Faster acceleration best mod not thought of.

[Smoothaccel]

Acceleration has two main factors given the weight of the car stays the same:
1/ Positive acceleration from torque at the wheels.
2/ Negative acceleration from air resistance, drag. Drag force squares with speed. so if you were going at 2mph and then speeded up to 4mph the drag force would go up by 4 times.

Now I am assuming that one aspec of the NSX fast acceleration with its relitavely low torque engine is due to it's low drag. I don't know how the drag compares to other cars but if NSXtasy or someone could help me here, I could be sure. I did not take into consideration for acceleration, the NSX's long torque curve and its advantageous gearing.

Now,

 

[Smoothaccel]

I was not done with that!!!
Now, drag is a function of the vehicle's cross sectional area and it's Cx or Cd(shape/characteristics of car). I dont know what is the Cx or Cd for the NSX. Is there some way to reduce these things? Not sure yet what the downforce of this car plays with the .Cd. Something I will look into.

 

[Jimbo]

Practically speaking aerodynamic drag has little effect on acceleration at normal speeds (i.e. less than 100 mph).

It's those things you did not take into consideration that are mainly responsible for acceleration. And weight too.

-Jim

PS: The Cd for the NSX is .32. The frontal area is 19.2 sq ft. The Air Drag Coefficient is .57. Could these be improved upon? Sure. Take off the exterior mirrors, change the profile of the body, etc. Honda made some improvements with the aerodynamics on the 2002 and it did increase the top speed. That's where these kind of changes are mostly felt.

------------------
1992 NSX Red/Blk 5 spd #0330
1991 NSX Blk/Blk Auto #3070 (Sold)
1974 Vette 454 4 spd Wht/Blk
1976 Honda Accord 5 spd, 3 door Blue/Blue
1977 Honda Accord - Custom - Under Construction
1986 Chevy Suburban
http://homepage.mac.com/jimanders/PhotoAlbum1.html


[This message has been edited by Jimbo (edited 23 November 2002).]

 

[nsxtasy]

Originally posted by Smoothaccel:
I was not done with that!!!

You know you can go back and edit your post, don't you? It's the second icon from the right just above the post.

 

[Smoothaccel]

Originally posted by nsxtasy:
You know you can go back and edit your post, don't you? It's the second icon from the right just above the post.

Really! Kool. I did not know that

 

[NSXPERT]

Personally, I think the biggest source of Drag friction is the underbody, make it smooth and you’ll go faster. Also wash your car, the dust and debris can cause the wind to become turbulent over the skin faster, the smoother the skin the longer the air stay laminar and the lower the Cd. I don't know if this would have a big enough effect to feel, but it gives another good reason to keep the car clean!

Aaron
NSXPERT

 

[Jimbo]

Underbody drag is important and oft overlooked. The NSX is pretty good in this regard. The underbody is fairly flat. I doubt it's the biggest source, however.

I suppose a dirty car would have a miniscule effect on drag, but I'd guess it's barely measurable.

-Jim

------------------
1992 NSX Red/Blk 5 spd #0330
1991 NSX Blk/Blk Auto #3070 (Sold)
1974 Vette 454 4 spd Wht/Blk
1976 Honda Accord 5 spd, 3 door Blue/Blue
1977 Honda Accord - Custom - Under Construction
1986 Chevy Suburban
http://homepage.mac.com/jimanders/PhotoAlbum1.html

 

[NeoNSX]

> I suppose a dirty car would have a miniscule effect on drag, but I'd guess it's barely measurable.

u shouldn't have mentioned that Jimbo... i was gonna forward this message onto a guy i know who's NSX always seems to need a wash.

...although the NSX still looks sexy even when it's dirty...

 

[ncdogdoc]

Originally posted by NSXPERT:
Personally, I think the biggest source of Drag friction is the underbody, make it smooth and you’ll go faster. Also wash your car, the dust and debris can cause the wind to become turbulent over the skin faster, the smoother the skin the longer the air stay laminar and the lower the Cd. I don't know if this would have a big enough effect to feel, but it gives another good reason to keep the car clean!

Aaron
NSXPERT

I cannot agree with the first statement more (the second one also, but more for vanity!). The front end of the NSX is an undertray waiting to happen. Look at the bottom of a 360 or a 996. It almost looks like a shrink wrap fetish going on down there.

While I believe that air management helps more with handling (downforce), it will obviously help with less drag and higher speeds.



------------------
Gary Yates
1995 Red/Tan
1992 White/Black
2002 Red and White Cooper S

 

[McAttack]

Anyone who's had an air cooled engine would know while the underbelly of the NSX is pretty flat, it's nothing compared to the old VW's or Porsche 914's.

I have been thinking if the the NSX could ever attain the elusive 200 mph mark. Best I've heard of is 193 mph. Anyone get over the 200 bar?

 

[BladesNSX]

Doesnt Science of Speed have an underbody tray mod? Infact I believe there are several mods available similar to the JGTC modifications. As for an NSX going over 200mph. I'm sure a racing NSX can do it if the gearing and earodynamics were modified. Though I don't see how any of this will help with initial acceleration...

NSXtasy??

Chris??

------------------
'91 blk/blk NSX
'96 Green Integra GSR
'02 CBR F4i Yellow/Black
Honda rules

 

[nsxtasy]

Originally posted by BladesNSX:
NSXtasy??

 

[X-TNSIV]

Originally posted by Jimbo:
The Air Drag Coefficient is .57.

isn't this figure high?

I can't recall if it was the supra or mitsu eclipse, but it was around .32

I can't imagine the NSX having a higher drag coefficient.

maybe I'm wrong.

Allen

 

[nsxtasy]

Originally posted by X-TNSIV:
isn't this figure high?

I can't recall if it was the supra or mitsu eclipse, but it was around .32

I can't imagine the NSX having a higher drag coefficient.

maybe I'm wrong.

No, you're not wrong. But re-read what Jimbo wrote:

Originally posted by Jimbo:
PS: The Cd for the NSX is .32. The frontal area is 19.2 sq ft. The Air Drag Coefficient is .57.

The Cd is the coefficient of drag, and this is what you're thinking of. It is indeed .32 as Jimbo notes.

Now, Jimbo can explain the difference between the "coefficient of drag" (Cd) and the "Air Drag Coefficient", because again,

[This message has been edited by nsxtasy (edited 25 November 2002).]

 

[tewills]

It's the 1.21 gigawatts produced by plutonium in the flux capsitor!!

 

[wilsonp]

It appears to be Cd x A according to Honda, A in m^2:
http://www.honda.ca/AcuraEng/Models/NSX/features.asp#bk03

 

[ncdogdoc]

Originally posted by BladesNSX:
Doesnt Science of Speed have an underbody tray mod? Infact I believe there are several mods available similar to the JGTC modifications. As for an NSX going over 200mph. I'm sure a racing NSX can do it if the gearing and earodynamics were modified. Though I don't see how any of this will help with initial acceleration...

NSXtasy??

Chris??

Yes, SoS does have the Taitec underbody tray, but it is designed for their nose piece and costs over a grand. I think there could be a fairly simple splitter and tray developed and reproduced for 50-70% of that. JMHO, may be eating crow once I build my own!

------------------
Gary Yates
1995 Red/Tan
1992 White/Black
2002 Red and White Cooper S

 

[Smoothaccel]

Originally posted by Jimbo:

PS: The Cd for the NSX is .32. The frontal area is 19.2 sq ft. The Air Drag Coefficient is .57

Jimbo, do you know how the Air Drag Coe of .57 compares to other cars? Looks like a high number.
Based on these numbers, I am curious how much force is exerted at 25mph and 50mph and 75 mph and...200mph. I might have to reserch my old physics book. I have read that sharp lines/corners hurts aerodynamics. The 2002 front bumper looks a lot rounder.


[This message has been edited by Smoothaccel (edited 25 November 2002).]

 

[Jimbo]

As mentioned, the Air Draf Coef (ADC) is the Cd x Area. Think of it this way... The Cd depends on the geometry. A 1:18 scale NSX should have the approximately the same Cd (although the air molecules don't scale...it's reasonably close for our purposes) as a 1:1 NSX. The ADC takes into account the actual frontal area dimensions, so a small model of a NSX will have a much smaller ADC.

To really compare cars you probably should compare Cd figures. Although, there's something to be said for smaller cars in general.

So...getting back to your question.

The NSX's Cd is .30 (2002) or .32 depending on the model. That's pretty good. The C5 Corvette is .29 (Z06 is .31). The Ferrari 360 Modena (that everyone raves about) is .335. The Boxster S is .32. The Lambo Murciélago has a so-so .33 or .36 depending on whether the side scoops are closed or open.

So, I would say the NSX is pretty darn good for a design that's several years old. Interesting side point, Honda claims they have the best Cd on their Insight... .25. Of course, the Insight has skinny tires, small engine, closed wheel wells, etc.

BTW: Aerodynamic drag forces increase with the square of the velocity.

-Jim

------------------
1992 NSX Red/Blk 5 spd #0330
1991 NSX Blk/Blk Auto #3070 (Sold)
1974 Vette 454 4 spd Wht/Blk
1976 Honda Accord 5 spd, 3 door Blue/Blue
1977 Honda Accord - Custom - Under Construction
1986 Chevy Suburban
http://homepage.mac.com/jimanders/PhotoAlbum1.html

 

[BladesNSX]

WHEW!!

Wow Jimbo...where were you when I was in college sitting at home doing my Physics (paired with Calculus)II homework scratchin' my head in frustration and looking up at all the pictures of the NSX, saying to myself "keep at it man..one day you'll have one too" only to get a C in the class

------------------
'91 blk/blk NSX
'96 Green Integra GSR
'02 CBR F4i Yellow/Black
Honda rules

 

[Jimbo]

Heh...

Well, when I was taking my Physics classes, I was driving my new 1976 Accord to college...and I would have never thought that Honda would have came so far in a mere 15 years.

-Jim

------------------
1992 NSX Red/Blk 5 spd #0330
1991 NSX Blk/Blk Auto #3070 (Sold)
1974 Vette 454 4 spd Wht/Blk
1976 Honda Accord 5 spd, 3 door Blue/Blue
1977 Honda Accord - Custom - Under Construction
1986 Chevy Suburban
http://homepage.mac.com/jimanders/PhotoAlbum1.html

 

[nsxtasy]

Originally posted by Jimbo:
As mentioned, the Air Draf Coef (ADC) is the Cd x Area.

I thought the Cd x Area is the drag. What's the difference between the ADC and the amount of drag?

 

[Lud]

Originally posted by nsxtasy:
I thought the Cd x Area is the drag. B]

No, you can't calculate drag unless you (a) have a velocity and (b) are moving through something (e.g. air). There is no drag if there is no motion, and there is no drag in a vacuum.

Drag = Cd * A * .5 * r * V^2

cd is coefficient of drag
a is frontal surface area
r is the density of the medium the object is moving through
V is velocity

See http://www.insideracingtechnology.com/tech102drag.htm

[This message has been edited by Lud (edited 27 November 2002).]

 

[Barn Man]

I have made a prototype underbody tray for the front end. It is a bit too flimsey, but hey it's a prototype right?! I made it out of aluminum. I haven't had much time to devote to it lately, so it's been on the back burner for a while. I also want to come up with an underbody kit for the rear. To do this I'd like to incorporate a SOS or other engine cover scoop and have a built in scoop in the underbody of the rear to circulate to circulate air across the motor. The only issue with this is that I'd want the air to come up from under the car not from on top and down through the engine compartment. If I can get the air to come up from the bottom, it would help create downforce on the rear by creating a slight vacuum under the rear of the car. I'd need an NSX and a day or two of free time to finish the idea and test it. Also, the NSX would have to have an engine cover with a backwards scoop on it to let the air out of engine compartment that is brought up by the lower udnerbody tray.
Barn Man....