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Old 07-26-2010, 11:43 PM   #1 (permalink)
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Ney guy with a Different goal in mind.

I dont really care about gaining Miles per gallon and such. As i own a 1990 Mazda rx7 gtu, it already has a low Cd, but as my goals with this car are to go 200 mph on salt, i will do what it takes to make the body as slippery as possible.

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Old 07-27-2010, 12:54 AM   #2 (permalink)
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boatail, blocks, dam, underbelly pan, pizza pan wheels & hubcaps, fender skirts (of the right type)

All this stuff is simple on paper, harder to impliment in real life.

The near ideal shape is a teardrop

Good Luck
Ryan
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Old 07-27-2010, 01:15 AM   #3 (permalink)
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yah. the thing is, mazda already implements a lot of this stuff im reality. my Cd is currently about .33 however the Aero model of the early years have a Cd of .29. yup. same as a prius.
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Old 07-27-2010, 01:22 AM   #4 (permalink)
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Quote:
Originally Posted by Drcygnus View Post
yah. the thing is, mazda already implements a lot of this stuff im reality. my Cd is currently about .33 however the Aero model of the early years have a Cd of .29. yup. same as a prius.
.33 aint great, you want to be under .20 if you can be, a good look at the aero honda with a full boattail should enlighten you a bit.
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Old 07-27-2010, 08:40 AM   #5 (permalink)
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Quote:
Originally Posted by Drcygnus View Post
yah. the thing is, mazda already implements a lot of this stuff im reality. my Cd is currently about .33 however the Aero model of the early years have a Cd of .29. yup. same as a prius.
Yeah, .33 isn't that good at all. The advantage you have is a smaller frontal area so your CdA is going to be lower than most even though your Cd isn't that amazing. rmay635703's suggestions are good ones.

Also, you state the .29 is the Prius' Cd. That is the Cd of a Prius, but its the Cd of a first gen Prius, by far the most unaerodynamic of the Prius generations. The 2nd gen has a Cd of .26, and the current 3rd gen has a Cd of .25. I agree with rmay635703 that you'll need to get a lot lower unless you have tons of horsepower to plow through the air with.
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Old 07-27-2010, 08:55 AM   #6 (permalink)
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First of all, let me welcome you to the ecomodder forum. Our goals of improving fuel economy by changing our driving style(s) and aero modifications are only a little off from your goal of 200+ mph on the salt flats. We both are looking for vastly improved effieicency from the vehicles we have chosen to work with. We both want to use the least amount of horsepower for our targeted speed, because as the saying goes: "going fast costs money, how much do you want to spend."

Look at some of the aero mods here on the site and see what works for you. Road test the modifications and do share your results. Though our results may not seem as dramatic as yours (because of how fast each of us are going when we test the improvements), we may be able to learn from one another and IMHO that is why we exist.
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Old 07-27-2010, 09:16 AM   #7 (permalink)
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ah. i am already learning.

i guess i should name some of my modifications to the car.

I have a high compression mazda 13b rotary engine from a series 4 turbo car with series 4 non turbo compression rotors.
a series5 hybrid turbo
550cc proimary fuel injectors with 1600cc seccondary injectors.
Haltech e6x
400cc Water injection preturbo
complete Braided and AN fitted fuel system.
and some other odds and ends.

so far i am making about 250 wheel horse power. while this was good enough to get me into the 140 mph range at the miami mile, i feel i could get slightly better.
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Old 07-27-2010, 09:22 AM   #8 (permalink)
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The more successful salt flats cars use a "cooling" system that just stores your engine heat in a massive tank of water until the end of the run, because radiators have very high aerodynamic drag. Seal up the grille, seal up the underbody, in addition to rmay's suggestions.

A former coworker of mine is a Wankel enthusiast who wanted to buy a Honda Insight body for racing. It's 1835lbs before you strip out the hybrid powertrain (and sell it on EcoModder!), has 20ft² frontal area, and starts with Cd=0.25. I have no idea if it could be made stable at 200mph.
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Old 07-27-2010, 09:23 AM   #9 (permalink)
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can i also say that while factory mpg is horrid 17/20, that i get better miles per gallon just by having a different tune in cruise. while Mazda has i guess a stoichiometric Afr while in closed loop mode, i cruise at about 13:1 as this provides better off boost res response. i know i can get this much much much leaner durring cruise and change the timing some, it does not affect the miles per gallon much.
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Old 07-27-2010, 09:32 AM   #10 (permalink)
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Quote:
Originally Posted by RobertSmalls View Post
The more successful salt flats cars use a "cooling" system that just stores your engine heat in a massive tank of water until the end of the run, because radiators have very high aerodynamic drag. Seal up the grille, seal up the underbody, in addition to rmay's suggestions.
it all depends on what radiator you are talking about. intercooling, then yes. they do store the heat somewheres else. however the fact is that we need tremendous amount of cooling (largest factory fitted oil coolers) it is key that we have at least a radiator or two to cool things down. steady high rpm runs will kill an engine quick as it produces the most heat in this rpm range.

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