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Old 03-01-2007, 02:13 AM   #1
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Make a guzzler a sipper

Hello it is about time I introduced myself. I'm David and I'm 21. I can spend hours reading about cars, whether it is about power or efficiency. I learned most what I know about cars, by hands-on experience.

My first car was a 85 Caprice (5.0 liter computer quadajet) It spun rod bearings, Then I bought a 93 Mitsubishi eclipse (1.8 liter 5 speed) for $500, fixed the brakes, added 17" wheels and It was the best handling car I ever had. I fell asleep at the wheel and totaled it, ironically, into another parked eclipse, probably at 35-45 mph. Then I got a 1988 3/4 ton Chevy truck. (350 Throttle body injection) someone made an illegal left turn (not my fault) and t-boned them. I took the insurance money and bought a 79 Chevy Blazer and a new 5.7 liter engine for the 85 Caprice. I pulled the TBI and wiring from it and put it on the new engine in the caprice.

I was on a DSM (Eclipse) Forum I don't remember which one, but 95% of the people there were antituner (or rice,) which was great. They didn't care about body kits or wings etc. Only function. Everything was about the Turbo 4G63 motor there. I haven't been there for awhile.
I later joined NAISSO Impala Forums. Those were mostly about the 94-96 impala, Also 91-96 caprice and Buick Roadmaster. There are not many boxy caprices like mine there. I have basically the same motor as 91-93 so I can squeeze in!
Also I am in GmTBI at yahoo groups. It specializes in Throttle body injection troubleshooting, performance, and conversions. It is an alternative to the other much more popular fuel injection. The most common TBI only flows 400 CFM stock. Many people rather convert to the more exotic FI or convert to carb.

One thing I think is great about TBI is that it injects fuel just before the throttle blades, instead of the intake valve, which gives the fuel more time to atomize. Something most of you don't have. I can burn my own custom chips like other FI.
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Old 03-01-2007, 07:26 AM   #2
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The only problem is fuel ditribution, and falling out of suspension. Back fires in CFI cares are a lot more fun to watch though haha.

Anyways, if your burning your own chips, I assume you have a wideband? You might want to look into the aerodynamics of your car. If you can fix some of the aerodynamics of the car that would help. Otherwise drive it more carefully (lots of great driving threads on here)

What kind of mileage are you currently getting? You can add a garage entry on here to host a few pictures and start a gas log. It would be cool so see what another land yacht owner is getting.
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Old 03-01-2007, 08:07 AM   #3
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caprice -

Hi, welcome to the boards. There is an interesting irony in the fact that us post-1996 drivetrain people can use the ScanGauge, so our lives are "easy" for MPG optimizing. The pre-1996 drivetrain people are forced to use more difficult but more powerful control systems. Since you had an Eclipse, I think you will like to read about this 1990 Plymouth Laser (similar drivetrain to your old Eclipse?) owned by member DRW that gets glorious MPG using Apex SAFC tuner control :

90 Laser
http://www.gassavers.org/garage/view/207

My hope is to someday (far in the future, probably) get an el-cheapo Saturn ECU/PCM controller off of ebay and do an autopsy to see if there is any hope of reprogramming it (damn chips are soldered in place !!!).

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Old 03-01-2007, 02:09 PM   #4
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I don't think atomization is an issue w/ most automobile injection systems. I mean, it's not like we're talking about 20psi of boost on engines with 15:1 CRs, just the usual 10-12:1 NA stuff. The switch to MFI was probably because it allows for better control of the mixture and injection timing which is needed for all the VVT-whatever systems. But for older cars, just shoot it in the intake and watch it go, so no problems there. I'd really suggest grabbing one of the T56s with the double OD (something like a .5 ratio for sixth) and maybe look into a gear vendors overdrive unit depending what your rear end ratio is... If you can idle down the freeway at 55-65mph, your cruising mileage will be in the 40-50mpg range. The down side is you'll have to shift more, but at ~2/3rds of throttle in top gear at 55mph you'll probably get double the mileage you get right now at 55mph. Good luck, there are plenty of people who would like to see a 40mpg/10s car here!
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I think if i could get that type of FE i would have no problem driving a dildo shaped car.
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Old 03-01-2007, 06:20 PM   #5
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Quote:
Originally Posted by caprice View Post
One thing I think is great about TBI is that it injects fuel just before the throttle blades, instead of the intake valve, which gives the fuel more time to atomize. Something most of you don't have. I can burn my own custom chips like other FI.
yea.... anyway whats the standard fuel pressure?

i would think your best areas for improvement would be a longer top gear and aerodynamics.

what kind of driving do you usually do?
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Old 03-01-2007, 07:37 PM   #6
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Aint much you can do with it. Driving yourself around in a 4000 lb v8 sedan with an automatic adds up to a lot of fuel being wasted... Sorry.

Make a guzzler a sipper, don't think so. Make a guzzler a marginally less guzzler, maybe.
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Old 03-01-2007, 07:52 PM   #7
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Buy a civic and save yourself the trouble of trying to be less wasteful in something designed to be completely unnecessary,

And welcome to the site!
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Old 03-01-2007, 10:12 PM   #8
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Seconded, I traded in the 20mpg, 3118lb century wagon a couple months ago on a very affordable metro and am currently in shooting distance of 60mpg (3.92L/100km). I could have put what I spent on the metro in the buick and not closed the mpg gap appreciably.

Also instead of a pickup, we have a trailer hitch on the saturn and a utility trailer. There's some folks getting real good mpg readings from their manual tranny saturns if you want one car that can "do it all".
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Old 03-01-2007, 11:11 PM   #9
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I'm gonna play devil's advocate and say it depends on what you're using the car for. If you use it for highway at a 4:1 ratio and really want a car with balls, go with the Caprice and get it geared as low as you can. The difference in peak efficiency between engines isn't much. Between a 92 Toyota V6 and a brand new Prius, there's only a 3% difference in efficiency, iirc. But the Prius gets more than twice the mileage because it's Atkinson engine and continuously variable tranny minimize pumping losses, unlike the older engine, which is operating at less than half of it's peak efficiency most of the time. If you drive mostly highway, and know you'll see clear roads at maybe 60-70mph, then you can pick a speed, calculate approximately how much power you need, and based on your engine's hp/tq curve, find the right combination of gearing that will place you at the BSFC (brake specific fuel consumption) minimum when you're cruising at that speed in top gear. For instance, lets say your sbc makes ~200hp@6000rpm, and you decide to leave your Caprice on the stock side. We can use a couple equations to guesstimate that at 70mph you only need ~33hp to maintain that speed, but since your car can make way more than that figure in top gear at that speed, you have pumping losses up the wazoo and inefficient engine operation. To make the engine more efficient, we need to drop engine rpm so the cylinders fill as much as possible with air and you don't get pumping losses. If you are at 2000rpm at 70mph, then we know you can make ~66hp, but only need ~33, so the cylinder is only filling about half of the way up. If you cut your engine speed in half again, then the cylinder can fill completely up and you can have the best possible engine efficiency at 70mph. These are just random figures, and the increase in your mileage depends on how much you can drop your engine speed at the desired cruising speed compared to how much power it makes, but depending on your setup and the options available to you, I think you could see ~40mpg@60mph.

Otoh, if you drive a lot of city, there's not much you could do for fuel efficiency with such a big engine. In that case, it'd be cheaper and easier to get a smaller car/engine.
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Old 03-02-2007, 01:34 AM   #10
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Now that I'd like to see- seriously!
Me too, but I'm pretty selfish. I want to see as many different drivetrains on GasSavers as possible, because that validates our mission. Something that caprice learns in his custom setup may help me later .

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