Whats the best boost AFR

[boosted4runner]

make the whole map 0-100kpa 14.7
then slowly ramp AFR to your desired target AFR

[Holden202T]

why would you make the 100kpa area 14.7 ?

[boosted4runner]

A turbo engine isnt under load till it has boost
You are wasting fuel if you make it any richer off boost

[Holden202T]

well thats a new concept i'd need to get my head around

[VX L67 Getrag]

a lot of different software's have different concepts of kpa, but yeah I know what both of you are saying but different softwares do different things!
But in this instance 12.8 to 100KPA 14.7 for stoich & then stagger 110Kpa upwards!

[darcy]

How is engine load different at 100kPa for a boosted vs non-boosted setup?
At 100kPa the same air mass will enter the cylinder, irresepective of a charger being able to deliver more.

[Holden202T]

yeah thats what i would have expected too and if thats the case, you would find you'd get a lean hesitation at 90-100kpa before boost came on ? and i dare say that would also adversely effect spool etc etc ?

[charlay86]

well stoich is going to have nice hot exhaust gasses for spooling the turbo.
but what if you have a massive turbo that takes forever to spool up.. surely one would want to tune the vacuum areas for power to afford some reasonable level of accelleration prior to achieving positive manifold pressure?

[v6bucket]

If your using methanol in this engine, be careful using petrol AFR numbers with methanol, methanol has a "best power" figure of .75 lambda, where petrol is .88 lambda which when converted back to petrol figures is 11.02 for methanol & 12.9 for petrol.

[Holden202T]

i will be using methanol with my boosted motor but i have kept everything in this thread petrol based because thats what most people would understand.

i have been making my methanol boosted tables in the back ground

its funny you mention the .75 lambda for methanol i never knew this, this correlates to 4.8 afr, i found on the dyno my engine made better power at 5 afr rather than 5.4 which is approx 12.4 in petrol terms, i also tried richer because the v6 sprintcar i dynoed was happier at 4.8 too, but mine didn't seem to get the same improvements, maybe something to do with my extra compression compared to the v6 stock compression im not really sure.

also going off my 100kpa methanol AFR's of 5 and transferring that into the boost table it gets to 4 afr richest, so thats 9.2 afr in petrol terms

that said methanol seems to work better richer in my experience and be less effected by hp loss too when rich! plus it should almost freeze the inside of the engine with that much going in there