Risk of running rich

[MikeS54]

Afternoon! This one's for the mechanics and the air / fuel ratio peeps, cause I'm not familiar. I have a 2019 Rebel w/ 5.7 Hemi and no e-torque. I have installed the Borla S-type exhaust, the Ram Air kit and today, added the Moe's 87mm Throttle body. My plan is to keep it like that for a while.

Question is - is it fine to run like that on 93 octane gas without a tune? I'm not planning on adding a tune.....unless I have to. I'm probably done modding for awhile as it drives pretty great now (at least on my first 20 mile TB test today). I did hear that if you plan to go headers, you'll need a tune because it'll run too rich.

Thanks in advance for the info!

 

[RAM Patriot]

The HEMI is 10.5:1 compression ratio.

89 octane fuel is recommended for optimum performance and fuel economy by Mopar.

Fuel Based On Compression Ratio

87 Octane
Gasoline with this octane number is proper for engines with compression ratios of 7:1 to 9:1.

89-90 Octane
Gasoline with this octane number is good for engines with compression ratios of 9:1 to 10:1.

93 Octane
Gasoline with this octane number is advisable for car engines with compression ratios of 10:1 to 11:1.

Based on this information our trucks will run optimally with 89-93 Octane fuel. Without having to advance or retard the timing.

 

[HandyCruiser]

The Ram Air kit is not supposed to void your warranty. Cat-back custom exhaust might void some of the warranty on the engine, I'm not sure. But hacking the PCM has been reported to void much of the warranty. Depending on how much time and mileage is left on your warranty, you might consider getting another PCM and then have it tuned by someone skilled at tuning Rams with the 5.7 Hemi. That will help your engine run better and help you take better advantage of the mods you've made. And good tune would likely make a bone stock engine run much better as well. You just have to remember to reinstall the stock PCM before going to a dealer.

If I was going to do that, I would likely look to Diablo Sport. They sell unlocked PCMs that work with their tuners. And many folks that do custom tuning have the software to write tunes that can be uploaded with a DS tuner. But start with the guy (or gal) that you want to do the tuning and get the equipment they recommend.

 

[Orion10182011]

Yes OP it will be fine to run like that. The throttle body is the only thing that might affect the tune. And that's a might.

Most likely the bigger TB will only affect how sensitive the throttle is. Doubt your getting any real power gain from it.

 

[Richard320]

If you're always running too rich or too lean, the computer will adjust the long-term fuel trim to bring things back to normal. This will be retained in memory even when the truck is off. Disconnecting the battery will erase it and it will have to relearn it again. You won't have any problems unless you get to some preprogrammed threshold. Typically it's somewhere near 30% off the original. Then you start triggering codes and setting off the light. If you can go a couple tanks of gas under all sorts of driving conditions without triggering any lights, I'd say you're fine.