FBO, Non-Cobrajet Intake Optimal Shift Points, A10

[markmurfie]

I reread it. It’s not any better. The first half is dead wrong and the second half is so fundamental that I wonder if you know what we’re even discussing or where the sticking point actually is.



0 and 1. What do I win? I had high school physics. I’ve been trying to move the discussion on to college level since the beginning.

You win nothing, you are wrong.

0 lbs in space.

mass of 3/4" x 1.5" x 4", but that mass could be spread out in any dimensions you wanted it to be in, so any three distances is right. Because weight is only relevant in the earths gravity frame of reference.

And no I'm not trying to muddy the waters, you don't want to talk about friction. You want to talk about a single object floating in empty space.


Dimension 0 is a point
Dimension 1 is a line
Dimension 2 is a square
Dimension 3 is a cube
Dimension 4 is a moving cube, this movement can be constant or acceleration. In acceleration it's called Time squared, but it could be any two time values multiplied together as the time spent at a constant speed could be different from the one spent accelerating. So you can not use acceleration for a mass equivalence, removing the time spent accelerating would give you a single point of acceleration, which would be a velocity. You would also not use velocity for a mass equivalence, eliminating the time at a constant speed would just be a single point in space/ time. This is because space/time is not a property of the 3rd dimension. Just like volume is not a property of the 2nd dimension, area is not one of the 1st, and length is not one of a point.
When you use mass in these equations you are reducing it down to the physical dimensions of the single object you are referring to.

A dyno measures your engines acceleration, and if you want to ignore that and incorrectly change that, go ahead keep doing it. Its like using a ruler and just subtracting 1/2", just because thats your way or you read it written in a book by someone with a PHD, it doesn't effect me. I'm just trying to tell you, you don't need to do that and you are coming up with the wrong measurements.

How do I calculate acceleration, I don't, I measure it on a dyno as horsepower. Any mass attached to the engine after that, just increases what the total energy output gets distributed to. Knowing that it is a significant amount of mass's moving amongst other mass's, appropriate gear ratios are applied to increase the leverage it has to overcome those extra frictional forces.

"Oh but, torque based ECU tuning blah blah blah", yeah it's dumb.

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[GregO]

So far we have ;
Markmurfie @ 29 posts
Engineermike @ 33 posts

Engineermike Wins by TKO.

@deanm11
Dean, all I can offer is to make absolutely 100% sure the actual crankshaft RPM matches the onboard instrumentation +/- 1% across the sweep of the RPM running range. (Or at minimum the RPM shift range)
Do not trust that what you see on your gauges or laptop are correct until you verify the crank RPM’s. Being off even a few hundred RPM’s cost lost power = extra time getting to the traps.
I’ve seen this where shaved ice speed run guys are left scratching their heads searching for MPH.
Verifying and validating “Crank RPM’s” to “Display RPM’s” especially in the area of the peak power band is mandatory.
This is splitting hairs to the laymen Hot Rodded but it’s a key tool to anyone looking to put someone back on the trailer !!!

 

[markmurfie]

https://media.wired.com/photos/5bc7...er/w_1600,c_limit/acceleratingspringscale.gif



acceleration opposite of gravity.
mass as a unit from a scale goes to 0.
with mass as a 0 the opposite acceleration is removed.
gravity * 0 mass = 0 weight
Yet gravity still acts on the mass returning its weight once all motion stops.

There is no mass equivalent you get from different accelerations.
Mass is the 3 physical dimensions the object occupies, not including the 4th, space/ time.

Moment of inertia is the same.

If anything the non rotating mass equivalent of rotating mass is equal. Shocking moment of inertia does not change. Angular momentum increases with increased RPM, perpendicular to rotation not parallel to it. you know what is parallel to it? Frictional forces.

 

[WildHorse]

Mass does not affect acceleration

True when speaking of acceleration due to only gravity.

 

[markmurfie]

True when speaking of acceleration due to only gravity.

Acceleration from gravity, is the same as acceleration in a vehicle. You feel it as getting pushed back in your seat. your weight increase as you have both gravity and the cars acceleration acting on you, the total force is just diagonal and opposite of direction of travel not straight down. Stop accelerating and your weight returns to normal you are just at a higher speed.

Acceleration is also not just a change in speed. A change in direction is an acceleration. You feel it going around a turn. Your weight again goes diagonal, just to the side instead of backwards. This would be M^2/T instead of M/T^2. That acceleration doesn't give a change in mass equivalent either.

We experience gravity as being pushed toward the center of the earth. We are under a constant acceleration.

 

[engineermike]

Good point @GregO

I have evidence that the dynojet engine rpm reads lower than actual. When I line up events going on in the log vs the dyno curve, there appears to be a 2-300 rpm offset.

This is pure speculation, but it may have something to do with span of data averaging. Basically the dynojet software would average power over some “looking-back” span of, say, 500 engine rpm. Then it timestamps it for the middle of the span. So, if actual engine rpm is 6500 when knock occurs and dynojet is averaging power from 6000-6500 rpm and stamps it 6250, creating a 250 rpm offset. The same happens when you hit the rev limiter or shift.

 

[markmurfie]

1 data point every 250RPM. IDK dyno graphs look like they have more resolution than that to me.

What about A loaded dyno holding a constant RPM? It would have to be some very small time interval based not RPM interval. Surely they use the same time interval measuring constant speed and accelerating.

I would think this difference comes from the inductive RPM pick up sensors coefficients vs the crank sensors coefficients. Like trying to get two different temp sensors to read the same temperature measuring the same thing. Different sensors, different characteristics. Which do you choose is the more accurate one? Id go with the one that polls faster.

On the dyno I'd go with its pickup ignore the cars, thats what it is using to calculate torque/ HP.

Making edits to a calibration, use the cars. Same concept as the wide bands, tune to the cars wide bands not the dynos, cause once you are off the dyno thats what the ECU is going to use.

My left shift key not working is driving me nuts.

 

[GregO]

On the dyno I'd go with its pickup ignore the cars, thats what it is using to calculate torque/ HP.

That won’t work once the engine or car is off the Dyno. All RPM readings should be verified when on the load cell. RPM corrections can then be applied or possibly recalibrated if possible.

 

[markmurfie]

That won’t work once the engine or car is off the Dyno. All RPM readings should be verified when on the load cell. RPM corrections can then be applied or possibly recalibrated if possible.

The RPM pick up for the Dyno stays with the Dyno....

Calibrated to what the cars crank sensor? Every car.... Nah. Leave the Horsepower and torque you get from the Dyno at the Dyno too it doesn't mean anything other than that exact pull in those exact conditions, and that you're engine is running well and safe.

Hypobaric climate controlled dyno room. You can really calibrate the ECU now.

 

[GregO]

The RPM pick up for the Dyno stays with the Dyno....

Calibrated to what the cars crank sensor? Every car.... Nah. Leave the Horsepower and torque you get from the Dyno at the Dyno too it doesn't mean anything other than that exact pull in those exact conditions, and that you're engine is running well and safe.

Hypobaric climate controlled dyno room. You can really calibrate the ECU now.

Yikes,
No reason to dive into the weeds with this reply.

 

[markmurfie]

Yikes,
No reason to dive into the weeds with this reply.

Don't take it personal, no hostility intended. I like civilized discussion. We are all just trying to learn.

When you don't hook it up, Dyno shows you a MPH from the wheel size. It has two RPM sensors.

 

[GregO]

Don't take it personal, no hostility intended.

We’re all good
I’m just not willing to get into the weeds over the simplicity of validating RPM reading at all data points, including the needle Tach.
It’s an easily over looked tool and 99% of people gloss over this when attempting to harness maximum power.

 

[markmurfie]

I'm still stuck on this change in moment of inertia thing. Tried to find what happens if you reduced the mass of a rotating object.

They want to build this thing about 25 miles from my house! And it's basically my variable mass flywheel idea that solves their problem.

 

[deanm11]

Good point @GregO

I have evidence that the dynojet engine rpm reads lower than actual. When I line up events going on in the log vs the dyno curve, there appears to be a 2-300 rpm offset.

This is pure speculation, but it may have something to do with span of data averaging. Basically the dynojet software would average power over some “looking-back” span of, say, 500 engine rpm. Then it timestamps it for the middle of the span. So, if actual engine rpm is 6500 when knock occurs and dynojet is averaging power from 6000-6500 rpm and stamps it 6250, creating a 250 rpm offset. The same happens when you hit the rev limiter or shift.

OP here. I've enjoyed the discussion and debate. Hopefully eventually we get some base of agreed points.. though as to my 1-2 and 2-3 shifts, all methods seem to indicate toward 7900 is optimal if I want to risk that high of an rpm.

As to the rpm signal... I have the run files from two different dynos. On one local dyno, I calculate a 7-8% "slip" at peak torque. On a more distant dyno, I only get 2%. This would seem to be the opposite of what engineermike says, as if there really is no TQ/slip, I am reporting both dynojets reading too high an rpm. I would like to know how or what I'm suppose to check and log off the dyno to get the verification GregO is suggesting. ... I log 'Engine RPM' with hptuners VCM Scanner and can evaluate how accurate the rpms seem given current gear and mph. Not sure what else I can do.

 

[markmurfie]

OP here. I've enjoyed the discussion and debate. Hopefully eventually we get some base of agreed points.. though as to my 1-2 and 2-3 shifts, all methods seem to indicate toward 7900 is optimal if I want to risk that high of an rpm.

As to the rpm signal... I have the run files from two different dynos. On one local dyno, I calculate a 7-8% "slip" at peak torque. On a more distant dyno, I only get 2%. This would seem to be the opposite of what engineermike says, as if there really is no TQ/slip, I am reporting both dynojets reading too high an rpm. I would like to know how or what I'm suppose to check and log off the dyno to get the verification GregO is suggesting. ... I log 'Engine RPM' with hptuners VCM Scanner and can evaluate how accurate the rpms seem given current gear and mph. Not sure what else I can do.

Torque converters slip even with lock up clutches. Wheel RPM and engine RPM are always going to be a little off from one another. Shift points are output shaft speed tho, so don't worry about what the Dyno says.

Output shaft, wheel speed, vehicle speed and a time stampsbin a log can give you a rough estimate of acceleration. The difference in speed over the difference in time. Or a dedicated G meter. Use that in real world conditions and base your shift points off that. I don't see a tuner being told to do this being too happy. They target an RPM, and it is what it is.

21.9 mph/s is about 1G, don't do every second intervals though, use the polling rate and convert to seconds or even right to Gs. When wheel spin happens and stops it's not accurate, but you could use a G meter.


Drivers are not requesting a torque, they are requesting a speed or acceleration, torque based ECUs are dumb.

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