My ML350 2003

[teoman]

So i have this car that i was going to sell for a diesel which can be modified a bit better but it appears i may be stuck with it.

It already has LPG and currently my fuel cost is comparable to a modern gasoline car so it is not too bad to own.

What mods do you recommend doing on it to make it more economical?

Will water injection play nice with LPG?

I also plan on deleting the mirrors which are slightly broken at the moment.
I also plan on putting full grill blocks. I can spray the radiator with water to reduce the need for the fan as it can suck quite a bit of energy when it is activated.

Hot air intake, would that have any negative effect on using it with LPG?

What else can you guys think of? I know it is not the most economical to begin with.

This is what it looks like:

[Daox]

What is your typical commute / driving like? City or highway?

[teoman]

Typical commute is mostly city with traffic ( i live in Istanbul with 20 million other people who clog up the highways). I know in traffic nothing much can be done for fuel economy besides getting a smaller car. But i do frequently go on longer trips. For daily commute i try to use my motorbike as much as possible.

[mcrews]

welcome!
you could increase the psi in the tires to 40+. that would help on the trips.
I have a KIA Sportage and it adds a couple of MPG when I take trips.

[cRiPpLe_rOoStEr]

Originally Posted by teoman

Will water injection play nice with LPG?

LPG is already quite cold, at least when it's aspirated in a liquid phase. IIRC most of the LPG conversions require the vehicle to start on gasoline and then switch to LPG when there is enough heat in the coolant to exchange with the LPG at the vaporizer.

I can spray the radiator with water to reduce the need for the fan as it can suck quite a bit of energy when it is activated.

Are you sure a water spraying would be so much less energy-intensive than a regular electric fan? There is also the weight of a water tank, pump and nozzles. Even though it's already used in a handful of high-performance applications such as hill-climbing vehicles that run at Pikes Peak, I'm not sure if it would be a good idea into a regular road-going vehicle.

Hot air intake, would that have any negative effect on using it with LPG?

A warm air intake is unlikely to have negative effects with LPG. BTW some earlier dedicated-ethanol vehicles in my country had an adjustable air intake which allowed a more precise temperature trimming from a colder intake to use in summer to a warmer one more suitable to use during winter in order to prevent carburettor icing. Pretty much the same feature is still used in small piston-powered aircraft.

[teoman]

It is injected in gas form, it does have an heat exchanger-vaporizer to boil the LPG.

I would have thought that direct injecting it would be beneficial for performance as it also cools the intake charge and should be easily controllable. Not sure why they prefer gas injection.

[Daschicken]

Originally Posted by teoman

I know in traffic nothing much can be done for fuel economy besides getting a smaller car. But i do frequently go on longer trips. For daily commute i try to use my motorbike as much as possible.

If it helps at all, the gasoline version of your car is EPA rated for 14 mpg city, 17 mpg highway.

Actually, in traffic and city driving is where you can get the most significant improvement in fuel economy. Look ahead as far as you can to anticipate traffic conditions ahead, try to look through windows or around the car in front of you. You know, the usual stuff. Check out the 100+ hypermiling tips at the top of the page and see what techniques you can use.

Remove any unnecessary weight, like unused seats, or misc junk. I don't risk removing my spare, but I also don't have an inflater/plug kit to patch a tire. Only you can decide what you are comfortable with. Pump the tires up more, try to maintain the correct pressure bias if there is one. For example, my accord specifies 32 PSI front, 29 PSI rear, so I set it to 51 front, and 47 rear.

Regarding your water spraying idea, that is actually a really cool idea. Make sure you monitor your engine temperature with those grill blocks, the idiot gauge is not a suitable replacement.

I had an idea for what you could do to optimize the water sprayer. Place a large water tank in the front of the car and connect a thin rubber hose above the grill block opening. You could either drill really small holes all around the hose, or you could use drip irrigation hoses. Also, install a closeable valve before the hose so you can turn the water supply on before a trip, and off when you are done. With this setup, you wouldn't need a pump and the associated electrical draw.


If you are going to do this, consider using distilled water in the water supply, less chance of things rusting.

Another idea I just had: Position the tank at about the same level, or lower than the supply hose. Have the end of the hose open and hanging in the wind. As you increase speed, the air flowing by may suck the water up the tube, supplying more water at higher speeds. I made a diagram of what I am explaining.

[teoman]

I already try to do that as much as possible. But it is bumper to bumper mostly.

I will pump up the tires to the sidewall pressures. I was already running 45psi.

[cRiPpLe_rOoStEr]

Originally Posted by teoman

I would have thought that direct injecting it would be beneficial for performance as it also cools the intake charge and should be easily controllable. Not sure why they prefer gas injection.

Direct injection doesn't really cool the intake charge, since it doesn't vaporize at the intake manifold and is injected directly to the combustion chamber at the liquid phase instead. But if LPG was fed in the liquid phase through a regular port-injection it would freeze the intake manifold. Some older Fiat engines and dedicated-ethanol ones from other manufacturers featured a heated intake manifold which had some ducts where the engine coolant would pass in order to avoid the risk of freezing due to a similar effect while running on ethanol. Anyway, LPG is not road-legal in my country, allowed only for special machinery such as forklifts and some tractors, but most of the illegal conversions that I have already seen were based either on dedicated-ethanol or Fiat engines exactly due to the intake heating provisions.

[teoman]

My lpg is manifold injected not port injected.

I suppose this is good for economy.