Rb30 Response/spool Time

[09ONE_32]

Hey guys I am nearly finished with my 25/30 build and something that has had me guessing is how soon I will have full boost compared with the RB25DET.

The only changes will be a little head porting, a genuine Greddy intake manifold and Q45 throttle body.

What’s the general consensus on spool time with identical setups compared to an RB25? I would hope to see full boost 500-700rpm earlier with a 8.2:1 CR RB25/30 over the RB25DET. My setup on a stock RB25DET with a set of cams (these will be used in the 25/30 as well) saw 1 bar of boost by ~4100rpm.

Is it out of the questions for me to make 1 bar of boost by 3300rpm based on the details above?

Those of you that have kept similar setups from RB25-25/30 post up your results so I can stop trying to estimate my spool time, response and average power.

Cheers.

[VB-]

what turbo?

it may be possible with adjustable cam gears/tuning, but so many things can change how early a turbo spools, like headwork, i've seen this go both ways, sometimes bringing power on earlier, sometimes later etc

[Al]

what turbo?

it may be possible with adjustable cam gears/tuning, but so many things can change how early a turbo spools, like headwork, i've seen this go both ways, sometimes bringing power on earlier, sometimes later etc

Why is that relevant? He is asking if the rb30 will spool up the same turbo faster than an rb25.

In short yes.

My mate has a very similar set-up to my rb30 on his rb26. We have the same turbo, same plenum, and very similar manifolds (i used ETM, he used 6boost). His GT30R makes full boost by approx 3800-4200rpm, on the rb25, mine makes full boost by about 2800-3000rpm on the rb30. I do have Tomei Poncams and headporting, where his engine is "unknown" as it was re-built before he purchased it. I personally think head porting and cams make the engine/turbo slightly laggier (in my experience about 200rpm) in the low rev range, but produces more power in the mid and high rev range.

RB30 all the way; cubes does matter, even with turbo 6 cylinders.

I couldn't be happier with my build!

[WHITER33GTS-T]

I have found the same thing with my 25/30 full boost is around 1000rpm earlier

Go the RB30

[09ONE_32]

Yewoo!!! I was hoping that would be the case. Even If I had full boost 700rpm earlier I would be very happy.

Al, full boost by 3000rpm would be pretty insane I take it? What size rear on the GT30? 0.63? And what was your power output?

The reason I didn't list my turbo specs is because they are a bit sketchy... It was a HKS TO4S which I have rebuilt twice, the second time with a full ball bearing water cooled core. Each time it was rebuilt the housings had to be machined and a slightly larger compresser/turbine needed to be fitted. I think it's a GT30 comp wheel and a largish TO4 Turbine of some description. Front cover is 0.6 A/R, rear is 0.63 A/R and the turbo is on a mid mounted HKS cast manifold with HKS 38mm gate.

Turbo made 380rwhp on stock RB25DET with cams @15psi with full boost ~4100rpm, so I think the RB30 will be a midrage monster with this setup.

Originally I was going for Mahle 9:1 CR pistons but couldn't get them so ended up going with the Mahle 8.2:1. Will the drop in CR make a noticeable difference to turbo spool? I have heard that a few guys have had some trouble with pinging at highish power levels with the 9:1 CR and end up having to pull a fair amount of timing out to avoid this.

What are the majority of people using as a static CR?

[bubba]

I've got dyno sheets showing same setup on my RB20 and RB30, I would hazzard a guess that RB25 would be somewhere in between so about 800rpm sooner spool sounds about right as there was about 1700rpm difference between the 20 & 30.

[Al]

Yewoo!!! I was hoping that would be the case. Even If I had full boost 700rpm earlier I would be very happy.

Al, full boost by 3000rpm would be pretty insane I take it? What size rear on the GT30? 0.63? And what was your power output?

The reason I didn't list my turbo specs is because they are a bit sketchy... It was a HKS TO4S which I have rebuilt twice, the second time with a full ball bearing water cooled core. Each time it was rebuilt the housings had to be machined and a slightly larger compresser/turbine needed to be fitted. I think it's a GT30 comp wheel and a largish TO4 Turbine of some description. Front cover is 0.6 A/R, rear is 0.63 A/R and the turbo is on a mid mounted HKS cast manifold with HKS 38mm gate.

Turbo made 380rwhp on stock RB25DET with cams @15psi with full boost ~4100rpm, so I think the RB30 will be a midrage monster with this setup.

Originally I was going for Mahle 9:1 CR pistons but couldn't get them so ended up going with the Mahle 8.2:1. Will the drop in CR make a noticeable difference to turbo spool? I have heard that a few guys have had some trouble with pinging at highish power levels with the 9:1 CR and end up having to pull a fair amount of timing out to avoid this.

What are the majority of people using as a static CR?

Full boost by 3000rpm feels absolutely farken awesome! I am picking the car up tomorrow (Friday), as i just got it fully tuned. Not too sure of the specs and final results, but i think it made 325rwkw@19psi with about 8600N of tractive torque. Low boost is apparently similar to my run-in tune: 310rwkw@15psi; Once on 15psi, the power graph is linear with a phat torque curve. Apparently high-boost is a lot more aggressive and has heaps more mid-range grunt; kept on breaking traction on the dyno, that's trying 4 different sets of tyres, including RE55s.

That turbo sounds way too small. I am maxing out the GT30R, hence why my graph looks so linear and why boost is also slightly dropping at high rpm. Note the lack of power gain from 15psi to 19psi, only 15rwkw. The only reason i kept high boost at 19psi, is to gain torque and a shit load of mid range power/torque. The turbo is maxed! Will post pics of final graphs soon, once i have them.

I am running 9:1 CR, my mechanic hasn't alerted me to any pinging issues. It is a fully built motor, with a fair bit of money thrown at it.

Below is my run-in tune:

Dotted line = Power curve

Solid Line = Torque Curve

[discopotato03]

What sized turbine housing do you have on that GT3076R ? It's not possible to "max" these turbos out without the largest or 1.06 A/R GT30 turbine housing on it .

I'm not sure if any of you have ever had propper Garrett GT30 and GT35 turbine housings side by side . Look like very similar castings to me ...

Sk told me ages ago that a well setup RB30 twin cam comes on boost at around 32-3300 revs with a GT3582R 1.06 A/R turbine housing .

If we assume that GT30 and GT35 turbine housings use the same or similar castings machined to suit the two different turbines its logical to assume that the big housing with the 3076R's smaller turbine and compressor wheels should spin up sooner all else being equal . For starters the GT30 turbine being smaller OD than the GT35 one will have less innertia to overcome and the fact that the nozzle and exducer diameters are smaller means the gas speed will be higher through the blades than it would be with the larger turbine .

The GT37 compressor in a GT3076R (aka GT3037R) has lower drive requirements than the GT40 compressor in a GT3582R (aka GT3540R) so the perceived "lag" will be less than a GT3582R will have in the largest 1.06 A/R turbine housing .

Your call but if I was building a street RB25/30 I think about a 9-9.3 CR (+ poncams) and a GT3076R with the big turbine housing , the lower exhaust side pressure should allow you to push healthy timimg numbers into it so it can make good pre boost torque and have good throttle response . The larger housing should make for economical highway cruising because it wont be jumping onto boost when it's not needed .

I'm not prepared to state what revs it will make positive pressure at but my guess is 23-2500 revs if tuned properly .

I'd like to think a 9.3:1 CR RB30 Twin Cam would be quite snappy in an R32/R33 without being restrictive , clean AFR's and best mean torque timing should make it feel strong and a 300 + Kw capable turbo make more torque than 2wd traction from the mid range up .

Torque is everything IMO , cheers A .