intake cross section & torque 1

[rennkafer]

Hi,
I was talking to someone yesterday about trying to improve performance by converting a 1641cc VW engine from single port heads to dual ports. He made the statement that I might actually be better off in this instance (dunebuggy with big tires - thus high geared) sticking with the single ports, because the reduced cross section area of the intake would cause an increase in air fuel velicity, and a corresponding increase in torque. He thought I should go ahead and install my dual one barrel carbs onto the single port heads. (sacrafice top end for low end torque) Am I going to see a significant increase in torque by sticking with the single ports to make it worth giving up the top end? The engine has a mild cam and a low budget header..neither of which I plan on messing with. The single port heads and tiny stock carb really seemed to be choking the life out of this engine when I had it in my Bug.
Thanks!
Steve Steven K. Madoski
Mechanical Engineer
Ocean Systems Division
NFESC, Code ESC 52
Port Hueneme, CA

 

[evelrod]

Steve, this is just my opinion, but I would go with the dual port heads suitably reworked for performance work, mount a pair of 40mm IDA Webers with the longest velocity stacks (air horns) I could find along with the BIGGEST K&N air filter I had room to mount .

Use 28mm to 30mm chokes ,f11 tubes, 120-130 mainjet range to start(might be a little rich) 180 or so air corrector jets( again might be a little rich) , 45 pump jets will do to start(top end jetting is controlled largely by pump jet bleed) This is just a generic set up for 1600 cc engine with headers and performance cam. Your engine may , and probably will vary considerably from these specs. Go to your local speed shop and by the performance book on VW and I'll bet you will find all the skinny on jetting.

Stick with the mild camshaft and small headers .Keep your compression ratio within reason so the thing doesn't over heat.(boosting the compression ratio is the one thing you can do to the engine that will give you a boost throughout the powerband, bottom to top. Just don't overdo it)

With this setup, your low and midrange will be great, and you might be surprised how well it runs in the top end , too. Use the highest octane fuel needed and hold your timing advance a little on the low side .


Rod