FWD Aerodynamics Info

[Glen]

It's always a good idea to have a stiffner or two depending on the surface area. Something as small as a piece of 1/2" alum. angle will take a lot of the vibration and stiffen the panel.

[SPARKY]

I am not knowledgable about your car--- but I would bet that it has lots of body dum dum between the body panels for noise abatement,  I am sure you could find lots of weight you could take off the rear of the car between the inner and outer body panels. I also think McRat is on the right track with the wheel wells, wheels and tires.  I would be looking into how to diminish wheel-tire pumping losses.  Also there are lots of replacment glass that is thinner than original and therefore would weigh less.  Every OUNCE you can move as far forward of the CL of the frt axel helps your cause---including your seat position as you race. I would concentrate on moving my CG forward.

after thought update:
every ounce you move from the rear of the car and reinstall in front of the frt axle CL actually puts more than an ounce on the frt tires

[mtkawboy]

From a former NHRA stock eliminator racer, lightest weight synthetic oil every where thats safe to run, light weight synthetic wheel bearing grease, keeping brakes backed off, run engine a little lower on oil, ultra hi dollar bearings everywhere if youre budget allows it. Get the car as easy to push by hand as possable. By itself each adds a little but together it can make a difference, every little bit helps. This and what everyone else has mentioned has to help a little

[Jonny Hotnuts]

I doubt this would be legal but many of the high end euro cars are using active aeros. I could see a spoiler/ canard (front and rear) controlled by an actuator (maybe go from high DF to zero DF triggered by a gear change?).

You could get high DF through the first few gears and then loose the drag in higher speeds.

I agree however that because you are in a weight limited class more HP is going to have a biggest factor, aeros wont have a huge affect till you are going faster.
Unfortunately with most forms of racing the real race is to the bank.

GOod luck
~JH

[allmotorcoupe]

Those are some good ideas guys, thank you all for your insight.

I have been doing some research and using the search on this site has given me a plethora of ideas . . . . . and a few more questions haha . .

1.) I know that lowering the front of the car will stop more air coming under the car. However If I do a full belly pan, ( Keep in mind my front bumper is entirely sealed off as well) would I still want to lower the car as much as possible? If I were to leave it a little bit higher so that more air could go under the car - where the underbody panels could shine - and help the air move quicker then if it were to go over the car . .
Basically I am just trying to figure out, that with my front end being sealed as it is, would lowering the car too much up front almost create too much downforce? Which i do not need ?

2.) I run an open header. The header ends just beyond the firewall . . If I were to build a full belly pan - I would have to do something with the exhaust gases. .  Now I could put a 6-8 inch pipe on the end of the header and have it dump down on an angle, and it would be flush with the under panel.
Is it possible that, if we directed more air under the car with the header like that - that the air could also help create a scavenging effect and almost help pull the air out of the motor faster? Resulting in a HP gain ?
Now the type of header I run ends with a reverse megaphone . . Ideally you do not want any length of pipe after the megaphone. So If i were to do what I mentioned above, I would most likely lose a few HP by adding length of pipe to the end of the header, so would be doing all of that be worth it based upon that ?

[SPARKY]

Where does the end of header point? You want it pointing at the starting line---parallel to the ground!!!!!!!! to use the thrust that Pat was talking about to help you get to the finish line

[allmotorcoupe]

It points straight back at the back of the car

Remember, its only a little 4cyl so there probably isnt that much thrust haha

[dw230]

Give this idea a thought. When using Dzus fasteners use the ones that are captured. These are on a small plate with a spring attached and the whole deal is attached to the panel. When loosened the button is still a part of the panel. This solves the problem of a button becoming loose and dropping on the race track causing a potential hazard for you or your fellow competitors. Sorry, I do not have info as to part numbers, etc.

DW

[Caveman]

Honestly dude?  A belly pan is a great idea, but only in LSR where weight can actually help. 

The weight of the pan will hurt your ET more than any aero gain it would give you....  unless you take your car to B'ville that is.

Answer to the Aero issue AND the weight issue?

1)  Lower the front of the car...  A LOT.  I'm talking cm's of ground clearance.  Have someone take a good pic of your car on the top end as you go through the traps at 130mph.  You'd be suprised how much acceleration and wind actually lift the front end.

2) Drill holes in anything non-structural (and even some in structural!) areas to lose weight.  Think inner body areas.

3) Cut out big chunks of inner door panel, holes in the door jam, the body areas underneath the rear bumper, the front bumper, the radiator mounting sheet metal, inner portions of fender structures, rear floor areas....  ANYWHERE to shave ounces.  If you have anything other than a steering wheel and a firewall, a seat, and a fire bottle, its dead weight.  Drop it.

THAT will get you those .002 seconds-----and a few more wins.

4) You may want to think of a slightly lower final drive ratio, or a slightly shorter slick.  That will also help acceleration, as the physics of better gearing always favor getting that 2k+ lbs rolling quicker.  A friend of mine in a 2,800lb car went from a 4.10 gear to a 4.56, and dropped nearly 2 tenths.  Top end speed was roughly the same...  but he got there in less time.

[1 fast evo 2]

I hope I can help you out a little as I come from an import drag racing back ground, I used to run in the Nopi turbo 4 class with my car which is a Mitsubishi evo 2, turbo 2.0 ltr.

The first thing is what rules are you running, are they using the N.H.R.A. rules as alot of series do or something different?
The reason I'm asking is due to the front ride height that everyone is suggesting may get you kicked out of a race as per the N.H.R.A. front ride height can't be lower than 3 ".

Aero wise I think you are on the rite track, I think you will see very good gains by lowering the front and closing off the front of the car.
Do not raise the rear edge of the hood, you where rite in your 1st assumption, if you can just run some tape across the back edge to seal the gap to the cowl area( this is a low pressure area, when you raise the hood it lets air in not out.), close off the interior of the wheel wells.
I also agree with Caveman about the belly pan, I would forget about it at the speeds and duration of time you are running. I think the above mods will get you the gains you are looking for, after these it's back to the old dragracing standards.

You need to have the best short time of anyone if you can't afford the power that the big boys are bring to the table, are all your tire and gear ratios optimized?
What is the front to rear weight percentage, is it still safe or within the rules, if I remember correctly for a front drive at an N.H.R.A. ruled event it was 70-30 front to rear.
Do you run a wheely bar, can you?
Are you running a dog box trans with a good clutch?

[allmotorcoupe]

Again, thanks for the help guys . .

I will try to answer all of the questions . .

dw230- I know exactly what fasteners you are talking about and that is a great idea as well as one less thing for me to lose thank you !

Caveman- The chassis by itself is pretty damn light. . I have cut it up a great deal already (thats what we do best in the northeast haha) I have a lot of balast over the front tires already from all the weight i took out, just so I can meet weight minimum. So going lighter isnt really an option at this point because of those weight minimums . .

I have 4x8 sheets of aluminum that I could use for the underbody panel, they are very light . . Even if I added 20lbs to the car with the belly pan ( I highly doubt it would be that much) It wouldnt really a big deal.

My concern with lowering the car so much is that because the front end is already sealed off completely as it is, will lowering the front as low as possible make unneccessary downforce as well ?

My tire size is capped at 24.5 x9 and that is the size we all run. It is necessary for traction. . I run a 4.7final drive. . The car makes peak hp around 9600. I shift at 9900-10,000 and I cross the traps around 98-9900 . . So the gearing itself is pretty optimum at this point. Especially since I am crossing the traps a few hundred rpms after peak.


1 fast evo 2 - Thank you for your input! We no longer run the nhra or nopi rules . . We run a new series called nscra and a bunch of local races that carry the same rules . . We Can NOT use wheelie bars on this class . . I could get a dog box but the $6000 price tag is a little out of my budget right now. .
With the things I have proposed to do, I already have all the material and shop available to do it. . I wasnt expecting any of it to help me drastically but I'd like to see it help a little . . After all its like free HP. . Materials are basically free, its just my time . . So If i can make any of these things work (regardless of how nominal it may be) I'd take it !

[Blue]

1.) I know that lowering the front of the car will stop more air coming under the car.

There's a lot I could re-state here that I have in previous posts, but this is the most important point:

Air going under the car is what creates downforce, NOT preventing air from going under it.

What an air dam or lowering the front of the car does is increase the negative angle of attack, or alpha.  Drive down the road at 60 mph, stick your hand out the window and tilt it.  That's IT.  As a professional aerodynamicist, this is the best illustration I can offer and DON'T let anyone tell you it's more complicated than that.  It isn't.

"Preventing air from going under the car" is a combination of a good thing (negative alpha) and a bad thing (separation on the belly and tail).  If you can do it without adding weight, add a belly pan with a diffuser at the tail to reduce the separation and increase the negative alpha even more.  Then you can have the best of both worlds.  Lowering the whole car makes the effect greater at the risk of separation.  Where you go in height is more a function of how good your diffuser is at the tail and how much the extra drag costs you if you go too low and cause separation.

As for this drag racer, cut the weight.  F=ma or a=F/m.  Reduce mass (m), and a given power level (force, or F) will yield more acceleration (a).  Until you hit 150 mph in LSR or a 250+ trap speed, power to weight will dominate the aerodynamics.

[allmotorcoupe]

Ok that makes perfect sense. . . Thank you for that. I appreciate it very much