Rb30 Power Delivery, Should It Be Better? How?

[Black_R33]

Engine Specs-

RB30/25 VVT/forgies/prepped STD rods/bearings from KFC (ha!)

FMIC/3" exhaust/no cat/45mm Ext gate

PFC/Z32 afm/550cc inj/big pump reg

STD cams/STD head

GT35 .82 exhaust/X-Force Stainless High Mount Manifold

OK, it’s had two run in tunes and now had a hard tune after 3000Klms. It makes around 300rwkw @ 5500rpm on 17psi, BUT, any more boost than that is a waste-it wont make more power. More importantly it needs to get to at least 3800rpm before it makes good torque. That equates to 1700 RPM of good power to work with.......to me that's a narrow power range for a street engine. Although not exactly the same, my 02 WRX STi has a similar narrow power band and it's a pig in traffic! When building this I new it was not going to be a high revving thing like a 26, but I was looking forward to the torque monster the bigger 3L was meant to be. Am I expecting too much or do I need to keep developing the thing and start changing cams or maybe even the turbo? For the 3L , I thought the .82 ex was a great match for some low rpm hussle. The tuner is quite experienced with RB's and the timing map and AFR's looks pretty good. His first thought was that there might be some restriction in the exhaust side of things.... but in the mean time till we do more testing....

ANY IDEA"S GENTLEMEN?

Dyno attached for your perusal.....

[R31Nismoid]

You should have 3.5-->4" on there.

3" wont cut the mustard at those power levels.

With the 3ltr also, your gonna need cams. You gotta get the air flowing around with the big 3ltr

[paulr33]

its almost like the turbo combo is too big

[SilverECR33]

its interesting how the torque starts to drop off at 2.2k, have you seen any other vlt dyno sheets to compare, maybe with the T03 on it.

If my net wasnt so slow capped atm, id bother loading some of the Hybrid dyno results nice figure 300rwkw ftw!

[SilverECR33]

its almost like the turbo combo is too big

I was thinking of saying the same thing, but i deleted it lol.

yea cause my bro's vlt, torque dont drop off till probably after 3k and thats with a T03.

[rb26s13]

so your only revving it to 5500?

[SilverECR33]

Cams? duration Lobe height. Intake Vs exhaust.

If you have retained the RB30 stroke, wouldnt you need more duration and lobe height than what the standard Rb25 cams has? as the Rb25 stroke is shorter right? and could be closing too early.

This is all very intersting to me cause im just doin an rb30 build for my rb25 now.

[R31Nismoid]

I was thinking of saying the same thing, but i deleted it lol.

yea cause my bro's vlt, torque dont drop off till probably after 3k and thats with a T03.

Nah, for a 25/30, the GT35 in the .82 IMO is the best suited turbo if your chasing a bit of power.

And the power should hold out to 6500-7000rpm pretty easily.

Definately a restriction somewhere

[Butler]

the turbo is too big for the motor but yet it is restricting power!! Weirdest statment ever! The GT35 would be sweet on an rb30. Stuff some cams into it and a good zorst and u should be fine.

[Forged]

cams alone should see 5-10% more rwkw. and try at least 3.5inch exhaust.

[Cubes]

Its not the cams its not the exhaust restriction.

Its the std plenum. Dropping an aftermarket plenum on it and touching nothing else (bar the tune) and peak power will raise up close to 7000rpm and power will hold well to 7500rpm.

Drop some cams in to it and power will hold until ~8000rpm.

Drop cams in it with the std plenum and peak power will still be made in the same approx 5500RPM but the turbo will spool slightly earlier. So a waste of time and $$.

I believe the GT35r .82 is a touch too big for a street rb30det that doesn't rev and make good power to at least 7000rpm.

If you want to stick with the std penum don't go any bigger than the GT30r .82.

GET A PLENUM ON IT!!!!

I'm not speculating or guessing, I've seen it with my eyes on the dyno and then felt the power delivery before and after.

Back to back on the dyno run the plenum made a huge difference to the average usable power when running the GT35r .82 on the rb30det..

I can't comment on a plazman plenum that retains the standard runners as the plenum used on my mates rb30det was a GTR/Greedy style setup. i.e short runners. It lost no off boost power (it actually appears to have picked up a touch) and returns the same fuel economy.

Then work out why its not making any more power. It may be springs, it may be the exhaust manifold.

What occurs? You dial in more boost and det levels go crazy or does it simply flatten off and not make any more power?

[r33_racer]

We have greddy plenum and tomei poncams...with a gt30 .82ar power kept climbing upto 8500rpm. Will find out when it gets tuned soon with the gt35 .82ar how it goes. With the gt30 we were seeing full boost by 3300rpm which was 1.5bar with a 6boost manifold. With the crappy chinese s/s manifold full boost was seen around 3600rpm and was 1bar.

Id put money on what cubes is saying with the inlet manifold restricting it up high. I reckon they have wound the boost up, and the power increase has been very marginal and not worth it for the knock increase?

[Cubes]

Ahh ok so you run a gt30 .82 with the old setup and cracked 300rwkw?

I was under the impression you previously ran a gt35r. nice.

Hows the new motor coming along?

[DennisRB30]

I just put a used XR6 GT35 1.06 rear on my 2JZ powered R31 with a $200 ebay manifold. The 2JZ has the same bore and stroke to a RB30 and with the twin cam head should be quite a similar engine response and power curve wise. 2JZ's plenum's are not restrictive so that would probably be the major difference.

My engine is stock, with stock ECU and stock auto trans etc, it has a 3.5" dump and 80mm exhaust with ebay 100mm cooler.

I am yet to put it on a dyno but it feels a lot stronger at 14psi than my old stock twin setup did at 20psi, which was dynoed at 241rwkw at 15psi. I can get 1 bar of boost up by 3500rpm in second gear, so its quite responsive given that it has the larger rear housing. Guys on the supra forums are getting 500rwhp with this turbo, some even with the .82 rear.

I have no idea what RB30DETs should be putting out but that gives you a basis for response and power comparison on a similar spec engine. Maybe Cubes is right about the plenum?

Edited January 22, 2007 by DennisRB30

[Cubes]

Auto's make a huge difference to spool.

Another mate rb_man has an XR6t turbo (.5 comp and 1.06 iw rear) on his rb30det. That makes 1bar on the dyno by 3900rpm. It feels not too bad on the street but lacks the go in the first 2 gears compared to the .82 gt35r. Click third and it really hauls.

[DennisRB30]

Auto's make a huge difference to spool.

Another mate rb_man has an XR6t turbo (.5 comp and 1.06 iw rear) on his rb30det. That makes 1bar on the dyno by 3900rpm. It feels not too bad on the street but lacks the go in the first 2 gears compared to the .82 gt35r. Click third and it really hauls.

It frys the tires in first gear and makes 1 bar by 3500 in second so that is certainly not the case with my setup. I have 4.11 gears also. But, yeah the taller gearing of the auto does help it spool a bit quicker. I was worried about lag but its not laggy at all. Another mate has a GT35 1.06 IWG with the 0.7 front on his manual VG30 R31 and its not laggy either. Must just be some prob with the RB30DET's.

Plenum maybe? Or just mismatched gears that were meant for high revving engines.

I think some of the guys with manual RB30DETs need to change their diff gears to suit the power delivery of the engine. 4.3 gears with a manual are not going to load it up enough in a light R32 or similar. I know someone who fitted taller diff gears which made the car much quicker since the turbo actually built boost in low gears.

Edited January 22, 2007 by DennisRB30

[Cubes]

It frys the tires in first gear and makes 1 bar by 3500 in second so that is certainly not the case with my setup. I have 4.11 gears also. But, yeah the taller gearing of the auto does help it spool a bit quicker. I was worried about lag but its not laggy at all. Another mate has a GT35 1.06 IWG with the 0.7 front on his manual VG30 R31 and its not laggy either. Must just be some prob with the RB30DET's.

Plenum maybe? Or just mismatched gears that were meant for high revving engines.

I think some of the guys with manual RB30DETs need to change their diff gears to suit the power delivery of the engine. 4.3 gears with a manual are not going to load it up enough in a light R32 or similar. I know someone who fitted taller diff gears which made the car much quicker since the turbo actually built boost in low gears.

That last little bit.. Hit the nail on the head.

[r33_racer]

Yeh cubes...so did we. When bought from gcg it was quoted as a gt35r .82...anyway after it blew with the last motor, discopotato03 got our dead turbo and checked it out...and found out its infact a gt30r not gt35r. So gcg ripped us off...but that was several years ago and i never checked the chra number or pulled it apart and checked wheel diameter...i assumed they provided us with the right turbo. Anyway new motor is in and ready to go with the gt35r weve just been abit slack finishing off the last few lines for the dry sump system. But i think its going to be a beauty:)

[Cubes]

Well no wonder you were scratching your head wondering why det levels were high at only 300rwkwish.

[r33_racer]

yeh yeh i know. Still i think final power figure was something like 370rwkws with it which isnt too bad for a little gt30r. Im hoping we will see 400rwkws with it. Only difference with this new motor is argo rods, dry sump system, and the gt35r. When time permits a 4" exhaust system for it too to replace the damaged 3"...got crushed when running off the track. However im not sure if the 3" was being a restriction at that power level or not.