Itinerant Air-Cooled

VWinVT wrote:

dingo wrote:1. hill climbing is an important issue....but does that not relate to torque instead of horsepower ?

2. How does an engine builder make money building Type 4 engines to the expectation of owners/drivers ? and still be cheaper than Subbie ? There is the rapidly decreasing availability of good factory parts, the aftermarket sub-quality uberkrap and/or used parts....which itself takes so much time and meticulous micro inspection just to verify usability ? Installation, shipping, warranty, returns...it is obviouosly a sustainable business or it wouldnt exist, but still, it boggles my mind...what am i missing in this picture ?

1. I always thought it was horsepower that allowed you to maintain speed on hills.

2. I don't get it either....the type 1 motors have many quality options and can be modified to make lots of HP...maybe we should be putting those motors in our busses....

The weaker cases, poorer cooling setup make High hp/torque Type 1 motors a poor choice for a 4000lb bus.

1. Without filling our forums with gobbledygook, horsepower is a function of torque.
to simplify your gobbledygook..

Horsepower is a function of torque AND rpm.

Torque is a function of cylinder pressure and crank stroke

so when climbing a hill, whats your rpm ? and how much does your engine rely upon it (type 1 more, late type 4 less)

VWinVT wrote: I always thought it was horsepower that allowed you to maintain speed on hills.

Depends on how you are going up the hill . . .

Staying in 4th gear at 50 mph on a hill because you can, is using the greater torque of the Type 4 engine.

Downshifting into 3rd at 50 mph and screaming up the hill at 4,600 rpm with a Type 1 engine, is utilizing the horsepower.

Does the dependance on RPM compromise engine longevity ?

dingo wrote:Does the dependance on RPM compromise engine longevity ?

Do you mean, "does a faster crankshaft RPM compromise engine longevity?"

Yes, generally. If you run a VW T1 engine at 5,500 RPM all day, you'll destroy something. If you don't destroy anything on the cooling fan/generator shaft, you'll pound out the bearings and saddles. If you run an Indy car engine at 5,000 RPM all day, it might not even break in fully. So it depends on the engine, and how you run it. The T4 power plant produces more horsepower higher up the RPM range. Where a T1 reaches its peak horsepower somewhere around 4,400-ish, a T4 engine (depending on build [914/bus/411]) will reach it in the ballpark of 5,000. Actual figures may vary. VW was clever with their gearing; if you hit the maximum horsepower output in one gear and then upshift, you will hit the maximum torque output in the next gear up. This is shown when the owners manual says something like "you may briefly exceed these [maximum] speeds for maximum acceleration." Colin detailed it excellently in the "shift points" articles on this site in the vehicle forums.

Robbie

asiab3 wrote:

dingo wrote:Does the dependance on RPM compromise engine longevity ?

Do you mean, "does a faster crankshaft RPM compromise engine longevity?"

Yes, generally. If you run a VW T1 engine at 5,500 RPM all day, you'll destroy something. If you don't destroy anything on the cooling fan/generator shaft, you'll pound out the bearings and saddles. If you run an Indy car engine at 5,000 RPM all day, it might not even break in fully. So it depends on the engine, and how you run it. The T4 power plant produces more horsepower higher up the RPM range. Where a T1 reaches its peak horsepower somewhere around 4,400-ish, a T4 engine (depending on build [914/bus/411]) will reach it in the ballpark of 5,000. Actual figures may vary. VW was clever with their gearing; if you hit the maximum horsepower output in one gear and then upshift, you will hit the maximum torque output in the next gear up. This is shown when the owners manual says something like "you may briefly exceed these [maximum] speeds for maximum acceleration." Colin detailed it excellently in the "shift points" articles on this site in the vehicle forums.

Robbie

Now that I read this, it makes perfect sense. I've always wondered y I can let the rpm's lag down In 4th going up a hill and it will usually hold speed at about 42mph with low rpm's. Not to mention the CHT's tend to,like this 'torquey' driving too.