Rb20 Dett S13 Conversion

[GTReality]

Hi Guys'n'Gals (not sure if this is the right forum, moderators please move if not)

I am in the process of putting an RB20 DET into an my S13 and, as I also have an R32 GTR which is currently being dry sumped by Dazmo, one of the true genltemen in our sport, I thought I would install two factory standard rb26 turbos onto the RB20 rather than going to a high mount. I am getting steamer pipe manifolds made as two of the head/manifold studs didn't line up with the RB26 manifold. Would have used the RB26 plenum as well and triple throttle bodies but the intake venturies on the RB20 are tapered and would not allow any flow increase from having extra throttle bodies so went with an aftermarket plenum and 85mm throttle body. Also went with MAP sensing rather than AFMs.

The car will have two tunes in its Microtec LT12, one for me to do circuit work with a rear wheel drive car and one for my son to learn drifting. I am aiming for about 300rwhp and will eventually swap the Garret 2860-7 turrbos from my GTR with -5s and put the -7s into the S13. I am not sure how laggy the S13 will be for circuit work, should be fine for driftin. Have considered using an exhaust cam off a non turbo RB20 which has a slightly higher lift or going to an after market cam with a few degree longer opening (if that is the correct terminoligy) to increase the exhaust gasses to the turbos.

I would really appreciate any constructive Tips or Traps to look out for with this build from anyone who has done this type of conversion before.

Thanks

Pete

PS. Lookout for my R32 once Dazmo has finished with it. Can't say I will be able to to get to 'Holy Grail' status at Willowbank but I bet Darren will.

[R31Nismoid]

someone here did GTR turbo's onto a 20 a while ago... there was nothing below 4500-5000rpm from memory, it'll be a very peaky setup.

More than it should be anyway... then you've added a larger plenum and TB so it could be a little bit nastier again inbetween gear changes.

Someone here will remember who did it... was a thread about it actually.

[Cartman]

someone here did GTR turbo's onto a 20 a while ago... there was nothing below 4500-5000rpm from memory, it'll be a very peaky setup.

More than it should be anyway... then you've added a larger plenum and TB so it could be a little bit nastier again inbetween gear changes.

Someone here will remember who did it... was a thread about it actually.

theres never anything below 4g on an rb20 anyway unless it has stock turbo. 

[STATUS]

You dont need different tunes, its a common misconception even more relevant with a microtech as it has the most basic calculations to determine mapping, the way an engine pulls through the mapping will be no different between drifting or circuit. One tune will do. Having done a few rb conversions (our current one attached (430rwkw)) i must admit they are a dog to circuit, they require allot of work just to get back to where you were with the SR20. Im a big fan of RB20's but in a s13 they offer to much weight over the front axle centerline and have poor low end performance a good SR20 will always be a better proposition. We run a RB26 in our current car and the work to get it to handle like it did with a 300rwkw SR20 was quite astounding and even then it is still compromise. Those who say a RB powered S13 handle well unfortunately must have never experienced "decent" handling

The twin setup would be ultra laggy and pretty bad for drifting especially a beginner (a beginner needs power on demand to make up for small mistakes) i reckon a realistic boost peak at around 5000-5300rpm and you would need to up the limiter to about 8500 and up just to keep a decent power band that is useable.

If your dead set on the rb20 then look at a TD06SL2-20g (i can now source them internally gated) it is probably the best all round turbo kit we have seen or used on the rb20 (with minor mods) again see attached

[R31Nismoid]

theres never anything below 4g on an rb20 anyway unless it has stock turbo. 

Ye, but for the power you get, the lag is excessive.

[Cartman]

Ye, but for the power you get, the lag is excessive.

that is rb20 nature. only turbos that really do perform very well on them are the td06's and 2530's, but even for the 2530 they are laggy

[R31Nismoid]

Oh ye i appreciate no turbo is "responsive" on the ole RB20

What i mean is the GTR twins, plus larger plenum, plus single TB and so on... it's going to be REALLY bad for the power that it will make.

I would be surprised if there is anything below 5000rpm. A 2530 would do a better job and give you at least 500rpm extra, and a nicer throttle response in between gears and so on.

5000rpm before anything starts for a peak of 240rwkw (GTR turbos) is not really at all productive. You'd be lucky to be making 200rwkw @ 6000rpm

[Roy]

When the RB26 cops a 2.8L crank then the lil twin turbo will love the 2.6L crank I know i sometimes think about going -7s on an RB24...but manifolding, cost of two turbos and complexity/packaging means i like singles. But done properly it cant be any worse then running a big single. Can it?