My new way of measuring on-road drag

[California98Civic]

Originally Posted by freebeard

... All I was saying was that that Template is not always fit for purpose.

That seems right to my differently-trained eye. Coming from a different field, I think of the Template as theory, which means it was derived from empirical research in a specific domain. Those findings inform a model, which everyone should know from the start is both useful and limited. It is fit for some purposes and not others. But aknowledging that a theory is limited--as all research is--is not the same as blanket dismissal.

The throttle stop testing method is smart. However, during any given testing effort wind, tire temp, ambient temp, road temp, reliability of the throttle stop material, drivetrain temp, accuracy of your GPS, and alternator charging will all still be variables. Several of those factors are not factors in a 50 mph to 0 mph coast down test. These are different methods, useful for different things and conditions.

[JulianEdgar]

Originally Posted by j-c-c

I didn't see enough info in the the video to agree with the stated conclusion of the test.

For example, the strakes seemed to have much wider spacing then is the norm, I am not convinced measuring pressure at a single point is reliable to ascertain what I think is really happening with the entire system, which is the goal (?), rather then a single point, and the two PW taped squares purpose was not explained. My assumption, they were the bases that held the strakes being tested, so they had an unknown thickness, and they likely disrupted the under airflow, like a spoiler would, and to what to degree, I don't know, but a test with no strakes and PW only, would have resolved that question, for that single point of air pressure test measurement.

You may well be right - and of course you can do some testing and make your own measurements. I don't have a monopoly on testing and posting results!

[JulianEdgar]

Originally Posted by California98Civic

The throttle stop testing method is smart. However, during any given testing effort wind, tire temp, ambient temp, road temp, reliability of the throttle stop material, drivetrain temp, accuracy of your GPS, and alternator charging will all still be variables. Several of those factors are not factors in a 50 mph to 0 mph coast down test. These are different methods, useful for different things and conditions.

Two things.

1. I have tried both methods, and I don't think you have. So I am speaking from experience, and I don't think you are.

2. One good way assessing the quality of a testing methodology is to make a change that gives a known outcome, and see how the test outcome reflects that change. Like, open/closed windows. I couldn't see any difference with coast-down testing; I can certainly see a difference with throttle-stop testing.

[California98Civic]

Originally Posted by JulianEdgar

... I have tried both methods, and I don't think you have. So I am speaking from experience, and I don't think you are. ...

That's an ad hominem argument, and it does not change the fact that the variables apply.

[JulianEdgar]

Originally Posted by California98Civic

That's an ad hominem argument, and it does not change the fact that the variables apply.

No it is definitely NOT an ad hominem argument; it is a simple statement of fact. You are talking about something you've not done, so you have no direct experience in how repeatable it is, how the results correlate to changes, etc.

[JulianEdgar]

I just did a good throttle-stop testing session. Ideal conditions - 13 degrees C, no wind, 30 per cent throttle. To give some idea of the consistency that is achievable, I did three tests of the car in its standard configuration (ie with undertrays and rear wing). One at the beginning, one at the middle and one at the end of the 40 minute test session. The results (km/h) were:

• 103
• 104
• 104

I am therefore using an average of 103.5 km/h as the reference.

Results of testing were:

• No rear spats - 104
• Vertical front winglets 40mm gap - 103.5
• Vertical front winglets 20mm gap - 105
• Edgarwit front air curtains 40mm gap - 106
• Edgarwit front air curtains 20mm gap - 107.5
• Rear vertical spoiler lip 35mm - 102.5
• Windows open - 101

[freebeard]

The alternative to straight strakes is to have them splayed.



It may not show at this angle (never saw the car again) but the fences inside the wheels are angled outward the width of the tires. This example is sized to the max of the class racing rules. I can see it doing triple duty:

separate wheelwell and underbody flow
diverging duct for the underbody
open-sided wheel spat

[California98Civic]

Originally Posted by JulianEdgar

No it is definitely NOT an ad hominem argument; it is a simple statement of fact. You are talking about something you've not done, so you have no direct experience in how repeatable it is, how the results correlate to changes, etc.

You seem to think I am arguing it is not a good method because I am pointing out how variables still apply. I've already told you I like what you've done here, and I plan to try it. But whether I have or do has no bearing on the relevance of variables, and anyone who wants to try what you are suggesting should think about them.

Originally Posted by JulianEdgar

I just did a good throttle-stop testing session. Ideal conditions - 13 degrees C, no wind, 30 per cent throttle. To give some idea of the consistency that is achievable, I did three tests of the car in its standard configuration (ie with undertrays and rear wing). One at the beginning, one at the middle and one at the end of the 40 minute test session. The results (km/h) were:

• 103
• 104
• 104

I am therefore using an average of 103.5 km/h as the reference.

Results of testing were:

• No rear spats - 104
• Vertical front winglets 40mm gap - 103.5
• Vertical front winglets 20mm gap - 105
• Edgarwit front air curtains 40mm gap - 106
• Edgarwit front air curtains 20mm gap - 107.5
• Rear vertical spoiler lip 35mm - 102.5
• Windows open - 101

Sounds great. I'm reticent to ask you any question, though, or try to discuss any of this, because you seem to get defensive. You seem uninterested in conversation. So good luck. I'll be curious what you come up with.

[2000mc]

Originally Posted by JulianEdgar

I just did a good throttle-stop testing session. Ideal conditions - 13 degrees C, no wind, 30 per cent throttle. To give some idea of the consistency that is achievable, I did three tests of the car in its standard configuration (ie with undertrays and rear wing). One at the beginning, one at the middle and one at the end of the 40 minute test session. The results (km/h) were:

• 103
• 104
• 104

I am therefore using an average of 103.5 km/h as the reference.

Results of testing were:

• No rear spats - 104
• Vertical front winglets 40mm gap - 103.5
• Vertical front winglets 20mm gap - 105
• Edgarwit front air curtains 40mm gap - 106
• Edgarwit front air curtains 20mm gap - 107.5
• Rear vertical spoiler lip 35mm - 102.5
• Windows open - 101

Have you tried testing with a scangauge or other similar device? Measuring to .1mpg should give you around 7x the resolution for an insight vs kmph.
When i tried testing wheel covers my results kept trending upwards, which I think would have been lost along with any result, if not for greater resolution. https://ecomodder.com/forum/showthre...tml#post418212
Do you have thoughts as to why in this more recent test, windows down produced 101kmph from a baseline of 103.5, while in an earlier video showed 98 from a baseline of 104?

[JulianEdgar]

Originally Posted by California98Civic

You seem to think I am arguing it is not a good method because I am pointing out how variables still apply. I've already told you I like what you've done here, and I plan to try it. But whether I have or do has no bearing on the relevance of variables, and anyone who wants to try what you are suggesting should think about them.



Sounds great. I'm reticent to ask you any question, though, or try to discuss any of this, because you seem to get defensive. You seem uninterested in conversation. So good luck. I'll be curious what you come up with.

I am always a bit irritated by the 'I haven't done it, but here's all the problems I think it will have' type of post. Do it, and then we can have a discussion about what really happens, not what you think might happen.