Hey folks,

Anyone doing this? I just put a new set in and was looking for someone's success. Did the basics (smoothed out spark tables, reset FI sizing, etc). It runs very nice, but I was looking for a head start on the fuel tables and such. Anyone have some raw material (ie. bins you're pleased with)? I'm going to start plotting the data this evening and see what I was getting. Little knock up high I need to get rid of, otherwise pretty stiff! Runs a lot smoother now compared to the 150k-mile 19# set I had on there before.

Thanks,
Craig

 

With ARAP I was getting knock at full throttle at about 2800-3800 RPM. I pulled some advance out and I need to run a scan again to see if that corrected the problem. I have the screens out of my MAF and there were a few areas where the BLM were real high. I adjusted the injectors constant down to get it in the ballpark. I anticipate having to mess the MAF tables to get it where I want it at cruising because I think most of the MAF BINS were designed for stock a MAF with stock filters.

I'm not looking forward to messing with the MAF tables.

That's my experience so far.

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87 Iroc 5.7, AFR190, SLP Cam(218/224), SLP 1 5/8 headers & cat back, Random CAT, SLP Runners (matched intake-runners-plenum), 48mm TB, 6E(arap) chip, Vigilante & Probuilt trans.

 

Yeah, I pulled out some timing as well. Running 160 stat, went ahead and smoothed out the total advance curves, placing a cap of 38 deg total. Looks like a plateau now. Pulled real hard all the way through now, very little if any knock counts (1 or 2, just from engine noise).

I pulled FI sizing down to 22#, this is with 24#SVO at 45 psig, vac compensator hooked up. I thought it would call for 27#+ setting, but so be it. Fuel-trim BLMs are still coming in around 130-140. Also bumped my AFR to 14.8 for what its worth. Runs like a champ though. I'm definitely looking forward to screwing with the MAF tables. There's got to be some goodness in there. Maybe if they are set right, the FI can be set right as well, have some true information in there instead of all these fudge factors.

 

It occurs to me that modifying ie. gutting a MAF sensor will cause MASSIVE errors in the MAF calibration tables. I mean, if you cut out the screens that's one thing, but if you cut out the fins, then that removes the restriction in areas other than the venturi zone, so the air now dumps around the hot wire instead of across it. I'm going in to change my scalar multipliers tonight, I want my real FI sizing to be in the code, and I want the MAF tables to correct for this now obvious bias that my readings have been suffering from for so long now. No wonder my BLMs have been consistently high!

 

On further thought, after starting to dig into the MAF scalar multipliers, I'm going to take the other approach. Rather than mucking up the tables beyond recognition of any of today's popular editors, I'm going to LIE to my poor ECM and tell it that I have a much smaller fuel injector in there than what I actually have (on the order of 21# instead of more realistically 27#).

By lying to the ECM, it should pretty effectively compensate for the fact that the MAF is reporting lower-than-actual rates. Assuming this brings the BLMs in line, which I think it will, then the resultant ratio of reported-vs-actual effective FI size should give the relative partitioning of air into the annular non-measured region of the MAF sensor compared to the stock arrangement. No harm done, just need to remember what the heck the deal is when i come back later.

If there are nonlinearities in the MAF air partitioning away from the measured cross-section with respect to total flow, then I'll probably have to tune through that as I collect BLM data. This will then justify messing with the tables.

This brings to bear a rather important application note: What is all the fuss over trying to make your MAF measure high rates? Who cares what the real rate is? Just put a big piece of pipe in parallel with the MAF with an adjustable orifice perhaps, and LIE to your ECM about how big your fuel injectors are, tell it they are smaller. Do a couple of iterations with the FI specification to get your BLMs in-line, swap in a couple of orifice plates to make sure you're getting relatively full-scale readings or as you like, and go with it. Should be a no-brainer in the end, get all the flow you want with MAF. I've seen many a discussion along the lines of enhancing the range of the MAF, and maybe some hints in this direction, but I believe this is the end-all be-all. And if you're REALLY worried about nonlinearities, screw it - forget about the pipe, just put two of the MAF buggers in parallel and just use one.

For what it's worth,
-Craig

 

I have to admit, that is a very creative idea. I don't have a MAF car, but when you think about it, what would happen if you installed a MAF that registered half the value of the normal MAF so max was 512 and just halfed the injectors...the MAF would be giving you half the reading but the injectors would read double.

The only difficulty would be the reduction of the "resolution" by half...but if you have a need for more than 256...this may be a solution.