It's a ratio not percentage. The V8V starts it at stoich (14.7:1). Then under full wide open throttle the injectors are programmed to dump fuel into the cylinders at roughly 10:1 (or worse at times). ECU tune will of course correct this, simply view my ECU tune thread from a while back to see the massive change in AFRs. Ideally you want to be around 12.5 across the board under WOT.

Hope that helps

 

Btw, in order to have the correct gearing ratios on the dyno dynamics you can manually input the exact tachometer ratio settings:

Engine speed: 3927 rpm
Road speed: 63mph
Tachometer ratio: 62.33 rpm/mph

That will allow the redlined to matchup perfectly under load

 

Thanks for the input guys, my mistake, did not mean to put the AFR as percent (it is a ratio of course). Will post my graph when I get it but if memory serves correctly, it did start out in the 14-15 range at 2k-4k and then at the top end had dropped down to below 11. The plot looks qualitatively similar to that posted by DetomasoGTS74.

There were a variety of codes thrown attributable to the front wheels not moving. The P code did show a discrepancy from one bank to the other which seemed weird, esp since there was no fan set up in front of the car (which in retrospect might have helped with the absolute power numbers). There were no significant air currents in the shop that I can recollect. The car was dyno'd with the tail of the car venting out the garage door.

Anyway, I'm encouraged that this could have been a code thrown only bc of the dyno conditions. But I have no explanation for one bank showing a fault and the other running within spec (and yes, the short term numbers were also discrepant R to L).

Question is this, since all I really care about are the relative improvement from pre- and post- modification, is there any compelling reason to switch dynos?

 

Thanks for the info, that's v helpful. AFAIR, pretty much everyone here has done their runs in 4th right?

 

Yes AFR can be done from the tail..when I read longterm and saw the percentage, I thought he was stating longterm fuel trim, which is in percentage..I misread the error

 

It's done in 4th gear for manual trans are 1:1 ratio..if not very close to this ratio

 

Wow, I wuold of thought, they'd at least used a fan..oh well

If the fault wasn't present prior, I'd just drive and see if the fault comes back again before going further diagnosing it..

My own 2cents..I would source a new dyno, mustang dyno or equal on 4wheel.. just if taking a dyno for before-and-after views..both dyno runs should be at the same place on the same dyno

 

I've never heard of running a dyno without a fan--very strange.

 

Just thought I'd post an update on this one. I haven't given up on documenting the gains as I install mods. But, based on the experience I had with the first guy, I thought it would be worthwhile to search out a more reliable operation (in the end the guy stopped returning my emails and never did send me the charts of the pulls we did).

Took me a while to get organized but I found a well established place in the GTA that does a lot of exotic and race tuning and have a monster of a Mustang Dyno installed.

Just repeated the baseline yesterday and got very reliable numbers in the 312-315 hp range, torque 251 ft-lb at the wheels (parasitic losses also measured and logged). AFR was also repeated. Oh and no engine codes (I can't believe I let the other guy do pulls without a fan running ). I'll post videos and pics of the charts once I've got everything together and have post-pulls done with the mods.