# 1/2 VW versus Briggs, Kohler, Generac V-Twins

Discussion in 'Half VW' started by nheistand, Apr 14, 2011.

### Help Support HomeBuiltAirplanes Forum by donating:

Tags:
1. Apr 14, 2011

### nheistand

#### Member

Joined:
Mar 4, 2011
Messages:
23
3
Location:
Vinton, Iowa / USA
I see that the Generac and other V-Twin industrial engines are starting to show up on ultralight aircraft and powered paragliders. The great thing about these engines is the low cost, newer technology, and easy service/repair. They come with alternator, starter, and electronic ignition built in.

On the other hand, the 1/2 VW can be built with a magneto so no battery or alternator is needed so the weight can be kept down to 85lbs or so. Also the 1/2VW should be built with high performance parts like Mahle pistons, Scat Crank and Rods, etc. Everything in life is a trade-off. The cost for these engines will be about the same until you start putting extras on the 1/2VW like starter, alternator, etc. These parts can be very pricey. A nice 37hp 1/2VW with a magneto is $3400 without extras at Hummel Engines. However, I will build and sell a 37hp 1/2 VW for$2900 including prophub, magneto, exhaust, intake, and carb ready to go.

9. Sep 7, 2011

### AZSpyder

#### Member

Joined:
Aug 6, 2011
Messages:
7
0
Location:
Tucson, AZ
I think I am going to end up using a 1/2 VW myself. Hummel has them up to 45 HP. If the Hummel's numbers, and other suppliers HP for displacement too, are correct the bore/stroke I'm thinking about would be about 40. There are a lot flying but most have been with stock strokes at about 32 HP for half a 1835cc, or 918 cc. The 45 HP is at 1200 cc and seems to be about maxed out on heat extraction.

So far no one has gotten a redrive to work on the 1/2 VW. I think only belt types have been attempted and the torsional shock eats them alive in minutes, but they are still trying. Maybe someday but it's been enough trouble that I wouldn't experiment myself.

The 1/3 Corvair sounds interesting. The head looks very good for cooling. They seem to be about 32-35 HP and just under 900 cc. There is not the bolt in hot rod displacement available like the VW but some are adapting VW cylinders for some increase.

Jerry

10. Sep 7, 2011

### Rod1

#### Member

Joined:
Sep 6, 2011
Messages:
5
0
Location:
UK
In Europe the B & S engine is gaining popularity fast but I think the issue you will have is weight. The B & S engine is 51lb!

Luciole.co.uk

Rod1

11. Sep 10, 2011

### litespeed

#### Well-Known Member

Joined:
May 21, 2008
Messages:
1,530
310
Location:
Sydney
Me I personally like the JCV 360 Its only 67lbs wet as a complete solution and has plenty of smooth power. It uses proven 4 valve heads and barrels with a aircraft specific bottom end and redrive. The B & S might be 51lb but then it still needs extras and no redrive, electric start, water cooled.............. Verner Motor, Czech Republic - Home page

12. May 29, 2012

### georgehreed

#### New Member

Joined:
May 29, 2012
Messages:
1
0
Location:
Orlando, FL
Hey I see from an old post that you rebuild half-vw engines?
If so, could you rebuild mine? It's fully modified, but has been sitting a while. I want it broken down and inspected, everything checked out - I'm putting it on my minimax and I want as much power out of it as I can. I want low rate of fuel burn and torque.
Reply to georgehreed at gmail and I will send pics. I can ship it to you in about 2 weeks.

Thanks,
George

13. Feb 10, 2015

### Armilite

#### Well-Known Member

Joined:
Sep 6, 2011
Messages:
3,111
251
Location:
AMES, IA USA
===============================================================================
What is the 1/2 VW Spec's you talk of:
Bore & Stroke
Intake Valve Size
Exhuast Valve Size
Carb CFM
Compression
CAM Lift & Duration

Rich

14. Feb 10, 2015

Joined:
Sep 6, 2011
Messages:
3,111