Camshaft selection for a 1000hp RB26/30.

[khezz]

Hello boys and girls.

 

So the bottom end has been sorted with spool rods, Ross 9.0-1 Pistons. Air will be supplied by a GTX4294R turbo. 3x Bosch 044s will be pushing E85 fuel through 2000ID injectors. Now what to do about the head?

 

This will be my daily driver so I am looking at drivability over top end grunt. What Camshafts would you suggest and why?

 

Is it still better to go for more lift over duration or does the higher compression ratio and a bigger bottom end help lag enough that you can go 270+ duration with no major issues?

[burn4005]

daily driver? GTX4294R?

 

*standing ovation*

[GTSBoy]

If you're really talking 1000Hp as a target, then you don't have the option of keeping the duration low.  You need revs and therefore you need cams that will support that.  So 270+ degree cams is almost a given.

There is also no reason to think that your options are "duration" OR "lift".  Realistically, you should run as much lift as you can.  The longer the duration the easier it is to get more peak lift into the lobe.  The limits are imposed by the other parts of the VT (lifter bores, springs, etc).  So whilst I won't give you a specific recommendation here, I will give you a general one that says, get something with big duration and as much lift as you can handle.

For reference, a loooong time ago I was involved in the making of a Supra do ~1000HP and it had HKS 292° cams in it (IIRC) and idled like a race bike.  Used many revs to make the power, on 98.

[khezz]

daily driver? GTX4294R?
 
*standing ovation*

Compared to my two old LM turbos this will be like driving an naturally aspirated engine. Lol

[khezz]

Thank you GTSBoy. It's amazing how things change when you jump up from 700hp to 1000hp.

[WMDC35]

Contact Kelfords, they'll sort something out for it

[khezz]

Contact Kelfords, they'll sort something out for it

Seems to be a universal answer these days when it comes to Camshafts and head parts in general. Cheers.

I should clear something up. I am not chasing a magical 1000awhp. I just want to max out the turbo from time to time. I am told that they are capable of that number though.

[Piggaz]

How big is the engine? I assume a 2.6 as there is no mention of a stroker. What sort of RPM do you plan on spinning this thing to?

[khezz]

Rb2630. 3L 87mm pistons with 9.0 to 1 compression ratio. Turbo is twin scroll ball bearing with a twin gate manifold. Running E85

[khezz]

Hoping it will make all the power before 8000rpm.

[burn4005]

I've got a mate selling a set of tomei procams. they're [email protected] if you're interested.

[baron_von_bootsector]

A bigger cam will definitely be required with the numbers you are seeking and the extra capacity / stroke of the 30 bottom end does address some of the low down shortcomings (debatable depending on which part of the tach you like to live in!) of throwing big cams on an RB26. I run 278 cams on my 3.4 and find they are grumpy sounding but still reasonable to drive gently due to the bigger bottom end. My compression is ~9.5:1 so its in the same ballpark as your setup but I am using twins.

You are going to need significant revs, big cams, headwork etc on that motor to get anywhere near what you are seeking so the daily drive ability is really going to come down to your definition of what is fun / acceptable to drive in traffic.

 

[khezz]

I've got a mate selling a set of tomei procams. they're [email protected] if you're interested.

I may be interested just waiting on some advice from my builder and Kelford.

[khezz]

A bigger cam will definitely be required with the numbers you are seeking and the extra capacity / stroke of the 30 bottom end does address some of the low down shortcomings (debatable depending on which part of the tach you like to live in!) of throwing big cams on an RB26. I run 278 cams on my 3.4 and find they are grumpy sounding but still reasonable to drive gently due to the bigger bottom end. My compression is ~9.5:1 so its in the same ballpark as your setup but I am using twins.
You are going to need significant revs, big cams, headwork etc on that motor to get anywhere near what you are seeking so the daily drive ability is really going to come down to your definition of what is fun / acceptable to drive in traffic.
 

Wow a 3.4l, very nice.

I know the RBs are built to rev. I know it will never drive as nice as my auto F6. But I would rather have a 900hp car that I can drive in morning traffic then brag about a piece of paper with 1000hp on it and need 6000rpm just to get the beast going of the lights.

By the sounds of things I have a very limited choice and slight more of this or that won't make much difference. Thanks for the help.

[baron_von_bootsector]

1 minute ago, khezz said:

Wow a 3.4l, very nice.

I know the RBs are built to rev. I know it will never drive as nice as my auto F6. But I would rather have a 900hp car that I can drive in morning traffic then brag about a piece of paper with 1000hp on it and need 6000rpm just to get the beast going of the lights.

By the sounds of things I have a very limited choice and slight more of this or that won't make much difference. Thanks for the help.

The 3.4 is damn nice but a lot of work when going straight from a 2.6 and trying to keep everything looking semi stock...

To give you an idea of the effort involved with the 1000HP figure - mine pumps out an honest 450kw (just over 600HP) at the treads at 7000 revs. I have a similar fuel system to the one you are planning (A walbro 450 and 2x 044's under the car with a surge tank), ID1300 injectors, Autronic ECU and a twin GTX2867's. I could go to 8000 revs but really given how it drives now the extra stress on the bottom end just isn't worth the bragging rights. The torque is huge,  the power is nice and linear as it comes on steam and the coppermix twin clutch makes it incredibly nice to drive.

It sounds like you are in the same sort of "rather drive it than dyno it" frame of mind as me, good luck with the mods and let us know how you get on with it

[khezz]

I can't imagine owning a car and hate driving it. Will keep my build thread up to date. Had the car painted today. Came out mint.

 

[anthonymcgrath]

Kelford or a set of tomei I reckon will work a treat! That's gonna be a monster build and the 3.4 should give some good low down punch before that tub starts working hard.

Jeez and I'm happy with mine on -5 at 1.2 bar lol (altho it goes back soon for 1.6 and nitrous to help spool lol)

[Piggaz]

Considering the "relatively low" RPM limit here which is 8000RPM, would it need a 270/280/290 degree shaft? A GTX 4294 is no GTX55 or something outrageous.

Considering it's a street car, I'd err on the side of "less is more" here if idle quality and all the rest of the things that make a nice streeter is important.

[khezz]

Considering the "relatively low" RPM limit here which is 8000RPM, would it need a 270/280/290 degree shaft? A GTX 4294 is no GTX55 or something outrageous.
Considering it's a street car, I'd err on the side of "less is more" here if idle quality and all the rest of the things that make a nice streeter is important.

Fare statement.

I am not too worried about idle. If It has to idle at a grand or more to stay happy then so be it. It's not going to be the most "streetable" daily driver but I don't want a dyno/drag queen either. So agreed. Less is more.

I am still a little staggered that we are discussing a 1000hp daily driver like its breakfast news. Not too long ago, that sort of GTR would never be considered streetable. God bless ball bearing twin scroll turbos, E85 fuel and all other things that makes this possible.

[Lithium]

Just to clarify - and sorry if this is kind of OT, when you say "1000hp" I'm assuming you mean at the fly wheel?   A GTX4294R sits in a weird place between being arguably quite a bit too small for 1000hp @ wheels on a Dyno Dynamics, and there being much smaller/more responsive turbos that would go past that power at the crank as well.

I'm assuming that the actual aim is to run to the limit of the GTX4294R?