LongHornCherokeeMan

I have been looking into purchasing a performance module/flash chip for my jeep to get me better gas mileage and better smoother performance. There are just so many and they all state to have great gains. I was wondering if anyone has any advice to share with me

Schmoozer

x2, always interested in an inexpensive & easy mod

LongHornCherokeeMan

so know one has any suggestions i sure as **** dont want to find out from trial and error

solderjunkie

There may be reflashed PCM's, but I've never seen one.

The JTEC controller is set-up pretty well already.

There is no "free performance". If you see a performance gain, you trade for it. You will lose fuel economy, or driveability, or emissions, or all-of-the-above.

ol"blue

When I checked on a couple of those "plug-'n-download" type reprogrammers for a normally aspirated engine, they increase power by increasing injector pulse width and advancing the timing. They average an increase in HP of around 10-20, but this is not conducive to increasing the MPG's. It takes more fuel to get more power. You can't have it both ways.

Cobrasix

As I'm sure you know, there is no 'free' performance gains. While with carb'd engines, you could increase power and economy by making tweaks on the jets, that was because the carbs were not always set up to run the most efficiently out of the box. Couple that with weather changes and they needed tweaking to keep at peak performance.

Modern EFI engines are already designed to run at a peak efficiency. You could in theory gain a little more MPG by retarding the timing a little more, but that can lead to other problems (overheating, knocking, etc). Most of the performance chips only advance the timing curve, which can result in modest gains in HP, but you will lose MPG as a result generally. With EFI the stock ECU is working to keep the ratios perfectly balanced based on loading, etc. Now, a well designed ECU reprogram can tweak the curve in such a manner as to not change the timing/pulse at idle and part throttle so you keep the MPG and then advance the timing/pulse at WOT to result in a minor increase in HP. Problem again there is most manufacturers already do that so they can advertise high HP numbers with decent MPG ratings. There is only so far you can advance the timing without major side effects.

I'm currently working on making an EFI system for my 65 mustang and working on making my own ECU (well, Megasquirt based) and the above factors are all things that have to be weighed. It's fun developing fuel/spark maps. (Not really)

So, long winded answer is that you won't gain much from a reprogrammed chip unless you've done other power adding modifications. But no matter what, to get more HP you have to burn more fuel.

Schmoozer

But conversely, if its a DD, I could put it on a "fuel saving mode" driving to and from work. However I'm getting the feeling there arn't any plug and play types for the Cherokee.

ol"blue

If not offered, most companies will custom make anything you want/need for your particular application. Give them a call.

Schmoozer

Yeah, but that also sounds like we're now leaving the realm of inexpensive mods...

Cobrasix

Thing to remember about modern ECUs is that they are not a 2D curve. They are a 3D map that uses inputs like air temp,RPM, ambient pressure, either Mass flow or Manifold Air Pressure, and Exhaust O2 ratios to optimize the performance of the engine based on apparant driving conditions. So, if you are daily driving, part throttle not doing anythign crazy, the stock ECU is already working to keep the fuel ratio as efficient as possible. Generally speaking, most ECUs always work for the most efficient fuel supply needed and only become inefficient when you are WOT or under heavy load (towing as read by MAP/MAF readings).

Any EFI system build in the last 15 years is already geared to being as efficient as possible under normal driving circumstances.

Want better MPG? put an ignition control that puts a rev limiter at 2500 RPM with a flip of a switch.

ol"blue

But that doesn't address the OP's need for more HP.

solderjunkie

AND mileage.

I don't see it being possible to get both from a simple PCM change.

If it were possible to get performance and mileage, MOPAR would have built it that way

LongHornCherokeeMan

ok so I think this is the first time i have said this "The factory must have done the best job they could"

Schmoozer

Cobrasix, the next time I say something stupid feel free to smack me. I was literally doing this stuff three months ago:



I don't know what came over me...

ol"blue

That's what I stated earlier. "It takes fuel to make power". He was seeking more power. Subsequent posters needed more MPG's.