How lean can you go!

[JayRolla]

Hey just wondering how lean you guys have been taking the e85. I usually run 11.3-11.5 but a lot of guys making serous power are running anywhere from 11.5-12.3. I leaned it out one day to around 11.8 and the car made a little funny smell so I richened it back up.

[thiazole]

11.5 to 12.0 is a pretty good area. You could go to 12.5, but I'd probably run a little less timing in that case.

[JackM]

I ran 12.5 without issue for a long time, but you are getting very close to burning up valves and hitting knock with that kind of AFR. Once I started turning up the power more I found that it left no room for error. It's just too close to hurting stuff so backing it down to 12.0 is good enough IMO.

Jack

[DSMtuned]

Keep in mind that the stoichometric air/fuel ratio is different for different fuels, so you have to change your way of thinking a bit when running E-85 and looking at the WBO2.


This is from the PLX website: http://www.plxdevices.com/InstallationInstructions/M-200_250_300UsersGuide.pdf

-Craig



Compatibility with Other Fuels
The above graphs assume that the device will be used with gasoline (14.7). The M-Series controllers are also compatible with the following fuels.
a. Diesel 14.6
b. Methanol 6.4
c. Ethanol 9.0
d. LPG 15.5
e. CNG 17.2
To find the new relationship of AFR to output voltage, simply multiply the lambda value by the specific fuel’s stoichiometric air/fuel ratio.
Example: If your engine uses methanol instead of gasoline. The conversion will be as follows.
1) Divide the AFR value by 14.7 (gasoline) to obtain a lambda value
2) Multiply the lambda value by 6.4 (methanol)
If your engine is running methanol and the M-300/M-200 display readout shows 13.00. Your actual air/fuel ratio is 13.0/14.7*6.4 = 5.66AFR

[JayRolla]

Ok thanks guys. So I should be safe to run 11.8-12.0 without worrying about killing my motor?

[DSMtuned]

I say lean it out until it knocks and then add a bit more fuel to give yourself a safety zone.

-Craig

[sbiggi]

I say lean it out until it knocks and then add a bit more fuel to give yourself a safety zone.

-Craig

That wont work well with e85. With that high of octane you will get negative returns before it knocks, ie loss of power.

If you want to be exact, get the car on a dyno and tune it there. Then you can see when you went to far when the power starts to drop off.

[DSMtuned]

That wont work well with e85. With that high of octane you will get negative returns before it knocks, ie loss of power.

If you want to be exact, get the car on a dyno and tune it there. Then you can see when you went to far when the power starts to drop off.

Wow, really? I super need to try it out!!

[dsm_gsx97]

I always say an EGT is nice here too. E85 doesn't knock much if ever so its likely you'd do damage before you'd see knock.

The general consensus of the pay to hire tuners tuning on E85 is mid 11s to mid 12s is good and safe. Most of them say there is minimal gains leaning it out from mid 11s to mid 12s so the lower is better as the richer mix gives you cooling benefits, however they also say when you get lean enough the cars come alive and get ridiculous. Of course at that point you are pushing how lean it is and would want a dyno and EGT and other things to be certain your doing a good job and all the guys I got this info have dynos in their shops. So since I don't have a dyno I tune my E85 customers to 11.5 just like pump gas and if they want it leaner I do it, but with a stern warning but I only will lean it out to mid 12s. I'm not into buying engines. :)

[BlueVelocity]

however they also say when you tune to low xxxx the cars come alive and get ridiculous. :)


That's classified information mister. :)

Knock? Where? On our last dyno session we never saw a reading over .55 volts. EGTS never creeped above 1480 and max AIT was 133*. AFR was, crackle-crackle, you're breaking up, I can't hear you.. :D

612hp at 24psi

[TerryLiv]

That's classified information mister. :)

Knock? Where? On our last dyno session we never saw a reading over .55 volts. EGTS never creeped above 1480 and max AIT was 133*. AFR was, crackle-crackle, you're breaking up, I can't hear you.. :D

612hp at 24psi

Erron,

I don't have a wide band so am asking. At .55V are we talking about 10.8:1, or am I off track?

Thanks,

Terry

[BlueVelocity]

Terry, the .55v is the raw voltage reading from the knock sensor. :)

[thiazole]

Yeah, my EGT gauge never did get very hot on E85 - certainly not like it did on gasoline. I think as you lean it, you increase cylinder pressure quite a bit. A leaner a/f mixture burns faster and therefore it is almost equivalent to advancing the ignition timing. That is why I say you should be careful not to go overboard with both timing and a/f. Every now and then you'll see someone on one of the bigger forums post engine carnage (like blowing a hole in the cylinder) on E85 where they were running super lean and with 24* advance, yet they never saw knock.

[matthewdesigns]

I was unknowingly running as lean as 16.x:1 on e85 when I first started using it due to an error in my eprom chip. Before I bought one, I borrowed a wb to see what was actually happening with the new setup and nearly crapped myself when I saw that. I registered zero knock at that lean a condition, so tuning for knock on e85 is not a good idea, as you'll probably never see any.

[JayRolla]

I say lean it out until it knocks and then add a bit more fuel to give yourself a safety zone.

-Craig

Scarry. This is why people burn valves on e85 without a WBo2.

[Gimpin]

Remember when pushing the limits of leaness that any wide band reads the average of all 4 cyl .... so if you have one injector that flows a little more and one that flows a little less you could be running a little lean in that one cyl

[JayRolla]

Remember when pushing the limits of leaness that any wide band reads the average of all 4 cyl .... so if you have one injector that flows a little more and one that flows a little less you could be running a little lean in that one cyl

Very very true! I think I will tune 11.5-11.8 and call it a day.

[JackM]

Yeah, my EGT gauge never did get very hot on E85 - certainly not like it did on gasoline. I think as you lean it, you increase cylinder pressure quite a bit. A leaner a/f mixture burns faster and therefore it is almost equivalent to advancing the ignition timing. That is why I say you should be careful not to go overboard with both timing and a/f. Every now and then you'll see someone on one of the bigger forums post engine carnage (like blowing a hole in the cylinder) on E85 where they were running super lean and with 24* advance, yet they never saw knock.

Yep, there are real issues with tuners today on E85. They are all trying to tune for higher power than the other and running timing way too advanced. E85 won't tell you anything is wrong until it's too late. If you have to go over 21 on timing to make power you are doing something wrong and putting the engine at risk, IMO. Lean AFRs will look like more power, but you will also do damage. Had one guy tell me brother (while he was tuning a customers car on the dyno) that AFRs are irrelevant and you tune for power only. My brother told him he was an idiot and a pissing contest ensued. The customer believed my brother and had him tune it his way. The result was a 30R turbo that did 598 to the wheels. 100hp more than everyone else keeps fighting each other to achieve. 500hp is supposed to be the goal on a 30R :rolleyes:

Here is a head that went way too lean. If you don't know how an engine works, you have no business tuning it IMO. There seem to be a lot of tuners out there now risking everything for power without the slightest clue as to what damage they are doing to those engines:

http://i98.photobucket.com/albums/l251/GVR4_1670/DSC02825.jpg

http://i98.photobucket.com/albums/l251/GVR4_1670/DSC02822.jpg

http://i98.photobucket.com/albums/l251/GVR4_1670/DSC02829-1.jpg

Jack

[JayRolla]

Exactly why I asked how lean should I go. Ive always been tuning 11.5 to be safe. 22* is the stock timing map on the 1g and the car seems to love it. When I back it down dsmlink shows a noticeable amount of power loss.

[JackM]

You should be okay at 12.0 with a good WB that you can keep an eye on. Also make sure your injectors are totally clean and happy too. 11.5 might be a touch too rich, but it's definitely very safe.

Jack

[matthewdesigns]

I'm having my chip remapped to target 12:1 afr's and 21* timing, up from 11.5:1 and 19*. We'll see how it does after the swap.

[thiazole]

I'm running 12-12.2:1 and 18* total timing. It seems to work pretty well. Back in the day, I used to run a ****load of timing and burned a hole through my head similar to what Jack posted (although not quite that bad). Right now, I'm probably being a little conservative, but I know this combo still makes good power and is safe.

[D Walker]

Recently I learned of a certian Subaru that while being tuned had the WG hose blow loose allowing the car to hit north of 35psi. The injectors maxed out, and the AFRs showed around 17.5/1. No knock was recorded. The car ran fine and boosted normally afterwards. As far as I am aware the engine is still in one piece. It made no power, but that seems to be about it.
There are specific rules as to what you can and cannot get away with when tuning a cars timing and fuel. Things like bore size, rpm, cam profile, etc. all have more to do with what the car requires than anything else and if you dont understand all of the dynamics involved dont try and push the envelope unless you like picking up pieces of engines-or, if your like me, push the envelope on YOUR car to see what you can and cant get away with and be prepared to live with those consequences.

IMHO timing and running an e85 car over-rich and with overly conservative timing is much scarier than running it leaner with reasonable timing. Running an engine in this way invites pre-ignition (when the un-burned fuel left in the cylinder ignites while the piston is on its downstroke immediately prior to the compression stroke) which will burn holes right in things, like cylinder heads and pistons.

Other things to remember about tuning-
Widebands only read burned fuel, not unburned, so if your overly rich or the timing is retarded to the point the fuel is leaving the cylinder head unburned you will read lean or lean-ish but the reality is your rich and doing bad bad things.

Timing will affect AFR- no idea why people forget that

AFR is not as important as timing to the tune, a proper tuning procedure is to get the timing close, work with fuel, work with timing again, then work with fuel, and repeat until you have "inched up) on a workable timing/fuel setup. Just locking in the timing to get "no knock" and then dialing in an AFR you think works is not only the lazy mans way of tuning its just plain stupid.

Also EGT's are about useless for tuning a car 99%of the time, Most are slow to react and by the time they indicate an issue, the damage is done. That said, they work fairly well if you have the engine/car on a loading dyno and are doing steady state tuning.

[Cloud]

Don, a few things about your post I would like to discuss.

I see your point about running rich and overly conservative on timing leading to preignition but I think that is misleading as the conditions for that to happen are out of what most normal people would tune for. We are talking past 10:1 (gas equivalent) afr's and less than 5 degrees of advance for the most part, which I doubt anyone will tune for.

In the normal tuning window I think that most people would consider ok, slightly richer mixtures (10:1<) are going to yield a better safety margin still. Conservative timing as well.

Unburned fuel is not going to read lean on a wideband. Unburned oxygen however will read lean. So if you misfire or have still combusting mixture at the o2 sensor you will read lean. If you just run rich and still have complete combustion there will not be a lean condition at the o2 sensor. Again I think that this is something well out of the range most people will end up with in their tuning process.

The relationship between timing and afr in the public eye still sometimes boggles me. I am aware that AFR has a large correlation to burn speed and thus required timing at a particular engine condition. I do not however see how timing necessarily changes the measured end gas AFR assuming complete cylinder combustion and timing within a reasonable range of values.

EGT's... I don't know why people use these to tune? They tell you when the stock ecu is pulling timing I guess... otherwise I would most likely only use it on a diesel to tell when I am pushing it too rich and going to melt my turbine.

[D Walker]

Don, a few things about your post I would like to discuss.

I see your point about running rich and overly conservative on timing leading to preignition but I think that is misleading as the conditions for that to happen are out of what most normal people would tune for. We are talking past 10:1 (gas equivalent) afr's and less than 5 degrees of advance for the most part, which I doubt anyone will tune for.

You would think so, but you would be surprised how often I see cars tuned "conservatively" running 10:1 or worse and with almost no timing. For some reason "tuners" only understand knock, not pre-ignition

In the normal tuning window I think that most people would consider ok, slightly richer mixtures (10:1<) are going to yield a better safety margin still. Conservative timing as well.

10:1 on a low compression engine running e-85 is too rich, and can be an issue.

Unburned fuel is not going to read lean on a wideband. Unburned oxygen however will read lean. So if you misfire or have still combusting mixture at the o2 sensor you will read lean. If you just run rich and still have complete combustion there will not be a lean condition at the o2 sensor. Again I think that this is something well out of the range most people will end up with in their tuning process.

Redicued timing can and will show "lean"- and by lean I mean say 12.5/1 when its really much much richer, and while literally blowing unburned fuel out into the exhaust where the 02 sensor doesnt read it. The freaky thing is depending on a combination of factors the EGT's may be high from the retarded timing allowing the fuel to continue to burn in the manifold or very low because the timing is dumping unburned fuel into the exhuast where it doesnt burn at all until it hits the outside air on exiting the exhuast and ignites.

The relationship between timing and afr in the public eye still sometimes boggles me. I am aware that AFR has a large correlation to burn speed and thus required timing at a particular engine condition. I do not however see how timing necessarily changes the measured end gas AFR assuming complete cylinder combustion and timing within a reasonable range of values.

Agreed- all I can think of is the majority of "tuners" learned to "tune" from reading forums or online articles-maybe a book from the library? I dunno...

EGT's... I don't know why people use these to tune? They tell you when the stock ecu is pulling timing I guess... otherwise I would most likely only use it on a diesel to tell when I am pushing it too rich and going to melt my turbine.
Yeap.