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Rebuilt Rb25 Problem

al_r33

By al_r33,
in Engines & Forced Induction

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Cubes Grand Master

Cubes

Posted
Posted

SECUR1TY, similiar as to how I ran mine in.

I basically drove half to full throttle every time I accelerated.

Its first drive was along the sea front that has lots of small round abouts so every half a minute it was seeing lots of load. :D

al_r33 Rising Star

al_r33

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Posted (edited)

Basically the mechanic recons that it has a ratio of around 7.5:1 & that the VCT isn鈥檛 correct! He spoke to a few guys and they have had the same problem with a rebuilt rb25 with all the mods should have made 300rwkw but made around 180rwkw so the up the ratio to 8.4:1 or 8.5:1 and played around with the vct and cams & stuff like that and put it on the dyno & it made 330rwkw @ the same boost & same tune!

So they have suggested to me that we raise the ratio to 8.4:1 or 8.5:1 & muck around with the head & get it back to the dyno for more tuning!

Does this sound like a solution or what?

Also does anyone know anyone that is making decent power of a ratio of 7.5:1?

Cheers

Alan

Edited by al_r33
Cubes Grand Master

Cubes

Posted
Posted

The low comp won't really affect power that much. But it will allow you to dial in an unusual amount of ign. timing.

IF the VCT is out it 'could' be bleeding off cylinder pressure?!?!

I would have thought if VCT were out so much as to affect a comp ratio test it would show up with a a crap idle.

BUT.. One concern is the wavy compression results. So that again brings us back to an iffy rebuild. And then the oil going everywhere?!?! WTF.

al_r33 Rising Star

al_r33

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Posted (edited)

nar the oil was comin out the oil line for the turbo! plus the car is barly drivable atm eg. wont idel & i allways have to keep the revs up or it goes to stall! but i think that is being cause by a faulty afm or busted ic hose!

but i have tacked down the guy who built it & going to talk to him as to why he would build an engine with a compression ratio of 7.5:1.

Edited by al_r33
Abo Bob Grand Master

Abo Bob

Posted
Posted

7.5:1 is 1980's turbo style.

When the tuner did his thing, did he push it to the point of detonation with boost and timing then pull back for saftey? Just wondering if it's low CR and the tuner didn't go to the edge to see where it was.

That's still only an alternative to what every one else is saying about a really poor rebuild which seems more likely at this stage.

al_r33 Rising Star

al_r33

Posted
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Posted

Yer he told me that he did push it to the point of detonation as he said he physically coulnt dial in anymore boost or timing & then he backed way off! It wouldnt even make more power when he would lean it out!

im getting to the point where im nearly over the old skyline!

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