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Massive Sudden Lean-out Rb20det

Rex_Kelway

By Rex_Kelway,
in Engines & Forced Induction

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Rex_Kelway Rookie

Rex_Kelway

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Posted

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...

KingPinnyupload.jpg

Thanks Lads

Rex

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Rex_Kelway Rookie

Rex_Kelway

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Posted (edited)

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 by Rex_Kelway
Mr. Oizo Grand Master

Mr. Oizo

Posted
Posted
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...

Rex_Kelway Rookie

Rex_Kelway

Posted
  • Author
Posted (edited)

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 by Rex_Kelway
crack Mentor

crack

Posted
Posted

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 Rookie

Rex_Kelway

Posted
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Posted (edited)

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 by Rex_Kelway

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