Outer Limits 4x4 Board

I was told be a mechanic that when an engine is total LPG you should remove mechanical and vacuum advance in the distributor. Then run the timing at 30 degrees. Does this sound correct? Whats the best way to setup and tune a total LPG engine?

you mechanic sounds like a dick head.


although LPG like a little more initial advance and a little less total advance.
leave you vacuum advance working. Just remember every engine is different.

If you have duel fuel the best you can do is run premium and set the timing on a dyno (power time) at peak torque which will usually allow you to add a couple of degrees.
LPG burns slower at low rpm and faster at high rpm hence what brad-chevlux said is exacly correct. Leave the vac on, for economy more vacuum at cruise will always help, it compensates for the slower burn speed due to poor mixture turbulace at light throttle.

Cheers


Joel

So are you saying disable the mechanical advance but leave the vacuum advance on?

no i'm saying if you are going to run LPG only, you could have your dizzy regraphed to suit. (have the mechanical advance curve changed.


minor edit

No I'm saying don't touch it aside from getting onto a dyno and adjusting the base setting to acheive peak torque at peak torque (the rpm peak torque occurs) on premium. The mechanical advance can be modified but it takes an hour or so on the dyno with an advance timing light to find the peak torques at numerous rpm and load sites and then having the distributor re-graphed on a distributor bench to match. In your application the gains probably wouldn't justify the cost.

Cheers

Joel