So we ran about half the race without the rear hatch to save weight and I'm not sure whether or not it helped... some of my thoughts:


- Should we really be chopping weight out of the back of a FF at this point (already stripped interior)?
- Do we ever go fast enough to have compromised aerodynamics as a result of removing the rear hatch?

Anyway - just some thoughts

Less weight = go faster (technically) regardless of where you remove it from.

If you're worried about aerodynamics, you could try stretching a piece of plastic across where the hatch was, and duct tape the edges. That should reduce most of the drag you would experience.

right - I agree with the less weight ... but at this point.... without the rear hatch the balance of the car just continues to get worse... we also felt more understeer towards the end of the race but we think that was a result of the tire wear - but we still had a lot of tread left.... so I dunno.... lots of variables

Taking weight out of just the rear will make the car unbalanced and nose heavy. If you remove a ton of weight from the rear you need to rebalance the car. Driving a car with a 60/40 weight ratio split will just have the car nose dive into every corner.

it really depends on the coarse.

If your are racing on very high speeds with sloping turns, you would want to keep the hatch in place. You want to keep the car as balanced as possible.

But if you are on a short coarse with hair pin turns, it would be best to shift the weight of the car to the front to create lift off oversteer. In a fwd car, you want every opporutunity to lose weight and shave off some oversteer.

Just remember losing weight on the back of the car will make you lock up the front wheels easier. But on the other hand your car is now lighter to it will be able to stop shorter and is easier on your brake system.

We were on a very fast course - 2 mile course averaging well over 60 MPH - one turn you could hold 60 and higher.

We took the hatch off and I think we felt understeer - that could have been worn tires - dunno. The other question is aerodynamics and drag - I am thinking of throwing the GT-Four Spoiler on (with lifter blocks) That is supposed to be function over 100 - 130 Km/h which we would have easily seen on this track.

you'll lose traction as the chassis will flex a lot more, especially turning at those speeds, the best thing to do here is remove the glass of the hatch and replacing it with a lexan piece, the heaviest part of the whole hatch is the glass.

for those who want this but want it to be cute, get the CF hatch and lexan glass replacement.


the Lexan glass replacement you can do yourself if you know how to use your hands.

Well, you would be better off running an actual wing instead of the riser blocks. Run a CF trunk with lexan or just change your stock glass to lexan. I would also change your hood over to CF as well. Relocate your battery to the rear, or atleast behind the passenger seat.


What have you done to the car so far? Suspension? Wheels, tires, width?

A little off-topic, but isn't the car already terribly balanced at something like 60/40?

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I believe it is 58/42. Which is why weight from the front needs to be moved to the rear.

That's pretty terrible. Does anyone know how much the battery weighs then?

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Really depends on what battery you have. There are so many options that your weight could very. Could be anywhere from 40-60 or far less if you are running a smaller battery.

We are starting to scope creep here some...

remember, 24 Hours of Lemons - that means no shiny CF. Thats a one way first class ticket to the crusher.


The car:

http://picasaweb.google.com/mjcoury/RaceCar#


The battery at the moment is basically where the passenger seat used to be - this was just for wiring purposes and running out of time.

The car has brand new KYB shocks and Vogtland springs. ST165 Calipers and rotors up front, EBC Red stuff for pads. 15" steelies with Michellin Pilots

The car handled VERY, VERY well I was just curious about the negative effects of rear hatch removal - specifically did it increase the understeer we seemed to have developed by the end of the race. And the lifter blocks, while cool, are not practical... no one is taking a turn at 90 MPH to see if they work... so.. there is that

keep the hatch, bin the glass just stick in some plastic. you could also mod the bonnet to shift some weight from the front, cut out some if its underside frame.

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I see, I was not aware this was a Lemons build. In that case, just give the front end some speed holes, attach a huge 2x4 wing on the rear and call it a day.

to be honest, if i was the one building this car for the lemon race i would have got rid of the hatch a long time ago.

Its very heavy and anything less then 60 mph you will not have much aerodynamic benefits. the 7afe is already under powered that needs as little weight to pull as possible. Like i mention before more weight on the rear tires will give your more stabilty. But fwd cars don't necessarily use the common 50/50 split weight ratio for good handling. On tight circuits, When the car is accelerating majority of the time. Most of the 50/50 weight gets transfered to the rear. therefore you will only have 40% of the weight over your front tires. This cause reduce acceleration and slower turn in. A 60/40 split for a fwd is preferred by some; the reason is the majority of the weight is on the front tires to allow for better turn in,better brake response, more lift off oversteer because you don't have to wait for weight shift to get maximum tire weight/grip to the front tires.

But the ultimate answer to your question is. How do the drivers of the car respond to the modifications? If removing the hatch also removes confidence from the drivers then it is a useless modification and will slow you down. If your car is not tuned to your drivers, No matter well tuned the car is it will not set a fast lap time.

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I really like that one.

Well the biggest issue I see with removig the hats is the you dramatically reduce structural rigidness and the back will flex like mad. Not good for handling.

back end will lift and slip out

Replace glass. Add riser blocks.

This post has been edited by lagos: Oct 8, 2009 - 2:08 PM

replace glass as stated above, and get a carbon fiber hatch

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Fail.


I'm waiting for videos to see exactly how your car handled so we can help you out

cf hatch ftw.
then paint it
thats what im doing

Screw that, I'd leave it bare. CF sexyness FTW.

it would look down right idiotic on my car

That's true...unless you got one with blue worked in there.

Where are you guys finding CF rear hatches?

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VIS makes them. They've got them on ebay.

But, everyone is saying you'll lose structural integrity, but since you've got that crazy roll-cage I don't think you'll have problems with flexing.

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going from the stock hatch, to a CF one really wont affect SI much if at all, afterall, it is just held in place by the 2 hinges, and the latch.
its the equivlent of the hood in that aspect.

he can't fork out for a CF hatch as the car can be randomly chosen to be trashed so it would be a total waste, some sort of "fun" element in their race rules

i would also agree that the hatch can't benefit rigidity of the body as its not really got any proper anchorage points, plus he has a full cage inside

This post has been edited by Tom_SS2: Oct 10, 2009 - 8:19 AM