Built rb20 or stock rb25?

[Skym]

I have a hybrid RB20 stock turbo on my car and engine is very responsive (with transient response) vs stock turbo (same feeling as with stock turbo, just feels alot stronger, quicker when car accelerates). Boost response is slightly laggier than stock, as it starts to reach 0 on boost gauge at 2500rpm (can keep turbo off boost for better fuel economy), full boost at around 3500rpm and peak hp at 7500rpm (produces around 270hp at engine with 12psi or basically 20hp more at same boost level as stock RB20 turbo with intake, 3" exhaust from stock dumppipe, bov mods, stock ECU tune). With intake, 3" exhaust from stock dumppipe, BOV mods, stock ECU tune, stock RB20 turbo it should produce 250hp at engine (varies from car to car due to internal wastegate being different on each car).

Hybrid RB20DET stock turbo should be capable of 350hp at 1bar (20hp more than stock turbo at same boost level with boost up mods) on pump gas and around 400hp with E85 at 1bar (those hp numbers are at engine and with boost up mods like Z32 MAF+Z32 MAF plug, retuned stock ECU, injectors, fuelpump, FMIC, full 3" exhaust from turbo, boost controller, upgraded clutch).

Hybrid RB25DET turbo has the bigger compressor wheel, so produces more hp at same boost level as hybrid RB20 stock turbo or basically can run lower boost level for same amount of hp. On RB25DET it's been known to produce over 400hp at engine at 1bar with Link ECU (map sensor, etc), HDI FMIC, Subaru? injectors, aftermarket fuelpump, intake, exhaust mods, clutch upgrade. But it is also known to surge unless drive to prevent it from surging (due small A/R exhaust housing with bigger compressor wheel). You could fit bigger A/R exhaust housing from VG30ET turbo to solve it, but might lose response (might not on RB25DET due to RB25DET produces more exhaust gas).

[magular]

Well Skym, I love how detailed and knowledgable you are with all this stuff, including the fact that this is rb20 stuff not 26 lol.
It's nice hear some actual numbers not just the top off your head, you've actually tested these things. Anyways. I guess this thread is built 20 or stock 25.... Seems like 20 is much more tuner friendly and ecu and transmission match up and motor weight.... Rb20 seems more then enough.

[supersayianjim]

well gents and gals. iam going rb25(forgive me). engine is here and swap has commenced.

[Skym]

Well Skym, I love how detailed and knowledgable you are with all this stuff, including the fact that this is rb20 stuff not 26 lol.

Don't think I'm that knowledgeable, but thank you for your kind words.

It's nice hear some actual numbers not just the top off your head, you've actually tested these things. Anyways. I guess this thread is built 20 or stock 25.... Seems like 20 is much more tuner friendly and ecu and transmission match up and motor weight.... Rb20 seems more then enough.

I haven't tested the E85, but in dyno links below there is a E85 dynochart showing 50hp gain at same boost level. Also some run E85 on track cars (with GM ethonal sensor, Link ECU on one car) and have better turbo spool, more hp than turbo is rated at on pump gas.

If want actual numbers when boosted up to 17psi, dynochart, in link below is a high flow RB20 turbo (known as a hybrid RB20 turbo, but some call it a high flow turbo. High flowing a turbo is polishing housings, backcutting blade, etc and hybrid turbo is new CHRA, new compressor, new exhaust wheels and machined stock housings to suit bigger wheels) and note the power at wheels (around 366hp at engine, 17psi with pump gas) -

http://www.skylinesaustralia.com/forums/topic/103095-rb20-turbo-upgrade-all-dyno-results/page__st__340

But that's with FMIC. The fullboost I mentioned above at 270hp is with stock SMIC. Also I think has ported wastegate hole on back of turbo, new wastegate flap, as stock is too small.

He had problems with it boost spiking (due to small wastegate hole on back of turbo), as shown in link below -

http://www.skylinesaustralia.com/forums/topic/103095-rb20-turbo-upgrade-all-dyno-results/page__st__320

Same boost spike problem at higher rpm I encountered on my car with hybrid RB20 turbo (have to fix it).

[supersayianjim]

bump for a good thread!!!

[krystalized_jdm]

For those curious, I decided to stick w/ rb20 w/ a few bolt ons and possibly nistune in the near future.

[S13Jordie]

For those curious, I decided to stick w/ rb20 w/ a few bolt ons and possibly nistune in the near future.

I chose the same thing. forward facing plenum along with gtr injectors and a different turbo. Going to remove as much rotating mass from the motor as possible ( pulleys and E fans) to help free up some extra ponies.

[supersayianjim]

cheers guys. iam getting a cash infusion and my project will continue next week. using the rb20 trans but will source a z31 trans for backup, and also running a z32 nistune ecu.

[DatsunZ31]

cheers guys. iam getting a cash infusion and my project will continue next week. using the rb20 trans but will source a z31 trans for backup, and also running a z32 nistune ecu.

run one from a S13 or S14 71C the N/A 71c's transmissions from the Z31's are garbage.

[supersayianjim]

so i hear. i need to source out a late model (like an 88-89) z31 turbo model. apparently they have the same beefy internals like a z32tt does.