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Back story first,

I had been spec'ing my 97 Spak toward Series 3 Maloo, but End of last year, it was written off...


So I sped up the process and now I have a VS Series 3 Maloo


When I bought the Maloo it already had a gas system on it (sprint gas, not injected type)

Now my plans are to convert it over to manual and at the same time give the engine a freshen up and put a set of flat top pistons in to get some more compression for a bit more response/power.
I have never done anything with gas before so I'm not sure how it will go with higher compression and tuning. My research suggests that LPG is higher octane so works well in hi-comp engines but I have not found anything to say what it's octane rating actually is and how this applies to dual fuel.

Onto the tuning side, while I had an NVRAM conversion in the Spak running DRRR, I never got around to installing my wideband so didn't do any real tuning only modifying the flags and a couple of tables to get it where I wanted it.
Long term I want to set up a memcal with 2 tunes which will switch with the gas change over, but in the mean time I'll be running the NVRAM to be able to realtime tune.
Will tuning on petrol cause issues when switching to gas? I currently run 95 octane but might go over to 98 if I need to after I doing the engine mods.

Ideally the final setup will be gas for economy and petrol of performance as this is my daily.

If anyone can advise me on whether or not I am on the right track would be greatly appreciated. At the moment I am just going by what a couple of mates have suggested with improving the 5L V8 and scraps I can find on the net. Not game to ask the 'experts' on commodore forums

Cheers,
Troy

Current spec:
HSV VS Series 3 Maloo Auto (100% stock but with after market gas system)
5.0L V8 195i (HSV roller cam) running stock CNPD/DRRS
Gas Sprint Gas AEB 295 Controller

Immediate Upgrade plans:
T5 Manual
NVRAM with DRRR
Engine-> New bearings, timing chain, ARP studs, flat top pistons (Hypatech), SS exhaust valves, gasket set, welch plugs
Exhaust-> Fit my old exhaust with left and right bungs for wideband O2 (Ceramic Pacemakers into twin 2.5" HiFLow Cats into single 3")

Future Upgrade plans:
Thermo fans AU, goign to see if I can get PCM/BCM to control them.
VT series 1 serpentine belt setup.
Statesman body loom and climate control
Modify stock banana manifold with bigger throttle body and MAF, no elbow and OTR

http://en.wikipedia.org/wiki/Octane_rat ... _.28RON.29

112 RON according to wiki. LPG is propane right?

From my reading it's a propane/butane mix that changes with the season. Never thought to look on Wiki for RONs that table shows butane as 94 and propane 112 so you'd assume it's going to be somewhere between those two. Therefore, if I tune on 95 petrol, I should be well and truly safe.

Cheers!

Heres some stats for different fuels. LPG should be able to make more power than premium 98, but you would need LPG injection to do it. Old school LPG might both mean wasted LPG potential, and an intake restriction on petrol

definately not an issue to run higher compression and if you keep the old school gas mixer you might be able to run more than you think as the cylinder fill through those is a bit on the poor side of things. from memory if you put flat tops in there is still room to take a bit off the top of the block with a standard cam.

Awesome, thanks guys, this is making me feel much better!

Thanks for the table antus, that also answered my next question of what the AFR on gas is likely to look like.

I'm going to look into the possibility/cost of injected gas somewhere down the track.

Troy

Helical wrote:Thanks for the table antus, that also answered my next question of what the AFR on gas is likely to look like.

Well, there is another half to that story. AFR is the air fuel ratio, on the input side before the bang. The O2 sensor measures the remaining oxygen in the exhaust. It actually measures lambda, where lambda 1 means stoich regardless of type of fuel. When your wideband displays AFR, it is converting lambda to AFR based on the assumption of fuel you are running (normally petrol). So, for LPG if you do not reconfigure the wideband, when it shows AFR of 14.7 its telling you lambda 1 stoich which really means AFR 15.5 for LPG. Until you look at LPG injection, this is not something you need to worry about. If you have the appropriate licensing to touch LPG and are just trying to trim the LPG mixtures with an old school mixer based on the wideband, then you can either reconfig the wideband for LPG and look for AFR of 15.5:1 or leave it as is and tune it like its petrol. You will get the same result. Technically it would make more sense for widebands to just tell you lambda always (most can) so you dont have to worry about the type of fuel, but its just not the norm.

That makes sense, I'm not licensed nor game to tinker with LPG atm so if I notice it's out I'll find someone who is.

Cheers,
Troy

Too true about lambda I wish I had started out tuning just using lambda as it simplifies everything now I just keep doing it the way I always have. Gas takes up a lot of room in your inlet tract especially when its through the old school mixer so you can get away with running fairly high comps.

lpg pumps in NZ say 98 octane on them