staticattic

I know all three are supposed to work well together. What I don't understand is the math behind the system. For example, I have 4 different styles of exhaust and I change them about every other month or so just to do something different. I have two types of stingers, a hide out muffler, and dual quiet packs. During my carb saga, I had left on the hide out muffler. When everything was done with my carbs, I had the engine running very well with one exception. While driving on the military base, most of the roads I drive down have a speed limit of 25mph. I usually cruised that speed in 2nd gear. After I got my carb issue worked out, my car would "buck" while doing that. When I got to the end of the cruise, either via a stop sign or an increase in speed, my car would sound like I was shooting a deer. I fixed that by shifting to 3rd and the problem went away. I never really thought much about it again since that was the only hiccup I had. I recently changed the hide out muffler to dual quiet packs. Did not open the hood and touch anything. With the dual quiet packs on, my car pops a little while idling, but I can drive it at 25mph in 2nd gear with no problems and definitely no shotgun blasts. My question, how are the three related? What is the math to figure out the best setup?

Jeff
72 Super Beetle
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fatalifeaten
It's partially about the amount of back pressure the exhaust/muffler provide. They flow differently and so you will see a bit of variation in the engine's behavior depending on the exhaust.

Honestly though, it sounds like your carb and maybe your timing are still a little wonky. Popping at idle's usually a sign of a vacuum leak, and the loading up in second gear and backfiring when you clutch sounds like a fuel delivery or timing issue.

Daily Driven Dubz Phoenix AZ Family


'66 Deluxe
'63 Deluxe ragtop
'61 Deluxe
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staticattic
IRT the popping during idle, the simple solution, according to the Webber book, is to play a little with the mixture screws. I hope that is all it is. With all I went through with my carbs, I hope I don't have a vacuum leak again. Or worse, a fuel delivery problem or timing issues.

I was just curious as to doing the math to figure out exactly what type of exhaust and how much back pressure would be the optimal solution for a given setup. I think I read somewhere, back pressure is better utilized at lower speeds, while no back pressure is better during wide open throttle. I guess the trick for daily driver type cars is to find a happy medium. For mine (with its current setup), it seems the dual quiet packs work the best. 
Jeff
72 Super Beetle
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fatalifeaten
Back pressure, shcmack pressure. Just run a stinger!



I actually ran a single QP when I did the break in on my last 1641 and it drove like it was bottled up. Once I dropped the stinger on, runs like a scalded dog. Back pressure is where it's at

Daily Driven Dubz Phoenix AZ Family


'66 Deluxe
'63 Deluxe ragtop
'61 Deluxe
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staticattic
I got off lucky this time. Playing around with my mixture screws seemed to do the trick. On the snail gauge, cyl 4 was at 7 while the rest were at 5. I never could get them all perfectly aligned, but they are now all between 6 and 6 1/4. I don't have a tach, so I have no idea what my idle speed is, but just going on the sound, I don't think it increased at all.

I also totally re-did all of my fuel lines. I now only have one filter, just after the hard line where it comes out underneath the car. No filters in the engine compartment and all new rubber. One major problem that I discovered, was my stomach. Before we went on our cruise, I could comfortably crawl underneath without the car jacked up at all. This time, I had to suck in my gut to squeeze under the jack point under the running board. Also, it used to be when I was completely under the car, with my feet towards the front, my gut would just barely touch the floor pans. Now it solidly touches the floor pans. Either my car is getting lower or my gut is getting bigger. Looks like I need to quit dinking around with the Bug and get on a treadmill.   
Jeff
72 Super Beetle
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fatalifeaten
*chuckle*

They will settle over time if you lower them. Mine settled nearly 2 inches when I dropped the front.

Go with that theory!

Daily Driven Dubz Phoenix AZ Family


'66 Deluxe
'63 Deluxe ragtop
'61 Deluxe
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Ryan
If you're getting more than 5 on the snail gauge, then your idle is too high.  Even a bigger 2332 will be right at about 5 at an 850 idle.  I keep my idle around 950 on my 1915 and I'm only pulling about 4.5 on my gauge.  If you set your mixture screws while it's idling that high, then they will actually be set too lean and can screw with the transition circuit.  You really should get a tach for this purpose alone.  --Ryan
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staticattic

Yesterday when I was getting back from walking my dog, I noticed a spray of oil on my driveway that matched perfectly with the curve of the rear of my car. I opened my decklid and found a fine mist of oil all over the engine compartment. It is obviously getting flung from the fan belt and appears to be coming from the area behind the bottom pulley. To top that off, while I was looking around my engine bay, I also came across the final mixture screw for cylinder number 4. I may not have the proper name for it, but it is the screw with the nut jamb almost right beside the spring loaded mixture screws on the carbs. Those were all tight at one time, so I am not sure how that screw vibrated out. Lately it seems, if it is not one thing, it is something else.  

Jeff
72 Super Beetle
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