David Brown

Is there anyone who has tuned an Accel DFI6. I need to do some changes and not sure what to do?

efiguy

iTrader: (2)

Call Dave at Autotrends in California, he's probably the most well versed on that ECU.

Ronny

iTrader: (1)

Can you access the owners manual?

efiguy

iTrader: (2)

http://info.accel-ignition.com/accel.../software.html

Do you have this to start with?

ASE doc

My advice is install a wide band O2 sensor and use the ECM's record function to log the base fuel map. Do this only after you have set a base line tune that allows you to drive the car. You can do this by using the baseline calibrations as offered from ACCEL's public download site, or you can use the injector sizing calibration function in the UTILITIES menu. Be sure to go low(35%?)on your HP estimate or you'll end up very rich to start with.

Start with light throttle runs from take off to 40 mph. It is best to use datalogging which you can do using the software that comes with your wideband O2 controller. It would be helpful to have an input from the ECM into the datalog, such as RPM, so that you can correlate the datalog from the wideband with the recording of the base fuel map. You could do this by using a wideband that allows analog inputs and connecting to the tach lead at the coil.

Otherwise, you just have to keep an eye on the wideband AFR meter while you drive. Either way, stop after a short drive and watch the recording to see where the base fuel map has been. The gen 6 has hot keys that allow you to perform different functions. One function is "ghosting". I believe this is the "G" key. If anyone knows better, please correct me. I'll read my hot key sheet tonight and correct this myself if I'm wrong and no one else corrects me.

By using the ghosting function, you can see where the base fuel map has been during your drive, just like using record. To make changes to the base fuel or any other map, just hit the E key and you can edit cells. No need to even shut the engine down,. When done editing, just hit the Q key and the map reverts to the trace function where it tracks as you drive. Keep your changes small and change only a small area of the map at a time so you don't get too far off. As you get the base fuel map where it needs to be, you can also fine tune the timing map, assuming that you're using an electronic ignition( definitely preferable). You can also fine tune start up fuel, warm up enrichment, and acceleration enrichment, all as needed. Remember though that the base fuel map is god and these other enrichment maps are only intended to correct for certain conditions around a properly tuned base map.

A few basic tuning pointers: Max throttle, max load AFR is generally ideal around 12.5:1. Err to the rich side as this is much more forgiving. You lose noticable power and risk engine damage at 13.5:1, you lose almost almost no power at 11.5:1 and risk no damage to the motor. 14.7:1 is stoichiometry, or perfect combustion(there are a few reasons why this is not ideal for max power) 14.7:1 would be ideal for light throttle cruise. You will likely find as I have that the gen 6 due its limited 8 bit structure and the resultant large map cells, is hard to get real clean. You will end up a little rich or a little lean, stay to the rich side for safety sake.

Once you get your fuel maps set up for best performance and reasonably close to stoich at cruise, you can use the heated O2 sensor that comes with the gen 6 and activate closed loop in Configure ECM. In closed loop, the ECM's fuel trims will run the system as close to stoich as possible in cruise coinditions. You can adjust closed loop enable parameters in the configuration(closed loop minimum temp, closed loop max throttle, etc.). By calibrating these factors, you can have closed loop fuel trim while still having full power fuel when you want it.

A good starting point for ignition lead is whatever idle advance lets the engine run decently smooth(mine idles at 23 degrees due to the huge cam), and generally about 29 degrees at 2,900 RPM. You can tune from there. Just be careful to pay attention for any detonation. The gen 6 allows use of the ESC knock retard module and knock sensor. I can't use them because my valve train creates too much noise and puts the system into full retard immediately at full throttle. Fortunately, I've tuned enough beasties that I'm very aware of the sound of pinging or spark knock. Allowing an engine to ping is a quick way to destroy it. The gen 6 also has idle spark which you can use to add spark lead to help smooth out the idle. As soon as you step into the throttle, the timing reverts to whatever spark map you have designed. I myself have never felt the need for it.

ASE doc

Okay, I found the link to the hot key page for the ACCEL DFI gen 6. The T key takes you directly to the timing map. The B key directly to the base fuel map. The A key directly to the acceleration enrichment tables. The / key acivates the ghosting function, not the G key. V key activates the virtual dash which is very useful for diagnostics as it lets you see real time data from all of your sensors. I used it to find an open IAT sensor that was causing my engine to run rich.

efiguy

iTrader: (2)

Good info ASE, I'm not as well versed on the Gen 6 as I am the Gen 7.

But I have to ask, in your signature it says, balanced @ 6K, is it not balanced once you hit 6001rpm? I think maybe you were given some bad info.

Thanks for your input.

ASE doc

I hope I wasn't given bad info. Ive only been doing this for 40 years. Actually, the rotating assembly was dynamic balanced at 6,000 rpm. This is the the point where the assembly is perfectly balanced. This is done on any properly built motor that will see extended high rpms to provide maximum stability and durability at high revs. The fluid damper absorbs harmonics and keeps the assembly smooth throughout the rest of the rpm range.

Gen 6 isn't that bad to tune. It just requires a little more work. Since the gen 7 has a wideband O2 senor in it's structure, isn't it pretty easy to tune?

ASE doc

I'm afraid my description of tuning the gen 6 is missing some info. First off, when tuning the base fuel map, start out with light throttle as I said and make small changes to only a small area of the map at a time. The map is 16x16 cells in size with the vertical axis being MAP(manifold absolute pressure) and the horizontal axis being PRM. You will find that as you drive, the trace starts out just below midway on the vertical axis and of course at lowest side of RPM. You will start your tuning in this area and as you make changes to the map you will see the changes on your air fuel meter. As you work your way towards WOT(the bottom two or three lines on the map), be sure to stay at 11.5-12.5 AFR. Do the WOT runs in small increments, keeping rpms down as you make your corrections then working your way up. Finally, you will make full throttle runs through the engine's power band and can make small corrections as needed. Because the maps are large in speed and map, ACCEL designed the system to compensate for the big steps by blending cells. Therefore, as you make changes, you will notice that the engine's AFR in one cell is affected by changes in adjacent cells. The base fuel map has a "graph" feature that lets you graph the map where you can see it in 3D and look for any ares that are way low or high. These will generally areas where AFR will be off.

The gen 6 GLOBAL ECM Configure table has many features such as rev limit. This is a fuel cutoff safety valve against breaking your motor should you miss a shift or otherwise severely overrev the motor. I strongly urge you to install some sort of ignition module that contains a soft rev, I use the MSD Digital 6. Set the soft rev about 300rpm or so below the fuel cutoff. Believe me, the first time you hit fuel cutoff on a full throttle pull, you will understand why I say this. It's like having some invisible force slam on the brakes when you least expect it and your face just about hits the steering wheel. This is really a bummer in the middle of a race as it instantly slows your car and by the time you recover, you opponent is gone. The soft rev just stops the engine accelerating and holds it right there until you wake up and grab the next gear. You still lose time but at least not quite as much. ECM Configure also lets you set base fuel map size, max MAP( 1 or 2 BAR for N/A or boosted applications)if you are not running a blower or turbo, select 1 BAR, along with max rpm for the base fuel map. You'll see that max rpm is pretty much the deciding factor of cell size. Changing cell size will also change max rpm on the map.

On the timing map. As I said, start out with 29 degrees at 2,900rpm with around 36 degrees max lead at max rpm. You can tune from there. I run 32 degrees at 3,000 and 42 at 6,500.

The gen 6 has a very usable timing map which makes timing adjustments easy. It's designed to work with GM EST. I know that mine plugs in to the GM small cap(external coil) HEI. As far as I can remember the harness comes this way. ACCEL makes the 300+ Race ignition controller with soft rev. I ran this ignition for several years until it quit on me out of nowhere. My diminished faith in ACCEL's newer electronics led me to use the MSD unit to replace it. The MSD is not plug and play with the the GM electronics but using GM weather pack connectors I was able to fairly readily adapt the MSD module to plug right in to the ACCEL harness.

The ACCEL DFI gen 6 employs a Motorola ECM very similar to the early GM units that came in the third gens. It is a very durable unit. It does not have self diagnostic capabilities but if you familiarize yourself with what normal sensor data should look like, you can easily spot any faulty sensor or circuit by using virtual dash.

I built my own engine harness, using parts of the original, to work with the DFI harness and provide for dual fan control and to operate my monster dual pump fuel system. Remember that any electrical work you do will be the biggest limiting factor in your car's reliability. My system has run pretty much flawlessly for 14 years since the original build because I took great care in building and routing my harness.

To tune the gen 6 you need to find an old laptop running Windows 98 or 95 to run the DOS based Calmap 6.2 software. Newer OS's will not work, even with serial patches and though the sotfware seems to load. I ran into this after my old Windows 95 laptop was stolen and I tried to use a newer DELL running XP. The software seems to load and the ACCEL screen even comes up but the ECM will not communicate. Fortunately, old units running 98 are out there and cheap. I bought an old Gateway for $50 and it works great.

As far as overall tuning of an engine, if you are not familiar with the basics, read. You can find many informative articles on the internet and there are many good publications that cover the subject(HP Books). The more you educate yourself, the more comfortable you will be with this process. Of course this whole process is so much easier on a dyno.

efiguy

iTrader: (2)

There's no doubt that you're a intelligent person. However someone gave you some very bad info when it comes to balancing.
I've balanced over a hundred crankshafts, none of which were spun at anything more than about 600 rpm, not 6000. I've never seen or heard of a balancer that will actually spin a crankshaft 6000rpm. That's ridiculous, and dangerous. Any idea how Nascar balances their tire/wheel combos? With a tire balancer similar to the one your local tire store uses. And it spins it at about 35mph, not 200. It wasn't that long ago when they used a simple bubble balancer. See my point?
If you have crankshaft harmonics problems then the first solution is to balance it heavy, as in using more than 50% reciprocating weight along with the 100% of rotating weight calculation you would normally use in the bobweight. If you experience issues beyond that then you probably have a crankshaft design problem.
And again, if it's balanced to 6000rpm, if you go to 6001 it's no longer balanced? I don't think so.

And sorry but I don't agree at all with your recommendations on setting his timing table, 42 at 6500, really? Did you dyno it? Did it really want that much at that rpm? I'd be very surprised if it did but that's another topic.

And yes the Gen 7 uses a wideband and I use it to tune the fuel map correctly, then I drive it with it turned off. If my tuning is right on, and it normally is, you won't notice any real difference. But it's a good idea to leave it on just in case you run it to a lean condition and it has to add fuel.

Note; the Accel Wideband/Datalogger will send a narrow band signal to any ecm all the while showing the real air/fuel ratio. Very helpful in tuning systems that only accept a narrow band O2 signal.

ASE doc

Thank you for not impuning my intelligence. I am not a machinist. I am a master automotive technician and I specialize in runability and engine performance. I have done so for 22 years of my 40 years as a mechanic. My info may not be beyond reproach, but I build and tune some very fast cars and seem to figure out and correct engine performance issues on every make and model of car that comes to me so I must be doing something right.

My information on crank balancing comes from alot of studying back when I was building motors for a couple of local NASCAR NW racers. Hot Rod magazine published an article on the subject in about 1994 and Smokey Yunick's column in Circle Track magazine touched on it once.

I use a local machinist Archie Somers who specializes in NASCAR small blocks. He's been in the business longer than I have and he has probably built thousands of 700+ hp N/A small block chevys. On any given day in the off season, he has a line of five or six motors ready to go out the door with dyno tags reading something like 720HP at 7,200rpm, and a few more in the process of going together. He's done the machine work on several motors for me and he did the rotating assembly and block prep on the motor in my signature. When I asked him about dynamic balance at 6K he never questioned it. I'll ask him about this later today to be sure.

I'm not stupid enough to think that the crank was actually spun at 6,000rpm on a lathe, and yes I know that tires are not balanced at 200mph. The point of balancing for 6,000rpm as I remember it is that this becomes the rotating assembly's ideal speed so that stress is dramatically reduced when an engine is run past 6,000rpm. Not that it is out of balance beyond this point. You obviously know more than I do on this subject and I don't want to hijack this thread anymore than we already have so I'll drop it and talk to my machinist to get the story straight. Thank you for bringing this possible mistaken idea to my attention. When I have more complete information, I may take this back up with you in a PM. In the meantime, I will delete that part from my signature to avoid confusing those who follow our lead.

As far as my timing curve is concerned, no I haven't dynoed the motor since it was first finished. But I hope you're not suggesting that the same ignition lead that works at 3,200 is also going to be best at 6,500. You realize that the flame front only develops so fast, even while engine speed and thus piston velocity increases. Unless timing increases with engine speed, efficiency will suffer. 42 degrees seems to work best as a max point at 6,500rpm. I have no detonation and I noticed a slight reduction in top end torque when I backed the timing off to 38degrees. When I have a chance to dyno the car, maybe I'll change it.

efiguy

iTrader: (2)

I would recommend dynoing it.
And for the record, I've redone dozens of tunes from guys who were engineers, longtime car guys etc. When it came to spark curves most didn't have a clue. Some think because you CAN give it anything at any rpm that it actually WANTS that, very seldom is that true.

Thank you for your feedback.

ASE doc

EFIguy, I guess I should thank you for correcting me on my crank balancing misinformation. I wish I could find one of those old articles to recheck what they were actually saying. Somehow, I really misunderstood. I guess Archie didn't really catch what I was saying. He just balances all cranks that will see much time above 6,000rpm to 1 gram. He's done a few for me too. I now understand what you were saying about counterweight being equal to 100% rotating weight + 50% reciprocating weight + oil.

I really do want to dyno tune my engine. I've just always used seat of the pants and a stop watch in the hand of a passenger to estimate power gains. I've also used a passenger to monitor the base fuel map in lieu of data logging. Trouble is, my passenger is usually too busy gabbing the door handle to really pay attention. The AFR meters that became available in the past few years help, at least with fuel tuning.

I'll get a better idea of the car's performance and maybe get to do some tuning tweaks when I get back to the strip this summer. I should say, when I convince my wife to let me take the car back to the strip. Last time I broke my transmission. The old trans was 14 years old anyway and was obviously due for a rebuild. I'm trying to convince her that the new trans I built will not break like the last one. (I guess that doesn't mean that the rear axle won't but I don't have to admit that to her.)

To the OP, I just realized what car you're talking about. A Gail Banks 500HP twin turbo car. Very cool. I remember seeing those come out in 82. I wasn't aware that they used the ACCEL DFI gen 6. I'm betting that they probably run an earlier version and that it may take an earlier software version too. What changes do you need to make? Have you tried connecting with calmap 6.32? If it works, then my instructions as imperfect as they may be will get you going in the right direction. If it won't connect, you may have issues.

To connect, assuming it is basically the same version of gen 6 that I have, look for a flat four pin GM weatherpack male connector about 1ft from the ECM. I assume that Banks mounted the ECM in the factory location behind the right side dash where the glove box might have been.

David Brown

Thank you everyone for the help. I have set the car up to take 2 degrees of timing out of it for every 1lbs of boost. I have started to add some timing back into it with the add of methanol. I think my issue might be the advance I am getting from the distributor module. I think they make some aftermarket ones that can lock the timing.

ASE doc

Does the MSD you're using have a built in timing curve that works with the DFIs spark control? The gen 6 I run works with the HEI module like factory EST. My MSD digital 6 is only an amplifier with a rev limiter built in. It doesn't affect timing.