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Liam 04-04-2009 08:16 AM

Newbie Lean Burn question
Hi all

I have been looking at your great forum for a while. Some great work going on here! Time to ask a question. (Excuse me if i show a little ignorance here)

I am currently enjoying the savings from running my diesel Merc on a WVO blend, and was thinking about ways to save on the petrol car I have.
I guess my question is about Lean burn, timing changes and water injection. I have done a fair bit of searching and read a lot of theory on the subject, but i don't seem to be able to find much an anyone who has actually done it.

Are there any decent fuel savings to be had by leaning the mixture?
Is a timing adjustment beneficial? Or is it one or the other?
Will water injection help the heat, pinging, and emission issues involved with these adjustments?
The vehicle i have in mind for this is a 1990 AE85 toyota corolla AWD wagon
(Possibly known as a All-trac in the US) It is running a 1.6L fuel injected 4afe engine.

Sorry for the long post. Any help appreciated.

theunchosen 04-04-2009 08:45 AM

Hi Liam and welcome,

I'm GLAD YOU ASKED! Its called GDI, Gasoline Direct Injection. Its touted as really high-tech stuff. . .but its been around for over a hundred years and diesels already do it.

With GDI you can have both. You can advance timing substantially because the liquid fuel flashes to a gas when it is injected in the high pressure/temp cylinder. This consumes enormous amounts of BTUs strictly in the form of heat. So it dramatically cools the charge allowing the compression to continue again once the fuel is injected. Normal II Indirect Injection has to stop at 14 degrees below TDC otherwise the fuel can knock, preignite and really terrible combinations of the two.

Ford touts its DIE ecoboost is 30% more gas worthy than normal. If thats true then seeing normal sedans get clear of 50 mpg will be standard and the advantages of diesel over gas will lose alot of leverage.

The advantage to the system is to make sure the fuel injection is controlled almost strictly by your foot on the gas pedal and has nothing to do with the throttle body. Then you rip the throttle out and run Wide Open Throttle all the time and get learn burn and substantially better FE below ~4500 RPM.

You probably know but for anyone who doesn't its like you get to burn as much oxygen(it burns aggressively on its own, cylinder pressure and temperature are almost high enough to ignite it on its own) as you would at WOT, but you're only putting in 1500 rpm's worth. 3x more air to burn(which is pretty free excluding pumping losses) fuel now burns much more aggressively as well. alot more power than you would get out of normal cycle at 1500 rpm, but not as much as you would at 4500. It comes out as getting about 20% more power of free air. . .or 20% less fuel however you wanna look at it.

Making it. . .Drill a plug for a spark plug in a diesel engine and get an ECU you can program and rip your throttle body off. As long as your state does not have laws against custom builds and emissions you should be good to go. GDI has very low emissions to start with especially if the fuel air ratio is above 30:1, so you shouldn't be terribly worried about that. 3-way cats are ineffective against its emissions because its much more like a diesel's exhaust (NOx) than gas(Hydrocarbons).

theunchosen 04-04-2009 08:51 AM

The construction part I am actually not so sure on, but thats the fastest way I've come up with to get something like it.

The other option is to buy one. Lots of cars are switching out the powerplants for GDI and I think the current cheapest vehicle with them is the Chevy Cobalt SS. If you wait long enough GM might go under and then you could buy the remaining replacement engines for cheap. As long as no one steps in and stops that. . .

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