Propane stroker?

[Heepofajeep]

You'd have almost identical HP/TQ outputs from propane with an 11.0:1 CR as you would from regular gasoline with a 9.25:1 CR. No worries about detonation either since propane has a 104 octane rating and burns a lot slower than gasoline.

Just curious why you say that? [I don't know either way, I am just curious].

 

[Dr. Dyno]

Just curious why you say that? [I don't know either way, I am just curious].

The reason is that one pound of propane doesn't produce as much energy as one pound of gasoline so if you kept the CR the same after the propane conversion, you'd see a HP/TQ loss of about 5-6%. You can compensate for that by raising the CR and that isn't a problem with propane.

 

[Chancer]

Would raising the compression ratio threaten the overall reliabliity of the engine? Keep this thread going - I'm learning lots - I aspire to doing the same...

 

[jwtrapper]

My major question is what do you do with the computer? Wont you still need it for timing? Or is there a way around this? I have been looking into lpg for my xj as well but what do you do about the computer? I could realy care less about the check engine light. Its on right now anyways.
As a kid I lived on a large ranch in Texas and all of the ranch trucks where on propane.

 

[XJJack]

Not sure what the smog laws would say, but I would pull the computer out of that loop aswell, just use a distubuter with a pickup and wire in HEI and time it the old fashioned way.

 

[English XJ]

Any ideas on an optimum compression ratio to run primarily on propane (LPG) but also on gasoline.

My LPG conversion is effectively dual fuel, staring on Gasoline, then switching when at temperature. If I run out of LPG I sometimes have to travel some mileage to the nearest LPG station.

So, given that I have easy access to European 97 RON Fuel (about equivalent to US 91 I believe) and only run on it for short to medium distances and time - what would an ideal compromise compression ratio be?

I have already started to build the stroker but could alter CR by milling block and/or head. How much would a 0.010"/0.020" etc. mill of either/both increase CR given a build-up almost identical to Dino's?

Sorry for the length of question, just wanted to try and provide all the information. AND Thanks to all you guys for getting me started on the stroker.

 

[Dr. Dyno]

I have already started to build the stroker but could alter CR by milling block and/or head. How much would a 0.010"/0.020" etc. mill of either/both increase CR given a build-up almost identical to Dino's?

If you copy my stroker but mill 0.015" from the block deck, the CR will be 9.5:1 and that's as high as you'd want to go with the Crane 753905 (or 753901) cam. When you switch over to LPG, you'll see a ~5% drop in HP/TQ compared with petrol but at least you'd be able to run the cheaper 95 RON juice (91 R+M/2) instead of 98 RON.

 

[English XJ]

Thanks Dino, that sounds like a pretty good compromise.

I'll update you when the block comes back and I can get to work on the assembly.