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It prevents the gas tank from pressurizing and rupturing. it also reuses the gas fumes, instead of them going out into the environment if you're silly enough to vent it to atmosphere.
Maybe a stupid idea but all these evap issues wouldnt exist if gas tanks were air-tight bags (inside a metal tank) that expand/shrink with the gasoline. Why is that not a thing? Maybe too hard to maintain
 

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Discussion Starter · #204 ·
If you block all of the vents to the fuel tank the engine will eventually stall due to pump cavitation. Also you may possibly collapse the fuel tank. Blocking it off will cause pressure to build in the tank and may rupture somewhere. You cannot seal the fuel system it needs air to flow in AND out. If you don't want your garage to smell like fuel that outlet had better go through a charcoal canister (evap)

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It is amazing what a few psi can do, negative pressure included. Which happens first, a collapsed tank to stalled engine? Maybe even a fried fuel pump?
 

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Discussion Starter · #206 · (Edited)
It is amazing what a few psi can do, negative pressure included. Which happens first, a collapsed tank to stalled engine? Maybe even a fried fuel pump?
I used to design instrumentation for tank farms. PRV's were part of my scope. There was so much to take into account. Especially if venting through a vapor recovery unit or a flare, using blanket gasses etc... In the case of the engine, gasoline has a range of RVP's. Somewhere around 9PSI. So depending on how fast you pump down there could be some negative pressure. On the positive side 9PSI over atmospheric is a lot of pressure over that area too. In essence if you completely plugged the tank you would expect it to develop around 9PSI give or take positive pressure over atmosphere. Over the surface area of the tank a few PSI could be a LOT of force. You would hope the pump would experience cavitation and destroy the impeller or stall the engine due to low fuel pressure before the tank collapsed. Or the gasoline may just boil to maintain the pressure if your rate is low enough. I'm not keen to try it and I don't suggest anyone mess with their evap unless installing a fuel cell with dedicated bladder and / or breather designed for the race track with an inversion (roll over) cutoff.
 

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Discussion Starter · #209 ·
Where did you get that cup holder? I might want it
I am Starbucks testing the cup holder over this week. It is a racing bike bottle holder. Seems to be doing the job! Available all over eBay and sold with the weight as the primary feature. The only drawback is that there is a little lip at the top that requires trimming to work with normal cups.
 

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Discussion Starter · #211 ·
More weight reduction starting. RPF1 with Azenis 660s. 15x7 & 15x8 for the lightest combo possible. I really don't care if I have to buy new rubber every other oil change. This combo is the lightest I could find. I honestly thought they shipped the tires by themselves the combo is sl light!

The wheels come back off when I do my alignment this week. I'll be pulling out the rotor dust / splash shields for some weight reduction while I'm in there. My Elise didn't have them so I am accustomed to the 1/2 second of weak break force when wet.

I'll likely need a few degrees of camber in the rear.

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Where do you get your alignment done? I need a alignment shop i can trust to get my exact numbers. Do you have adjustable arms in the back? What numbers are you going for?
 

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More weight reduction starting. RPF1
Chapeau.
One of the first Í did; shed the weight where it counts most ;)
The wheels are both unsprung ánd rotational mass. The latter makes it count double. I could copy a brain hurting formula but the easiest visualisation is that the wheels turn at twice the speed the car travels at.

Thanks for keeping up the sharing @Node , despite the head wind and derailings(y)
Ah and I díd delete the charcoal canister. Fitted a racing motorbike tank cap breather valve.

Sorry if I missed it but where did you get the mirrors from? Still on my whish list those. The interior one I simple deleted.

My rear wing is under 3 kilos now and gives some 20 kgs of downforce at 80 km/h. At 100 km/h this results in about 5% more traction at the rear without extra centrifugal force meaning ditto extra grip margin. You could use that for cornering speed or keep it as extra safety margin.
Also worthy to note that it more than compensates for the decreased MR2 (read twitchyness) of adding lightness. The wing is like the fletches on an arrow.

p,s, cup holder; I simply ask the charming company :cool:
 

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Discussion Starter · #214 ·
Alignments I usually do myself with a string and camber gauge. I have to check the garage floor first this weekend. I suspect it has moved in 50 years. May not be entirely level.

Regarding the suspension parts, I'm having a tough time choosing what I am going to use. The effective damping of the KYB black struts has gone WAY up with the removal of all the weight from the chassis. It really is becoming a rough ride. You would almost think the car has coilovers aside from the squats it does during acceleration. It's going to be an interesting challenge to figure out what spring rate and damper settings to go with.

Further weight reduction... The seat replacement should net me another 50 lbs and I'm not done yet. I'm strongly considering hard coated and ceramic treated thermoform plexiglass for all the windows now that that is an option. I really would like to see one of the thermoform windscreens in person first though. Maybe I'll ask at the Lotus dealer when I pick up my diffuser. One of the only areas I'm willing to add weight is aerodynamics. I feel the aluminum diffuser is the safest with all the exhaust heat even if a difflow carbon unit is lighter.

Anyway, lots of changes coming.

Mirrors are APR Performance Formula GT3 Carbon Fiber. Very nicely designed base. The stalk could be lighter but they are super light anyway.
 

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Thanks for the mirror specs. Node. Alas too rich for me with shipping and import.
Same issue as with lighter bonnet/engine lid and plastic windscreen, otherwise I´d have had those 10+ kg of lightness added years ago :cautious:

50 lbs on the seats is WOW! Neat!
 

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Discussion Starter · #216 ·
Thanks for the mirror specs. Node. Alas too rich for me with shipping and import.
Same issue as with lighter bonnet/engine lid and plastic windscreen, otherwise I´d have had those 10+ kg of lightness added years ago :cautious:

50 lbs on the seats is WOW! Neat!
Yeah, stocker seats with leather are somewhere around 38 lbs each. I just sent off an inquiry to Eltech. My Italian is crap but a single skin seat from them is shocking light. However I can't tell if the weight they advertise is with or without pads. So I can't say 100% what the delta will be. I was really interested in the Tillet B5 but they are 10 lbs vs 5 lbs for the Eltech and lack FIA and homologation ratings. Plus they cost like 50% more. Too bad because I prefer their more subtle style and the Tillet appears to seat the driver about 1” (or more) lower. I have also heard that they are super comfortable for those who are of narrow girth.
 

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Do factor in the weight of the mountings.
There is a hefty difference between fixed, sliding or even the tilting OE sliders. I opted for twó of the latter so the passenger (a RHD drivers base) had a tilting adjustment too. I left quite a bit of weight on the bone with this but it is véry much worth the added practicality.
Bottom line I halved the seat weight without losing practicality, in fact gaining interior space.

There is só much choice.
When I was shopping, also looked at aluminium, ´fighter style´ buckets. Also akin the ones like mounted in the Porsche 550 racers. In retrospect they would have matched better with my tonneau but the current ones are more comfortable.
Then there are the plastic kit car seats. Ah and don´t forget the early Elise ones. Those are quite good but do without exception need a refurb of the covers.
The by far best ones, even factoring the extra cost, are imo the carbon fibre ones used by Noble cars. Just did not want to spend that much on a passenger one too so opted for two also very nice ones. Still content.
 

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Discussion Starter · #218 ·
As I recall the Elise seats are not that light. The S2 first generation ones prior to the Probax ones hurt my back a lot. Maybe it was the way I always plopped into the Lotus. My max with those seats was about 3 hours before I would need to get up and walk around. I had to modify the brackets on mine too to get the seating angle right.

Yes I know the brackets are going to add a bit of weight. I had my seats completely apart when I recovered them and even without the base they are still fairly heavy. I'm on the fence about the mounting. I will either make some tracks or brackets with a pivot cotter pin to allow access to the area behind the seats.
 

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I left some 5 kilos or so on the floor with the choice of rails. ´On the floor´ being a key thing. It is in the centre and on the floor so even though 5 kg is 5 kg, the location made me give more weight to functionality.

Whishing you lightness, whatever the choice will be.
 

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Discussion Starter · #220 ·
I left some 5 kilos or so on the floor with the choice of rails. ´On the floor´ being a key thing. It is in the centre and on the floor so even though 5 kg is 5 kg, the location made me give more weight to functionality.

Whishing you lightness, whatever the choice will be.
I have been looking for aluminum tracks somewhere. It seems nobody makes a good set. I have seen a few lightweight tracks but they are really designed for bottom mount seats. The lightest and lowest seats all seem to be side mount. At this point my plan is to cut up a set of OE tracks and use some steel tabs to attach to the side mount points. Im not really happy with that solution since it would be heavier than direct mount brackets and will also require re-tapping the mount points in the floor.
 
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