Tuning... Lean or Rich?
12-07-2009, 05:35 PM
#1
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Join Date: May 2007
Location: OH
Posts: 564
Tuning... Lean or Rich?
I have been tuning a 98 cobra on and off using sniper SF. The current tune is:
Rear O2's off
EGR off
low spark - +1.0
mid spark - +1.5
high spark - +2.0
global spark - +2.0
low fuel - +0.6
mid fuel - +0.6
high fuel - +0.4
We just did some additional data logging with the LC1 as well as with recon and was wondering if someone could tell me if we are close. Pulls were in 2nd gear from 2500 - 6000. The car seems to be down some power up high but not sure if it is lean or rich as I have no clue as to how to read these graphs.
Rear O2's off
EGR off
low spark - +1.0
mid spark - +1.5
high spark - +2.0
global spark - +2.0
low fuel - +0.6
mid fuel - +0.6
high fuel - +0.4
We just did some additional data logging with the LC1 as well as with recon and was wondering if someone could tell me if we are close. Pulls were in 2nd gear from 2500 - 6000. The car seems to be down some power up high but not sure if it is lean or rich as I have no clue as to how to read these graphs.
Last edited by wolverine8490; 12-07-2009 at 05:37 PM.
12-07-2009, 09:41 PM
#2
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Join Date: May 2008
Posts: 213
Recon can only get mixture data from the O2 sensors, which are turned off at WOT. So in this case Recon isn't useful for getting AFR at WOT because it can't do that. However it is useful for seeing MAF counts and timing at WOT, so make sure you keep it around.
The LC-1 data is what we're after for WOT runs.
Here is your LC-1 graph:
Apparently, you recorded for 7.45 seconds, and your AF was pretty much at 14.7 the whole time. So, either you mistimed your LC-1 logging or your engine was at 14.7:1 through most of your pull, which is extremely lean. I'm betting on the mistiming thing.
In order to get useable data, we need the data logs from the entire run, and preferably for you to go WOT for longer than a few seconds. We need time for the AF to stabilize, so we can see where it centers around.
From your graph, the AF tanks down to about 11.9 right before cutting off, which is another reason I believe that you didn't give it enough time to actually read the WOT AFR. 11.9 is a much more reasonable AFR at WOT, and you're probably shooting for something like that at the end (are you NA or forced induction)?
If you can, do another, longer WOT run, and make sure you're datalogging the LC-1 the entire time. We need to see where your AF ratio stabilizes to see how your tune is doing. For what it's worth, Sniper tunes are very conservative, so I would imagine that your overall tune is rich which is a good thing.
The LC-1 data is what we're after for WOT runs.
Here is your LC-1 graph:
Apparently, you recorded for 7.45 seconds, and your AF was pretty much at 14.7 the whole time. So, either you mistimed your LC-1 logging or your engine was at 14.7:1 through most of your pull, which is extremely lean. I'm betting on the mistiming thing.
In order to get useable data, we need the data logs from the entire run, and preferably for you to go WOT for longer than a few seconds. We need time for the AF to stabilize, so we can see where it centers around.
From your graph, the AF tanks down to about 11.9 right before cutting off, which is another reason I believe that you didn't give it enough time to actually read the WOT AFR. 11.9 is a much more reasonable AFR at WOT, and you're probably shooting for something like that at the end (are you NA or forced induction)?
If you can, do another, longer WOT run, and make sure you're datalogging the LC-1 the entire time. We need to see where your AF ratio stabilizes to see how your tune is doing. For what it's worth, Sniper tunes are very conservative, so I would imagine that your overall tune is rich which is a good thing.
12-07-2009, 11:10 PM
#3
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Location: Saint Augustine, FL
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Why did you set the rpm based fueling settings as you did, was this based on some observation of the LC-1?
---------------------
low fuel - +0.6
mid fuel - +0.6
high fuel - +0.4
---------------------
These settings lean the mixture quite a bit (0.4 to 0.6 "AFR"). In SF the selections affect the AFR--I.e. selecting +0.6 adds 0.6 to the AFR in the indicated range--12.0:1 will become 12.6:1.
As to the LC-1 logging, as it only logs AFR (and not load or even rpm) it's pretty much worthless--my advice is to reset the fueling settings to 0.0 and watch the AFR while doing some WOT runs.
For n/a you want AFR at WOT to be 12.5:1 to 13.0:1 (I like the rich end as it allows a bit more timing).
Let us know what you see...
What octane fuel are you running?
Do you have a gauge connected to the LC-1, if so which one?
---------------------
low fuel - +0.6
mid fuel - +0.6
high fuel - +0.4
---------------------
These settings lean the mixture quite a bit (0.4 to 0.6 "AFR"). In SF the selections affect the AFR--I.e. selecting +0.6 adds 0.6 to the AFR in the indicated range--12.0:1 will become 12.6:1.
As to the LC-1 logging, as it only logs AFR (and not load or even rpm) it's pretty much worthless--my advice is to reset the fueling settings to 0.0 and watch the AFR while doing some WOT runs.
For n/a you want AFR at WOT to be 12.5:1 to 13.0:1 (I like the rich end as it allows a bit more timing).
Let us know what you see...
What octane fuel are you running?
Do you have a gauge connected to the LC-1, if so which one?
12-08-2009, 06:50 AM
#4
3rd Gear Member
Thread Starter
Join Date: May 2007
Location: OH
Posts: 564
Yeah I forgot when we were logging you want to do the pulls in 3rd and not in 2nd. I think that is the reason for the short log. We will do some pulls in 3rd now with the fuel back to stock and see where we are.
We adjusted the fuel/spark timing according to the first log we pulled off the car before we did any tuning. I will re-attach that to the message. It looked like it was a lot closer to where we needed to be at that point. The main issue we were having with the stock tune was the car was backfiring when he was shifting gears at WOT which I believe is due to the extra air with the IMRC delete. I will attach the first runs we did with no tuning and see what you think. Right now we are runing a 93 octane tune.
The cobra is NA. We do have a guage hooked up in the car. That is another issue we are having though. I have the same setup in my stang. When we turn the cobra on the guage counts up to 15.x and stops. My 96GT counts up to 22.x and then stops. There is something messed up with the guage or the wiring to the guage but I have not had the time to mess with it yet as the output on the PC seems correct. Here is the kit we bought http://www.summitracing.com/parts/INN-3796/.
Thanks for the help on this. We just cant seem to get the car running right. Before the tuning and the IMRC delete, he used to be able to break 295/35/18's loose when he hit 2nd. The car does not even have the power to do that anymore.
We adjusted the fuel/spark timing according to the first log we pulled off the car before we did any tuning. I will re-attach that to the message. It looked like it was a lot closer to where we needed to be at that point. The main issue we were having with the stock tune was the car was backfiring when he was shifting gears at WOT which I believe is due to the extra air with the IMRC delete. I will attach the first runs we did with no tuning and see what you think. Right now we are runing a 93 octane tune.
The cobra is NA. We do have a guage hooked up in the car. That is another issue we are having though. I have the same setup in my stang. When we turn the cobra on the guage counts up to 15.x and stops. My 96GT counts up to 22.x and then stops. There is something messed up with the guage or the wiring to the guage but I have not had the time to mess with it yet as the output on the PC seems correct. Here is the kit we bought http://www.summitracing.com/parts/INN-3796/.
Thanks for the help on this. We just cant seem to get the car running right. Before the tuning and the IMRC delete, he used to be able to break 295/35/18's loose when he hit 2nd. The car does not even have the power to do that anymore.
Last edited by wolverine8490; 12-08-2009 at 06:54 AM.
12-08-2009, 08:20 AM
#5
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Join Date: Dec 2006
Location: Saint Augustine, FL
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Based on those logs the adjustments you made in SF should get the AFR up to 12.5:1 to 12.7:1--which is good for n/a.
However...
The IMRC delete is generally not "good thing" when running n/a. They are there to improve charge velocity at lower rpms and loads, actually because the 4V engine can breath so well that charge velocity falls off below 2500 rpm or so.
Ford put them there to improve low rpm (< 3k) engine performance, removing them on a n/a setup will reduce low-end torque a bunch.
Form Greg Banish's Engine Management book:
"Generally speaking, very little extra power is gained by removing these [IMRC] from the intake tract, and the low-end torque loss is usually significant enough to be noticed by the average driver."
Greg does not recommend removing them on anything but track cars that spend their lives running over 3k rpm. This may be the entire source of the performance hit you have observed...
However...
The IMRC delete is generally not "good thing" when running n/a. They are there to improve charge velocity at lower rpms and loads, actually because the 4V engine can breath so well that charge velocity falls off below 2500 rpm or so.
Ford put them there to improve low rpm (< 3k) engine performance, removing them on a n/a setup will reduce low-end torque a bunch.
Form Greg Banish's Engine Management book:
"Generally speaking, very little extra power is gained by removing these [IMRC] from the intake tract, and the low-end torque loss is usually significant enough to be noticed by the average driver."
Greg does not recommend removing them on anything but track cars that spend their lives running over 3k rpm. This may be the entire source of the performance hit you have observed...
12-08-2009, 10:24 AM
#6
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Thread Starter
Join Date: May 2007
Location: OH
Posts: 564
Yeah we talked about that last night. He threw away all of the old parts for the IMRC. We may try and find another set and put them back on. I have read that it is very difficult to tune a NA cobra with the IMRC's removed. I was hoping we could do it without them, but maybe I will just tell him to find some and re-install then start tuning from there.
12-08-2009, 10:33 AM
#7
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Join Date: May 2007
Location: OH
Posts: 564
low spark - +1.0
mid spark - +1.5
high spark - +2.0
global spark - +2.0
low fuel - +0.6
mid fuel - +0.6
high fuel - +0.4
12-08-2009, 12:31 PM
#8
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Join Date: Dec 2006
Location: Saint Augustine, FL
Posts: 10,938
Re: IMRCs, they are both intuitively and actually intake restrictions--however at lower engine speeds (under 3k rpm) they are good restrictions that increase the intake charge velocity. This causes more air/fuel (which has mass) to flow into the cylinder because it's traveling faster. At higher speeds, and if properly designed, the restriction they add is negligible for street performance.
Removal (of the IMRCs) is really only desirable when running a "*****-and-all" positve displacement blower setup, one without any sort of bypass valving, where the blower blows all the time and excess boost is vented via a BOV.
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