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Acceptable weight loss

Hi Ned,
I've done most of the things that you've done plus a few of the things you propose and I can say that it does make a real difference. My only caveat is that you need to be a reasonable driver to be able to appreciate that difference. A lot of people on here don't get the fact that the improvement comes from the sum of incremental gains rather than from just doing one particular thing.

I also have a similar mission to you, in that I have kids and need the rear seats to be accessible and functional. In essence though - go for it - it's a much better car when it's lighter. It feels far more agile, - it's not all about power to weight ratio, it's the fact that it will change direction quicker and stop quicker too, which adds up to a much more fun driving experience.

Stuff to do..
1. Lose the spare wheel and tool kit. If you must, take a compressor and a can of gunk, and your towing eye.
2. Don't remove your front impact bar, as the towing eye screws into this. If you can make other provisions then great, otherwise hang onto it. It's not that heavy anyway. Do remove the rear one.
3. Any weight lost from the rear of the car will be of greater benefit to the handling balance than weight lost from the front, so the lighter cats/exhaust and wiper delete are all steps in the right direction.
4. Lightweight battery - I went for the same battery as ELA but found that because the car lived outside, the battery got too cold to start the car on winter mornings for the school run. The lithium cells in the battery need to be above about 6 degrees C to give enough oomph to start the car. You can warm up the battery by running some electrical devices such as the lights and radio, and then turn them off again before attempting a start. This worked for me many times, but it was also frequently a gamble as you could easily drain too much juice out of the battery when warming it up and then not be able to start anyway. I have an Odyssey PC680 on the bench which is about to go into my aeroplane, and I might try it in the car to see how it goes.
5. LWFW - ELA reckons this is the single biggest game changer of the character of the car. I don't have one yet, but I probably will go for one at my next clutch change. The centre plate needs to be a sprung one from a 993. The cheapest way to get one is to buy an old worn out one and get new friction surfaces riveted on. I found a place in Bordon, Hampshire that would do it for £90 and give me any friction coefficient they had to choose from.
6. Wheels - I went from Sport Design GT3 wheels to 993 10-spokes as they were supposed to be the lightest OEM wheel, but the difference in the driving experience was really very minor, so perhaps hold off on wheels until other gains have been realised. The weight difference was minor and most of that difference seemed to come from the tyres rather than the rims.
7. Roof - The non sunroof steel roof weighs 7KG and costs about £400, the sunroof version with all the sunroof gubbins is somewhere around 20KG, and a carbon roof costs £1000, and weighs 3KG. When I do my roof, I'll be going for a steel panel. If you go for a composite roof, don't take any cr@p from cretins who think a bonded in composite panel represents a weak link in the car and will fall off in a crash or make the car less rigid. It makes the car more rigid.
8. Radiators - remove one of the fans. The comment earlier about it not being a Mezger/GT3 and therefore the mod not applying doesn't hold water. Heat production is proportional to HP production. A Mezger producing 400HP has a 33% greater heat output than an M96 at 300HP, so has a 33% stronger argument for having fans on both radiators(yeah, yeah, I know there's a centre one too). You can easily lose one of the fans. I took off the RHS one in the pursuit of better side to side weight distribution. I have an LTT and the temperature rarely goes above 81. I would only put the fan back on if I was expecting to be regularly stuck in very bad traffic on very hot days.
9. Washer bottle - It's pretty big -run down the contents until the low washer bottle light comes on the top up just enough to put the light out.
10. Take out any floor mats. They weigh a fair bit.
 
Hi Martin, that's some list. I'm on for most of it but I've no intention of touching the roof. The air cons going so I want the sun roof as I always use it, and besides, it's just not in the budget even though I am going for a coat of paint.

On the flywheel. I bought a sachs clutch a while ago to be fitted when I get that far in the build. Can I not use it? I was under the impression it'll fit straight onto a lwfw.

I'm interested in the battery as I'll definitely do something here. What battery do you have in atm? Mines purely a toy, garaged and on trickle charge if needs be.

Sorry, I can't really think straight atm as I've been up all all night with the birth of my new baby girl.
 
Just googling my current battery weight, apparently it's 22.5kg :eek:
A drop to 7kg for an odessey would be a good start.

The radiator fan delete is on the cards as well :thumb:
 
Congrats on your new daughter!!!

I currently use a normal car battery, though slightly smaller than std spec (about 60ah rather than 70ah). If you're feeling flush you might consider trying two of the lithium batteries together. They weigh next to nothing and two might actually make it reliable and still be a good deal lighter than a PC680.. I'll let you know how I get on with the PC680, I'm not sure it has the capacity to do the job, however my plane has a six litre engine and I've been told the PC680 will spin it like a top by other owners.

I'm not sure of the precise reason for needing a sprung centre plate, but you're losing the damping/springing that the dual mass FW provides, so that's probably why. You'd probably get increased wear or driveline shunt if you went with a solid centre plate. I believe you're fine to use whatever cover plate you got with your Sachs clutch kit.
 
Martin996RSR said:
Hi Ned,

8. Radiators - remove one of the fans. The comment earlier about it not being a Mezger/GT3 and therefore the mod not applying doesn't hold water. Heat production is proportional to HP production. A Mezger producing 400HP has a 33% greater heat output than an M96 at 300HP, so has a 33% stronger argument for having fans on both radiators(yeah, yeah, I know there's a centre one too). You can easily lose one of the fans. I took off the RHS one in the pursuit of better side to side weight distribution. I have an LTT and the temperature rarely goes above 81. I would only put the fan back on if I was expecting to be regularly stuck in very bad traffic on very hot days..

You seem to be missing the point, how often have you heard of cracked heads on a Mezger? - While on a 3.4 M96 its common place, controlling of the coolant temp on these engines is critical, hence the exceptance of the addition of a LTT being worthwhile, removing a rad fan on a daily driver to save circa 4kg is madness IMHO.
 
Just googling my current battery weight, apparently it's 22.5kg :eek:
A drop to 7kg for an odessey would be a good start.

The radiator fan delete is on the cards as well :thumb:
 
True madness lies in declaring facts without empirical evidence to back up assertions. If you've already tried removing a fan and found your cooling to be inadequate then you were either in a traffic jam in a heat wave, or your rads are clogged with silt and bunged up with leaves. However, if you've never tried removing a rad fan then how could you possibly know?

I've had only one rad for over six months and have seen no downside so far. It's only madness if there is evidence that it causes the coolant temp to rise beyond acceptable limits. I totally accept that inadequate cooling will damage the engine, but the point is that removing one rad fan does not cause unacceptably elevated coolant temperatures.
 
I have to admit I'm with Martin on this one. I've never noticed my fans on and I'll also be ditching the air con condensers so air flows gona be up. Also the ltt will be going in with a new water pump
 
I run a centre rad with a GT2 chimney and Cup front bumper vent, LTT and the two standard rad's with one of the a/c condensers removed to accommodate better flow, rad cowls have been removed to elevate air stacking, inner arch liners modified.

In addition an FVD motorsport sump that gives an extra 0.6L of oil and is finned to improve air flow over its exterior. – Secondary air pump has been removed to improve airflow around the engine bay, hydraulic engine mounted power steering pump has been replaced with a frunk mounted 997 Cup item, which again allows more airflow in the engine bay and removes the heat the pump produced.

With all of the above, when inevitably stuck on the M25 on my way back from Brands, the fans regularly kick in and I see temperatures significantly higher than your quoted 81. – In fact I see higher temperatures when stuck in traffic than I do when tracking the car.

Ohh and did I forget to mention that I have indeed removed, and subsequentially, refitted said rad fan! – its MADNESS!! But each to their own.
 
Ya have a fair point. Experience is always good.

On the frunk mounted ps pump. Is it an Opel pump? I've always been keen to know more. Do you by any chance have the air con deleted? Is there an off the shelf belt anywhere for deleting ps pump and air con pump?
 
Hi Crash, I don't think we're at odds at all. I originally wrote that I would only keep the second fan if I expected to be stuck in traffic, and you're arguing that in your experience the fan you kept ws necessary to keep from overheating whilst stuck in traffic on the M25 on the way home from Brands. I reckon that's the same viewpoint isn't it?
 
Anecdotal data point - I've crawled my 996 through central London rush hour traffic when its 30 degrees outside, and never for the water temperature needle as high as repeated laps of Brands Hatch got it.
 
Robertb said:
Alex said:
Petrol's 0.7kg per litre (sorry for being pedantic :oops: )

Not at all... interesting, not realised it was lighter than water... guess it makes sense as petrol floats on the waters surface.

I just checked. The internet told me that "the density range of petrol is 710 to 775 gram/ litre at 15 degree celcius. Thus weight of 1 litre of petrol at 15 degree celcius varies from 710 to 775 grams."

It still makes a difference though as all of that weight is up front in a 911.
 
I like these weight threads, even if what is meant by 'acceptable' is entirely subjective.

The point has been made above, but the location of the weight is also important, as well as the actual weight. I suspect that the easiest gains are the spare, tools, rear seats, mats etc. (all the removables), and the best gains are around the rear (the exhaust and cats mainly), as well as unsprung weight such as suspension, brakes, rims, and tyres.

I wouldn't have the patience to remove the carpet and the sound deadening, even if it is heavy, but stock seats are really heavy. And I'd stick to a normal battery for the winter. But there are good losses to be made.

For example, in the other car, the weight losses include the rear seats (-17kg), front buckets (Sparco Evo2 with mounts are c 8kg each, together -52kg), à–hlins R&T suspension (which is about 10kg lighter than Bilstein B14s), TTV lightweight flywheel (-6kg), lightweight rims (-20kg), Quaife (-1kg), rear control arms (-1.2kg), but then again I have added a strut brace, an aluminium skid plate, a BBK and a thicker rear ARB, so who knows where I have ended up, maybe 100kg down?
 
Thanks for the input guys.

MaxA
What is the other car?
I'd be keen to see more on the seats. My 'acceptable" term wasn't very clear but I have a few things I need to abide by. I need the rear seats as my kids love a spin out in it, it's a big sense of occasion for them from the daily. I'm open to all weight reduction ideas but I need the rear seats and access. I had ruled out fixed buckets until I read ELAs thread where he made the seat bases and rails to suit so he could get the seat to move far enough to let an adult in which is more than plenty. I also need to think about fitting a child seat in the front but I'm sure I can get round this.
Safety issues like air bags are a keeper though I removed the drivers to fit an omp wheel.
On the carpet, is there much to be gained by taking out the sound deadening but retaining the carpet? Is this just a no go as the carpet won't sit right then?
 

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