I am currently writing an application for end-of-line quality control testing for a
BUS manufacturer that will use a dynamometer and the vehicle's control interface.

One of the tests that we need to perform is determining the actual downshift speeds of The vehicle.

So the first step was to search the Internet for anything regarding shift points that's When I came upon the following WEB site:
http://integra.vtec.net/geeser/shift_points.html

I saw from a spreadsheet that the a shift point at a particular RPM and Torque I believe is calculated as follows:

(keep in mind that I am only a programmer with absolutely no automotive experience Whatsoever!!!)

Shift = RPM / (Final Drive Ratio * Gear Ratio For 1st Gear) * 60 *
((Tire Diameter*Pi())/63360)

When I go to calculate the Shift points the only information that I
will have access to are the Engine RPM and the Dyno Speed (MPH) at each
second of the test.

So the question that I have then is how would I calculate the shift points
knowing the Engine RPM and the Dyno Speed (MPH) at each second of the test??????

Thank You

Gary

 

Gary, I've been cruising this site today on my day off (while at work), and since I'm feeling a bit guilty about that I figured I'd see if I can lend a hand (since the topic is closely associated with what I should be doing anyway).

I've read your post a few times and still haven't figured out exactly what you're trying to accomplish/quantify.
For instance, .. downshift speed(s). Is that the wheel (vehicle) speed at which downshifts are to be performed, or are you referring to the amount of time it takes to do the dowmshift?
Why are YOU determining the shift points? Especially if the vehicle's control interface (engine/transmission controller('s)) operating parameters have already been established. I would imagine QC would be more of a verification procedure?
I'm sorry I may not have been much help at the moment, but as you can see I'm not quite sure what you're trying to do. ed

 

Thank You Very much for your reply


I believe I am concerned with the wheel (vehicle) speed at which the downshifts occur.

The application that I am trying to write has associated with each vehicle a set of test parameters where the user can specify the number of shift points and the minimum and maximum speed values (MPH) for each shift point.

The way the application works for a down shift check is as follows:

“The operator will be prompted to operate the vehicle at full throttle, while the dynamometer slowly decelerates (at a configurable rate) the vehicle down to a speed whereat the transmission should downshift into the lowest gear to be tested. Using data acquired during this lug-down, the application will attempt to determine the actual downshift speed(s) or the vehicle.”

As I am running this test I start collecting the engine-RPM and the dyno-MPH at each second of the test from the top speed to the bottom speed.

If the vehicle has an ECM interface then I think I can query it to determine if a shift point has occurred and at what speed it has occurred. If the vehicle does not have an ECM interface then it is a lot more difficult to determine the shift points.

So the question is then how would I determine the shift point for a vehicle with no ECM interface knowing the engine RPM and the dyno MPH at each second of the test from the top speed to the bottom speed?

I am looking for some kind of equation that uses the engine RPM the dyno RPM and the time to calculate the shift points.

Thank You

Gary

 

As I understand your question, you are dealing with a slighlty different problem then Geeser's page.. Geeser was looking for max acceleration, not day-to-day running. As such the best gear to be in was _always_ the LOWEST gear you could be in without over-revving the engine in the case of the Integra dyno plot.

More generally, you have a torque conversion and an engine rpm to vehicle mph conversion for each gear, and you have a torque/rpm plot. For any particular mph point, you may have several rpm/gear selections available, and for max acceleration, you always choose the rpm/gear combination that results in the highest torque (after applying that gear's torque conversion to that rpm's torque value).

This all amounts only to WOT conditions.. fuel economy of other conditions complicates other analyses..

does this answer the question, or am I missing it?

I'm a bit confused by this.. let me offer definitions related to this, you correct me where I'm wrong..
You want to know at what mph point the engine transmission _actually_ downshifted, right?
Dyno RPM =~ MPH
EngineRPM/DynoRPM="some ratio"
The Dyno RPM value at which "some ratio" changes is where the shift occured..

right?

 

Thank You Very much for your reply.

"I'm a bit confused by this.. let me offer definitions related to this, you correct me where I'm wrong..
You want to know at what mph point the engine transmission _actually_ downshifted, right?"

That is correct.

After I have completed the test, I will have stored in memory The Engine RPM and the Dyno MPH (not RPM as I stated earlier, sorry about that) at each second of the test.

Each vehicle will have a set of test parameters which define the limit values for each test. For the Down Shift Test I have the following limit values

Constant Ratio Time Per Gear
Constant Ratio Tolerance Percent
Number Of Down Shifts To Check
DownShift1 Minimum DownShift Speed MPH
DownShift1 Maximum DownShift Speed MPH
DownShift2 Minimum DownShift Speed MPH
DownShift2 Maximum DownShift Speed MPH
DownShift3 Minimum DownShift Speed MPH
DownShift3 Maximum DownShift Speed MPH
DownShift4 Minimum DownShift Speed MPH
DownShift4 Maximum DownShift Speed MPH
DownShift5 Minimum DownShift Speed MPH
DownShift5 Maximum DownShift Speed MPH

"Dyno RPM =~ MPH
EngineRPM/DynoRPM="some ratio"
The Dyno RPM value at which "some ratio" changes is where the shift occured..
right?"

I am not sure what you are saying, however I think I might be seeing something here.

If I want to determine the speed at which the transmission down shifted, then I guess that I would look at the ratio of the Engine RPM to the dyno MPH ( I would have to somehow calculate the dyno RPM from dyno MPH, do you know how I would do this??), for each second of the test and where ever there is a significant change in the ratio then that is where the engine transmission downshifted.

Is that what you are telling me?
Keep in mind that I am only a programmer and not an engineer.

How would I use ‘Constant Ratio Time Per Gear’, and ‘Constant Ratio Tolerance Percent’ (The limit values defined above) to determine where the engine transmission downshifted?

Thank You

Gary

 

ok... hmm..
Constant Ratio Tolerance Percent refers to what I was talking about with "some ratio" being constant while your in a certain gear, and a change in "some ratio" meaning a change in gears. Due to tires and play in gears and just general sloppiness of the real world, "some ratio" will actually be _nearly_ constant. The Constant Ratio Tolerence Percent just tells the computer how much it can change due to slop and still be considered "constant".

dyno MPH =~ dyno RPM ...just ratio the two like you said.

That should work..

keep in mind, that this is your job, not mine.. I'm just some shmoe on a web message board trying vaguely to understand your question and give you helpful suggestions.. use your own best judgement and responsibility following my advice.. if you blow up busses, or lose your job, don't come blaming me!

That said, I am giving this info in good faith.. I just may not be understanding the whole situation..
good luck..

 

Thank You for you help on this.

I was just trying to get an good understanding before I started working with my Boss on this.

Once again

Thank You

Gary