LPG and EGT's

[Jimbo]

I have been playing around with the LPG on my GQ trying to get the mixtures a little more stable (using a wideband).

LPG stoich is around 15.7:1 but the gq can cruise at 16.5 and higher no problem. Does anyone have data on what happens to the EGT's as you start to lean it off.

Also what should i be aiming for when accelerating? As i understand it LPG (already vaporised) has no cooling affect. Do the EGT's rise with a richer mixture too?

Cheers

[Northside 4x4]

I have been playing around with the LPG on my GQ trying to get the mixtures a little more stable (using a wideband).

LPG stoich is around 15.7:1 but the gq can cruise at 16.5 and higher no problem. Does anyone have data on what happens to the EGT's as you start to lean it off.

Also what should i be aiming for when accelerating? As i understand it LPG (already vaporised) has no cooling affect. Do the EGT's rise with a richer mixture too?

Cheers

That graph is a good tuning guide for ULP and gas.
The HP graph can be moved to the right by 1AFR point, the BSFC doesnt move very far though due to the energy per litre differences of the fuel.
15.5:1 is a good cruise ratio
13-13.5:1 under full load for best safety and power.

If you look at BSFC, it is the same between 15 and 16:1, BUT! the torque/hp drops the leaner you go.
This is especially noticeable with gas as it has alot less energy per Litre.

Basically just because your running it leaner, doesn't mean you will have better economy.

[Jimbo]

Thanks, I have it around 14.5 for light to mid acceleration and it seems fine. Not much tuning ability with this impco 200 mixer!

[Northside 4x4]

Thanks, I have it around 14.5 for light to mid acceleration and it seems fine. Not much tuning ability with this impco 200 mixer!

14.5 is ok, marginally rich but wont cause any problems.
You will notice an economy saving backing that off to mid 15's though.

[date]

A question about Air/Fuel ratios: Where did you get your A/F meter and how much?

[Jimbo]

I bought an AEM wideband off ebay for $185 delivered but that was when the aussie $$$ was a bit higher

http://www.ebay.com.au/itm/AEM-DIGITAL- ... 322wt_1037

One of the best things i have bought off ebay so far. Helped me solve a few issues with the patrol and save on a dyno tune or 2.

[date]

Jimbo:
This looks like a product which is premanently screwed into the exhaust pipe somewhere. How did you do it? I am actually after a portable device which I can use to check both my vehicles (both on gas) and also my friend's LPG toyotas. Do you know of any portable devices?

[Jimbo]

I have it installed in the factory O2 sensor (yes the ecu misses out on an o2 reading for now) in the extractors.

It only requires a 12v power supply. I think you could easily make it portable but unless you are running it on a dyno you don't want it to be just clamped to the exhaust while driving around and tuning.

I was just going to buy another wiring kit and have that installed permanently on both my cars as it is only a 2 min job to unscrew (and unplug) the sensor and then unplug the gauge.

If i were you i would just semi install it on each vehicle by running the wires through the window (firewall too a while in patrol), tuning the vehicle and then removing them. I was originally going to do that but i like monitoring my patrol under different conditions (towing and so on) and was very surprised how variable my LPG set up is. Very easy to run super lean or super rich without knowing. Eg when i first hooked mine up i was idling at under 10:1, cruising at 11:1 and then 16:1 while accelerating.

[Jimbo]

Also it comes with the bung that you can weld in your exhaust and then just put a bolt in it when your done.

Also have a look at this link

http://www.ebay.com.au/itm/PLX-DM-6-Mul ... 755wt_1270

This wasn't around when i bought mine. Looks pretty fancy and can have other sensors displayed on the same gauge and its cheap!!

[date]

Jimbo: One of the reasons I have not gone down this path is doubt about what the control systems are doing. The Gas computer takes the O2 reading from the standard sensor and uses it to determine where to set the stepper motor in the gas delivery line between the converter and the engine mixer. In my vehicles, the O2 sensor is downstream from the catalytic converter and I have been told that you get false readings because the Cat adjusts the exhaust mixture. I have been told that you need a 4 gas monitor to do the job properly ($4500+). Does your Nissan have the O2 sensor downstream from the Cat?

[Jimbo]

My o2 sensor is in the exhaust at the end of the extractors well b4 the cat. I have had it unplugged for ages as i'm running straight gas (for now until i solve some problems) and have unplugged the feedback loop as it wasn't working well.

What gas system do you use? Mine is an impco 200 with feedback but looking to change it to an impco 225 without feedback. There is a guy on ebay that sells them for $200 complete. I was quoted $170 just for the diaphragm for mine!!!!

[Northside 4x4]

There is .2 afr difference before and after a cat converter in most cases. After cat will read .2 richer than before.
Its important to remember that because the O2 reading has changed, doesnt mean the mixture actually changes.
Still X amount of air and fuel being burnt by the engine, but chemical changes take place that cause the readings to differ.

So if you take that into account you will be right. No need to spend big money on a gas analyser unless your testing for emission standards etc.. which is null and void because there are none for LPG.

How cat converters work
http://en.wikipedia.org/wiki/Catalytic_converter" onclick="window.open(this.href);return false;