Memcals and Gas settings

[FXST01]

What maps/fields should be changed in a memcal when a car is on gas?

What maps/fields should be changed in a memcal when a car is dual fuel?

[FXST01]

Anyone? well then cue the tumbleweed

[delcowizzid]

well if its holden it seems nothing is changed at all in the early model duel fuel tunes.they just turn injectors and stuff off when you flick to gas.if anything spark would be the only thing needing changing to suit LPG more if it was dedicated lpg but duel fuel they leave it the same so it runs fine on both

[VTSSDUDE]

Doesn't gas have it's own management system. So wouldn't matter how you tune the memcal. So on fuel you can have your tune and gas, it's gas.

[delcowizzid]

gas only has fuel adjustment itself via the mixer.as for spark it should all be controlled by the ecu still

[rob drag racer]

well if its holden it seems nothing is changed at all in the early model duel fuel tunes.they just turn injectors and stuff off when you flick to gas.if anything spark would be the only thing needing changing to suit LPG more if it was dedicated lpg but duel fuel they leave it the same so it runs fine on both

spark was what i was told two i suppose if ya run ya car on lpg the most it probably wouldn't hurt to have the spark done ?

[delcowizzid]

back in the day when i had LPG HQ's they had a duel fuel dizzy that swapped spark curves when you swapped fuels gave extra economy on LPG so there would be gains on LPG for sure .

[rob drag racer]

don't relay apply to me now seeing im getting into the eb until the warmer weather when i rebuild the vp thought id ask just to clear it up lol

[DavoVP]

Yes, the ignition curve should be adjusted, you can run quite a bit more advance down low then trail it off, i cant remember the exact figure's sory.

But with that being said itl run fine on the original petrol timeing curve, mine does, well untill i throw in my halltech

[Not_An_Abba_Fan]

I have found that the VN on dedicated LPG lacks top end. It's good for up to around 2500rpm but after that the acceleration seems to drop off. It still accelerates but it feels like you only have half throttle. I have been looking for an LPG tune for a while now and no body will commit to doing one. I have been told that a tune for 98 ron will work but the spark advance is still too much at high revs. I need someone to experiment for me. I have a memcal, I just need it tuned so that the spark advances as normal until 2500rpm then remains constant after that.

[delcowizzid]

i could slap a couple of test tunes on a chip for you to test mate i have some big enough chips to put 4 tunes on at once and switch between if you wanted to have a play round

[Not_An_Abba_Fan]

That would be good mate.

[delcowizzid]

what tune you running now a factory gas tune

[centy]

i would be interested in testing out a few tunes to.
vp v6 ex cop car dual fuel.
goes like a scalded cat on petrol and sfa gas used when running that but low power.

[FXST01]

Delcowizzid,

Could i get the bin files emailed to me?

Cheers

[Not_An_Abba_Fan]

As far as I am aware it is still the factory petrol tune.

[DavoVP]

sounds to me like your running lean, Mines a manual vp, and it only starts droping off at 4.5 grand, ( cant tell the diff between gas and petty till then ) the reason for that is i only have a single stage mixer, which means set it rich down low and hope it doesnt get to lean up high. mind you though i only get 450-500 k's out of 72 useable liter's on gas.

When i didnt care for my gear box i coud bake 2nd with 245 / 45 17's on the rear on gas. twins aswell, ive since stuffed my diff, and broken one gear box lol.

Looking after the old girl now, ive had my fun with it, fixed her up and she just gets me from a to b now.

[greenfoam]

Weren't you supposed to send me one? anyway run it so at WOT there's about 28 degrees in at 2500 and then leave it at 28 all the way out, that will be fine for lpg

[FXST01]

So, any way back to my original question, what map/field needs changing?

Is it the F1 SAMAIN table?
The KMAXADV constant/scalar?
or some other one ?

[delcowizzid]

yip samain is the spark advance table.

[Not_An_Abba_Fan]

Weren't you supposed to send me one? anyway run it so at WOT there's about 28 degrees in at 2500 and then leave it at 28 all the way out, that will be fine for lpg

PM me your address and I will send you a memcal. How much?

[delcowizzid]

It is important to remember that the burning rate of LPG differs from that of petrol. At low RPM the burning rate is slower and more advance is needed. At high speeds the burning rate is faster, consequently less advance is needed.

When an engine is converted to run on LPG as a single fuel engine the ignition timing should be revised to give more ignition advance than the petrol engine at low speeds, and less than the petrol engine at higher speeds. This means that conventional distributors must have adjustments made to the mechanical advance mechanism to reduce the rate that advance increases with speed. Merely altering the static timing is not correct.

In the case of a dual fuel conversion the matter is complicated because the ignition timing needed for optimum performance on petrol will give too much advance at high speeds when LPG is used. The difference could be as much as 10 degrees.

An engine tuned for optimum performance on petrol and running on LPG will have too little advance at low RPM and too much at high RPM. It could therefore encounter detonation at higher RPM.
An engine tuned for optimum performance on petrol and running on LPG with the distributor advanced but not recalibrated with a different rate will have excessive advance at high RPM, and a higher probability of encountering detonation.
An engine tuned for optimum performance on LPG and running on petrol will have excessive advance at low RPM and therefore a possible detonation problem.
Incorrect ignition timing on any engine will lead to problems. Detonation is not always audible. The nature of the problems encountered will vary with the engine type, the octane rating of the fuel (petrol or LPG), engine speed, and in the case of LPG the installation and type of conversion and the source of the LPG.

Here is a list of some typical and some less common effects observed on dual fuel engines operating in Australia:
Piston land or crown erosion
Ring land breakage
Groove wear
Skirt scuffing (usually on the thrust side only) or breakage
Top ring scuffing or breakage or molybdenum flaking out
Spalling of the chromium on oil ring rails

Unfortunately it is not possible to optimise the ignition advance rates for petrol and LPG with the one setting on a distributor so a compromise setting will usually be obtained. From a performance point of view this may represent little problem since the engine is most likely to run on petrol only occasionally, i.e. when the gas tank is empty. Later engines with engine management systems and the more sophisticated LPG conversions can have the advance rate and initial spark timing settings optimised for both fuels

The best way to be sure that the ignition is optimised for both fuels is to install an ignition switching device, known also as "Dual Curves". These units are wired into the ignition system and switch automatically to the LPG or petrol setting when the fuel switch is activated. They will give more initial advance than the petrol setting when the engine is running on LPG, and as speed increases they will give less advance than the petrol setting. Although these are usually pre-calibrated for a range of applications (i.e. not necessarily calibrated for a particular engine) they will give a much better approximation to the ignition requirements for engines being converted than the incorrect practice of merely altering the static timing.

[levymetal]

i remember reading something once (on this forum) about someone who wanted to run dual eeproms and be able to switch on the fly. ****ed if i'm going to search for it, but i wonder how he ended up going with that. might be useful here

[Not_An_Abba_Fan]

I have the memcal out of the spare ECU ready to send.....