JTEC 4.0 Injector Scaling?

[Mr4btTahoe]

Hey guys...

So on the '98 JTEC 4.0 ecu, there isn't much there for altering injector size. I've seen some threads talking about adjusting battery voltage correction... I've seen another talking about scaling the entire fuel map by the percentage difference between the stock injectors and the replacements.

For instance.. the stock injectors are rated at 243.8 cc/min (23.2lb @43.5psi) and the replacements are rated at 363.1cc/min (34.6lb @ 43.5psi). That equates to a 48.93% increase.

So.. if scaling the whole map.. would I multiply the whole map by .5107?

Or is there a better way to do this?

Thanks guys.

[B00STJUNKY]

Hey guys...

So on the '98 JTEC 4.0 ecu, there isn't much there for altering injector size. I've seen some threads talking about adjusting battery voltage correction... I've seen another talking about scaling the entire fuel map by the percentage difference between the stock injectors and the replacements.

For instance.. the stock injectors are rated at 243.8 cc/min (23.2lb @43.5psi) and the replacements are rated at 363.1cc/min (34.6lb @ 43.5psi). That equates to a 48.93% increase.

So.. if scaling the whole map.. would I multiply the whole map by .5107?

Or is there a better way to do this?

Thanks guys.

Use the inverse of the injector increase.

363.1/243.8 = 1.4893
1/1.4893 = .6715

Multiply fuel map by .6715

And, yes, you need to alter batter voltage offset to match the new injectors, or the whole map will be off.

All of this, of course, is assuming the only thing changed was injectors. If there were other changes made (ie. MAP sensor range, base fuel pressure), then the whole stock mapping is thrown out and you basically start from scratch.

[Mr4btTahoe]

Already tuning for the 2 bar map... Just starting to run out of injector.

So.. where do I get the battery voltage offset info? The injectors I'm using are coming from another car.. low mileage grand Prix gtp. They are plug and play as far as size and such goes... But they are just a stock injector. So far, I've only had luck finding flow rates I posted above.

Thanks for the insight.

[spoolboy]

So.. where do I get the battery voltage offset info? The injectors I'm using are coming from another car.. low mileage grand Prix gtp. They are plug and play as far as size and such goes... But they are just a stock injector. So far, I've only had luck finding flow rates I posted above.

Thanks for the insight.

From the calibration of a GTP file would be the only place - if it happens to be in the same format. And it probably won't be.

So your choices are to purchase injectors that you can get data for or say fuck it and dial it in as close as you can with pulse-widths without changing the battery offset. And possibly have issues.

[B00STJUNKY]

Already tuning for the 2 bar map... Just starting to run out of injector.

So.. where do I get the battery voltage offset info? The injectors I'm using are coming from another car.. low mileage grand Prix gtp. They are plug and play as far as size and such goes... But they are just a stock injector. So far, I've only had luck finding flow rates I posted above.

Thanks for the insight.

An injector P/N would be needed to have any hope of finding that data. Or, at least the make/model and year that these injectors came from, then getting the corresponding tune file for said vehicle to look up what the GM calibration had them defined as. Even then, assuming they were originally calibrated as 3 bar injectors, and are now running in a 4 bar setup, it'll be a bit of guess work getting them defined close enough.

[Mr4btTahoe]

Hmm...

The injectors are a Bosch # 024508208 also referred to as the "Bosch Whites"

I've found some numbers but not sure yet.

[B00STJUNKY]

Hmm...

The injectors are a Bosch # 024508208 also referred to as the "Bosch Whites"

I've found some numbers but not sure yet.

What are the breakpoints for voltage that are shown in your calibration file?

[MSJeepTJ]

Mr4btTahoe

I would love to see one of your tune files on tuning the 2 bar map. Im working on my 97 2.5 turbo and having some issues

[Mr4btTahoe]

Mr4btTahoe

I would love to see one of your tune files on tuning the 2 bar map. Im working on my 97 2.5 turbo and having some issues

My other post describes most of what I did.. I'm at work now but can post the current file when I get home.