R33 Rb30 Conversion

[Rolls]

Perhaps the dfelivery of twins would help a GTSt with traction.

Why would twins deliver the power any differently from an appropriately sized single?

[Cubes]

I was under the impression twins offered better response once in the rpm where the turbo's are able to make all their boost. i.e in gear roll ons or corner exit.

All though not exactly the best comparison.

A mates old rb30det gt35r .82. Made all its boost (17psi) around the mid 3000's.

He now has an rb26 with mild cams, mines ecu and a pair of rb2530's, it makes all its boost (15psi) a shade over 4000rpm.

Both make within 10rwkw of each other on similiar boost.

Roll on in second gear at a shade over 4000rpm; the twins get up and go noticably quicker despite the smaller motor. YET they make all their boost later in the rpm.

As I said; not exactly the best comparison.

Twin 2530's with his setup I thought was quite impressive; definitely not laggy or did it have that big turbo feel the gt35r tends to give.

When his rb26 develops the death rattle it will be interesting to see how the 3ltr goes with his setup providing he does go the 3ltr.

[BAMR33]

Nice! that adapter looks the goods.

Secur1ty, I am in the same boat as you. It looks like I will be using my slide hiflow on my RB30 and possibly upgrade later (who am i kidding ofcorse i will bloody upgrade later) as if a measly 330rwhp is enough

I have bought all my parts and will be using:

RB30E series 2 nissan block, rods, pistons and crank. will inspect it and if it is in good condition I am not going to rebuild it as it has fairly low k's

R33 RB25DE head with VCT stock cams, new springs, r33 CAS and all standard R33 bits

standard nissan or cometic HG. new tensioners x 2 and 151 tooth belt

GTR injectors

R32 remapped ECU

Things I will have to figure out...

1. I will have to adapt a top feed fuel rail to an R33 RB25 inlet manifold. this should be doable... I already have the GTR squirters so make do with them.

2. will have to do a bit of figuring out how to get the R32 loom to play with the R33 cas and sensors otherwise I will have to swap the cams to R32 ones Do'h!

3. sort out the VCT head modifications, drill and tap tensioner hole, lower engine mounts.

so its a bit of work and will be the first time i have taken on a project this big. I have changed gearboxes, diffs and brakes, suspension but never pulled an engine apart.

I have a hoist, big garage a spare car and a big garage so all should be sweet!

The aim is to have a responsive 250rwkw package that is reliable with decent torque.

anyone see anything i have missed?

I'd put in a new set of rings at least and oil restrictors in the head.

Must be the week to start on an rb30, I just bought an excellent condition rb30 series 2 block and I'm in the process of buying vct r33 head. Also maybe putting a slide hi-flow on, except the one I have is only the rb25 rear housing

[Scooby]

Why would twins deliver the power any differently from an appropriately sized single?

I think the twin set up gives more flexibility with quicker spool, better response and a more progressive power delivery. From the dyno sheets I've seen the twins are less peaky than a single, which seem to make their power in a narrower band.

Fine from a race car perspective maybe, but for my streeter if I can get a nice 300 rwkw from the R34N1 twins on the 26/30 I'll be happier than running a T04Z etc that gives me 400rwkw but almost doubles the power between 4500 and 6000 rpm.

Show me a big single that performs like the twins and I'd be pretty interested.

[proengines]

Cheers Rockabilly for the nice words, it makes it worth the weeks it took getting everything digitised and making sure it all fits. Thanks for your faith buying it from the other side of the world! Let me know once you have it all up and running.

As for the twin vs single, I did a 25/30 a couple of months ago, a fairly basic engine with forged pistons, rods, mls gasket, std valves with some porting and a pair of 256/264 cams, not using the vvt, just a pair of adjustable gears. The engine is in a 33 GTST running a single 35/40 1.06 rear housing (from memory) on a chinese manifold, Plasmaman plenum, 660cc injectors etc. It makes boost from just under 3000 and pulls like a train. It made 364kw at the wheels a couple of weeks ago when it was being tuned and masses of torque. Any more power would be useless in a 2wd on the road. Personally, if I was starting from scratch I would go single, it's a lot cheaper and simpler to do. Then again, in a GTR everything else is already there for the twins so why not stick with them unless they need to be replaced.

[Adriano]

IMO 99% people put singles on their car to make more power. 65% put a bigger turbo than the power they want to make/end up making, and 10% use these turbos to their full capacity. Have a look at the mafia's power curve. Hes making the most of the turbo, and makes heaps of torque. How many rb25's on here have gt35r's and dont make 350-360rwkw, i think thats the real problem, most people want to see a big 700hp turbo strapped to their motor, doesnt matter if it only makes 500hp because it doesnt have the supporting mods, and the lag makes it feel like a rocket.

[bakker]

can anyone save me the hassle of going through every post on this subject and direct me to an A through Z step by step how to on doing an rb25/30 conversion witha vct n/a head in an r32??. got the N/A 25 motor and a perfect 30 block just want one set of instructions so i can follow em for the build.

[Adriano]

Look in cubes signature, there is a guide, however i recon 20 pages of this thread are the same question as yours.

[Scooby]

It makes boost from just under 3000 and pulls like a train...Personally, if I was starting from scratch I would go single, it's a lot cheaper and simpler to do. Then again, in a GTR everything else is already there for the twins so why not stick with them unless they need to be replaced.

Hi Greg;

Any idea what the power curve looks like? I agree with the fitting advantages of a single but but it's the peaky nature of most singles I don't like.

Why not stick to twins in a GTR 26/30? Not sure if you're a Borat fan but to quote him it 'is pain in my assholes'. Things on that side don't fit well anymore. Heater hoses, bov plumbing, dump pipes (even more fun if you have the long wastegate style), airbox, oil feed and return lines, water lines, AFM plumbing. Only upside is you don't need a PFC/remap... initially.

Cheers

[Cubes]

I guess what Greg is saying is the singles power delivery aids rwd traction more so than the twins; in other words; what the single gives is more than enough for rwd.

The twins that I've seen definitely come up MUCH quicker than the big single when the pedal hits the metal as they say

I'll say it again. The comparison I've seen has a lot of variables; but none the less I really do think twins spin up and begin pushing decent air quicker when the throttle opens.

We will never really know as who in their right mind goes from a twin setup thats making mid 300's atw to a big single that does the same.

[sky30]

I guess what Greg is saying is the singles power delivery aids rwd traction more so than the twins; in other words; what the single gives is more than enough for rwd.

The twins that I've seen definitely come up MUCH quicker than the big single when the pedal hits the metal as they say

I'll say it again. The comparison I've seen has a lot of variables; but none the less I really do think twins spin up and begin pushing decent air quicker when the throttle opens.

We will never really know as who in their right mind goes from a twin setup thats making mid 300's atw to a big single that does the same.

I have always thought of going twins for better response than my GT35, but cant see how twins with the same combined HP rating as a single would boost quicker when they are only driven by 3 cylinders.

I have full boost with my GT35 at 3400rpm, would twins that are combined rated to 700hp boost that early?

What RPM does antonys GTR make full boost?

[Cubes]

Im not sure about others but from what I've seen the big single makes all its boost at an earlier rpm than 2 similiar sized twins.

So thats lag.

Response; once there's enough exhaust gas to bring both the big single and twins up on to lets say 1bar.

Put the foot down; the 2 smaller twins with less inertia are able to spin quicker up to speed and accelerate off. More so noticable in the lower less load gears.

Thats my understanding behind why Nissan went twin parallel turbo's, offer the best response when accelerating out of corners.

[r33_racer]

BIG SINGLE FTW. only cause thats what i run.

Just run water injection pre turbo.....hot side! ie. into the runners. Reduce lag and increase spool.

I believe cubes is right in what hes saying though. however twins equal messy...more pipes...lines....exhausts...intakes...manifolds.

[CEF11E]

Cheers Rockabilly for the nice words, it makes it worth the weeks it took getting everything digitised and making sure it all fits. Thanks for your faith buying it from the other side of the world! Let me know once you have it all up and running.

As for the twin vs single, I did a 25/30 a couple of months ago, a fairly basic engine with forged pistons, rods, mls gasket, std valves with some porting and a pair of 256/264 cams, not using the vvt, just a pair of adjustable gears. The engine is in a 33 GTST running a single 35/40 1.06 rear housing (from memory) on a chinese manifold, Plasmaman plenum, 660cc injectors etc. It makes boost from just under 3000 and pulls like a train. It made 364kw at the wheels a couple of weeks ago when it was being tuned and masses of torque. Any more power would be useless in a 2wd on the road. Personally, if I was starting from scratch I would go single, it's a lot cheaper and simpler to do. Then again, in a GTR everything else is already there for the twins so why not stick with them unless they need to be replaced.

Hi Greg,

I have seen this car at autotech and was there when it was being tuned and yep it has a really meaty power curve and some ridiculous torque figure.

seeing the figures from this car helped me make th 30det decision.

[sky30]

Im not sure about others but from what I've seen the big single makes all its boost at an earlier rpm than 2 similiar sized twins.

So thats lag.

Response; once there's enough exhaust gas to bring both the big single and twins up on to lets say 1bar.

Put the foot down; the 2 smaller twins with less inertia are able to spin quicker up to speed and accelerate off. More so noticable in the lower less load gears.

Thats my understanding behind why Nissan went twin parallel turbo's, offer the best response when accelerating out of corners.

I see what your saying in theory, but does it happen in the real world>? Im very interested to see some results of twin RB30det.

What RPM does Antonys start building boost, and what RPM does his make full??

[Cubes]

Antony's starts making a little boost around 2000rpm and then makes ~1bar a shade over 4000rpm; it kicks around 4500rpm.

Even though his isn't an rb30dett I think its slightly comparable.

His sitting in second gear at 4000rpm and then floor it gets up and goes a hell of a lot quicker than the big single gt35r .82 ever did.

It does lag slightly more when accelerating from a low rpm and has stuff all off boost but once its up in the rev's it gets up and goes in the lower gears than his old gt35r ever did. Comparing dyno runs the rb26 has much less mid range and 10rwkw less top end which is noticable once it gets going in 3rd+ gear.

When the rev's are up the turbo's feel instant as soon as you nail it; the gt35r never really had that feel even though it was hanging off a larger motor.

[shanef]

did the 2 motors have the same comp ratio? same cams? same headwork? same style of manifold? same exhaust?

if not then u cant/shouldnt really compare them, even u know that one

[Scooby]

...cant see how twins with the same combined HP rating as a single would boost quicker when they are only driven by 3 cylinders.

smaller turbos don't need as much gas to move them and therefore spin sooner / boost at lower rpm. same situation as a single; smaller will boost quicker but not have as much top end. using two instead of one provides quick boost and good combined power.

[Cubes]

did the 2 motors have the same comp ratio? same cams? same headwork? same style of manifold? same exhaust?

if not then u cant/shouldnt really compare them, even u know that one

Shane, have a read above at my previous posts. You'll see I said its not the best comparison.

Regardless, twins offer better turbo response due to less inertia.

Providing there is sufficient exhaust gas smaller turbo's are able to go from idle rpm to 80,000rpm quicker than a wheel 2x its size.

Why would Nissan throw ceramic turbines on their turbo's? To lower inertia and provide better response from the turbo.

[Adriano]

But a turbo with double the hp ability doesn't have double the rotating dimensions, or double the rotating inertia