A much lighter X1/9?

[Bjorn Nilson]

I've done the "obvious things" and reduced the weight to 820 kg/1850 lb so 150 kg/330 lb removed. If I ever will finish the 128 SL project (that easily can be lighter than 700 kg/1543 lb), I will build a 100% race X. I have an idea of stripping everything except the cockpit, building a tube frame, and covering it with a Dallara kit I've found for a bargain. I guess and hope it will be lighter than 700 kg.

 

[carl]

I have removed the obvious, bumpers, entire interior including the very heavy dashboard. Also removed the entire headlight assembly. Tube header and turbo muffler got rid of the stock exhaust and the dual IDFs weigh less than the stock FI. I unbraced and drilled the rear trunk lid and knocked four pounds off that. I could gut the doors but the car is parked outside so I can't remove the windows. I don't carry a spare but let vanity get in the way and added a rollbar! I'm around 1800 pounds.

 

[Steve Hoelscher]

Most of what I did on my DSP X1/9s was what was allowed by the classification rules. Light battery, removing optional ecquipment, spare tire/jack, light weight seats, etc... I could run any alternator so I swapped to a small/light hitachi. It was only 3 lbs. I had the lightest X1/9s on grid at the National Championships. At the time my '80 1500/5 spd car was 1925 lbs, fitted with 13x8.5" wheels and 225/45 tires. My previous '74 was right at 1800 lbs.

I have built a couple of mod class autocrossers that were very light. 1200 and 1400 lbs. But we cut out everything that wasn't necessary to making the car go around an autocross course. They were not streetable cars.

 

[bruinbro]

Most of what I did on my DSP X1/9s was what was allowed by the classification rules. Light battery, removing optional ecquipment, spare tire/jack, light weight seats, etc... I could run any alternator so I swapped to a small/light hitachi. It was only 3 lbs. I had the lightest X1/9s on grid at the National Championships. At the time my '80 1500/5 spd car was 1925 lbs, fitted with 13x8.5" wheels and 225/45 tires. My previous '74 was right at 1800 lbs.

I have built a couple of mod class autocrossers that were very light. 1200 and 1400 lbs. But we cut out everything that wasn't necessary to making the car go around an autocross course. They were not streetable cars.

Forgot to add battery change to my list of bolt ons. It’s a biggie.

 

[Rupunzell]

LeMons car is about 1600 pounds with full cage, added structure for seat belts, Mazda 12A PP rotary, Porsche 901 gear box. Body covers are thin fiberglass, 15x7 alloy wheels...

One of the drivers has a Porsche GT3 track day car, very surprised at how good the LeMons X went around the track.

Lower weight makes everything work better. One set of tires last the entire race weekend, car is easier to drive/control and lower stress on the chassis parts and all that.

There are very few 2,000 pound or less two seats produced today. Majority of two seaters are near 3,000 pounds or more. Moto brands add lots of power, huge tires, power assisted steering and brakes, electronic "driver aids" and all that to achieve performance numbers (extremely marketable).. little is ever mentioned about the driving experience of a 3,000 pound + moto.


Bernice

 

[Bobkat]

I've done the "obvious things" and reduced the weight to 820 kg/1850 lb so 150 kg/330 lb removed. If I ever will finish the 128 SL project (that easily can be lighter than 700 kg/1543 lb), I will build a 100% race X. I have an idea of stripping everything except the cockpit, building a tube frame, and covering it with a Dallara kit I've found for a bargain. I guess and hope it will be lighter than 700 kg.
View attachment 76254

Does anyone have the weight of a Dallara kit? There is so much variations in FG construction that weights can get out of hand and more than the metal they replace.

 

[Bjorn Nilson]

Does anyone have the weight of a Dallara kit? There is so much variations in FG construction that weights can get out of hand and more than the metal they replace.

Mine is stored on the attic so I can't easily weigh it so I can't help. I think the weight also depends on manufacturer/brand. Hoods and doors would probably reduce a lot of weight but fenders not so much.

 

[autox19]

On and off target. "boostedboiz" youtube channel have been working on a tesla plaid. they stripped it down to a tesla cart loosing over 700 lbs. the funny part (and you can watch the vids to details) it wasnt faster in the 1/4 mile by much. the top speed suffered with no body. they since went to a wind tunnel and put on a make shift body. had faster exit speeds for sure. The other part was it actually has issues getting traction with the missing weight until the computer started compensating. still a crazy fast car for being as heavy as it it.

Odie

 

[Rupunzell]

On and off target. "boostedboiz" youtube channel have been working on a tesla plaid. they stripped it down to a tesla cart loosing over 700 lbs. the funny part (and you can watch the vids to details) it wasnt faster in the 1/4 mile by much. the top speed suffered with no body. they since went to a wind tunnel and put on a make shift body. had faster exit speeds for sure. The other part was it actually has issues getting traction with the missing weight until the computer started compensating. still a crazy fast car for being as heavy as it it.

Odie

Not just weight reduction, it all works together as a system. Alter one part of the system, the entire system behaves different. This is why focusing on a single aspect often produces non-uniform results and unbalanced results.

Reduced weight means less weight pressing down on the tires, this reduces overall traction. Modern racer cars compensate for this by aero design excellence.. Aero has it's own set of trade offs from how much road speed is needed for the aero to work to how much added drag -vs- downforce and Much Much more.. Where the down force is applied on the chassis alters chassis dynamics and is road speed dependent... or one of the aspects of why aero centric race cars can be difficult to drive. There is more, tire temperatures and tire grip (intimately connected) are other factors to deal with. For race tires, each heat cycle degrades tire traction..

Traction_Grip and Control are two of the Most Important aspects of moto dynamics. Far more important than straight line power or "go"..

This is why simply adding more "power", lower weight and altering just one aspect of any moto does not work.. and why original designs must be respected and deeply understood before doing any alterations from the original design..


Bernice

 

[carl]

That's the nice thing about doing a diet on an X. From the factory, they were underpowered and by today's standards under braked.

 

[JimD]

I take a couple hundred pounds out of my X every time I get out of it.

 

[bruinbro]

I take a couple hundred pounds out of my X every time I get out of it.

I know this was a joke, but a real and significant weight reduction is to lose personal weight.

 

[JimD]

I know this was a joke, but a real and significant weight reduction is to lose personal weight.

I know and I have lost thousands of pounds in my lifetime. The struggle is real.

 

[tigeravg]

I've done the "obvious things" and reduced the weight to 820 kg/1850 lb so 150 kg/330 lb removed. If I ever will finish the 128 SL project (that easily can be lighter than 700 kg/1543 lb), I will build a 100% race X. I have an idea of stripping everything except the cockpit, building a tube frame, and covering it with a Dallara kit I've found for a bargain. I guess and hope it will be lighter than 700 kg.
View attachment 76254

Bjorn, you might want to view "Davide Cironi's" video on a full blown race X. They get it to 559kg. Of course the only part of the car that is still X1/9 is "most of" the cockpit. The rest is hand fabricated, with a motorcycle engine. Insane car.

 

[Ulix]

I know this was a joke, but a real and significant weight reduction is to lose personal weight.

That is true, of course.
But also sooooo much less fun than making mods to your car.

 

[carl]

Nobody likes to ride in my X so I often think of removing the passenger seat.
Talking about...er...biological weight in an X, I can definitely tell in my Miata when I'm hauling an adult sized passenger...my shop pup not so much.

 

[BiTurbo228]

I've done some rough calculations around the density of various cars which does corroborate that X1/9s are a little leaden as standard. The calcs are pretty rough, but they're about 144kg per m2 which is on par with the density of a lot of 90s cars (about when density peaks). Things like the NB MX5 after they put more crash protection in.

If they were built like an NA (so lightweight, but not necessarily floppy) they'd be spot on 800kg (131kg/m2). If they were built like a Spitfire they'd be 775kg (127kg/m2 for a MkIV).

I've been taking more of a 'build it like an NA MX5' approach with mine rather than 'build a racecar for the street'. It's Uno Turbo swapped so that's not helping it, but was 921kg with a full tank but without driver when I corner-weighted it. Since then I've:

Removed the spare wheel (-10kg)
Swapped in a Punto GT gearbox with custom subframe (all evened out to +2.1kg)
Added an oil cooler (+2kg)
Replaced the front metal bumpers with fibreglass ones (-0.5kg)
Deleted the luggage tray (-3.6kg) though likely will remake another in a lighter material
Removed the speakers (-0.8kg)
Whipped the bumper bolts out of the rear (-0.11kg)
Swapped in an alloy radiator with a tubular frame (-2.6kg)
Swapped the original fan for 2x modern slimline ones (-1.8kg)
Swapped the Mk2 roof for a Mk1 version (-2kg)
Changed the sound deadening in both footwells for dynamat (-2.4kg)

There's plenty left to do, but we're hovering just above 900kg at the moment. I've got about 30kg more identified without doing any significant chopping (FG boot, bonnet and engine cover, lexan rear window, lightweight flywheel, tubular manifold, half-sized washer tank, lightweight alternator, some other bits and pieces). If I can get it down to ~800kg I'll be overjoyed, but finding 70kg more without significant chopping will be difficult (not afraid of significant chopping, just don't have a place to repaint it afterwards!).

 

[Rupunzell]

I've done some rough calculations around the density of various cars which does corroborate that X1/9s are a little leaden as standard. The calcs are pretty rough, but they're about 144kg per m2 which is on par with the density of a lot of 90s cars (about when density peaks). Things like the NB MX5 after they put more crash protection in.

If they were built like an NA (so lightweight, but not necessarily floppy) they'd be spot on 800kg (131kg/m2). If they were built like a Spitfire they'd be 775kg (127kg/m2 for a MkIV).

Real simple, the exxe was designed, produced and tested to pass the proposed 50Mph frontal barrier and 80Mph rollover test for occupant survivability. The only other vehicle from that era that passed this DOT proposed requirement was the Volvo 240 series. None of the Mazda MX5's NA/NB, Triumph Spitfire or similar convertibles can or will pass this proposed DOT requirement.

Or why the exxe has such an excellent chassis in terms of rigidity, stiffness. Know the exxe chassis was derived from the Lancia Stratos by the same designer/engineer of the Lancia Stratos. Both Stratos and exxe share a much more than is believed or expected.
When the exxe chassis is directly compared to the MX-5 NA/NB. the MX-5 comes up flexi and no where near as crash survivable as the exxe. Comparing the exxe to the Triumph Spitfire, the Spitfire is worst in terms of chassis stiffness/rigidity than the MX-5 and he Spitfire as delivered has swing axles in the rear which should have never been allowed or produced.

Having been around a MX-5 for decades now, the MX-5 remains a best Meh... for a very, very long list of design reasons..

I've been taking more of a 'build it like an NA MX5' approach with mine rather than 'build a racecar for the street'. It's Uno Turbo swapped so that's not helping it, but was 921kg with a full tank but without driver when I corner-weighted it. Since then I've:

Removed the spare wheel (-10kg)

Easy.

Swapped in a Punto GT gearbox with custom subframe (all evened out to +2.1kg)

Ok.

Added an oil cooler (+2kg)

Ok.

Replaced the front metal bumpers with fibreglass ones (-0.5kg)

Easy.

Deleted the luggage tray (-3.6kg) though likely will remake another in a lighter material

Easy. If weight is of that much a concern, delete the cover between the power train compartment and rear boot (trunk) and it's related thermal insulation.

Removed the speakers (-0.8kg)

Easy

Whipped the bumper bolts out of the rear (-0.11kg)

Easy

Swapped in an alloy radiator with a tubular frame (-2.6kg)

Ok.

Swapped the original fan for 2x modern slimline ones (-1.8kg)

Ok.

Swapped the Mk2 roof for a Mk1 version (-2kg)

Easy or simply remove the insulation from the MK-2 version.

Changed the sound deadening in both footwells for dynamat (-2.4kg)

Ok.

There's plenty left to do, but we're hovering just above 900kg at the moment. I've got about 30kg more identified without doing any significant chopping

Do not simply "chop" as there are important structures that must be considered.

(FG boot, bonnet and engine cover, lexan rear window,

FG or Composite (CF) Bonnet (hood), Rear trunk cover, doors, all add up for weight reduction quick. Trade off for going to a FG bonnet (hood) is front crash survivability same applies to the doors which are a LOT heavier than believed. Also door glass is no light weight.

lightweight flywheel, tubular manifold, half-sized washer tank, lightweight alternator, some other bits and pieces).

All these bits add up for weight reduction.

If I can get it down to ~800kg I'll be overjoyed, but finding 70kg more without significant chopping will be difficult

70Kg reduction is not that difficult.. given the items listed are done.

(not afraid of significant chopping, just don't have a place to repaint it afterwards!).

Again, don't simply "chop"..


Bernice

 

[Steve Thomas]

built like a Spitfire

so badly, so nasty, so cheap, so flimsy. If that is what you want an X to be, go buy a Spitfire instead. Yeah people love them which tells you a lot about "people"

If want to do serious weight reduction - stop thinking in lumps. Look at every single part at its lowest level [look at parts, not assemblies]. Make every part lighter or preferably, leave off. Think about each part. What does it actually do? Is that function something you want? Could it be done diferently [lighter]? Don't fuss about big weight reductions - just take weight of everywhere you can. You will be amazed at the total you can acheive but lots of tiny changes.

And really think every thing from a weight perspective. Fglass bumper - why? If you don't want a functional bumper on the basis of weight, why put the weight of ANY bumper on? Etc.

 

[Alain - The Red Scorpion]

Nobody likes to ride in my X so I often think of removing the passenger seat.
Talking about...er...biological weight in an X, I can definitely tell in my Miata when I'm hauling an adult sized passenger...my shop pup not so much.

Same here. I am always alone in my X. So off went the passenger seat...and the glove box cover... and the spare wheel... and... and... I'm down to 870 kg, not counting both rear covers, replaced by a one-piece aluminium cover. Planning to fabricate the same for the super heavy front trunk cover. Objective: approx. 800 kg. Believe me, it makes a substantial difference in acceleration (plus of course braking and handling). "Light is Right" said Colin Chapman. You were Right, Mr. Chapman.