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| Mechanical Mechanical – General Tips, Problems, and Solutions, not related to the specific systems above |
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#1 (permalink) |
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Site Admin
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30MPG is the Goal
I use my '72 1900 wagon as a daily driver for 8-9 months a year and average between 20 and 24 MPG for a 40 mile round trip commute. It's an automatic with non-working A/C. 32/36 Weber. Low comp. engine was "rebuilt" not to many miles ago.
I pulled the head off to fix an oil leak (late style head gasket used on an earlier setup) and got to thinking about ways to increase it's gas mileage. I'm looking for ideas or comments on how to get it to a 30 to 35 MPG level using a combination of conventional parts and tricks.Here's what my thoughts and questions are so far: Cyl. Head - I'm replacing the head with a 1.5 head. Should I use a stock solid or hydraulic cam? Don't want to get into any wild porting, but are there any areas on the intake side that should be cleaned up? Fuel system - Carb (Solex or 32/36 Weber) or '75 Fuel injection? Exhaust - Sprint with a 2" pipe? Cooling - Electric fan or '75 clutch fan? Tires - I have a set of 185 (?) x 14 that I can put on. Excess Weight - The only A/C parts left on it is the under dash unit. Rear seat is out I do not plan on dieting and losing 50 pounds so that is not an option. Throwing some ideas out to see where this goes. Last edited by Gary; 06-13-2008 at 08:09 PM.. Reason: 6/13 - Changed title to a more realistic goal. |
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"My name is Gary and I approved this post."
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#2 (permalink) |
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Have Opel, Will Travel
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Tall, skinny, properly-inflated to slightly over-inflated tires are the first place to start. Second place is new top quality synthetic lube in the trans and rear axle. Third is top quality synthetic grease for the front wheels and u-joints.
It might be worth slipping a quart of type-F ATF in with the new tranny fluid to firm up the shifts some. That's an old trick for firming up GM transmission shifts, though without knowing the condition of your trans it's hard to know if it would work well, not work, or damage something. I would suspect that for the best possible fuel economy you would want to use the EFI manifold and injectors and such but swap to an aftermarket computer like an SDS unit or a Megasquirt that runs off either a newer hot wire MAF sensor or a MAP sensor. A more sophisticated injection system should allow for better fuel economy if it's dialed-in correctly, or at least more tuning options to get towards more mpg. |
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1958 Rekord Sedan, 1958 Olympia Wagon, 1959 Opel Olympia Sedan, 1967 Kadett Coupe, 1967 Admiral Sedan 4L CIH-6, 1968 Kadett fastback 1.1L, 1970 Kadett Wagon Turbo 2.2L, 1971 Kadett Sedan 1.1L, 1971 Kadett 4-door, 1972 Ascona Sedan 2.8L V-6, 1973 Blue Max Manta, 1975 Manta Wagon 4.3L V-6
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#3 (permalink) |
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Rice Cooker
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Gary,
I've had a similar goal in mind for a long time (with a manta) but haven't made much progress other than accumulating parts (I keep getting sidetracked with other projects). I can't help but believe that going to a modern, fully tunable EFI system would make a big contribution. I'm planning the Sentra SER throttle body/Opel EFI plenum setup with a megasquirt, and try to tune the engine for economy. Several years ago when I dumped a 4 speed and installed a 5 speed in a GT I was getting 30+ MPG using a well-tuned Weber 32/36. I could never break 25 mpg with the 4 speed, but my commute was all highway. My experience with the automatic has been even worse gas mileage. I'm wondering if there are strategies to porting an Opel head that would improve economy? Certainly skinny tires help, along with a good ignition system and appropriate exhaust. It'll be interesting to see how others may have approached this challenge. I'd like to see just how high the mileage could go with the 1.9L. Todd K. Edit - Also, what about cam profile? That's a pretty cheap way to drastically alter an engine's performance, but I've never heard us mention optimal profiles for economy. Last edited by neuropel; 01-28-2008 at 12:35 AM.. |
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"I'd rather have a bottle in front of me than a frontal lobotomy"...
________________ 1969 Lenk GT 1974 Manta 1973 Manta Rallye |
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#4 (permalink) |
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Member
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I recommend breaking your approach into two areas. Let's say something like:
Big expensive gains would include converting the car to a five-speed manual transmission. Rebuilding or overhauling the engine to keep the combustion chamber tight. Then move on to advanced modifications such as EFI and engine management systems. Small incremental gains would include good wires/plugs, electronic ignition, synthetic oil, your tall skinny tires. And wax the hell out of the car to make it as slippery as possible. Meanwhile:
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#6 (permalink) |
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Non Civilian
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I also had high lift low duration cam that seemed to help gas mileage. 252 adv. dur. with .420 lift.
If I recall I was getting 34 mpg with .30 over high comp pistons and a pacesetter header. |
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Some People Are Like Slinkies. They're Not Really Good For Anything, But They Bring a Smile To Your Face When Pushed Down The Stairs."
![]() Remember: Advice and Opinions are free, take it for what it's worth. Caution: Driver carries less then $20 of remorse. |
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#7 (permalink) |
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Member
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check the fuel/air ratio with
Gastester Digital Exhaust Gas Analyzer | Automotive Diagnostics | Northern Tool + Equipment or similar and change jets if needed. Make sure your choke is fully open when hot and working properly. |
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#9 (permalink) |
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Detritus Maximus
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Depending on what comp. ratio you get with the 1.5 head, a 5 speed may not work well. You drop your rpm, but will it have enough power to pull an overdrive? Flat tops, at least, or maybe do the 2.4 stroker bottom with the stock head and a good cam.
I'd say look for torque rather than hp. Anything that keeps the rpm down will help alot. The further you have to push the pedal down to achieve the performance you want, equals more rpm and gas. Keep the windows up, aerodynamic mirrors, 3.18 rear end, lose the roof rack, front airdam, and maybe lower it a little. Whatever you do, keep from having rev the motor to much. Maybe someone else can answer this, is there an advantage to using an earlier small runner intake manifold for economy purposes? |
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"No, it's not fiberglass."
"No, the motor is not in the back." "No, your friend in high school did not 'peg' his speedometer." |
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#11 (permalink) |
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Southern Red Neck
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Actually, I have a stock 75 F.I. Sportwagon, with roof rack, airdam and huge fog and driving lights. It was an automatic, till I switched it over to a 5-spd and it got 33 mpg at an average of 70mph when I went to and from Carlisle last year. Oh, it has pertronix ignition
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"Yes, I do have a rifle rack in my Sportwagon"
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#12 (permalink) |
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"The Jägermeister"
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I assume Gary has this wisdom anyway, but maybe for some younger kids around here: The most efficient way is a defensive driving style. Don't spin the tires when leaving the red lights, don't race the rice cooker next to you. Speed up slowly, get off the gas when going downhill. Look forward and get off the gas approaching a red light or stop sign. Sounds boring? In morning and evening commuting I DON'T CARE!
Dieter |
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#13 (permalink) |
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Member 1000 Post Club
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Gary,
From recent experience, I found the larger intake valves coupled with modest porting gave better economy and power. Bumping up the compression will also make a difference. However, I don't know for sure which method of increasing the compression ratio yields better economy results: low comp pistions with a 1.5 Head or flat top pistons with a 1.9 head. My guess is: it will take more and higher skilled porting work with the 1.5 head than with the 1.9 head to achieve the economy results you desire........... Also, I recommend changing over to synthetic fluids and greases as Jeff suggested. A front air dam will help aerodynamics.... as well as reducing height of the car.... if the rear of the wagon is lower than the front, from saging springs, the front will catch too much air under the bumper... Also, you need to restrict some of the air through the radiator/engine compartment as well as this make up about 20% of total drag. |
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Paul
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#14 (permalink) | ||||||
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Project 1450 supporter...
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Hydraulic cam is a better choice IMO, the specs are milder.
Assuming you go the Weber route, keep it a 32/36 and jet accordingly for economy, probably 125 primary main jets FWIW.
I'd lose the automatic and go 5-speed, the automatics have about 300 rpm worth of 'slippage', and the engine is always revving higher than even a 4-speed. They also eat up a lot of power and create heat, hence drag. I've never gotten 'good' mileage from an automatic Opel, and I've driven 3 of them as daily drivers over the years. When I drove my Ascona from CT to Mid-Ohio racetrack back in 1995, I got 28.5 mpg for the entire trip. And we all know the Ascona is a brick aerodynamically. That was with a Getrag 240, 3.89 gears, very wide tires (245/50 -13's!), and 300 lbs of stuff in the trunk (spares and luggage), and a constant 72 mph for 11 hours each way. Oh, and the engine was the same one I loaned you for your old blue wagon, with a 38 DGAS and ported intake, so it was making 97 hp instead of 65 hp stock. Considering the extra weight, aerodynamic and frictional drag (tires), and the addition of 50% more power, it wasn't too shabby. And that car was only rated for 24 mpg from the factory... Bob |
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#15 (permalink) | |||
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Project 1450 supporter...
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The bigger intake valves help because the Opel head design over-scavenges on the exhaust side, and thus uses more fuel (dumping it out the tailpipe).
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#16 (permalink) | |
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Living in the past
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30 MPG or bust
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#17 (permalink) | ||||
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Site Admin
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Round 2
Thanks for the inputs. My commute is ~32 miles highway and 8 miles city. Only one route is available.
![]() How would you restrict the air flow?
Thanks, guys. I will be keeping the automatic and will not be going into the lower end of the engine at this time. So the dished pistons are staying. (I am gathering up parts now and will be building up a stroker motor for my GT at some point) Here is my plan based on the posts so far;
New question: Valve timing - Stick with stock setting or advance/retard the setting? I'm sure more questions will come up but it is good to get it all in one thread. |
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"My name is Gary and I approved this post."
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#18 (permalink) |
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Opeler
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I don't know what the situation in the Northeast is, but you may find that where you buy fuel can make a difference. I avoid filling up in the Chicago metropolitan area if possible. They use blends that are more eco-friendly but definitely affect mileage. If I fill up in rural areas I find my mileage can be around 5% better. One clue that you're getting the "good stuff" is that the pump nozzle lacks vapor recovery hardware.
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