Weird Problem With Rb30/25

[SirRacer]

Gidday all,

Just looking for some ideas on a problem ive encountered. My car makes 295kws on 14psi and then basically stops making power from that point on even with the cam gears adjusted, more boost and ignition timing changed etc.Ive added the dyno plot which shows 4 psi = about 9 kws which isnt right for a turbo of my size.

Rb30det

R32 rb25 head with cam gears but stock cams

Rebuilt internals

8.5 comp rb30, all rebuilt etc

3.5 inch exhaust with one muffler (loud as hell so hopefully flows ok)

gt3540 1.06 turbo, with Sinco customs turbo manifold with the gate out the housing.

Im just looking for some first hand ideas of what the problem may be. Some would say cams, but ive had friends of friends make 370kws on the stock cams. My intake is a bit interesting so have added up a picture of that 2.

Any suggestions would be great, but if you dont know, please dont post as it will just give me things to check that i dont need to.

Cheers

Edited January 26, 2011 by SirRacer

[Moodles2]

Haven't mentioned much info on the exhaust, can the cat have collasped and is causing an exhaust restriction?

[Girorostar]

Which intake manifold is that? It looks like the RB20 manifold. I would think that is your restriction. From what i've read on this site is that these manifold wont make more than 300kw, should look into getting a front facing plenum.

My 2cents

[R31Nismoid]

Well we all know it's not the cams, plenty of people have run far more power with the same turbo.

Check the timing belt is on correct, even if you've checked it. Recheck. the amount of times this has been the issue is amazing of late.

Doesnt sound like exhaust issues, either way drop it from the dump pipe, super easy check

Inlet manifold as stated above is a good option too, but more hassle

Measure boost pressure @ turbo outlet and somewhere after the intercooler to check to see if there is a pressure drop/issue

That'll give you plenty for now.

[The Mafia]

I'm thinking an inlet manifold too.

I'd look at getting yourself a greddy copy or something. Can be had from Autobarn for about $350. Don't buy ebay ones, they are shit, and you'll end up replacing it.

[SirRacer]

Thanks guys.

Exhaust has no cat, one cannon muffler and bugger all bends. Its noisy as hell but i didnt build it as a street car.

Intake is an r32 so you cant just go and buy a greddy copy so easily, its custom manifold time.

I asked about the timing belt and whether the cams werent installed at TDC, but the tuner said the engine ran way too smoothly for that to be the case.

Will check out the turbo pressure drop too.

A friend of mine whos very clued up with rb's is doing some research as well so hopefully we can get to the bottom of the problem.

[paulr33]

what brand are the cam gears

are they secure, have they been double checked

check base timing at idle

as ash said, double check, triple check

whatever is wrong, is fundamentally wrong given the power is ass, ie it wont be a slight restriction causing it, id say timing is way off or something fundamental to make that much of a difference in the results (or to hamper it)

[Tony de Wonderful]

Dodgy batch of fuel?

[SirRacer]

Greddy cam gears. Very secure. We adjusted them both ways and they just shifted the power curve.

Something is definitley wrong somewhere so all these ideas are great. Im not sure about the fuel batch idea though, maybe read the post a bit more, as its making power everywhere else, so there isnt any reason why at a set point it should stop.

295kws @14 psi is actually pretty good power wise, its just once we get past this point that things cause issues.I asked the tuner about the timing and he said its bang on. Cant download the map at the moment but will send it to Lith who will no doubt check it out once ive got the info.

[R31Nismoid]

It won't be in the map, it'll be something else dude.

As i said - just because you are "told" the timing belt is correct, does not mean it is.

Cars can have a belt off 1-2 teeth and run/idle perfectly but have issues @ varying points.

You really need to have it all checked and ruled out otherwise you'll never get anywhere.

[paulr33]

agree

much like in complex ip network troubleshooting

assume nothing; prove everything

[SirRacer]

Is this DIY mechanic sort of thing or should i be checked by a workshop? Will get it checked by mechanic mate on Saturday. I asked the tuner about this also as the engine has just been rebuilt. He seemed to think that it wouldnt make good power anywhere if that was the case, but will check it now anyway.

I havent seen any other rb25de (r32) intakes with power levels higher than this so thought id may have been that.

Edited January 27, 2011 by SirRacer

[Lithium]

Only reason I asked for the map was I wanted to see what was happening with timing and fuel in the higher load zones, IMHO at 14psi its making reasonable power for the boost level - so the fundamental flaw isn't related to the engine's inherant ability to use air and make power... there is something that changes when it goes from 14psi to 18psi. If the tuner was having to do weird things to keep everything happy, I thought it might be a clue given its the closest to having the car right in front of me.

The power curve tracks the previous one - usually with a boost leak or a restriction of sorts the curve will change shape a bit, but in this case it actually looks like the boost level is different but its hardly reflected at all in torque or power anywhere in the curve. At the moment it seems easiest to blame the inlet manifold, though there are apparently other cars which have made more on the stock one on pump gas - I haven't seen any in person myself however, as most people seem to go aftermarket after 300kw.

[SirRacer]

Just tracked down a guy in NZ who has had a similar problem. He couldnt quite explain it but the gist was that the belt was stretching and throwing the timing out.

Anyone care to explain how this would work?

I spoke to a friend whos a mechanic tonight and he seemed to think if the belt was out and throwing timing the car would run like crap, yet mine runs perfectly.

This is what he wrote anyway (i cant quite decipher it)

"My Car we changed the 360 degree cam angle sensor

And I put on a Crank Angle Sensor. Was going out by 14-15 degree now is 0/0 perfect timing.

When we put cam angle sensor on made 409kw I think and timing out by 4 degrees. Put Crank angle sensor on the 0/0 made 451kw at same boost"

[STATUS]

the Nissan CAS do weird things when on the fritz i've had a similar issue to your NZ mate but it had nothing to do cam belt stretch.... as for your actual issue i could not say.

[O2 Autosports]

what fuel system have you got, can you go rich(10-11) on full power if you want?

[Lithium]

Just tracked down a guy in NZ who has had a similar problem. He couldnt quite explain it but the gist was that the belt was stretching and throwing the timing out.

Tuner should probably be able to see symptoms of this while tuning - thats with the CAS. I'd also expect this to be an obvious issue at all boost levels.

[Dose Pipe Sutututu]

what fuel system have you got, can you go rich(10-11) on full power if you want?

highly doubt it's a fueling issue, look at the A/F.. it's bang on 12:1 for both pressure levels