Dropping MPH and Time

[Noclutch]

Last night at the track I was running late for the T&T portion before qualifiers and only had time for 1 pass and had to hot lap it off a 70 mile trip. Ran a 13.2 @ 103.

By the end of the night in cooler air and the car cooled down a bit I was running 13.6's @ 100.

I normally run 13.0 @ 106-7 in the same DA

60' was normal but the 1/8th was down from 8.3 @ 84 to 8.5 @ 80

Car is not missing and starts out strong. I don't see a spiking in rpm as I go down the track.

I have my suspicion what it might be but need to hear some conformation from others. I will get back when and if I work this out. Next time at the track will be late Aug but a trip to a dyno will be set up before but fixing the suspect problem should be addressed first as I don't want to waste dyno time.

 

[JeremyH]

Plugs?

 

[Noclutch]

Thanks, it could be, fuel filter is also on the short list before going to the dyno.

Just installed the 3k converter and added the DR's and was expecting a 2mph loss worst case but a .4 gain in the 1/4 over all.

Not where I should be.

 

[dragpac]

Hot weather is like the Bermuda triangle,sometimes it can't be explained.

 

[Noclutch]

Was not the weather, other cars with like set up were gaining as the night went on as is the norm, 10degree difference cooler after the first run should show a gain of at least .2 et. Went to 72F after a 82F start, not so hot. Changed the WOT fuel up and down but resulted nothing.

 

[stang72]

You don't think your new converter is acting up?

 

[808muscle]

So you have a new convertor and new drag radials.........What were you running your tires at? For my auto when I added the MT ET streets I had to air them up to 30 psi before I could get a better time. If your tires are too soft it will slow you down on the top end for sure.

 

[psfracer]

mph always drops off when the plugs need replacing. We would go through that all the time when running C16 on our blower cars.

60' would be fine, but mph would always drop off, along with ET.

Are you using pump gas? When was the last time you changed plugs? Is the car breaking up any on the big end?

To keep it simple, replace the plugs first. Easiest thing to do first.

 

[psfracer]

2nd thing I would look at is the tune and make sure the converter is locking?

Any datalogs? you could monitor the timing at WOT and see, if for some reason, the car is pulling timing out as you go down the track.