Idle and part throttle tuning?
03-17-2004, 03:29 PM
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Idle and part throttle tuning? Right now I have a small problem bothering me. My car is running lean in open loop but goes rich when in closed loop.
Example:
Start car and it surges a little for about 45 seconds(maybe more??) which leads me to believe that it is slightly lean.
After it warms up a bit(closed loop) and the O2's kick in it goes rich. And stays rich from idle to part throttle cruise(850-2400rpm). LTrims 0 to +7 usually +5 or +6 at idle.
My VE table is scaled 60%, 80%, 90% at 400, 800, 1200. Also, my TB hole is enlarged slightly from the last cam.
Now, fixing the open loop lean problem seems easy enough...raise my VE values until it clears up. But won't that make my rich condition in closed loop even worse?
Example:
Start car and it surges a little for about 45 seconds(maybe more??) which leads me to believe that it is slightly lean.
After it warms up a bit(closed loop) and the O2's kick in it goes rich. And stays rich from idle to part throttle cruise(850-2400rpm). LTrims 0 to +7 usually +5 or +6 at idle.
My VE table is scaled 60%, 80%, 90% at 400, 800, 1200. Also, my TB hole is enlarged slightly from the last cam.
Now, fixing the open loop lean problem seems easy enough...raise my VE values until it clears up. But won't that make my rich condition in closed loop even worse?
03-17-2004, 08:58 PM
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Originally Posted by NO CATZZ
Right now I have a small problem bothering me. My car is running lean in open loop but goes rich when in closed loop.
Example:
Start car and it surges a little for about 45 seconds(maybe more??) which leads me to believe that it is slightly lean.
After it warms up a bit(closed loop) and the O2's kick in it goes rich. And stays rich from idle to part throttle cruise(850-2400rpm). LTrims 0 to +7 usually +5 or +6 at idle.
My VE table is scaled 60%, 80%, 90% at 400, 800, 1200. Also, my TB hole is enlarged slightly from the last cam.
Now, fixing the open loop lean problem seems easy enough...raise my VE values until it clears up. But won't that make my rich condition in closed loop even worse?
Example:
Start car and it surges a little for about 45 seconds(maybe more??) which leads me to believe that it is slightly lean.
After it warms up a bit(closed loop) and the O2's kick in it goes rich. And stays rich from idle to part throttle cruise(850-2400rpm). LTrims 0 to +7 usually +5 or +6 at idle.
My VE table is scaled 60%, 80%, 90% at 400, 800, 1200. Also, my TB hole is enlarged slightly from the last cam.
Now, fixing the open loop lean problem seems easy enough...raise my VE values until it clears up. But won't that make my rich condition in closed loop even worse?
If your closed loop LTFTs are positive (+5 to +7 as you say), then you are not rich at all, but lean. Hence the LTFT is positive (adding fuel in an attempt to correct the lean condition). But, that addition of fuel may cause you to be rich at WOT if the LTFTs lock at that positive value, thus adding the additional fuel that may not be needed at WOT.
I would adjust the IFR table to get the part throttle LTFT to go 0 or negative at part throttle. I had to scale my whole IFR table by 90% to get -10 to 0 LTFTs in all the cruising fuel trim cells......
If you are happy with your warm starts, then you could probably leave the VE table alone.....
03-18-2004, 07:04 AM
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Thanks. I know that my usage of the terms of rich and lean are different...I go by the tailpipe sniff test. Yes, if my LTrims are + that means the PCM is dumping fuel to compensate for a lean condition which in turn makes it rich out the pipe.
Here is what I did:
Put the VE table back to stock. Now my part throttle LTrims are damn near perfect but cold start sucks. I have to hold it at 1200rpm for a few seconds before it will idle on its own. After about 30 seconds it will idle just fine but I have to let it warm up before putting it in gear.
Trial and error. Sometimes I wish I had a carberator so I could be done with this whole mess. But then you can't have 400+rwhp and 20+ mpg with a carberator.
Thanks
Josh
Here is what I did:
Put the VE table back to stock. Now my part throttle LTrims are damn near perfect but cold start sucks. I have to hold it at 1200rpm for a few seconds before it will idle on its own. After about 30 seconds it will idle just fine but I have to let it warm up before putting it in gear.
Trial and error. Sometimes I wish I had a carberator so I could be done with this whole mess. But then you can't have 400+rwhp and 20+ mpg with a carberator.
Thanks
Josh
03-18-2004, 05:53 PM
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For your cam, I would try 65-70% (400rpm), 70-75% (800rpm), 75-80% (1200rpm) on the VE table.
And if your LTFTs were +7 or so, then I'd multiply the whole IFR table by about 90-93%, and see if that gets your LTFTs to an average somewhere between -10 to 0.
Give the car about 50 miles of drive time and a few cold & warm starts to let the PCM learn. Then re-evaluate....
If the LTFTs stay 0 or less, then you can start messing with the PE table to lean out WOT.
And if your LTFTs were +7 or so, then I'd multiply the whole IFR table by about 90-93%, and see if that gets your LTFTs to an average somewhere between -10 to 0.
Give the car about 50 miles of drive time and a few cold & warm starts to let the PCM learn. Then re-evaluate....
If the LTFTs stay 0 or less, then you can start messing with the PE table to lean out WOT.
