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Old 02-19-2008, 11:42 PM   #1376
union7
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Random E85 economy data:

Not a SUBE, but a SAAB 900 16v, but it has a slightly larger turbo and the Normaly aspirated compression ratio pistons.

anyway maybe this data will help someone

I spent some time on the dyno today, I did not do any power tuning, I was doing an experiment to find the best AFR for economy with timing optimized for that AFR. (ALL AFR's noted here will be on the gasoline scale even though i was using E85, which at this time of the year here is supposedly E70). (Colorado Springs)

I logged my rpm and load at about cruising speed on the highway at 3000 rpm fith gear , so that i could go to the dyno and then get an idea of my HP required at cruising speed.

I went to the dyno and loaded the car to my cruise conditions, and noted the tractive effort (say 30 lbs). This number represents the "power" that my car needs to maintain cruise at 3000 rpm 5th gear on the highway.

I then loaded the car at this point at different AFR's and then experimented with the timing with fixed AFR until i found the timing that used the lowest msec of fuel while still making 30 lbs.

I repeated this for different AFRs.

The results: (only listing the least efficient tested to and the most efficient)

3000 rpm, 30 lbs tractive

manifold kpa=about 55 for all

AFR 15,best advance=28,msec required=2.27


AFR 16.8,best advance=40 ,msec=2.07

i experimented past 17:1 and between 15 to 16.8, but 16.8 was the best
timing seemed very critical 1 degree either way lost 3 lbs or so tractive force.
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Old 02-20-2008, 06:17 AM   #1377
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Very interesting data thanks!

Larry
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Old 02-20-2008, 11:38 PM   #1378
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Sweet! 17:1 huh? The leanest I've heard on gas was about 18:1 but that was with detonation on iron heads. Did you notice any detonation at all when you put more load on it while lean?

I suspected for a while that lean on E85 wouldn't detonate like gas and shouldn't run hotter with the right timing. But, I never had the dyno time or adjustable computer of my own to futz with. What is your static compression ratio? That may be why you were able to run it so lean.
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Old 02-24-2008, 08:33 PM   #1379
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Super lean mixtures on alcohol fuels can melt down an engine just like gasoline so be careful. You only get cooler combustion temps at typical rich power mixtures.

Larry
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Old 02-24-2008, 10:12 PM   #1380
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Larry, I think he's onto something. Remember how it only takes 35-50hp to make a car cruise or accelerate under normal driving. How lean could we potentially go at cruise considering that and not melt anything?
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Old 02-25-2008, 01:42 AM   #1381
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Really lean mixtures help fuel economy right up to the point you start burning valves or melting holes in piston crowns. It really depends on the car. Most ECU's are designed to go to a fuel air mixture that is cat converter friendly (stoich), you really have to fight the car's ECU to go leaner than that in the OBDII cars so it is not much of an option for most of us. Although I understand the Open ECU and some of the high end setups will let you change that target AFR, you could end up killing the cat or pushing your nitrous oxide emissions up enough that you can't get a pass on emissions testing even though you are getting great fuel economy.

On gasoline max fuel economy happens around 15:1 - 16:1 if I recall correctly and lean burn limits are near 18:1. Maximum combustion temps are just lean of stoich. If the mixture gets lean enough it cools off due to the dilution by air flow. You also need to look at engine efficiency, since your ignition advance requirements change with mixture if you do not tweak the ignition timing to accommodate the burn speed of the leaner mixture you could actually increase fuel consumption on leaner mixtures if your timing is too far off. Proper timing can make a big difference at those low power levels and lean mixtures, one degree of timing error could drop engine efficiency enough to totally cancel out the leaner mixture.

As mentioned above, the only way to really do it, is to get the car on a dyno and tune for minimum air flow (or fuel flow) at the tractive effort/rpm you use at highway cruise. Its a long slow process and can only be done on dyno's that allow you to hold a steady load.

Larry
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Old 03-01-2008, 08:06 PM   #1382
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Subscribed
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Old 03-02-2008, 03:07 PM   #1383
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Subaru Stars Help

will My 91 2.2 subaru legacy run this stuff being all stock ?
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Old 03-02-2008, 06:50 PM   #1384
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Quote:
will My 91 2.2 subaru legacy run this stuff being all stock ?
Read the first 3 pages or so of the thread --- short answer yes, at minimum 30% possibly more with modifications.

Larry
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Old 03-04-2008, 11:59 AM   #1385
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Quote:
Originally Posted by HamFist View Post
Larry, I think he's onto something. Remember how it only takes 35-50hp to make a car cruise or accelerate under normal driving. How lean could we potentially go at cruise considering that and not melt anything?
I can get mine to cruise at 18:1 or leaner with no problems. My AEM wideband will only show 18:1 then it goes -- off the scale. I also have an EGT gauge and I don't think it gets over 800F at criuse. If the car is not warmed up, it will misfire a lot trying to run that lean though. As far as gasoline goes I can't get it to run leaner that 16.6:1 without misfireing.

Edit 4-17-08:
My cruise EGT's are actually about 1200F. I don't know why I thought they were 800. My EGT sensor is in the factory primary 02 location.

Last edited by salt; 04-17-2008 at 04:49 PM.
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Old 03-04-2008, 12:16 PM   #1386
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Where are you taking your EGT readings? My car is currently cruising at ~18:1 because of a malfunctioning front O2 sensor, and my EGTs are around 1200F at cruise. (Taken from the casting button on the driver's side collector.)
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Old 03-09-2008, 12:26 PM   #1387
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well i'll let everyone know how my 07 2.5i runs on 30% E85

thanks larry!
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Old 03-10-2008, 11:34 AM   #1388
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ok, so last night i filled up with 30% (4gal.) of E85 & unleaded (85oct.) gas. i did notice an improvement to power/low end torque when i got on it. how ever tho, the car runs hotter then normal when driving on the hiway & geting on it. (but at idle/cruising the water temp goes back to normal) no CEL's for running 30% e85 on stock ecu & injectors.

what will cure the water temp spikes?



the curent mods i have done is, header, cai, no cats.
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Old 03-10-2008, 01:02 PM   #1389
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Quote:
Originally Posted by salt View Post
I can get mine to cruise at 18:1 or leaner with no problems. My AEM wideband will only show 18:1 then it goes -- off the scale. I also have an EGT gauge and I don't think it gets over 800F at criuse. If the car is not warmed up, it will misfire a lot trying to run that lean though. As far as gasoline goes I can't get it to run leaner that 16.6:1 without misfireing.
800 at cruise? stock a wrx is around 1200-1300 at the casting bung. I'm at 1500 or so most of the time. 800 at cruise is too low, you are washing down the cylinders at that temp.
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Old 03-10-2008, 04:25 PM   #1390
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sounds like he may have meant 800C. <shrug>
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Old 03-11-2008, 01:48 PM   #1391
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Quote:
Originally Posted by rkramer View Post
800 at cruise? stock a wrx is around 1200-1300 at the casting bung. I'm at 1500 or so most of the time. 800 at cruise is too low, you are washing down the cylinders at that temp.

He is doing lean cruise. As you lean out past stoich EGTs go down.
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Old 03-11-2008, 01:55 PM   #1392
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Answer: 800 C = 1472 F
***********
maybee?
***********
***********
***********
***********
***********
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Old 03-12-2008, 02:41 AM   #1393
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here is some more info.



the water temp spikes stopped. i'm thinking the ECU freaked out. the next day, the water temp guage was function normal. not a single CEL untill today! i hit 1/4 tank and my CEL came on, thank god i have a ob2 scanner, so i scanned it, "system too lean (bank 1)", now remember i'm not running a cat. so i reset the code, continue driving another 30 miles, no cel. so i don't know if the E85/85oct mixture set the CEL off or it was due to me running catless (i've been running catless for the past 3months with no CEL's).





i ended up getting 325 miles to a tank of gas while running 30% E85/70% 85oct, which is about what i average when i run 91oct. [90% of this was hiway miles]
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Old 03-12-2008, 09:32 AM   #1394
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Quote:
Originally Posted by SubeN'Siren View Post
Answer: 800 C = 1472 F
***********

DOHHHH!!! that sounds very likely.
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Old 03-12-2008, 12:42 PM   #1395
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30% will likely be your limit on those stock injectors, especially with airflow mods. Try an o2 sensor bung extension for the rear o2 sensor. I've heard they help, but I put down 160whp through a cat and never got a CEL.
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Old 03-12-2008, 04:26 PM   #1396
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Quote:
Originally Posted by Vizzionz View Post
here is some more info.



the water temp spikes stopped. i'm thinking the ECU freaked out. the next day, the water temp guage was function normal. not a single CEL untill today! i hit 1/4 tank and my CEL came on, thank god i have a ob2 scanner, so i scanned it, "system too lean (bank 1)", now remember i'm not running a cat. so i reset the code, continue driving another 30 miles, no cel. so i don't know if the E85/85oct mixture set the CEL off or it was due to me running catless (i've been running catless for the past 3months with no CEL's).





i ended up getting 325 miles to a tank of gas while running 30% E85/70% 85oct, which is about what i average when i run 91oct. [90% of this was hiway miles]
bank 1 which sensor? If its sensor 2 then you should be good with the spark plug defouler mod
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Old 03-12-2008, 06:18 PM   #1397
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How about shutting the Cat efficiency cel off? That way you can use the too lean cel to "set" your mixture.
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Old 03-12-2008, 10:12 PM   #1398
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Quote:
Originally Posted by TheMadScientist View Post
How about shutting the Cat efficiency cel off? That way you can use the too lean cel to "set" your mixture.

i'm waiting for the defs for the 07 2.5i A/Ts to be released so i can turn it off!

well, i had to fill up last night again, so this time, i put in 2.25gal of E85 & 7.25gal of 91oct, no CEL's of any kind, no water temp spikes. nothing. i'm guessing the ecu freaked out the first time it seen the e85 mixture.


i'm looking into getting some WRX injectors so i can increase the e85 mixture and go on a dyno and see what it's putting down (i'll even do a base line with straight 91oct)
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Old 03-16-2008, 11:01 AM   #1399
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Ethanol will be coming to the North East in 2010.

http://pittsburgh.bizjournals.com/pi...21/daily7.html

I've been reading this thread with envy. Looks like I'll finally get some alky goodness!
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Old 03-18-2008, 02:46 AM   #1400
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yeah stupid va
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