24 replies to this topic

[fourex]

Two of the major influences on the octane rating of lpg in your running engine (aside from the butane percentage) are 1. the speed of the incoming mixture to the combustion chamber and 2. the temperature of the gas/air mixture. Unlike petrol/air mix, lpg doesn't induce "charge cooling" by using a richer mixture (unless the gas is injected from a compressed state). Most of us don't run gas injection, so using the typical set up which we know is a converter, we get the gas changed from a solid to a gas and use hot water via the heater hoses to stop the converter from freezing up. The problem is that the converter heats the gas up somewhat, so the gas/air mixture is often hot to start with. This decreases the octane rating of the gas/air , so preignition is more likely. By using a restrictor in the coolant line going to the gas converter we can decrease the temperature of the gas exiting the converter on its way to the mixer/carby. If you go to far with this (too much restriction to water flow) then the converter will freeze up and leave you stranded with a car that wont go! If you get it right then the gas leaving the converter will be around ambient temp, or under full throttle/revs very cold. This will give your engine better volumetric efficiency, resulting in more power. The problem is the differing amounts of heat needed to keep the converter from freezing in the extremes of operation. At idle or slow driving the converter needs bugger all heat from the coolant , but at full throttle and high revs the converter needs a lot of hot water to stay warm. I used an automatic transmission cooler to largely overcome this freezing up problem, the water going to the converter first had to go through the cooler which was mounted in front of the cars radiator, so the faster I drove the cooler the gas temp from the converter. If I put my hand on the pipe from converter to mixer it would feel cold to touch, and tyhe engine went much better from around 100 k.m.h.

[matt_lamb_160]

You can buy electronic temperature controllers which monitor the gas temperature and control the amount of water that goes though your converter.

[fourex]

You can buy electronic temperature controllers which monitor the gas temperature and control the amount of water that goes though your converter.

Where do we buy them from Matt ?

[tribal]

I've always thought if you could control the coolant supply to the converters you could get better bang for your buck.

Be really interested to know more about the electronic temp controllers and how much you could tweak them for peak efficiency on LPG...

[ltd351t]

Cooling the vapour post-converter with a small water to air cooler?

Restricting water to converters isnt the best idea if the system is making decent power, none of the control systems respond fast enough, probably fine for setups that are not pushed very hard tho.

It would be good to slightly lower the converter water supply temp and use a system that stabilises it, IE that same cooler you have on the front, but have a thermostatic switch and fan, and mount the fan out of direct airflow.

Then you could regulate and lower the temp of the water entering the converter, and it would stay stable, and not be weather or speed dependant, the converter would also maintain its peak flow and duty cycle.

[matt_lamb_160]

Not sure where to buy the electronic controllers. The one I know of is an AutoTronic DualCurve #4036 Electronic Temperature Controller, but there are others. It is just a vacuum operated switch with a solenoid from the temperature sensor.

[xw351]

Cool post,

I also found that the B2 convertors had internal liquid gas passages that had reversion points designed to slow the flow of liquid to vapour, effectively holding the liquid up so as to reduce the change of state time from liquid to gas.

Simple mod was to die grind these reversion points off and open the passages up allowing faster transition through. Mind you I had one of the Ecotrans thermostat in the bottom hose conversions with the top hose bleed off to the thermostat in the bottom.

[S33YA]

how hard is it to grind don those passages?? im running a b2 atm

[fourex]

Not sure where to buy the electronic controllers. The one I know of is an AutoTronic DualCurve #4036 Electronic Temperature Controller, but there are others. It is just a vacuum operated switch with a solenoid from the temperature sensor.

I would have given my left testicle for one of these 10 years ago.....hang on...I think that I swapped that testical for something else........anyway, I googled and googled, it seems that autotronics are not easy to track down, has anyone found a complete converter temp contol system that doesn't require a p.h.d. to understand and fit?

[xw351]

how hard is it to grind don those passages?? im running a b2 atm

Well you would need to strip your convertor to begin with but unless your a gas fitter, then it's pretty hard to accomplish as the passages are all internal.

[Neeek]

has anyone found a complete converter temp contol system that doesn't require a p.h.d. to understand and fit?

http://www.altfuel.com/thermostats.htm

I've got one of these. Haven't fitted it yet, but if it does what it says on the tin....

[xw351]

Here are some pics of the mods,
This one is just about finished and the liquid starts in the centre and works its way to the left and then doubles back on itself.


The one on the left is original (note the reversion points where the material has an angled backcut) and the right is about half way through.


You could spend ages on these and even get some expoxy metal and smooth the outer radius on the final stages where it loops.

Edited by xw351, 02 June 2010 - 11:51 AM.
typo

[matt_lamb_160]

Did you do that for high rpm when you can't get enough water through the converter.

[fourex]

http://www.altfuel.com/thermostats.htm

I've got one of these. Haven't fitted it yet, but if it does what it says on the tin....

Great stuff Neeek, I have already fired off an email , I want to order the smaller 3/8 unit, I would prefer to run the converter as cool as possible. which one did you choose?

[Neeek]

Great stuff Neeek, I have already fired off an email , I want to order the smaller 3/8 unit, I would prefer to run the converter as cool as possible. which one did you choose?

I've got the M456 one. I bought it because I found that this mob had a couple of OHG X-450 to Holley baseplate adapters. Only 2, mind... and I bought both of 'em! Figured I'd get the 'stat as well while I was there.

I've been having some driveability issues of late, and I'm no closer to figuring out what's wrong. I know that I'm running very lean, so I'm hoping that by installing this 'stat my convertor will run cooler, the LPG will be richer and I can finally stop spluttering and backfiring out the pipes under load... I'll try and fit it up this weekend and see if the "seat-of-the-pants'o'meter" detects any change...

[xw351]

Did you do that for high rpm when you can't get enough water through the converter.

I wanted to keep the gas temperature lower which would reduce the expansion of the gas when it went through the conversion stage, so as not to consume available space for air in the manifold, I had plently of water flow and never came close to freezing the convertor. By opening up the passages, the liquid to gas phase change was reduced which meant that it was cooler and richer which I what I was chasing.

[fourex]

I've got the M456 one. I bought it because I found that this mob had a couple of OHG X-450 to Holley baseplate adapters. Only 2, mind... and I bought both of 'em! Figured I'd get the 'stat as well while I was there.

I've been having some driveability issues of late, and I'm no closer to figuring out what's wrong. I know that I'm running very lean, so I'm hoping that by installing this 'stat my convertor will run cooler, the LPG will be richer and I can finally stop spluttering and backfiring out the pipes under load... I'll try and fit it up this weekend and see if the "seat-of-the-pants'o'meter" detects any change...

I converted my brothers kingswood (remember them) to lpg back when you were allowed to do it yourself , bought everything second hand including a converter designed for a four cylinder car, and set up the carbie with a spud in the side. The problem was that the converter could not supply enough gas to get the car (202 red) to go over 100 km/h, and boy was it slow getting there!! Economy was great though!! You can run gas reaaaaaalllly lean and not get misfire (and the kingsy had points in the distributor!!) If I were you I would be checking the ignition system, from the rotor button, right through to the plugs. I often found that commonly available sparkplug leads (read cheap) only last 12 months or so with gas, and the next place to look when misfire/popping occured was for the build up of white flaky crap on the dissy cap terminals, inside and out. Actually I've found the standard xf electronic ignition to be quite good, when changing plugs some of the ones that I pulled out had a gap of 1.5 m.m., and they were still getting the job done!

[Neeek]

It may be ignition, but I hope not - have spent a small fortune on the ignition side of things and there's nothing much cheap about it..!

[matt_lamb_160]

Where do we buy them from Matt ?

http://autoparts.ras...products_id=178

[bob 351]

http://autoparts.ras...products_id=178

ha ha 2 years later