yo_marc

I recently swapped in a Borla axle back exhaust. Seems like a great system. I noticed almost immediately that I was getting a fair amount of pinging under moderate acceleration and quick tip-in under, say, 2500rpm. I figure the JK's electronics need to adjust the fuel trims to the free'er flowing exhaust. In the meantime I'd run 89 grade fuel.

I ran through two tanks of 89, and was surprised at how responsive the motor was. I went back to 87 over the weekend, and notice almost immediately that the motor's response is poor and power under 2500 is down. RPM's hang when shifting and it's harder to rpm-match gears. The exhaust note is noticeably flatter too. In my experience, those are all signs that timing is getting pulled. Threw in about 5 gallons of 89 yesterday, and it's a little better today.

Anyone else out there experience anything like this? Is it a byproduct of a better flowing exhaust? Just bad gas?

Not really complaining about the 'need' to run 89. The power increase is very noticeable. More curious to hear what you all think is going on.

Thanks

IcyFridge

It is more likely bad gas. I have done countless exhausts over countless vehicles and have never had the problem you are experiencing.

Try a different gas station's 87 octane and see if it is the same? Do you have a tuner installed?

yo_marc

Thanks - I likely will at the next fill up.

No tuning installed.. From air filter to the cats, I'm all stock. (except for spark plugs).

I've done a few other exhausts too, also haven't experienced anything like this. Had me scratching my head.

BKGM Jeepers

My 3.8 prefers the tune I installed. I get better performance, better mileage and no pinging on 87 octane.

I'd think you're getting bad gas. I was just in Utah and noticed that they sell 85 octane at stations. I didn't try it in my jeep.

yo_marc

Thanks guys. I actually have a tuner in the mail now. Looking to install it early next week.

That's very interesting that the 3.8 perfers a tune for 87. I'm glad to hear - I have been afraid if I run a 87 tune that the motor will want to ping even more.

I couldn't resist filling up with 89 octane this morning. Again, very noticeable difference in the motors power and response.

It seems as though 87 is hit or miss... sometimes it runs decent, others, doggy. 89 has consistently performed above and beyond what 87 delivers, even on it's best days. It's a 'fun' improvement, just surprising to me.

FWIW, we run a 'winter blend' of gas here, for the cold weather. Not sure when the local stations switch back to a warm weather blend, but it's certainly noticeable when the winter brew hits the pumps. Not in a good way. Also, we run 10% ethanol. And I'm at 200' above sea level. Cant help but wonder if all those factors play into one another and combine to make 87 octane fuel flirt the line of what the 3.8 needs.

mgmavant

My stock (engine anyways) 08 needs to run on 89. Every time I try to run the 87, it pings and knocks all the time - especially under acceleration. I've been running 89 for a couple of years now with no issue, but I do try the cheaper stuff every now and again to make sure. If I knew a tuner would work, it would have paid for itself by now!

jaybrown

Try to but Eco fuel saver. It works just as good they say even better than high octane for only a couple bucks extra a tank. I run the 93 tune it's great on 87 gas with the Eco fuel saver. You get more milage and more power. Awesome product