Outer Limits 4x4 Board

I was thinking of injecting methenal or small amounts of toluene at higher boost levels to stop detenation. I ve read everywhere that gas has a higher octane than pump fuel like 100-110 or something but it seems the power figures are similar between pump fuel and gas motor's with similar setup's. Avgas has about 100-105 octane and you can run 11 to 12to 1 comp ratio's, gas not a chance. Either the fuel company has diluted it down heaps now with butane and other crap and hasn't told us or it was never that high in the first place. ust wanted to know other people's thoughts on the all important matter of making more power.

Do you have a decent intercooler? LPG octane is offset by high air temps, what sort of total timing and boost are you running? LPG hasn't has 105 octane since butane was added, it's characteristics are very similar to premium 98 these days. Depending on cooler, compression ratio, camshaft and few other details you can run up 30 psi.

Joel

My intercooler is front mount 600x300x75 outlet piping always cold/ambient after a thrashing. It hasn,t been dynoed yet hopfully 2weeks, so its very hard to tell if there is detonation or pinging while driving. Running 14deg locked timing @10psi stock motor turbo t4/t3 .7 cover .69turbine 38mm waste gate crane ign bp7es plugs head has been recoed and modified chamber (88cc)relieving around valves while keeping as much quench area as possible. It seems to be fine but 14psi goes heaps harder but scared ill bust another head gasket, that will be number 4 from detonation. I have a a/r meter fitted andruns 12.5 most of the time. How else can I detect pinging with out spending hours dicking around on an expensive dyno. Could I fit a knock senser. Keen to here your thoughts.

dont forget forklift gas has a higher octane rating aswell

Fork lift gas? why would they need high octane gas? do you know this for sure, sounds interesting could rig something up for dyno runs.

Thats 100% propane like BBQ gas, it has lower carbon emissions so suits indoor use more.

12.5: is that ULP or LPG AFR? The calculation is based on Lambda, which is always consistent regardless of fuel. Due to LPG lambda 1 being 15.5:1 and PULP and ULP being 14.7: then 12.5:1 using an LPG calculation is different to 12.5:1 on ULP. 12.5/15.5= 0.8 Lambda wheres 12.5/14.7=0.85 lambda. If that makes sense. I won't tell you what to run but you see the difference?
I've run well over 14psi on these engines, but they have been purpose built, generally I stop around 12 on a stock motor. It gets very technical but more boost dosent always equate to more power, if you are pulling excessive timing to stop Knock with high boost the power may not be any higher and the EGT's are much hotter. I try to tune turbo vehicle to the sweet spot which is dependent on Octane rating, boost, IAT, camshaft and so on.

Joel
Cheers

Joel

Finding out optimal timing and a/f ratio is hard. Seems like closly guarded secret, I appreciate the time and effort in getting the results on the dyno but hey where all mates here chasing the same thing HORSE POWER! If I injected Toluene into the gas mixer would it increase the octane of the lpg or just extend burn time?

If the optimum timing can't be worked out by the dyno operator find another dyno operator. In regards to mixture I will say that too lean means too hot and potential engine failure, dropped valve head, brocken rings seizure etc. Too rich will mean low power and poor economy. One of the reasons I don't broadcast AFR's on line is I don't want to be held accountable for someone toasting an engine as AFR's are relative to the vehicle, application, weight and so on. Suffice to say I richen our comp trucks when they do the Outback challenge and Cliffhangar compared to the Victorian winch comps as the amount of time under full load is critical to heat soak and ultimate engine life. A 9 sec drag car can be leaner than a 3 ton truck that is required to run at high power for 3 hours up a rocky creek.
Joel

Yeh fair enough see your point. I'm just having trouble finding the right person for the job. I'v got to take it to someone who knows turbo's, with gas reseach in a 4wd patrol. Don't what to be a guinea pig for someone with half a clue. Wish I lived in victoria I'd just take it to you guys no problems.