The stutter's back at around 2000rpm.

I haven't changed the spring tension in the converter, only in the mixer. The stock converter keeps up to around 5000rpm so I don't spin it right out on LPG. Not sure what you mean by 50/50 balance Joe.

I don't have the specs on the tune, I'm still using the generic Raptor tune done by RDP.

From one of my posts today on AFF:



So it looks like you were right weeks ago Joe about a possible problem with the converter being masked.

Tony what a 50/50 balance is, is that you screw the idle screw all the way in & have it running on the sensitivity screw, then roughly 1/2 a turn back on the sensitivity screw & smooth the idle back with the idle screw, that might get rid of that stumble also what are your plug gaps & do have a dyno a/f reading if your having to constantly reset or play with the mixtures do the convertor undo the drain bolt if you see a bark brown coloured oil the diaphrams contaminated & streteched get it re-kitted

Joe

Great thread, can i ask? On page one you said that you advanced the cam 4*, can i ask the advantages behind this? is it to generate more low down torque or is that because it suits your s/c and or gas better?

Cheers.

I've been making small adjustments today & going for a run after each. Seems to be going OK ATM. There's a stumble at around 1000rpm on a very light throttle. Step into it though and it chirps the treads as it takes off. But what I've been finding lately is that settings that work one day are no good the next.

I've arranged a re-kit and will do the washer mod at the same time.

Plugs are gapped 0.85mm. A/F on LPG when I had it dynoed dropped into low 11's, maybe 10's, before climbing back to 14 up top.

Thanks for the info on 50/50. I'll give it a try, although I've had the best results so far with less sensitivity and more idle. Bit hard to tell sometimes, the variable mixer adds another variable. I guess the gas passage opens up as the venturi opens, allowing it to flow more gas?

I advanced the cam 4* last year when the car was still NA as it had felt to be short of low-down torque for quite a while. Turned out to have a collapsed cat which I replaced & got a fair bit of performance back. At the moment it doesn't seem to be hurting the midrange or top-end, so I've just left it. I'll probably set it back to stock when the time comes to do the emissions test as I guess it may have some effect on emissions.

Ok fair enough thanks.

only reason i ask as im getting both max HP and Torque at 4000rpm and it just smoking the treads 1st & 2nd (manual) and i was considering retarding it maybe 2* more (already at 2) to try and get it to rev a bit better and have some more top end but when i saw you had advanced 4 i was considering the benifits. Then again a six and a eight a two different machines.

The old girl got relegated to a project shortly after my last post and spent nearly 2 years in bits in the shed, just being put back together to be inspected for rego. Last rego check it was idling like total shight and the mechanic who did the pink slip did a bit of troubleshooting for me. He's a bit of an enthusiast, has built some LPG 350's with topmounts in the past & seems keen to see this succeed.

So, he spent a few minutes checking things (and didn't even charge me) and found that my intake manifold gasket was leaking around cylinders 5 & 6. That was probably causing the hassles I was having before.

When my current daily drive got shoulder-charged by a big roo just before Christmas, I got motivated to replace the offending gasket. In the process I found one of the wires on the crank position sensor was worn or rat-chewed (or the K-Rudd equivalent!) through to only having 2 strands remaining. So I fixed the wiring while I had the manifold off.

Long story short, the old girl now runs a s**t better. Smooth idle, no stutters, snappy takeoff and a nice surge from midrange to redline.

It had still been very rich at the top end on petrol. Due to the lack of tuning options locally, I worked around this at first with 20% smaller injectors bought through ebay. They were advertised as XR6T injectors but were black rather than dark blue. They turned out to be BA V8 injectors as used on both 3V and 4V engines. Same nominal flow rate @ 3 bar as the XR6T units. Dunno why they're different, but they seem to work.

This made the bottom end lean on petrol, so I bit the bullet and bought a Sniper (no I didn't intend the pun, sometimes s**t just happens) and gradually enriched the mixture from idle to 2300rpm. Much nicer on petrol now.

Once the gasket was replaced, it ran fine on gas straight up. Consumption was awful though. How about 17l/100km at a steady 109km/h on the Great Cash Cow (aka Hume Freeway) during a trip to the Police State? I replaced the O2 sensor a couple of weeks ago and tried MacGyver's procedure for tuning the LPG (which sounds like 50/50 as Joe described above) and on the first tank of LPG since, I got 15.2l/100km for half highway, half town driving with a bit of getting up it thrown in.

I'm still keeping it under 5000rpm on LPG just in case. I need to find the LM-2 which has also been in the shed for more than 2 years and get some logging happening. I'm thinking I'll make the wideband O2 a permanent fixture in place of the stock O2 sensor, using an LC-1 to provide narrowband emulation to the PCM. Then I can plug in either the LM-2 or a gauge to the LC-1's wideband output as needed.

That will hopefully let me get the tune spot-on on both fuels. There is still a very slight hesitation on petrol when giving it full throttle from a standing start, so the low-rev load points need just a bit more tweaking. But it's gone past the point where the seat of the pants is enough to judge what's needed, I need to get logging going.

But it's a long way better than it was before I got the Sniper. Some days it wouldn't pick up revs at all from a standing start until I backed off the throttle. Like chalk & cheese now.

And one thing I need to do is quieten the exhaust a bit. Under load above about 2600rpm it roars like a tiger with its balls caught in a rabbit trap. I haven't been arrested yet but I have to be very careful around town. A bit more noise suppression wouldn't go astray, even if it costs me a few kW. A couple of kW is cheaper than a few $hundred.

I've finally found someone who's made a credible suggestion for quietening my exhaust a bit without choking it right down or going to the expense of dual smaller pipes. The old girl goes in for "surgery" tomorrow, so I finally got off my Lucky Grills and made a little vid of how it sounds now. If you listen carefully you can hear the Raptor on the overrun. Enjoy!

http://www.youtube.com/watch?v=afCx5BGUDr4

Hope it works OK, I was a YouTube virgin until now.