quote:Originally posted by Kid:
There is a short movie of that 928 on Youtube, correct?
I bought a 40 year old car, partly because of the looks, and don't mind the old thing has some "issues", so why not IDA's
I actually feel the same way. I feel the modifications should be period correct and I actually use the Gp4's as a target/role model.
Actually on the tuning, Webers being "off tune" is actually a misnomer or an axie moron. If the are off, the car won't move out of the driveway.
What the issue is, is maximizing them for that day, just like you were racing. What ever the setting turns out to be, is the best the car will run on that day, and you leave it alone.
My setting is 140f/160a, F5 mains. .67f idle on the stock 110 idle air holder. The chokes are 40.5mm, which were custom milled down out of 3/16" thick wall aluminum tubing.
I will tell you that it will also run better on 170f/190a, and F7's seem to run as well as the f5's. The car will pull very, very, very hard on that setting and I actually like the color of the plugs better with it then the 140f combination.
Idle set screws are about 5/8ths of a turn out from the seat.
When the transition flat spot is there it is at 2800 to just under 3000 rpm.
I haven't got the courage to try the third hole yet. The problem is if it screws up the carbs, you have to solder the hole back up.
The IDA's have gotten a little pricey to screw around with them.
Here it is. You can see the third hole clearly in this picture. There are those that swear by it.
Here's a discussion about it from Club
Cobra.
http://www.clubcobra.com/forum...ransition-ports.html
This is the article the picture below is from.
http://www.aircooled.net/rebui...-ida-vw-carburetors/
The new third hole is the top one. The article states that the "newer" IDAs come with the three holes.
Anyone here have maybe the made in Spain 48IDAs of which they can check on?
Some have questioned if the third hole makes the idle heavier.
Apparently no, and because the venturi effect only draws fuel out of one hole at a time as it aligns with the throttle plate. The throttle plate moves in relationship to each hole as you operate the throttle.
It makes a lot of sense to add the third higher hole since it is "higher" in the rpm cycle that the idle circuit stops functioning and the dead spot occurs.
To make it operate at a higher rpm, it needs a higher transition hole. Seems ridiculously simple, but carbs are not rocket science.
This "tune ability" or flexibility is why many say the IDA is the carb to run even on the street.
It isn't just the V8s that see this transition issue. Virtually every engine the IDAs are used on exhibits the transition issue.
