More Turbo Questions ?

[Sydneykid]

Hi B-man, we used a GCG 450 bhp ball bearing hi flowed RB25DET turbo on a RB30DET (RB25DE head). It made 290 rwkw on the RB30DET at 6,250 rpm compared with 220 rwkw on the RB25DET at 7,000 rpm. Amazingly both were at 1.3 bar.

There are a few issues with this comparison;

The RB30DET had a ported cylinder head, the RB25DET was standard

The RB30DET had adjustable camshaft pulleys, the RB25DET didn't

The RB30DET had a split dump pipe, the RB25DET didn't

The RB30DET had a 3.5" exhaust and no cat, the RB25DET was 3" with a cat of unknown quality

The RB30DET had standard RB25DE camshafts, the RB25DET had standard RB25DET camshafts

My summation, the RB30DET breathed a lot easier (porting, inlet, cams exhaust) and therefore the turbo was able to spin a few more RPM and produce more airflow at the same boost.

We are just about to do the same thing on an RB31DET (RB30E block and crank + RB26 top end) with a GCG 500 BHP ball bearing hi flowed RB25DET turbo. I want to break through 300 rwkw with a hi flowed turbo and a standard GTR intercooler. Then we will stick the GT3040BB on it as the target is a responsive 600 bhp.

Bottom line, I'd give it a go B-man.

[RIPS]

Thanks sydneykid, Its good to see a direct comparrison with what you've done to what we do over here.

The motor on the above plot has no headwork at all, standard cams and pulleys, was through a standard R32 GTR intercooler, 3 inch exhaust and was at 1.4 bar (NOS brings it up a bit.) without NOS we got 270rwkw at 1.3 bar and I remember you said somehwere that the roller dyno uses about 20kw more than a hub dyno so we must be close!!! That same engine in a totally complete GTS4 with me in it (all up 1800+kg) on stuffed 18in road tyres with no drag wheel alignment, just straight off the street runs 1.7 60ft and mid 11's @ 200kph. Thats all with a totally stock internal motor.........Regards Rob.

[B-Man]

Thanks guys - great info.

Sydneykid, did your RB30DET with the RB25DET head and RB25DE cams retain the VCT ?

RIPS, that power is impressive for a standard rebuild.

Cheers,

[Sydneykid]

Hi B-man, No VVT that's why I chose an RB25DE top end over a RB25DET. At the time I thought all RB25DE's didn't have VVT and only RB25DET's did. But since then I have updated my knowledge and found there are RB25DE's with VVT. We were using the standard R32 ECU (chipped) and it didn't have VVT drivers, so that's the main reason I went for the RB25DE top end. The other is the more aggressive camshaft timing and lift.

I have never tried RB25DE camshafts in an RB25DET head. The only problem I can see is if it's an RB25DE without VVT it will not have the drive pegs on the inlet camshaft. If they are from an RB25DE with VVT then it will and they should fit straight in. I don't know if the RB25DE VVT camshafts are as aggressive in timing as the non VVT ones. I suspect not, as the VVT is mainly used to comply with tighter polution regulations which may also require less aggressive camshaft timing and lift.

Hope that helps

PS for RIPS; we use a Dyno Dynamics roller dyno and all numbers I quote are "real" on the day, not ambient compensated using Shootout mode.