Rb25 To Rb30...

[cactus]

Hey guys,

I am currently running a built RB25 with GT3082R (.82r), standard head, all supporting mods and making roughly 360rwhp @ 18psi thrugh a KEAS built auto with 4200rpm stall. A lot of people tell me the reason the power is so low is because of the auto, which I assume is true.

Was planning on selling the engine, however someone has suggested I go the 30 bottom end. I dont want to go spending money without asking a few questions. Really, my question is whether there is a noticeable difference with torque going from the RB30 to the 25. Down at the drags, I struggle to get a 60 foot below 2.4 seconds even with the big stall (I still only see around 7psi if that on the line). I am hoping going to the larger capacity I might see a little more boost and RPM a little higher...

Also, is there much to gain HP wise?

Cheers,

Matt.

[R31Nismoid]

Power is about right - i wouldn't say low at all.

However if you are only getting 2.4 60ft - Simply going 3ltr won't fix that.

There is clearly something wrong with the convetor/lockup or some other shortfall in the setup

Also how much does the HQ actually weigh? (im @ 1480kgs)

What diff gears are you running?

What type of auto and gearing is going on there?

I could manage to get 2.1-2.2 60ft on 225/60/16 street tyres with 370rwkw in manual HR31 coupe/1480kg's & RB25.

ET was only 12.1 lol... over powered and no traction isn't really productive when you gotta back off a couple times

HP wise - no real gain. You'll just make the same power on less boost perhaps

[cactus]

Power is about right - i wouldn't say low at all.

However if you are only getting 2.4 60ft - Simply going 3ltr won't fix that.

There is clearly something wrong with the convetor/lockup or some other shortfall in the setup

Also how much does the HQ actually weigh? (im @ 1480kgs)

What diff gears are you running?

What type of auto and gearing is going on there?

I could manage to get 2.1-2.2 60ft on 225/60/16 street tyres with 370rwkw in manual HR31 coupe/1480kg's & RB25.

ET was only 12.1 lol... over powered and no traction isn't really productive when you gotta back off a couple times

HP wise - no real gain. You'll just make the same power on less boost perhaps

THe car weighs 1700kg with me in it ...

I run Borg Warner with LSD - 4.11s

Auto is the standard 4/5spd RE401A I believe it is, with KEAS full manual valve body, MV auto hi-stall and box was rebuilt by KEAS with upgraded everything

Yeah, I thought it might be a stall issue also, but believe maybe its just the weight.

When I ran my best time, it was a 12.6 @ 113mph with 2.3 60 foot... on street tyres so was a little stiff on traction but not too bad as it has about 200kgs of gear in the boot.

Was hoping the 3Lt would make a huge improvement

[R31Nismoid]

So 1700kg's + the 200kg = 1900?

Or did you mean 1700kg is the absolute total?

To note - if you had traction issues with 2.3 60ft, going 3ltr won't make it any easier. If anything more torque sooner will give you more issues.

Considering i could manage a 1.9 60ft with less power (same weight, @ basically 1500kg's).

Im not sure 0.4 extra is right for only 200kg's (if its 400kgs then thats about right i would imagine with my powers of guestamation)

[cactus]

So 1700kg's + the 200kg = 1900?

Or did you mean 1700kg is the absolute total?

To note - if you had traction issues with 2.3 60ft, going 3ltr won't make it any easier. If anything more torque sooner will give you more issues.

Considering i could manage a 1.9 60ft with less power (same weight, @ basically 1500kg's).

Im not sure 0.4 extra is right for only 200kg's (if its 400kgs then thats about right i would imagine with my powers of guestamation)

No sorry, 1700KG total with me in the car. I was just mentioning the fact that a minimum of 200kgs sits in the boot

I will go slicks if it is a major issue. I consistently run between 2.2 and 2.4 at the moment, no matter how I try get the car off the line.

[MBS206]

Power is about right - i wouldn't say low at all.

However if you are only getting 2.4 60ft - Simply going 3ltr won't fix that.

There is clearly something wrong with the convetor/lockup or some other shortfall in the setup

Also how much does the HQ actually weigh? (im @ 1480kgs)

What diff gears are you running?

What type of auto and gearing is going on there?

I could manage to get 2.1-2.2 60ft on 225/60/16 street tyres with 370rwkw in manual HR31 coupe/1480kg's & RB25.

ET was only 12.1 lol... over powered and no traction isn't really productive when you gotta back off a couple times

HP wise - no real gain. You'll just make the same power on less boost perhaps

There is no huge HP gain no...

It's the shit loads of torque earlier on in the rev range that make it faster.

Hence, same RPM, same power, less boost...

So keep the boost up the same, same RPM, and low and behold, MORE POWER!

The 3Lt picks up roughly 15 - 20% more torque at the same boost levels. (But you have to be aware, there is DEFINITELY more air flow)

250RWKWs and traction issues at 130KM/h... That's what the 3L does...

[R31Nismoid]

Umm... well duh, but you can make more power with more boost into the current setup - whats the point?

The question was asked - will there be much gain in HP, the answer is no - regardless or how you want to approach it.

If he has a massing stall, the 60ft should be lower than that. I still think there is more too it. I'd ring KEAS ans get their thoughts on the matter.

Although its gone from 2.4 to 2.2, which is 0.4 of a sec at the other end (generally speaking)... so 2.2 is getting lower but still not the best especially if you are leaving the line with boost read and loaded as opposed to a rev and a dump

[bubba]

No transbrake?

[cactus]

No transbrake?

Nope... Not suited to the valve body.

[MBS206]

Umm... well duh, but you can make more power with more boost into the current setup - whats the point?

The question was asked - will there be much gain in HP, the answer is no - regardless or how you want to approach it.

If he has a massing stall, the 60ft should be lower than that. I still think there is more too it. I'd ring KEAS ans get their thoughts on the matter.

Although its gone from 2.4 to 2.2, which is 0.4 of a sec at the other end (generally speaking)... so 2.2 is getting lower but still not the best especially if you are leaving the line with boost read and loaded as opposed to a rev and a dump

Bringing boost on earlier, and quicker, matched with he has no transbrake, might be making 7PSi on the line with the RB25 at X power, but the RB30 should push boost up a touch more, and be making alot more torque = better off the line if it'll hook up...

Yep, it'll make the car a shit load quick off the mark then the 25, so long as grip is available...

If he can't get full boost up in the 25 sitting on the line, then more boost won't help it launch quicker, just top end.

Either displacement, or nitrous is needed basically...

[unique1]

hey matt, if your interested in comparing 3l torque with a gt3076r (not far off your turbo size really) i can take you for a drive, its also in a 1700kg car (stagea) so same weight too. Its only making around 320hp at moment but the torque difference from the rb26 i had before is crazy, the thing drives around effortless under 2000rpm unlike the 26. I Checked today and its making 16psi (current boost setting) at 2900 - 3000rpm on the road in 3rd or 4th gear.

Ive spoke to you a few times in the past i had the jun 2.7l in my car previously and tuned by Mick also if you happen to remember.

if your keen send me a pm

Edited September 16, 2009 by unique1