What causes bucking
08-17-2007, 09:56 AM
#1
Teching In
Thread Starter
iTrader: (1)
Join Date: Mar 2006
Posts: 38
Likes: 0
Received 0 Likes
on
0 Posts
What causes bucking Generally speaking (taking the tune out of it) what causes the low RPM bucking and surging with larger cams? Is it duration, overlap or something else. AKA which of these would be worse or would they be the same given the same lope profile?
230/232 114 Overlap -> 3
222/224 110 Overlap -> 3
230/232 114 Overlap -> 3
222/224 110 Overlap -> 3
08-17-2007, 10:15 AM
#2
I would say the 222/224 w the 110 lsa
Heck I have a hotcam and that thing bucks a lil even at like a 25 mph coasting!
well as expected even in traffic, but that is the price you pay!
I dont mind it just pull the clutch and slip it a lil, problem solved!
Heck I have a hotcam and that thing bucks a lil even at like a 25 mph coasting!
well as expected even in traffic, but that is the price you pay!
I dont mind it just pull the clutch and slip it a lil, problem solved!
08-17-2007, 11:23 AM
#4
Good tuning can get rid of most bucking. The thing is though, it can be time consuming to do a full RAF assesment, tweak IAC effective area, and work spark down so I beleive that many tuners just "get it close" and move on. Of course if you have your own software you can affors to be picky about it. It's always worse with the lower LSA.
08-17-2007, 12:31 PM
#5
TECH Addict
iTrader: (10)
Join Date: Jun 2004
Location: Commerce Twp, MI
Posts: 2,918
Likes: 0
Received 0 Likes
on
0 Posts
Short answer...bucking is caused by air, fuel, and spark being wrong and sometimes the PCM trying to correct for those inconsistencies. Too much timing, too much IAC, or inconsistent AFR's can all lead to surging/bucking.
08-17-2007, 12:35 PM
#6
Overlap is whats the cause. The more overlap, the harder to tune it out. So, its a combination of both your duration and LSA. Once you get enough overlap, you cant tune all the surge out.
And as Frost stated, most people get em close. There are some tricks to cleaning it up tho.
And as Frost stated, most people get em close. There are some tricks to cleaning it up tho.
Trending Topics
08-17-2007, 06:32 PM
#9
Teching In
Thread Starter
iTrader: (1)
Join Date: Mar 2006
Posts: 38
Likes: 0
Received 0 Likes
on
0 Posts
I know the tune can have a lot (if not all to do with correcting it) but I also know the bigger the cam the more of an issue it can be. My question was is this because of overlap or duration?
08-17-2007, 06:51 PM
#10
Originally Posted by blackey
I know the tune can have a lot (if not all to do with correcting it) but I also know the bigger the cam the more of an issue it can be. My question was is this because of overlap or duration?
You figure your overlap by both your duration and LSA.
So, in a sense, its from both. But, the root cause is overlap.
And, there are some cams you cant get all of it out.
08-19-2007, 01:57 PM
#11
TECH Regular
iTrader: (7)
Join Date: Jun 2005
Location: Mass
Posts: 438
Likes: 0
Received 0 Likes
on
0 Posts
This has always puzzled me? Everyone always says overlap/ duration. My cam is 224 DUR and 114 LSA. I had ZERO bucking issues for over a year. I added a turbo and 60 LB injectors, now at 1400-1500 RPM it bucks. The cam is the same. The only low end tune related issue (at the beginning) was the IFR was changed for the larger injectors.
08-19-2007, 02:17 PM
#12
Originally Posted by zapp168
This has always puzzled me? Everyone always says overlap/ duration. My cam is 224 DUR and 114 LSA. I had ZERO bucking issues for over a year. I added a turbo and 60 LB injectors, now at 1400-1500 RPM it bucks. The cam is the same. The only low end tune related issue (at the beginning) was the IFR was changed for the larger injectors.
Also, 60 # injectors may be doing some funky stuff at shorter DCs.
08-20-2007, 08:29 AM
#13
TECH Regular
iTrader: (7)
Join Date: Jun 2005
Location: Mass
Posts: 438
Likes: 0
Received 0 Likes
on
0 Posts
Originally Posted by edcmat-l1
Putting a turbo on it changed the way it scavenges, which is similar to putting a longer duration, tighter LSA cam in it. My opinion, anyways.
Also, 60 # injectors may be doing some funky stuff at shorter DCs.
Also, 60 # injectors may be doing some funky stuff at shorter DCs.
