Bri Bro

I am not sure if you run a catalytic converter, but if you do, you need to dither around 14.7 to allow the chemical reaction to occur in the cat.

ryanm6100

I get 20mpg driving mixed city/highway. Not very good, but how I drive, Ok.

Rogue_Ant

No. The AFRs can be leaner without issue. Otherwise all the thousands of chevy and fords with air-pumps (smog-pumps) would've had major problems passing emmisions.


-Rogue

RPHARRIS

Best mileage for me was achieved with around a 14.7 AFR and A LOT of part throttle advance. I don't remember the exact numbers, but they were very similar to my 05 Jetta 2.0 on my daily commute (a mix of highway, city, and twisty roads). Any richer than than 14.7 will begin to seriously compromise mileage, any leaner will (in my opinion) slightly dull the responsiveness because more acceleration enrichment is needed.

special tool

I would be interested in helping you with this goal.

Bri Bro

The cat for the old air pump systems (replaced in the early 80s when regulations changed) was a 2 way and only oxidized. Current cats are three way and reduce and oxidized emissions. That is why they need to dither around 14.7, one side (<14.7) they reduce, on the other (>14.7) they oxidize. The 944 uses a three way so it needs to dither to reduce NOx.

There were some 3 way cats made that had two parts, the front part reduced emissions, and the back part oxidized. The back part had an air pump connected to it. They were expensive and you don't see many of them around anymore.

zoltan944

Not that your hiding anything, just wondering the numbers for o2 readings for these same paramiters
idle
what you are at prior to 1psi
full throttle
etc...

I've spoken to a few others, just wondering your thoughts as a current E85 driver!

gregeast

Best I've seen is 28, with Vitesse chips & MAF. 'Course those of us living up here in the pristine mountain air have a bunch less atmosphere to push out of the way than you flatlanders

Rogue_Ant

Greg, my 31mpg was driving back and forth from Colorado Springs to Denver. I'm sure I could've gotten better in a 'lesser state' (flater)..


-Rogue

Rogue_Ant

Thanks for the info!

Still no issue running leaner then normal - except the emissions part...


-Rogue

333pg333

How much do you guys pay for E85 per gallon anyway? That's the way to go though you will have to upgrade a few things but once done, you can have your cake and eat it. You will have to use a bit more fuel however it's much cheaper than pump over here...or will be when they release it.

zoltan944

i think its 10-20% below regular in the southwest. I think it should be lower, just the stations tacking on more money.
Works out to $.80 or so a gallon from premium or less depending on station

Rogue_Ant

The great thing about E85 is that you can be pretty sloppy with AFRs.. Furthermore, E85 rich-best-torque is a very similar Lambda value to gasoline. This simplifies things, as I use a normal gasoline scaling on my WBO2, and I can utilize ratios that I'm familiar with instead of a direct Lambda value.

At idle I usually shoot for a little lean of stoich, mid 15s.

For anything less then 1psi (~100kpa), I lean it out. I've been playing around with the AFRs for lean-burn, but mid 16's is a good place to start. E85 will burn much leaner, but you really need to increase the ignition lead, to maintain any kind of power.

From 1psi to about 10psi it slopes from ~14.2 to ~12.5 or so. Pretty much anything above 10psi is upper 11's. You should be able to run low 12s under boost with E85 and be just fine. However I'm a little more aggressive then most with boost, so I don't mind the extra safety margin.


-Rogue

blown 944

I have been paying around 2.20 per gallon up until about a month ago and now it is up to 2.70. About a dollar less than the cheap grade and 1.20 less than 91 octane. I have no idea how much less than race fuel.

I agree completely with Rogue's tune. Even if I am tuning in a much more primitive manor the numbers presented are very similiar to what I like to run

MM951

st: i would love any help to reach my goal, thanks


re: e-85

Jeez.. there are only a couple of e-85 stations in NY, the nearest is 60 miles away from me.. but it's only $2.90/ga.

for me locally :
87 octane is @ 4.01 9/10
89 is @ 4.12
92 is @ 4.22!

So the savings would be $1.32/gallon. X23 gallons (irrc) = $30.36 per tank.
Say it would be ~4.3 gallons to go 120miles @ 28 mpg = $12.47 cost

That makes a savings $17.89/tank, even though I have to travel 120 miles round trip to get e-85.


I think I'm going to have both a 92 octane and e-85 tune..

blown_944/rouge ant, mind if I pick your brains about tuning w/ e-85?