Tune time?
Moderator: John_Heard
Tune time?
I have a tune up question that i think i know the answer but i want to get some others thoughts.
small block chevy was running 12.89-12.91 but had a little pop (back fire?) in the burnout box so i assumed it was a little retarded on the timing so i bumped the timing up (advanced) 4deg.
the next run it went 13.004. the next run it went 13.01. the adjusted altitude was getting higher each run.
so was i leaning it out by advanceing the timing? was the pop not a timing problem to begin but a lean condition?
should i have went up on the jet size and left the timing? or go up a couple sizes on the jets and advance the timing too?
What would you do?
small block chevy was running 12.89-12.91 but had a little pop (back fire?) in the burnout box so i assumed it was a little retarded on the timing so i bumped the timing up (advanced) 4deg.
the next run it went 13.004. the next run it went 13.01. the adjusted altitude was getting higher each run.
so was i leaning it out by advanceing the timing? was the pop not a timing problem to begin but a lean condition?
should i have went up on the jet size and left the timing? or go up a couple sizes on the jets and advance the timing too?
What would you do?
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Re: Tune time?
What is the rest of the tune and combo?
Do you have a wideband? If so what were the AF's?
Do you pics of the plugs after the pass?
Do you have a wideband? If so what were the AF's?
Do you pics of the plugs after the pass?
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Re: Tune time?
First off change only one thing at a time. Too many changes at one time will confuse you and make it hard to tell what change affected it.
In my opinion the pop in the burnout means little. The Motor has no load on it there for it may have been just a pop. If it's doing it elsewere I would be more concerned about it.
In my opinion the pop in the burnout means little. The Motor has no load on it there for it may have been just a pop. If it's doing it elsewere I would be more concerned about it.
Blackhoodmafia!!!!
1972 Nova SS
572 C.I. BBC
Best to date: 1/8
et: 5.28
mph: 134
new wt. 3340 lbs
1972 Nova SS
572 C.I. BBC
Best to date: 1/8
et: 5.28
mph: 134
new wt. 3340 lbs
Re: Tune time?
I dont have the other number!
Yeah it's just in the burnout box from a idle. I think it could be the idle mixture or maybe a diaphram or too small of squirter?
It seems to run down the track good no missing or popping.
I was just a little confused as to why it ran slower after advancing the timing?
Yeah it's just in the burnout box from a idle. I think it could be the idle mixture or maybe a diaphram or too small of squirter?
It seems to run down the track good no missing or popping.
I was just a little confused as to why it ran slower after advancing the timing?
Re: Tune time?
I was told to jet up until your speed falls off and then back off a jet size - that's the Farmer John way of figuring out rich/lean, in addition to reading plugs.
My issue with reading plugs is that unless I'm able to stop and pull them when I hit the return road I can't tell much from them. By the time I'm back to the trailer they'll have changed color...
My issue with reading plugs is that unless I'm able to stop and pull them when I hit the return road I can't tell much from them. By the time I'm back to the trailer they'll have changed color...
1969 ProStreet Camaro RS Best 9.75@139 1.46 60'
Blown 427 BBC, TH400 w/Brake, Back-Half Ladderbar
Narrowed 12-Bolt, 4.10 Gears, Spool, Moser 33 Spline
http://www.marsh-racing.com/harrys_camaro-1.htm
Blown 427 BBC, TH400 w/Brake, Back-Half Ladderbar
Narrowed 12-Bolt, 4.10 Gears, Spool, Moser 33 Spline
http://www.marsh-racing.com/harrys_camaro-1.htm
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Re: Tune time?
Too much advance can get the flame started too soon and you will lose hp.Speedster wrote:I dont have the other number!
Yeah it's just in the burnout box from a idle. I think it could be the idle mixture or maybe a diaphram or too small of squirter?
It seems to run down the track good no missing or popping.
I was just a little confused as to why it ran slower after advancing the timing?
CDR PERFORMANCE
The Custom Engine Shop
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The Custom Engine Shop
Dart - Callies - BRC - Oliver - BME - Custom Cams - T&D - Trend - JGS - BorgWarner - SuperNatural - EV - CSU - C&S - BS3
http://www.cdrperformance.biz
- CDR Performance
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Re: Tune time?
You guy got to invest in a Wideband. The AF meters are the only way to tune (plus plug reading). If we had affordable handheld Widebands 20+ years ago we would have sooooooooooo much faster then and today.wikd69 wrote:I was told to jet up until your speed falls off and then back off a jet size - that's the Farmer John way of figuring out rich/lean, in addition to reading plugs.
My issue with reading plugs is that unless I'm able to stop and pull them when I hit the return road I can't tell much from them. By the time I'm back to the trailer they'll have changed color...
PLX, NGK, LM-1 Innovative are some of the W/B we use. No more guess work.
Correct, to get a good read on the plugs you need to click it off after the light and get it towed back to the pits.
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Dart - Callies - BRC - Oliver - BME - Custom Cams - T&D - Trend - JGS - BorgWarner - SuperNatural - EV - CSU - C&S - BS3
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Re: Tune time?
I have never heard of a wideband in racing? sorry im just getting back into drag racing after a 16-17 year layoff.
Things have changed a bunch.
Do you have a link to them?
Things have changed a bunch.
Do you have a link to them?
Re: Tune time?
http://www.oxygensensor.net/innovate_motorsports.phpSpeedster wrote:I have never heard of a wideband in racing? sorry im just getting back into drag racing after a 16-17 year layoff.
Things have changed a bunch.
Do you have a link to them?
We put an LC-I with DB gauge in over the winter and can't wait to get some real tuning runs.
Re: Tune time?
thanks.
we ran one of these on my kids jr dragster a couple of years ago. it was a mychron 360.
we ran one of these on my kids jr dragster a couple of years ago. it was a mychron 360.
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Re: Tune time?
The links above is to a good common wide band. The wideband use an O2 sensor (like in late model cars) to sniff the exhaust gases. 14.7 -1 is perfect at idle for a gas motor.Speedster wrote:I have never heard of a wideband in racing? sorry im just getting back into drag racing after a 16-17 year layoff.
Things have changed a bunch.
Do you have a link to them?
13.5 +/- ~ 14.7 to 1 at cruise is good.
N/A WOT 12.5 to 1 is good and
11.5 to 1 on forced induction and n2o
By being able to record AF's on pass or on the street you can tune based upon information coming directly out of the motor. Spark plugs still need to get pulled and check, as they are in the heat of the battle in the motor. The O2 sensor is placed after the motor and is only telling us about what has already happened.
EGT are good too but they are too dependent on correct timing. But they can tell you your timing is way off.........
Lots more too but I type too slow.
CDR PERFORMANCE
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The Custom Engine Shop
Dart - Callies - BRC - Oliver - BME - Custom Cams - T&D - Trend - JGS - BorgWarner - SuperNatural - EV - CSU - C&S - BS3
http://www.cdrperformance.biz
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