V-Twin Forum banner

1 - 4 of 4 Posts

·
Registered
Joined
·
116 Posts
Discussion Starter #1
Anybody have any feedback on spark timing vs boost? A roots-type blower makes boost basically from idle, so that would seem to indicate retarding the timing at low rpms, but how much? I have read 2 degrees per pound of boost. And then how agressive an advance curve? I have 10 advance curves to choose from, going from much slower than stock to much faster than stock. I hope that the tuner will know his stuff but I also want to know enough to be able to tell if he knows his stuff...
 

·
Banned
Joined
·
128 Posts
03FXDL said:
Anybody have any feedback on spark timing vs boost? A roots-type blower makes boost basically from idle, so that would seem to indicate retarding the timing at low rpms, but how much? I have read 2 degrees per pound of boost. And then how agressive an advance curve? I have 10 advance curves to choose from, going from much slower than stock to much faster than stock. I hope that the tuner will know his stuff but I also want to know enough to be able to tell if he knows his stuff...
Tuning a forced air motor is a whole different ballgame. Better hope that tuner does alot of SC and T'd engines on the dyno. Not many tuners around that have any experience with boost. Heck, most tuners are marginal when it comes to naturally aspirated.

I would be VERY conservative in your timing since you have no intercooling on an air cooled engine thats going to get real hot internally.

BTW did you lower your compression or switch to forged pistons?
 

·
Registered
Joined
·
116 Posts
Discussion Starter #3
MechaGodzilla said:
Tuning a forced air motor is a whole different ballgame. Better hope that tuner does alot of SC and T'd engines on the dyno. Not many tuners around that have any experience with boost. Heck, most tuners are marginal when it comes to naturally aspirated.

I would be VERY conservative in your timing since you have no intercooling on an air cooled engine thats going to get real hot internally.

BTW did you lower your compression or switch to forged pistons?
Yes I am quite concerned about getting a tuner with knowledge of boosted applications. There is a company here in the valley called ECS Dyno that says they do alot of blown and turbo bikes so I'm going to use them.

I did not lower the cr or install forged pistons. My cr is 9.1:1 or maybe a tick less. The boost level is low and I don't plan to run it hard.
 

·
Banned
Joined
·
128 Posts
03FXDL said:
Yes I am quite concerned about getting a tuner with knowledge of boosted applications. There is a company here in the valley called ECS Dyno that says they do alot of blown and turbo bikes so I'm going to use them.

I did not lower the cr or install forged pistons. My cr is 9.1:1 or maybe a tick less. The boost level is low and I don't plan to run it hard.
If your at 9:1 or lower your actually ok and can probably boost the psi a few pounds more, but you should still be running forged pistons. Those cast pistons will be toast soon if the motor isnt tuned well. You should run a forged piston if you want good long term reliability.
 
1 - 4 of 4 Posts
Top