AFR raises with methanol

O

OneQuikSix

Member
Joined
Jun 7, 2001
I did some preliminary tuning today in the 90deg weather today. I got the car running smoothly at 13-14 psi boost on 93 octane. After several hits to establish a baseline, it looks like the fuel system is way rich (which I expected at lower boost levels). Rich/lean measured by Plx wideband and stock O2 sensor. Afr is low 10.0. Next, I turned on the Alkycontrol kit (knob on 6). At the same boost levels, the AFR goes way lean (14.5). The IAT dropped to the mid 80's. Is it possible the drastic reduction in IAT temps require that much more fuel (kinda like nitrous on a much smaller scale)? Here is what I know...

Fuel pressure rises with boost.
Plenty of voltage from alternator.
Zero knock

It looks like the fuel system is keeping up fine but the tune needs a lot more fuel added to the WOT fueling. Anyone have similar experiences? I see most people have to trim fuel when alky kit activates. I have logs but will have to attach them later.

Posted from the TurboBuick.Com mobile app
 
[quote="OneQuikSix, post: 3248761, member: 180]..... Is it possible the drastic reduction in IAT temps require that much more fuel (kinda like nitrous on a much smaller scale)? Here is what I know.........[/quote]

With lower IAT you have more air going into the engine, so at a given boost you do need more fuel since it takes the proper ratio of fuel/air to make HP, in this case you WILL be making more HP! :)

If Eric's SD program is set up and tuned properly, it should be compensating by adding fuel for the added air if your fuel pump is up to the job of providing enough fuel?
 
Should get richer once the systems starts spraying as methanol is a fuel.
 
It's funny because I never thought about what was happening when methanol was injected beyond its knock suppression ability. At the low boost levels I am at now, my IAT's would peak around 135 degrees without the alky. With the alky, the IAT's hover around 80 degrees at the same boost level. That is a 55 degree reduction (10 degrees less than ambient!!!).

I'm going to add some mid-boost fuel and see what happens. I've already increased the WOT fuel to the max! If this doesn't help, I guess I will need to have Eric make some adjustments.
 
Should get richer once the systems starts spraying as methanol is a fuel.
Click to expand...

Thanks for chiming in Julio. Another possibility I just thought of is the age of the methanol. I've had it for a few years in my garage. If water has built up inside, could that cause my symptoms? I know the engine stumbles and the IAT's drop when I press the test button. I didn't bother looking at the AFR/O2 to see if they display a rich spike. I'll check into this later today.
 
If the car still has the OE narrow band sensor you can validate the wideband reading. If the 14.5 is real, the narrow band sensor should see it too.

If the engine is misfiring, it would indicate lean. Not consuming the oxygen through combustion, the oxygen sensors would pick it up. Should really be laying over alot if that is happening.
 
According to the OE oxygen sensor, the car is lean. Obviously, I took my right foot out of the equation almost immediately but I did feel the car fall on its face big time!
 
Do you think it was misfiring?

if so, could be plugs. what's the gap?
 
I didn't hear anything unusual. Plugs are Autolite 23's or 24's...I can't remember. They are gapped at 0.030." The data screams LEAN and the performance echos the data. I guess I need to determine whether the methanol is bad (stale) or if the car simply needs more fuel added to the chip.
 
It appears my methanol is bad. While the engine stumbles and the IAT's drop when I push the test button, neither the wideband nor stock O2 registered a rich spike. I tried this several times to verify. Now the question is what happened to my meth and what did I spray into my engine?

Posted from the TurboBuick.Com mobile app
 
OK...update.

I completely drained and refilled the reservoir with new meth from sealed containers. After pressing the test button, the same thing happened...no rich spike. So, I guess the meth was fine after all. The next thing I will try is lowering the alky gain knob and see how the car responds.

Posted from the TurboBuick.Com mobile app
 
For those of you following this thread...stand by. After reviewing my logs, I noticed the chip started doing some wacky things as soon as I turned on the closed loop WOT fueling. What's interesting is the effect on mid-boost fueling (steady 14.5ish AFR) even though the closed loop correction should only affect fueling when boost is at higher levels. I am starting to wonder if there may be some correction occurring at idle too. This would explain why the car doesn't experience a rich spike when I press the test button. I am going to turn off closed loop WOT fueling and see what happens next.
 
The SD chip has correction capability at idle, cruise, and WOT. It all depends on whether you have it turned on or not.
Depending on your alky settings you might not see an immediate rich spike when testing at idle. However, if it stumbles during the test, then it most likely is way rich. Maybe the wideband isn't working properly.
Try posting a log of the test.
Eric
 
Thanks for chiming in Eric. At this point, I've got the methanol turned off until I figure out what is happening with the AFR numbers. I turned off the WOT correction and had no change to the AFR's at idle, boost, etc... While I have never had any problems with my wideband O2, it would explain what is happening. The car drives/idles smoothly. I just hope I haven't damaged something throughout the testing process. I'm going to inspect the spark plugs tonight when it cools off some. I have a PL log but my internet explorer will not allow me to upload it for some reason. Any idea how to test/recalibrate a PLX wideband O2?
 
Datalogging is SO important! I would have never been able to figure this out 10 years ago when I only had a scanmaster. After reviewing many logs from this past Saturday through today, I realized my PLX wideband is/was malfunctioning completely. Apparently, my malfunctioning PLX sensor causes the controller to send a signal of approximately 14.3 AFR when my car is running at any rpm and load. Because I had tunnel vision when reviewing the PL logs, I failed to notice the artificial lean condtion reported by the PLX in the frames (sometimes minutes) leading up to the run. On the worst pass, the boost crossed the threshold programmed into the SD chip whereby WOT fueling occurs. At this point, the chip saw an overly lean condition (that was artificially reported by the failing PLX) and threw a bunch of fuel at the car to compensate. This caused the car to nose over severely. The good news is my car never ran even remotely lean and I saw no knock throughout the testing. The bad news is I now must figure out my PLX problems and start all over with the tuning.
 
Some good news today. I swapped the old wideband sensor with a new one. It reads much better now at idle and spikes rich when I press the alky test button. Unfortunately, it is raining all day so no testing till Friday night. I'll be starting slow again without the alky till I make sure everything is working properly. Sure wish I could change the title of this thread to something more appropriate.

Posted from the TurboBuick.Com mobile app
 
It looks like everything is working the way it is supposed to. Now I have to start all over with the tuning process. But, that is the fun part.:D

Posted from the TurboBuick.Com mobile app
 
You must log in or register to reply here.

Similar threads

H
No start. Losing motivation.
2
Replies
22
Views
3K
phil_jordan
P
SteveZ82
Hard Start when Cold
Replies
15
Views
2K
SteveZ82
SteveZ82
J
Map sensor no longer reads 100 kpa with key on
Replies
1
Views
606
Chuck Leeper
Chuck Leeper
hflwyo
First data log with wideband chip
2 3
Replies
52
Views
3K
Ttype6
T
W
1987 Buick Grand National - Well maintained hardtop with upgrades
Replies
10
Views
6K
Chuck Leeper
Chuck Leeper
Top