alky % and a/f change revisited!

[norbs]

A question for Razor.....

According to some calculations,

This is based on the following formulae from innovate forum:

sAFR = (%ofAdditive * sAFRadditive + (90-%ofAdditive) * sAFRgas) /100

where:
sAFR is resulting stoich AFR
%ofAdditive is amount in % of mass of additive (methanol) mixed in
sAFRadditive is stoich AFR of additive (6.4 for methanol)
sAFRgas is stoich AFR of base gasoline (14.7)

For a 10% mixture of methanol to gasoline by mass the resulting stoich AFR is 11.95

So, for an engine that's tuned to certain AFR at a certain load and RPM on straight gas, the resulting (gasoline equivalent) AFR when running the mixture can be calculated as:

new AFR = tuned gas AFR * (gasoline stoich ratio) / blend stoich ratio

An engine tuned to 11.0 gas AFR (which your wideband will show if its set for gas) will run at the equivalend of 13.5 gas AFR with a 10% methanol blend.

 

[norbs]

Just ignore all that crap, just tune to 11.3~8 and leave it alone, i have foiund out it doesn't matter what fuel you use.

 

[Bens87tr]

1st post was on September 10th. I don't know Norb, but it looks like we have been ignoring that... :wink:

 

[DMan]

Norbs,

I didn't check your math in detail, but the stoich afr will change as you blend fuels. If you've got one of those Innovate meters and blending fuels like all us alky guys do, I think the best thing you can look at is LAMBDA instead of AFR, and tune for a lambda of 0.9-0.8 at WOT.

A question for Razor.....

According to some calculations,

This is based on the following formulae from innovate forum:

sAFR = (%ofAdditive * sAFRadditive + (90-%ofAdditive) * sAFRgas) /100

where:
sAFR is resulting stoich AFR
%ofAdditive is amount in % of mass of additive (methanol) mixed in
sAFRadditive is stoich AFR of additive (6.4 for methanol)
sAFRgas is stoich AFR of base gasoline (14.7)

For a 10% mixture of methanol to gasoline by mass the resulting stoich AFR is 11.95

So, for an engine that's tuned to certain AFR at a certain load and RPM on straight gas, the resulting (gasoline equivalent) AFR when running the mixture can be calculated as:

new AFR = tuned gas AFR * (gasoline stoich ratio) / blend stoich ratio

An engine tuned to 11.0 gas AFR (which your wideband will show if its set for gas) will run at the equivalend of 13.5 gas AFR with a 10% methanol blend.

 

[Mad_Trbo]

Just out of curiousity, do you have the ability to monitor lambda?

I took class on tuning from EFI101 and I undrstood that if you are going to blend fuels you can monitor lambda and tune for a specific point without having to worry about the blends you are using.

Just a thought. I know you guys have little respect for the rice burners out there. But I have my DSM which is tuned to run at about .78 - .80 lambda reading with methanol alky spray. Car conservatively produces around 350 wheel hp on an all wheel drive drive train. I am completely looking forward to seeing what I can get from my 87 T-Type.