Massive Sudden Lean-out Rb20det

[Rex_Kelway]

Hi Lads,

Rex Has his KingPinny 'budget hack' on the Dyno the other day for its post-build, pre-thrash checkup. It makes respectable grunt with AFR's sticking nicely between 12.3 and 11:1 for the whole run.

However at the top of the run just prior to limiter (perhaps 500rpm) the AFR suddenly makes a dead vertical up past 14:1 which is where the operator jumps off the acceleratix. We repeated the run three times, peak power was within 2-3rwkw and the same massive sudden vertical leanout condition.

The dyno was done as a favour so no fault finding was performed, Rex was thinking that perhaps the AFM may be faulty (NIssan's are renowned for them) causing the ECU to basically drop the injector duty cycle right off.

The engine R32 RB20DET and is stock, along with the ECU and turbo etc. Only modifications are filter, exhaust and intercooler setup. Boost is un-modified but up to 11psi due to removal of restrictions in pipework etc.

Rex has considered AFM maxing however it seems more likely that Mr ECU would just go massively rich safety-like instead of lean.

Anyone seen/heard similar problems? He has seen a couple of other graphs with the same problem, but not an explanation.

Rex has some diagnosis to do on Mondey such as AFM peak voltage etc, but would be good to have some things to check if He runs dry ideas wise. It also seems very unlikey to be a fuelling issue because of the shape of the graph.

Have included printout below if it helps...

Thanks Lads

Rex

[crack]

maybe the fuel pump has hit a brick wall as far as flow goes. what type of pump is it and how old?

[MBS206]

Injectors maxing out is my theory.

[Mr. Oizo]

Use this to check if your injectors are maxing out:

http://z31.com/software/injector.pl

I still can't believe you got 180rwkw from a stock rb20 on 11psi

[Rex_Kelway]

Rex considered fuel pump not to be the problem because surely if pressure couldn't be maintained the AFR would rise gradually. PUMP is R32 GTR

Fuel injectors maybe, but supposedly they are good for 230odd rwkw at 100% DutyCycle. HOWEVER with stock reg, He knows not.

Sounds like Rex may need a slightly different Multimeter...

As for the power, trust Him, Rex cannot believe it either. Approx 140rwkw would've been a delight but the 192.6rwkw peak almost made Rex pass-out.

Edited November 11, 2006 by Rex_Kelway

[paulr33]

fuel pump

[Mr. Oizo]

Rex considered fuel pump not to be the problem because surely if pressure couldn't be maintained the AFR would rise gradually.

Fuel injectors maybe, but supposedly they are good for 230odd rwkw at 100% DutyCycle. HOWEVER with stock reg, He knows not.

Sounds like Rex may need a slightly different Multimeter...

Injector size: 270 cc/min injectors(25.7 lbs/hour)

Number of injectors: 6

BSFC: 0.65

Duty cycle: 100%

This combination will supply fuel for 237 horsepower

237hp = 182kw...

[R31Nismoid]

I still can't believe you got 180rwkw from a stock rb20 on 11psi

agreed, its in the land of "impossible" i believe

[crack]

r32 gtr fuel pump is still a 15? year old fuel pump.

[Rex_Kelway]

I knew this was going to happen, believe Rex he has heard it muchly since the day it was dyno'ed.

The engine is approx 60,000kms ex-GTS4 R32 from around 1993 He believes. Wether or not they use a different turbo (M-spec or whatever??) He knows not, but it IS the turbo that came in the half-cut. On Mondey he shall get serial no's to confirm.

Rex works for an importer, and yanked the motor out himself.

The car was 100% stock, no filter not even a timer or boost gauge. all of the factory bolts/sheilds/gaskets/retainers were in place with no signs of ever have being removed. Thats whay leads Rex to believe its stock.

Believe it or not the turbo is not the 'be all and end all' of the intake system. It is VERY dependant on the systems around it.

This was designed to be a help diagnose thread, not a 'you're a liar' thread. The Dyno may be wrong, but the operator has done it a thousand times. The car does feel that fast.

Back to the problem...

Fuel pressure shall be checked on Mondey to be sure

Edited November 11, 2006 by Rex_Kelway

[crack]

no one is calling anyone a liar. the figures quoted are at the top end of the believable scale.

all we are doing is trying to help diagnose a problem. if you get as many suggestions as possible, you can eleminate them one by one.

craig

[Rex_Kelway]

Yep, maybe a bit premature ...

Rex is just geared for the 'Thats too much power, its impossible...You're a liar!!!' arguement that is likely to follow that printout and specs list.

Edited November 11, 2006 by Rex_Kelway

[Morgs]

Have seen graphs like that when the fuel pump ran out of voltage (intank 044 without direct power feed from battery)

Edited November 11, 2006 by Morgs

[JSWR32]

Wouldnt hurt to check / replace the fuel filter too.

[Rex_Kelway]

New fuel filter as part of conversion.

Check fuel pump voltage, check.