[Bboy_Burst]

be sure to take it off when you run the 1/4, then put it back on and see if there's a difference

 

[purplemonkeydishwasher]

Taken from Wikipedia:

Acura NSX 90's Drag Coefficient - 0.32
Honda Civic Sedan Drag Coefficient - 0.31
Acura NSX 02+'s Drag Coefficient - 0.30
Toyota Prius Drag Coefficient - 0.29
Honda Civic Hybrid Drag Coefficient - 0.27

Pretty impressive numbers considering it's got less drag than both the Prius AND a 'supercar'.

Edit: Nevermind. The 2010 Prius has a DC of 0.25

Actually...it's astounding how high drag coefficients on supercars have. They are notorious for being very bad with drag numbers. It's because a lot of aerodynamic stabalizers are used on supercars to help with negative lift...and when you talk aero, it's always a trade off between more downforce or less drag.

be sure to take it off when you run the 1/4, then put it back on and see if there's a difference

^^ this is a great idea. OP you should really do some tests and post it up so we can see some data. Have you thought about running a completly smooth under carriage as well?

 

[Leonard1818]

This is a GREAT idea.

But...

in order for it to be worthwhile, we would need to know, on average, how much higher MPG this yields. at $140+, it would need to add some significant gains in HP to make it worthwhile.

I agree that you should take it off and log 5-10 fill up MPG's and then put it back on and do the same. Then, figure the average increase in MPG by using it. We could use that number along with our local gas prices to put an exact dollar-savings number to each fill up with these parts in place!

 

[miky360]

been wanting to do something like this for a while
where can i buy this? :wigglesmiley:

 

[WhiteCivic10]

Do you have the part numbers man?

I'll do this prob within the next month.

 

[sivtecboi80]

I wish they made the whole kit for a coupe then i would do it. This is very ingenious of you op! If you look at the undersides of a Ferrari,Pagani,bugatti or any other race type street machine they run full covered bellies. This i would think help with 1/4mile times,topspeed times and better gas mileage via eliminating airdrag. Some aftermarket company should come out with something that fits both platforms i would be all over it.

 

[aki]

That's awesome, I wonder if it'd fit coupes? =O Pretty ingenious, surprised nobody tried it before.

in order for it to be worthwhile, we would need to know, on average, how much higher MPG this yields. at $140+, it would need to add some significant gains in HP to make it worthwhile.

Well it's only helping with making the airflow underneath less turbulent. Less drag = goodness all around.

 

[k20 Fcukin Fritz]

the front does but the back does not from what the op has put

 

[Leonard1818]

Less drag = goodness all around.

Yes, but how MUCH goodness? What are you after, better MPG? Better performance? Both?

Without knowing HOW MUCH better MPG or performance something like this actually yields, it's impossible to determine if it's really worth it.

I can't believe everyone is blindly saying they're just going to do it without knowing what it *actually* does...

I'm not saying it's a bad idea... I'm just saying that from an economical perspective it may not actually be worth it. Until we have some data, we don't really know.

Don't you think Honda would have considered this on the Si if it *really* made that much difference? And Honda isn't paying ~$150 for these parts... I would think that if it provided a lot of benefit on the Si that it would have come on there stock. Honda could have claimed better MPG and better aerodynamics.

p.s. I think they make a similar part for the rear of the coupe. Is the rear of the coupe covered up underneath?

 

[aki]

I can't believe everyone is blindly saying they're just going to do it without knowing what it *actually* does...

Erm, we do know what it does, it's called the Bernoulli principle. A flat bottom reduces drag, which allows air to move quicker. The air moving quicker reduces pressure, which in turn reduces lift and promotes downforce.

The "why wouldn't Honda include it for $150" is exactly why Honda didn't include it. Why didn't Honda include a better intake for $150? Better wheels? Better X? Because to keep the car in a certain price range for a particular market demographic, they can't include the whole kitchen sink.

If you're questioning its usefulness, the CTR comes with underbody paneling too, and I'm guessing it's pretty similar to the Hybrid.

 

[FB Si]

I think the underbody parts are a good idea for the hybrids, but those parts will also prevent some heat from escaping under the car. Heat soak is going to be worse, especially if you're stuck in traffic.

These parts could even actually generate a little lift at higher speeds.

 

[aki]

I think the underbody parts are a good idea for the hybrids, but those parts will also prevent some heat from escaping under the car. Heat soak is going to be worse, especially if you're stuck in traffic.

These parts could even actually generate a little lift at higher speeds.

How would it produce heat soak if the cat/b-pipe area is entirely uncovered? The portion below the engine bay is already covered, it's covering mainly the sides.

And what property of physics causes this to generate lift at higher speeds? It's actually the exact opposite, the faster you go the more you benefit from this.

 

[Leonard1818]

Erm, we do know what it does, it's called the Bernoulli principle. A flat bottom reduces drag, which allows air to move quicker. The air moving quicker reduces pressure, which in turn reduces lift and promotes downforce.

The "why wouldn't Honda include it for $150" is exactly why Honda didn't include it. Why didn't Honda include a better intake for $150? Better wheels? Better X? Because to keep the car in a certain price range for a particular market demographic, they can't include the whole kitchen sink.

If you're questioning its usefulness, the CTR comes with underbody paneling too, and I'm guessing it's pretty similar to the Hybrid.

Thanks but you're still missing the point. HOW MUCH (IN DOLLARS) DOES THIS BENEFIT A CONSUMER?!?!?!?

I have no dobut it makes a difference in some way. NO DOUBT ABOUT IT! Why else would they include it on the HYBRID?! That's not the question here...

Since you seem to be pretty bright, let me break this down for you. This costs $150. Let's pretend I want this JUST for MPG purposes. Let's also assume gas is $2.80/gallon right now. This means I can buy 53.57 gallons of gas with this $150. If i get 30mpg on average (which I do), that means for $150 I can travel an additional 1,607 miles.

These are numbers. The above example is QUANTIFIABLE. My point is, it CAN NOT yet be proven that I will BENEFIT MORE by buying this for $150 than simply saving the $150 and buying additional gasoline.

Do you get my point yet?

I understand Honda would not include this because of cost reasons. My point being made with that comment is that Honda certainly has a threshold that must be met of cost:benfit for what parts they include on a vehicle as part X may not provide enough benefit to justify the additional cost incurred by including that part. Obviously, Honda did not consider this particular part to yield enough benefit for what it cost to include it in on the vehicle. Sure there are probably other variables at play... most notibly (and likely one of the big deciding factors) is that the standard part for Hybrids would have needed to be modified to fit the Si oil pan (as the OP mentioned). This would drive up production costs since they would either not be able to be produced on the same assembly line or there would be an additional step to making the same part for an Si model. The additional cost incurred to make this product for the Si is likely why it was not included. But, as mentioned in the quote below, there were probably OTHER reasons it wasn't included.

I think the underbody parts are a good idea for the hybrids, but those parts will also prevent some heat from escaping under the car. Heat soak is going to be worse, especially if you're stuck in traffic.

These parts could even actually generate a little lift at higher speeds.

I thought about the heat dissipation aspect previously as well. I'm not sure if the Si runs hotter than the Hybrid but it is something to consider.

 

[K20Z3allmotor]

i edited the 1st post to show the hybrid bolts needed to secure rear panels.

 

[K20Z3allmotor]

be sure to take it off when you run the 1/4, then put it back on and see if there's a difference

ill be sure to do that next time im up there.

 

[K20Z3allmotor]

I think the underbody parts are a good idea for the hybrids, but those parts will also prevent some heat from escaping under the car. Heat soak is going to be worse, especially if you're stuck in traffic.

These parts could even actually generate a little lift at higher speeds.

this is why we have radiators and cooling fans, heat will escape as soon as you start moving just like in any car. plus my engine bay stays super clean.

 

[FB Si]

this is why we have radiators and cooling fans, heat will escape as soon as you start moving just like in any car. plus my engine bay stays super clean.

And where do you think the heat escapes when you're sitting still or moving? Answer: Much of it is blown under the car.

There is a reason why only the hybrids have these parts. Think about it...

 

[sivtecboi80]

I think at the end of the day you probably are going to only gain a few miles better a tank than without it. I have no proof or results but if you think about it, what its really doing is creating less drag which will help yeild better mpg as your engine will work less to keep the car moving. Its also going to help with trap speed i belive maybe only a 1-2mph better, just my theorey. I think honda didnt do it just like another member mentioned even though it doesnt cost alot on there part it adds up. They put it on the hybrid because it helps them acheive better mpgs so its a benefit moreso with the hybrid to acheive their mpg status.

 

[K20Z3allmotor]

And where do you think the heat escapes when you're sitting still or moving? Answer: Much of it is blown under the car.

There is a reason why only the hybrids have these parts. Think about it...

air flow out of the header tunnel area, no were else, that part is still open, these cars are not motorcycles, you can let it sit idleing for hrs, the fans will kick on to allow the coolant to cool and regulated by the thermostat to keep it from getting to cold. this obsession with heat soak has got to stop, get a IMG and call it a day. upgraded radiators, vented hoods, etc are a waste of time on a SI with no turbo or S/C.

i think the real reason honda did not add this on to other civics is because of costs, the chassis would have to have more holes, subframe too, and they would have to make it fit coupes which would involve more parts and production cost. i had to modify mine to fit, think about how much more it would have took for honda to design it to fit the whole line up with different engines and subframes and chassis.

 

[K20Z3allmotor]

updated on page one, made a cover for the big hole cut out to clear oil pan.

i also been averaging about 1 mpg better than before.