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MetroMPG 05-11-2017 02:45 PM

MetroMPG's 1998 Chevrolet Metro (Pontiac Firefly) mods & repairs kitchen sink thread
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(The unmolested 1998 Pontiac Firefly 1.0L 5-speed, shortly after bringing it home.)

I figure it's about time I made a "kitchen sink"/catch-all thread to document everything - eco and otherwise - that I've done/am doing to the Flea.

(I've had the car for 12 years now -- I think it's safe to say it's a keeper!)

If you don't know the backstory, the car was a lucky barn find: it had been driven less than a year, and then parked in a garage and not driven for 7 more years before I got it with ~2500 km / ~1500 miles on the clock.

MetroMPG 05-11-2017 02:47 PM

Mods & Tests index...
(This list is a work in progress - will be adding links to related threads.)

Transmission & engine

  • Installed transmission with taller final drive - 5.2% improvement
  • synthetic transaxle oil - untested
  • efficiency camshaft from XFi model installed March 2007 - untested
  • lower viscosity synthetic engine oil (at first: 5w30 2L + 0w20 1L), changed to full 0w20, summer 2006 - untested
  • timing advanced - untested
  • engine block / coolant heaters (on the Blackfly) - Update: April/07 installed additional 850w inline heater
  • alternator disable - ~10% improvement
  • warm air intake (WAI) - tested
  • K&N air filter (Busted! Removed & sold. See Testing a 'performance' air filter for MPG)


  • prototype removable boat tail - ~15.1% fuel economy improvement
  • partial grille block & rear wheel skirts - ~5.7% improvement
  • streamlined wheel covers - untested
  • deleted passenger outside mirror - ~2.3% improvement
  • Kammback hatchback extension - ~4.9% improvement
  • radio antenna repositioned - untested
  • gap filling around headlights - untested
  • hood/bumper gap sealed - untested
  • partial cowl block - untested
  • smooth undertray - ~2% improvement
  • gap filling around headlights - untested
  • massive cardboard air dam - tested

  • tire pressure 38 psi (front) 36 (rear); boosted to 48/46 Feb/06; again to 52/48 fall/06 - tested
  • LRR tires (Bridgestone Potenza RE92 from 1st gen Insight)
  • lightweight 14 inch alloy wheels (with wheel discs)
  • aftermarket cruise control (only used for testing, or on flat roads)
  • new brake calipers (on Firefly #1 - the original ones were dragging slightly & replacement noticeably improved rolling resistance)
  • daytime running lights switch - so I can turn them off on a divided freeway, where DRL's safety contribution is lowest. (It's highest on undivided highways where there's an oncoming overtaking hazard, and where other cars are approaching your path at right angles - e.g. urban driving).
  • engine kill switch (to keep the ScanGauge alive if the engine is stopped while at rest or coasting)

  • a good tire pressure gauge
  • a ScanGauge
  • Accessing the brain trust at
  • Books: Road Vehicle Aerodynamic Design by RH Barnard; Aerodynamics of Road Vehicles edited by Wolf-Heinrich Hucho

MetroMPG 05-11-2017 02:57 PM

exhaust work - getting harder to find parts!
The just car's coming up to 40k km / 25k mi., and it's time for its first ever "major" repair: exhaust work. Original exhaust, and I've been patching various leaks with muffler cement (bondo, actually :D) for a couple of years now.

Well, the intermediate pipe busted last week, and no reasonable amount of bondo can hold it together any more. It's time to actually spend some money on this heap! The original pipes only lasted 19 years - shameful.

Interestingly, the car is now getting old enough that the first 2 parts stores I called couldn't get the parts. The dealer doesn't stock it anymore either -- their parts guy said GM sold off all its OEM stainless Metro exhaust parts to a U.S. company. They could special order it, but the price was crazy.

Luckily, the 4th place I called could get it. So I'm getting an "aluminized steel" replacement for the intermediate pipe w/ resonator.

MetroMPG 05-11-2017 03:39 PM

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Not as good as stainless, but I wonder how the cost:durability ratio compares between the two metals. This was 1/3 the price the dealer quoted for the stainless part. Think this'll last 1/3 of ~17 years?

I'm about to find out, and then I'll know for the next time it needs replacing.

Daox 05-11-2017 04:34 PM

Since you haven't been driving the Firefly in the winter, I think you'll get some pretty good life out of it.

MetroMPG 05-12-2017 11:46 AM

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True. Also, I rarely do short trips where you fill the system with condensation, then turn the engine off & cause it to rust out from the inside. Longer trips heat everything up & dry it out, which helps keep things shiny.


I discovered last evening it definitely needs a new muffler too. I couldn't see how bad the top of it was - it's coming apart!

I'm surprised it was still muffling. Also cool: note the Suzuki name stamped on it!

Here's the whole mess:

Yes, that's duct tape! (You know you're a shoddy mechanic when there's duct tape on your exhaust system.)

And it looks like I repaired this before and completely forgot about it -- the section of pipe between the flange and the resonator was replaced. It has the telltale signs of my awesome welding skills on it. Pretty easy to tell from factory welds.

I really should make a repair log for the car. Hey, I think I just started one with this thread.

Daox 05-12-2017 12:11 PM

Hah, yeah that muffler looks pretty far gone. Aluminized replacement I take it?

MetroMPG 05-13-2017 08:48 PM

Re-muffled, for life!
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I splurged and went for the stainless muffler with a lifetime warranty.

Very happy with the results: The exhaust is tucked up snug & tight to the underbody, it doesn't rattle against anything, and the car purrs like a Rolls again.

I joked (half joked?) with the parts guy that there is probably a 0% chance that the company will still stock this particular muffler by the time I need to claim a warranty replacement. In another 10 or 15 years maybe?

We'll see. I'll post back when that happens. :)

MetroMPG 05-15-2017 06:33 PM

Getting hitched...
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Next up... it's not as bad as it looks!

I just took the bumper off to measure for a trailer hitch.

For occasional towing of my light utility trailer... and as a mounting point for something that rhymes with "bloat trail".

Stubby79 05-16-2017 01:26 AM

Moat rail? Float sail? Goat jail?

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