Accel Enrichment
 

As I have stated before, I have worked with HP Tuner software for Corvettes for quite sometime now, and I find mysef trying to find correlations between the GM ECU and the Evo ECU. I am hoping that someone may already know the answers to these questions, so that we may be able to get a good help file created for the Ecuflash software.

The first topic I want to touch is the Accel Enrichment table.

In other applications, I have found this table to be referred too as the Power Enrichment table. However, I am not saying that this is what this table is as, to be honest, I am not certain what it does yet. So, does this table act as a multiplier to the stoich value and apply it as a modifier to the fuel value when operating in open loop? For instance, with a vette, you can simply perform some runs and get an average value of your AFR histogrammed out at RPM and MAP. So lets say that you find you are rich from 3800-5200rpms and you want to lean it out a bit. All you need to do is open the Power Enrichment table and adjust accordingly. Lets say I want to hit approx 13:1 afr. All I need to figure is that the car wants to run 14.7 at closed loop.So now I want to modify that number, in open loop, to run at 13. I would simply modify my PE table at the specific RPM and give it a value of 1.125, since 14.7/1.125 ~ 13.0. Now once again this is a target and there are a few other tables that may modify this value, IAT modifiers etc.

This makes tuning the vettes very easy since I dont need to go an fudge with a ton of fuel points in the main map. I can simply leave those alone and just focus on the enrichment modifiers, which gives me better response and a better tune in the long run.

Does the Accel richment table work in this same manner? And can someone provide the formula that is being used by any or all of the tables by the ECU to mod the fuel mixture?

Thanks!
Chris

I've been wondering the same thing also. I was going to add in a small value to a certain RPM point and see if there is a difference in fueling but my laptop is 40 miles from me.

I am going to do some expermintation myself this weekend, but I am thinking it doesnt have as much of an affect on everything as I think. Especially since the values seem to be the same.

This is exactly how this works. I have experimented with this extensively and it works in the manner that you mentioned. it is a very useful tuning tool.

HiVolt

acceleration enrichment is this...

When you open the throttle real quick from low throttle position, say around 15% or so, your letting in more air faster than the ecu can compensate for based on MAF or manifold absolute pressure. This creates a lean condition for a moment until the injectors catch up. If you watch your afr gauge you can see this happening, at a low cruise if you all of a sudden blip the throttle, you'll see your afr jump lean then back to richer. Acceleration enrichment is based off the throttle position sensor so it immediately will add a certain amount of fuel as you hit the throttle to compensate for the rapid change in airflow. I'm not sure how ECUflash is set up to use it but adjust it so when you hit the throttle from low rpm it doesn't go lean too much.

If your a carb guy, think of it as your accelerator pump.. When you tip in the throttle quickly, it allows you to quickly add additional fuel so you don't get a lean condition or stumble on sudden throttle changes..

This serves the same effect of "boost enrichment" on the MAFTPro speed density conversion piggyback. I am certain either variable would produce similar results.

Got it! Thanks guys!

Two questions:

If one upped to a larger throttle body, accel enrichment would be something that would probably have to be adjusted, correct?
Ditto for an upgraded intake manifold?

l8r)

Yep, the odds are pretty good that you'd have to adjust it.. the larger throttlebody and intake manifold would definitely alter the car's tip-in throttle response..

Thanks. {thumbup} ...another project begins :)

l8r)

Yah same here.. I'm in the process of fixing an exhaust leak on a vband clamp wiht my new turbo.. but I have a ported throttlebody and sheet metal intake manifold going on the car.. I have to retrofit the brackets for the OE egr solenoid, pressure regulator solenoid, provision mounting the OE map sensor and whatnot.. so I'll be doing the same sorts of adjustments.

would u increase or decrease the enrichment and across the whole spectrum or just a certain column?

It really depends.. at very low engine speeds you might find you need to decrease it.. but at higher loads, it would be the opposite.

i have blips at very low throttle and the a/f ratio will jump down to 12 and then go up around 17- thats why i wasnt sure which would cure it- taking away or adding

I also have stock ported 65mm throttle body and stock ported intake manifold