thisisntjared

front lip --> aerodynamics++ = mpg++

can anyone supplement this theory? in theory it makes sense and honda made the oem lip for a reason, but how effective is it? ive been doing lots of minor(inexpensive) tweaks to my car to see if i can improve the highway efficiency without cutting out weekend performance and i recently put on an oem lip on my cx hatch.

in english: a front lip implies better aerodynamics which equals better miles per gallon. can anybody provide useful examples or insight?

moores55

all for the bling factor

thisisntjared

even the lip that comes on the model intended for better fuel consumption?

suspendedHatch

What model specifically are you talking about?

What is "better aerodynamics"? Some people think that more downforce is better, and some people think that less coefficient of drag is better. But you can't have both.

I seriously doubt a front lip helps mpg unless it's an undertray. Anything that increases the frontal area decreases mpg.

Redline96LX

Yes, if you get a lip that alters the aerodynamic shape, you will affect MPG and downforce. But there are many lips, so I don't think either will be noticable to you.

Biggest factor is to have that spoiler thing on a hatch. Also, the VX has this slight diffuser under the back. The back bumper on our cars can act as a parachute. Rig up a plastic plate (thin and crude is ok) for the back under the car, that will do more than a lip odds are.

thisisntjared

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by suspendedHatch &raquo;</TD></TR><TR><TD CLASS="quote">What model specifically are you talking about?

What is "better aerodynamics"? Some people think that more downforce is better, and some people think that less coefficient of drag is better. But you can't have both.

I seriously doubt a front lip helps mpg unless it's an undertray. Anything that increases the frontal area decreases mpg.</TD></TR></TABLE>im talking about any lip on the civics prescribed in this forum.

in my specific instance i am refferring to better aerodynamics as a lower coefficient of drag. however, in some instances you can have both. i.e. the oem diffuser which eliminates the high pressure system caused by the parachute of the bumper, therefore decreasing lift(almost the same as downforce ) while making the entire area more streamline improving the coefficient of drage.

im sorry for not clarifying my terminology earlier . also i have studied the way the oem lip works. it simply removes the inward curve on the lower part of the front bumper thus not permitting as much air to be directed underneath the car. the section where it would increase the frontal area is just in front of the tires, so in theory its helping there too as less air is going to such a turbulant area as the tires.

in general i would think anything to help stop air from going under the car would be excellent in reducing lift(lower pressure under vehicle) and improving the cd since the air would be thinner where it is more turbulant, under the car.

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Redline96LX &raquo;</TD></TR><TR><TD CLASS="quote">Yes, if you get a lip that alters the aerodynamic shape, you will affect MPG and downforce. But there are many lips, so I don't think either will be noticable to you.

Biggest factor is to have that spoiler thing on a hatch. Also, the VX has this slight diffuser under the back. The back bumper on our cars can act as a parachute. Rig up a plastic plate (thin and crude is ok) for the back under the car, that will do more than a lip odds are.</TD></TR></TABLE>i didnt think it would be that noticeable either, but thats why i posted to try to squeeze any thoughts i mightve missed or experiences out of the general honda population.

also no need for the oem diffuser, i decided to not care about looks and cut off the lower 3in of my rear bumper last month. i have a theory as to why this is better than holes in the bumper but i will save that for another post. so far i have been getting 36-38mpg consistantly 75% highway driving at 80mph consistantly. all non highway driving i take my car to vtec from every light also quite consistantly. in another month(4 tanks later) i will see if this lip helped at all. it seems more quiet for some reason...

nice sedan btw. some stiffer springs and youve got a pretty complete package

salesmonkey

lips are cosmetic like a body kit

Sly_Samba

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by salesmonkey &raquo;</TD></TR><TR><TD CLASS="quote">lips are cosmetic like a body kit</TD></TR></TABLE>

A well designed body kit is not only cosmetic.

G2 Speed

but then your talking about mugen bodykits.. which cost 4g's

BryanPendleton

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by thisisntjared &raquo;</TD></TR><TR><TD CLASS="quote">in my specific instance i am refferring to better aerodynamics as a lower coefficient of drag. however, in some instances you can have both. i.e. the oem diffuser which eliminates the high pressure system caused by the parachute of the bumper, therefore decreasing lift(almost the same as downforce ) while making the entire area more streamline improving the coefficient of drage.

im sorry for not clarifying my terminology earlier . also i have studied the way the oem lip works. it simply removes the inward curve on the lower part of the front bumper thus not permitting as much air to be directed underneath the car. the section where it would increase the frontal area is just in front of the tires, so in theory its helping there too as less air is going to such a turbulant area as the tires.

in general i would think anything to help stop air from going under the car would be excellent in reducing lift(lower pressure under vehicle) and improving the cd since the air would be thinner where it is more turbulant, under the car.
</TD></TR></TABLE>

The wake of a vehicle is a low pressure region, NOT a high pressure region. This low pressure region is one of the major contributors of a cars overall Cd (drag coefficient). Minimizing the wake can pay dividends on reducing overall Cd. Holes in the bumper, that lower diffuser you are talking about, and probably cutting your bumper up like you have described.

Air is everywhere, so putting a lip infront of the tires, does not "protect" the tires.

Your concern is reducing the vehicles overall Cd (drag coefficient), so the dicussion of lift in not of important. With that said, whether the air goes under the car or over is not important either, as mentioned the goal is Cd reduction, not lift control.

Some areas of attack:

1) One component of Cd is viscous drag. This is the drag associated with viscous flow accross a surface area. You can reduce viscous drag by reducing surface area.

2) Another component is pressure differential. As mention earlier, the rear of the vehicle creates a nasty lower pressure wake that kills the Cd of a car. Minimzing the size of this wake will improve Cd.

3) Another component is fluid seperation. Fluid seperation is when a fluid can not negociate a obsticle or path without creating a turbulent eddie or low pressure region, just like your wake at the rear of your car. DO NOT misunderstand fluid separation as turbulence. Keep in mind most flow with respect to a car is turbulent. Turbulent flow is not a BAD thing either, as it helps you golf ***** fly further and can reduce you Cd if controlled properly. To minimize fluid separation though you best bet is to stream line the car. Any edge, ledge, obstruction, etc. can cause seperation.

BryanPendleton

With all that said, my thoughts on a lip are this. They increase surface area thus viscous drag. They serve to "direct" flow, there by altering lift, and in the case of a lower front spoiler it directs air into the engine bay, increaseing visous drag and fluid seperation. It also creates another wake itself, thus you have a low pressure region just behind the lip, further reducing Cd.

Everything with regard to a lip spells an increase in Cd (drag coefficent).

As for the diffuser, I am guessing (having never seen it) it reduces car wake and streemlines to improve Cd, but the increased surface area will increase Cd, but I can almost guarantee you that the positives outway the negatives. Can't say the same for a front lip.


Modified by BryanPendleton at 12:34 PM 1/23/2006

thisisntjared

bryan, your my hero its good to know that honda-tech has more to it than just single sentence uneducated guesses. when i was reffering to the higher pressure area around the rear bumper i was reffering the the area in front of the rear bumper, under the car. either way i agree with you.

so to further the conversation: do all of those abs plastic sheets and lining in the bottom of the engine bay, in the wheel wells and even the side skirts help in reducing the coefficient of drag?

also i do not have a/c in my car at all. would blocking off that side of my grill with abs plastic help in reducing cd? since it would effectively remove something causing separation?(some air goes directly into the engine bay, some stays outside the car)

thanks again soooo much for your intelligent insight and advice.

BryanPendleton

IMO, the plastic lining in the bottom of the engine bay is probably beneficial in streamlining the bottom side of the car. Is there room for improvement? Absolutely! As for wheel linings and side skirts, I don't see them having a significant impact on Cd.

Get yourself a set of "moon hub caps" Sheet metal over the rear wheel arches. Line the bottom side with sheet metal. Blocking off flow into the engine bay will help. Maybe some spoon side mirrors to reduct frontal area and stream line. Shave door handles, antenna, wipers, drip grooves, relocate gas to truck and weld up gas door, remove windshield squirters. You biggest improvements are going to come from minimzing that wake at the rear of the car. If you can use sheet metal to "curve up" towards the rear. This will require modifications, perhaps moving the muffler. . . You could get crazy with creating an aerodynamic car. If you want some tips, look up land speed record cars. There are a variety of classes, so of which the civic will fall into, and see what kind of modifications they make. I believe there is a civic that held a land speed record at one time, may still hold it.

mugenpowered

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by G2 Speed &raquo;</TD></TR><TR><TD CLASS="quote">but then your talking about mugen bodykits.. which cost 4g's</TD></TR></TABLE>
Yup, those lip kits are actually tested in a wind tunnel, and they actually effect downforce.

thisisntjared

i doubt i could go as far as shaving door handles wipers drip grooves and relocating the gas door. but it is inspiring. do the spoon mirrors really help that much? i was also thinking of an partial under-body tray focusing on the rear and front of the car, but thats a lot of work. i am definitely inspired though.

ReggieGrip

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by G2 Speed &raquo;</TD></TR><TR><TD CLASS="quote">but then your talking about mugen bodykits.. which cost 4g's</TD></TR></TABLE>

could someone give me a link to these? i want to see what 4k body kits look like, the curiosity has got the best of me....

8krdline

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by BryanPendleton &raquo;</TD></TR><TR><TD CLASS="quote">IMO, the plastic lining in the bottom of the engine bay is probably beneficial in streamlining the bottom side of the car. </TD></TR></TABLE>

I agree

BryanPendleton

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by thisisntjared &raquo;</TD></TR><TR><TD CLASS="quote"> do the spoon mirrors really help that much? </TD></TR></TABLE>

I have not idea the magnitude or the significance these changes will make, but IMO its a step in the right direction.

suspendedHatch

One-lined uneducated guesses. That's funny. Tried to sum up the best info I could give you based on a unit in a class I took focusing on wind tunnels and F1 cars. I doubt you'll actually do anything that would make a difference, because it is 1) too costly, 2) too difficult, or 3) too impractical. But there WAS a guy with an Integra on these forums that had build a rear diffuser with seperators at the ideal angle out of sheet metal (sorry, the corect terminology and details escape me at this time of night.) You could take off your windshield wipers. That would make a big difference, but it just isn't practical for most people.

My car is lowered, has spoon style mirors, vx rear diffuser (decreases surface area btw), freeway miles are about 36-38. Right about where most Civics are. My friend gets significantly better, but he has no aerodynamic mods. He has an EG hatch with a EK HX motor, AEM EMS tuned to run lean 16:1 ratio when cruising.

thisisntjared

your probably right. i doubt ill get much better than what i have now<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by suspendedHatch &raquo;</TD></TR><TR><TD CLASS="quote">My friend gets significantly better, but he has no aerodynamic mods. He has an EG hatch with a EK HX motor, AEM EMS tuned to run lean 16:1 ratio when cruising.</TD></TR></TABLE>ive always thought about doing that. but using a z6/y8 tranny... doesnt the hx run on a lean burn from honda though?

97spooncivic

i would think you would get .00000000000000001 mpg more than without a lip

BryanPendleton

And thats the difficulty in all of this. There is not way to truely measure your results, without a hundred other factors and variable coming into play.