Type 4 fan speed

[oprn]

I am putting a type 4 engine into a Manx copy and am wanting to gear it up some with tire size to gain a bit of mileage, reduce noise and engine wear. I understand that the type 1 engine needs to run in the low 3000 rpms minimum to get sufficient cooling under load on the highway. What about the stock type 4 fan? I believe the type 4 transaxle is a bit higher geared than the type 1 and the car is also heavier. Does this mean that the type 4 fan is more efficient at lower rpms?

I did change out the rear tires this summer to ones that were about 2" taller and the old 1600 DP did gain about 10 degrees on oil temperature at the same speed so that is why I ask.

[oprn]

Ok, maybe I should reframe the question differently.

What was the final drive ratio on the 411/412 cars and what was the stock tire size?

[dawie]

Final drive of 411/412 manual transmission:
(These are for "rest of the world" models, USA versions might differ.
sedan:3.72:1
wagon: 3.91
Both had direct 1:1 4th gear.
Wheels:
sedan 15 inch, 155 wide
wagon:
15 inch, 165 wide.

Airflow of type 4 fan:
800 liter/sec @ 4500rpm,
710 liter/sec @ 3600rpm

As a comparison, late type 1 wide dual port fan:
600 liter/sec at 4000 "engine rpms".
Single port fans had less.

These are VW's spec as per various publications.

[oprn]

Thank you very much!

That was the kind of info I was looking for. Presently the Buggy drags bottom coming out of parking lots so I want to raise the back end some for that reason as well as wanting to gear it up on the highway for better mileage and lower noise. It is a swing axle now so I do not want to re-index the torsion bars for increased ride height as that would put it into a positive camber situation with the danger of the rear "jacking" in hard corners. The Ralph Nader "Unsafe at any speed" syndrome... found not only on the Corvair but also VW, Mercedes, Peugeot, NSU and a number of others - including of course the Ford 1/2 ton twin I beam front end.

Interesting that there is that much more air flow from the type 4 fan! I wonder if the type 3 fan was more efficient than the type 1 as well?

I also wonder now too how folks get away with the type 1 fan on the type 4 engine!

[TZepeSH]

But do you know some numbers for type1 fan, to compare? How big is the difference?

[dawie]

Also remember that these flow figures are while pumping air through the total gap area between the fins of each corresponding type of engine. Type 4 also have more fin surface area than type 1.
Total combined cross-section of gaps between fins of type 4 being more, it would be slightly easier/slightly more flow to pump air in a type 4 application. (Compared to the same type 1 fan supplying a type 1 engine).

Type 3 flat fan:
580L/sec at 3800rpm, so close to type 1 dualport fan (which does 600L/sec at a higher 4000rpm).

[Clatter]

The type 4 heads have so much more finnage,
And the castings are of a very high quality.

In something like a light buggy,
Your big challenge would be getting it warm enough - having a proper working thermostat.

Short of some putting on some 44" swampers, I doubt you could get it too hot if you tried.
(Assuming all of the tin is in place and working)

[oprn]

Oh yes, all the tinwork will be in place. The only exception will be the vertical firewall tin. I am a bit concerned about recirculation of hot air from the cooling and exhaust systems re-entering the cooling fan due the fan being low and at the rear. I thought that leaving that tin off would encourage some cooler air from under the buggy to go over top the engine and displace at least some of the hot air that will be following the low pressure draught behind the engine. The type 1 engine in the buggy now is not bothered much by this as the cooling fan inlet is at the front of the engine and the fan shroud creates a fairly effective "dam" to direct cooler air from the fender wells into the fan.

As far as a thermostat, I have learned my lesson on that one. Like so many other "sheep" out there I followed the "big guys" in the magazines back in the 60s and 70s and threw all that junk away. You don't need it right? Well my Dad told me over and over I was making a serious mistake and guess what? The old guy was dead right! Man I wish I had all that "junk" now that I threw away, these engines tune and run so much better when the temperature is more constant. It's like night and day. I suspect they will last much longer too.

I have not fully resolved in my mind what the final exhaust system will look like. Type 4 systems are scarce and pricy with little for options. Again I do not want anything that will have a collector and muffler right at the cooling fan inlet. That eliminates everything commercially available at the present. Duals would put the exhaust to the side and would have the right "look" but at this point I am not prepared to accept the imbalance they will cause on the engine. Been there, done that! Four singles would work if quiet enough or turn a 4 into one system around, have the collector under the transaxle and a single muffler come back on one side. Then I lose ground clearance...

There is no easy solution but then if it was easy any idiot could do it, right? I like a challenge.

[Piledriver]

Perhaps look to the late water cooled Vanagon setup for exhaust inspiration...
Was a 4>2>1, each paired section (1,3/2,4) were ~equal length as was the secondary section, but with a 4>2>1 the individual cylinder runners can differ wildly, the total length of the pair being the critical dimension.

[oprn]

Yes I have looked at those systems and seen that most don't come very close to a tuned length set up. I wonder if the power penalty would be any worse than 4 singles? I really like the simplicity and compactness 4 singles would bring.

One of the hurdles I have encountered is that 1 5/8" exhaust tubing is not available in western Canada. I am told by someone in the US that it is readily available there and is marked "made in Canada"!

Right!

So I have to pay duty, shipping and handling and the exchange on the dollar to buy our own made in Canada goods? Ha! That is an insult!

So someone up here makes it...

Oh! By the way I did a little temperature test tonight out on the highway:

ambient temp: 65* F

air temp directly behind the center of the engine at stock carb height: right around 120* F, a bit cooler close to the engine, increases to 120 about 8" back and stay close to that temp to at least 2 feet back then starts to drop off.

air temp directly behind the crank pulley: 140* F, stays at that for the first foot then drops off to 130 range at 2 feet and down to 120 further back.

The hottest spots were directly behind the engine and moving the temp probe to either side the temp came down fairly quickly. A foot either way made 15 to 20* difference!

That tells me that my hunch was right, the hottest spot behind the buggy will be exactly where the type 4 fan draws it's air!

[Piledriver]

Actually the factory 86+ 4-2-1 is a proper tuned length system.
On a 4-2-1 the tuned measurement is valve to valve distance between 1&3 or 2&4.
The individual runner length can vary, its the total length that counts.

4 individual pipes will cost you ~15% power or economy.

[oprn]

Interesting - I would not have taken that to be a properly tuned system.

So if the distance valve to valve counts then there must be back flow up against the closed valve. This should also apply to a regular 4 into 1 system not?

[Piledriver]

4 into 1 works much differently than a tri-Y.