Dyno graphs - BAD afr? - looking for some help

happynole · 03-19-2008, 10:37 AM

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?

prodrifter · 03-19-2008, 12:47 PM

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.

panapower · 03-19-2008, 01:30 PM

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.

rowdy-GTi · 03-19-2008, 02:17 PM

Weird how it goes from richer to way too lean. Usually it goes lean to rich??

A FPR will richen the whole curve out meaning you`ll run ok after 4k but super rich before.

Sure you haven`t got a vac leak still? If not i`d ditch the JWT ecu. A stock ecu will give better fueling than that.

happynole · 03-19-2008, 04:19 PM

Quote:

Originally Posted by panapower

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.

panapower · 03-19-2008, 04:22 PM

Quote:

Originally Posted by happynole

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.

toolsheded46and · 03-20-2008, 07:03 PM

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?

squirlz · 03-20-2008, 07:13 PM

Quote:

Originally Posted by toolsheded46and

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.

LaotianAsn4 · 03-20-2008, 07:23 PM

Hey Nole, I was one of the guys at the dyno? Do you remember his name by any chance? Could've been one of my G20 guys

Flounder · 03-20-2008, 08:16 PM

Dang that's lean! I had the opposite problem when I dynoed my car a couple years back...

happynole · 03-20-2008, 08:30 PM

Quote:

Originally Posted by squirlz

Just to clarify.

Thank you

Quote:

Originally Posted by LaotianAsn4

Hey Nole, I was one of the guys at the dyno? Do you remember his name by any chance? Could've been one of my G20 guys

I think his name was Ramie or something like that

LaotianAsn4 · 03-20-2008, 08:35 PM

Quote:

Originally Posted by happynole

Thank you

I think his name was Ramie or something like that

Lol, Ronnie...Hah, PM me your number and I'll get it to him.

Setzer · 03-20-2008, 08:44 PM

AFR looks VERY dangerous. Install the FPR as a band aid for now and crank it up a bit.

Benito Malito · 03-20-2008, 08:46 PM

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.

importfighter01 · 03-21-2008, 08:53 AM

Here happy:

http://www.sr20forum.com/all-motor/6...ff-big-hp.html

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.

FastNX · 03-21-2008, 07:44 PM

How certain are you that the Wideband was calibrated correctly?

wes · 03-27-2008, 05:14 PM

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....