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Old 04-04-2021, 11:31 PM   #1 (permalink)
Master EcoModder
Join Date: Jan 2012
Location: United States
Posts: 1,756

spyder2 - '00 Toyota MR2 Spyder
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Extremely thirsty supermodel - eco attempt!

I decided life is short, and used car prices have shot up in the last I got this (probably the lowest mpg per occupant or per unit length/height on this forum lol):

Yes, 3600lbs, V8, 15mpg (drinks 91 octane). Right now I have a beater Infiniti G35 that gets around 24mpg on a good day, and it has an even less efficient engine (albeit quite a bit smaller) and similar weight and aero. If I can get a 26mpg tank, I will probably have set an Aston Martin owner record. Obviously, fuel cost is almost negligible compared to maintenance, but it would be nice if I could hit 500 miles a tank and reduce refueling.

I'm making this thread to document the eco-friendly mods that do happen to this car, which will be rather few in number. This car is mainly going to sit parked as automotive art and not burning through copious amounts of fuel.

All the planned mods that will maybe eventually happen are as follows:
-Partial grill block, pending fluid temperature measurements. The bar grill makes this extremely easy and aesthetically pleasing, just add tape to the back of the sets of bars. There's plenty of space behind the grille to do a bit of smooth ducting as well.

-Thinner fluids: The transmission fluid is already 70w-75 (OEM fill), but the engine has 10w-60 in it and the power steering has the original factory fill. The oil spec is A3/B4 which 0W-40 meets, but 5W-50 is factory approved and still an improvement. The PS fluid was updated in a service bulletin to CHF11S, the lowest viscosity fluid on the market, which I'll be doing. A P/S delete is not practical because of the way the belt is routed and also because the front of the car is extremely heavy, though some day I would love to figure out an underdrive pulley solution.

-Slightly taller tires when I need them in a few years, the 6th gear is fairly short.

-ECU Tune: At high rpm, the engine runs near 10:1 AFR On top of that, the EGR seems to be very underutilized at 4% maximum dilution, bumping this up and adding a few degrees timing should drop pumping losses by a lot, but figuring out how to flash this ECU may be a major challenge. If I can get the ECU reflashed to my preferences, I am optimistic that I can gain 5% more efficiency.

-Weight reduction:
  • Lithium titanate battery, which will drop 40+lbs out of the car and use less power from the alternator to charge. This may or may not work, as the battery is located behind the seats so there's some voltage drop in the cables going to the starter, which combined with the low working voltage of LTO and the large engine may be an issue. I may opt to buy a LFP battery if the voltage is inadequate.
  • When the time comes, lightweight flywheel, the AMR package should be around 10lbs lighter, and the rotational inertia is dramatically lower, which should be like removing >100lbs in 1st gear. Also, instead of the 25k mile original clutch life expectation, it'll instead outlast everything else on the car.
  • When the time comes, Wilwood two piece brakes (-16lbs), since it's barely more money than OEM replacements. I am thinking about getting them chromium or tungsten carbide sprayed so I don't need to replace them ever again to save money.
  • Airbox delete, -10lbs.
  • Trunk compartment divider delete, -10lbs (already done).

Ideally, the seats could be replaced with the Recaros they sell over in Europe (no side airbags), but my interior is in fantastic condition especially after I spent the whole day filling in all the wear spots in the leather and those seats would cost half a lifetime's worth of fuel XD

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Last edited by serialk11r; 04-04-2021 at 11:52 PM..
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