question about bucking...
05-19-2006, 12:12 PM
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question about bucking... hey guys i have the cam in sig and i had horrible bucking at first... now that i have spent hours tuning it the bucking is gone...it honeslty drives like stock...
The only problem that i have lingering that ihave not spent too much time with is this.
If i am just regularly cruising at about 1500-1700 rpm and i am only applying enough throttle to maintain speed i get a lil bucking. now i understand that bucking is often associated with a lean condition and this spot i have running at around 14:1. i have sinced richened it to 13.8 (i have not tuned for this or tested it yet)
But my main question is how can Ignition advance affect bucking? can i increase or reduce timing to help? my timing in this area is averaging from 32-35 degrees of advance.
Thanks
Louie Panayi
The only problem that i have lingering that ihave not spent too much time with is this.
If i am just regularly cruising at about 1500-1700 rpm and i am only applying enough throttle to maintain speed i get a lil bucking. now i understand that bucking is often associated with a lean condition and this spot i have running at around 14:1. i have sinced richened it to 13.8 (i have not tuned for this or tested it yet)
But my main question is how can Ignition advance affect bucking? can i increase or reduce timing to help? my timing in this area is averaging from 32-35 degrees of advance.
Thanks
Louie Panayi
05-19-2006, 12:41 PM
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More advance wants more fuel.
What it looks like to me is that your advance is a little high.
You should be able to get away with up to 15:1 AFR at a steady state cruise, but you may have to lower the advance.
Normally when you lower the advance the AFR richens up on its own a little bit, so you may have to compensate.
If your MAP reading is jumping around at a steady-cruise in this RPM range, then that could explain the bucking by both the fuel and spark changing back and forth from one VE cell to another VE cell as the MAP changes.
Even if the MAP is fairly steady it could be affected by an adjacent cell.
Look for a much leaner VE cell right next to the one you're cruising in. Same goes for the spark table, though you should see if your spark is changing on your datalogs.
The area of the VE & spark table that is between your steady cruise and moderate acceleration is the trickiest part to fine tune. Just remember that as MAP increases during the first part of acceleration, the engine will want more fuel and less spark. Remember that the RPM will also be going up during this acceleration.
When you let off the throttle or hold it steady, the RPM will still be up, but the MAP will go down, and you need less fuel and more spark again.
You'll probably see an eliptical shaped diagonal area of table cells being used during most of your cruising. This is where most of the fine tuning happens.
What it looks like to me is that your advance is a little high.
You should be able to get away with up to 15:1 AFR at a steady state cruise, but you may have to lower the advance.
Normally when you lower the advance the AFR richens up on its own a little bit, so you may have to compensate.
If your MAP reading is jumping around at a steady-cruise in this RPM range, then that could explain the bucking by both the fuel and spark changing back and forth from one VE cell to another VE cell as the MAP changes.
Even if the MAP is fairly steady it could be affected by an adjacent cell.
Look for a much leaner VE cell right next to the one you're cruising in. Same goes for the spark table, though you should see if your spark is changing on your datalogs.
The area of the VE & spark table that is between your steady cruise and moderate acceleration is the trickiest part to fine tune. Just remember that as MAP increases during the first part of acceleration, the engine will want more fuel and less spark. Remember that the RPM will also be going up during this acceleration.
When you let off the throttle or hold it steady, the RPM will still be up, but the MAP will go down, and you need less fuel and more spark again.
You'll probably see an eliptical shaped diagonal area of table cells being used during most of your cruising. This is where most of the fine tuning happens.
yeah I knew that.
05-19-2006, 05:02 PM
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lol good deal.
Man you are saving my ***...with all of your help the camaro is running great..i am honestly amazed myself...i cant believe that it runs this good with a cam that big...
istill have the 3:42s...
Louie
Man you are saving my ***...with all of your help the camaro is running great..i am honestly amazed myself...i cant believe that it runs this good with a cam that big...
istill have the 3:42s...
Louie
05-19-2006, 10:34 PM
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I just got a chance to look at the tune & log you posted links to.
Your timing isn't off far enough to cause the bucking.
It looks kind of obvious to me that it's a VE problem. Your VE table is a mess. It's very spotty without a smooth progression from low to high loading. There's a few lean holes in there near the range you're talking about that need to be cleaned up.
I'd lower the timing a couple of degrees and do a LOT of fixing in the VE table.
I could mail you an example tun file with the VE modified in such a way so you see what I'm talking about, if you'd like. I should have some time in the next few days. pm me your email.
Dan
Your timing isn't off far enough to cause the bucking.
It looks kind of obvious to me that it's a VE problem. Your VE table is a mess. It's very spotty without a smooth progression from low to high loading. There's a few lean holes in there near the range you're talking about that need to be cleaned up.
I'd lower the timing a couple of degrees and do a LOT of fixing in the VE table.
I could mail you an example tun file with the VE modified in such a way so you see what I'm talking about, if you'd like. I should have some time in the next few days. pm me your email.
Dan
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05-20-2006, 09:31 AM
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http://h1.ripway.com/01blkss/Log_0010.efi
http://h1.ripway.com/01blkss/richerdriving_TC_TF.tun
These are the newest ones...and by looking at your 10:30 post i am assuming that these are not the ones that you saw... take a look at this one the VE table is a million times better.
I posted it at like 2 am last night on EFilive.
Louie
http://h1.ripway.com/01blkss/richerdriving_TC_TF.tun
These are the newest ones...and by looking at your 10:30 post i am assuming that these are not the ones that you saw... take a look at this one the VE table is a million times better.
I posted it at like 2 am last night on EFilive.
Louie