful above 6000rpm if the cams wont support airflow above 7000rpm.

[Ryan1200]

Ryan give me a call man happy to discuss. I do my own research... I am disappointed you think that. Might just keep the information to myself in future.

All good man just having a friendly dig.. Back on topic...