Mudge Posted February 4, 2003 Share Posted February 4, 2003 Ok, got the car idling decently again, and able to stab the gas and have it return to idle instead of staying at that RPM and only slowing going back down. Measuring from the pivot rod, to the carbs, I found that each was off by 1/8" or so, so I see that the whole geometry is somehow wacked out to start with. Looks like a single nut in the pivot area on the furthest front carb could be the cause, but I didn't mess with it. What I decided to do, was back out the idle speed screws all the way, and measure as accurately as I could the distance between both, which was about 2 3/4mm. Once I did that and put the idle speed screws back into place (seated to the 2 3/4mm mark) the car started up fine, and idled just fine even at 600 RPM which most of the rest of the time would be impossible. I didn't let it heat up all the way to finish with the idle speed screws, but brought it to 120º or so, so on a later drive tonight I will set the final adjustment there. Hopefully I should pickup some main jets within a week, and be able to report in 10-14 days with, I hope some good news. I was getting very close to giving up and going for some SU carbs, when I read about them they have only 1 freaking needle/jet, sounds easy! Quote Link to comment Share on other sites More sharing options...
Mudge Posted February 24, 2003 Share Posted February 24, 2003 Ok, sorry for the long wait, I finally have some form of an update (took awhile for my jets to come in, and me to put them in). My settings now are 60 primary idle jet, 40 secondary idle jet. I ran this for about 4 days, not long enough to really see if it made much different MPG wise but I'm sure it did, however I dont believe to a great extent. I have now in the car as of tonight, a 110 and 120 for the secondary jets (remove the top of carb to get to these). Previously I had a 145/150 setup which was in the car when I got it. With the timing I'm currently running I might be detecting a tad bit of ping in a couple areas but I'm not sure, so I may back off the timing tomorow to see if WOT is any different. I also have a 130 set of secondaries to put in, which I'm guessing might be good with the 120 for my 2.4L, in terms of lessening my current minute power loss. What is going on now, is that if I'm going towards a hill at 60, it requires a bit more work to maintain that 60 MPH compared to before, if I keep the gas pedal 'level' it seems to lose more umph than previous setup 145/150. I also notice, that giving the car gas past around 2k RPM has a bit of a hesitation effect, so I would think that currently I'm running a bit lean and/or maybe the timing can fix it, but I think I like the timing close to where it is now. I may continue to run this way for the week to see if this is the "ulitmate" MPG setup for DGVs, but again I think the 120/130 might be better for WOT. I had it in 3rd on the freeway up to about 5500 RPM and it felt pretty strong, I made a few WOT trips and it seems pretty good overall, especially past 4k, so if anything was effected most noticeably it seems to be transitioning past 2k RPM or so, this could be because I now have a soft spot or something since you are really supposed to change jets along with air tubes, emulsion tubes and yada yada yada ($$$). Simple cruising or 'normal' throttle input is pretty normal. I spent $44 on this last bach of jets, plus the other $34 or so, I'm almost to the point of having had a set of round top SUs. So for the one or two people stuck with DGVs you may consider just getting a carb setup that everyone knows how to work on/tune. With only one jet you almost can't go wrong it sounds like So, 60/40 idle jets (60 main idle), 110/120 secondaries (I'd suggest 120/130 probably?) I have a stock exaust manifold, N33 intake and N42 head, so its probably pretty close to stock as far as fuel needs go. The exaust is pretty wide open and noisy which makes listening for the engine a little tough at WOT. Hopefully I can make a "final" or near final update by the end of the week in regards to MPG. I have an 82 280ZXT turbo car which will drop in hopefully in the next 2-3 months, so this is about the end of the road for me carb wise. I made my guesses on buying jets based on surface area, which is probably not the best or most accurate way but its about all I could go on, since there seems to be NOTHING out there on the net, or in the books, on choosing DGV jet size, nor does there seem to be ready information as to when the vacuum secondaries kick in, which is also rather sucky. Quote Link to comment Share on other sites More sharing options...
Mudge Posted March 1, 2003 Share Posted March 1, 2003 Looks like about 22MPG, a few WOT trips and a few short drives. Most of my driving is either a 10 min trip, or my 45 minute treck into San Fran for work, so not much freeway stuff, either way not great but much better than the 15 I started out with. Quote Link to comment Share on other sites More sharing options...
scott19 Posted March 17, 2003 Share Posted March 17, 2003 Hey Mudge, just went through 5 pages of your ordeal, I hope I might be of service to you or whoever might be reading this in the future. First some DGV Z car tips: 1.Make sure ignition system is in top shape. 2.Rebuild the carbs. Kits can be had in the $20 range (each) and include the power valve and accelerator pump diaphragms, which frequently go bad. It's very easy to rebuild these carbs if you have at least average mechanical skills. It also gives you the chance to clean the jet orfices and float bowl. 3.Connect the vacuum advance hose from your distributor to the vacuum fitting on one of your carbs, NOT to the intake itself. If you connect it to the intake, the vacuum advance will be wide open all the time. Plug the vacuum fitting on the other carb. 4.Go through your linkage to make sure everything is synched up and not binding. It's not a bad idea to disconnect the linkage when adjusting the idle speed and mixture. 5.Adjust the the idle speed screws as low as possible ( till the engine rpm gets as low as car can take and still idle reliably). 6.Have the idle MIXTURE screws out about 2-3 turns. Start on one carb and turn the screw in at about 1/4 turn increments, until you hear the engine start to stumble. Back the screw out until the engine starts to regain smooth idle. It's been my experience here to use a vacuum gauge connected to the INTAKE, and to back the screw out till the gauge reaches it's maximum reading, then stop. You MIGHT turn the screw in a hair at this point. 7.Repeat step 6 for the other carb. 8.Adjust your idle SPEED screws to your liking ( I prefer about 800 to 850 rpm). Adjustment back or forward on one of the screws may be necessary until you get a good even idle. 9.If you're still experiencing an off idle hesitation/stumble, adjusting your timing up may help. Common Z car practice is to experiment on pushing it up until you're pinging at top gear under load, then retard it back a bit. 10.Jets? In my opinion, the most important one is the primary idle jet. I have a stock 260 with these carbs, and even after all these above adjustments, I still had a bit of stumble. I was running a 50 in the primary idle jet, a 55 in the secondary. I did what you did and switched them, 55 primary idle, 50 secondary. Definite improvement I just did this, so time will tell if I got rid of the stumble for good. I'll post again in a couple of days with the results. Hope this helps someone. Quote Link to comment Share on other sites More sharing options...
Mudge Posted March 17, 2003 Share Posted March 17, 2003 I found out that I for sure have an R200 in the back, and if my tach/speedo are accurate (the speedo is, I have been through several speed traps) I have a 3.90 gear. I run anywhere from 3400-3800 on the freeway in 5th with my .864 overdrive and 195/60 -15" tires. Quote Link to comment Share on other sites More sharing options...
A. G. Olphart Posted March 20, 2003 Share Posted March 20, 2003 As usual, I'm confused: I don't follow the logic of putting smaller jets in dual carbs because they are seeing smaller displacement. With less displacement per carb, the throttle plates will just open less... like they are running on the big engine at a lower RPM. Isn't jet size pretty well tied to the venturi size? (I noticed in the charts of stock Ford DGV's that the ones with small jets also had smaller venturi sizes). Quote Link to comment Share on other sites More sharing options...
Mudge Posted March 21, 2003 Share Posted March 21, 2003 Thats why your not really supposed to change just one thing when you want to change AF on a carb, you change the linearity of how it operates if you just change one thing. Soft spots, etc will occur. If there were no need to put smaller jets in a carb, then people wouldn't sell them. My gas mileage improved 25%+, so in my eyes it worked. Not as well as I hoped, but I didn't want to dump over a hundred bucks into a set of carbs when I could have had SUs. If I had known that I'd end up with 20-22 MPG and spend $70+ then I would have just gotten SUs anyway. Quote Link to comment Share on other sites More sharing options...
Here comes trouble Posted January 19, 2007 Share Posted January 19, 2007 32/36 DGV dual carbs Z Main Jet primary....140 Main Jet secondary...135 Air jet primary ...165 Air Jet Secondary....160 Idle Jet secondary.........50 Idle Jet primary....55 Float needle and seat................2.0 Main venturi (choke tube)....26/27 Primary emulsion tube......F50 Secondary Emulsion tube...... f-6 more info: http://forums.hybridz.org/showthread.php?t=118404 Quote Link to comment Share on other sites More sharing options...
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