Cosworth power blocks

[Soloside]

Originally Posted by FRSBRZGT86FAN

That hilariously untrue, that's dictated by how your tune handles fueling tables, AFR and load tables. Driving comparatively, I can get the same MPG with the Stage 2 UEL 93 octane tune as with the stock tune with stock UEL. I've made considerable tune edits to my 93 tunes to achieve this without loss of power, of course when I'm flooring it all the time the 93 tune will do worse than flooring it with the stock uels and tune, obviously the trade off for more power.

stock factory tune for a stock car is the most optimal tune in terms of MPG/POWER am I not correct?


Unless you're telling me adding more power throughout the band is going to improve your mpgs

[bfrank1972]

Originally Posted by Soloside

stock factory tune for a stock car is the most optimal tune in terms of MPG/POWER am I not correct?


Unless you're telling me adding more power throughout the band is going to improve your mpgs

Not really - factory tune is usually a compromise with large safety margins built in to ensure reliability with a variety of fuel qualities, environments, and usage conditions.

Specifically, aftermarket tune gains mostly come from optimization of timing advance and fuel mixture. Factory tunes usually run slightly richer than what's optimal for power, and less timing advance than what's optimal for power - both will ensure somewhat cooler cylinder temps, slightly lower cylinder pressures, and more protection against knock. Aftermarket tunes push AF ratios & timing advance curves closer to 'optimal for power'. But more optimal AF ratios & timing advance also equals better MPG. This is oversimplifying things a bit but in general optimized factory tunes should return better power AND MPG while sacrificing some margin for knock/reliability in less than ideal fuel conditions.

[Soloside]

Originally Posted by bfrank1972

Not really - factory tune is usually a compromise with large safety margins built in to ensure reliability with a variety of fuel qualities, environments, and usage conditions.

Specifically, aftermarket tune gains mostly come from optimization of timing advance and fuel mixture. Factory tunes usually run slightly richer than what's optimal for power, and less timing advance than what's optimal for power - both will ensure somewhat cooler cylinder temps, slightly lower cylinder pressures, and more protection against knock. Aftermarket tunes push AF ratios & timing advance curves closer to 'optimal for power'. But more optimal AF ratios & timing advance also equals better MPG. This is oversimplifying things a bit but in general optimized factory tunes should return better power AND MPG while sacrificing some margin for knock/reliability in less than ideal fuel conditions.

ahh I see. Thanks for the explanation!

[FRSBRZGT86FAN]

Originally Posted by Soloside

stock factory tune for a stock car is the most optimal tune in terms of MPG/POWER am I not correct?


Unless you're telling me adding more power throughout the band is going to improve your mpgs

@bfrank1972 took the words right off my keyboard



In a way you are correct:

The stock tune is optimized for the best timing, and AFR for the stock header and air filter. Its also covers a "wider range" of fuel types from 87 (worst case against owners manual recommendation)-93 (best case but is still held back). They also have been data-logged and proven to run unnecessarily rich in most cases, thats why stage 1 tunes are showing better MPG and power than stock in most cases. In a sense we trade the reliability and convenience of perfect performance in all conditions and fuel types for more specific fuel.

For running a turbo of course you can't compete with NA MPG numbers as you need to add fueling and timing to compete with higher density of air.
For me and you running e85 as well there's no way we can ever get the same MPG as stock because e85 is 15-27 percent less efficient due to the fuel having less energy.

Its pretty complex but OEM tunes leave a lot on the table as far as power and efficiency is concerned on most vehicles.