Quote:
Originally Posted by Mkrusz
That's all great if your into spending money. Did you forget the burnt valve problem or was I just blowing smoke?
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Combustion temperature only gets excessive if you run lean. Under good stoichiometry, alcohol produces lower combustion temperatures and does not burn valves. This should be elementary to an ASE master mechanic.
Since ethanol brings quite a lot of its own oxygen to the party, it requires about a 10:1 air/fuel ratio compared to around 14:1 on gasoline. This would necessitate as much as a +40 fuel trim on a typical, unmodified fuel injection system and as any ASE master tech should know, +25 is about as far forward as a typical ECM will drive its injectors to compensate for altitude changes and typical wear-n-tear - not to mention the injectors themselves may not have additional duty cycle available in low(ish) pressure systems. On gen1 v6 Troopers it's easy, you just disassemble the TBI pod and drill out the fuel pressure regulator ball valve retainer, tap the housing for a screw, and screw down until you get the desired higher pressure. The ECM can trim + or - 25% roughly so assuming your o2 sensor is operating correctly you just fill up your empty tank with e85 and drive around, adjusting the fuel pressure up until the CEL no longer comes on. This turned out to be around +6psi and yes, it will probably reduce the life of the fuel pump but never did in the 70k+ miles I owned either of my Troopers.
My tempo has a piggyback ECU for its dual fuel CNG conversion and although I haven't had cause or desire to reverse engineer it - the car seems to work brilliantly on E85 and when I point a laser thermometer at the exhaust manifold, temperatures are the same on E85 as gasoline. The cat runs about 50-100F cooler though, or appears to, on E85 (i had to measure on different days so atmospheric conditions may skew results)
My 01 Blazer uses a gm vortec 4.3 engine and thanks to a sticky poppet I replaced the fuel injector assembly with GM's fix for the poppet problem, the factory injector assembly that came on 2004+ implementations of the 4.3 vortec. This replacement has an adjustable fuel pressure regulator in it as well, but getting to it requires an awful lot of disassembly so I didn't want to adjust it "by ear" - I got in touch with pcm4less and had them reprogram an ECU for me which decreases cycles between sensor polling (adjusts more rapidly to changing conditions/fuels) and has a few fuel map adjustments that were recommended to me after I described what I was doing. Thanks to this being an OBD2 vehicle I was able to use a scangauge to determine my existing fuel trim, which sat at + or - 3 on gasoline. I bench adjusted the fuel pressure regulator to 72psi (oem is 65) and since I already use an outboard Walbro 110psi fuel pump (half the price of replacing the in-tank assembly when it wore out) I shouldn't have any pump related issues.
I'm no master mechanic, just some dork who grew up on a farm but I have a decent understanding of the differences among these fuels, and how to work with them. It really is this easy, and my experiences exactly match what I expected: E85 has fewer btu's and is heavily oxygenated compared to gasoline, so you have to supply more of the fuel per combustion, but thanks to its higher octane and self-provided oxygen - AND the fact that you ARE injecting more fuel - it ultimately does provide a greater amount of power if for no other reason than because your air intake can't bring as much oxygen in through natural aspiration with gasoline.
Like I said, an ASE master mechanic should know this, I'm not formally educated and managed to get it.
