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Unread 03-23-2012, 04:07 PM   #271
uptillnow
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Quote:
Originally Posted by Matt1981CJ7 View Post
Keith,

Thank you. I knew you'd know the answer to that one.

I started a new thread about the e-port, or lack thereof, on the 38. Mcmud responded with a very simple change to my existing layout. See below. Unless anyone sees a problem with this, I'll roll with it.

Matt
I would say Mcmud knows what he is talking about...
Your EGR and airfilter heated air vacuum source will apply when the temperature controlled vacuum valve opens (CTO) with some temperature right off idle..
This will work.
UPTILLNOW

Matt,
I was re-reading your post and noticed you turned the idle speed screw in another 1/2 turn. Can I assume you have it turned in 1 full turn?
I would recommend a vacuum gauge on the "S" port, turn the idle down slightly more than when you have ZERO vacuum, or ZERO needle movement on the vacuum gauge. This will be the most you can open the throttle plate. Then re-adjust your timing and then hook-up your manifold vacuum hose. This "should" recover some of your idle speed that you attained by turning in the idle speed screw more than the 1/2 turn maximum.

The problem is when the speed screw on a WEBER has the throttle plate exposing the enrichening holes #1 you get way way too much fuel at idle, and #2 when you shut off the engine, the throttle plate does not come down and cover up those holes, therefore nothing stops the siphon until the float bowl empties.
Also, I think we can fix that flat spot once we get you on the idle circuit.
Friendly point to consider.
UPTILLNOW

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Unread 03-24-2012, 08:31 AM   #272
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Don't mean to jump in but I recently installed Weber 32/36 DGEV on a 258. After installation I replaced the ICM and the spark plugs. Performed the nutter bypass and set the timing to 8 degrees BTDC. Followed redlines's tuning guideline along with a vacuum gauge. Engine starts easily, once warm it idles smoothly, revs easily to 4000. While driving it sputters and almost dies until I let off the accelerator. Could this be a float level problem? Any and all ideas are welcome.
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Unread 03-25-2012, 08:38 AM   #273
Matt1981CJ7
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Quote:
Originally Posted by uptillnow View Post
I would say Mcmud knows what he is talking about...
Your EGR and airfilter heated air vacuum source will apply when the temperature controlled vacuum valve opens (CTO) with some temperature right off idle..
This will work.
UPTILLNOW

Matt,
I was re-reading your post and noticed you turned the idle speed screw in another 1/2 turn. Can I assume you have it turned in 1 full turn?
I would recommend a vacuum gauge on the "S" port, turn the idle down slightly more than when you have ZERO vacuum, or ZERO needle movement on the vacuum gauge. This will be the most you can open the throttle plate. Then re-adjust your timing and then hook-up your manifold vacuum hose. This "should" recover some of your idle speed that you attained by turning in the idle speed screw more than the 1/2 turn maximum.

The problem is when the speed screw on a WEBER has the throttle plate exposing the enrichening holes #1 you get way way too much fuel at idle, and #2 when you shut off the engine, the throttle plate does not come down and cover up those holes, therefore nothing stops the siphon until the float bowl empties.
Also, I think we can fix that flat spot once we get you on the idle circuit.
Friendly point to consider.
UPTILLNOW
Uptillnow,

Sorry for my delayed response, a buddy and I skipped out for an early season fishing trip, over the last few days.

Today, I plan to make the necessary changes to my vacuum layout, double check for any leaks, and then do the vacuum test/adjustment you've described.

I also need to check the choke, since it didn't seem to operate on the first fire up, but hopefully that was just an anomaly.

I'll post an update, later. Thanks, again.

Matt
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Unread 03-25-2012, 12:44 PM   #274
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Ok, I made the necessary plumbing changes, then reset the idle screw to 1/2 turn in, and the mixture screws to 1-3/4 out.

For whatever reason the engine responded differently to these base settings this time. Perhaps I didn't have it warmed up enough the first go around.

This time, it fired up running a little rough at 800 RPM. As it warmed up, it began running smoother, but the RPM never climbed any higher than about 860. I'll worry about the choke operation, when I get the idle circuit figured out.

Once the engine was warm, I kicked the choke off, and it settled into a reasonably smooth idle at 630. Turning the mix screws in 1/4 turn resulted in a 30 more RPM and a smoother idle. Turning them in any further caused the RPMs to fall. So, now the mix screws were at 1-1/2 turns out, and the idle screw was still at 1/2 turn in. This became my baseline settings for Shawn's idle circuit text described on post #198.

I cranked the idle screw up to 1400 RPM. When I turned the mix screws further in, it made no difference until I was a full turn in, then the RPMs started dropping. When I turned the mix screws 1/4 turn out from baseline, it caused the engine RPM to increase about 20. Further out caused a drop in RPM.

Are the results of this test enough to necessitate a jet change?

Thanks,

Matt
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Unread 03-25-2012, 01:18 PM   #275
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Quote:
Originally Posted by Matt1981CJ7 View Post
...This became my baseline settings for Shawn's idle circuit text described on post #198.

I cranked the idle screw up to 1400 RPM. When I turned the mix screws further in, it made no difference until I was a full turn in, then the RPMs started dropping. When I turned the mix screws 1/4 turn out from baseline, it caused the engine RPM to increase about 20. Further out caused a drop in RPM.

Are the results of this test enough to necessitate a jet change?

Thanks,

Matt
Nice work bud. I was hoping we didn't have to go into "forbidden" territory to correct it

Being that you could go a full turn in on the mixture screws before it hung its tongue out, I'd say your idle jets are in good shape and they did a good job sizing them. If it stumbled as soon as you turned the screws in even a quarter turn, you'd probably need larger idle jets.

How's the deep-throttle stumble?


Shawn
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Unread 03-25-2012, 01:43 PM   #276
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Shawn,

Great. I'm glad the idle jets appear correct.

I'm really noticing a considerable improvement to the low and medium end of the power curve with the 38, over the 32/36.

It still has the "deep-throttle stumble". Actually is more of a lag or hesitation, than a stumble. If I'm easy on the skinny pedal, it accelerates smoothly. But, if I'm cruising at say 55 in 4th, and stomp on it, it doesn't respond immediately, instead it hesitates for a second, then gradually picks up speed.

Matt
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Unread 03-25-2012, 01:51 PM   #277
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Hi Matt, glad to see you've got it worked out. I know you're running a 38 but had a 32/26 previously. You're at 6700 and I'm at 8800 in Conifer, commuting to 5400 daily and putting my 32/36 on in May. Any idea what idle, main and air control jets you had in the 32/36? Thanks in advance!
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Unread 03-25-2012, 02:02 PM   #278
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Unfocused,

Hey neighbor.

To be honest I never checked the jetting on the 32/36. I can tell it was the standard Redline K551 32/36 kit, and it was pretty much plug and play.

But, now that I've experienced the 38, I believe the 32/36 is a little undersized for the 258.

If you haven't made your purchase, I'd highly recommend the 38, instead. If you're dead set on the 32/36, I may have a 6-month old one for sale.

Matt
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Unread 03-25-2012, 02:19 PM   #279
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Thanks Matt, I've already got the carb with factory jets. Nice to know they weren't too far off for 6700. Maybe I'll get lucky and one size change all around will do the trick, or at least get close.

Currently running the BBD and really have no problems with it. Getting about 20mpg RT on the cummute from Conifer to Greenwood Village, and able to mostly hold 65mph in 5th on the uphill run on 285, 31's and 411 gears, MSD 6A. Measured mileage tests in the summer RT from Conifer to Fairplay gets about 24mpg, about half at 10000 so really no complaints at all.

The Weber is an experiment this summer to see what's up Oh, here's a link for torque and HP curves - can't tell which is 32/36 or 38 but maybe it'll be helpful. You can click on the charts and they'll expand, and of course the view expansion in the lower right status bar will give you more.

Thanks again, Mike

http://www.clutchkitcenter.com/media...weber/Jeep.gif
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Unread 03-25-2012, 04:01 PM   #280
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Mike,

Dang, dude, if mine would run 65 up 285, and get that kind of mileage, I wouldn't change a thing!!

I think your 5-speeds, and 4:11 gears, are probably the reason you'd leave me in the dust up that hill. My lowly 2:73 gears and 4-speed doesn't have that kind of getty-up.

Don't get me wrong, I think the Weber is an upgrade over the BBD, especially the 38. But in your case, I wouldn't touch it until you need to.

Matt
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Unread 03-25-2012, 05:19 PM   #281
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I've been doing a little research, and PMing with other members, about this "altitude jetting" thing.

There seems to be two schools of thought on this. One says to leave the mains at the standard 1.45mm size, and simply increase the air correctors until you find a sweet spot.

The other theory is to reduce the mains for the major changes ( 1 size down for every 3000 above sea level ), and then fine tune with whatever air jets are necessary.

So, lets get into this. What's your theory?

Matt
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Unread 03-25-2012, 06:17 PM   #282
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That's what I'm planning for Matt. I've learned a great deal from this thread, particularly from those guru's (you know who you are, Thank You!) who've technical knowledge of the carb, and those with hands-on experience as well. So, from what I know now without actually having mounted the 32/36 here's the plan (all mechanical settings to factory spec):

As to the idle circuit, it seems the fuel mix screw is primary (mechanical in nature), to be in the 1.75 to 2.5 out turn range with attention to position relative to the enrichment port. I'll tune that with a vac gauge for best lean idle at 8800 and see where it ends up, swap the idle circuit jet as needed. That should take care of everything through 2K rpm's or so I think.

The main circuit is a little more difficult. Please understand I'm most interested in economy without sacrificing a lot of performance. For the mains, I'll wire a multimeter in series with the O2 sensor which I can watch while driving. The O2 sensor is a single wire unit so wiring the meter in series is simple. Luckily on the uphill run I'll be on the mains, as you know, so the meter will tell me what's happening: .1v is lean, .9v is rich, .5v +- .05 is just right. If I have to adjust I'll get one size smaller main jet and one size larger air controller and play with one, then the other, then both. I'll reset vac best lean idle with any change.

That and reading the plugs should dial it in pretty close, I hope. I don't much care about the downhill run as I'll be on the idle circuit anyway, if not full throttle-off. But the O2 meter will still be talking to me all the way for both idle and main circuits I'll hook up the meter with the BBD before the swap to get a baseline for comparison; other than swapping the carbs nothing else needs to be changed.

All carbs are designed for sea level in terms of the difference between atmospheric and vacuum pressures and up here it's a little weird, as you know. Instead of 22*HG I've got 15*HG so the air/fuel flow is different. I'm fully emissions compliant with the pulse air system, etc., and I really think that the stepper motor is providing benefit to mpg - and THAT is what this experiment is all about! It hasn't been nuttered because the MSD over-rides the MCU as far as ignition goes. The MCU isn't even plugged into the dizzy yet the Pulse Air and Solvac function normally.

I'm just going to let the carb tell me what it wants via the O2 sensor. The reason I asked you about the jets was to get a starting point, but it isn't critical. This will be a nice hobby for the summer! If you want to knock heads this summer PM me and we'll set it up.
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Unread 03-25-2012, 07:12 PM   #283
Matt1981CJ7
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Quote:
Originally Posted by UnFocused View Post
That's what I'm planning for Matt. I've learned a great deal from this thread, particularly from those guru's (you know who you are, Thank You!) who've technical knowledge of the carb, and those with hands-on experience as well. So, from what I know now without actually having mounted the 32/36 here's the plan (all mechanical settings to factory spec):

As to the idle circuit, it seems the fuel mix screw is primary (mechanical in nature), to be in the 1.75 to 2.5 out turn range with attention to position relative to the enrichment port. I'll tune that with a vac gauge for best lean idle at 8800 and see where it ends up, swap the idle circuit jet as needed. That should take care of everything through 2K rpm's or so I think.

The main circuit is a little more difficult. Please understand I'm most interested in economy without sacrificing a lot of performance. For the mains, I'll wire a multimeter in series with the O2 sensor which I can watch while driving. The O2 sensor is a single wire unit so wiring the meter in series is simple. Luckily on the uphill run I'll be on the mains, as you know, so the meter will tell me what's happening: .1v is lean, .9v is rich, .5v +- .05 is just right. If I have to adjust I'll get one size smaller main jet and one size larger air controller and play with one, then the other, then both. I'll reset vac best lean idle with any change.

That and reading the plugs should dial it in pretty close, I hope. I don't much care about the downhill run as I'll be on the idle circuit anyway, if not full throttle-off. But the O2 meter will still be talking to me all the way for both idle and main circuits I'll hook up the meter with the BBD before the swap to get a baseline for comparison; other than swapping the carbs nothing else needs to be changed.

All carbs are designed for sea level in terms of the difference between atmospheric and vacuum pressures and up here it's a little weird, as you know. Instead of 22*HG I've got 15*HG so the air/fuel flow is different. I'm fully emissions compliant with the pulse air system, etc., and I really think that the stepper motor is providing benefit to mpg - and THAT is what this experiment is all about! It hasn't been nuttered because the MSD over-rides the MCU as far as ignition goes. The MCU isn't even plugged into the dizzy yet the Pulse Air and Solvac function normally.

I'm just going to let the carb tell me what it wants via the O2 sensor. The reason I asked you about the jets was to get a starting point, but it isn't critical. This will be a nice hobby for the summer! If you want to knock heads this summer PM me and we'll set it up.
I'm in. Just name the time and spot.

Interestingly, my '81 came with the Solvac and Pulse Air, but no MCU, and a non-stepper BBD, so a Nutter wasn't necessary. I have no emissions out here in Elbert County, so I removed the Solvac and Pulse Air, mostly to un-clutter the engine.

I look forward to what you find in your experiment. Altitude jetting/tuning appears to be a rather "black art".

Matt
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Unread 03-26-2012, 09:23 AM   #284
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Unfocused,

After re-reading your post, I noticed your comment about only getting 15*HG at your altitude, instead of the 20-plus readings most guys report. I, too, have never gotten a reading much over 16*HG.

I've read that most vacuum gauges are calibrated at sea level, so they inherently read lower at altitude.

Based on that, I've concluded our engines are actually producing the same amount of vacuum as they would at sea level, but the difference is simply in the calibration of the gauge. Assuming that's true, our engines should be pulling the same volume of air, just at a lower density.

I'm not exactly sure where this is headed, but if my theory is correct, it seems our tuning goal should be to maintain the proper ratio of fuel to air density. Since we can't change the density of the air, only the volume, it makes more sense to me to reduce the fuel flow, than to increase the air flow.

Am I thinking this thru correctly?

Matt
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Unread 03-26-2012, 09:53 AM   #285
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Quote:
Originally Posted by Matt1981CJ7 View Post
Unfocused,...
I'm not exactly sure where this is headed, but if my theory is correct, it seems our tuning goal should be to maintain the proper ratio of fuel to air density. Since we can't change the density of the air, only the volume, it makes more sense to me to reduce the fuel flow, than to increase the air flow.

Am I thinking this thru correctly?

Matt
Yes
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