Quarter Mile Math

Nigel

Well-Known Member
I took some points out of a power logger file of a 1/4 mile run from zero seconds to 11 seconds (that was the 1/4 ET) in 1/2 second intervals. Just goofing around, but it gives a picture of what is happening through the run.
Power is just a form of F=MA per time. So, the power actually accelerating the car is P=V*A*Mass. This is the power applied to accelerate the car forward minus aero, friction losses, and other losses. I pulled the MPH vs time from the PL, plotted in excel, and then added a polynomial trendline to the chart. Excel does the hard work, but once you have the trendline(and formula), the acceleration is the derivative, and the distance is the integral. I integrated for the distance as an accuracy check. After 11 seconds distance is 1331ft, close enough to 1320 for what I am doing.
Initially(60ft) the aero and rolling resistance is negligible, but the biggest parasitic loss is force applied in a direction other than parallel to the horizontal 1/4 mile direction i.e. the direction required to increase the speed of the car. Any rise in the body or rotation of the body, such as a wheelie, squatting, or even excessive separation of the back wheel is energy consumed and wasted. Additionally, you likely get a fair amount of loss in the torque convertor until the turbine gets to a certain rpm. That rpm will be an inherent feature of the converter design.
The aero drag force is a semi rough estimate.
I don’t know the exact HP curve of my car, but you can get an idea of what is being put to ground. The rolling friction losses are likely somewhat small and I would expect to increase with velocity squared. Ultimately, getting the HP applied curve as flat as possible and as close to the crankshaft HP as possible will net the best acceleration.
Does anybody know if the high end engine management systems offer these kinds of outputs?
Analyzing data like this could be very beneficial for doing before and after change comparisons. Turbos, converters, suspension, whatever…

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Mr.Spool

Well-Known Member
Does anybody know if the high end engine management systems offer these kinds of outputs?
Yes.
There are alot of outputs depending on which computer that show just about everything that the car is doing some of these options are wheelspeed on both front and rear.
Shock travel,converter slip behavior and well as pressure.
Rpm/ boost/turbo behavior, g force monitoring and the list goes on and on all in time increments that can be seen and matched to the distances you are running.
This info is invaluable as you can see what every peice of the car is doing and when it does it and where it does it down the track or street.
I will add that a draggy is usually within 1 tenth of the timing lights at the track
Which makes it the best low cost accurate product for the real test and tuner to get an idea of changes that can move the car In the right or wrong direction
 

dynoman

Well-Known Member
I remember when They first started monitoring wheel speed on Top Fuel cars and found that the clutch was still slipping even at the finish line . That's when they started adding more clutch pressure down track to lock it up and the speeds increased accordingly .
I always told my boys ... Knowledge is power .
 

Nigel

Well-Known Member
Yes.
There are alot of outputs depending on which computer that show just about everything that the car is doing some of these options are wheelspeed on both front and rear.
Shock travel,converter slip behavior and well as pressure.
Rpm/ boost/turbo behavior, g force monitoring and the list goes on and on all in time increments that can be seen and matched to the distances you are running.
This info is invaluable as you can see what every peice of the car is doing and when it does it and where it does it down the track or street.
I will add that a draggy is usually within 1 tenth of the timing lights at the track
Which makes it the best low cost accurate product for the real test and tuner to get an idea of changes that can move the car In the right or wrong direction
Post some charts of HP including a calculation for aerodynamic drag for the quarter.
You can log any sensor that has a 0 to 5v output at a 5 samples per second sampling rate with a powerlogger, the drawback is you only get two, other systems will take many more. You can go cheap with an innovate setup and do quite a bit, the log works software has math channels, so you may be able to do some complex stuff. The question is not about sensor logging and looking at sensor data, the question is what kind of analytical capability, if any, do the aftermarket systems have built in. A bunch of stuff is not logged it has to be calculated.
 
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Chuck Leeper

Toxic old bastard
Staff member
I've always had an interest in the electronic controls and the info available.
Some of you older guys may remember the Chevrolet Power Manuals printed many yrs ago.
I have a collection of those manuals. The one I'm looking at now is 3rd edition 1978.
These manuals have sections in them dealing with vehicle dynamics. Interesting stuff, not directly tied to drag racing, but relevant.
Would be interesting to see a system like the Dominator set up with all the bells and whistles.
Or a MoTec with such a set up. New version has an optional Logging level 3 license that has 2000 channels!
It's only money!
 

Mr.Spool

Well-Known Member
Post some charts of HP including a calculation for aerodynamic drag for the quarter.
You can log any sensor that has a 0 to 5v output at a 5 samples per second sampling rate with a powerlogger, the drawback is you only get two, other systems will take many more. You can go cheap with an innovate setup and do quite a bit, the log works software has math channels, so you may be able to do some complex stuff. The question is not about sensor logging and looking at sensor data, the question is what kind of analytical capability, if any, do the aftermarket systems have built in. A bunch of stuff is not logged it has to be calculated.

The holley will show the amount fuel used in any timeframe a person wants to look at that's how you know how much power you are making and when.
Looking at wheelspeed in the front and back and converter behavior gives you a picture of how it's being applied.
It's not a chart it's a graph and has number specific info as well.
The amount of inputs is vital and is the reason for upgrading the computer along with the ability to run a much faster wideband o2 sensor.
 

Mr.Spool

Well-Known Member
I've always had an interest in the electronic controls and the info available.
Some of you older guys may remember the Chevrolet Power Manuals printed many yrs ago.
I have a collection of those manuals. The one I'm looking at now is 3rd edition 1978.
These manuals have sections in them dealing with vehicle dynamics. Interesting stuff, not directly tied to drag racing, but relevant.
Would be interesting to see a system like the Dominator set up with all the bells and whistles.
Or a MoTec with such a set up. New version has an optional Logging level 3 license that has 2000 channels!
It's only money!
There are several cars up here running the dominator with every input being used the info is graphed out and you can see everything the car does and the level of correction is awesome
 

Mr.Spool

Well-Known Member
A bunch of stuff is not logged it has to be calculated
So just in case my response wasnt what you are looking for
Is the question if someone doesnt have the computer and the many inputs to see all the data how can it be done without?
 

Nigel

Well-Known Member
Every data logger has a sampling rate limit, including the ones you are using, it can't be any time interval you want.
How did you verify the brake specific fuel consumption to calculate power.
A graph and a chart are the same thing, post the graph (chart) I asked for. It is calculated.
 

Mr.Spool

Well-Known Member
Every data logger has a sampling rate limit, including the ones you are using, it can't be any time interval you want.
How did you verify the brake specific fuel consumption to calculate power.
A graph and a chart are the same thing, post the graph (chart) I asked for. It is calculated.
Sure it can
Its a complete down to millisecond record of the entire run of all the sensors that you have hooked up.
If you have seen a log from a holley you can see the fuel consumption.
As far a log I'm not going to post that kind of information on the web.
We do look at the timeslips (et and mph) and we know what the cars weight.
Wallace racing calculators is another good tool to look at things if you have numbers off a draggy or track you plug them in and have a good time playing with slip numbers and g force and mph off different distances.
As far as aero drag goes depending on how fast the car will go the focus is downforce.
 

Nigel

Well-Known Member
Sure it can
Its a complete down to millisecond record of the entire run of all the sensors that you have hooked up.
If you have seen a log from a holley you can see the fuel consumption.
As far a log I'm not going to post that kind of information on the web.
We do look at the timeslips (et and mph) and we know what the cars weight.
Wallace racing calculators is another good tool to look at things if you have numbers off a draggy or track you plug them in and have a good time playing with slip numbers and g force and mph off different distances.
As far as aero drag goes depending on how fast the car will go the focus is downforce.
Every data logger has a sampling rate limit (it is an inherent equipment limitation), that is not an opinion, that is a fact. Just because you don't understand, that does not make it not so. None of them have a millisecond sample rate, and even if they did, it is still a limit, but they don't. A Holly dominator has a max sample rate of 10 milliseconds.
Wallace racing calculators and dragy do not provide close to what I posted above.
The focus of this thread is what I posted, and apparently you said yes with zero understanding of what I posted. I posted information that people may find interesting and may want to have a real discussion and an open back and forth, and I asked about a specific capability that aftermarket ecu software packages may or may not have.
Either post information that adds to the topic or leave it be. Don't come into my post, give a wrong/non answer, then copout and tell me the real answer is a secret.
 

TType85

Well-Known Member
Every data logger has a sampling rate limit, including the ones you are using, it can't be any time interval you want.
How did you verify the brake specific fuel consumption to calculate power.
A graph and a chart are the same thing, post the graph (chart) I asked for. It is calculated.
Holley Dominator/HP is adjustable from 1-100 samples per second (10ms), from all sensor at one time.

You can set up something like 47 extra inputs on the dominator (HP is only 8) depending on what you want to log. You can use any of that data in the math channels. The log viewer allows up to 10 math channels but if you need more or more complex calculations all the data can be exported to csv.

I have a couple of math channels set up but If you know the formulas you can set up to 10 of them in the Holley log viewer. Everything I have seen people are just using the rule-of-thumb bsfc for calculations (.6 for gas, .81 for E85)

Unfortunately my laptop that had any useful logs crashed but this is from when I was just getting it set up with the new combo on 91 octane and had the boost at 11psi max and tps was only reading 85% max. Car is mild built motor with cnc ported heads, 4-bolt headers, 6766 .81 a/r, and 120lb injectors. 300hp at the crank with 11psi seems to be a reasonable estimate.

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Mr.Spool

Well-Known Member
Every data logger has a sampling rate limit (it is an inherent equipment limitation), that is not an opinion, that is a fact. Just because you don't understand, that does not make it not so. None of them have a millisecond sample rate, and even if they did, it is still a limit, but they don't. A Holly dominator has a max sample rate of 10 milliseconds.
Wallace racing calculators and dragy do not provide close to what I posted above.
The focus of this thread is what I posted, and apparently you said yes with zero understanding of what I posted. I posted information that people may find interesting and may want to have a real discussion and an open back and forth, and I asked about a specific capability that aftermarket ecu software packages may or may not have.
Either post information that adds to the topic or leave it be. Don't come into my post, give a wrong/non answer, then copout and tell me the real answer is a secret.
I said milliseconds and I have given plenty of info and everything I have posted is true.
It was clear to me earlier that you have never obviously seen what the Holley does and understand what actually goes on.
As usual you have an attitude and want to argue about things, try to attack me and get all upset that you think you know things you dont know about.
Nothing wrong with wallace calculator and a draggy.
For 150 bucks you could actually
know what's going on.
Look at the screenshot of the Holley and check the left hand corner
Looks like what I said is right there.
And no I'm not giving you a screenshot like above that is a secret and private business.
Don't seem like you respect that.
But I bet you will like his post though😉
 

Nigel

Well-Known Member
Holley Dominator/HP is adjustable from 1-100 samples per second (10ms), from all sensor at one time.

You can set up something like 47 extra inputs on the dominator (HP is only 8) depending on what you want to log. You can use any of that data in the math channels. The log viewer allows up to 10 math channels but if you need more or more complex calculations all the data can be exported to csv.

I have a couple of math channels set up but If you know the formulas you can set up to 10 of them in the Holley log viewer. Everything I have seen people are just using the rule-of-thumb bsfc for calculations (.6 for gas, .81 for E85)

Unfortunately my laptop that had any useful logs crashed but this is from when I was just getting it set up with the new combo on 91 octane and had the boost at 11psi max and tps was only reading 85% max. Car is mild built motor with cnc ported heads, 4-bolt headers, 6766 .81 a/r, and 120lb injectors. 300hp at the crank with 11psi seems to be a reasonable estimate.

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Good stuff. A csv would be useful for in depth calcs, but depending on the inputs the math channels may get you there. Thanks for sharing! For an Alky car, I think you would have to determine the bsfc on the dyno. That obviously gives engine crank power, the HP I posted above would essentially be the force vector applied to the CG level with the track not including rolling losses and assuming a level track. With a reasonable estimate of the rolling losses applied, you could map how much crank HP is actually making it to accelerate the car and plot it. I wish the powerlogger would export to csv, you could do quite a bit with it then.
 

Nigel

Well-Known Member
I said milliseconds and I have given plenty of info and everything I have posted is true.
It was clear to me earlier that you have never obviously seen what the Holley does and understand what actually goes on.
As usual you have an attitude and want to argue about things, try to attack me and get all upset that you think you know things you dont know about.
Nothing wrong with wallace calculator and a draggy.
For 150 bucks you could actually
know what's going on.
Look at the screenshot of the Holley and check the left hand corner
Looks like what I said is right there.
And no I'm not giving you a screenshot like above that is a secret and private business.
Don't seem like you respect that.
But I bet you will like his post though😉
Bizarre. It is real simple, don't converse with me or reply to my posts, problem solved. No emotion, I just don't like the way you conduct yourself, use your telepathic powers and crystal ball on someone else. Get over it and move on.
 

Mr.Spool

Well-Known Member
Bizarre. It is real simple, don't converse with me or reply to my posts, problem solved. No emotion, I just don't like the way you conduct yourself, use your telepathic powers and crystal ball on someone else. Get over it and move on.
You do realize you on an open forum?
This is the land of the free sir and I will post what I want when I want.
But thanks for telling me how you feel and judge me🙄
Have a good one hope your day goes better and I'm out of "your thread".
 

Nigel

Well-Known Member
I had some previous 1/4 logs with a 3021 LU converter. The car was almost identical as far as performance, I would typically be able to run 11.2s with the 3021, and I can run 11.0s with the PTC, same trap speed. You can see the difference with the power laid down between each converter and the slip of each converter. Dave's 3021 is an excellent converter and probably the best LU out there in my opinion. The PTC NLU is a little better at the track, but the thing I like most is its coupling and low slip. Not for the performance, but the car shifts right around 5k rpm consistently (stock governor) and would trap 400 rpm lower. I don't have anything special for a valve train, TA stock style heavy-duty rockers, small cam, and prefer to keep the rpm lower. Between that and the small turbo, and I really like the way it drives. It looks like the slip of the 3021 does not really hurt the 1/4 performance on the back end, the advantage of the PTC looks to be mainly in the 330, at least for my example.

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