AFR 13.3 w/o knock?!?
Thread Starter
Joined: Apr 2003
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From: Houston, TX
AFR 13.3 w/o knock?!?
My ecu+ shows me running ~13.3:1 AFR on WOT pulls nearly the whole way and I show 0 for knock count! My sensor is definatley working, I'm even getting phantom knock from my cams/mounts/etc. I'm still using mitsulogger for load and ecu+ for everything else. I'll post both files in a zip here. You can cross reference the times if you desire. Barring the idea that my WB is incorrect (it may be, but for the sake of argument) what the heck?! lol no knock at 25psi, 0-2 deg timing at peak torque, and water injection on 13.3 AFR? Doesn't sound reasonable to me. I used to get knock when I was running around 11.5... (this is all on 93 octane)
-my wideband reads ~14.7 at cruise and idle.
logs: http://filebox.vt.edu/users/utara/random/tune.zip
-for ECU+ users: I use GM 3-bar and set WB to PLX
-my wideband reads ~14.7 at cruise and idle.
logs: http://filebox.vt.edu/users/utara/random/tune.zip
-for ECU+ users: I use GM 3-bar and set WB to PLX
Thats the basic idea with water injection, with waters high latent heat of evaporation you can run much leaner AFR's while maintaining a very similar egt.
How much water are you running?
When was the last time you calibrated your wideband?
How long have you been using the sensor? How old is it? Have you used leaded gas while using this O2?
How much water are you running?
When was the last time you calibrated your wideband?
How long have you been using the sensor? How old is it? Have you used leaded gas while using this O2?
If your timing isn't set for bubba tuning there is no reason to knock. There is also no reason to run that lean because your loosing power at 13.0, I keep my AFR below 12.8.
Whatever you do, do not allow full load at 14.7, that would melt down your engine for sure!
Whatever you do, do not allow full load at 14.7, that would melt down your engine for sure!
On a Honda I just did, the WB was WAY OFF do to an over rich condition and subsequent fouling. When it went to the dyno it made 160whp with 13.5 AFR and getting it back to 11.5:1 (both time no knock) bumped it 180whp (@ 9psi with a Greddy kit) on a DD.
I had my car on the dyno yesterday, dyno operator was saying it was running lean so I quickly changed to the stock fuel maps - still lean
today I found an exhaust leak which could have caused the lean condition...
today I found an exhaust leak which could have caused the lean condition...
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NJ
I agree for the most part, I mean lets face it, hitting .5 or .6 on the head is herculean effort. Most of the reading I have done points to a 12.5 - or there abouts. Each combustion chamber being a little peculiar in its wants. But really fuel tuning to that point is obsessive. ie race tuning
All I'm saying is there is a range of afr that suits motors for best power, it may be 12, it may be 13. at least that is what I have read.
In the end it is a matter of providing just enough extra fuel that every bit of o2 in the charge can link up with the fuel in the time and space provided in the chamber.
If the chamber provided enough time and had the right shape an afr of 14.7 would be the best for power.
The last point, and I wish I knew the fix, There seems to be a mechanism within the ecu that richens the afr when the motor is driven hard for prolonged periods.
I recently logged some sessions and at the start of each I had what I wanted for afr, by the third lap the afr had dropped .5. Coolant and air temp were logged and nothing looked out of a narrow range.
I agree for the most part, I mean lets face it, hitting .5 or .6 on the head is herculean effort. Most of the reading I have done points to a 12.5 - or there abouts. Each combustion chamber being a little peculiar in its wants. But really fuel tuning to that point is obsessive. ie race tuning
All I'm saying is there is a range of afr that suits motors for best power, it may be 12, it may be 13. at least that is what I have read.
In the end it is a matter of providing just enough extra fuel that every bit of o2 in the charge can link up with the fuel in the time and space provided in the chamber.
If the chamber provided enough time and had the right shape an afr of 14.7 would be the best for power.
The last point, and I wish I knew the fix, There seems to be a mechanism within the ecu that richens the afr when the motor is driven hard for prolonged periods.
I recently logged some sessions and at the start of each I had what I wanted for afr, by the third lap the afr had dropped .5. Coolant and air temp were logged and nothing looked out of a narrow range.
Evolving Member
Joined: Sep 2006
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From: California
I dont get why meth/water would give you similar EGT's even though you get the advantage of latent heat from evaporation, that still only absorbs about 600 calories of heat per 1 gram of water evaporated. yes meth/water would decrease volatility of the entire fuel mixture, but i dont get how meth/water makes such a significant impact on EGT's we are talking high cylinder temps here.
Just like some people think runing a rich fuel mixture cools the cylinder temps because of more fuel, when really all more fuel does is slow the burn.
Just like some people think runing a rich fuel mixture cools the cylinder temps because of more fuel, when really all more fuel does is slow the burn.
Evolving Member
Joined: Sep 2006
Posts: 368
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From: California
wait nm, i just realized water has a pretty high specific heat in comparison to some object and 1 calorie heats up 1 gram of water by 1 C,
Nm i guess meth/water injection really will create a REALLY REALLY significant cooling effect if you think about it.
Damn evaporation kicks heats *** when you really break it down. 1 gram of water absorbs a crap load of heat.
Nm i guess meth/water injection really will create a REALLY REALLY significant cooling effect if you think about it.
Damn evaporation kicks heats *** when you really break it down. 1 gram of water absorbs a crap load of heat.
This is very true. This is why I am heavily thinking about running a small bit of water/methanol down here in SC. The weather here is changing now, and we are seeing some pretty cool late evening/night temperatures here now. During the June/July/August timeframe it's gets so hot & humid here that I usually have to pull about 3 degrees timing because the car doesn't like it. So far, I have developed a summer/fall map, and will be doing a winter map soon. Running a small amount of water injection during the hot summer months will allow me to be able to run my winter map all the time, witout knocking, and without running the heavy timing maps of a true full blown water/methanol set-up. I just want to do it for a few extra degrees (No more than 2-3), but use it mostly for the steam cleaning effects and slightly slightly increased knock threshold. (No big nozzles)
Thread Starter
Joined: Apr 2003
Posts: 1,580
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From: Houston, TX
lol, guys... I know that's too lean. Thanks for the advise. I'm just really pointing it out because I was shocked that it's not knocking... I fixed the intake manifold gasket and the leak must have been quite serious b/c now the same tune that was 11.5 before is 13.3. That's all I was pointing out. lol I don't shoot for 13's.
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From: Virginia Beach, Virginia
When your tuning with meth you should be tuning for a target lambda. That being you are reading the amount of oxygen in the exhaust stream. Since methanol and gasolene have different stoichiometric values you can't shoot for an AFR that is meant for gasoline when you are in fact running a mix of gas and meth. With that said if you want to hack your way through the tune meth needs to run richer than gas so if your target AFR is 12.0:1 on gas you should be shooting for richer than that when on meth. Or if you want to be accurate you need to know what lambda value your motor makes most power at (lets assume 12.0:1) you'll have a lambda of 0.816. Now methanol runs stoich at 6.4:1 AFR. If you were running on straight methanol your same motor would like an AFR of 6.2:1. You can now easilly see that if you have your wideband set to gas and your running straight meth and your wideband is reading 12.0:1 your going to melt down (actually the motor wouldn't even run, you would probably just lean misfire). Thing is if your injecting say 10% meth under boost you can't really even guess what AFR to tune the car for without some fancy math, and why not just tune for a lambda value that automatically tells you the ratio of unburnt oxygen irregardless of what kind of fuel or mixes of fuels you are using. With that being said, if your truly running 13.3:1 with meth and not lean misfiring or hurting parts somebody needs to give you a cookie.
1) he's injecting water, not meth, it's inert and does not change the AFR
2) irregardless isn't a word
3) I like cookies