Gtr 4 Inch Exhaust?

[Griffin]

I have a fully built rb26 with -10 turbos with greddy front pipes, 4 inch cat and hks silent power cat back. Is it worth going to 4 inch from cat back? What gain should i get? Will i need a retune?

Ive seen some replies about 4 inch exhausts but searching didnt really help.

[R31Nismoid]

-10 are 450rwkw+

So yes, 4 inch is needed with large front pipes too.

Also a 4 inch cat will be causing restriction also.

[Griffin]

should i step up to 4 inch from the front pipe into a 4 inch cat body then 4 inch from there on?

[OMGGTR]

Nis do u need bigger? U said 4" cat is a restriction? Also u got any dyno sheets with the -10s ?

[R31Nismoid]

-10s are the same as GT-RS's - 450rwkw+

If 2530's will make 400-420rwkw, and the GT-RS are bigger again... Then pretty easy to set expectation when there are a few RS results making some BIG numbers in the dyno threads.

4" CAT will be a restriction on a turbo setup that large. Have a look @ any CAT, it can't NOT be a restriction and hence if you wish to run one you'll need a larger one for good performance.

Realistically though, for best performance with those turbos, only option is a 4" straight pipe - no CAT.

Remember RS's are internally gated so you need a lot of flow.

Realistically RS's are not really a great turbo anyway (hoping to see Piggaz comparo soon of -10s vs -5s).. That will hold a very interesting story. Same as Gav from WA, he picked up something like 1200rpm extra response doing the same step back in turbo size... Such a boost in the mid range is just insane for a street car

[Griffin]

The engine is fairly responsive considering its not a stroker due to being fully race balanced and light flywheel.

This is with 700cc injectors maxed out. Engine is built for 30 psi. If e85 becomes available Should i fit bigger injectors , 4 inch exhaust and a tune for e85? It has a power fc djetro. What sort of power should i expect?

Edited June 14, 2011 by Griffin

[R31Nismoid]

come on, you can't say coming on 20psi @ 5000rpm is responsive!

700cc injectors are already too small for -10s... You need ~1000cc to flow the power they are capable of on PUMP.

Add in E85 - you need ID2000 (2000cc), and a good fuel system to back it up.

[Griffin]

Do you mean it takes 5000rpm to make 20psi? cant say ive noticed. So u reckon just get bigger injectors and an exhaust to make the most of what i have? How much boost should i run considering the -10s and a built engine?

[R31Nismoid]

I mean you won't have 20psi before 5000rpm with -10s on a 2.6ltr

That can't really be put in the same sentence as responsive (Wait till Piggaz see's this thread lol)

At a minimum you'll need injectors, exhaust.

I'd also say to make the most you'll need super cams, heaps of head-work, bigger valves - basic terms - the works, and then some.

You'd be aiming for at least 25psi as a starting point as well. Depends on if the motor will take that however with timing in it. Totally depends on how it was built. Might find its not even possible.

All of this assumes you have a expensive bottom end too. Just your normal standard rebuild really ain't going to take that, especially the RPM part. You would need to spin to at least 8500-9000 to get use outta the power range on the 2.6

[Piggaz]

Oh god no. RS's in a 2.6L would have to be the worst low mount setup out there. They are terrible on a (my) 2.8. Sure you might make a nice big fat number starting with a 4 but you are going to be belted by a well balanced car with little baby -7's or -9's.

On the pommie forum they seem to love the '2.8 + RS' setup. It is not the setup to have. On a dirty thirty they are not bad... But they are not great either. Once again te next size down in turbo size would make for a much quicker car. Yes you might loose a bee's dick in top end (20 HP) but the midrange will more than make up for it.

It's up to you but area under the curve wins!

[Nee-san]

Oh god no. RS's in a 2.6L would have to be the worst low mount setup out there. They are terrible on a (my) 2.8. Sure you might make a nice big fat number starting with a 4 but you are going to be belted by a well balanced car with little baby -7's or -9's.

On the pommie forum they seem to love the '2.8 + RS' setup. It is not the setup to have. On a dirty thirty they are not bad... But they are not great either. Once again te next size down in turbo size would make for a much quicker car. Yes you might loose a bee's dick in top end (20 HP) but the midrange will more than make up for it.

It's up to you but area under the curve wins!

Pretty much spot on, I would not put them on a 2.6 litre, 2.8 or 3.0 is a different story that's probably for another thread though.

Piggaz mate, have your Midori dumps shown up yet ?

What's the goss ?

[sucram]

4'' body cat is too small for a 4'' system

Usually you will find a 4'' body on a 3'' cat or a 3'' cat that has been necked to 3.5''

[Piggaz]

Pretty much spot on, I would not put them on a 2.6 litre, 2.8 or 3.0 is a different story that's probably for another thread though.

Piggaz mate, have your Midori dumps shown up yet ?

What's the goss ?

Dumps are here, 5's are in their boxes in my room. Just waiting on my Nismo cooler to turn up. Also should have the crank timing trigger (will explain later) to stop this timing floating around issue!

Anyway, back on topic. Get a cat that is 4 inch in and out with the biggest body you can find!

[N1GTR]

This thread delivers, full race balance style.

As someone who's had RS's on an 87mm 3L they STILL sucked compared to 5's.

They weren't as bad on a 3L as everyone makes out they were but it's not even fair once the 5's are fitted to the same engine.

The graph for this will look like a cliff, nothing nothing nothing nothing then a sharp rise on the right hand side.

It will be great if you can always keep the rpm up, but for example if you're in 3rd at say 60kmh and go full throttle it's going to be painfully slow to get any meaningful power out of it and if it's a street car you may think that's super quick but relatively speaking compared to others it will get left for dead.

Good luck with it however it ends up

[sucram]

might be interesting to see what .48 housings would do to -10's

Wont fix it properly but might be a band aid for some

[Piggaz]

might be interesting to see what .48 housings would do to -10's

Wont fix it properly but might be a band aid for some

Smaller housings on the front or rear?

[Piggaz]

might be interesting to see what .48 housings would do to -10's

Wont fix it properly but might be a band aid for some

[R31Nismoid]

might be interesting to see what .48 housings would do to -10's

Wont fix it properly but might be a band aid for some

Assuming you mean rear... That'll just make them even more surge prone pushing more air around earlier

Its like people that put a .63 rear on a 700hp GT35 - madmans business.

If you pulling the turbos off to swap housings, you might as well just put on better turbos overall.

[Piggaz]

If anything they need a bigger rear, it won't help the lag problem but it will go along way to stop them sounding like Thomas the tank engine!

[Piggaz]

Ash. Can you delete my double posts.. IPhone rubbish. Sorry mate.