Is Racing on 93 "Safe"? Not really.

[Speedy!]

@BULL @jonx96 @vortecd @hellman

I've seen a trend lately with people going to the track with their Hellcat with 93 in the tank. That's not the best idea from what I've seen. Running around on the street you're probably not gonna be able to hammer on it enough to be a problem but even then if you plan to really get after it for some reason I'd suggest a little insurance in the way of good fuel. Most race tracks sell race fuel and adding 2-3 gallons to the tank is cheap insurance and doesn't require any tune changes or anything else. It simply provides some protection when running these cars hard.

For those that don't know, my original motor blew up. It broke the number 7 rod and spit it out the oil pan. By the time it broke I had been racing the car for a couple years and had just started modifying it. At the time it was a head scratcher because everything was setup to be super conservative. I've learned a bit about these cars since then, and seen quite a few standard Hellcat motors break the same way mine did, and quite a few of those it was even the same cylinder 7 that let go.

This is a drag strip pass in my car bone stock on Shell 93. STKR was logged throughout the entire run with a max of 5.5 deg which is A LOT. In a custom tune I don't wanna see more than .5 to 1 deg in a blip or two.
Sorry these are in Diablo, this was before I saw the light and switched to HPTuners.


I dropped in a couple gallons of 109 unleaded race fuel for the next pass just to see. STKR was reduced dramatically indicating the knock on 93 was REAL. I actually needed more 109 than I had added since it was still getting a couple degrees of STKR here and there but the 109 definitely helped a TON.


Back then I thought, meh it's stock so it must be fine or they'd not sell them like this. Ran the car for about 18 months no issues, started modifying it and the motor failed within 3,000 miles of adding a pulley. Coulda been a fluke, I just got unlucky, OR all that knock over time had taken its toll on the rods. I've had lots of emails and comments on my YT channel about people having the same thing happen and more then you'd think were bone stock cars.

So you may say, who cares it's under warranty. OK, what if it breaks after the warranty is up or what if you're waiting 6 mos for a motor and hoping the dealer techs do a good job installing the new one? I bet that $10/gal race fuel as a safety net sounds pretty good about then.

2015 and 2016 Hellcat factory tunes are quite a bit hotter than later years. I'm not sure about 2017, but in 2018 there was a definite change to the commanded timing. Here's a comparison between a 2016 and a 2018 A8 Hellcat factory tune file timing table at WOT. Anywhere you see a red number is how many degrees LESS the 2018 is vs the 2016. Notice most of those red numbers are where a stock car lives at WOT in the upper RPMs and it's as much a 3deg but something really got their attention around 2880 RPM as well.


Just a PSA based on my research and experience but I'll never again run the car hard on "pump gas" unless it's E85 "pump gas"

 

[BULL]

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[Hpindy]

I'm going to give my $0.02 as a person who races ON pump gas ....
If you are a person that doesn't want to data log , know what you are looking at , know how to make changes or don't have a good relationship with a good tuner I wouldn't race on pump gas ..... It's not worth the risk . it varies so much it's hard to dial in a " hot " tune.
I could speak for days on this .....

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[DavidKFla]

I just switched my Charger over to 100 VP just because I felt that it was needed. My buddy with a SRT8 Challenger was just told by his tuner that he needs higher octane in his car because it was spark knocking.

 

[ACMAVRO]

Watching

 

[jonx96]

Here was my second revision of a tune. It was March. Poor fuel. Any time we have good DA it is usually followed with poor fuel so if I was wanting to push for the best times no way I could do it without adding some octane booster
This tuner didn't update all the tables he should have because the car actually went into negative timing. I'm sure that was great on the engine during a hard wot pull.........

Here is a log from a well known tuner a bunch of people seem to love for some reason. I asked for a flex tune where the 93 is as safe as possible because I wasn't using it to race
Well here is some knock in a chart nicely laid out

Some of this has to do with tuners pushing cars to hard. Some of it has to do with crappy 93 in spring and fall months. Regardless I'm sure these tunes were close to 0 knock on great 93 and summer months.

 

[drag racer]

sub'd

 

[Speedy!]

@jonx96 so in your first screen shot it would show a commanded 12deg of timing. Is that on a stock setup or with a pulley and what RPM? Something is definitely funky with that. Calibrations have a "floor" (how it was explained to me) that is the lowest possible timing value after all modifiers. -2 was probably where yours was, so it basically just yanked all of it for some reason. A spike that slowly drops (decay rate) is usually something funky going on. Could have been some knock and the car over reacted for some reason.

The table you posted is more interesting. Same question if it's stock car or pulley installed? The rest of the story would be commanded timing in the tune. On my car, there were a few RPM areas after the pulley (maybe before too) where it was prone to resonance and noise from the supercharger that set the knock sensors off. On mine 4,000 RPM was a real noisy spot.

Once you get in to custom tunes and pulleys on 93 things get even more interesting beyond bone stock racing on 93 which is what I was trying to highlight in my post.

 

[Speedy!]

I'm going to give my $0.02 as a person who races ON pump gas ....
If you are a person that doesn't want to data log , know what you are looking at , know how to make changes or don't have a good relationship with a good tuner I wouldn't race on pump gas ..... It's not worth the risk . it varies so much it's hard to dial in a " hot " tune.
I could speak for days on this .....

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By the time you see a problem in a log there's a real possibility it'll be too late and the damage is done. It's just not worth the risk when you can easily add 2-3 gallons of race fuel IMO.

 

[jonx96]

@jonx96 so in your first screen shot it would show a commanded 12deg of timing. Is that on a stock setup or with a pulley and what RPM? Something is definitely funky with that. Calibrations have a "floor" (how it was explained to me) that is the lowest possible timing value after all modifiers. -2 was probably where yours was, so it basically just yanked all of it for some reason. A spike that slowly drops (decay rate) is usually something funky going on. Could have been some knock and the car over reacted for some reason.

The table you posted is more interesting. Same question if it's stock car or pulley installed? The rest of the story would be commanded timing in the tune. On my car, there were a few RPM areas after the pulley (maybe before too) where it was prone to resonance and noise from the supercharger that set the knock sensors off. On mine 4,000 RPM was a real noisy spot.

Once you get in to custom tunes and pulleys on 93 things get even more interesting beyond bone stock racing on 93 which is what I was trying to highlight in my post.

Both logs were with a 2.85 pulley. I have no idea what the first log was for timing because it was diablo.
The second tune maxed at 14 deg. Which in my books is not a conservative 93 tune and a max effort tune for a 2.85 and 93.

 

[jonx96]

Also octane booster fixed the knock issue of the first log so I know it was real the second I never tested. But I never run 93 so wasn’t even worth the test.

 

[Hpindy]

By the time you see a problem in a log there's a real possibility it'll be too late and the damage is done. It's just not worth the risk when you can easily add 2-3 gallons of race fuel IMO.

I start out "soft" with the tune them work my way up watching everything... But not everyone does that ...

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[Speedy!]

There ya go. I do that even with E85 LOL.

 

[Linda's Hell Cat]

My Husband John "Top Cat" Posted back in 2015 that he put a couple of gallons MS109 in my stock Hellcat when I was racing at the Track. His thoughts and it was from information that he read about the SC was to add the MS109 to keep my HC Charger's Engine safe.
Even now if I happen to be racing and using 93 I still have the added MS109 and Josh@HHP believes it is a good safety measure to take.
Some guys like to race around the the streets on 93 and they add the octane booster. And some won't tell you that they do because they think it makes their Tuner look Great!
This is not about anyone's Tuner that is in this thread, but it is about some Tuners who are known well enough.

Linda

 

[Hpindy]

There ya go. I do that even with E85 LOL.

Same here ... Also I have the demon HO bottom on my car so I have a super safe pump gas tune for regular driving then I play with the timing in the HO tables and if there is a big problem ( pulls 4 degrees ) it will kick back to my street tune instantly..
I do this with any fuel I use ......

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[The Max]

The way i read this info, BTW thanks for enlightening us non tuned Hellcats, is that all Hellcats have knock retard.

Imagine if only 91 octane is your only choice! Always add some kind of octane booster.

If your not racing and just accelerating hard in our Hellcats, even stock, we are not producing full power if were knocking.

Is it possible that the knock sensors are too sensitive?

I'm still trying to understand if the Bypass leaks power from the supercharger.

 

[EricG]

Interesting and on the edge of what I understand about these cars and the tune. So this is especially a concern for pre-2018 cars?

I can only get 91 octane, but I do live at 5500' elevation. I have raced my car with a 50/50 mix of 100 octane unleaded and regular 91, also raced it with just only 91 in it. Times and trap speeds were almost exactly the same.

I thought I read that the factory Demon tune and the tune on 2019+ cars is better than before. This has me second-guessing whether or not I'm fine just running pump gas all day every day and also has me questioning future mods and fuel desires...I guess I'm lucky to have decent access to E85 in my area, there's quite a few stations that have it I think. Was not going to make that my primary choice though.

 

[PaVaSteeler]

Following. Very informative, as usual (love your YT channel).

When running my race logs, I notice an occasional KR blip of .5 to 1.5, but only briefly; I'll have to pull the actual tables and study them closer now that you've pointed this out.

For us pedestrian 6.4L owners who race on a 93 octane tune, any detriments with using the RaceGas brand of octane booster?

My car is down at MMX waiting for an upgrade, but in my conversations with them, they felt a race gas tune (plus the ongoing cost of MS109) wouldn't net me material results, especially compared to the cost.

Based on this post however, I'm feeling some preventive measure might be in order as (as others on here have pointed out) I may be vulnerable to the vagaries in the quality of the 93 gas I use.

 

[Linda's Hell Cat]

John gained his Experience and Knowledge for a couple of mods he had done to his Hellcat and Mine. This comes from building My 2010 SRT8 3.6 to 4.2 Kenne Bell Build. Which was with Tim Barth.
The Hellcat has a Super Charger that gets hot and works in Tandem with the Engine. The MS109 was not for any ET gains but it helped keep the engine cool = Safe.

@Speedy when I attended Challengerfest with my brand new Stock Hellcat Charger, John added the MS109.
That year I drove from Winter in Pa finishing my break in miles, stopping on the way for an oil change and then continued to a Hot as Hell Spring in Bowling Green. That next day I raced my Stock ( had a DSS AL DS installed. We all know the stock 2015 was a Twizzler waiting to happen and some Nittos 555's) I got to enjoy racing 14 back to back passes. I had a wonderful weekend with lots of wonderful peeps.

Thank you @Speedy! it's good to help the members with your info because blowing up engines is not cheap and yes there were stock blown engines as well as Tuned.
We know we can get away with somethings sometimes and then that day happens when and the smoke comes but, it's not from a a burnout. Or a bunch of oil underneath.

Better be safe than Sorry

Linda

 

[Idoru99]

So now I'm confused.

While at Challengerfest this past year, I was planning on adding some race gas to "stay safe." From what I understand, it's to raise the octane a bit to help reduce or prevent short term knock retard.

I mentioned it to one of the people helping you run Challengerfest and was told it would be a waste of money because I wasn't tuned for it and the engine couldn't use it (paraphrasing, but that's what I took from the comment). I wasn't trying to "use" it for ET, I just wanted to stay as safe as possible.

What am I missing?