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Rb30 Feels Lazy.

Daboss

By Daboss,
in Engines & Forced Induction

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Daboss Experienced

Daboss

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Hey all I have finally put my rb30det together and I must say I feel accomplished doing it, but the improvements I expected from it are not there. It still feels like my rb25det. I don't know if it is just me or my expectations were to high but everything feels the same. I expected off boost driving to feel better and have more grunt and low down torque and a massive increase in spool seeing as I went from a 2.5 to a 3 liter while using the exact same turbo and housing, but no such luck.

To give a bit of background on the car: I had a rb25 with a few mods,forged pistons, forged rods, all bearings changed to acl bearings, freddy intake manifold, t4 twin scroll manifold with the collector for the wastegate merged so you only use one wastegate, hx 40 with t4 .58 housing, 850cc injectors, ford lightning maf, meth injection, walbro e85 450 lph in tank fuel pump all controlled by a power fc.

Never dynoed the car but was making excellent power for me. Boost of about 15psi came on full at about 4000rpm in second from a cruise doing about 2000rpm then going wide open throttle. It lit up the tires doing that in second and pulled all the way to red line. In third and fourth I had strong pull all the way to my redline of 7000rpm as well. Needless to say being lazy I knocked the motor due to lack of oil, so instead of a full rebuild I decided to go rb30.

I sourced all the parts I needed and built an rb25/30, used the rods and pistons that came with the block with a new set of bearings, rings, rod bolts, crank collar mod, oil pump gear mod and 1.2mm mls headgasket. Reused everything else that would have been on my 25 to finish build. So engine was exactly the same as what was in my rb25 except I now should have half a liter more displacement right?...........

Wrong!!!!

Car is up and running now and I have put a road tune on it and it feels no different from my rb25. As I stated earlier it feels just like my old rb25 and in some instances less responsive, was just being a bit stink with the less responsive statement, but I was expecting such a different drive that I meant every word of it. Same turbo on the car and the spool time is the same from a log I did full boost at 4000rpm flooring it in second, it doesn't light up the tires the way the 25 did. In fact it doesn't spin them nearly as much, don't get me wrong it pulls but just not as I imagined it. The off boost driving feels just the same as the 25. I figured spool time would drop at least 500rpm and I would need a new set of tires in a day or two from lighting them up in first second and third and off boost driving would feel like my old 25 driving off straight from cold start, but it doesn't.

From the information I gave you what do you guys think? Am I just expecting to much or is my disappointment warranted?

A little bit more information I forgot to mention. Car had oil leak around crank after fixing mistakenly put car timing out about a tooth drove round like that for about a week boosting and tuning noticed difference from taking longer to crank and loss of response. The car use to start basically half a crank but now it cranks longer to start ever since timing was out fixed it and since fixed the cranking hasn't improved and still feels a bit gutless on the power and response side of things.

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Shoota_77 Veteran

Shoota_77

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Too low in comp? Was it originally a turbo motor or non turbo? The turbo motors were something like 7.5:1 comp or something like that from memory. With comp like that to get the most out of it you need to run a big turbo which obviously means delayed onset of boost. To be a nice responsive motor off boost you need to be running at least 8.5:1 but preferably mid 9's would be better. If you're still running methanol in conjunction with E85 I'd imagine you could get away with even higher than that on a well tuned/well setup engine.

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Daboss Experienced

Daboss

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Too low in comp? Was it originally a turbo motor or non turbo? The turbo motors were something like 7.5:1 comp or something like that from memory. With comp like that to get the most out of it you need to run a big turbo which obviously means delayed onset of boost. To be a nice responsive motor off boost you need to be running at least 8.5:1 but preferably mid 9's would be better. If you're still running methanol in conjunction with E85 I'd imagine you could get away with even higher than that on a well tuned/well setup engine.

The motor was originally a non turbo motor, or so I was told. Is there anyway to tell a non turbo from a turbo rb30? No e85 were I am from. I am running water meth injection in conjunction with USA 90 ron.

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KiwiRS4T Grand Master

KiwiRS4T

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Low compression is the most likely problem but double and triple check the cam timing. Have you done a compression test?

It won't help your off boost performance but turn up the boost to 25psi (more cylinder to fill up).

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Ben C34 Grand Master

Ben C34

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Turbo engine had oil squirters, and a noticeably less material on top of pistin to reduce comp (same chamber volume)

If you used stock na pistons and a non neo head you would have aprox 8.3to1 which is low. Sure you have added capacity bit the drop in comp comes at a price.

As kiwi said check cam timing, what gaiety thickness did you use?

The thinner the better in the car of non neo head stick piston build.

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Daboss Experienced

Daboss

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Low compression is the most likely problem but double and triple check the cam timing. Have you done a compression test?

It won't help your off boost performance but turn up the boost to 25psi (more cylinder to fill up).

Cam timing was quadruple checked it is spot on. Will do compression test this weekend and let you know the results. What type numbers should I expect going with I built it right and compression is around 8.3:1? Also am I right to assume that there should have been noticeable gains over the rb25 if the motor was built with 8.3:1 compression ratio?

It is virtually the same as my old engine which would have been 8.5;1 or maybe even a bit lower as my old rb25det headgasket was a 1.3mm. Only difference would be this engine has a half liter more displacement, which should equate more everything.

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KiwiRS4T Grand Master

KiwiRS4T

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I have a low compression RB30 which severely limits off boost as well as outright performance making 314AWKW with a GT3540 - others easily make 350 -400 with the same turbo and higher compression. I don't know the number but it will be around 8:1 A compression test on mine comes out at about 135psi - ideally you would want better than 9:1 and about 180 psi

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r32-25t Grand Master

r32-25t

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Turbo engine had oil squirters, and a noticeably less material on top of pistin to reduce comp (same chamber volume)

If you used stock na pistons and a non neo head you would have aprox 8.3to1 which is low. Sure you have added capacity bit the drop in comp comes at a price.

As kiwi said check cam timing, what gaiety thickness did you use?

The thinner the better in the car of non neo head stick piston build.

no rb30s had oil squirters
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XRATED Veteran

XRATED

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... something is up.

I went from a stock rb25 with bolt on's to a low comp 25/30 with the same everything including tune (just bumped the rail pressure) and it was a noticeable improvement.

yeah, don't think any rb30's had oil squirters.

J

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Daboss Experienced

Daboss

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I have a low compression RB30 which severely limits off boost as well as outright performance making 314AWKW with a GT3540 - others easily make 350 -400 with the same turbo and higher compression. I don't know the number but it will be around 8:1 A compression test on mine comes out at about 135psi - ideally you would want better than 9:1 and about 180 psi

Well definately not 9:1 compression in fact I am assuming around the 8:1 to 8:3 range. I used stock n/a pistons with rb25det head and 1.2mm mls head gasket.

... something is up.

I went from a stock rb25 with bolt on's to a low comp 25/30 with the same everything including tune (just bumped the rail pressure) and it was a noticeable improvement.

yeah, don't think any rb30's had oil squirters.

J

Exactly what I am feeling. Like I said don't know if my expectations were to high, but it just does not feel right. Feels like my old rb25 and with basically the same everything except a half liter more displacement I should see/feel noticeable gains. The turbo spooling at virtually the same rpm is indication to me that its basically the same as my old rb25. Guess you guys will be able to tell me more after comp test results.

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