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First off, a little background on my setup. For the December runs I had a JDM highport swap with S4 cams, UR pullies, Thermoblock spacers, JWT popcharger, wrapped SSAC with 2.5" downpipe, Catco 3" high flow cat, and a 2.5" mandrell bent catback exhaust. Timing was set at 19 degrees. I also have a JWT flywheel and an SR16 tranny if that makes any difference (I wouldn't think it would matter). The changes made from the Dec runs to the Jan runs were a JWT ecu with the pop program for premium fuel and rev limit raised to 7950, timing moved from 19 to 15 as jwt recommends, and finding & fixing a vacuum leak that was causing a rough idle even after the new ecu was installed. Here are the graphs:
I was very dissapointed with the Dec runs, and while I'm happy with the increases in both power (+6.5 hp) and torque (+11 ft-lbs), I was honestly expecting more than 150 hp. I didn't have afr numbers for the Dec runs, but I had a bung installed pre cat on the exhaust before the Jan runs so that afr's could be watched.
I honestly don't know a lot about afr numbers, but was told that I am dangerously lean. I picked up a adjustable fpr, fp gauge, and a new fuel pump from Greg V, and while I can install these on my own, I don't know what setings I should be at in terms of fuel pressure, afr, etc.
I met a few guys at the Atlanta dyno day in January that seem knowledegable about this and one offered to help me out, but I lost his number. Any help here?
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Ruby Red 91 NX2000.... Speed doesn't kill, rapid deceleration does
White 93 SE-R..........rebuilding
Fuel pressure needs to be at 3 bar, or 44 psi. The air/fuel ratio looks to be very lean. I think it needs to be right around 12.9-13.1 range. But I too, am a noob with air/fuel ratios.
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The Ride: 1994 Nissan Sentra SE-R
USDM original lowport, AEM cai, SSAC header, fidanza flywheel. UR 4 pc. pulleys, 2.25" exhaust, stock timing
152.8whp
134.8 ft.-lbs torque
gwad... that's lean like a mofo on WOT. if that sniffer is at the tailpipe then you can rest assure to take off ~ 0.4 off that reading to get a better idea of what its truly reading close to the engine.
gwad... that's lean like a mofo on WOT. if that sniffer is at the tailpipe then you can rest assure to take off ~ 0.4 off that reading to get a better idea of what its truly reading close to the engine.
The bung is just aft of the header collector flange, about 6" in front of the cat.
The bung is just aft of the header collector flange, about 6" in front of the cat.
if that's the case. that's bad. cause we typically see around ~ 0.4 difference at the tailpipe than the bung before the cat or on the downpipe of a turbo. sort that out maing. lean is mean but that's just really mean... to the engine.
Not that this is your problem but yuor timing is at 19 degrees. Correct me if im wrong but doesnt jwt recomend with their ecu you run it at 15?
Quote:
Originally Posted by happynole
The changes made from the Dec runs to the Jan runs were a JWT ecu with the pop program for premium fuel and rev limit raised to 7950, timing moved from 19 to 15 as jwt recommends, and finding & fixing a vacuum leak that was causing a rough idle even after the new ecu was installed.
Just to clarify.
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It seems that some people have been spoon feed their whole lives, It is societies job to teach them how to use the spoon for themselves.
You have just a pop on the stock plastic hose? I'd be tempted to find a 3" mandrel bent pipe in there. That will lean it out more but once you figure out this bug you'll want the air. A nismo fpr can really help eek out some ponies NA. Remember MK's big NA thread on?
Definitely try again with a stock ECU. Thermoblock spacers shift the curve to the left iirc so you'll have plenty of room to rev still.
There he goes one of gods own prototypes. A high powered mutant of some kind not even considered for mass production. Too weird to live and too rare to die
HST
Last edited by Benito Malito : 03-20-2008 at 08:48 PM.
Mike Kojima confirmed that a cammed motor with a 3" intake runs lean and needs more fuel psi to richen things up. He says anything over 13.2 is getting too lean. If you look at many SR20 dyno's with afr graphs, they almost always run too lean. In other words, our maf's don't compensate for the extra air too well. He says in the thread above that after adding 4 extra psi (that would be like 48 psi at WOT vs 44 stock) it brought the afr down to 13.1, but this is still on the edge of lean. According to what I've read an sr motor can run as rich as 12.6 and not have a negative effect on hp. So in your case i'd recommend a stock ecu and 5-6 psi of extra fuel. Its better to be rich than be lean.
Last edited by importfighter01 : 03-21-2008 at 11:46 AM.
Reason: mispelling
I agree with the above post. I am not saying it is not lean, but verify the sensor and equipment are accurate. Anyone that tailpipe mounts a sensor (perhaps there are some exceptions) you can pretty much toss out those readings. They slap it on every car regardless of what type of fuel they are running and mistreat the sensor. I do not put much faith in those types of shops...
If they pull the sensor out of a case and can show you how they calibrate or test the sensor for accuracy, then I would trust the readings; provided you are certain there are no exhaust leaks....
Speed doesn't kill, rapid deceleration does 
