ET vs MPH Question

[Jerryl]

Trying to learn a few more things.
I don't want to keep bothering Dusty with my rookie questions, so here I go.

I have learned from the experts to always tune for MPH at the track first, than focus on ET's.
So, let's Ass-U-Me identical 60 ft times . . .
Does higher MPH always coorelate to quicker ET's?

Edit:
Located an awesome thread!
http://www.turbobuick.com/forums/tr...k-up-vs-non-l-u-efficiency-when-unlocked.html

 

[jasjamz]

Yes, given its a clean pass with no issues like bogging, loss of traction, or some other unusual event.

 

[Jerryl]

Yes, given its a clean pass with no issues like bogging, loss of traction, or some other unusual event.

According to the formula, you are correct, and this is my limited understanding.

So, what about the real world?
If a locked converter picks up 2-3 mph vs unlocked, does that mean the ET's will be quicker in the real world?

 

[jasjamz]

Yep, given the 60' is the same. Its like using 85% throttle vs. 100% throttle past the 1/8th. You're putting more power to the ground so it will get you there faster.

 

[yullose]

ET's are not as vulnerable in the 2nd half of the track, as they are in the first half.

The 60ft times have the largest impact on ET's, because that is time wasted trying to get moving from a dead stop. The quicker you get your sled away from the starting line, the better the overall ET will be.

I've coasted thru the traps already with a 9 sec timeslip at an unimpressive 85mph, because my car would 60ft in the 1.20's.

I've seen other cars run 11.50's @ 150+ already too... Generally stickshift turbo cars with lousy 60ft times.

MPH will always show horsepower... being it is simple math. It takes X horsepower to accelerate Y weight to Z speed in 1320ft.

If you have killer MPH but ET's don't match... then you need to work on the 60ft times.

 

[jasjamz]

ET's are not as vulnerable in the 2nd half of the track, as they are in the first half.

The 60ft times have the largest impact on ET's, because that is time wasted trying to get moving from a dead stop. The quicker you get your sled away from the starting line, the better the overall ET will be.

I've coasted thru the traps already with a 9 sec timeslip at an unimpressive 85mph, because my car would 60ft in the 1.20's.

I've seen other cars run 11.50's @ 150+ already too... Generally stickshift turbo cars with lousy 60ft times.

MPH will always show horsepower... being it is simple math. It takes X horsepower to accelerate Y weight to Z speed in 1320ft.

If you have killer MPH but ET's don't match... then you need to work on the 60ft times.

LOL! sooo..... is your answer to his original post a yes or a no...

 

[JDSfastGN]

I have to disagree. Gearing and tc efficiency/ multiplication can help or hurt a car. Mph does not =e.t. Even with the same 60 ft. Mph is hp but it may not mean a quicker e.t.

 

[jasjamz]

I have to disagree. Gearing and tc efficiency/ multiplication can help or hurt a car. Mph does not =e.t. Even with the same 60 ft. Mph is hp but it may not mean a quicker e.t.

Ok, so if two car leave at the same time, and both have a 1.60 60ft time, run all out to the finish, the car with more trap MPH will have take a longer amount of time to get to the finish line??? That does not make sense. The only way that can be logical is if a problem arises with the higher HP car during the run like a loss of traction over rev or something.

 

[JDSfastGN]

Because of gearing or maybe because one car has a stronger mid range that helps it get to a quicker 330 or 660 e.t while the other car may comeon strong in the upper rpms. For example my dads 86 in the sig has a converter that hits hard out of the hole but is very loose until it's locked up in 3 rd. So it picks up from 97 to 126 on the back half. My ptc in my car is more efficient down low but is not as efficient as a locked up converter up top. It's much easier to improve your et down in the first half of the track, while a locked up unit will pick up 27-29 mph it doesn't matter much towards the et at the end of the 1/4. In the end they have the same et with one car charging hard up top catching the car that acelerated quicker down low past the 60 ft

 

[bison]

I only agree to a certain point. Its more important to make the car work in the sub 330' if you want to have blistering e.t.'s. Your a/f could be really rich and costing you 2mph in the eighth but it still e.t. better if the 60' is .1 quicker and the 330' is .2 quicker. The first half of the track is critical. You will realize this when you are making a lot of power and let out at the eight and still roll across the line in less than 6 sec after letting out. When cars are quick its more important to look at the 330' time as an indicator of the entire pass and not just the 60'. Most quick cars have more power than they can use in the first 60'. Another thing too is that a lot of LU converters will 60' great and mph better than anything but they give up a lot of e.t. when they are unlocked in 1st and 2nd gears. If they are making a lot of power (like 800+) they will almost always e.t. better if the 330' and 660' times are quicker regardless of the mph at the quarter trap on a full pass.

 

[bison]

Ok, so if two car leave at the same time, and both have a 1.60 60ft time, run all out to the finish, the car with more trap MPH will have take a longer amount of time to get to the finish line???

It could well be that. Especially if the converter is spec'd wrong or tire height/gearing is not optimal. It could pull the engine down too hard on shifts and out of the power band. Eventually the engine will catch up and give the mph but the amount of e.t. lost while its out of the power band may not be enough to win. Its way harder to make up whats lost down low than it is to get it all down low and sacrifice some up top. The higher trap mph could mean that the car was catching the other car but didnt have enough time since they already passed the quarter mark. Ive seen plenty of cars that had same 60' but at the 330' and 660' one is substantially quicker even though the other car may quarter trap with more mph. Its actually quite common on a lot of TR's since a lot of guys are over turboed, under convertered, and under springed. 3 things all pulling at each other throughout the pass. Same thing goes for poor tune throughout the run.

 

[bison]

Gearing and tc efficiency/ multiplication can help or hurt a car. Mph does not =e.t. Even with the same 60 ft. Mph is hp but it may not mean a quicker e.t.

So true

 

[84gnguy]

ET indicates traction and MPH indicates HP

 

[bison]

ET indicates traction and MPH indicates HP

Hopefully ET indicates traction and mph

 

[Dusty Bradford]

So, let's Ass-U-Me identical 60 ft times . . .
Does higher MPH always coorelate to quicker ET's?

To directly answer the question, the answer is no.

To understand, the answers are in the 330' and 660' times as Bison has said.

When you break down a timeslip the car with the higher mph will run the 660-1320 distance a little quicker than the car with less mph. It's very common though for the car with the slower mph to run the 0-660 distance quicker than the other car and it makes up the difference.

You can have 2 cars run a 10.95 with identical 60 foot times. Once car can run 119 and the other 124. This is because the car with a lower mph ran quicker to the 1/8th mile and made up the difference.

I see this all the time with nitrous vs turbo. The nitrous car will usually out 330 the turbo car. The turbo car may run 10mph faster than the nitrous car, but the nitrous car gets there 1st.

 

[Alky V6]

I agree with no.

Generally, if you setup a car for highest mph, you're going to give up a little e.t., and vice versa.

 

[jasjamz]

Another Learning Experience....

Sorry Jerryl, guess I was wrong. Learn something new everyday. I was under the impression that If he was going to lock his converter to gain 2-3 mph but launch the car having the same 60' it would et better since the slippage would be much less. That would allow him to transfer more power to the ground and propel the car to the stripe quicker.

All of the one car may run harder in the first 660, and the nitrous car vs. turbo car examples don't really seem to fit into what Jerryl is asking. I appreciate the sharing of knowledge and experience though. Seems to me that he was trying to see if basic theory would hold true. Maybe my "if you do XXX after the eighth" or "if you take two cars" example complicated things, which I did not intend to do.:redface:

If I went from 20 to 23psi, I would expect to see a gain in MPH and quicker E.T even if I had a 1.55 60' on both runs. Am I thinking wrong here too?

 

[Alky V6]

Sorry Jerryl, guess I was wrong. Learn something new everyday. I was under the impression that If he was going to lock his converter to gain 2-3 mph but launch the car having the same 60' it would et better since the slippage would be much less. That would allow him to transfer more power to the ground and propel the car to the stripe quicker.

All of the one car may run harder in the first 660, and the nitrous car vs. turbo car examples don't really seem to fit into what Jerryl is asking. I appreciate the sharing of knowledge and experience though. Seems to me that he was trying to see if basic theory would hold true. Maybe my "if you do XXX after the eighth" or "if you take two cars" example complicated things, which I did not intend to do.:redface:

If I went from 20 to 23psi, I would expect to see a gain in MPH and quicker E.T even if I had a 1.55 60' on both runs. Am I thinking wrong here too?

I have to agree with you. If a tuning parameter (any type of tuning parameter) is changed midtrack, then your scenario is possible. If all tuning scenarios are fixed from the start, then the generalization I posted is correct.

 

[Jerryl]

Goes to show;
Never underestimate the power of reality.
Thanks to who replied.