Kamback for a station wagon?

[kingsway]

I have a VW Golf 1.9 SDI (Diesel) Mk 4 - It's an Estate Car (Station Wagon) so not exactly good aerodynamically!

I'm wondering if a Kammback might help me? Has anyone any experience with this type of vehicle?

Mind you - I got 60 mpg imperial (49.96 mpg US) on a recent long run. Raised tyre pressures, half-blocked radiator (Grills still open for the moment) and keeping to about 60 mph and DWB as much as possible - in very flat country.

[euromodder]

Welcome to ecomodder.

A Kammback will work the same on an estate as on a hatchback.


With most of Europe in the freezer these days, you won't need much cooling ;-)
The upper grille can safely be closed off - many have blocked (part of) the lower grille.
Always keep an eye on temperatures when blocking grilles.

If you haven't tried coasting to slowly reduce speed - give it a try.
(I keep the engine on for power steering and power brakes , others even kill the engine)

[kingsway]

Originally Posted by euromodder

Welcome to ecomodder.

A Kammback will work the same on an estate as on a hatchback.


With most of Europe in the freezer these days, you won't need much cooling ;-)
The upper grille can safely be closed off - many have blocked (part of) the lower grille.
Always keep an eye on temperatures when blocking grilles.

If you haven't tried coasting to slowly reduce speed - give it a try.
(I keep the engine on for power steering and power brakes , others even kill the engine)

I have yet to block the actual grills - so no aerodynamic advantage yet - but have blocked-off about two-thirds of the radiator to good effect. It's warming up in half the time, and no sign of the temp being too high (it's about 0 deg C at the moment!

I'll be interested to see if a few minor mods can bring about any useful savings. I tend to get similar mpg figures however the car is driven...

I must admit I haven't really tried coasting - I live in a very flat area of the UK, and see heavy traffic pretty much all the time, so not that much opportunity!

My little i litre 3 speed automatic Daihatsu is the one that guzzles fuel - costing slightly more to run than the (manual) Golf which is nearly twice its size! (By about UK£1.00 per hour.)

I am a Driving Instructor, so most of my mileage is done with a novice at the wheel. Only towards the end can I start introducing them to Eco-Driving techniques!

BTW I can't afford a Scanguage - I don't think it will work with my VW anyway - but am using a very low cost Android APP called 'Torque' on my smartphone and a very cheap (less than $10) Bluetooth OBD2 adapter.

Due to the non standard protocols used by VW I can read a lot of things, but not fuel consumption on the VW. Works 100% on the Daihatsu however.

[Piwoslaw]

Welcome to EM

A Kammback is very much doable on a stationwagon! In my case it (with rear skirts, the significance of which I'm not sure of) reduced fuel consumption by 8% @ 100 km/h (see my mod thread in the sig). You can even slap a long boattail on, like Weather Spotter did, for even better results.

Originally Posted by kingsway

I must admit I haven't really tried coasting - I live in a very flat area of the UK, and see heavy traffic pretty much all the time, so not that much opportunity!

You don't need hills and long slopes to coast, just do it anywhere you can. My area is also flat - there are only a few places where I can coast for more than 300-500m. It's more about feeling the flow of traffic and knowing where and when to pop into neutral. But you should know that as driving instructor.

And don't worry about engine off coasting yet - you won't be doing it too often with a turbodiesel.

Originally Posted by kingsway

My little i litre 3 speed automatic Daihatsu is the one that guzzles fuel - costing slightly more to run than the (manual) Golf which is nearly twice its size! (By about UK£1.00 per hour.)

And you still have it? Either swap the trans for a manual, or get rid of it!

And get those grilles blocked!!

[kingsway]

Originally Posted by Piwoslaw

Welcome to EM

........ where I can coast for more than 300-500m. It's more about feeling the flow of traffic and knowing where and when to pop into neutral. But you should know that as driving instructor.

spend a large part of my day teaching people to NOT coast!!

And don't worry about engine off coasting yet - you won't be doing it too often with a turbodiesel.

My car is a non-turbo, hence the SDI ('S' being for suction) - which is why I get such good MPG as standard. the TDI gives almost double the power of my car...

Originally Posted by kingsway

My little i litre 3 speed automatic Daihatsu is the one that guzzles fuel - costing slightly more to run than the (manual) Golf which is nearly twice its size! (By about UK£1.00 per hour.)
And you still have it? Either swap the trans for a manual, or get rid of it!

And get those grilles blocked!!

I bought the little automatic to test the water and see if there is enough business to be had teaching automatic here in the UK. The jury is still out on that one. Why do I uses such a thirsty little car? Its a 2003 model, previously owned by an old man who did only 9000 miles in it! So I bought the car for less than a tenth the price of a new car - and it's condition is still 'like new'.

That huge savings I made on the purchase price can help to pay for many
hundreds of litres of fuel - even at UK prices!

It is a bit 'basic' and uncomfortable, so I may well replace it at some point - otherwise, a conversion to LPG would pay for itself fairly quickly

I like the idea of making a few aero mods, and maybe drawing my customers attention to the benefits eco-driving. My problem is doing it in such a way that it doesn't look too un-professional!

[Sven7]

I'm assuming you have a MK4 Golf.



It has been said on here that Hucho's book warns against doing angled belly pans or Kammbacks on estates because of vortex formation. Saloons and coupes, due to their sloping rear rooflines, create pressure differences on the top and sides and when the air meets at the rear corners of the roof it creates a spinning vortex of air. This is bad because it increases your drag.

Estates, though, are already approximately an equilateral box. There is little pressure difference from the top to sides so you will have much fewer/smaller vortexes coming off.


You have A and you want F. A badly executed kammback could give you Ba

If you're going to extend the rear more than what Piwoslaw has, I recommend you try a partial boat tail. This is because adding too long of a kammback might create a pressure difference! But this should only happen if you by far exceed the vertical plane of the lower hatch.

3-Wheeler has a very nice looking boat tail on his Honda Insight and if you're worried about looking professional that would be the car to copy. Georgboy has a nice partial kammback on his Geo Metro which you may also want to take a look at.

I hope that all made sense. Then again you probably won't be going full steam ahead on the aeromods right from the get-go. Look into a belly pan, which may deliver something a couple mpg highway. For stop and go traffic though you'd probably be better off reducing weight. Remove the rear seat if possible, take out the spare tire if you have a roadside assistance program, and maybe buy some light alloy wheels.

Good luck!

[kingsway]

That is indeed the profile of my car, Sven.

Thanks for your input! Sounds like a small Kammback might not be sufficient to make all that much difference. I did wonder if a 'shelf' jutting out from the top of the rear door (as you see on several cars) might give a sharper cut-off and reduce turbulence at the rear?

If I did build a boat-tail, I think it would have to be easily detachable so I can use it on the occasional long-run, but leave it off around town.

I lived in sub-Saharan Africa for many years, and a lot of station wagons were fitted with air scoops at the rear to direct air onto the rear screen in order to keep it clear of dust. Can't imagine it did anything to reduce drag though!!

I'm currently cutting some Correx to block the grills - but struggling to make clean and decent looking cuts!! Looks like a bit of experimentation and practice might be required...

I have a reasonably long run across France, Holland and Germany planned for the summer - be nice if I could get something working before then.

[euromodder]

Originally Posted by kingsway

Sounds like a small Kammback might not be sufficient to make all that much difference.

The smaller it is, the less effect it'll have.

Making it bigger, you come into boat-tail territory

I did wonder if a 'shelf' jutting out from the top of the rear door (as you see on several cars) might give a sharper cut-off and reduce turbulence at the rear?

Volvo used 2 very small spoilers on the top of the rear door on its V50 models (MY 2007 on IIRC) - and they keep the rear window cleaner than on the same cars without them.

Rounded surfaces at the rear are not very good - hence you'll see more and more cars with hard ridges built into the rear lights or the bumpers to let the air detach cleanly.

I lived in sub-Saharan Africa for many years, and a lot of station wagons were fitted with air scoops at the rear to direct air onto the rear screen in order to keep it clear of dust. Can't imagine it did anything to reduce drag though!!

It'd have needed to be intricately designed and shaped in order to reduce drag - so no.
Though it's possible.

[jrscteg]

interesting

[kingsway]

The attached is my attempt at visualising what might be practical mods for my car - so long as I can end-up with a reasonably professional finish!

Grill delete
Smooth wheel covers
Rear Skirts
Mild Kammback