18 Degree overlap - surging
Thread Starter
Race Director
Joined: Dec 2004
Posts: 13,760
Likes: 75
From: Haymarket VA
18 Degree overlap - surging
I'm running a cam with 18 degrees of overlap on a 110 lsa and I have some surging between 1500 and 2000 RPM. Is it realistic to expect that an SD tune can get rid of this?
Other than this area the car idles well and runs very strong.
BTW: This is a 402 w' 12:1SCR 8.8:1 DCR with L92 heads
Other than this area the car idles well and runs very strong.
BTW: This is a 402 w' 12:1SCR 8.8:1 DCR with L92 heads
Last edited by WKMCD; Jan 10, 2007 at 09:18 PM.
Racer
Joined: Jul 2003
Posts: 250
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From: Tampa Florida
I've been having the same problem with my cam profile (.570/.570 @ 239 Intake / 251 Exhaust @ 8 Degrees Separation). There were several hits in the forum concerning an air leak between the MAF and Throttle Body. I did find a trouble area on my Carbon Fiber bridge and working on it helped a little bit but still can't cruise at 60mph. It starts getting tempermental around 55 and is bad through 63. I'd be interested in any lessons you learn here. I've got LS1 Edit and a Predator but not particularly good with LS1 and their support sucks royaly.
Good Luck!
Good Luck!
Racer
Joined: Jul 2003
Posts: 250
Likes: 0
From: Tampa Florida
Thread Starter
Race Director
Joined: Dec 2004
Posts: 13,760
Likes: 75
From: Haymarket VA
My current cam actually has 19 degrees of overlap. Several very good tuners have worked on it and it's gotten better but still not acceptable for how I want to use the car.
Plan B: New cam = 13 degrees of overlap installed with CNC'd Stage 2 L92 heads to replace the current stock L92 heads. We're also dropping the compression from 12:1 to 11.5:1 so we can run a little more timing up top.
Plan B: New cam = 13 degrees of overlap installed with CNC'd Stage 2 L92 heads to replace the current stock L92 heads. We're also dropping the compression from 12:1 to 11.5:1 so we can run a little more timing up top.
Advanced
Joined: Jan 2005
Posts: 51
Likes: 0
From: Charleston SC
surging is overfueling. overfueling will happen when you haven't tuned VE table correctly, or your injector information/flow is wrong. MAF should take care of it, but the moment you change the airpath, the MAF calibration changes as well and if not accounted for properly, ends up giving you wrong data, forcing the computer to miscalculate every single fuel decision.
what you're describing here is a pure example of bad tuning.
i've tuned idle on a Trex and MS4 over email and was able to get better results than cars that i've seen gone through _three_ different 'reputable' tuners. it's not easy, but it's doable, most pros just dont take the time, because it takes way too much time to get it done right.
what you're describing here is a pure example of bad tuning.
i've tuned idle on a Trex and MS4 over email and was able to get better results than cars that i've seen gone through _three_ different 'reputable' tuners. it's not easy, but it's doable, most pros just dont take the time, because it takes way too much time to get it done right.
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Thread Starter
Race Director
Joined: Dec 2004
Posts: 13,760
Likes: 75
From: Haymarket VA
surging is overfueling. overfueling will happen when you haven't tuned VE table correctly, or your injector information/flow is wrong. MAF should take care of it, but the moment you change the airpath, the MAF calibration changes as well and if not accounted for properly, ends up giving you wrong data, forcing the computer to miscalculate every single fuel decision.
what you're describing here is a pure example of bad tuning.
i've tuned idle on a Trex and MS4 over email and was able to get better results than cars that i've seen gone through _three_ different 'reputable' tuners. it's not easy, but it's doable, most pros just dont take the time, because it takes way too much time to get it done right.
what you're describing here is a pure example of bad tuning.
i've tuned idle on a Trex and MS4 over email and was able to get better results than cars that i've seen gone through _three_ different 'reputable' tuners. it's not easy, but it's doable, most pros just dont take the time, because it takes way too much time to get it done right.
Redhardsupra, I've read your tuning posts on the other forum and I know you've done some incredible tuning. I wish you were closer.
Advanced
Joined: Jan 2005
Posts: 51
Likes: 0
From: Charleston SC
The cars idles perfectly with the current 110lsa cam. It's the low/very slight throttle driving that's the problem. I get a "fluttering" in that area.
Redhardsupra, I've read your tuning posts on the other forum and I know you've done some incredible tuning. I wish you were closer.
Redhardsupra, I've read your tuning posts on the other forum and I know you've done some incredible tuning. I wish you were closer.
