Well that's weird that you picked up 8 mph from that alone. That's equivalent to picking up 60 horsepower from a better 60". Trap speed indicates power more than the et. The car had 11's in it w/ that 120 mph trap regardless.... I really need to see that time slip to believe that. I just don't understand how a car can gain 8 mph in speed without any other mods, just lowering the 60' by .4".
Are you sure you weren't running in worse da and than it became cooler at night and better da? Honestly 8 mph is a lot for only .4 second difference in the 60"... 8mph is alot in general. I've never seen that happen before. I've always seen the opposite... that the more spin=more trap speed.
As an example in the 1/8th mile my friend has a t/i/e 5.0 and his best time is a [email protected]
86 mph w/ a 2.2 60". One run he spun through all of first and into second... ran a [email protected]
89 mph w/ a 2.5 60".
I've never really seen the mph drop because of a bad 60"... I know the et is greatly affected by the 60". That will change significantly, but the mph stays pretty constant. Trap speed normally indicates horsepower.... and you gaining 8 mph in trap speed seems very hard to believe.
As I mentioned in my previous post, this was an extreme example. There's no doubt air density played part of the role in my example/situation, but even still it's not the first time I've seen a car trap lower with a worse 60', nor would I say it's uncommon.
We often hear that trap speeds will go up if you're spinning. This does happen and true to an extent. What we don't hear often is, what's considered spinning? At what point does traction loss become too excessive?
What I've found from personal experience is most cars cutting 1.7-1.9 60's usually
trap their highest MPH. The same car usually
traps lower with killer 1.4 or 1.5 60's and lower again with higher 2.2+ 60's. Again, this is personal experience, not factual or accurate for every car.
A 2.5 second 60' is excessive if the car was losing traction. With that much wheel spin, the car never had enough time to accelerate itself to a normal trap speed. This was true for every 2.5 60' I've seen or can think of.
Unfortunately, I never kept the 12 second time slips I got at the track. I still have the 11.4 @ 128mph one, but there's not point to showing it without the 12.2 @ 120mph pass.
I don't mean to cause an argument by any means, I just want to share some information that helps explain the OP's experience. I also want to stress that I'm not ruling out any minor adjustments needed to the OP's tune either. Which is why I'm assisting him with datalog info and any additional Bama support needed.