Flash tuning results on a stock 99 VR4

[Greg E]

Mitsu could have done a MUCH better job with tuning the 3/S out of the box. You would be amazed the HP potential these cars are limited to from the ECU. Thanks to the combined efforts of Ceddy and Gatecrasher in disassembling the stock 99 VR4 ROM this potential can finally be unlocked.

After months of patiently waiting for the snow to melt/salt to be washed away, i was finally able to get out tonight with the 99 and get to work tuning the tables in the ECU on my own car. No more asking others to take risks testing things out for me.

Few things to point out: My car is 100% stock. All emissions equipment still installed, stock air box (had to reinstall it), stock exhaust with all 3 cats, stock boost (controlled by the stock BCS), stock unrewired fuel pump and this is full weight car. With the exception of the rims, a forge closed loop BOV and 121K miles on the chassy, this car is just as you would have bought it back in 99.

The programs I use for flash tuning are ECUFlash, EVOScan 2.6 with a custom 3/S definition file and a dyno calc program called VDR 5.71 which uses your EVOScan logs to generate a dyno curve of your car. I had to add the gear ratios, Drag CoEff and Frontal areas for a VR4 to the program but that info was easy to find using Google. Been using these programs for years with great results!

Speaking of results, I had no idea how huge of a beast could be unleashed!



What you're looking at are the before & after results of about half a dozen pulls in 3rd gear on a few back roads. The blue/red lines are the car with the stock tune, the yellow/green are after my tune.

Note: These are NOT actual dyno results, just a calculation based on RPM, time and a number of other variables (which you can see on the left hand side of the chart).

Yes, you're seeing that right. 47hp and 73 ft/lb gain in torque with just tweaking the timing, fuel and MAF tables. :muahaha: The ECU also has something called lean spool which I tried playing with a bit but I'm not sure if it does anything yet. More logging/testing will need to be done to confirm its function.

The first (base) pull was done on a flat stretch of road in 3rd gear starting at about 2700 rpms and holding the gas pedal to the floor till as close to redline as I felt comfortable going on the dark and narrow tarmac. The results were about what you expect on a stock car (225-230whp) so I was confident the variables I put into the program were going to be accurate enough. EVO guys have found this program to be within 5-10hp of an actual dyno but obviously, I'll need test this sometime.

After about half a dozen pulls on the exact same stretch of road we're left with a 47hp and 73 ft/lb gain in torque! This is a 0 knock tune on 93 Sonoco gas. Another couple degrees of timing got me a bit of knock so I had to back it off and settle with what you see.

My car has a bit of a stutter to it as well which I figure is from the old plugs, wires, fuel filter and injectors. So that's what you're seeing in the dips in the graph but even still, there's a HUGE gain in low end power! The butt dyno highly approves of this mod!

The weather is calling for flooding rains over the next couple days and I have other plans this weekend, so maybe early next week I'll reinstall the K&N open air filter and test the results. After that will be a full exhaust.