'75 Injected Stock Ascona: Gas Mileage?

[Opelkurt]

Question:

I have an injected '75 Ascona sedan, bone stock (low compression engine) with 70,000 miles. Automatic tranny, no other options like AC, etc. It drives and runs like new. 165/80 tires at max pressure.

I do mostly highway cruising with this car, 55-65 mph. It routinely gets about 21 mpg, no better or worse, tank after tank. Does this seem about right for this breed of Opel? Anyone else keeping track?

-Kurt

[opelnut10]

That is a good number, it is a three speed automatic heaviest model Opel that was imported. In top tune and driving it like you have a raw egg under your foot it might do 23 MPG. They are somewhat under-powered and with the 3:44 rear you are at about 2500 2600 RPM at that speed. If you do mostly highway driving you might do a little better with a 3:18 rear but 80hp pushing a 2300 lb. car is only going to do so much.

[Paul]

Kurt,

I can't speak for the Ascona w/ auto, but a 1975 Manta w/4-speed was rated by the EPA @ 19 mpg in the city and 27 mpg on the highway. BAck when the Federal Speed limit was 55mph, I used to get 28 - 30 driving at 63 mph on the interstate.

Somewhere I've got an old Car and Driver with a 6 car comparision that might give the EPA numbers from back then, but the car was a manual tranny.

I think 21 mpg is a little low. The 75 FI model used a "Special" thermostat. If you are using the standard looking thermostat, then the water never heats up to the proper temp and the car will run a bit on the rich side. The injector pulse width is tied to the water temp by a negative coefficient temperature sensor. So the water needs to be at 195 for the car to fully lean out at normal operating temperature.

Also, I'd bump the timing up a couple of degrees, try 5 degres advanced. Also, I'd change out the rear end grease with a synthetic, like Red Line. I'd also run a full synthetic motor oil. I'f you don't want to go that route, I would run 1 QT of Moble 1 with what ever regular oil you use. Maybe the best way to improve milage would be to throw out the points and get a Pertornix.

With these few things you should be able to eak out a couple more MPG's

Good Luck

[BQS4]

Actually, it still comes down the the fact that you're driving a "boxcar" shaped car through the air, Cof D is what we're taking about here. I can say this as I own a Sportwagon (or 3 ) and a GT. The GT gets far better mileage, even before I swapped to the 5-spd, but, that's due to the aerodynamics of the body.

[RallyBob]

Since the injectors are Bosch pintle-style and are 31 years old, they are probably not sealing up too well when closed, and are contributing to the lower mileage you're getting.

But as mentioned by others, there are numerous strikes against you. It IS a boxy sedan style, you have an auto trans, and it is a low compression engine (less efficient). So your mileage is not really out of the norm.

I used to get 23-24 mpg from my stock '73 Ascona (32,000 miles in 1992)with a 4-speed, 3.44, and a Weber 32/36. When I built a high compression 2.0
litre engine for it with a 38 DGAS, a ZF 1:1 5-speed, and a radical cam, I got 22 mpg. More than twice the stock power, but also more efficient, so barely any mileage was lost unless my foot was into the throttle.

Bob

[Opelkurt]

Originally Posted by Paul Kurt, I think 21 mpg is a little low. The 75 FI model used a "Special" thermostat. If you are using the standard looking thermostat, then the water never heats up to the proper temp and the car will run a bit on the rich side. The injector pulse width is tied to the water temp by a negative coefficient temperature sensor. So the water needs to be at 195 for the car to fully lean out at normal operating temperature. Also, I'd bump the timing up a couple of degrees, try 5 degres advanced. Also, I'd change out the rear end grease with a synthetic, like Red Line. I'd also run a full synthetic motor oil. I'f you don't want to go that route, I would run 1 QT of Moble 1 with what ever regular oil you use. Maybe the best way to improve milage would be to throw out the points and get a Pertornix. With these few things you should be able to eak out a couple more MPG's

Excellent advice. So good in fact, that I had already done all of those things! The Pertronix really helped the power curve at higher RPM where the old points showed their limitations the most. And it is running at the proper temperature with the correct thermostat.

I suspect Bob is on the mark regarding the injectors; they are the originals and they're probably worn and crudded up as well. After I check all the basics like fuel pressure, etc., I may round up some new or reconditioned injectors from OGTS. Or if anybody has some NOS laying around, let me know?

I also have a 1.5 head with 1.9 valves, unshrouded, that I'm planning to install this summer. Should get a small bump in horsepower and mileage with that. I know it won't work miracles, maybe 2-3 mpg, and ~8 hp?

-Kurt

[jordan]

I belive it is cheaper and a better use of money to get the old injectors cleaned, flow tested, and calibrated by a company like rc engineering www.rceng.com their website explains what they do and it can make quite a large improvement, even brand new injectors can be bettered by their procedures. Where should one begin to look for brand new injectors anyways?

[Opelkurt]

Originally Posted by jordan I belive it is cheaper and a better use of money to get the old injectors cleaned, flow tested, and calibrated by a company like rc engineering www.rceng.com their website explains what they do and it can make quite a large improvement, even brand new injectors can be bettered by their procedures. Where should one begin to look for brand new injectors anyways?

That sounds like good advice.

Opel GT Source has new injectors for $45 each, and rebuilt for $39 each.

-Kurt

[Rionart]

Right now OGTS is out of stock on new injectors....I just bought the last 3 and am waiting patiently for more to come in....

[David McCollam]

There are several injectors services that charge anywhere from $15-35 per injector to clean, including new seals for the injectors and feed hose.

Try these guys. http://www.witchhunter.com/injectorserv1.htm

Good luck,

Dave

[GTJIM]

Originally Posted by jordan Where should one begin to look for brand new injectors anyways?

The early fuel injected Jaguar V12 has the same Bosch '0 280 150 105' injectors .....
Three Opel sets on each motor....

Have a look at this thread: http://www.opelgt.com/forums/factory...fuel+injectors

[RallyBob]

Use caution cleaning old injectors. Often the flow pattern goes to heck because of metal erosion at the pintle and seat....and when you clean all the gunk away the pintle seals even worse. The best route is probably replacement.

[jpavlack]

Whatever the reason, the 2dr ascona was actually the LIGHTEST of the opel models in '75, not the heaviest.

[opelnut10]

Your right Joe, the two door Ascona is lighter than the Manta and the Ascona Wagon. With the big boumpers and the beams in the doors and the bigger, heavier brakes on the 75 they are the heaviest Opels imported to the US. Add the flat front end and extra requirements to push 80hp through a TH180 transmission and they are going to require more gas to operate than a lighter, more areo-dynamic car with more HP.

[Paul]

Something else that hurts the Aero.. is if the rear springs are sagging. Mantas have a tendenancy to sag in the rear. So, when the rear is lower then the front sits up more catching more air causing lift and drag. You might try cutting 1/2 a coil from the front. The point is not to substantially lower the front, just to bring the car back to level. Might be worth 1 mph.

Other things to consider... make sure the rear brakes aren't dragging and the front wheel bearings freely and you find any vacuum leaks.

If you want to get hard core you can always remove the windshield wipers... or follow a semi very closely

[Opelkurt]

Originally Posted by Paul Something else that hurts the Aero.. is if the rear springs are sagging. Mantas have a tendenancy to sag in the rear. So, when the rear is lower then the front sits up more catching more air causing lift and drag. You might try cutting 1/2 a coil from the front. The point is not to substantially lower the front, just to bring the car back to level. Might be worth 1 mph. Other things to consider... make sure the rear brakes aren't dragging and the front wheel bearings freely and you find any vacuum leaks.

It's an Ascona..... The brakes and bearings are all up to spec.

Good point though..... it was sagging when I got it, which made it look like a granny-mobile to me. The rear springs were each broken in two places, so I subbed in a nice pair from a '74 Sport Wagon. They hold the rear up very nicely, appearance was improved 100%, it handles better and they didn't hurt the ride (a nice surprise) even though they're stiffer than the originals.

-Kurt

[Paul]

Well, I've run out of ideas. You've done all of the inexpensive things. Short of mounting an electro magnet on the front of the car and get a pull from the car in front of you......

Sounds like you have a nice running and very dependable ride. Wish I could have been of more help.

[Opelkurt]

Originally Posted by Paul Well, I've run out of ideas. You've done all of the inexpensive things. Short of mounting an electro magnet on the front of the car and get a pull from the car in front of you...... Sounds like you have a nice running and very dependable ride. Wish I could have been of more help.

Hey, you nailed everything; it's good to know I've covered a lot of the bases already. From the responses it sounds like the car is simply on the low side of normal for mpg.

I bet I'll find a couple more miles mpg with fresh injectors, and the 1.5 head should add a couple more. That would put it in the mid 25 mpg range, fine for a 30+ year old car w/ a 3-speed slush box.

And yes, it is a great ride in great shape; I'll post pics when it comes out of storage next month.

-Kurt

[opelnut10]

Putting the 1.5 head on the engine will help it as far as power, with the sprint exhaust manifold I would go to 2" system and do away with the rear muffler. Just run the 2" in 2" out free flow muffler and packed tips to cut down on the sharp exhaust tone. Those changes shold net you about 8-10 HP and make it pull better in mid-range, which is where you are doing most of your driving.

[Sportwagon75]

Kurt - I have a number of 75 Opels. Be sure to check your fuel pressure to make sure it's within factory specs. The regulator can often be sticky after 30 years and the pump can be weak. Others have already mentioned the proper thermostat. The higher temperature was intended to help atomize fuel more efficiently with the F/I. Also...you would probably know if it was leaking severely...but make sure your cold start injector is not leaking. You can also play with the timing a little to improve MPG. Also...does the car still have the EGR system intact? It's another common source of trouble. Also, is your clutch fan working properly? It can sap a little power if not working right. If you have stock exhaust, consider increasing it to 2". Check the rubber rings that seal the fuel injectors. Make sure they're not dry rotted or cracked. Air can leak around them. New seals are readily available. Lastly...the stock air intake is somewhat restrictive with all of its twists and turns and changes of direction. If you're still using the stock air cleaner...consider using a K&N element to lower restriction and make sure you're pulling cold air from the grill area as intended. I use Pertronix in mine and if it doesn't improve mileage(I believe it does) it certainly makes it more reliable.