I went through and found my old dyno sheet.



Here is why I pulled it up. When I first modded my truck, I only had a 2# pulley and a flip chip from JDM. That is what was on the truck when I dynoed it. Stock exhaust, TB and a JDM cone air filter. My best e.t. with decent traction was a 13.6 (at 4100 ft elevation here) and normally it would run 13.8's.

I decided to step up to a predator with a JL tune and a 4# pulley. I also decided to install a wideband O2 at the same time to be safe. To my dismay, my best time was a 14.2 but my a/f ratio was a "safe" 11.5:1. I went back the following week and with the 6# pulley and JL tune ran a 14.0 with the same a/f ratio as before.

The really dissapointing part about all this is the guy I sold my JDM pulley and flip chip to ran a 13.8 and does so time after time.

I'm trying to figure out where the power is at. My guess would be the a/f ratio and timing but I have no idea what the timing is on the JDM chip nor on the JL program. i do know that the JDM chip is actually a 4# pulley program but since we only have 91 octane here, that is what Jim had burnt for me for the 2# pulley.

All the times mentioned above were on drag radials and I have no mph figures since the "track" only displays e.t.'s

Need some expert advice here.

Thanks

 

you can see what your timing is on your predaotr by datalogging on a run, or havinmg a freind watch it while you stomp it.

 

What were your 60' on all the runs? How about temp?

 

well the only 60' time I have was from the best run. That time it was about 65 degrees out:



The other times (14.2 and 14.0 along with my buddies 13.8) were at a different track with only the e.t showing on the display with no slips or mph.

He will pull away from me on the 4# and we are dead even with the 6# compared to his 2#.

I also tried to datalog the timing but the predator told me that the selection was not allowed on this vehicle or something of the sort. it let me check everything BUT timing. Go figure

 

your power loss is comming from the change in a/f. On these motors in a basic stock/bolt on set up, the closer you get to stoich, generally the more power you make untill you eventually explode.

What do you think is better........running 14's and a safe tune, or running high 13's and about to have to dump 10k on a motor???

 

Logic tells me this is not a safe tune 13:1 but I figured I would ask the experts here.

 

I have always been tol that lean is more powerful but also more dangerous. Did anyone see the engine masters challenge on speed or in popular hot rodding. They build the motors to hold up to detantion.

 

I have been to a couple of dyno tunes in the past couple of weeks the tuner set all 3 trucks around 11.8 -12 a/f they where making well over 500 rwhp on 93 pump gas.ie built motors. If i where you i would get a dyno tune for sure getting ready to get mine dyno tuned soon .The way i see it if nothing else peace of mind right.

 

Now a days the Red Line (AF Chart on the Dyno sheet) is set at 12. You never want to go over that as a rule of thumb, especially in the higher RPM's (4500 - 5500)

My old stock motor had a AF of 10.4 when I put down 501/615
on a 75 Shot of Spray.

My New motor was showing an A/F over 12 in the high RPMS,
That is not exceptable for Sal or me, my problem is I ran out of Pump, the stock pumps cant flow enough for 22lbs of Boost, (and we still have to throw 150 HP of Spray on top of that : o )
Just to get it back under, I had Sal put new larger pumps in Sun, and we got other plans before re-dynoing. AS said, your's is WAY TOO LEAN, AND DANGEROUS



See what was happening if I stayed into it longer
TOTALLY NOT EXCEPTABLE Not for us at least

 

I feel the same way. Guess I was running on the edge with that other JDM tune but I would rather keep the motor together.

I have already contacted JL about getting more aggressive with my tune so we will see what happens.

Thanks guys!

 

FWIW,..... Here's some info for you guys.

Supercharged engines will develop maximum power at 12.5 air fuel ratio. Minimum detonation will occurs at 11:1 fuel ratio,....BUT power will be down because the engine is richer. After 11:1, richer ratios DO NOT suppress detonation from boost or excessive timing. ALWAYS, run the best fuel available,....PERIOD

Air fuel ratio is 50% of horsepower. Example: An engine's horsepower increases 20%. Air fuel ratio will decrease by 10% - 300hp @ 11.1 ,.....vs 360hp (+20%) @ 12.2 (10%)

 

I'm not a modern car tuning guru. But I do have some observations and an opinion. (don't we all)

*needed* fuel for the best power is based on load/air flow. In my understanding these dyno jets don't actually load the motor the same way that running down the track does. Therefore the motors are not loaded as much during a dyno pull. Or maybe I should say.. they are'nt loaded in the exact same way a run down the 1/4 would.

Also, many guys are spinning thier eatons waaay beyond it's efficiency range. Sure your gonna flow more air. But your also over heating the charge and the tuners need to pour the fuel to it to cool the head temps. (small planes do this I'm told)

Also it's my suposition that tuners are to some degree guessing (educated guessing) that XX.X amount of A/F ratio on a dyno pull will be good out on the track. The more trucks they tune... the more feedback they get... the better thier guessing becomes. (As would any of us who don't have big money to spend on finite measuring equipment that the OEMs do)

My A/F as measured on a dynojet pull starts off around a 13.5/1 & dips steadily to a 12 flat on the top end. May sound "lean" to some of the armchair QBs out there. But my plugs don't lie!

Just my redneck 2 cents, Rich

 

thought you used a mustang dyno?

 

It was tuned on a mustang dyno. I'm talking about a dynojet pull I've made since then.

Rich

 

Acceptable.