Dynoed the truck today and found something interesting. I dynoed 2 chips. Last time I dynoed, I pulled 394/495.6 with the street side of my JDM flipchip.

Please note that on all the pulls OD was off, and truck went from 32-3300rpm (70 in 3rd gear) to 5400/5500rpm.

I made the first set of pulls on the PSP. I asked for a rich and safe tune and that's what I got.

After a brief cool down I dynoed the JDM chip, on its street side. I just wanted to see what my straight pipes gave me (or took away) since that was my only mod from last time. However I ran a lot richer than last time for some reason. Last time when I dynoed, at 5400rpm I was at 11.5. This time I was at 10.6!! I made 3 pulls and they all were consistent, with AFs ranging from 10.6-10.9. Suffice to say I lost quite a bit of hp, about 25-30, and also lost 30-35 lbs. of torque.

I'm not really upset about the power loss. This is NOT a tuner bash. I was just wondering what could have caused me to run this much richer all of a sudden. Could it be the straight pipes? It was a different dyno location and temp was a little warmer but I don't see how that could account for this much of a difference.

I appreciate any insight you guys might have regarding this. Again this is NOT a bashing thread against JDM or PSP. I don't want to start any tuner wars etc. and was simply curious as to why I'm running so rich all of a sudden. Could it be the dyno since both chips I made pulls with were extremely rich? I don't have access to a scanner for a while so if you guys need more info please ask.

Thanks in advance,
Charles

 

Also, I want to note that my first set of pulls on the PSP were also extremely rich. After 3700 or so it was below 10 all the way, on both pulls. Also lost power of course...a bit more since I was running even more rich (than my JDM tune).

 

I'm sure Sal and or Jim will give a sugestion, but if you havn't changed the heat range in your plugs, or made any fuel delivery changes, I'd say one of two things.
One you had a partially clogged fuel filter the first time around or too hot a plug.
Or, one of the Dyno's you used is off.

 

Fuel filter was changed 1k miles ago. 7000 miles on the truck. plugs are denso IT20s w/ about 3500 miles on them. they are gapped at .036-.038.

my mods are 4#, e-fan and e-waterpump, denso it20s, jdm filter kit. (more mods but i wouldnt see how a ft vbody etc would effect AFs or dyno #s)...

also my truck runs strong as chit. can't tell any power loss by seat of the pants feel at all. dont think it's a clogged fuel filter (as i've heard the effects of those)...

the rich results were from another dyno than last time. about 5-7 degrees warmer. dont have the other sheets so i cant tell you humidity, pressure,etc. but again this seems negligible when looking at the huge differences. i could be wrong though....


also this shop has dynoed lightnings before....and it came pretty highly recommended although the setup isn't as large as my previous dyno location (FLP in naperville).

 

also the 2nd set of pulls with the JDM were done without much cool-down as i had to drive around and key on/off since i swapped chips.

 

 

i dynoed both sessions (this one today and the one in oct.) on the same fuel filter. if it was clogged last time then i would not have been able to pull those numbers and would have definitely noticed something in performance after all this time. and if it became clogged today or recently i would have only ran into a lean condition, not a rich one.

would anything else cause me to run this rich? i'm just hoping i am not rich enough to blacken plugs, etc etc. hopefully it's just a safe tune that guzzles gas but does not have any real longterm effect on the motor (other than the fuel filter dirtying quicker, etc)

 

Did you have a bung installed for a wideband ? or did you have the probe stuck up the exhaust pipe ?

 

there were two taps, one under the hood on the passenger's side somewhere and the other on the exhaust tips. is that the reason?? (sorry i dont know which tap measures AF but there was one attached to my tips)

also just to note my straight pipes are only after the cats. so basically its just the muffler deleted with 2.5 inch tubing retaining all cats etc.

 

however even if it measured my AF inaccurately my rwhp and torque seem to correspond with the richness (ie i lost a noticeable amount of power from running noticeably richer)

 

Go back to the place you dynoed the first time and see if you have the same results. The dyno you use can make a lot of difference. There are guys out there with stock Ls dynoing with nearly as much power as guys with a 4 lb. pulley and a chip. Different dynoes can be that much off from one another. Even the A/F measurements can be different. This may not be the case in your instance; but, you can't switch dynoes and make reliable comparisons.

 

i may have to do that. my only reason for dynoing this time was to see the AFs on my psp. however i dont know how reliable the AF measurements are now since for my PSP i saw the AF plummet below 10.0 after 3800 rpm!

 

cyntaxx, it's safe to say it's probabaly not a fuel problem. What interests me is the fact that BOTH CHIPS ARE RICH. We're talking about the 2 tuners with the fastest Gen 2's on the planet and both of them surely know how to tune.
MY MONEYS ON FAULTY A/F READINGS THIS TIME AROUND

To answer your other question, I'm tuned for a 4 lb lower and a 2-3 lb upper but right now for the cold months my upper is off which means I'm running much richer than normal because I'm running
2-3lbs of boost less than I'm chiped for. Plus I have colder plugs than you do, so as for loading up, I would'nt worry, I'd just make sure you give it a nice 3/4 to full throttle blast once in a while for at least 5 seconds at a time to heat up the cylinders and clean up the plugs til you figure this out.
Sounds like fun

 

yah i understand the AF readings could be off but how the rwhp and torque loss seems to correspond. and i would hate to think the entire dynojet is miscalibrated...

on another note i think i would've noticed this signficant of a drop in hp. we're talking a good 20-25 horses here....and if i was running that rich i would have definitely noticed during fuel fill-ups (MPG etc) however its true that there are variables in there and i would much rather see #s on a screen (dyno) than seat-of-the-pants feel. and going to the track would not help currently since traction is a %$*#@

 

I had A/F's all over the place when I did my forst dyno,
and that was because the tailpipe sensors are hard
to get accurate readings from. Jim at JDM suggested placing
the monitor in one of the O2 metters holes or taping another
bung to be used for dyno readings.

Good luck ...