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The Great Weight Debate


JWL

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Folks-

 

After the Nationals last year, Jeff Feit and I got to talking about power-to-weight and what the "magic bullet" is in terms of HP, TQ, and car weight. Jeff was kind enough to take the data we collected and put it into a series of spreadsheets that show some remarkable results from the event. Enjoy and thanks to Jeff for his work here.

 

Sheets are at: http://midwestai.home.comcast.net/AINationals06HPTQWT.xls

 

-JWL

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You will notice that there is an empty column (except for me) for engine displacement and EFI or Carb. If any of you are willing to fess up, it would be interesting information to add. Post it here, and I'll update the sheet.

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You will notice that there is an empty column (except for me) for engine displacement and EFI or Carb. If any of you are willing to fess up, it would be interesting information to add. Post it here, and I'll update the sheet.

 

 

I for one would VERY curious to see this

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Thanks for the data Jeff!

I ran a little statistical calculation of the different comparisons and so far have concluded that there is no statistical significance in the interaction between HP and Weight. If I have some time I'll try to adjust out some of the fliers in the data to see if it makes a difference.

 

Maybe we should add in other factors as well - age of driver, years of experience, color of paint, etc.

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I think this shows it would be scary to see what happens if they get about 350 pounds out of Spencer Sharp's car.

 

Matt you'll want to tread very lightly with your statements otherwise you really piss of Griswold.....

 

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That is indeed interesting. I'll be happy to state that the engine that left me stranded at the chicane, was a 327 ish cubic inch displacement. It's choked down like a fat man in an S&M session.

Considering my best lap and where I finished, I'd say I coin the phrase, "you must first finish before you finish (At all).

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What I find interesting is that no AI car was under 3000 pounds. The lightest 05 Mustang is Matt Erickson at 3342, what a bunch of piggies.

 

I am surprized to see no one even near 2800, much less the new 2700 weight limit. Looks like the 05 Mustangs don't even have a chance to get near 3000 pounds. Are you 05 Mustang guys carrying a lot of ballast? I know Matt Erickson has some, but his car is pretty well stripped.

 

Looks to me like the championship is still up to the driving and setup, not so much the power to weight.

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I don't know why, but I was always thinking that AI cars had 400+ HP.

I guess that must be the AIX guys.

Very nice job on the chart.

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The point of this was to illustrate a few points to current and potential competitors:

 

You don’t need a minimum weight car. There were only 2 cars under 3000… and they were at the very back. The bulk of the cars, including front-runners, were 3100+. Spencer Sharp was second fastest at 3572#. There are good reasons to run a heavier car with more HP, so the 2700# minimum isn't going to change anything.

 

You don’t need to run close to your minimum weight. Lots of cars, including front-runners, playing it safe at 100+ lbs over minimum. Jay Andrew was 163# over, Spencer was 373# over.

 

Getting the ratios dead-on isn’t critical. I used the measurement of difference in minimum weight calculated from HP and TQ as a measure of how close the ratios were. Lots of people at 100lb+ difference, which means that they are 10+ shy on either torque or HP. Robin Burnett could have 20 more ft-lb with the same minimum; Matt Erickson could have 27 more.

 

Hope everyone finds this useful/interesting. Let me know your displacement and Carb/EFI so I can fill in the chart!

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This is why I like AIX. Take a driver…a 2,700 lb 500 hp car…keep everything the same except bump it to 750 hp…and it WILL be faster.

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Don't get me wrong, this is great information, but I would not read into one fast lap per session too much. Heavier cars may not be able to string as many fast laps together like a lighter car because their tires may overcook. Traffic may not allow some cars to ever get a clean lap in, etc, etc.

 

Then again, the driver talent and car setup must be equal too.

 

But I agree Jeff, the class is working well. The cars are pretty equal, and it looks like driver talent and car setup have a lot more to do with fast lap than power to weight may. That is a very good thing.

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I find it very hard to believe anyone that is serious would leave over a hundred pounds or the equivalent power on the table. Or maybe they just made some of you think they did . . . I have always learned not to believe everything I see.

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Jeff and JWL as well as the rest of the respondees, Thanks alot, now I've got to really figure out what all this means. . .

 

This level of technical info and discourse just shows why our classes are so interesting and fun to compete within. As a bystander that has always wanted to "get into the game" and is trying to upgrade my car this winter, this stuff is very encouraging.

 

Thanks to all for your insights and good natured comments.

 

MD out

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I find it very hard to believe anyone that is serious would leave over a hundred pounds or the equivalent power on the table. Or maybe they just made some of you think they did . . . I have always learned not to believe everything I see.

 

Not sure what this is suppose to mean? I think winning nationals or finishing top five is pretty serious. I'm going to go out on a limb and say driver skill and set up, trump and few extra HP/TQ.

 

I'm not sure how the top five could have faked anything. Everyone was weighed and the top five were dyno'd. Where's the wiggle room?

 

Jeff, great info, thanks.

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*Disclaimer* I did not run this data in Minitab or statease to get any real numbers, but just looking at the graphs show a weak or no correlation in regards to anything shown. The HP-laptime graph seems to show the *most strong* (still weak) correlation and even at that, the regression line is almost horizontal.

 

The actual weight versus laptime seems to suggest an inverse relationship between weight and laptime. I think this is consistent with what Jeff is saying. If weight were really important, the regression lines for weight versus laptime and HP versus laptime would be paralell. They aren't. The *imaginary* line for weight versus LT has a much larger negative slope than the line for HP vs LT.

 

What does this mean to me? Yeah, we follow AI rules. As HP goes up , so must weight. But, in the general sense the fast guys are running with a lower HP to weight ratio.

 

My take away...No matter how hard you analyze these factors, you still have to improve driving to improve lap times.

Steve

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My take away...No matter how hard you analyze these factors, you still have to improve driving to improve lap times.

I agree. The bottom line is this is amateur racing and there is a wide range of car prep, budget and driving talent in the field. If there was greater parity in these areas, you could crunch the numbers and probably come up with some concrete findings, but American Iron is not that well-developed yet. The best drivers still win even if they may not technically have the "best" cars in every sense. However, I will say the sweet-spot seems to be a power-to-weight ratio around 3150 pounds.

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However, I will say the sweet-spot seems to be a power-to-weight ratio around 3150 pounds.

 

Those graphs are about as random as it gets; I don't know if I can agree with your conclusion. What do you mean sweet-spot?

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I find it very hard to believe anyone that is serious would leave over a hundred pounds or the equivalent power on the table.
It all depends on how confident you are in your dyno numbers. When there is a dyno at the track and you know you will be tested you have to leave yourself some room for error. Many of the guys in our region have been burned before, and now leave themselves about 100# cushion.

 

Are you confident that you will NEVER exceed your current dyno numbers?

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However, I will say the sweet-spot seems to be a power-to-weight ratio around 3150 pounds.

 

Those graphs are about as random as it gets; I don't know if I can agree with your conclusion. What do you mean sweet-spot?

What I mean is that two of the top three finishers, Andrew and Royce, weighed 3147 and 3150 respectively.

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Sorry Jeff, but those numbers are about as useful as a boil on my a## (both cheeks)

 

Those numbers can only be deemed meaningful if the level of preparation and driver skills were pretty close to all the cars listed. That was not the case, far from it.

 

I hope nobody looks at the data and makes design specs for their AI car based on that.

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