I hate my Carbs Much Less, Chris Foley is a God! |
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I hate my Carbs Much Less, Chris Foley is a God! |
Mblizzard |
Oct 30 2013, 12:13 PM
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#1
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Advanced Member Group: Members Posts: 3,033 Joined: 28-January 13 From: Knoxville Tn Member No.: 15,438 Region Association: South East States |
Well after much playing and changing I have to say I hate my carbs. I have done every jet size and I can't really get it to run well on anything but 70 idle jets and that is way to rich. With 60s it runs not quite as rich but the hesitation on the initial throttle is huge.
Have played with the adjustments and I think I have it running well but it never performs well. 2056 just built, 44 IDFs, 60 idle jets, 28 vents, 135 mains, F-11 emulsion tubs, 175 air correction jets. Timing at 27 to 30. SVDA Dizzy with electronic ignition. Valves recent set and rechecked. Synced at idle and 1500 rpm. Runs well at higher rev and pulls strong but I can't get rid of that hesitation. I know there will always be some but at times from a dead stop it almost stalls. What am I missing? (IMG:style_emoticons/default/headbang.gif) (IMG:style_emoticons/default/headbang.gif) Gone through all of the Weber tech trouble shooting steps and I can't find anything that says I have something wrong. Is there an adjustment on the accelerator pump? Or do I need to up the accelerator jet? I will be going back to FI at some point but these carbs should work better than they do. Taking it to Eurohaus tomorrow maybe they will have better luck. Suggestions? |
rhodyguy |
Oct 30 2013, 12:17 PM
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#2
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Chimp Sanctuary NW. Check it out. Group: Members Posts: 22,093 Joined: 2-March 03 From: Orion's Bell. The BELL! Member No.: 378 Region Association: Galt's Gulch |
did you ever try backing one of the throttle stop arm screws off contact?
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DBCooper |
Oct 30 2013, 12:42 PM
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#3
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14's in the 13's with ATTITUDE Group: Members Posts: 3,079 Joined: 25-August 04 From: Dazed and Confused Member No.: 2,618 Region Association: Northern California |
You say "hesitation on the initial throttle is huge." What does that mean, exactly? Is it always from a "dead stop"? Meaning it falls on its face on the first touch of of the throttle? When you stab the throttle only from low RPM's, or only at high RPM's, or both? Or on a smooth application of the throttle it stumbles at some point as the RPM increases? All of those, or any of them more or less?
Are you using the Weber tech manual? It has (if I remember correctly) some values for the volume of gas from each full squirt of the accelerator pumps. Did you measure that? If not you can get a reasonable idea by watching the stream in each throat as you pump the carbs, but I guess you probably need to know what looks "right" first. to compare. Oh, and another thing that can cause a low-RPM stumble is low float level and not enough fuel in the bowl. |
rhodyguy |
Oct 30 2013, 12:54 PM
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#4
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Chimp Sanctuary NW. Check it out. Group: Members Posts: 22,093 Joined: 2-March 03 From: Orion's Bell. The BELL! Member No.: 378 Region Association: Galt's Gulch |
the carbs in the kit don't have a pump arm adj feature?
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7275914911 |
Oct 30 2013, 01:00 PM
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#5
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Hummmm!!! Group: Members Posts: 756 Joined: 7-May 08 From: Mid-South Member No.: 9,028 Region Association: South East States |
I want to say too much Carb for a 2056(does it have a cam?). On my 2056(9550) I am running 40idf with 32 vent, .55 Idles and 1.35 Mains. I am also running big headers and performance muffler. And I am very happy with the performance. Cable Linkage also. Really money well spent on that item!
Good Luck, Mike.... |
rhodyguy |
Oct 30 2013, 01:03 PM
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#6
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Chimp Sanctuary NW. Check it out. Group: Members Posts: 22,093 Joined: 2-March 03 From: Orion's Bell. The BELL! Member No.: 378 Region Association: Galt's Gulch |
iirc his venturies have been sized to 32s.
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Cap'n Krusty |
Oct 30 2013, 01:16 PM
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#7
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Cap'n Krusty Group: Members Posts: 10,794 Joined: 24-June 04 From: Santa Maria, CA Member No.: 2,246 Region Association: Central California |
Before we go any farther, what distributor are you running?
The Cap'n |
DBCooper |
Oct 30 2013, 01:30 PM
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#8
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14's in the 13's with ATTITUDE Group: Members Posts: 3,079 Joined: 25-August 04 From: Dazed and Confused Member No.: 2,618 Region Association: Northern California |
Said it's a SVDA and 28 venturis on a 2056, but didn't say what cam.
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Cap'n Krusty |
Oct 30 2013, 01:59 PM
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#9
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Cap'n Krusty Group: Members Posts: 10,794 Joined: 24-June 04 From: Santa Maria, CA Member No.: 2,246 Region Association: Central California |
Well, that's what I get for not reading the original post very well. Is the vacuum hooked up? Correctly? Is the timing set to what it should be with that distributor?
The Cap'n |
DBCooper |
Oct 30 2013, 02:27 PM
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#10
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14's in the 13's with ATTITUDE Group: Members Posts: 3,079 Joined: 25-August 04 From: Dazed and Confused Member No.: 2,618 Region Association: Northern California |
Cap'n, he said he'd tried timing between 28 and 32, so I'm assuming with a light at full advance. Mike, were you getting timing movement with a light when you varied RPM's? And for curiosity do you know what the timing was at idle?
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Mblizzard |
Oct 30 2013, 03:28 PM
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#11
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Advanced Member Group: Members Posts: 3,033 Joined: 28-January 13 From: Knoxville Tn Member No.: 15,438 Region Association: South East States |
Ok running through the list!
Stock FI cam. Floats are set to the recommended spec. Getting good movement of advance with rpm change. At idle the timing was just slightly advanced for TDC. Dizzy says 28 to 34 BTDC so I am in that range. The accelerator pumps seems to be putting out a good stream. Hesitation not present wit 70 idle jets. Huge hesitation is only at low rpm or dead stop. In 3rd gear at 3000 rpm going to WOT is a slight hesitation that is barely noticeable. Carbs to big? After consulting with numerous experts the consensus was 40 or 44 did not matter if the vents were sized correctly. Running 28s for more low end performance. Might try 32s but I just don't think that is the issue. Did I miss anyone? |
r_towle |
Oct 30 2013, 03:29 PM
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#12
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Custom Member Group: Members Posts: 24,591 Joined: 9-January 03 From: Taxachusetts Member No.: 124 Region Association: North East States |
I cant believe 60 idle jets on 44mm carbs would not run far to rich in the idle circuit.
The throttle plates are still 44mm regardless of the venture sizes. It is a big carb for that motor. Camshaft might make it work, but it would need plenty of overlap to speed up the A/F charge enough. What happens when you run smaller idle jets? Its an air velocity issue you have to sort out. Smaller carbs, or more aggressive camshaft with headers and heads to match. Smaller carbs will make you smile. |
Mblizzard |
Oct 30 2013, 03:36 PM
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#13
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Advanced Member Group: Members Posts: 3,033 Joined: 28-January 13 From: Knoxville Tn Member No.: 15,438 Region Association: South East States |
I cant believe 60 idle jets on 44mm carbs would not run far to rich in the idle circuit. The throttle plates are still 44mm regardless of the venture sizes. It is a big carb for that motor. Camshaft might make it work, but it would need plenty of overlap to speed up the A/F charge enough. What happens when you run smaller idle jets? Its an air velocity issue you have to sort out. Smaller carbs, or more aggressive camshaft with headers and heads to match. Smaller carbs will make you smile. While I understand the thought on the butterfly valves, the information I got was that the valves could be 144 but the vent still determined the flow. A 28 vent in a 44 performs exactly the same as a 28 in a 40. Right or wrong that was the opinion of more than one person. I have seen 44s on smaller engines. Going smaller on the jets to 45 makes it run so poorly that it is clear it is running very lean. |
Jetsetsurfshop |
Oct 30 2013, 05:11 PM
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#14
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Senior Member Group: Members Posts: 814 Joined: 7-April 11 From: Marco Island Florida Member No.: 12,907 Region Association: South East States |
Did you check the linkage. Working on my car today and had similar problems. The passenger carb was opening before the drivers. Basically running on 2 cylinders.
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r_towle |
Oct 30 2013, 05:14 PM
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#15
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Custom Member Group: Members Posts: 24,591 Joined: 9-January 03 From: Taxachusetts Member No.: 124 Region Association: North East States |
Stock FI camshaft, jets to large, and throttle plates too large with a very slow port speed are clear factual evidence that the opinions you have listened to May not always be right.
40mm is good up to about 2.4 liter, but then you need custom vents to keep up. How do you know it's running lean? Do you have an Air fuel gauge? Running 50 idles is pretty typical on a 40 mm carb. With the larger amount of air moving by the jet, you cannot help but suck in more fuel than a properly tuned 40mm carb, though at a lower speed. It may be reality that in order to try and compensate for the larger throttle plates, and lower port speed, you may need more fuel to make up for it, but I have a really hard time believing that.... But what do I know. |
r_towle |
Oct 30 2013, 05:25 PM
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#16
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Custom Member Group: Members Posts: 24,591 Joined: 9-January 03 From: Taxachusetts Member No.: 124 Region Association: North East States |
Did you port match the bottom of the carb to the manifolds?
carbs are all about port velocity, open times (duration) of the camshaft, and the overall sucking power of the engine...it's all a Venturi affect. You might be able to get it right, or you may need to live with the bogging low speed of the 44 mm carbs on a stock camshaft motor... Really the issue is the camshaft is really a low duration with little overlap, so the air speed is slowwwwwwww This works fine with EFI when you can regulate the fuel with an on off switch, but when you regulate the fuel based upon port speed and air flow, you need smaller carbs...or a better air pump....or both. |
Bills914-4 |
Oct 30 2013, 05:41 PM
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#17
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Member Group: Members Posts: 310 Joined: 1-March 08 From: suburbs of Miami FL. Member No.: 8,762 Region Association: South East States |
I'm guessing you balanced the carbs with a uni-sync of some type and that you adjusted the linkage so that they pull the same on each carb ,
when my carbs are out sync (one side getting more fuel there than the other side) it stumbles and hesatates in the low RPM range & low rpm takeoff , Bill D. you might want to invest in a weber book , I learned a lot form my dellorto book : ) |
914_teener |
Oct 30 2013, 05:43 PM
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#18
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914 Guru Group: Members Posts: 5,205 Joined: 31-August 08 From: So. Cal Member No.: 9,489 Region Association: Southern California |
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Cap'n Krusty |
Oct 30 2013, 05:56 PM
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#19
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Cap'n Krusty Group: Members Posts: 10,794 Joined: 24-June 04 From: Santa Maria, CA Member No.: 2,246 Region Association: Central California |
Cap'n, he said he'd tried timing between 28 and 32, so I'm assuming with a light at full advance. Mike, were you getting timing movement with a light when you varied RPM's? And for curiosity do you know what the timing was at idle? OK, I missed that, too. I'm a bit off today, sitting down a couple of minutes at a time between moving truckloads of stuff between storage sites for 3 people. Full advance with or without vacuum? The thing I'm getting to is whether there's enough initial advance when the throttle is cracked. Many systems accomplish this with a vacuum retard unit. As in, BAM, you have 10-12 degrees right now. The Cap'n |
Mblizzard |
Oct 30 2013, 06:26 PM
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#20
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Advanced Member Group: Members Posts: 3,033 Joined: 28-January 13 From: Knoxville Tn Member No.: 15,438 Region Association: South East States |
Cap'n, he said he'd tried timing between 28 and 32, so I'm assuming with a light at full advance. Mike, were you getting timing movement with a light when you varied RPM's? And for curiosity do you know what the timing was at idle? OK, I missed that, too. I'm a bit off today, sitting down a couple of minutes at a time between moving truckloads of stuff between storage sites for 3 people. Full advance with or without vacuum? The thing I'm getting to is whether there's enough initial advance when the throttle is cracked. Many systems accomplish this with a vacuum retard unit. As in, BAM, you have 10-12 degrees right now. The Cap'n Without vacuum. I am going to run through everything again and check to be sure I have not missed anything and let you know. |
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