Fuel Comp. Chip Upgrade


Let me start out by saying that I generally don't fool around with fuel chip upgrades. I have tried chip upgrades in the past and have been disappointed. Three of my experiences with chips involved piston engines... and I really couldn't tell that the chips made any difference. I also tried a chip from SuperChips in a 2nd Gen Rx7 and couldn't tell that it helped much. I'm not saying that the chips didn't perform as advertised... just that I couldn't tell a seat-of-the-pants difference (and in my book that's what matters).

I recently ran across an article in Grassroots Motor Sports magazine (great magazine!) that commented on a new fuel chip from SAS Racing in Florida. I was suspicious but the idea behind it made sense and it boasted higher gains than the average chip. Apparently, SAS developed the chip with another company called MD Racing. I also suspect that SuperChips had some involvement in it, but I don't know for sure. I called SAS and talked to a patient guy named Carl. From what I have been able to piece together, the chip modifies the ignition timing and changes the fuel curves. It may do additional things that I'm not aware of, but those are the major mods. I also believe that they are greatly advancing the timing at low rpms, and backing it off as the revs climb, which should be a safe thing to do. Excessive timing advance will kill a rotary, but only at high rpm. They claim a 25 horsepower increase and a 25 ftlb increase in torque. Carl also mentioned that they were seeing a 46 ftlb increase in torque at 5700 rpm.

They offer a 30 day money-back guarantee, so I decided to try out their Autocross chip (it boasts the highest gains). I removed my fuel computer, shipped it to them, and got it back within a few days. When I received the fuel comp. I cracked it open to see what they had done (I'm an electrical engineer, so I'm naturally curious about such things). As I suspected, they had replaced one of the eproms that provides the data tables for the fuel comp operation. I was very impressed with the quality of the soldering work that was done. They installed a socket for the new eprom and the soldering job was very clean.

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The fuel computer after being removed from the car.

The fuel comp. opened up. The new chip is circled in red.

Before I removed my fuel comp, I checked the timing, idle, etc. and everything was perfect. I installed the modified fuel computer and started the car. It started easily and sounded good. I checked the timing and just about freaked out. It wasn't anywhere near the timing marks. I have a digital timing light with advance built in, so it was easy for me to determine that the car was running at exactly 15 degrees advance from the stock timing. After repeated calls/emails to MDRacing and SAS, I found that that is the way it is suppose to work. I couldn't get a good explanation from either company as to why it is that way (I'd really like to know). It must shift the timing somehow, because if you set the timing back to stock, the car will barely run at all. I don't much like that side-effect, but as long as you remember that your car's timing needs to be set at 10 degrees BTC (leading) and 5 degrees ATC (trailing) instead of the stock 5 ATC (leading)  and 20 ATC (trailing) then you'll be ok. The car also wants to idle a few hundred rpm higher that it used to, which doesn't bother me. I haven't tried, but I'm sure the idle could be set back down if one desired to do so.

As for performance... I was impressed. There was definitely more torque in the low rpm range. Also, around 6000 rpm there is a extremely noticeable increase in acceleration. There is a definite seat-of-the pants difference here. Read below for a less vague measurement of the performance increase.

A good way to see how modifications affect your car is to do a few 40-70 runs in 3rd gear. This allows you to use almost the entire useable rpm range of your engine and since you stay in 3rd gear the whole time, it eliminates driver input as much as possible (some people shift quicker/slower than others). So, find a nice piece of deserted interstate, as flat as possible and hold your car in 3rd gear at 40mph. Start a stopwatch as you punch the accelerator and stop the watch when you reach 70mph. Some people like to start about 30mph and start the watch when the needle crosses 40 (kind of a running start). It doesn't really matter what you do, as long as you are consistent. This test is good for seeing how your car's time changes as you make modifications. It really isn't good for comparing two cars unless you run in the same direction on the same piece of road. Also bear in mind that air temperature will affect your car's power. Try to make your runs about the same time of day. Early mornings are the best. Finally, be careful. Now that some roads have a 70mph speed limit, you can do this test without breaking the law!

This chip cut my 40-70 time by almost a full second.

Now for some notes:


I've also decided to include a quick set of instructions on how to remove the fuel computer:

  1. Disconnect the positive terminal of your battery.

  2. Remove the five screws holding the passenger's side door sill in place. Its the long plastic piece that runs along the bottom of to door frame. Pop the door sill off. Be careful. It's pretty sturdy, but you could break it.

  3. Remove the passenger's side kick panel. It is the plastic panel on the right side of the passenger's footwell. Use needle nose pliers to remove the three press-in plastic holders that keep it in place.

  4. Peel the carpet back to reveal a large steel cover that protects the fuel computer. (see pics below)

  5. You'll need to remove two 10mm nuts at the top of the plate and two 10mm bolts at the bottom. Then slide the plate out.

  6. The fuel computer frame is held in place by several 10mm bolts and nuts. Remove them and then unplug the three large wire harnesses from the computer. Then you should be able to remove the computer

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The fuel computer cover plate.

After removal of the fuel computer.