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Discussion and questions related to the course Understanding AFR
Im a little confused about the correct afr using methanol and the different target that i supposed to have on the idle, mid and power range... im using a methanol wideband that reads from 3.75 to 7.0 afr...
Lambda 1 for methanol is 6.4 (Andre can you confirm ?)
The rules are the same than pump gas
around 6.1 / 6.4 (0.95 / 1 lambda) at idle
5.4 / 5.7 for power on an NA engine
and up to 4.8 for power on a turbo engine
I would strongly suggest that you consider tuning in lambda as it will make the transition between different fuels so much easier.
Lud086 is right, the stoichiometric AFR for methanol is 6.4:1 so on methanol 6.4:1 = 1.00 lambda.
The key with methanol is that it is very tolerant of a rich mixture (provided you have plenty of spark energy), but very intolerant of a lean mixture. For this reason you're always best to aim richer and be happy with an engine that will make great power and offer good reliability.
You haven't mentioned if you are FI or NA so I'll gives some guide lines for both.
Idle/cruise 0.90-0.95 lambda (normally methanol is only used in a race application and hence cruise economy is almost irrelevant)
Full power NA - 0.75-0.80 lambda
Full power FI - 0.65-0.70 lambda (you may even need to go richer than this at very high boost levels)
If you want to convert the lambda targets to AFR, simply multiply by the stoichiometric AFR. ie 0.65 * 6.4 = 4.2:1
did u recommend any specific brand for the lambda sensor that i should buy like a bosch type or any other or if u have like a part number..
or i think the aem uego sensor is capable to change the reading to lambda?
There are a wide range of wideband units on the market that will do a great job. When tuning on methanol you are shooting for very rich AFR numbers and hence some sensors won't read rich enough. The NTK sensor I use will only read as rich as 0.68 (ish) which for example isn't enough for a turbo application.
I would suggest looking for a unit running the LSU sensor. The NGK AFX unit is a well respected option and can now be purchased through Ballenger Motorsport - http://www.bmotorsports.com/shop/product_info.php/cPath/103_107/products_id/357/
I'm surprised you get limited by the NTK sensor Andre. Too old sensor maybe ?
The AFR500 (direct replacement of the NGK AFX) allegedly go from 9.0 (0.62) to 16.0 (1.09)
It can be modified by ECM (the actual manufacturer) to display lambda instead of AFR, and extend the range to 0.6 - 1.3 with the same Bosch or NTK sensor. That's why I'm surprised. If ECM can reach 0.6 I don't think the limiting factor is the brand of sensor itself.
It may well be due to a limitation imposed by the Motec controller. It's interesting though because my dynapack had a Motec PLM fitted and configured to use the LSU 4.2 sensor. I got sick of the life span of the sensors and recalibrated the PLM to use the NTK sensor. On the LSU sensor the PLM would read to about 0.64-0.65 but on the NTK it flatlines around 0.68
ECM has the AFM1000 type D version realy setup for methanol tuning, going down to lambda .3
D Version: 0.30 to 1.15 λ, 4.37 to 16.76 AFR (gasoline), 1.94 to 7.44 (methanol)
I was planing to send one of mine in incase I do any more methanol tuning in the future.
The only time I care to deal with AFR is intial ecu setup otherwise I will use lambda.
If you are gonna do tuning on methanol and can't afford the AFM1000 I would suggest using a wideband with the NTK sensor, the Haltech methanol wideband would probably give you the range you need.
A colleague of mine who drag races a methanol fuelled FJ20 powered rail uses the ECM1000 and swears by it. On paper the measurement range is ideal for methanol. I haven't personally had the opportunity to use one.
The ECM AFM1000 don't use your average NTK sensor but a "lab grade" version. (to keep good accuracy further apart of lambda 1.00)
A big part of the price is due to this.