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Old 04-24-2021, 06:14 AM   #2 (permalink)
serialk11r
Master EcoModder
 
Join Date: Jan 2012
Location: United States
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spyder2 - '00 Toyota MR2 Spyder
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Is running E85 actually cheaper than gasoline in your case? In the US, if you're not in a ethanol producing area, E85 is not much cheaper than gasoline. Definitely cheaper than 100 octane or xylene/toluene though

As you said, standard spark ignition engines seem to be able to run at around 1.4 lambda with the right adjustments as you said. Using a small amount of hot EGR essentially heats up the air, while the excess air is akin to cooled EGR with better combustion characteristics (you can read papers about mixing hot and cold EGR). Another thing which may or may not be suitable for your car is to run hotter coolant temperatures, as your car has port injection so it'll directly raise the temperature of the fuel disproportionately. I heard horror stories about BMWs of that vintage blowing head gaskets and radiators so I don't know if this is actually a good idea.

If you're raising compression ratio by welding material, I would go a little lower because you probably are interfering with the flow and cooling characteristics, maybe like 13:1.

There are a few ways to run even leaner (like >2 lambda) which you can't really do on your own:
1. Stratified charge direct injection (I believe some Audis used this in Europe for a while, presumably when emissions regulations were more relaxed)
2. Higher energy ignition methods, e.g. laser or prechamber jet or "plasma", these can get you past 2.5 lambda, pretty crazy.

Finally, I think you likely have some significant gains to be found elsewhere, like taller rear tires, underdrive pulley for power steering, thinner fluids, drag reduction, etc.

Last edited by serialk11r; 04-24-2021 at 06:21 AM..
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