6spds, Cams, Bucking---What's the real deal
09-26-2006 | 07:51 PM
#61
Originally Posted by GuitsBoy
Until a tuning genious can lay out a step by step procedure on how to tune a big cam to not buck, im gonna have to say that no tune will ever completely eliminate it. Sure I can easily drive around the problem areas, but that dosnt mean its eliminated. Im very particular about my tune. Ive tried positively everything and I read constantly in the tuning forum and the HPT board. Nobody that I know of has sufficiently explained how to aleviate bucking. The best ive seen is a few coverups. They seem to work fairly well (although not entirely) but then once the weather changes, its back to bucking hardcore again. Wont somebody fess up and let the magic spell out of the bag?
The big ones that everyone mentions are
Fuel.....I'm as good as I'll get using a wide band
Spark.....it holds steady. Have tried everywhere from 23*-45*
Throttle cracker.....have been all over it. Add, subtract, zeroed out.
DFCO.....disabled
I dunno what I'm missing. The 224 cam was easy. The TSP Giant....little more work.
09-26-2006 | 08:58 PM
#62
Thread Starter
On The Tree
Joined: May 2006
Posts: 108
Likes: 0
This thread is getting more discussion than what I thought it would. Although mine might be able to be tuned completely out, it appears this is more common than I would have thought.
Who has the biggest cam with a 6 spd that has NO bucking at all????
Who has the biggest cam with a 6 spd that has NO bucking at all????
09-27-2006 | 11:21 AM
#65
On The Tree
Joined: Mar 2006
Posts: 105
Likes: 0
correct me if i'm wrong, but isn't a bucking under 1500 rpm's usual. Any rpm under 1500 is a huge lug on the motor, not to mention you have a cam. My car with stock cam bucks under 1300 rpm or so, and it only gets worse with a cam/rough idle car. I never drive under 1500 rpm's, it doesn't make sense.
09-27-2006 | 11:26 AM
#66
Originally Posted by mxmatt137
correct me if i'm wrong, but isn't a bucking under 1500 rpm's usual. Any rpm under 1500 is a huge lug on the motor, not to mention you have a cam. My car with stock cam bucks under 1300 rpm or so, and it only gets worse with a cam/rough idle car. I never drive under 1500 rpm's, it doesn't make sense.
09-27-2006 | 11:33 AM
#67
I agree. It's almost like it happens when just above a state of neutrality. Like when just letting it idle across a parking lot in gear with no throttle, after taking my foot off the throttle.
09-27-2006 | 02:01 PM
#68
To the last three posters, my stock M6 car will do this as well, in the same situation. Low (approx. walking speed) in first gear, clutch out, 0% to very light throttle, and typically decreasing rpms. I've since figured out that its better to clutch in and coast than endure the buck.
I'll be modding my car soon enough, and I'll do my best to tune it & make it liveable, but this isn't an operating condition that most cars excel in. I had a 5.0L Mustang years ago that would do the same thing. Come to think of it, both of my parent's economy cars did it too.
I'll be modding my car soon enough, and I'll do my best to tune it & make it liveable, but this isn't an operating condition that most cars excel in. I had a 5.0L Mustang years ago that would do the same thing. Come to think of it, both of my parent's economy cars did it too.
09-28-2006 | 09:29 AM
#69
TECH Resident
Joined: Jul 2005
Posts: 907
Likes: 1
From: NJ
Originally Posted by Pewterme
This thread is getting more discussion than what I thought it would. Although mine might be able to be tuned completely out, it appears this is more common than I would have thought.
Who has the biggest cam with a 6 spd that has NO bucking at all????
Who has the biggest cam with a 6 spd that has NO bucking at all????
09-29-2006 | 11:02 PM
#70
I'm having the same issues in parking lots, and other low RPM/low (or no) throttle situations. Patrick G's cam. Speed Inc. had my car on the dyno for 3 pulls before they told me it was tuned. I've been talking with Larry the last few weeks and I'm bringing my car back in Monday to have the tuner drive around with it a little bit and work out some of the issues (as well as tune the car below 3000RPM!).
I had absolutely zero problems like this when the car was stock. I don't think your stock cam car should be bucking under 1300..
I had absolutely zero problems like this when the car was stock. I don't think your stock cam car should be bucking under 1300..
09-30-2006 | 12:02 AM
#71
Originally Posted by GuitsBoy
Until a tuning genious can lay out a step by step procedure on how to tune a big cam to not buck, im gonna have to say that no tune will ever completely eliminate it. Sure I can easily drive around the problem areas, but that dosnt mean its eliminated. Im very particular about my tune. Ive tried positively everything and I read constantly in the tuning forum and the HPT board. Nobody that I know of has sufficiently explained how to aleviate bucking. The best ive seen is a few coverups. They seem to work fairly well (although not entirely) but then once the weather changes, its back to bucking hardcore again. Wont somebody fess up and let the magic spell out of the bag?
go out on a country road, put it on cruise at 1500, and use the VCM controls. Usually, bigger cams like to be richer than the tree hugging 14.7:1. For example, you could put my AFR to "12.7" and it would buck a lot less. So, use the VCM and change the AFR (note this is commanded, not necessarily actual). Also, you can add/subtract timing. You'd be surprised how much you can get done shortly with a friend.
i'm of the opinion that big cams will never drive like stock. by that rational, you could tune all the lope at idle out of them. granted, you can make it a LOT better, but they will 'lope' until they clean up at higher rpms.
09-30-2006 | 06:30 AM
#72
Originally Posted by Greg Fell
do you have a friend and HPT?
Yes, ive got my low end richened up. For the most part its around 14.0 and then works its way upwards from there. This is a true 14.0, not a lean condition that averages out with rich decel from a fat min inj pulsewidth. Any more fuel than this, and the bucking actually gets worse. Subtract and it gets worse. Im balanced on a knife edge, and that knife edge seems to move slightly with the weather conditions.
