2g rear downforce needed!

[D_Eclipse9916]

I think the problem with the stock body is getting rid of lift rather than needing more downforce. The car definitely gets "light" on a stock body around 120 and up. Because of our slope of the coupe shape, I do wonder if a NASCAR style (again old style) would work wonders. Its used on Camaro Mustang Challenge cars with very similiar body lines. That is if you didnt want to get what is commonly referred to as "rice" wings (properly done they are far from it).

Absolute best way to do it? Get an immense APR or similiar (dont go ebay, these things actually require immense amount of engineering to produce a high downforce/low lift and MAINLY LOW DRAG wing).

Your problem however...definitely suspension setup and/or brake bias.

 

[LiquidX]

As mentioned above, I would recommend a battery relocation to balance the weight more evenly unless it's just a suspension issue.

 

[Flash]

The battery relocation to the rear would help, but it wouldn't be a drastic effect given his skill level. A much more experienced driver (ie Randy Pobst) could feel the difference. I think it all comes down the the OP checking his car out for problems and then trying different setup's at the track. I would like to see if Scott's recommendation for trying the stock rear sway bar helps.

 

[gsxitement]

I have the battery in the spare tire well. With the nascar style spoiler, I was thinking it would be taking advantage of the big round rear fenders these cars and use some of the air rolling down the sides of the car. I'm going to go over everything tomorrow after work and see what I can find out. Thanks for all the help!

 

[m3smgii2002]

Rolling on/off throttle will cause weight transfer to front and with stock suspension may appear as if the rear is lifting. Only race track testing with the suspension setup for that track (i.e. ride height, sprint rates, etc) and some data can verify where and more importantly how MUCH downforce you need. For example, on my '97 Talon TSi AWD (stock aero) on my home track I can actually get the FRONT to lift slightly at speed with the suspension setup for bouncing over chicanes at speed.

Also, wings cause drag and that'll slow you down too. So you need to be design carefully if you actually want to go faster! There are some decent books like "Going Faster! Mastering the art of race driving" that might help.

Cheers,
-M

 

[dieselsdad]

Sounds like alignment or even air pressures. I purposely use air pressure to get the rear to rotate. If you've done ANY changes to the braking system you might consider the brake bias or changing the prop valve. I race the first gen car and see NO need for a wing. What swaybars are you using? Is it AWD or FWD? If FWD you need a BIG rear bar and a teeny weeny front bar. What's your rear camber like? Too much rear camber can create this unsettled feel as well.

 

[gsxitement]

Rolling on/off throttle will cause weight transfer to front and with stock suspension may appear as if the rear is lifting. Only race track testing with the suspension setup for that track (i.e. ride height, sprint rates, etc) and some data can verify where and more importantly how MUCH downforce you need. For example, on my '97 Talon TSi AWD (stock aero) on my home track I can actually get the FRONT to lift slightly at speed with the suspension setup for bouncing over chicanes at speed.

Also, wings cause drag and that'll slow you down too. So you need to be design carefully if you actually want to go faster! There are some decent books like "Going Faster! Mastering the art of race driving" that might help.

Cheers,
-M

As I mentioned before I'm running K-sport coilovers all around with the full poly bushings in the rear and the RM Rear sway bar. I have some stiffening steps taken in the front. Not really sure that having weight off the front end while trying to turn is a good idea. As for the literature, Yes, it's a very good book, I have read it and I also went to the Skip barber racing schools at lime rock and have some karting and track day experience as well. I'm also aware of the downforce vs drag thing.

I'm going to make some changes while I wait for the track to open, and see what happens.

 

[drivemusicnow]

This sounds a lot like rear toe change under "rebound".

Basically, when you unload the rear (by loading the front) the suspension moves upwards. This change in "ride height" of the rear can effect the hub/wheel/tire with both camber gain/loss and toe gain/loss.

I'm not all that familiar with the rear suspension on the 2g, but is their some bumpsteer inherent in the design? If so this would likely be the culprit.

Anybody have a good picture of the rear suspension setup?

 

[gixxerdrew]

It doesn't sound like an aero-issue at all from how you described it. Actually take your car to the track, learn it, feel it and adjust accordingly.
The links posted above are not going to suit your needs for a wing that creates real downforce. Check out APR Performance for a rear wing.

It's not a downforce issue.

Also, all the "wings" linked below won't make any difference on a car. They're for looks (even though they look quite ugly in my opinion), and not for function. Look at real racecars for an idea for wing design. These have none.

These cars, for what they are, are actually quite stable at high speed (assuming a half-decent suspension setup, correct alignment, and good-condition suspension bushings). The 2g even in stock form has a very good Cd (around .28-.29).

Look elsewhere for your problem. You say you aligned it yourself and you're a mechanic. No offense, but I've been to places that specialize in alignments, and have great feedback, that should be nowhere near a car used for racing. Take it to a real alignment shop that sees more than mid-90's Corollas. If you're next in line after a Lotus Exige that looks like it's had more track miles than street miles, you've come to the right place.

What kind of tires are you running? I've had tires that were a little too wide for the wheel, and tires that had soft sidewalls, that produced an unnerving feeling much like you're describing. For a 225 section width tire, you should be minimum on a 7.5" wide wheel. For 235s, 8", and for 255s, 9". Buy a proper track-ready tire, like a Direzza Star Spec, Falken Azenis (not great for long track days especially in the summer due to overheating, but amazing sidewall stiffness), Toyo RA1, NT01, or any Advan from Yokohama.

Also, check your braking system. It sounds like it happens only under braking. I know there's also a lot of weight transferring off the rear, but I doubt that's the cause. Re-bleed the entire system and make sure the car doesn't pull under heavy braking. Try hitting the brakes hard from 60 mph and letting go of the wheel (make sure it's a smooth road to avoid any bump-steer input). The car should brake smoothly and straight. Does the back-end always come around the same direction? Disable ABS (pull the fuse). What tires lock first? These cars, with a close to stock braking system, tend to lock the fronts first, with the rears close behind (in my experience).

I've done several track days, braked hard from well over 120 mph, and have never experienced a feeling like that, unless I was trying to turn (not good), and I don't even have poly suspension bushings yet.

Don't ignore the front suspension either. How low is your car? The lower control arms in the front should be level with the ground, or point slightly upwards toward the car's centerline. The rear should then be slightly higher or level with the front. Any lower than that and you're negatively affecting the car's suspension geometry.

Im going to agree with these guys... also be careful DSMs are known to have a very agressive rear brake bias especially if you start losing weight back there. But with that said, Im working on a new wing for APR Performance which has been optimized in CFD and will make a completely ridiculous amount of downforce it should be out this summer.

 

[LiquidX]

Im going to agree with these guys... also be careful DSMs are known to have a very agressive rear brake bias especially if you start losing weight back there. But with that said, Im working on a new wing for APR Performance which has been optimized in CFD and will make a completely ridiculous amount of downforce it should be out this summer.

Can you make it look stock ?

 

[JD98GSX]

I bought a JSP "blade" carbon fiber wing, and it is used on several time attack cars. it is adjustable, and light weight. it also come with either 5 inch pedistals or 10 inch pedistals. I went with 10 so I could grab more air to push down.

 

[eclipsegsx1736]

I bought a JSP "blade" carbon fiber wing, and it is used on several time attack cars. it is adjustable, and light weight. it also come with either 5 inch pedistals or 10 inch pedistals. I went with 10 so I could grab more air to push down.

Any pictures of the car?

 

[JD98GSX]

I will throw some pics on here in a little bit. It is pooring outside. So keep an eye on this thread and i will get them on asap. it looks good.

 

[snowborder714]

Can you make it look stock ?

When you want it to look like stock, you know you care more about looks than performance.


Drew, I look forward to seeing what you've come up with. Definitely keep us updated

 

[rx7ttlm]

My best guess is your problem stems from something other than your rear downforce. If your bushings are shot or your alignment blows, or soft side walls your car will feel like it wonders at all the wrong times. Shocks also play a big part in controlling weight transfer, combine blown shocks with the rear toe decreasing under braking (the geometry is retarded) this all adds up. But its rare that I hear someone complain about a awd car being to loose. Its also a function of driving, if you do something silly like chop the throttle mid corner any car will let you know its not the right thing to do somehow. Or if you dicked up air pressure that will do it too. To low will make the car feel like its numb and do silly shit as the tire rolls over, and to high you will get good initial grip but as the tire comes up to temp it will feel greasy

and i am going to freak out if I see another "race" wing that is fing huge with no front downforce being added.

 

[LiquidX]

When you want it to look like stock, you know you care more about looks than performance.


Drew, I look forward to seeing what you've come up with. Definitely keep us updated

What's wrong with looking stock??? I'd rather have the thumbnail than a shopping cart handle IMO especially if it become more performance than for looks while still looking sleeper.

and i am going to freak out if I see another "race" wing that is fing huge with no front downforce being added.

You shouldn't worry about the no down force concern with Drew. It may look like an aftermarket wing though but it will have function.