Gt3540r Iw On Its Way R33 Gtst

[fEkuaR]

Your really pushing a standard bottom end at 300+rwkw. I hope your tuner knows what they are doing if you want it to last at that power level.

[bazr33]

What would be the cheapest way to strengthen the bottom end and be reliable for my setup

would gtr rods, Forged pistons do the trick?? i was tryin to stay clear from opening up the engine but hey, if i want the power and dont want it to blow up then i have to do it.

im more worried about how much it will cost to get someone to do it.

any suggestions and what parts to get will be good.

thanks

[LTHLRB]

as long as its healthy u wont have a problem, just make sure u have a good tuner by your side mate.

but shot peened gtr rods and forgies will be a sweet package.

[Cubes]

The blokes here in Adelaide that have reliably pushed 300rwkw+ on the stock rb25 have all dropped the comp ratio via a thicker headgasket to 8-8.5:1.

[fEkuaR]

A headgasket is good insurance on your bottom end. Will have a slight adverse affect on your response however. Id suggest spending the money to get rods and pistons. Its good insurance and you will feel alot better knowing that its done everytime you put your foot down.

[Cubes]

Well you can't have your cake and eat it.. Most rb25 rebuilds drop the comp ratio down to 8-8.5ish with forged pistons anyway.

The rb25 rods are underestimated. Keep rev's under 7500ish rpm and there's no need for forged. They will hold what ever the gt3540 can make. GT40+ and definitely rods.

[fEkuaR]

  Cubes said:

Well you can't have your cake and eat it.. Most rb25 rebuilds drop the comp ratio down to 8-8.5ish with forged pistons anyway.

The rb25 rods are underestimated. Keep rev's under 7500rpm and there's no need to change.

I dont disagree with you at all, though personally if i was going to really push my engine to 300+ id just want that extra confidence that forged internals would give. There is no dout that this car is going to have to rev to make power.

[Devils_Advocate21]

Ummm CP flat top pistons up the comp ratio dont they

[LTHLRB]

they make all turbo pistons that are forged a lower compression ratio because obviously your going to pump it with boost and power.

But for 8s and stuff they up the ratio.

also a metal headgasket will drop it further, so yeah safer boost.

[HR31_RB20DET]

If going forged internals go speak to Brad about a package of spool rods and CP pistons, he does a good deal last time I checked.

  bazr33 said:

What would be the cheapest way to strengthen the bottom end and be reliable for my setup

would gtr rods, Forged pistons do the trick?? i was tryin to stay clear from opening up the engine but hey, if i want the power and dont want it to blow up then i have to do it.

im more worried about how much it will cost to get someone to do it.

any suggestions and what parts to get will be good.

thanks

[Cubes]

  fEkuaR said:

I dont disagree with you at all, though personally if i was going to really push my engine to 300+ id just want that extra confidence that forged internals would give. There is no dout that this car is going to have to rev to make power.

Don't take my post the wrong way... Wasn't indended to come across as a disagreement.

You are right.. A gt3540 on a rb25 you want rev's as it won't really get moving until 4500-5000rpm behind a 5speed.

To make the most of the turbo you really want to spin it to 8000rpm and to do that reliabily as with all the rb's it requires some work with rods/pistons and oil.

[bazr33]

sounds like i might have to go for the rods and pistons option.

Does anyone know how much it would cost to get these fitted????

i already have bought a 1.5mm metal layered tomei head gasket.

Does anyone know if the nismo rb26rods fit into a rb25???

Yeah might have to speak to Brad about the pistons and rods.

Thanks

[fEkuaR]

It would be a good idea to get oversized pistons 20thou or whatever is recommended to you by your workshop. Have your block taken out to suit so its all nice and fresh. Rb26 rods will be fine for the 25 they are compatible.

[fEkuaR]

  Cubes said:

Don't take my post the wrong way... Wasn't indended to come across as a disagreement.

You are right.. A gt3540 on a rb25 you want rev's as it won't really get moving until 4500-5000rpm behind a 5speed.

To make the most of the turbo you really want to spin it to 8000rpm and to do that reliabily as with all the rb's it requires some work with rods/pistons and oil.

Agreed it would be better if he could get those revs up to around 8000rpm he will make more use of the set up that way. Aslong as he takes your advice on the oil aswell he should be able to build a reliable engine up to making the most of his gear.

Edited April 28, 2007 by fEkuaR

[bazr33]

kool, thanks for all the advice, and now knowing what im going to do.

Now last questions is for the ppl who have had pistons/rods upgraded, how much was it to have these put into the engine???

[VLT025]

How much are these ex XR6T turbos going for? Could be a cool low cost option for some big power...

I know that the VL/RB30ET brigade love them

[GTRNUR]

I've seen an RB25Det with the GT3540 (0.82 housing)on it run over 400kw to the tyres. Boost was around 32lb i think. Aries pistons and crower rods, stock cams, and an un-ported head. It also had a metal head gasket and ARPM head studs. Crank was stock.

It barely got boost in 1st gear, in 2nd it came on like a switch at 5000 rpm with instant revs past 7500 and a hail of wheel spin and tyre smoke, same deal in 3rd and 4th.

3lt bottom end is the way to go, but if you cant afford that, doing pistons and rods so you can safely rev it past 7500 reliably, and maybe a GTR crank is the way to go. There is one in the parts section that has the JUN crank collar fitted for the oil pump thats reasonably cheap. Every bit of displacement increase you can get will help reduce lag a little.

Also, keep in mind oil restrictors for your head or you'll end up with no oil in the sump if you rev above 7500. Or you can run an external oil return to the sump.

See how one mod leads to another... and another.. $$$

Good luck with it.

Ian

Edited April 28, 2007 by Vspec R33

[bazr33]

well i bought this turbo for 1500 came with custom split dump to cat, with exhaust manifold and oil line.

you can get them cheaper but couldnt be bothered looking around anymore.

So yeah mods that i'll do is

Nismo rb26 rods if they fit.

Either CP Pistons or ACL Pistons.

I'll look into rb26 crank, but i have heard that they either dont fit or have to change something else to fit it.

Port and polish head with poncams and valve springs.

and yeah definately get oil restrictors for the head.

So yeah looks like its going to be a bit costly but yeah im in no hurry to do this, so i'll get stuff one by one.

[joe blo]

the spool forged rb25 rods r 675 with bolts ready to drop in. im not sure how much the gtr rods wud b worth after shotpeening but id say thered b stuff all difference and the forged rods wud b stronger. so get them.

[BHDave]

If you are going to all this expense to get the most out of a cheap turbo, wouldn't you be better off binning it and getting a turbo that better suited to the stock engine? 3071 or 3076 would be the obvious choices, one will make just under 300 on reasonable boost, one will make a bit over.