Guest jake Posted August 22, 2004 Share Posted August 22, 2004 Here are the specs from the Triples I bought from Motorsport. The Only thing I changed was the emulsion tubes from F11 to F16. DCOE 40 Choke (primary venturi) 30mm Aux. Venturi 4.5mm Main Jet 130 Air Corrector Jet 170mm Emulsion Tube F16 Idle Jet 45F9 Needle Valve 1.75mm (float control) pump jet 40mm Pump Exhaust Valve 50mm (accelerator pump bleed-back valve) Starter Jet 85F9 I get that flat spot or bog in low RPM as well I checked the throttle plates and they are covering the holes. Funny I still get that 'cone' shape as if the plates are not closing correctly. The idle screws are all the way out so they aren't causing the problem. As far as I now I should change the Main choke and Venturi to something smaller? Quote Link to comment Share on other sites More sharing options...
Guest NapaBill Posted August 23, 2004 Share Posted August 23, 2004 Jake, You mention the "idle screws are all the way out." They should be between one half and one and one-half turns out. It sounds like your idle circuit is a bit lean. If you were able to get a good idle with the screws set properly, you should go to a smaller air correction on the idle jets, say to a 45F6. If the whole circuit is lean, try increasing the jet diameter also, say to a 50 or 55F6. The cone from fuel washdown is always going to be there....it's just that the black area around the cone is darker and larger when the plates are open too much. Bill Quote Link to comment Share on other sites More sharing options...
Guest jake Posted August 26, 2004 Share Posted August 26, 2004 Thanks for the response. But I guess I didn't write that correctly. I meant the throttle plate adjustment screws are all the way out. The mixture (idle) screw is at the correct setting (1.5 turns). Still it drives me nuts I can't figure why the carbs 'bog' anywhere under 3000rpm. I always need to throttle up above 3000 around town to get good response. Quote Link to comment Share on other sites More sharing options...
srgunz Posted August 27, 2004 Share Posted August 27, 2004 Jake I have mikunis but the theory is the same. It sounds like your idle (low speed) jets are too lean. I had the same problem. To get rid of it I ended up with 62.5 idle jets. It is now instant response when I hit the throttle. The weber book I have recommends 55F2 idel jets for a stock L24 or L26. So depending on your motor you may even go bigger than 55. Quote Link to comment Share on other sites More sharing options...
Guest jake Posted August 27, 2004 Share Posted August 27, 2004 OK, So 55F6 or 55F2? which would suit my purpose? the info below shows the F6 is rich (for airflow) while the F2 is towards the leaner air flow side. It looks like they recomend the F9 as a staring point. The 55 seems to be the correct number though. here is the info I found on: http://members.aol.com/dvandrews/webers.htm Idle Jet selection Idle jets cause a lot of confusion; although their name suggests that they govern the idle mixture, this is incorrect. It is true that the fuel consumed at idle is drawn through the idle jet, but the idle mixture is metered not by these jets, but by the idle volume screws mounted on top of each barrel. The idle jets control the critical off-idle progression between closed throttle and the main jet circuit, it is this part throttle operation which is so important to smooth progression between closed throttle and acceleration and for part throttle driving. If this circuit is too weak then the engine will stutter or nosedive when opening the throttle, too rich and the engine will hunt and surge especially when hot. The technique for establishing the correct idle jet size is detailed later, but as a starting point 40/45f9 idle jets for a 1600 engine 45/50 f9 for an 1800 and 50/55f9 for a 2000 will get you out of jail free. Below is a chart showing approximate idle jet sizes for given engine sizes, this assumes one carb barrel per inlet port E.G. two DCOEs. Engine size Idle jet size 1600cc 40/45 1800cc 45/50 2000cc 50/55 2100cc 55/60 Establishing the correct idle jet for a given engine is not easy but usually an approximation will make the car acceptably driveable. If the progression is weak then the engine will nosedive when moving the accelerator from smaller to larger throttle openings. A certain amount of change (richer/weaker) to progression can be achieved by varying the air jet size on the idle jet; this alters the amount of air that is emulsified with the fuel drawn through the idle jet. If this does not richen the progression sufficiently then the next jet size up, with the same air bleed should be tried. Below is a small chart showing the most commonly used air size designations, running from weak to rich. Generally speaking start your selection with an F9 air bleed. Weaker Normal Rich F3 , F1 , F7 , F5 ,F2-F4 ,F13 ,F8-F11-F14,F9 , F12 , F6 The ones in normal use are F2,F8,F9 and F6. Quote Link to comment Share on other sites More sharing options...
Guest jake Posted September 8, 2004 Share Posted September 8, 2004 Update here, I installed 60F9 idle jets and wow! what a difference at lower RPMS. Much more drivability around town. I can let the clutch out without touching the gas. (I was sitting in holiday traffic to test it out) The car would always stall with the 45F9 jets. Also much better response when I gun it. The transition from idle to main circuit is very seamless. Best 40 bucks I spent on the engine yet... I am getting more gas fume smells. Don't know if it related but I think it's mostly due to the valve cover breather. Thinking of running a house into the manifold instead of K&N filter. Quote Link to comment Share on other sites More sharing options...
Guest NapaBill Posted September 9, 2004 Share Posted September 9, 2004 Hi, All. I was going through some stuff this past weekend and found some old Weber technical literature. Funny how the memopry works. I posted in here some time ago that idle jet air correction (F#'s) were progressive. As Jake pointed out, that was incorrect. It tends to get slightly complicated because some idle jets only have one air bleed orifice while others have two, but Weber has a breakdown based on the total equivelent air correction size as follows: Air Jet F Code 0.70 F6 0.90 F12 1.00 F9 1.20 F8-F11-F14 1.30 F13 1.40 F2-F4 1.60 F5 1.70 F7 2.00 F1 2.30 F3 The reason why there can be more than one idle jet with the same air correction size but a different F# (F8, F11 and F14 for example, all of which have a single 1.20 air bleed) has to do with the internal diameter of the jet, which varies from 2.00 for F8 to 1.50 for F11 to 1.70 for F14. A larger internal diameter would have an effect like using a smaller diameter emulsion tube, increasing the volume of emulsified fuel/air available in the well for sudden demand. According to Weber, the more commonly used are F7, F5, F2, F4, F13, F8, F11 and F14. Also, I found some charts and graphs for main choke and main jet selection and for emulsion tube characteristics, along with illustrations of correct and incorrect throttle plate settings. I will attempt to post these in the photo album. Cheers! [/img] Quote Link to comment Share on other sites More sharing options...
zredbaron Posted September 13, 2004 Share Posted September 13, 2004 NapaBill (or anyone else that can help!): I just got some A/F data from some dyno runs: Also, my power is very bumpy below 3500 rpm. From being too rich in that range, I assume? (BTW i think that strange red peak from my first run was from timing not being in the right place and giving false readings...but what do I know?) I am going to get the biggest chokes I can fit in my 40DCOEs, and I am thinking the following changes might be in the right direction: 34-->36mm chokes 130-->145 main jets 180-->195 air corrector jets F11-->F2 emulsion tube 65.F8 idle jet? * 40 accell. pump jet ** * idle jet will have to experimented with all of these other changes. ** this is what's in the car. I was advised that since I go super rich once I hit the throttle and then lean out as the engine builds rpm I should go smaller. Thoughts? I know I'm not supposed to change too much at once, but a lot of these were calculated, and I was *hoping* with that A/F graph you might have a feel for these adjustments....and possibly verify or adjust some of these numbers...of course, if I do get all these jets, I plan on experimenting with different combinations of what I've got to see what makes her happiest... Thanks! Quote Link to comment Share on other sites More sharing options...
Guest NapaBill Posted September 13, 2004 Share Posted September 13, 2004 Mark, I need to know about the methodology used by the dyno man. Did he increase rpm gradually against a constant load, or did he floor the throttle and vary the load to change the rpm? The chart begins at 2000 rpm. It would help to know what the mixture was like between there and idle. What is your idle rpm? Just speaking idly (harhar) I think a .55 idle jet is about right. Since the graph cuts off at 2000 rpm it is hard to judge the idle, since that leaness at 2000 might be the idle or it might be the beginning of transition. If it actually goes leaner at idle, try a .60, but also go leaner on the air correction, say F13 or F2 whether you change the fuel orifice or not. The transition is way too rich. You want a fual/air ratio around 13-14:1. From 2800-3500 your motor bottoms out at 10:1. It climbs back to 13:1 at around 4800 and drops under again at 6700. So you need to lean the idle(?), the transition and the beginning of the main circuit, keep the middle of the main circuit the same and lean the top end. Good trick. According to Weber, at 517cc per cylinder with peak horsepower at 6000 rpm you should be running 38mm chokes. Since 36 is the largest available for 40DCOE’s, change to 36’s, unless your rejetting budget encompasses buying three 45DCOE’s! Also according to Weber, with 36mm chokes your main jet size should be somewhere between 1.35 and 1.60. While you have the opposite of a lean condition anywhere in the main circuit, I think enlarging the chokes will call for larger main jets, either 1.45 or 1.50. Your top end is rich, which indicates a larger air corrector jet is needed. I would try 2.00 and also experiment with some 2.15’s. (I always change air corrector jets in steps of .15mm.) Peak power from 5000-6500 looks pretty good. It would be nice to lean it out from 3000-5000. The larger chokes should help that, since they will decrease the vacuum on the auxilliaries. What size Auxilliary Venturis are you running? If they are 3.5 you can delay the entry of the main circuit by changing to 4.5’s. Don’t change the emulsion tubes. F2’s are definitely not indicated for this engine, unless you are running alcohol! F2’s have a smaller outside diameter (7.5mm versus 8 for F11 and 8.2 for F16) to allow more fuel/air mix to be held in the emulsion tube well for sudden accelerations. Also, F2’s have four less 1.00mm holes in the middle of the tube than F11’s. F2’s will worsen your low rpm richness. The F11’s are good all around emulsion tubes and should work fine for your application. Don’t change the pump jets. (Waste of money.) Remove the top covers of the carburetors and unscrew the little brass widgets in the bottom of the float bowl. This is the Accelerator Pump Drain Jet (also called Inlet Valve with Exhaust Orifice). These little buggers have more to do with accelerator pump volume and durration than the size of the pump jets. And you only need to buy two of them! If it has a hole in the side, it allows some of the fuel from the pump jet to bleed back into the float bowl instead of being injected into the manifold. If there is no hole it is a closed drain back and will inject all of the pump discharge in a long burst. If there is a hole the size will be stamped on it (closed is .000). The larger the hole, the shorter the duration and the less the volume of fuel delivery. I think you should increase the size of the drain back by 20% or more. That will reduce the volume and duration of the pump stroke without affecting the high speed enrichment function. Hopefully, doing all of this will result in a more consistent mixture, smoother operation, and a higher and wider power band, not to mention better mileage. What are you getting now? And what does the horsepower curve look like? ~Bill Quote Link to comment Share on other sites More sharing options...
ZR8ED Posted September 13, 2004 Share Posted September 13, 2004 Guys guys guys. I had no idea there were so many people on this site with webers that needed help. I've been off the weber scene for 3 years now (gone turbo), but I am still a "Weber Warrior" at heart! I've only briefly looked over this thread, so I'm in no position to comment yet... I've still got a bunch of pump jets, main and airs kicking around, as well as spare gaskets and such from my rebuilding days. (I don't do rebuilds anymore) Maybe in the future I'll get back into it as a hobby again. I've kept my manuals, and all my testing notes and results as well. I've got a ton of misc mikuni jets as well.. way too many to list, and no sets that I can remember. I have them in a big case that I'd like to get rid of sometime. Anyways, I'll take some time and brush up on this thread. If you got a question just ask folks! Thanks, Scott. Quote Link to comment Share on other sites More sharing options...
zredbaron Posted September 14, 2004 Share Posted September 14, 2004 Bill, The runs started at 2000 rpm because with the cam I have and the jetting as it is, the car doesn't do so well down there. The dyno runs started at 2000rpm with light pedal and transitioned to full pedal by around 2500rpm or so. Full pedal till the end of the run. My idle rpm is about 1000. I had 55.F8 idle jets in the car, and it was too lean (did a nose dive under 3000 rpm). I have 65s in now...perhaps 60 would be best. Here's the power curve: As for gas mileage, I have no idea. I just did a head swap, and haven't driven it enough to tell you. I was getting 18-22 before the swap. Not sure how relevant it is but my head flows 200cfm (lift .520", duration is 290° for intake, and 274.8° for exhaust). Compression: ~11:1. Thanks for the help!!! -Mark P.S. Scott, are you willing to part with any of your jets? I would love to get my hands on a decent collection so I can play with them on a dyno... Quote Link to comment Share on other sites More sharing options...
Nismo280zEd Posted October 20, 2004 Share Posted October 20, 2004 Ok so after a bad attact of the "while i'm at it's" A simple intake manifold gasket change turned into a new header, which turned into a new muffler, into a completely new exhaust. Somehow it also turned into a new alternator, a "winged hood" and welded up headlight buckets. Also a round racing style fuel door and new parking lights. Anyway!.... I'm curious about what kinda power numbers i should be looking for with my triples, I plan to get a dyno run sometime soonish and would like to know how i compare. My setup was mentioned before, N47 ported and polished head. Racing cam from japan, and valve springs. New 6-2-1 "thick flange" header into 2.5" exhaust piping. I should mention the head has been shaved quite a bit and a 1mm head gasket is being used. I'm honestly hoping from something around 200-220 rwhp am i nutz? -Ed Quote Link to comment Share on other sites More sharing options...
Nismo280zEd Posted October 20, 2004 Share Posted October 20, 2004 Clearly i must be nutz Quote Link to comment Share on other sites More sharing options...
Guest Rider_X Posted November 2, 2004 Share Posted November 2, 2004 What are the best webers to go with? Quote Link to comment Share on other sites More sharing options...
SHO-Z Posted November 12, 2004 Share Posted November 12, 2004 I am also new to the triple scene. Went to buy a 5 speed for $75 and came home with a set of triple SK Racing Carbs for an extra $100, not a bad day at all. From all of the searches, most of the information from zcar.com, I have done they are a cross between a Weber and Makuni. Have not had the time to really get into them as yet. From the Weber book that I have, forced induction is possible with this design of Carb. If anyone has information on SK Racing Carbs, I would appreciate information. 8) Quote Link to comment Share on other sites More sharing options...
DeusEx Posted November 22, 2004 Share Posted November 22, 2004 Hey guys, Well its been a while since i posted on here an i am ashamed to say that i found my problem posted earlier in this site. Woudl you believe that i had a small engine fire that cooked one of my air filters and killed my spark plugs. Replaced them, instant smoothness . That was my bad. I was happy with it for a while, but i began to wonder if i should tune my carbs to my new cam. As a result of teh cam the car now revs to 7500 instead of about 5500 so its a big difference up top and i lost my stump pulling torque. I was speaking to a local engine builder who actually has a 240 with triple SUs and he said my car should be pulling from 1200 instead of 3500. He recommended jetting my carbs to suit the cam as well as dialing in the cam. Now i dont have a variable cam gear and i did find TDC so do i still need to get this done? Is it a law of teh jungle to have yoru carbs jetted to suit you cam? Here are the specs as a refresh. Triple 45mm Webers with 32 venturis 200 Air correctors F16 Emulsion 120 Mains CAM Settings Valve Ex: .012 In: .010 Ex Opens: 66 Closes: 26 In Opens: 26 Closes: 66 Lobe Lift: .318/.318 Any suggestions as to what i should do. As always guys your knowledge and help is always appreciated Quote Link to comment Share on other sites More sharing options...
Synlubes Posted December 2, 2004 Share Posted December 2, 2004 NapaBill, I have not seen where / if you have posted up any of the tech info you referenced in your last post. If you need some help putting the stuff up or somewhere to host it, let me know. Quote Link to comment Share on other sites More sharing options...
DeusEx Posted January 4, 2005 Share Posted January 4, 2005 Why isnt this a sticky anymore!? Dont tell me im alone in teh world of metered fuel leakage! Quote Link to comment Share on other sites More sharing options...
Nismo280zEd Posted January 4, 2005 Share Posted January 4, 2005 Hey i was thumbing through some porsche catalogs, when they go back over to webers, they use a 3psi fuel pump and recomend a bosch 009 distributor (going back to mechanical advance and points) thought it was kinda interesting. What psi is everybody running? -Ed Quote Link to comment Share on other sites More sharing options...
DeusEx Posted January 7, 2005 Share Posted January 7, 2005 Hey guys, was trolling round the net to pass some time and happened upon the weber site. After some reading in the setup and jetting area i read that 45mm webers should never run less than a 34mm Venturi (choke) now im running a 32 as are a few ppl i know and weber recommend a 36mm. Is anyone out there running a 36mm venturi in their 45 webers? If so whats the power delivery like, any flat spots. If not im keen to get this done along with planing my P90 to try and get compression into the 10s. Thanks Quote Link to comment Share on other sites More sharing options...
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