Light weight vs. Weight/Weight Ratio

[65Matt]

I've been wondering the same thing. My E30 is almost back on the road with a 5.0 in the engine bay. The car is stripped to the bone, and I'm thinking it's going to be less than 2500 lbs, but nose heavy with the engine.

[MattBimmer]

I think it was the Chief designer of Lotus that said adding power makes you faster in straight aways and reducing weight makes you faster everywhere.

I think weight distribution would be a better way for most drivers. I think ripping everything out of your car to shave weight should be for cars that are track cars and are not registered.

I know "because racecar" but I think having a versatile E30 thats good on the track but can also turn heads and roast mustangs on the street is the best route.

[BrewCity11]

This question was brought up when I was reading Sport Compact (back when they ran),

this thread needs the mag article where they chopped off body parts of a vette to see how much faster it was.

I had that issue. It was a clapped out Sentra with a huge body kit.

They started with a turn key ricer, and stripped it down in stages, ending with a sawzall chopping that thing down to the unibody. Granted, all they did was run the 1/4 mile for testing, but was fun to read nonetheless.

Some perfomance truck magazine did it back in the 90's too on a Chevy, removing the panels and bed, etc.

Would be great to see someone do testing with an E30 on a track.

[Nsquared97]

I think it was the Chief designer of Lotus that said adding power makes you faster in straight aways and reducing weight makes you faster everywhere.

Colin Chapman.

I had that issue. It was a clapped out Sentra with a huge body kit.

They started with a turn key ricer, and stripped it down in stages, ending with a sawzall chopping that thing down to the unibody. Granted, all they did was run the 1/4 mile for testing, but was fun to read nonetheless.

Some perfomance truck magazine did it back in the 90's too on a Chevy, removing the panels and bed, etc.

Would be great to see someone do testing with an E30 on a track.

I saw a video just recently that was the same thing, but with a C4 Vette. And they did do some handling tests, cars actually got slower after reducing so much weight, couldn't put the power down.

[2mAn]

great discussion guys. recently i was looking to build a RWD A1 chassis VW. I wanted to get to 50/50 weight distribution and after much research I realized that it wasn't the best way.

[priapism]

8 parts, start here:

http://www.motoiq.com/magazine_articles/articletype/articleview/articleid/1424/the-ultimate-guide-to-suspension-and-handling-part-1-wheels-and-tires.aspx

In short, they're both important.

[2mAn]

just wanted to bump this again for more discussion.

My car is an 84 with no power accessories except mirrors and steering and a 2.7i. Weighed it with a full tank and it came in at 2560 with me in it (160lbs). I was messing with my friends S50 E30 and we were pretty even. He had a passenger in his car. He was shocked that I had at least 500lbs on him and was able to hang with him. My goal is to shave more weigh off the front of the car, but Im also going to do some things that will add weight over the rear axle.

Does anyone know how much weight can be saved with a lighter hood? Any other ideas on how to shave extra weight

[Xat1cZ]

You save just as much weight with the hood as that hood is advertised to weigh versus stock..


It's not too difficult to find ways to remove weight if you use some imagination, make the whole front end; hood, fenders and bumper out of carbon fiber for example = profit?

[BlackbirdM3]

Yes, less weight is good, but weight balance is also very important. My Datsun for example has all its weight up front despite having the motor behind the front axle, and very little in the back. I have been fighting handling issues with it since day one. It doesn't understand the concept of understeer. I've got the biggest front anti-sway bar made for the car on there, 900lb springs, no rear sway bar and for a long time I ran the Nissan Comp race springs in the rear at 200 lbs (leaf springs). In that setup it was a handful when pushed hard. It was so bad that trying to autocross on street tires was a pointless exercise in doing donuts and hitting cones. It wasn't that the car wouldn't turn in, its that it would so so and just keep going. Applying power anywhere in the corner was a one way ticket to being backward. It was so bad the only area I could be on the power was a straight line. Corners and slaloms were out of the question. I then bought my first set of R compounds, a set of V710s. The tires made up for the lack of rear grip in a very big way and I had a couple near TTODs running with the PCA. (they were pissed.) Really the tires were just a band-aid for the underlying issue The back end of the car was too light and way to stiff. I tried traction bars, and those made things worse. I then found a set of Mono-leaf rear springs in Australia. I bought them and installed them to find the rear of the car was far more settled, but the 54lbs of unsprung weight I lost screwed my weight balance up even more. The car no longer hopped when I hit a bump on the road, but the car handled far better with a full tank of fuel, and would go away as the fuel burned off. My solution was 80lbs of lead ingots in the trunk. Now the car got fast as I found out doing VARA U at Buttonwillow to get my race license. During the second day there, VARA had a test day going with their other drivers so the track was pretty full. A friend who I taught me how to race criteriums on my bicycle was there in his BRE built 240 (Its not THE BRE 240Z, but one they built for someone else.) He would up and run away from me in a straight line, but in the corners I was faster. A few months later at Laguna Seca, I again proved that the ballast weight in the car was a good thing because through a corner, there were very few cars that were faster than I was. In a straight line, sure lots would up and run away, or be evenly matched, but through the corners I always found myself waiting for a hole to open up so I could pass someone. (There is no contact allowed in vintage racing. Besides do you want to have to pay to fix the 250 GTO Ferrari that is next to you? No, I didn't think so.) Still, as fuel burned off, the car went away so the only logical explanation is weight balance is very important.

Sure taking weight out of the car is a good thing but if it makes you slower through the corners because the balance is off, what is the point. Autocrossing, I've found that I can leave the lead out of the car but I have to run a full tank of fuel to keep the back end in line. There are cars out there that are very sensitive to weight balance.

My M3 on the other hand is just brilliant now and should get better with some anti-sway bars (I just have the stock ones with tire bushings at this point) and adjustments to the front and rear roll center. The front is really too low, and the rear wouldn't be hurt by going up either. Still, left/right transition is stunning, and I've only managed to spin the car once, on cold tires in the rain. It was just a long lazy spin.

So, where to loose the weight? Anything up high, and anything that rotates so, wheels and flywheel. From there, I'd say seats, a/c if you have it, exhaust.

Will

[dougie30]

How much weight do you think I would save by removing the sound dampening/heat shield from the engine bay and trans tunnel? Because mine is just crumbling away.

Also how much loader, and hotter do you think it would get in the cabin?

[Nick_S]

I had that issue. It was a clapped out Sentra with a huge body kit.

They started with a turn key ricer, and stripped it down in stages, ending with a sawzall chopping that thing down to the unibody. Granted, all they did was run the 1/4 mile for testing, but was fun to read nonetheless.

Some perfomance truck magazine did it back in the 90's too on a Chevy, removing the panels and bed, etc.

Would be great to see someone do testing with an E30 on a track.

One of my favorite articles from them.

Started with this. It ran 16.3 in the 1/4 mile, 0-60 in 8.6 seconds.


Then started gradually ripping things and measuring the performance gains. Till they finally ended up with this. Ran 14.3 in the 1/4 and 0-60 in 5.8.

[nrubenstein]

Less weight is good up to a point. Realistically, no one is going to achieve the kind of weight reduction that it takes to throw a BMW chassis so far off the curve that the weight balance is worse than the weight reduction without getting to fairly stupid and unlikely measures.

[LJ851]

Less weight is good up to a point. Realistically, no one is going to achieve the kind of weight reduction that it takes to throw a BMW chassis so far off the curve that the weight balance is worse than the weight reduction without getting to fairly stupid and unlikely measures.

True. One thing that is crucial to success is to re-spring and re-damp the suspension to match the new weight and weight balance. This is something those magazine strip the cars down "tests" don't do.

[Loupoz]

Just throwing it out there, anyone seen the topgear episode, where they all 3 get a 325i vert, and take them round a track? Jeremys is faster even though its an auto, but it has a great big concrete slab in the trunk.

And yes i know the cars arent identical, Jeremys is a Mtech, Hammonds have a bad suspension setup, and i cant remember whats the deal with captain slows.

[jlevie]

Coming into the thread a bit late...

For a track car (as in road course) the first step is to "add lightness" (Colin Chapman's words). Then you balance the car (corner and fore/aft weights). As far as possible the balancing is done by fiddling with the corner heights. Judicious placement of the minimum amount of ballast finishes it off. For an E30, try to get the fore/aft balance no worse than 51/49%.

The car should then understeer slightly on corner entry and oversteer on exit. You can fix either condition, but not without making the other worse. So a balance between two is the best compromise. Understeer on entry can be reduced by judicious trail braking.