Is Racing on 93 "Safe"? Not really.

[16GoManGoHC2]

@16GoManGoHC2 the Hellcat will use .0722 for stoich which is 13.85 AFR. To get what your actual AFR is multiply .793 x 13.85 = 10.98AFR on gasoline.

Richer than I'd set it to, but if you dialed it in on a dyno and made max power at that setting then it is what it is for your car.

The yellow highlight for FA Enrichment is the amount of PE your car is commanding to get to .793 lambda at WOT.

View attachment 63438

@jonx96 figured this mystery out for me. This is in my Flex tune where 0% alcohol in table 34290 is using a FA Stoich of .0680 not .0722 so my AFR at .793 Lambda should be around 11.66 like the AFR calculator says for gasoline? Correct or no? Just trying to wrap my head around why the car liked this and plugs looked good mixture wise.

 

[Speedy!]

1/.0680 = 14.7 AFR which is the stoich point for gasoline. .793 x 14.7 = 11.66 AFR so yes you're right there. You have to be careful with the FF tunes since they change stoich points throughout the mixture percentages.

 

[jonx96]

so ford you just type in the lambda number In the power enrichment table. It’s kind of nice because it takes away some of the math 😂 there are somethings ford does better and things dodge doesn’t better. If I could just tell the two of them take the good from each and put it in one it would be so nice

 

[jonx96]

1/.0680 = 14.7 AFR which is the stoich point for gasoline. .793 x 14.7 = 11.66 AFR so yes you're right there. You have to be careful with the FF tunes since they change stoich points throughout the mixture percentages.

Well remember still a little on the rich side that .79 meaning does not change like AFR.
Is the .79 rich enough to cause a lot of harm? Ehh no. Maybe if ran long enough he could run into some issues but like he said the plugs would show it before the engine had an issue. I think there are a lot of things that have to be looked at to look at his knock issue. The extra fuel may not be the issue. Playing with other settings could affect this as well.
I need to look at some of the logs he has sent me.
I have seen fuel trims being off enough where .81 turns to .87 then turns back to .88 and there was some knock to follow this quick event. Is that his case I don’t know yet. But there is a professional term I like to use that goes “do not rape the PE table to fix a fuel trim issue” 😂 or really any issue.
sometimes you can make more power if you pull a degree of timing and lean it out a bit. Adding and removing fuel can make a dyno which is crazy. Which he say a gain but was that because the engine was running as efficient from either KR or depending on his knock sensors just the event of the knock hurting hp. The richer fuel could have lessened the affect. But being able to lean it out a bit and diagnose the knock issue may gain even better results. We will see.

 

[Speedy!]

I must of missed mention of a knock issue. In any case I think 11.66 afr is a sweet spot. I always shoot for 11.4 - 11.6 for a street tune. That's .83 lambda on the Hellcats 13.85 stoich. I go for .81 on E85. I'll bring in a tick more fuel above 6000 as a safety.

Knock can be a funny thing on these cars when a smaller pulley is installed. I always start with known high octane fuel to dial that in.

WOT trims should be easy to sort out.

 

[Magnified]

How big a tick more fuel? Just curious.

 

[16GoManGoHC2]

I must of missed mention of a knock issue. In any case I think 11.66 afr is a sweet spot. I always shoot for 11.4 - 11.6 for a street tune. That's .83 lambda on the Hellcats 13.85 stoich. I go for .81 on E85. I'll bring in a tick more fuel above 6000 as a safety.

Knock can be a funny thing on these cars when a smaller pulley is installed. I always start with known high octane fuel to dial that in.

WOT trims should be easy to sort out.

From watching the exhaust, looking at plugs and pistons I don’t think I have actual detonation (knock). I’m just on a quest to get the knock sensor voltages as low as possible so if true knock does occur the sensors catch it quick. She runs clean, but a 2618 piston engine with looser then stock PTW clearances and bearing clearances, different rods and crank shaft balance isn’t as quiet as the stock components settings are. Here’s a rear dyno view, exhaust is clean as a whistle start to finish

 

[Speedy!]

Put some race gas in it and test?

Mine would get 6deg stkr after the 2.72 until I tweaked it...on race gas.

 

[jonx96]

Put some race gas in it and test?

Mine would get 6deg stkr after the 2.72 until I tweaked it...on race gas.

Wow I am surprised your 2.72 being the hellraiser made that much noise.

 

[Speedy!]

It's the supercharger rotors I think.

 

[fumanchu182]

I guess it’s time to start running Sunoco 260GT 100 octane fuel mixed with race gas?

i mix this with my race gas, 93 🤣

I must of missed mention of a knock issue. In any case I think 11.66 afr is a sweet spot. I always shoot for 11.4 - 11.6 for a street tune. That's .83 lambda on the Hellcats 13.85 stoich. I go for .81 on E85. I'll bring in a tick more fuel above 6000 as a safety.

Knock can be a funny thing on these cars when a smaller pulley is installed. I always start with known high octane fuel to dial that in.

WOT trims should be easy to sort out.

im hoping, tomorrow im going to the track!

 

[Hickster]

Lifters??

 

[16GoManGoHC2]

Lifters??

Please explain Hick, lifters?? Being a source of the noise you sayin’?

I’ve been thinking of adding one of these to my tool bag. Anyone ever use one??

https://www.plex-tuning.com/products/plex-knock-monitor-2/

 

[hellman]

It's the supercharger rotors I think.

Hey Speedy, what timing we’re you running with your combination using 105 octane fuel? Just curious how much extra timing you could run over 93 octane. I think I saw a post of yours that stated you were running 4-5 degrees more on 105 octane race fuel? What performance gain do you think you would get by tuning a stock boosted car on 105 octane race gas over 93 octane? Is there a point where the extra timing stops making a difference. I think I remember a car out there running stock boost tuned on Sunoco 260GT+ (104 octane non-oxygenated) fuel pushing 22 degrees of timing running 10.01 in good DA. Is tuning on race gas basically worth about a 1/10 with that extra timing. I think that is what I was remembering. Thoughts???

 

[The Max]

Lambda this and lambda that, isn't that a fraternity in some movie.

After reading this thread, and it's extremely informative, I wish for the days of carburetors and points when you could easily adjust things very simply.

Seriously, when full throttle in my Hellcat there is so much noise upfront and even more from the rear. How the hell can those knock sensors do anything but sense pure power

 

[BULL]

Lambda this and lambda that, isn't that a fraternity in some movie.

After reading this thread, and it's extremely informative, I wish for the days of carburetors and points when you could easily adjust things very simply.

Seriously, when full throttle in my Hellcat there is so much noise upfront and even more from the rear. How the hell can those knock sensors do anything but sense pure power

It's a double edged sword, points and plugs and a simple carb left a lot of untapped power (and fuel economy) on the table.

This is what we get to deal with for getting 700-800 hp and 20+ mpg.

 

[jonx96]

If teachers would have just taught math with vehicle tuning as examples. Maybe I would have paid close attention

 

[Speedy!]

I used to hate math LOL.

Hey Speedy, what timing we’re you running with your combination using 105 octane fuel? Just curious how much extra timing you could run over 93 octane. I think I saw a post of yours that stated you were running 4-5 degrees more on 105 octane race fuel? What performance gain do you think you would get by tuning a stock boosted car on 105 octane race gas over 93 octane? Is there a point where the extra timing stops making a difference. I think I remember a car out there running stock boost tuned on Sunoco 260GT+ (104 octane non-oxygenated) fuel pushing 22 degrees of timing running 10.01 in good DA. Is tuning on race gas basically worth about a 1/10 with that extra timing. I think that is what I was remembering. Thoughts???

A good race gas tune is probably worth around 3/10 all things considered. You might eek a little more out with good trans tune changes as well you just have to be careful and not get greedy. The best thing about custom tuning is you can start to tweak the car for track conditions. As an example at ChallengerFest 10 I ran several passes and kept going 10.1 to 10.2. It was spinning a bit off the line and very frustrating. I showed a log to Mike from OST and he showed me how to make a tweak that actually pulled power out and I ran a 9.8x next pass.

 

[Mean Cat]

Please explain Hick, lifters?? Being a source of the noise you sayin’?

I’ve been thinking of adding one of these to my tool bag. Anyone ever use one??

https://www.plex-tuning.com/products/plex-knock-monitor-2/

That says discontinued ?

 

[Magnified]

I used to hate math LOL.



A good race gas tune is probably worth around 3/10 all things considered. You might eek a little more out with good trans tune changes as well you just have to be careful and not get greedy. The best thing about custom tuning is you can start to tweak the car for track conditions. As an example at ChallengerFest 10 I ran several passes and kept going 10.1 to 10.2. It was spinning a bit off the line and very frustrating. I showed a log to Mike from OST and he showed me how to make a tweak that actually pulled power out and I ran a 9.8x next pass.

Math rules the world!