Grog

Guys -

I am considering a wideband O2 sensor setup to measure and adjust the AFR on my Whippled 502 MPI (5# boost). Since the injector duty cycle is fixed in the ECU mapping (I think), I would lean/richen by decreasing/increasing fuel pressure at the regulator. Is this logic correct?
Also, what AFR should I be running through the rpm range with this setup? Is it different than would be on a NA motor?

I appreciate the input.

Greg

Strip Poker 388

iTrader: (6)

I would not try it with fuel pressure. I would recal the ecu , use the wideband O2 sensor to find out the ratios at different RPM and loads.then have some one program it.

But !!!! I bet Mark at Precision Marine in LA has a Map he can put in your ECM that will work good. He has a lot of cals for that set up.

Try him at 504-469-2463 Mark Boos

Goodluck

Rob

Grog

Thanks Rob. I might end up doing just that, but first I would like to know if my fuel curve is already close to optimal. The only reason I question it is that my EGTs never get above 1200° F. I think I may be running a bit rich and wasting power.

Plane Silly

I have the Procharger set up that uses the FMU. I also have an LM1 and kept my F/R at about 12.5:1. I blew up the motor this season! The word is that the FMU is just to inconsistent. I now have a new motor and had my ECU reprogrammed to my motor specs and keep the F/R closer to 11.5:1. It runs much better and the A/F is much more consistent. Get your ECU reprogrammed!

Strip Poker 388

iTrader: (6)

Note .....on EGTs mine stock ran 1500 and sometimes 1600 by the lovise/gaffrig gage. there not real acurate!!! Also pump gas will run higher temps than race gas ,like most people judge temps by, Mine now never gets above 1200 at 9lbs of boost ...on the dyno steady state pull the max was 1325

theres some dyno sheets in the GD section if ya do a search.

Does your have the piggy back computer and the extra injector?

Grog

If understand what you are asking...Mine came with a full set of new injectors and then I had to have the original ECU remapped.

articfriends

iTrader: (1)

What your wanting to do could work somewhat as a bandaid approach. Lets say you install the air fuel ratio gauge and your afrs under boost are 9.5-1 to 11-1,you could lower fuel pressure a little at a time until you get it to 11.5-1 under boost at the leanest setting and it would clean it up somewhat. Now,if you discover your at 11.8 or higher though somwhere and below 11.2-1 somewhere else you can't lower fuel pressure to raise the lower #'s without raising the ones that are too high already without risking a meltdown. I did find on my motor Crockett set the afr's in the mid 11's on dyno under boost and they were closer to mid 10's when tested in the boat but lowering my fuel wouldn't have worked because there were a couple of spots that were almost 13-1 so it required re-programming on the water-the only way your going to do it right with a mefi-3 as there is no way to give it feedback or input for a "automatic" correction,Smitty

jdnca1

Our dyno guy doesn't care a bit about EGT's...he doesn't even measure them anymore. What he does measure is A/F ratio for every cylinder...his thoughts are if those are where you want them, then EGT's will be where you want them...unless of course you run a radical deviation (timing, etc) from the "norm". Most of the roots / carbed is set up ~12.2-12.5:1 with some motors having 100's of hours logged.

Grog

Agreed. If the AFRs vary much over the rpm range (which is probably the case), adjusting the fuel pressure won't work. If I plot AFR with respect to rpm and send it to Precision Marine like 388 said, maybe they can tell me if it looks good or a remap is what I need.
In any case....good stuff. I appreciate everyone's input.

Strip Poker 388

iTrader: (6)

That sound like a plan,does the afr meter have a record feature?