Is it possible to have Fuel Mixture bellow 15:1

Like the title says… just a thought :wink:

Yes it is possible. I believe the air/fuel mixture you choose is the full throttle air/fuel mixture. When you use Direct Injection and a power mixture of 15:1, the cruising mixture is something like 25:1 or close to that. It should say the cruising mixture when you are using this slider. But… if you are talking power mixture below 15:1, I am sure it is possible, just probably wont produce much power.

Between 12 - 12.5:1 seems to produce the most power.

That is what the real world tuners get when they map real world engines.

Chemical correct ratio for normal gasoline is 14.7:1.

These are for max power, cruising is leaner ratios.


I know for a fact that the ideal fuel mixture is called a Stoichiometry mixture :geek:

Geek warning! :wink: :ugeek:

The mixture with the best fuel efficiency is 15.6. anything lower than this will will result in less efficiency.
keep in mind this is at full throttle and for MPI

Then why isn’t the minimum mixture 15.6:1?

The mixture number in the game (that you set) is the number for “power enrichment”. The cruise number is also given and can go into the 30s if you use direct injection.

In real life or in the game, 15.6 afr’s are dangerously lean at full throttle.

the lowest possible is 15:1 and the highest you can go is 10:1 that is what Daffy and the other programmers built in…although I would like their feedback on this please

Even 15:1 is so ridiculously lean for full power mixtures, you’d have a very hard time making that not explode and melt pistons etc IRL.

I run my engines usually around 13.3:1 to 12.5:1 or even right up at 10.0:1 if its a super powerful V8 big block with lots of BOOOOOOOST on it

very lean mixtures like 15 or less have difficulty igniting, just like ones that are too rich. unless the engine has suffcient compression and advance.also, it does burn very hot, but will not necessarily knock.

as a note: diesels operate with a very wide range of mixtures. they work with anything between 3 and 48:1. and stoic is 14.6 for diesels (yeah , pretty close to petrols. after all,they are related, but if it runs at this mixture, it will hit 6000 in less than a second if not under load)

speaking of lean burns and economy in general - take a look at Hondas VTEC-E it disengages 1 intake valve at low RPMs to allow leaner burns and make it more economical

read up -

i have no idea on the mix values though

I think of VTEC as the work of the Devil myself so it has variable Mixes me thinks

I would really like to see lean burn petrol engines as well. I know the “engine designer” part of the game is now locked, but unlike adding diesel or electric other alternative fuel systems this would not require large changes, perhaps it could be added fairly quickly after the game is finished as a balance patch.

As regards the AFR representing “full power setting” and therefore the engine still has the ability to go over 15:1 at part throttle, no that is not what is meant by lean burn. Conventional engines run stoich at part throttle then go rich at WOT to prevent knock.

Lean burn engines run stoich at part throttle then go lean at WOT to prevent knock, since detonation risk is highest at stoich and decreases the further your AFR departs from it.

Obviously, a lean burn engine will make less power than a rich one , but since we don’t have diesels, i’d like to make a large capacity , long stroke pushrod truck engine with low max rpm, turbocharging and a full throttle AFR of 22:1 or so.

Rich of Stoich

  • More power, up to a point

  • Much worse emissions

  • Much worse economy

  • Lower RON

Going lean

  • Much worse power
  • Slightly better economy
  • slightly worse emissions
  • lower RON

Misfire eventually becomes an issue, lean burn engines tend to have seriously beefy ignition systems. However, high BMEP / boost offsets that to a degree, it’s a lot easier to ignite a lean mixture under the sort of conditions where it would knock at stoich, than it would be igniting the same AFR at idle.

Though eventually you get into a bit of a coffin corner between misfire and detonation if you keep jacking the boost up.

6 years later … try not to bring up long dead threads please.


Would you rather he make a new topic then be told to use the search function?

Well, it’s certainly less worse than reviving an old thread for the singular purpose of making a ridiculously unnecessary comment.

Replies to a necro.

To necro it again.