Worse gas mileage with Predator

[mnpewter04]

Just got a Predator for Christmas, installed the 87 tune and noticed that I have lost 2-3 mpg according to the computer.  Just wondering if anyone else has seen this with their installs?

[old-chevy-dude]

did you set your tire size?

the predator has a default size in it, something like 205/75 R15..

When you write the tune to the vehicle if you fail to adjust from the default size (even if you have OEM size tires) it tells the ECU you have a different size tire and screws up the speedo and the mpg reading in the vehicle DIC

[LornesAV]

I would think that would be in the instructions!
I just got my truck back with new pistons and rings. Gas mileage took a dive, 15 down from 17. I have an app that shows fuel trims short and long. The longs were at +7 and it look like shorts where hovering around +3. The shorts are kind of hard to read as the changed rapidly. All 3 different tunes available had the same results.
Trip before I had the pistons changed long trim was at a -4 and that was after drive quite a while with +4 for a while.

[ohiobellboy]

I would think that would be in the instructions!
I just got my truck back with new pistons and rings. Gas mileage took a dive, 15 down from 17. I have an app that shows fuel trims short and long. The longs were at +7 and it look like shorts where hovering around +3. The shorts are kind of hard to read as the changed rapidly. All 3 different tunes available had the same results.
Trip before I had the pistons changed long trim was at a -4 and that was after drive quite a while with +4 for a while.

-4 is too low! Check the Pred forums. Ideal is 0 to -2. If you're at +7 then it needs adjusted. Make sure you're following the proper methods for determining your LTFs. Monte is better at explaining this than I am but I know those are the numbers you're looking for.

[mnpewter04]

I thought I changed the tires but maybe it didnt take... I will have to run out and check.  Have been reading on the other forums and trying to figgure that stuff out is like another language for me, just cant wrap my head around the numbers.

[mnpewter04]

Checked and do have the current tire size in the program.  it should be entered just as the tire shows right? 265/70/r17.  My spedo is also off by 4 mph but cannot seem to change it with the stock tires size entered.

[ohiobellboy]

Checked and do have the current tire size in the program.  it should be entered just as the tire shows right? 265/70/r17.  My spedo is also off by 4 mph but cannot seem to change it with the stock tires size entered.

If your speedo is off, then that will account for some of your mileage. Is the speedo fast or slow?

[CodeBlueEMT]

 My fuel mileage can vary 2-3 mpg just from city driving, stop and go vs. setting the cruise on the highway and rolling.

 Did you change any parameters other than trying to enter your correct tire size?

 I didn't try to compute my mpg's right after installing the Predator performance tune. Initially, my right foot tripled in weight.

 Might not hurt to check your air pressures if you haven't done so recently. Every little bit helps.

 Good luck.

[mnpewter04]

Speedo reads 60 and gps shows 56.  Before the tune instant mpg on a flat road would vary between 19-21 and after it is 17-18 on the same road with same speed. I haven't changed any other perameters as I don't know what to change

[LornesAV]

Speedo reads 60 and gps shows 56.  Before the tune instant mpg on a flat road would vary between 19-21 and after it is 17-18 on the same road with same speed. I haven't changed any other perameters as I don't know what to change

Same gas?
Not meaning to 
My issue may have been my wheel bearing and maybe the gas, and highway traveled. I tend to get worse mileage on 55. I traveled back 67 (maybe 5 mph slower) DIC showed 19.5 actually 17.9 mpg. I still would have to say not what I expected. Next week highway 44 and 70 (usually my best mpg).

[mnpewter04]

Well I fixed the speedo problem. I adjusted the tire size by tire height in inches. But now my remote start won't work. Seems to be one thi g after the other with this

[LornesAV]

After reading your post I tried mine, it still works. Maybe coincidence.

[MightyMouse]

Speedo reads 60 and gps shows 56.  Before the tune instant mpg on a flat road would vary between 19-21 and after it is 17-18 on the same road with same speed. I haven't changed any other perameters as I don't know what to change

If you're logging a +7 LTFT (Long Term Fuel Trim), that means you're running extremely lean, so the drop in mpg makes sense. Keep in mind that weather has a lot to do with LTFTs as the air gets more dense in colder temps, using less fuel.
If you've been running your tune for more than 100 miles and you're still showing +7 (using the Predator's data logging feature), go into the tune and adjust the injector slope by -7. Run it for 50-100 miles and log it again. You should be near zero in your LTFT.

Read the stickys on the diablosport forum as well. They'll help you a lot!

Good luck,
MM

[LornesAV]

I have read some of them but I think I would be afraid to adjust the settings. I am not sure what happened on that trip. I ran 18.5 down to springfield mo and 18.5 back but haven't filled the tank to verify. The app I have now shows +4, I would have thought that would be on the rich side. I am running the 87mpg boost currently.

[mnpewter04]

If you're logging a +7 LTFT (Long Term Fuel Trim), that means you're running extremely lean, so the drop in mpg makes sense. Keep in mind that weather has a lot to do with LTFTs as the air gets more dense in colder temps, using less fuel.
If you've been running your tune for more than 100 miles and you're still showing +7 (using the Predator's data logging feature), go into the tune and adjust the injector slope by -7. Run it for 50-100 miles and log it again. You should be near zero in your LTFT.

Read the stickys on the diablosport forum as well. They'll help you a lot!

Good luck,
MM

So i would need to do a data log, is this done while driving and hooked up to the predator?  And is this adjusted in the performance tune?
Thanks

[LornesAV]

So i would need to do a data log, is this done while driving and hooked up to the predator?  And is this adjusted in the performance tune?
Thanks

Yes there is an option in the diablo menu to data log but first go to the diablo sport forum. 06monte has a thread under predator, GM Gas for the proper items to log.

After filling up mine the mileage back from Springfield is at 14.8, the DIC read 19.6 gallons used the actual fill was 23.227 nearly four gallons difference. This happens about once every six months.  one of the frustrating things to monitor my AV operation to show if tune up or some kind of maintenance needs to be performed. Or is it just the gas stations pumps way off.  If that is the case then the next fill should be less than the DIC. I have had that happen as well.

[LornesAV]

So i would need to do a data log, is this done while driving and hooked up to the predator?  And is this adjusted in the performance tune?
Thanks

Have you invested in the tune from 06monte? If so any improvement, I would have to say I had had no improvement from the stock diablo tunes. I am going to put the factory one back on for this week and see what happens. I checked one of my 02 sensors today didn't look to great so I have them on order. God bless the GM mechanics for having to deal with what should be an easy change out but isnt.