Another carb tuning question, Problem solved!! |
|
Porsche, and the Porsche crest are registered trademarks of Dr. Ing. h.c. F. Porsche AG.
This site is not affiliated with Porsche in any way. Its only purpose is to provide an online forum for car enthusiasts. All other trademarks are property of their respective owners. |
|
Another carb tuning question, Problem solved!! |
Cevan |
May 20 2010, 01:09 PM
Post
#1
|
Senior Member Group: Members Posts: 1,079 Joined: 11-December 06 From: Western Massachusetts Member No.: 7,351 |
So I’m entering the wonderful world of carb tuning. (Please save all the FI comments. I couldn’t afford aftermarket FI and I’m using a cam not compatible with stock FI.) The engine is a recently built 2056.
I’ve sync’d the carbs using my STE meter. I adjusted the idle mixture screws per Aircooled.net’s website. It doesn’t appear to make a huge difference when I go from one turn out to all the way in, or from one turn out to two turns out. I adjusted them so that the engine ran the smoothest. The engine seems to idles nice. So I go for the first drive. After puttering down my long driveway in 1st gear, I pull out onto the road and it goes nicely through 4th gear, maybe at half throttle. At some point (maybe ½ to 1 mile into the drive) it starts to get boggy on acceleration. Definitely a change, so I head back home. This morning I started it back up. It’s still boggy, pretty much from 2000-4000. If I go WOT, it bogs worse. If I slowly increase the speed, it bogs less. And it smells like it’s running rich, like unburnt fuel (I did check for fuel leaks). I tried adjusting the idle screws some more. It seemed like I got it to run a little faster at idle. The engine revs fine with no load on it. I checked the carb balance again and went for another spin. Still boggy. Still smells like it’s running rich. For the next drive I need to pay more attention to any carb or exhaust popping. I’m trying to diagnosis this problem in a logical order. I’ve already checked the dwell, timing and valves. The carbs were just rebuilt. The floats are set per the Redine website. My plan is to pull a spark plug from either side and inspect them for signs of it running rich or lean. I’m also going to clean the idle jets as maybe something clogged the jets during the first drive. I’m also going to install a fuel pressure gauge so a passenger can see it while I drive (just in case it’s running lean), although the fuel pump is new. If none of this helps, should I try a different size idle jet? I have 50s already. Any other suggestions? Here’s the current setup: Weber 40mm IDFs Idles 55 Main 130 Air 200 Emulsion F11 Vents 32mm |
jmill |
May 20 2010, 07:21 PM
Post
#2
|
Green Hornet Group: Members Posts: 2,449 Joined: 9-May 08 From: Racine, Wisconsin Member No.: 9,038 Region Association: Upper MidWest |
It doesn’t appear to make a huge difference when I go from one turn out to all the way in, or from one turn out to two turns out. I adjusted them so that the engine ran the smoothest. Doesn't sound right. Go out farther than 2 turns. You can go like 5 before fear of the needle falling out. I'm thinking you haven't gone out far enough. You'll hear and feel a difference. It's not huge but you'll know when your passing through the sweet spot. If that spot is more than 2 1/2 turns out increase idle jet size. If your not advanced enough it will be boggy. |
Cevan |
May 20 2010, 07:45 PM
Post
#3
|
Senior Member Group: Members Posts: 1,079 Joined: 11-December 06 From: Western Massachusetts Member No.: 7,351 |
It doesn’t appear to make a huge difference when I go from one turn out to all the way in, or from one turn out to two turns out. I adjusted them so that the engine ran the smoothest. Doesn't sound right. Go out farther than 2 turns. You can go like 5 before fear of the needle falling out. I'm thinking you haven't gone out far enough. You'll hear and feel a difference. It's not huge but you'll know when your passing through the sweet spot. If that spot is more than 2 1/2 turns out increase idle jet size. If your not advanced enough it will be boggy. It does make a difference. I just thought it would be more pronounced. I will advance the timing and drive it again. |
Lo-Fi Version | Time is now: 27th September 2024 - 02:33 PM |
All rights reserved 914World.com © since 2002 |
914World.com is the fastest growing online 914 community! We have it all, classifieds, events, forums, vendors, parts, autocross, racing, technical articles, events calendar, newsletter, restoration, gallery, archives, history and more for your Porsche 914 ... |