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Old 04-04-2021, 11:31 PM   #1 (permalink)
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Extremely thirsty supermodel - eco attempt!

I decided life is short, and used car prices have shot up in the last year...so 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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Old 04-05-2021, 07:52 PM   #2 (permalink)
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Considering how a Recaro could improve the support while pushing this beauty to its limits on a track day, it may be worth
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Old 04-06-2021, 12:04 AM   #3 (permalink)
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The Recaros would drop 60lbs which is really substantial, the issue is the shape doesn't really seem to fit the rest of the interior style, and losing the side airbags isn't great. I could go buy Recaro shells and then have an upholstery shop make leather covers for probably 3-4k all in vs. 11k for the OEM pieces (yea...). My acrylic paint touchup made the leather look almost just like new, and the foam in the seats is still mostly intact, so I'll probably never be able to justify replacing seats.

I drove it to get gas at Costco and then took a short fun spin around town...based on the needle movement, I'm pretty sure I went through over 1 gallon of gas in around 16 miles (still haven't figured out how to set the trip meter lol).

I was driving pretty efficiently and slowly but the oil temp hit 100C very quickly (measured with an IR thermometer pointed into the oil tank, as the car doesn't have a sensor :/), so that 10W-60 is creating some SERIOUS friction.

The power steering was actually only barely warm. The original factory fill was a Texaco Cold Climate low viscosity fluid that's already thinner than most PS and ATFs on the market, but I'm putting in the updated even thinner fluid.

Avoiding idling should help a decent amount, though replacing the starter motor is extremely time consuming so cycling too much is probably not smart. This engine burns about 1.7 liters per hour (that's 0.44 gph) idling, which is fairly bad but relatively low for a V8 lol. I think for the custom tune I'm trying to figure out, dropping the idle from 750rpm to 680rpm like a more normal car would quench its thirst a touch.

Last edited by serialk11r; 04-06-2021 at 12:31 AM..
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Old 04-06-2021, 02:16 AM   #4 (permalink)
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Old 04-07-2021, 01:02 AM   #5 (permalink)
It's all about Diesel
 
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Quote:
Originally Posted by serialk11r View Post
My acrylic paint touchup made the leather look almost just like new, and the foam in the seats is still mostly intact, so I'll probably never be able to justify replacing seats.
I guess the pleasure of seeing the results of your own work on the restoration of the upholstery may decrease any will to replace those seats
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Old 04-07-2021, 02:57 AM   #6 (permalink)
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Okay not much mpg progress, been working hard at touching up the bigger paint chips on the front.

Did a little more research, apparently the PS was filled with normal ATF from the factory, so switching should actually drop the viscosity by almost 50%! AFAIK, this could actually be a measurable improvement if it can drop the PS pump power from e.g. 500W to 300W.

Still debating whether I want to go thinner than 5W-50 on the motor oil...With very few miles of gentle street driving, I feel like a 0W-40 would not shear below the minimum viscosity, and the factory used 0W-40 for break in. The viscosity drop would reduce friction probably 10%. However, NAPA has 5W-50 for dirt cheap so I might just go all 5W-50.

I've been contemplating the grill block more. It seems like the radiator fan is very eager to turn on (the engine is large after all), so it's probably best to be conservative and have something easily removable that only blocks a small portion, like a piece of tape (easiest), or a bit of foam behind the grill (more streamlined, slightly more work to attach).
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Old 04-08-2021, 11:33 PM   #7 (permalink)
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Only blocked off a small portion of the grill, but half the oil cooler in the hopes that my oil gets hotter and thinner. Looking at some charts, it seems like 10W-60 at 120C is more like a 40 weight at 100C, with 60% of the viscosity.

Also I hooked up my OBDII scanner again and was pleased to see that with a hot engine the idle fuel flow is actually 1.6lph not 1.7lph. Still very high...
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Old 04-09-2021, 03:08 AM   #8 (permalink)
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Old 04-09-2021, 09:26 AM   #9 (permalink)
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10w60!
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Old 04-09-2021, 11:56 AM   #10 (permalink)
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They have 0w-50 now, but maybe that's too expensive for your eco-project.

And you can swap that Infinity for a proper slow car like an old Prius now, just add a bumper sticker that says: "My other car is an Aston Martin"

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