New Owner of a 1981 4door VW Rabbit Diesel**47.5MPG**Baseline - Page 9 - Fuel Economy, Hypermiling, EcoModding News and Forum

JQmile · 03-01-2014, 08:34 PM

Quote:

Originally Posted by aerohead

The following are from a CAR and DRIVER road test of a VW Rabbit Diesel,reported,November 1979, measured at constant highway speeds (probably at Chrysler Proving Grounds which is just a hop skip and a jump from C&D's office at the time)
__________________________________________________ _______________
80 mph = 27.0 mpg
75 mph = 30.0 mpg
70 mph = 34.5 mpg
65 mph = 41.0 mpg
60 mph = 47.0 mpg
55 mph = 52.0 mpg
50 mph = 57.0 mpg
45 mph = 61.5 mpg
40 mph = 62.5 mpg
This car may be a bit different but the trend line may be similar for the speed differentials.

That was kind of my experience with my Chevette. As near as I could figure, it's drag coefficient was somewhere around .45, which is horrible. When I tried to pulse and glide with that much wind resistance against a 2,200lb car, it was like I was throwing an anchor out the window. Low speeds is your friend in any boxy-shaped vehicle.

Cobb · 03-02-2014, 05:22 PM

I had a 81 mercedes 240d. 475 thousand miles, rust everywhere, original everything. Anyhoo got to the point needed starter fluid in 80 degree weather. Before I called the kidney foundation to tow it away I went joy riding through a through fields. I decided to test the governer/rev limiter and see where the power is and what it sounded like reved up. I normally babied it considering the age, miles and the fact it took 2-3 days for parts when it needed service. Man I was able to do 25 mph in 1st gear, 50 in 2nd, 70 in 3rd. This is a 4 speed with over drive, so 4th was a much higher gear than the rest. I normally shifted into 4th at 35mph.

It hauled ass and I had some fun doing donuts once the engine was wound up. It went from sounding like a clattery diesel engine with solid lifters to a roaring 454 v8 with open headers.

I got 32 mpg regardless of driving style.

Quote:

Originally Posted by Christ

I'll be the first to let you know that 'drive it like you stole it' is actually a viable fuel economy driving style for diesel mechanical cars.

bigchelis · 03-05-2014, 01:19 PM

Well, I just filled up again yesterday.

338 Miles and 6.5g of Diesel....DARN IT

Stuck at 52 MPG.

The exaust just makes it fun, but definitely no improvement IMHO. Back to the drawing board.

Good thing is I still havent put a front air dam or any aeromods. So, that will be my next move.

I actually have the opportunity to purchase a 1980 VW 1.5L with 4speed.
I hear while the Head Bolt/Gasket issues can be bothersome the smaller 1.5L gets 55MPG and them some with more ease.

bigC

Cobb · 03-05-2014, 06:22 PM

What wrong with that?!?!?!

Not bad for a 33 year old car.

1.5? The Dasher had a 1.3.

Displacement is one thing, the amount of fuel dumped into the engine is another. You ca try adjusting the screws on the pump or the nut behind the steering wheel.

Christ · 03-06-2014, 02:46 AM

Quote:

Originally Posted by bigchelis

Well, I just filled up again yesterday.

338 Miles and 6.5g of Diesel....DARN IT

Stuck at 52 MPG.

The exaust just makes it fun, but definitely no improvement IMHO. Back to the drawing board.

Good thing is I still havent put a front air dam or any aeromods. So, that will be my next move.

I actually have the opportunity to purchase a 1980 VW 1.5L with 4speed.
I hear while the Head Bolt/Gasket issues can be bothersome the smaller 1.5L gets 55MPG and them some with more ease.

bigC

As soon as you get it, remove the head and get a ARP stud kit. There isn't one specifically for that engine with the 11mm head bolts, but they can build a kit for you that will work.

Barring that, you can also get some threaded rod in the grade 8, cut it to size, and use that in the same way.

The problem with the head bolts is that the recess in the block is a blind hole and very close to an oil galley or water jacket or something... it cracks when you overtighten the bolt, which basically everyone does.

Don't trust 'I wont overtighten it'... just replace the bolts with studs. Unless you want to research which hole cracks and trim that bolt down by about 3-4 threads so it doesn't contact the bottom of the blind hole. The other option is lots of machine work to finish drilling that hole all the way through and apply sealant to the threads of that bolt when you install it.

bigchelis · 03-06-2014, 02:57 AM

Quote:

Originally Posted by Christ

As soon as you get it, remove the head and get a ARP stud kit. There isn't one specifically for that engine with the 11mm head bolts, but they can build a kit for you that will work.

Barring that, you can also get some threaded rod in the grade 8, cut it to size, and use that in the same way.

The problem with the head bolts is that the recess in the block is a blind hole and very close to an oil galley or water jacket or something... it cracks when you overtighten the bolt, which basically everyone does.

Don't trust 'I wont overtighten it'... just replace the bolts with studs. Unless you want to research which hole cracks and trim that bolt down by about 3-4 threads so it doesn't contact the bottom of the blind hole. The other option is lots of machine work to finish drilling that hole all the way through and apply sealant to the threads of that bolt when you install it.

Yeah the head bolt issues sound like a pita
I actually was about to drive 4 hours to pick it up only to find out the 2 and 4 door Rabbits are same lenght !!! Only reason I wanted a 2 door was because I thought they were shorter lenght

Christ · 03-06-2014, 03:18 AM

yep the doors are different but the chassis is the same.

See if you can find a diesel rabbit p'up. Those are nice utes.

Cobb · 03-06-2014, 06:16 PM

Well, I dont know about all that. I just know many new owners do not take the car back to the dealer for the required maintenance of getting the stock head bolts retorqued.

+1 on the 3 square, spline, torex and hex heads. Those cars use a range of "allen head bolts" that requires special tools for stuff like the head and the cvc axle bolts.

Think I removed the head on my 79 dasher with the 1.3 is with a 10 mm hex end socket. Blew head gasket between 2-3 cylinder towards the exhaust/rear of car.

Christ · 03-07-2014, 02:03 PM

Yea, don't make the mistake of using the wrong tool... lots of guys try to use the Torx sockets for the triple square bolts, etc... they're nto gonna work right, and best case scenario, you break the tool rather than the engine.

ECONORAM · 03-10-2014, 10:55 PM

Quote:

Originally Posted by Christ

As soon as you get it, remove the head and get a ARP stud kit. There isn't one specifically for that engine with the 11mm head bolts, but they can build a kit for you that will work.

Barring that, you can also get some threaded rod in the grade 8, cut it to size, and use that in the same way.

The problem with the head bolts is that the recess in the block is a blind hole and very close to an oil galley or water jacket or something... it cracks when you overtighten the bolt, which basically everyone does.

Don't trust 'I wont overtighten it'... just replace the bolts with studs. Unless you want to research which hole cracks and trim that bolt down by about 3-4 threads so it doesn't contact the bottom of the blind hole. The other option is lots of machine work to finish drilling that hole all the way through and apply sealant to the threads of that bolt when you install it.

If you had an 81 or newer, I'd sell you my head studs. At least i think they are for the 81+. I'll have to look. Even back then, head bolt torque was a concern. My parents had a 78 diesel 2door that would get 48-49mpg. They ran 23.5 CR, a half-point higher than the 1.6s, and they'd rev just a touch higher.

Make sure the bottoms of the bolt holes are well cleaned out with a bottoming tap before running the head studs down..or you'll hydro lock any fluid at the bottom of the holes and CRACK!