Tune time?

[Speedster]

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?

[CDR Performance]

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?

[supernova]

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.

[Speedster]

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?

[wikd69]

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...

[CDR Performance]

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?

Too much advance can get the flame started too soon and you will lose hp.

[CDR Performance]

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...

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.

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.

[Speedster]

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?

[1720]

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?

http://www.oxygensensor.net/innovate_motorsports.php

We put an LC-I with DB gauge in over the winter and can't wait to get some real tuning runs.

[Speedster]

thanks.
we ran one of these on my kids jr dragster a couple of years ago. it was a mychron 360.

[CDR Performance]

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?

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.
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.