Massive air dam on '98 Geo Metro (Firefly), A-B-A coastdown test; Update: version 2

[tomicdesu]

Originally Posted by MetroMPG

I'd argue that tank to tank testing is madness! Way too many variables.

? I'm not saying tank to tank; I'm saying over a few to many tankfuls, say 400+ miles. I don't know what variables you'd be worried about, and of couse it would matter what you are testing and how large a delta change.

For something as substantial as the huge cardboard airdam results would be concrete; A B A tests work well here. If you are trying to measure something down in the noise, well, I'd argue you would have a hard time telling on the street anyways, and long-term averages are the only thing trustworthy without sufficient environment control.

Testing is tough to pull off. Cars have a crapload of variables. Maybe I'm spoiled with southern California sea level flat highways and narrow temperature and humidity range.

I wouldn't attempt to measure (random example) with/without side mirrors Cd; it's too small. Big airdam and tail? I better see a measurable result. Talking street car; if I was racing with a super slick car and a budget, more is possible obviously.

I see a lot of threads on this board making claims that I don't see evidence for. When you're measuring incremental changes that amount to a few bare percent, yeah, it's truly tough. But we need some sort of reliable -- if insufficient resolution -- tests to back up claims.

[tomicdesu]

Originally Posted by MetroMPG

I'd argue that tank to tank testing is madness! Way too many variables.

And I argue back, errors and inaccuracies in measuring fuel consumption, and very-short-term variables (wind, surface, driver) are substantial.

? I'm not saying tank to tank; I'm saying over a few to many tankfuls, say 400+ miles. I don't know what variables you'd be worried about, and of couse it would matter what you are testing and how large a delta change.

For something as substantial as the huge cardboard airdam results would be concrete; A B A tests work well here. If you are trying to measure something down in the noise, well, I'd argue you would have a hard time telling on the street anyways, and long-term averages are the only thing trustworthy without sufficient environment control.

Testing is tough to pull off. Cars have a crapload of variables. Maybe I'm spoiled with southern California sea level flat highways and narrow temperature and humidity range.

I wouldn't attempt to measure (random example) with/without side mirrors Cd; it's too small. Big airdam and tail? I better see a measurable result. Talking street car; if I was racing with a super slick car and a budget, more is possible obviously.

I see a lot of threads on this board making claims that I don't see evidence for. When you're measuring incremental changes that amount to a few bare percent, yeah, it's truly tough. But we need some sort of reliable -- if insufficient resolution -- tests to back up claims.

[gascort]

I see good points here from Tom... and Metro. For the small stuff, you can do a corollary study to show a general (albeit small) trend that would not show up in the noise of an A-B-A test. One could argue that such small changes are not worth doing if not noticeable, but I noticed a general trend after removing my mirrors, roof rack, and modding my wipers. I couldn't get a coastdown or immediate, consistent A-B-A measurement of the gains, but they can't possibly hurt, and I generally improved by about 1mpg over several tanks after the three small mods.
I have absolutely no doubt that the front wheel skirts will help. If A-B-A was inconclusive with just one, there may be enough improvement with both to see a small trend emerge from the noise of testing results. (plus, it looked sweet!!) Also, it might be worth waiting until after making the new air dam - with more air pushed to the sides and over the top of the car, the front skirts become more important and thus more noticeable to get full gains of the air dam.
That said, this has been a bit threadjacked - when are we going to see a "professional, true-factory looking" airdam appearing on Darin's firefly?

[tomicdesu]

I neglected to point out I do the multi-tankful thing on a car with a carburetor (!), so the EFI on-time calc clearly won't work there. And I'm with you on the 'in the noise' cummulative stuff like your (gascort) mirrors and stuff. It's a tough call. But even coast-down would need multiple runs to average out wind and other factors.

I'm looking through various airdam threads for technique and testing methodology. My ancient car has I think a lot of low-hanging fruit.

I didn't see concrete results for Darin's lovely cardboard hack -- just a casual result from the meet. Did I miss something?

MetroMPG -- can you point me to a thread or info on practical fuel-comsumption measurement methodology? Also I apologize for coming on too strong, and I hope I didn't sound dismissive.

[gascort]

Originally Posted by tomicdesu

MetroMPG -- can you point me to a thread or info on practical fuel-comsumption measurement methodology? Also I apologize for coming on too strong, and I hope I didn't sound dismissive.

You should check out his website - metrompg.com

[JoeBob]

I know this is ancient history now, but so is the story of a friend of mine's Pinto station wagon.

1974 Pinto wagon, 2.3 liter engine, automatic transmission.
With timing set per factory spec, about 9 mpg. With timing set just short of pinging, about 18 mpg. The car was < 4 years old at that time, probably under 50k miles. He kept a gas log on the car at that time. I was the person who adjusted the timing on the engine, so I know how it was set. I remember the situation well because it seemed like awfully low mileage.

Two caveats: One - he WAS a rather, uh, shall we say, "enthusiastic" driver. As enthusiastic as one can be in a 2.3 liter Pinto with an automatic. He was always on "assigned risk" insurance, paying through the nose because of speeding tickets, etc. Two - He did replace the timing belt at some time previous to our setting the timing...I can no longer say for certain that he had the valve timing set right. I think he did, but it's been over 30 years ago and I've forgotten many things that were more important to me than that...

Originally Posted by Frank Lee

Who knows?

I've been trying to track down something trustworthy re: Pinto fe but as of now what I put up is what I got.

I haven't even found the original C&D article. I want to see that, not filtered by all the recent coverage of it. I did see someone's comment that the car in question had the 2.0 with a/t.

Almost regardless of what I or anyone finds, I simply don't remember little '70's cars, rotten old-school automatic transmissions or not, getting fe THAT terrible.

[Frank Lee]

Thanks...

but his sounds like it could be "atypical".

Your friend could probably make a CRX get 10 mpg too.

[Christ]

Originally Posted by Frank Lee

Thanks...

but his sounds like it could be "atypical".

Your friend could probably make a CRX get 10 mpg too.

Hell, I didn't even get that bad of mileage in my Si going 100+ at nearly redline... IIRC, cruising at 65-70 on the highway was like 4k RPM.(Si/ZC hybrid tranny - shortest gears you can get, and stupid short for anything really usable. You spend too much time shifting, IMO.)

[Frank Lee]

OK it ain't much but I found this:

Smilin' Jack on February 14, 2009 at 08:05 PM

My first new car was a Grabber Green '71 Pinto hatchback. Bought it for $2375 cash when I was in the service. It had some quirks, but I liked it. Gave the Colonel a ride in it one day and he said, "What you have here is a tin can filled with plastic." Didn't bother me a bit as I thought, "Heck, it doesn't pretend to be anything else. That makes it more honest than 99% of everything else on the road."

There was a heat shield over the exhaust manifold that would sort of bark at you at certain RPMs during acceleration. Took awhile to find that and come up with a fix. Also, the points had to be regapped at least once a month. Distributor cam must've been rough. The points would slowly close up, timing would become greatly retarded, and performance would go to h*ll.

Also, one of the overhead cam lobes started to self destruct at about 45K miles. Probably due to running the valve lash too loose on the 2.3 engine. Figured out where the racket was coming from, replaced the rocker arm, dressed out the lobe with extra fine emery cloth and ran it with no further problems until I scrapped it due to rust in the early '80s.

The car got 28 to 29mpg regularly with its little 2 barrel (Weber?) carburetor. I thought this was great after coming from a gas guzzling '66 GTO.

It wasn't a bad car at all. I really liked the crisp little 4-speed transmission and the rack & pinion steering. The Vegas were better looking, but their engines were serious crap. After the Pinto, I bought nothing but Fords until 2003.

Thanks for this article. It brought back memories.

It's the m/t but still, the a/t shouldn't (couldn't!) be 50% worse! I know of no car where the a/t version is that much worse.

[Christ]

That's bout what I 'member from Father's Micro-Stang (Pinto)...