Front body undercover (and perhaps rear too..)

[MvM]

I am working on a body undercover for my NSX.
The original NSX Type R has a carbon body undercover at the front of the car, just under the battery tray. According to my information, this undercover is even more effective in reducing lift then the NSX Type R vented hood.
So far I have created the following very simple device. The tray is 60cm wide and 80cm long (about 26"x 32"). Like the original cover, it has two longitudal fins 2.5cm (1.0") high. When fixed, it will cover the compete battery tray from front to the rear. The width of the plate is the same as the black plastic front flap. In fact, I have left a rim of 2" wide in front to slide under this plastic at the front. The cover is made from a single slab of aluminum, 65x80cm and 0.1 cm (0.04") thick. Total weight so far is only 1.4 kg (about 3.1 lbs).

I have a question left however. Even with the NSX-R the space underneath the gastank is left uncovered. I was wondering if there would be a specific reason for that because it seems to be a very simple thing to cover this part of your underbody as well.
BTW, the picture to the right is from the normal NSX Type R.

I will post more pictures when the cover is attached to the car.

 

[rbirling]

You probably wouldn't want to do this without the NSX-R hood (you didn't say whether you have the hood or not). If you don't have the vent in the hood, and you cover up the bottom of the car, cooling air won't be able to flow very easily through the radiator, and I would expect cooling problems, and increased drag.

 

[MvM]

I do not have the Type R hood and yes, I understand what you mean.

I have had several discussion about this problem and noone has been able to really answer all my questions.
The costs of this mod is very low and I think in this case the proof is in the pudding as they say.

If it will not work it will be just as easy to remove the cover again and in this case it is not much work to try it out and see if it will work or not

When fitted, there will still be space left and right from the cover for the air from the radiator to go to.
However, if you look at the underbody opening right now, it is a mixture of uneven formatted openings, both from left to right and from front to rear. So whatever the airflow is right now, it can never be smooth. With this cover mounted, I suspect that the air will now pass the cover on the left and right in a more jettisoned way. Pressure at those points will be higher of course, but it will at least flow more direct and undisturbed towards the rear. At the same time, the air entering the space under the car directly will flow more smoothly to the rear for the width of the undercover at least.

According to the Type R info, the undercover tray will reducte the front Lift Coefficient by 0.040, whereas the Type R hood only makes a difference in Lift Coefficient of 0.025

 

[rbirling]

It will be interesting to hear your results. I agree that it is a bit of an unknown how this will affect the car without the hood. I don't suppose you have a way to test your Cd (or Cl or whatever) change? :smile:

 

[MvM]

You touch upon a subject that I have thought as well.
The NSX Type R says all modifications together results in something like 35Kg downforce at the front at 180 kph. So, technically speaking, if you know the springrate of your front shocks and would have a way to measure the total height of the car while driving, you could calculate your amount of downforce.
Unfortunately, I cannot think of any way of doing that. Even with a full 35 kg downforce, the total compression of your springs is only about 2mm at the most.

Anyway, I'm working on the NSX tomorrow and given enough time, I will try to mount this underbody cover onto the car. When I'm done, I will post the pictures. Testing it, however, will have to be postponed until the rest of the car is ready too.

 

[garyn]

Just a thought when comparing before and after undercover panel. If you have access to a race track, you can compare E.T. and trap speed times.

 

[NSX-SA]

Pics of my undertray made from ABS acrylic. I dont have a Type-R bonnet and dont have any overheating problems driving in peak traffic at 40c heat or while travelling at 270km for extended periods. I have noticed downforce has increased significantly on the front. I am working on a rear diffuser atm and will post pics when finished.

 

[MvM]

Pics of my undertray made from ABS acrylic. I dont have a Type-R bonnet and dont have any overheating problems driving in peak traffic at 40c heat or while travelling at 270km for extended periods. I have noticed downforce has increased significantly on the front. I am working on a rear diffuser atm and will post pics when finished.

Very informative post and pictures. Your undercover is really an Undercover.

Yesterday I had some time to fix my own undercover to the car.
So far, this is the result. As anyone can see, there is enough space left and right for any air from the radiator to flow to, but after the previous post that was already obvious I guess.

 

[WingZ]

I don't think the tray that you made would cause overheating ,but the black undercover ahead of it.

 

[Bram]

This is very good underbody tray...Can you post the diamensions of your undertray and maybe how is mounted to the underbody.

Thanks, Bram

Pics of my undertray made from ABS acrylic. I dont have a Type-R bonnet and dont have any overheating problems driving in peak traffic at 40c heat or while travelling at 270km for extended periods. I have noticed downforce has increased significantly on the front. I am working on a rear diffuser atm and will post pics when finished.

 

[goldNSX]

Good project, MvM? I had sth similar in mind a year ago but left it. Some people reported that the OEM front-end is a little bit nervous above 240 km/h which was reduced by the Type-R hood and the underbody. But I think that your underbody tray should be a little bit wider to get in effect.

 

[AR]

I don't think the tray that you made would cause overheating ,but the black undercover ahead of it.

My car has that black undercover, is it not standard, I can't remember looking that well under my 99.

 

[WingZ]

My car has that black undercover, is it not standard, I can't remember looking that well under my 99.

I just looked under my 04 and there's a partial cover in the center ,but nothing like some of the side to side covers shown above.

 

[Bob Kenney]

Pics of my undertray made from ABS acrylic. I dont have a Type-R bonnet and dont have any overheating problems driving in peak traffic at 40c heat or while travelling at 270km for extended periods. I have noticed downforce has increased significantly on the front. I am working on a rear diffuser atm and will post pics when finished.

I am Impressed!!
Estimated total weight increase?
Thickness of the material used?
How long have you had it in place?

 

[MvM]

Good project, MvM? I had sth similar in mind a year ago but left it. Some people reported that the OEM front-end is a little bit nervous above 240 km/h which was reduced by the Type-R hood and the underbody. But I think that your underbody tray should be a little bit wider to get in effect.

Hi Thomas,

As far as I could judge from the Type R pictures, my undercover is about the same width as the original one. There is some room left on both sides so the radiator air has space to go somewhere. So far it is hard to tell if it has any benefit. I have had the car to up around 160 mph without any trouble. The nervousness I had one time was more attributable to a not very flat road surface. Overheating has simply not been an issue at all.

 

[da3dalus]

I have also been intrested in creating a front underbody diffusor as well. Thanks for the informative posts and great pictures. Estimated cost of the ABS plastic diffusor? I'm thinking that it might be the better way to go instead of metal, carbon fiber, etc...

I found what looks to be a front underbody tray on the Route KS site...