steve260z Posted January 12, 2015 Share Posted January 12, 2015 Here's an interesting short video on AFR on a stroker w/webers: Quote Link to comment Share on other sites More sharing options...
gacksen Posted January 13, 2015 Share Posted January 13, 2015 just wondering about the lean condition they have between 2-4K they say it is the accel . pump. as for some graphs i have seen there is everytime the same lean condition in that rev range on the dyno graphs. why is that ? it does not seem that the cause are the accel pumps. also why are most of the holes on the emulsion tubes everytime in the middle section ? Quote Link to comment Share on other sites More sharing options...
Leon Posted January 13, 2015 Share Posted January 13, 2015 Sorry to say, those guys don't understand how to tune sidedrafts. just wondering about the lean condition they have between 2-4K they say it is the accel . pump. as for some graphs i have seen there is everytime the same lean condition in that rev range on the dyno graphs. why is that ? it does not seem that the cause are the accel pumps. also why are most of the holes on the emulsion tubes everytime in the middle section ? Good observations. The lean spot could be due to the e-tube and not the pumps. Different dynos will have different AFR profiles, especially at the start of the run, depending on the type of dyno and its settings. A load-bearing dyno such as a Dynapack has the ability to hold the car at WOT for a set amount of time before beginning the pull. This gets rid of transients (accel pump shot) and makes the runs much more consistent back-to-back. Ideally, once the main circuit is tuned in this manner, the pumps can then be tuned by performing transient tests.Weber designed all their emulsion tubes for downdrafts. None of them are optimized for the DCOE. Quote Link to comment Share on other sites More sharing options...
steve260z Posted January 31, 2015 Share Posted January 31, 2015 (edited) Still tuning (like what's new...) but I've totally rid the car of the dead spot. Under acceleration the motor would bog down around 2,500 rpms. Using Keith Franck's advice has been awesome. I set the float levels at 25mm from the top of the carb and didn't worry about where the brass floats were in relation to the gasket. On mine the spec level was 8.5mm. Ended up more like 6.5mm. The transition is absolutely smooth. Edited February 12, 2015 by steve260z Quote Link to comment Share on other sites More sharing options...
steve260z Posted March 1, 2016 Share Posted March 1, 2016 Anybody got updates? We've gone a full year not touching the best thread here. I'm out of content since I've had the front suspension apart redoing the springs, struts, ball joints....In addition to oil leaks, misfires, dual mass flywheel, clutch, radiator, expansion tank, coolant routing hose, window tint crap, door lock actuator, HVAC blower motor, valve cover gasket, and thermostats issue with the 2 BMWs in the driveway. Anybody want to buy a E90 335i? Quote Link to comment Share on other sites More sharing options...
zredbaron Posted March 2, 2016 Share Posted March 2, 2016 Weber designed all their emulsion tubes for downdrafts. None of them are optimized for the DCOE. Nice! Well, not nice.... but nice to know! I was never very impressed with changing E tubes. Thought I was missing something. Probably still am. Anybody got updates? We've gone a full year not touching the best thread here. Hard to believe, I remember we used to get 20 emails a week on this thread. I have two updates, well, maybe they're sort of the same update: I will be engine-dynoing my new, rebuilt, new-rebuilt race motor (third time's a charm!) this spring / summer. I will be comparing 40 DCOEs (36mm venturis) to 45 DCOEs (36mm venturis) on the same motor, same day (two Cannon manifolds port-matched respectively). I don't know of such a comparison on the internet or in a book for any application. The comparison isn't fair to the 40 DCOEs, as my head outflows what the carbs can deliver. This is the whole point of the unfair experiment... to compare the dyno plots of a restricted intake (past the Weber flowcharts) to a more appropriate intake (within the charts). Appropriate being relative, of course, because 45 DCOEs are still a top-end compromise for a full race motor, and this is a deliberate compromise to maintain low-RPM torque and throttle response (autocross). This experiment is partly a result of painting myself into a corner in a discussion that came up on my engine thread, and partly out of my own curiosity and enjoyment of our mutual hobby. Weber debate begins here, which ultimately trails off with me citing a Weber chart and then saying I'll let the dyno settle the debate once and for all. My theory is that the draw of the pistons at a given RPM creates a given vacuum signal regardless of intake, drawing metered amounts of fuel set by the carburetor / jet combo. If under-carbureted, inadequate air matches fuel metered for adequate air, producing a rich condition. (The carburetor "feels" more airflow than is actually present.) This cannot be patched at high RPMs with air correctors, because what the engine needs is a more open intake, period. The thread has been pretty silent, not sure if I was too aggressive with my argument? Regardless, should be a fun experiment. We all expect HP and torque to rise... but what about the A/F graphs? What will those look like? And no, I'm not trying to send the debate to this thread. I've already typed too much on the subject as it is! Just completing the circle and replying to Steve. He's right, it's been a long time coming. Quote Link to comment Share on other sites More sharing options...
steve260z Posted March 2, 2016 Share Posted March 2, 2016 Great news. I don't know of any back to back test like that. Very curious about the result. Quote Link to comment Share on other sites More sharing options...
Viva Datsun Posted May 2, 2016 Share Posted May 2, 2016 I'm now working on rebuilding a set of DCOE 40s I bought off a member on here. They were pretty nasty inside and the shop I dropped them off at for cleaning couldn't get the choke/starter circuit/enrichment cam brass tubes out in one piece. They're the little tubes that have a skinny portion in the middle. They don't do anything but activate the starter circuit as far as I can tell. Has anybody simply plugged these? Or maybe someone has a stash of the less common parts laying around they could sell? Any help rebuilding a set of DCOE 18s that were pretty far gone would be helpfull. Most of the info I've found on webers has been related to just tuning, not so much rebuilding. Quote Link to comment Share on other sites More sharing options...
steve260z Posted May 3, 2016 Share Posted May 3, 2016 Most if not all folks here don't use the choke circuit. Since it's the cam piece I would make sure the parts that follow are in the off position and won't move on there own. I haven't recently looked at a diagram but I would think you are fine assuming it's in the off position. Pierce manifolds stocks all kind of parts. I would guess $15 bucks each for the broken parts. Quote Link to comment Share on other sites More sharing options...
Viva Datsun Posted May 4, 2016 Share Posted May 4, 2016 What about the throttle shaft bearings? My seals were shot and I'm seeing some kits on Ebay with sealed bearings that ship free from Europe. Has anybody tried these bearings or dealt with these Ebay buys? Quote Link to comment Share on other sites More sharing options...
steve260z Posted May 4, 2016 Share Posted May 4, 2016 I bought used carbs as well. I see you're experiencing the downside of used ones. Quote Link to comment Share on other sites More sharing options...
Viva Datsun Posted May 4, 2016 Share Posted May 4, 2016 You would probably be correct. I just got them back from being ultrasonic cleaned and blasted. everything looks a lot better now but of course I'm not free. Quote Link to comment Share on other sites More sharing options...
1 tuff z Posted May 4, 2016 Share Posted May 4, 2016 Just pulled my Fairlady out of winter hibernation. This past winter I mated a 100k mile L28 stock block to an E31 head with mild port & polish work, new valve guides, 280z valves & an Isky 290/490 regrind cam. Triple 45 DCOE 152 [spain] Webers that are pretty new [from Evilc] and a header/exhaust from Sean Dezart in France. I welded in a bung for a wide band O2 sensor but haven't plumbed the gauge yet. specs for my triples 145 Mains 155 air correction 36 chokes F16 emulsion tubes 45 accelerator pump jets 55F8 idle jets 4.50 auxillary venturis Today while checking the above specs [hope I have ID'd correctly] I checked the idle mixture adjustment screws. From L>R they were; 2.5, 2.25, 2.75, 2.75, 2.25, 2.25 turns out. I only have a few miles on it but looking at the header coloring i have more blue in the middle cylinders than outboard. Think that's lean? When idling it sounds like it slightly missing [new plugs], pops when cruising along and pops under deceleration. It really pulls nicely and sounds awesome under mid to full throttle, once it climbs above 3k rpm's. My timing light is broken so I'm unable to check that and until I finish the wide band info is lacking. Currently it prefers rapid but not stomp on it throttle input and if I provide too little input begins to die. Ahh, the fun of sorting it all! Quote Link to comment Share on other sites More sharing options...
steve260z Posted May 5, 2016 Share Posted May 5, 2016 You've just taught me something more vague than reading spark plugs..... Quote Link to comment Share on other sites More sharing options...
steve260z Posted May 5, 2016 Share Posted May 5, 2016 Oh, and I woundn't run that new motor very hard or under load not knowing the timing and AFR. Quote Link to comment Share on other sites More sharing options...
Leon Posted May 5, 2016 Share Posted May 5, 2016 (edited) David, sounds like you got your work cut-out for yourself! You've just taught me something more vague than reading spark plugs..... LOL, agreed! Edited May 5, 2016 by Leon Quote Link to comment Share on other sites More sharing options...
Viva Datsun Posted June 23, 2016 Share Posted June 23, 2016 Alright I've got my carbs almost all together now. Sealed throttle shaft bearings feel great and the ebay guy put together a kit of six for those of us running triples. Found some banjo barb fittings from a diesel parts place on ebay too. Way cheaper than the redline fuel fittings. Now I'm still missing a few key pieces before I can really call these things rebuilt. The accelerator pump springs were totally shot when I pulled them apart, so that's a must, three of the big flat washers on the ends of the throttle shafts, one of the roll pins to secure the accel pump cam to the throttle shaft and four of the little balls that go under the brass weights. I think those are part of the pump circuit, not the starter circuit, right? If anyone can help me piece together these stupid little parts that would be awesome. I know I can get them from someone like Pierce Manifolds, but I'm trying to do this on the budget of a carpenter paying his way through school, so any help would be much appreciated as I'd love to have these done by the time I can drop in my new L28! Quote Link to comment Share on other sites More sharing options...
Dat73z Posted July 5, 2016 Share Posted July 5, 2016 Hi all, Figured I'd get some thoughts before I go to town on this. Have a set of DCOE 40 151's I rebuilt myself. To get a nice idle I need to crank down the idle screws which exposes the first set of progression holes and idle AFR's are 10 flat. 900-1000 RPM idle with 50F9 idle jets with the idle mixture screws 2.5 turns out. Timing set at 34-35 BTDC at 3500 RPM. Gets lean (~15 AFR's) at the transition between the idle circuit and mains and pops on occasion. I'm thinking this is because the first progression hole is uncovered on all 3 carbs and bleeding out that system. Mains/air correctors seem fine and I'm at 12-13AFR's on the mains so also a bit rich so maybe I can go a size up on the air correctors? Car drives decently but exhaust tip is covered in black soot from running rich at idle I presume. I've tried covering the progression holes to where a light tip in of the throttle allows the butterflies to expose the first progression hole and turning out the air bleed screws to where the engine will idle. The problem is I need to turn the air bleed screws all the way out and the some of the carbs begin to drip fuel from the trumpets (4PSI fuel pressure). Also, I hear an audible air leak on one of the carb barrels at this setting so it seems like the setting is too far out. I've been thinking of drilling a small hole in each of the butterfly plates (1/32" starting to 1/16" from what I've read online) to let air bypass the butterflies and not have to crank the air bypass screws all the way out to keep the first progression holes covered. Thoughts on this and am I approaching this the wrong way? Thanks! Quote Link to comment Share on other sites More sharing options...
steve260z Posted August 13, 2016 Share Posted August 13, 2016 When syncing the carbs how close is "close enough"? With the SK sail gauge I can get the following in kg/hr: Throttle/flow: 1-7 2-5.5 3-6 4-5.5 5-5 6-5.5 I'm just concerned about throttle #1. I may have a slightly bent butterfly or rod on carb #1. Reason for concern? Quote Link to comment Share on other sites More sharing options...
zredbaron Posted August 13, 2016 Share Posted August 13, 2016 (edited) By "reason for concern?" are you stating this is a concern and asking why? Or are you asking if this is something to be concerned about? Either way... mathematically/theoretically it would distribute the load and volumetric efficiency more evenly if you are able to reduce the throw of the carb linkage to adjust the variation as follows: 1 - 7.0 to 6.0 (5.25 + .75) 2 - 5.5 to 4.5 (5.25 - .75) 3 - 6.0 to 5.5 (5.25 + .25) 4 - 5.5 to 5.0 (5.25 - .25) 5 - 5.0 to 5.0 (5.25 - .25) 6 - 5.5 to 5.5 (5.25 + .25) I understand this is difficult to achieve, but I always shoot for the moon when tuning. Actually, I just always shoot for the moon... Edited August 13, 2016 by zredbaron Quote Link to comment Share on other sites More sharing options...
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