Piston Slap: The Making of the BMW M3 "Big Tank" Edition

Sajeev Mehta
by Sajeev Mehta

John writes:

I own an E92 M3 and it’s my huckleberry, except for one thing—with a gas tank capacity of about 16 gallons, road range is a measly 300 miles between fills. And when I drive, I want to drive.

Every other car I have owned has been able to do 400 miles on a single tank in highway driving with the exception of my STi, which only did 330 before rapid maneuvers caused temporary starvation.

So my question is this: is it possible to fit a larger gas tank to my car—say one of about 20 gallons or so? If so, what are the positives and negatives of this, and where would I get one?

Sajeev replies:

Back in the day, GM had you covered. Anyone remember the 36.5 gallon “ Big Tank” option Chevrolet offered for the Corvette in the early 60s? Back here in Bimmer world, you have two opportunities for installing a 20-gallon tank in your M3. Only one is guaranteed to work.

I have never seen the underside of an E92, but I do recall the M3’s rear mufflers being pretty gigantic. Which means you remove them, run tiny mufflers (like Dynomax bullets) and route both pipes on one side. (Get some ear plugs too.) Only then will a 20-gallon fuel cell fit. Maybe.

If that’s out of the question, how in love are you with your trunk? That’s the only sure location for an E92 with a big gas tank. If either way is feasible, getting the tank is easy: any race shop stocks these fuel cells. Dimensions are readily available too. There are plenty of E92s set up for race purposes, and you will emulate their wiring/fuel pump/safety setups for your car. Not exactly easy, but it’ll be easier than you think.

P.S.: Doing an LS-X powertrain swap with the F-body’s 6-speed transmission (with that insanely tall top gear) might get you to the magic 400 mile mark. Think about it: that powertrain means you can idle at 55-ish MPH. That, and the V8 M3 will be disgustingly fast and light. So, again, LS-X swaps are still made of WIN.

[Send your technical queries to mehta@ttac.com]

Sajeev Mehta
Sajeev Mehta

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  • PeteMoran PeteMoran on Aug 14, 2009

    @ doctorv8 Odd how the “high tech,” “high specific output” 4 liter V8 in the M3 gets trumped in fuel efficiency by a 12 year old pushrod Chevy motor with more cubes and more torque. Oh, and that same motor is lighter, cheaper, and more compact than Bavarias finest. Really? The BMW referenced weight with throttle bodies, all accessories and headers is 445lbs. Various versions of the LS2 seem to be 450lbs onwards and it's not clear if any accessories are counted.

  • Roadracer Roadracer on Aug 14, 2009
    niky :...this is a “compact” car, after all… not a midsizer. There's your answer--trade up to an M5. Surely it has a larger tank!
  • JOHN One is for sale on an ebay car donation site.https://www.ebay.com/itm/305579991767?itmmeta=01HYHVJ49MCC6HEWQY5AX9MX85&hash=item4725fca2d7:g:k9cAAOSw5V5mThFw
  • Scott So they are losing hundreds of millions of dollars and they are promising us a “Cheaper EV”? I wonder how that will look and feel? They killed the Fiesta because they claimed that they couldn’t make a profit on them and when I bought the first one in late 2010 they couldn’t deliver the accessories I wanted for it! Then I bought a 2016 Fiesta ST and again couldn’t get the accessories for it I wanted. They claimed that the components were going to be available, eventually. So they lost on that one as well! I don’t care about what they say anymore. I’ve moved on to another brand.
  • Michael S6 CX 70 or 90 will not be on my buying list. Drove a rental base CX 90 and it was noisy and the engine noise was not pleasant. Ride was rough for a family SUV. Mazda has to understand that what is good for Miata isn't what we expect in semi luxury SUV. My wife's 2012 Buick Enclave has much better Ride and noise level albeit at worse gas millage. Had difficulty pairing my phone with Apple CarPlay
  • Michael S6 What is the metric conversion between one million barrels and the number of votes he expects to buy.
  • NJRide This could give Infiniti dealers an extra product maybe make it a sub brand