Proof that 87 Octane fuel is limiting your 3.6

[bmpcamry09]

Yeah.....another octane thread, but this one is different. This one has proof as to why these 3.6 engines run best on anything other than 87 octane. If you want to safely run 87 octane and still have factory power, you need to be tuned for it. I have no problems tuning for 87 octane for those that want it. But if your stock, your losing out on potentially 40 horsepower and 40 foot pounds of torque when the weather is hot, and the data to prove it is right here. Check out my video. This video is featuring JL Wranglers, but they tune and operate the exact same way on the Gladiator, there are no differences in the ECU tune between the two.

EDIT: Yes, I realize it was not an exact comparison in the video, my intention was to just show an example of a Jeep running like crap on 87 and what a similar Jeep can run like with custom tuning on the same fuel. If you go to page 2 of this thread, you will see an exact side by side comparison for the same Jeep for more accurate data.

Sponsored

 

[azmojave]

So if you don’t let the timing retard to avoid knocking, are you letting it knock? Or is there a fix for that? Where do we go for more info? My Google machine isn’t helping.

 

[bmpcamry09]

So if you don’t let the timing retard to avoid knocking, are you letting it knock? Or is there a fix for that? Where do we go for more info? My Google machine isn’t helping.

It's not that we aren't letting it retard with the tuning. All factory knock retard strategy is left in place in my tuning for safety.

With tuning, we are optimizing WOT fueling, intake and exhaust variable cam scheduling, and spark table mapping to allow that hot gas to get out of the engine faster and help prevent knock from ever happening in the first place.

Attached below is my tuning guide. Walks through everything to get started.

 

[azmojave]

Thanks. This is out of my wheelhouse.

 

[bmpcamry09]

Thanks. This is out of my wheelhouse.

All good!! I’m a nerd. Lol

 

[yoda13]

This is out of my wheelhouse too. I will say that my jeep feels noticeably less spunky when it settles into true summer around here.

 

[bmpcamry09]

This is out of my wheelhouse too. I will say that my jeep feels noticeably less spunky when it settles into true summer around here.

Yep, these ECUs have a table that aggressively pulls timing when intake air temperature goes up, as it does with ambient air temperature increase.

for people that modify their jeep, but might not want to fork over the money for a custom tune, heat management will go along way. Think of ventilated hoods and that sort of thing.

 

[davey]

will higher octane help till it gets programmed?? and when you do said program if you forgo hp/tq will it increase fuel milage..

 

[AmishMike]

@davey yes higher octane will certainly help.
For example, I have a 2020 Rubicon, stock. I average 19.8 mpg on a trip running 87 octane, if I use 91 octane on the same trip I get 21.3.
In the heat of the summer when pulling my 16’ camper which is single axle and weights 2,480 dry, I am down to 10.0 mpg running 87 octane at 63 mph. When I jump up to 93 octane, not only do I get close to 12 mpg but my sweet spot jumps up to 71 mph.
This non scientific study of mine is based on over 100k miles with the Gladiator. Trips all over the east coast and throughout the south. Camper towing had been from Pa. to Fl. Several times, Ohio and parts of New England.
Around me, there is about an $0.80/gal difference between 87 and 93 octane. So for daily driving without a load etc., it does not make financial sense to me to run anything over 87. When I am towing, not only does it nearly pay for itself in mpg, the fact that the sweet spot jumps up 8 mph and I can go further between fill ups is well worth it.
I confess that I have not done any real world comparisons using 89 octane. That might be more economical and be enough. I don’t suspect so. Maybe hot weather and not loaded, it would suffice.

 

[Free2roam]

No issues here..... should've bought a diesel.

 

[White Eagle]

There is no question it makes a difference but something else that makes a difference for me is if you are buying gas within one of these counties around ozone day cities. There is something different and negative about the gas In these areas.

 

[Dilly’S Willy]

I think it should also be noted that those who are in tard states with ACN fuel, the gains are a bit less as your fuel is much worse than most everyone else.

Every engine I've had ran worse and could feel less power everywhere after living on the east coast then moving to the west coast with the same vehicles (same VINs).

And yes, untuned on 89 you can feel a difference when you push it hard, until it gets hot again. But once those intake temps come back down, the power returns a bit more again.

TBH I think my next mod (after tires and brakes) will be the tuner setup. Tired of crap MPGs and lack of power with my manual.


@bmpcamry09 have you found a way yet to reduce the power limiter for the clutch temp bs? Or even any tables? I'm assuming the Auto PCM doesn't have those tables?

 

[bmpcamry09]

The manual ECU doesn’t have that mapping either. I’ve actually done more manuals than automatics and I’ve seen the inside of pre recall and post recall files and there are minimal differences within the ECU, I think another module, perhaps the BCM, is the primary monitor of that.

 

[Rusty PW]

The manual ECU doesn’t have that mapping either. I’ve actually done more manuals than automatics and I’ve seen the inside of pre recall and post recall files and there are minimal differences within the ECU, I think another module, perhaps the BCM, is the primary monitor of that.

Have you found anything for torque management in 1st, 2nd and 3rd gears in the auto that limit power?

 

[bmpcamry09]

Have you found anything for torque management in 1st, 2nd and 3rd gears in the auto that limit power?

Yes. Several things.

For starters, on the engine side, a hard ceiling of 279 LB FT torque demand is set on stock tuning, but there is a flywheel torque table that is used as a multiplier and reduces this down even further.

Also, the throttle blade won’t open fully even at wide open throttle until RPM range is around 3500-4000 on stock tune. Tuning it correctly will get it to fully open right off idle if torque demand warrants it.

Most of the torque limitations outside of that are within the factory cam scheduling, mostly just the intake variable cam scheduling. Depending on fuel/octane/knick resistance, the intake cam timing can be advanced anywhere from 5-70 degrees from its resting place at any time.

The tricky part is Stellantis ECUs don’t like these parameters simply maxed out, unlike some GM stuff I’ve done. There are several tables that have to align with one another to make everything work well together. There are other tables that have to be inverse of each other or they can throw a limp mode condition. It’s pretty advanced and took awhile to get everything ironed out the way I wanted.

Sponsored