Race car build - weight loss

[Jerry Can]

Can anyone give me some specific examples of how much weight they were able to remove from a hot hatch/saloon type car whilst turning it into a race car?

I'm specifically interested in a post 2002 car that would have had more modern secondary safety items like door bars and air bags as well as A/c sound deadening. Is 150kg possible?

[AdeRacing]

After gutting the interior etc or after that stage? Easy to lose well over that amount starting from a road car. Don't forget you'll be adding a fair bit of weight back in with a roll cage but 150kg should be no problem. My 1998 Puma is nearly that under standard and didn't have half the bells and whistles of the new (2009) car I'm building. I swear the seats alone weighed 150kg between them with the electric and bags in them.

Sound deadening is always the shocker. I didn't weigh with the new car but with the Puma it was nearly 30kg.

[BMR]

I got my fiesta st race car project less the seats etc so not sure how much they account for.

I removed all the sound deadening and weighed it - 25kg it accounted for. Each door bar was about 6kg from memory. Heater unit must be a few kg too as it came out as well.

Just to note the race car with me in it at under 100kgs is 1100kgs approx. The kerb weight of the standard car is 1137kg.

[Jerry Can]

AdeRacing said:

After gutting the interior etc or after that stage? Easy to lose well over that amount starting from a road car. Don't forget you'll be adding a fair bit of weight back in with a roll cage but 150kg should be no problem. My 1998 Puma is nearly that under standard and didn't have half the bells and whistles of the new (2009) car I'm building. I swear the seats alone weighed 150kg between them with the electric and bags in them.

Sound deadening is always the shocker. I didn't weigh with the new car but with the Puma it was nearly 30kg.

From standard road car to the point of adding back in a cage. Yes I could imagine the seats are heavy.

[Robmarriott]

Is there a minimum weight and is ballast mentioned in the regs?

The reason I ask that is that most series' have a minimum weight in each class and a lot of them will specify that you're not allowed to bolt ballast in, they can also be very strict on cutting metalwork out so if you do you'll want to do it where it can't be seen.

What car is it? There's always a lot of weight in things you wouldn't consider like seat brackets, which you can get out with a spot weld drill, the alternator/AC bracket is often combined and if you ditch the AC, you might be left with surplus metal on the bracket.

Wheels are a big thing if the regs allow you to change them.

Passenger airbags are often forgotten, the battery weighs a load and you can normally get away with a smaller one, same with electric windows, you can bin the mech on the passenger side for a kilo or so, and then wedge the window up with something.

But, like I say, just be careful, the series I built my Clio for was very strict on ballast (ie, it was prohibited) so if you went too low, you would have had to be creative with where you hid the weight you needed to get it back up!

[andye30m3]

My E36 318is race car weighs in the region of 1080kg, manufacturers kerb weight is 1240kg and it has a reasonable cage in it not a cheap 6 point. So depending on the car I'd expect -150kg is achievable.

probably need to be a bit careful with the specific regs your running to as my car has GRP panels and healight blanks which wouldn't be acceptable in many series.

I'm still in an ideal world looking to remove a fair bit more weight as I'm currently running with about 135 bhp / ton in a class where your allowed 180 bhp / ton.

[Jerry Can]

It is a power to weight formula, 145bhp/tonne. Road car is 1080kg and power 138hp. Not far off, I reckon I need it down to about 950 exc me, and a small power hike to get to the number.

[PhillipM]

If it's a power to weight formula you'll be faster leaving it heavy and finding more horsepower usually, especially with fairly low power figures like that, as most places drag will be a big issue.

[Steve H]

There's usually a sweet spot for power/weight, see what your competitors are doing - especially the front runners .

I would normally say losing 150kg should be fairly easy but it sounds like your car is pretty light in the first place which suggests it's not got as many options for reductions?

[Robmarriott]

Assuming a roll cage is mandatory, and with the caveat of not knowing what the car is, I'd say you'll struggle to get it down 100kg with a roll cage.

My Clio started at 1010kg with an almost empty tank and full interior.

When it was weighed post race, it was 1055kg - all the interior removed, lighter wheels, no aircon or associated bits, no airbags, one seat (on fixed mounts with the original seat mounts removed), lighter battery, bits of metal cut out behind the bumpers where it couldn't be seen... The car was weighed with half a tank and a driver who was 65kg. It had a 6 point cage and a plumbed in extinguisher as per the regulations.

So, working back from that, the car was about 915 with no fuel, no driver and no roll cage, only 95kg less than stock with a lot of stuff removed.

If your car is 1080kg, I guess it's similar in size (138bhp makes me think 206GTI?)

It's going to be tough unless you can swap panels for lighter ones, I couldn't do that with the Clio (wings are plastic anyway), the regulations prohibited it.

[avenger286]

Don't know if this will help but this is what I have removed from my rally car so far with scale recorded weights.

Front seats 38kg
Rear seat 15.5kg
Parcel shelf 1kg
Rear cards 2kg
Boot carpet and plastic 1kg
Rear belts and fixings 4kg
Spare wheel 13kg
Wheel brace and tools 2kg
Radio 1kg
Sun visors 1kg
Front belts and fixings 4kg
Plastic door surround 1k
Front mats and floor sound proofing 5kg
Head lining 2kg
Carpet 3kg
Front airbags 5.5kg
Rear wiper motor 2.5kg
Behind dash sound proofing 11kg
Floor sound proofing 4kg
Seat brackets and rear boot brackets 5kg

Total 121kg

Car before started at 1010kg and 130bhp as standard

[NJH]

PhillipM said:

If it's a power to weight formula you'll be faster leaving it heavy and finding more horsepower usually, especially with fairly low power figures like that, as most places drag will be a big issue.

OP also bear in mind that a lot of weight removal, especially of the easy kind, will come from the middle of the car and the other end to the engine. It's not unusual for stripped track/race cars to have worse weight distribution because the most difficult thing to loose weight from is the engine.

OTOH an old trick is to strip the weight down under a class minimum and then add things back in and onto the car to help the weight distribution. Many seem to run the maximum ballast they are allowed to for example.

[bucksmanuk]

PhillipM said:

If it's a power to weight formula you'll be faster leaving it heavy and finding more horsepower usually, especially with fairly low power figures like that, as most places drag will be a big issue.

Not necessarily, I’m eligibility for a one make one-class championship, with a strict power to weight ratio. The weight is determined by the engine power. The current vogue is to de-tune the engine and have the car lighter.

Although on the Silverstone GP loop, I suspect most will wish they had gone the other way.

[Jerry Can]

thanks for the replies, food for thought

[mat205125]

NJH said:

PhillipM said:

If it's a power to weight formula you'll be faster leaving it heavy and finding more horsepower usually, especially with fairly low power figures like that, as most places drag will be a big issue.

OP also bear in mind that a lot of weight removal, especially of the easy kind, will come from the middle of the car and the other end to the engine. It's not unusual for stripped track/race cars to have worse weight distribution because the most difficult thing to loose weight from is the engine.

OTOH an old trick is to strip the weight down under a class minimum and then add things back in and onto the car to help the weight distribution. Many seem to run the maximum ballast they are allowed to for example.

It's always gonna be a compromise, and what might work at one track might not work at another.

The logic is sound that if the nature of the track (and car) was fast flowing turns and long straights, then tuning for more power to punch through the air, and dragging some additional weight, would be the way to go. If on the other hand you needed to dance around a tight and twisty track like Cadwell park (for example), then as light and nimble as possible, with modest power, would be preferable.

Ideally, you'd always make the car as light as possible, and then ballast back up to weight my putting components (tanks and batteries) in key places, and adding material to get the best centre of gravity and distribution as possible.

[drmotorsport]

In the case of my race Puma which was 1035kg in road trim including the usual modern safety and comforts; i've been able to get that down to 830kg including adding in a fairly substantial rollcage. It's quite easy to remove the bulk of the weight for free, but I went further and replaced some parts like windows, bonnet and tailgate with lightweight items.