perhaps... I won't lose any sleep over it :biggrin:If you climb under the rear and actually look at it, the OEM exhaust does NOT meet up close to the Type R diffuser that well. I think you are grasping at straws giving Honda way too much credit.
Rear diffusers...let's see them!!!
- Thread starter MetalSpikeRacing
- Start date
The information you remember may have been from this page: http://world.honda.com/NSX/technology/t3.html
According to that, the little thing under the rear valence Honda referred to as a diffuser reduced the coefficient of lift at the rear by 0.002 (about 2% as much as the bigger rear wing did) and drag by 0.003. Honda didn’t state what impact any of the other aerodynamic changes had on drag only that in total, they increased the 2002 NSX-R’s drag by 0.02 compared to the standard NSX.
I agree that without a closed and preferably flat underbody in front of the diffuser, the diffuser won’t work as it should. However, if it can reduce turbulence around the muffler area, maybe it can at least reduce lift and drag somewhat for that reason alone.
There are some nice pictures in this thread, by the way!
work in progress, it's on a lift also, but here is mine =)
Well, evidently there are some on this thread that think Honda is giving themselves too much credit
If you climb under the rear and actually look at it, the OEM exhaust does NOT meet up close to the Type R diffuser that well. I think you are grasping at straws giving Honda way too much credit.
I wouldn't be so quick to dismiss this. Sure it might not sit flush to the can but when air is in motion you might not need a complete flush transition to get the desired effect. For example you get less drag in a pickup with the tailgate up vs down thing. Seems like it should be the other way around but pockets of air can fill in the voids and help reduce drag. Did Honda design intentions take this into account? Who knows but who am I to doubt them. The majority of us on the forum have not designed a car nor have access to facilities to do this type of testing but they do, so I don't think the credit is unwarrented.
Last edited:
- Joined
- 19 February 2008
- Messages
- 1,532
Quick question as I am trying to figure this sales guide out…
are you sure that that figure isn’t .2%?
if it is 2%- the front undercover increased by 40%
if its .2% - pat yourself on the back for not giving Honda to much credit?
I said it earlier but 70kg off a 1270 kg car is 5.5% of the total weight. Some parts on the car will receive an increase in performance of greater than 5.5%
Lower the weight with a dialed in suspension = you have a faster car.
Oh yeah... that faster car also includes a titanium shift knob, sick seats, and a pretty cool sales literature piece... TY for posting that
If the diffuser reduced Clf .002 and the spoiler reduced Clf by .085, the reduction of Clf by the diffuser alone is 2.38% relative to that by the spoiler alone.
(edit: the above figure should be 2.35%)
Relative to the total Clf reduction from all of the parts (-0.100), the diffuser accounts for 2% of the total.
Although the arithmetic calculation above is correct, the fundamental reasoning is flawed because the sum of the individual Clf reductions are not additive.
Since the Clf values are not additive, it is difficult to gauge how much each component contributed. However, given the order of 10 difference the diffuser had on Clf relative to other components individually, it is safe to presume it contributed a marginal amount to the overall Clf reduction.
Attachments
Last edited:
- Joined
- 19 February 2008
- Messages
- 1,532
dam.. I'm a math junkie and it sucks that the reduction was -.10 since its divisible by 10 and makes figuring out your equation a lil harder.
.002 of .1 instead of .002 of 1 is 2%... but its not 2.38%
would you mind showing the equation?
and 2% of -.10 is so minimal.. toss is out the window when you account for wind passing cars ect ect... math is always right.. but you cant predict all circumstances
Again, since the individual reductions are not cumulatively additive, it is flawed to take each component on it's own and calculate a percentage of the total.
From greenberet's post:
greenberet said:
When stated "about 2% as much as the bigger rear wing did" the calcuation I performed was:
100*Clf(diffuser)/Clf(wing) = 100*.002/.085 = 2.35%
:redface:sorry I did fat finger the last significant digit on my earlier calculation to 2.38, instead of 2.35%:redface:
Why do you say the reductions in the lift coefficient Honda published on that web page are not cumulatively additive?
The coefficient of lift is calculated by measuring how the force the car exerts on scales changes in a wind tunnel and then dividing that apparent change in weight by the plan (top) area of the car, taking the air density and airspeed into account. As long as the plan area of the car doesn’t change, the lift coefficient is simply a certain percentage of the lift or downforce measured by the scales. If something changes the lift coefficient by a certain amount (say, -0.002), then that’s because it changed the weight measured by the scales by a certain amount. If another change reduces the lift coefficient by another -0.002, then the scales will measure twice the reduction in lift.
If you add up the lift reduction measures on the web page linked to in post #127, the things that impact mainly the front axle should reduce the lift coefficient by 0.1 and the things that impact mainly the rear axle should reduce the lift coefficient by 0.087. Since the coefficients of lift ended up as -0.04 at the front and -0.06 at the rear for the 2002 NSX-R, they should have started out as +0.06 at the front and +0.027 at the rear for the regular 2002 NSX if the figures are cumulatively additive, right? If the numbers for each component are not cumulatively additive, then those should not be the front and rear lift figures for a 2002 NSX.
The numbers may not be cumulatively additive if Honda didn’t take the interactions between the components into account when publishing the figures. A rear wing can help a rear diffuser create more downforce, for example. Then the overall reduction in lift may be even greater than the sum of the individual parts. On the other hand, the figures Honda published may have taken the interactions into account but be for the front or rear axles individually without considering that creating downforce behind the rear axle tends to lift the front axle, kind of like on a see-saw. If that's the case then the total reduction in lift may be slightly less than the sum of the individual parts.
On this web page (http://www.honda.co.jp/auto-lineup/nsx/2005/mechanism/index.html), Honda states that the lift coefficient of the standard 2002 NSX is +0.055 at the front and +0.02 at the rear. That's quite close to, but slightly less than, the figures implied on the 2002 NSX-R web page. So I'd strongly suspect that the figures on the NSX-R web page are cumulatively additive but that they show the changes in front or rear lift, not cumulative lift. Or that there are simply rounding errors.
Getting back to the diffuser, if the OEM 2002 NSX-R rear "diffuser" reduces the lift coefficient by 0.002, it should reduce lift by 3 or 4 pounds at 175 mph. That’s really not much but it probably doesn't add much weight and at least it looks racy.
This page clears up the information greatly.
I misunderstood the information on this page http://world.honda.com/NSX/technology/t3.html as the change from the stock NSX, not the absolute value.
That's what made it not seem additive.
You are right, compared to a baseline figures you provided things do actually add up.
I stand corrected. :redface:
And at 90 mph (which is an avg speed around a road course) that amounts to almost nothing.
- Joined
- 19 February 2008
- Messages
- 1,532
And at 90 mph (which is an avg speed around a road course) that amounts to almost nothing.
There you have it folks... the NSX Myth Buster team has been formed and equation has been identifiesd..
The TEAM consisted of a weekend warrior track junkie, an outcast, a highly trained back eagle operative researcher, and a math whiz who likes to be reffered to as cars that origanaly sold for less that 6k from the dealership
Captain STMPO GreenBeret geometro and a picture thread can solve the unknown...
This weeks bust - Type R can be Type R.... But it can also be Type E (estetics)
Were now taking suggestions for other busts...
90% of the users don't even make full use of the diffusers. Just for looks and bragging right:tongue:
fixed
^^^^^^Too funny.:biggrin:
lol :biggrin:
This one is for sale on Yahoo JP at the moment. Best one I seen yet for a street car, cleans up the rear alot.
http://page7.auctions.yahoo.co.jp/jp/auction/g116328269
http://page7.auctions.yahoo.co.jp/jp/auction/g116328269
Looks like an authentic Marga Hill Diffuser. Never seen one not intalled though. That looks like it goes way deep into the underside of the car.
Covering the jagged bits beneath the car has to be good for aerodynamics and hiding the muffler is good for aesthetics. However, the rear, inclined portion of that underbody cover looks far too steep to be functional as a diffuser.
Thats why I said street car :wink: :tongue:
- Joined
- 21 December 2005
- Messages
- 1,215
Why is it set so far in?
That's what she said.
Similar threads
