^^^ I'd say your V/E is approaching 50% ^^^

"As you know an engine is nothing more than a big air pump"


So are people!!!!!!!!!!!!!!!!

there's a few companies that make the direct liquid injection systems, I guess they figured a way to resolve the pressure issue. maybe they regulate it down to a low pressure in a 2 stage regulator and spray it at a lower pressure that can always be delivered.

overall high compression and lpg are good. however you get there.

Turbos and LPG work very well together my previous car pic is below:




Yes I know it's a gemini but it was straight LPG and was about 7.5:1 comp ( yes a little low for some) but due to the slower burn rate of LPG you don't hurt pistons as easily, so this car had cast pistons O'ringed block standard head modified EFI manifold to fit the 350 CFM GRA Gas carbi and a low comp 1.6 litre, it had a modified dissy no vacum adv just mechanical and softer springs so it would advance earlier and a gas camshaft. It used to pump out about 200 RWHP and got it's best economy at about 120 km's with light throttle and the turbo just spooled up at about 3000 rpm. it would do about 400 kms on 50 litres on LPG. (65 litre tank)

just more info for you. this car was built for a daily round trip of 110 kms for commuting to work. all country driving ;)

direct liquid injection has been trialed by a few companies here but they have never released a product because the metering is so difficult due to the presure differences between a full tank and an empty tank.

Cheers

Engine Combustion Theory / Alternative fuels reading

here's some reading for interested people. ( talks about lots of combustion theory, useful no matter what fuel you use )

I'm dreaming of a nice blowthrough non intercooled setup, it's not going to make a 'beast' but I don't think you'll be getting in front of me getting on the highway.

it's on that fj20 rallycar. yeah water injection would work, way cheaper than all that intercooler piping, would make it more responsive and lighter and less complicated.

I suppose a propane injector that fogged in liquid lpg would cool things down nicely and richen the mixture a little. lpg expands 270 times when it reaches room temp and pressure. Maybe spray a very tiny bit of n2o ;)

I seen a bit around about water injection to control intake air temperature - and it working as well as an intercooler.

It's on a B310 race car....trying to remember who's race car. (It's a member of this forum) the while Sunny.

I'm kind of dreading a suck through turbo. At least i probably don't need the special seals, but I'd been hoping to use an intercooler, so that won't work in a suck through.

Is the improved mixing worth not having an intercooler?

what if there are 2 turbos, 1 to pressurize the intercooler and another to mix up the air and feed the engine? Or is that way more complicated than it needs to be.

Lpg really blends well, so maybe that's overkill.

just want to boost the CR up to about 12:1 to take advantage of the higher octane.

is the accelerator pump why petrol carbs seem less efficent? LPG mixers don't spray extra fuel when you mash on the throttle.

Fuel economy is totally dependent on mixture quality. Good quality A/F mix and good economy.

The AF ratio (except in EFI systems) is controlled by the amount of vacuumn caused by the velocity of air through the mixing device (Gas Mixer or carb). Ideally the AF ratio is constant. In reality it varies with air velocity (throttle opening) through the mixing device and engine speed. It is not only air fuel ratio that has an effect on economy but the quality of the air/fuel mixture (fuel particle size and the degree of uniformity through the mixture). Finer particles, (evenly distributed so each molecule has easy acces to oxygen for combustion) maximises the amount of heat per burn cycle.

At high engine vacuumn you have high air velocity through the mixing device. This gives better fuel quality through better mixing (emulsification).

Assuming an ideal spark condition, by finding the throttle/engine speed combination where the AF ratio is at the ideal mixture with best emulsification, you will achieve the best power/economy compromise.

Suck through turbo's on LPG get very good mixture quality due to the gas passing through the compressor turbine and so can give very good results even on low boost levels.

Blow through systems mixture quality is no better than N/A carbs or mixers but is able to force more mixture into the cylinder.

The vacuumn gauge will give you an idea of velocity through the mixer.

I've been thinking about the whole system.

I used to have a vacuum gauge that i watched while driving it made fuel economy interesting.

If i calculated the frontal area i could figure wind resistance and could find terminal velocity, and then how fast it should go at a given HP number.

There's a trade off of speed/air resistance and fuel usage.

theoretically if i went 55 in 5th gear and kept the throttle as closed as possible that would be nearly the best mpg possible.

it's kind of a fun thought exercise.