Technomotive EPROM Modifications

What is an EPROM modification?

The EPROM in an ECU contains the instructions that the engine computer executes. You can consider the EPROM as the "rulebook" defining how the ECU will react to any given situation. By modifying the program in the EPROM, we change the rules by which the ECU plays. This allows us to get around some of the more bothersome restrictions the factory imposes on the ECU, while adding some really unusual functions the factory could have never foreseen.

Available EPROM modifications

As you can see from the selections below, there is a lot of untapped potential in a stock ECU. We at Technomotive strive to fully understand the ECU code. That is why we can offer modifications that you will not find from any other aftermarket ECU reprogrammer.

We've grouped the modifications using the familiar aftermarket "Stage" classifications.

Type Modification Stage I Stage II Stage III
Convenience A/C Shutoff 1,2 1,2 1,2
Security 1,2ß 1,2ß 1,2ß
Display Codes 1,2ß 1,2ß 1,2ß
Speed Sensor 1,2ß 1,2ß 1,2ß
Gauges Oxygen Sensor 1,2 1,2 1,2
Spark Advance 1,2 1,2 1,2
Injector Duty Cycle 1,2 1,2 1,2
Battery Voltage 1,2 1,2 1,2
"Octane" 1,2 1,2 1,2
"No Limits" No Fuel Cut 1,2 1,2
No Boost Cut 1,2 1,2
Higher Redline 1,2 1,2
Drag Race Shift Light 1,2 1,2 1,2
Clutch Cut 1,2
Selectable Launch RPM 1,2
1 = 1st Generation (89-94)
2 = 2nd Generation (95-96)
ß = Currently in Beta Test
1,2ß = Available for 1G, but 2G is in beta testing

More information on each of the individual modifications is available below.

Convenience modifications

Imagine the following scenario. It is a hot, sticky, August afternoon. You've been running errands all day in heavy traffic. You've got the air conditioning on full blast, and it is barely keeping up. Finally, the last errand is complete and you are on your way back home. The traffic starts to thin out and the drive becomes more pleasant. You miss the last light right before the expressway, and end up first at the red light. On your left, someone pulls up and starts revving their engine. Well, you are not one to recklessly race on the street, but the road ahead looks clear enough - you decide to give the guy a lesson in 0-60 acceleration. You hit the light perfectly and launch well, but soon you hear a low pitched growling whine from the engine as its RPM goes over 4000, and the engine doesn't feel as strong as it normally does. You move to second gear, but get the same results - and you see a blur go by on the left. Ooops! You forgot to turn off the air conditioner!

Wouldn't it be nice if the engine computer turned off the air conditioner when the RPMs got too high or when you put your foot through the floor? There is really no reason why it can't - on the DSMs, the ECU has direct control of the air conditioner clutch relay! Not only are you robbed of performance due to the drag of the air conditioner compressor, but you are risking the health of the compressor by driving it at such high RPM. A couple people have actually had the compressor "explode" when they missed a shift and ended up driving the compressor at over 7000 RPM.

This is a perfect example of a convenience modification. This modification does not really affect performance of the engine directly (after all, you can reach over and turn off the A/C yourself!), but makes the ECU do something nice and convenient that the factory could have programmed in from the start.

Here are some simple things we've added that we believe should have come from the factory.

Gauge modifications

So you've installed a second boost gauge because the stock gauge is too inaccurate and doesn't have enough range. What to do with that waste of gauge? It sure is in a nice place. Its location right below the RPM meter makes it easy to keep an eye on it while drag racing instead of having to look at a gauge on your A-pillar or in your center console.

Well, we reprogrammed the ECU to display just about any sensor input or variable available to it. Here is a list of what we have tried and what people have been requesting to give you an idea of what can be done.

All the gauges above look real handy, and you can't make up your mind which one to pick. So why should you? This modification also allows you to select which of five different gauges you want to look at before you start your engine, using the throttle to make your selection. (Please note that once the engine is running, you are locked onto your selection until the engine is shut off once again.) The ECU will even remember your last gauge selection between starts. Read our instructions on how to use the gauge selector.

"No Limit" modifications

A funny thing happens when you start putting "go-fast" parts on your DSM... it fights back! Despite building one of the most bulletproof production four-bangers on the planet, Mitsubishi engineers played it safe and put a bunch of restrictions in the ECU code that prevent the tough little two-liter from attaining its maximum output. Not that the engineers don't like having a little fun - they simply got leaned on by the bean counters that track warranty returns. You see, the bean counters know that there are many people who are going to buy a DSM and completely neglect it. Never change the filters or oil, buy crappy gas, never clean the spark plugs... then take the car out and beat the living daylights out of it. So the engineers set the "safe" limits in the ECU to levels where even an abusive customer finds it difficult to force the car into an early warranty repair.

In the case of the DSM, this actually works out to a happy situation. The car has been detuned enough from the factory that it lies in a very attractive price range; it also gets classified in a better insurance price range. You can make your car faster than a good Porsche for less than half the price, and pay relatively low insurance premiums to boot!

As you upgrade the hardware on your car, the factory limitations start to hit you hard! "Why me?" you think to yourself... "I'm not one of those bozos that never changes the oil. I take pride in keeping my car in good shape. Why should I suffer the fate of the lazy and slow?"

We at Technomotive believe that you shouldn't have to live with these limitations.

Drag race modifications

CARB and EPA notice

These modifications only affect the car in "high-throttle" situations. Typically, exemptions are granted for modifications that only occur during "high-throttle" situations. In the case of the gauge or the shift light mods, smog related items are not affected at all. One would think that full smog testing would not be necessary, but until we get the full green light, we must say the following.

For off-road use only in California and other states that have adopted CARB rules. Not for use on any street-driven vehicle in these areas.

Restrictions and the gritty details

Please note that we can customize any of the above numbers to fit your needs, or implement any custom combination of the above.

All of the above modifications (aside from the clutch cut) use already existing equipment in your car. Your car will look absolutely stock to anyone else, even the dealer. None of the above mods will impact the use of any scan tools by the dealership (except for the security mod - the dealer will have to start your engine to run the scan tool! - but if you are worried about it, you can always pop your old stock EPROM back in for trips to the dealer).

The above modifications are currently only available for those ECUs that already have an external EPROM. To find out if your ECU qualifies, you can follow the instructions for the first generation and second generation DSMs elsewhere on this site.

These modifications are available on both the 1st and 2nd generation ECUs (some 2nd gen stuff is still in betatest). Both generations have been tested at the dragstrip.

These modifications have only been tested on turbo cars so far. We see no reason why most of these mods (except those specifically aimed at turbos) shouldn't work on the non-turbo DSMs. However, we will require at least one betatest iteration to insure there are no problems. If you are interested in being a non-turbo betatest site (2.0l and 1.8l engines), please let us know.

This performance modification involves removing your stock EPROM and replacing it with a high-quality, high-grip socket and a new EPROM with your choice of options. You will have to send us your ECU in order for us to socket it. This means your car will be unusable until we ship your ECU back. Please keep this in mind. If you want to minimize downtime, you can socket the ECU yourself - however, we offer no discount, as we do not recommend doing this yourself unless you are an expert.

TECHNOMOTIVE IS NOT RESPONSIBLE FOR ANY DAMAGE THAT MIGHT OCCUR DUE TO THE USE OR MISUSE OF THESE PERFORMANCE MODIFICATIONS. You should make sure you understand the full ramification of these mods. For example, by removing the fuel cut limit on the ECU, it is quite possible you can "lean-out" your engine and burn pistons, valves, or ring-landings. You should keep an eye on the air-fuel ratio to make certain it doesn't drop to an unsafe level and you should make sure the EGTs (exhaust gas temperatures) remain reasonable. Be sure you understand exactly how each ECU safety restriction removal affects the operation of your engine.

Prices and ordering

Our prices for these modifications are listed above. Just to be clear, these prices include the cost of desoldering your stock EPROM and replacing it with a high-quality socket and a new EPROM with your desired modifications. Your stock EPROM will also be shipped back to you. These prices do not include shipping or any applicable taxes. There is no discount if your ECU has already been socketed for some reason. Please let us know the shipping carrier and method you would like us to use, and whether you want us to ship the ECU fully insured.

We currently have other more extensive performance modifications in betatest. If you decide to upgrade to one of these new products in the future, you can apply the full purchase price (sans tax and shipping) towards the purchase of the new ECU modifications (current ECU and EPROM upgrades must be returned in working condition with no signs of tampering).

Our preferred method of contact is via e-mail. Contact us at We can also be reached at 805-692-2181.

Sorry, we are not currently set up to accept credit cards. However, checks or money orders would be just fine.

We reserve the right to change pricing and terms at any time.

©1998 Technomotive
January 28th, 1998