Thread: Ride Height & fuel consumption???

The secret is to earn enough as not to care

Originally Posted by rmp

Yes, a lift will increase fuel consumption. However, you'd need a lab to notice the difference. I agree with the others who say that tyres, gearing etc are more important.

To put it in perspective - a 50mm lift on a Series/90/110/Defender that is about 2m high, increases the frontal area and hence fuel consumption by about 2.5%, or, say, from 10.0 to 10.25 l/100km. Your consumption probably varies that much anyway, and as discussed above, most people make other changes such as tyres at the same time as they lift it.

John

I notice a bigger change when I have the roof bars on (not a roof rack). The bars add about 10% increase in fuel consumption).

Above 80km/h, the car lowers itself to low ride height (25mm below standard ride height), but this is for handling:

This setting lowers the vehicle’s centre of
gravity, thereby improving the handling
characteristics of the vehicle.

Ron

Originally Posted by DirtyDawg

The secret is to earn enough as not to care

Pretty close to it, but was just a curiosity.....
Fuel economy improvements will be a set of extractors with a good exhaust system & a fuel star added. Will measure the difference.

Am testing a FFI fuel pill that is supposed to improve fuel ecnomy...... results to follow.

Originally Posted by p38arover

I notice a bigger change when I have the roof bars on (not a roof rack). The bars add about 10% increase in fuel consumption).

Above 80km/h, the car lowers itself to low ride height (25mm below standard ride height), but this is for handling:

Ron

I presume you are talking about the P38 - it probably DOES have more or less laminar flow over the roof - but not with the roof bars. Interestingly the Citroen DS wagon I used to own had a fixed roof rack, whose front bar (only about 40mm above the roof, and about a metre fromm the top of the windscreen) was deliberately used to break the airflow away from the roof, this bar being covered in a corrugated plastic sleeve to make small eddies.

John

I read once that the roof lights on the Camel Trophy Freelanders increased their fuel consumption by 4mpg!

Larry.

Originally Posted by JDNSW

I presume you are talking about the P38 - it probably DOES have more or less laminar flow over the roof - but not with the roof bars. Interestingly the Citroen DS wagon I used to own had a fixed roof rack, whose front bar (only about 40mm above the roof, and about a metre fromm the top of the windscreen) was deliberately used to break the airflow away from the roof, this bar being covered in a corrugated plastic sleeve to make small eddies.

Yes, I was referring to the P38A.

Why did Citroen want to break up the laminar flow, John? They must have had a good reason.

Ron

Originally Posted by p38arover

Yes, I was referring to the P38A.

Why did Citroen want to break up the laminar flow, John? They must have had a good reason.

Ron

I can only speculate. The sedan had a step at the back end of the roof to break airflow away from the body (same effect as a Kamm tail, but less obvious), but the wagon had a step up rather like a disco at the back of the rear doors (and the back of the roofrack) and a rounded rear profile, and it may have been that keeping the airflow following the roof led to this less than ideal shape creating large scale turbulence, avoided by introducing small scale turbulence further forward. On the other hand they may have been committed to the roof rack on the wagon, and found that breaking the airflow away from the body at the front of it reduced the drag of the rest of the rack. But as I said, this is speculation - as it was designed almost fifty years ago, it is unlikely there is anyone about now that knows the reasons.

Thinking about it - that is a little uncanny - when the DS was introduced in 1955, the first car with fully self levelling suspension, load adjusted inboard disc power brakes, collapsible single spoke steering wheel, controlled collapse rate body, Cx of 0.33 - Rover had just updated the 80" Land Rover to 86" and was about to increase the wheelbase by two inches to accommodate a diesel. Another interesting comparison - the DS, with a wheelbase about the same as a 130 had a turning circle less than any Landrover ever built. The Landrover and Citroen DS were two landmark cars, both totally different to anything else, and neither really copied at all closely by anyone else.

John