I have a Camaro with a fresh 454; aluminum heads, roller cam, etc, etc. The most interesting part of the setup is the Accel Gen 7 DFI (digital fuel injection). I am trying to tune with the laptop and it gets kinda confusing sometimes. There are LOTS of screens with an infinite number of combinations.

The car actually runs fairly well using a baseline 454 map that came with the software, but of course, I still need fine tuning.

The instruction manual that comes with the DFI isn't very good, IMO, and I'm trying to find something better. Does anyone know of any well-written basic instructions for tuning the Accel DFI??

thanks

 

I know most anything you'll need to figure out. Think about it and form some solid questions. I'll do my best to help.

 

Thanks for the offer. I have the wide-band O2 sensor, so that helps. Couple of questions for ya:

1) How do you ascertain the correct A/F ratio? It seems most fuel adjustments are made in the VE table, to get the engine to correspond to the desired A/F ratio table. But how do you actually know what the A/F ratio should be? Should I mess with the A/F table first, or the VE table?

2) How do you use "data logging"?

thanks

 

The idea is to turn off most/all of your fuel corrections and just tune the VE(although your wideband version can automatically adjust it for you).

You really need to try different AF ratios out and see what it likes. For a large cammed engine, I would start with 15:1 at idle, 13.5-14.0 at part throttle and 13.0 at WOT. Highway cruising (@ light loads) might like 15:1 for better MPG. Those numbers are a good place to start but every engine is different....



Go to the datalog tab, go to configure and run. Then you'll see options. Stick with manual triggering, that way you control when logging starts. Make sure you have file length long enough for what you are doing. Then you'l need to setup the sensor/value you want to log. There are 6 imput line which means you can log that many things at once. After you configure logging then hit the record button to log. Use the graph session option to view you log files. I can't really explain what to look for in the logs. That just takes time and experience.

Try reading the instruction manual several times to understand things better. Many of the tables are like the GM stuff so you can even search diy-prom for table explanations. Do as much research as possible before asking questions, that'll help you greatly.

 

Thanks for the tips, but my question still is: do you tune the VE table first or the A/F table?

Or perhaps this?? start with all corrections off, as you say, and tune using VE table til it runs nice. Then watch A/F reading and adjust A/F table to that reading? Is that the method?

thanks

 

Nothing else matters until your fueling is modeled correctly. Everything depends on the VE table being accurate.

When the engine is warm, put some safe values into your Target Air:Fuel table and dial in your VE table until you see those same values on your wideband. Do this using closed loop fueling correction and try for the least possible O2 feedback correction percentage -- less than 5% is a good number to shoot for initially.

 

since you have the wideband, just autocal the VE table.


http://www.accel-dfi.com/AskTechResu...dID=8&ID=64382

 

LOL, thanks. That was actually me that had posted the question to Accel tech. I still don't understand the answer, but it sounds like it would only do one cell at a time, so I never bothered to try and figure it out.

thanks for the link

-

 

It will do one cell at a time. You just need to hold the engine at X load and RPM long enough for it to make the VE correction. I didn't have the wideband option so I just tuned the VE and ignored everything else, while using my stand alone wideband. Put all the entries in the AFR table to 13.0 . Then drive around adjusting the VE to net 13.0 . That's what autocal does for you....

 

13.0 is too rich for light-load driving isn't it? Most things I've been reading say 14.7 or even 15.0 for light load.

So it seems the A/F table needs to be scaled and that's where I get confused. But I got just enough knowledge to be dangerous now, so I'll just try playing around.

thanks

 

It is too rich. I have suggested AFRs (for various loads)in a couple of post up.. Putting it all to 13.0 will allow you to dial in the VE table much faster. Otherwise you'll have to figure out the targe AFR in order to match it while tuning through the VE table, for each load value..

Following me?

 

Man, sometimes I just feel stupid. But I don't get it.

If I put the A/F table all at 13.0, then I am adjusting the VE table for a too rich setting for much of the table. I mean, I'd be basing corrections on the 13.0, which would often be too rich, so I don't understand how this would help speed up the tuning, as I would have to lean out the VE and A/F tables at some point.

I'll just use the Accel baseline A/F table and tune off of that for now. Car actually runs pretty good in closed loop mode and I haven't even touched the map file, other than set TPS points. I can see it adding fuel for most light load driving, with A/F reading about 15.0 at light loads.

The only other thing I really need to set up is the IAC valve.

thanks

 

You put it to 13.0 just to tune the VE table. Then start to play with different a/f ratios. That's AFTER the VE table represents the true pumping losses of your engine.

I know a bit about IAC....

 

Thanks for the explanation. I think I'm actually starting to get it.

I looked at the manual for directions on setting the IAC. Is that sufficient, or any there any secrets to adjusting it?

thanks

 

Hope you don't mind if I jump in, but I figured I could help your comprehension.

If you put in a target AFR of X (say 13.0:1), and you correct your VE until the WB reports an actual AFR of X (say 13.0:1), then you VE table CORRECTLY represents the actual VE of the engine. This means that if you change the target AFR, then your actual AFR should change to this amount. You do NOT have to lean out the VE tables later, just the target AFR tables. You can dial in your VE, in theory, with ANY target AFR. It's just that the engine wouldn't run so well at 9.0 or 18.0 (probably bad enough to cause false WB readings). Make sense?

If the DFI has a table for AFR vs coolant vs RPM, then you could put in anything you want (a nice sweep from lean to rich from idle to WOT would be good) and dial in your VE that way. It would work the same exact way as above, since as long as you match the target (commanded) AFR with the WB measured AFR, you have the correct VE for a given RPM and load.

 

Kevin

Thanks for jumping in. I noticed your sig. You live in Middletown, RI? What are the odds on that, as I also live in Middletown, LOL.

Can I buy you lunch sometime and pick your brain?

thanks

Dave Fraser
Middletown, RI
743-2431 cell

 

I would begin with the IAC start position. You want to raise the value until the engine initially revs a bit over target idle RPM, then lower it a hair. I'm talking about the second your RPM gauge starts to register RPMs.If that setting is too low, the engine will kind of stumble up to the target idle speed(when starting). If the settings are too high, the engine will rev over the target and then go to it. The idea is to have the engine RPMs slightly OVERshoot the target upon initial startup.


...at least that's where I would start. That table is based off coolant temp, so you'll have to adjust it cold and warm. Then smooth out the rest of it.

 

I would begin with the IAC start position. You want to raise the value until the engine initially revs a bit over target idle RPM, then lower it a hair. I'm talking about the second your RPM gauge starts to register RPMs.If that setting is too low, the engine will kind of stumble up to the target idle speed(when starting). If the settings are too high, the engine will rev over the target and then go to it. The idea is to have the engine RPMs slightly OVERshoot the target upon initial startup.


...at least that's where I would start. That table is based off coolant temp, so you'll have to adjust it cold and warm. Then smooth out the rest of it.

 

DP

 

That's fine, but I've never touched an Accel DFI ECM. I can help you with tuning theory, however.

Hmm, lunch. I like lunch. I think we could arrange that sometime.

 

These are the Accel manual instructions for setting IAC. Is this similar to what you suggest?


"The position of the throttle blades relative to the position of the Idle Air Control Motor actuator plug must be set correctly. The relationship between the two is critical in controlling idle, acceleration, and deceleration characteristics of the motor. A brief description of operation will help you understand how to adjust this function. The function of the IAC motor is to bypass air around the throttle blades. Since the starting position of the throttle blades does not change, the IAC valve position changes to compensate for changes in Idle demand or load. When the IAC opens, it bypasses more air around the throttle blades and when it closes, less air is bypassed.

Under certain conditions, usually during cold idle, the throttle body will emit a high frequency hissing sound. This is actually caused by the air reaching sonic velocity traversing through the entry hole in the throttle body. This phenomenon can be monitored as the engine warms up. As coolant temperature (ECT) rises, demand or load decreases, causing the IAC to close. The ideal setup would bypass the least amount of air during no load conditions.

To properly set this relationship, make sure the engine is warm and at operating temperature. Access the Target Idle Speed table in Calmap. Adjust the values in the table to best fit your application. Ordinarily, idle speeds will generally increase as coolant temperature decreases. Target idle speeds will also need to increase with increased camshaft duration. Consult your cam supplier for further information. Next, check and verify that all accessories are off, the transmission is in neutral or park, and the parking brake is set. Select the Minimum IAC position vs. Coolant temperature table.

Set the value at current engine temperature to 5%. Monitor the IAC position value at the right side of your screen. Adjust the throttle blades to bring the IAC position value to 6%. If the target idle speed does not match the engine idle speed when the IAC position is set, then the throttle bores are distorted, a vacuum leak is present in the intake manifold, or the throttle blades need to be drilled. Once the throttle blades have been adjusted, the TPS Set Points must be re-calibrated. To reset these tables, refer to the TPS Set Point, Low, and High Offset Voltage tables in the Configure ECU section. For further tuning or calibration information, reference the Calmap Tuning section in this manual. "