Weber Set-Up and Tune Discussion - Page 14 - JeepForum.com
Search  
Sign Up   Today's Posts
User: Pass: Remember?
Advertise Here
Jeep Home Jeep Forum Jeep Classifieds Jeep Registry JeepSpace Jeep Reviews Jeep Gallery Jeep Clubs Jeep Groups Jeep Videos Jeep Events Jeep Articles
Go Back JeepForum.com > Models > Jeep CJ Forum > Weber Set-Up and Tune Discussion

Rear Disc Brake Conversion Kit- TJ,YJ,XJSWAG 50 Cal Ammo Can Mount With M2A1 Can~Artec JK 1 TON SWAP~

Reply
Unread 08-16-2011, 10:57 AM   #196
John Strenk
Moderator
 
John Strenk's Avatar
1976 CJ5 
 
Join Date: Feb 2005
Location: Shalersville Ohio
Posts: 12,966
Quote:
Originally Posted by uptillnow View Post
This is a GREAT find... A big problem, other than poor idle, is when you turn the engine off the throttle plate does not come down and cover that enrichening hole. This exposed hole will continue to siphon until the float bowl is empty or you restart the engine. This siphoning fuel goes into the intake manifold, down the cylinders washing the oil off the walls, and then it just delutes the oil. I believe this is true for any carburetor that has enriching holes or slots for enrichening etc.
This is the reason it is so very "CRITICAL" to keep the throttle plate below the enrichening hole (s).
Good Find, Good Fix, Good Save....
UPTILLNOW
Let's not go overboard on that Many carbs are designed to have the transition holes partially uncovered.



A lot have a air bleed hole that will prevent fuel from siphoning out when the engine is off. Unfortunately, they tend to get plugged with dirt and then you have siphoning problems

Follow factory recommendations.

Carburetor Factory that it.

John Strenk is offline   Reply With Quote
Unread 08-16-2011, 11:05 AM   #197
uptillnow
Member
 
uptillnow's Avatar
 
Join Date: Mar 2009
Location: Placentia, California
Posts: 475
Just my experience after working on Webers for a few years.
Thanks for your concerns pictures and imput.
UPTILLNOW
uptillnow is online now   Reply With Quote
Unread 08-18-2011, 05:16 PM   #198
swatson454
Mall-crawlin' Hot Rodder
 
swatson454's Avatar
1983 CJ7 
 
Join Date: May 2009
Location: Dripping Springs, TX (soon)
Posts: 4,728
I recently ran what I believe is a much more relevant test for determining the best idle jet size and I thought I'd share it.

To give you an idea why, and I'm not trying to undermine Redline's tuning methods at all, it didn't make any sense to me to use some arbitrary mixture screw setting with the engine idling to accurately determine the best idle jet size the engine wants when it's actually running down the road.

The test: After driving the Jeep around so it's good and warm, wheel back in and do your best at finding the lean-best idle as described earlier. Using the speed screw, increase the engine speed to 1,400 rpm. This forces the carb into its progression circuit where the engine spends 90% of its time, not at idle. Now, turn the mixture screw(s) in a half turn and note any change in rpm and/or engine sound. Return the screws to where you started and then turn them out a half turn. Again, noting any change in rpm or engine sound. Take the screws back to their starting position and return to idle.

If the engine responded with a cleaner sound and/or more rpm when the mixture screws were opened, you may benefit from a larger idle jet. If the engine responded with a cleaner sound and/or increased rpm when you turned the mixture screws in, a smaller idle jet may be in order.

To quantify that idea with actual findings, I started with 45 idle jets and 1.85mm idle air bleeds. Don't let the air bleeds throw you off too much; it's basically a leaner 50 idle jet that pulls richer towards the top end of the progression circuit than a 45 would. At 1,400 rpm, turning the mixture screws out a half turn really had no impact. However, turning them in less than a quarter turn resulted in a quick drop in rpm and the engine basically choked. Had I not been maxed out on my idle circuit, I'm positive an increase in fuel from the mixture screws would've made a difference in rpm. This particular test shows that the engine wants more fuel. My wide-band air/fuel monitor showed full lean, over 16:1 before touching the mixture screws.

Next test: Installed 50 idle jets and went through the lean-best idle procedure again. Brought the engine back up to 1,400 rpm and took the mixture screws out a quarter turn. No change in rpm or sound. Mixture screws back to the starting position and then in a quarter turn. No change in rpm but a slightly cleaner sound. Took them in another quarter turn and the rpm started to drop and the engine sounded rougher. This tells us that the engine has enough fuel by it not responding to giving it more with the mixture screw and it also tells us what our window is for going leaner by it dropping rpm at a half turn in on the mixture screw. The air/fuel ratio before touching the mixture screws was 14.2:1. Good! Now we know where the lean spot is and where it no-longer responds to more fuel.

Final test: Installed 60 idle jets and went back through the lean-best idle procedure. Again, 1,400 rpm with the speed screw. Take the mixture screws out a quarter turn, no response in either sound or rpm. Turn them in a quarter turn from the starting point and only a vague improvement in sound, being a little cleaner. Another quarter turn in showed another barely detectable improvement in sound. This tells us that the engine is getting more fuel than it wants by not responding to additional fuel from the mixture screws and barely a slightly better sound from reducing the fuel with the mixture screws. Obviously, the volume of fuel being delivered by the 60 idle jets was so much that a smaller, controlled amount being added to or removed from the total by adjusting the mixture screw had very little to no impact. To visualize the scenario, adjust the little flow gate on a river dam that's already overflowing. The engine sounded sluggish and 'heavy' with these jets. Air/fuel ratio before touching the mixture screws was 11.8:1 Really?

The whole point with this test is that not everyone wants to spend $300+ on a wide band air/fuel monitor and the typical "X amount on the mixture screw at idle is perfect while driving" setting leaves a little to be desired. It does take a good ear and "feel" for what the engine is telling you but it's pretty damn accurate. Hopefully this helps bridge the gap by providing a more accurate means of sizing your idle jets.

Any and all thoughts are greatly appreciated, of course!


Shawn
__________________
Live in a way that those who know you but don't know God will come to know God because they know you.
swatson454 is online now   Reply With Quote
Unread 08-18-2011, 05:51 PM   #199
uptillnow
Member
 
uptillnow's Avatar
 
Join Date: Mar 2009
Location: Placentia, California
Posts: 475
Shawn this is Great!
This includes all of the fuel from the enrichening holes, all higher speed pump nozzle enrichening and any tip in from the main circuit, (if the float is too high, or the main jets too too big).
Thanks for this alternate tuning explanation.
UPTILLNOW
uptillnow is online now   Reply With Quote
Unread 08-18-2011, 08:19 PM   #200
razor2264
Registered User
1979 CJ5 
 
Join Date: Sep 2008
Location: Iwakuni, Japan
Posts: 140
Thanks Shawn! Great info!
razor2264 is offline   Reply With Quote
Unread 08-19-2011, 01:13 AM   #201
Matt1981CJ7
Web Wheeler
 
Matt1981CJ7's Avatar
1981 CJ7 
 
Join Date: May 2011
Location: Elbert, CO
Posts: 9,882
Wow, that was a loooooong read.

I must have got lucky. My 32/36 was pretty much plug and play.

I've experimented some, but my final settings keep coming back to very close to factory settings.

Matt
Matt1981CJ7 is offline   Reply With Quote
Unread 08-19-2011, 06:49 AM   #202
swatson454
Mall-crawlin' Hot Rodder
 
swatson454's Avatar
1983 CJ7 
 
Join Date: May 2009
Location: Dripping Springs, TX (soon)
Posts: 4,728
Thanks guys. It's not perfect but what ever is, lol. One thing I forgot to mention is that once you get the right jet installed and drop the idle back down, the lean-best mixture screw settings fall where ever they fall at idle because you correctly sized the jets for the progression circuit.

Based on this test, I went up a size from 45 to 50s. I'll get some good drive time on them and report back.

Quote:
Originally Posted by Matt1881CJ7 View Post
Wow, that was a loooooong read.
Matt
Indeed, Matt. I think it took longer to write the post than it did to run the test with three different jet sizes. Sorry about that

Anyways, I'd like to gather some thoughts from you guys and go from there.


Shawn
__________________
Live in a way that those who know you but don't know God will come to know God because they know you.
swatson454 is online now   Reply With Quote
Unread 08-20-2011, 04:17 PM   #203
medic-11
Registered User
1990 YJ Wrangler 
 
Join Date: Jun 2010
Location: Lakeland, FL
Posts: 244
Has anyone used a weber 32/36, 34 or 38 on a turbo in a blow through application? Im considering buying a 38 carb kit, but will hopefully be bolting on a turbo soon.
medic-11 is offline   Reply With Quote
Unread 08-21-2011, 08:32 AM   #204
swatson454
Mall-crawlin' Hot Rodder
 
swatson454's Avatar
1983 CJ7 
 
Join Date: May 2009
Location: Dripping Springs, TX (soon)
Posts: 4,728
Quote:
Originally Posted by medic-11 View Post
Has anyone used a weber 32/36, 34 or 38 on a turbo in a blow through application? Im considering buying a 38 carb kit, but will hopefully be bolting on a turbo soon.
I've never boosted a carbed engine but I do have some thoughts. I certainly wouldn't do it on a 32/36, who's progression circuit is already too small. Boost and lean aren't allowed to play in the same sandbox.

You'll most-likely need to "boost reference" the power valve so it works correctly and I don't know how to do it on a Weber. Maybe you can google some good information on "boost referrenced power valves."

Sounds fun though
__________________
Live in a way that those who know you but don't know God will come to know God because they know you.
swatson454 is online now   Reply With Quote
Unread 08-21-2011, 07:16 PM   #205
medic-11
Registered User
1990 YJ Wrangler 
 
Join Date: Jun 2010
Location: Lakeland, FL
Posts: 244
I never thought about searching for specific carb mods. I did google "weber 38 turbo" and a few other ways at wording with little result. I was able to find some info about a Mitsubishi Montero turbo kit that uses a weber 38, but they are selling modded carbs so no details are given. Thanks for the search pointer.

On a side note, I used to have a ATI supercharged/intercooled 1985 Corvette (EFI) and I recently sold my 1993 GMC Typhoon (Turbo/intercooled/ full time AWD- but also EFI), so I am familiar with forced induction tuning on an EFI car. I used to use Moates.net Autoprom for tuning on the fly. I still have a Zeitronix wide band, and I have lots of carb tuning experience from my 1971 Nova with a Holley 750 DP (sold thanks to divorce...)

If and when I turbo the 4.2, I will take pics and post it all on here, probably in the YJ section though....

Thanks, Jim
medic-11 is offline   Reply With Quote
Unread 09-01-2011, 05:38 PM   #206
SJ85CJ7
Registered User
1985 CJ7 
 
Join Date: Jun 2011
Location: Some place between Heaven and Hell, Tennessee
Posts: 75
Just installed a Weber 32/36 used, starts fine but rough idle, spitting in the primary barrel (gas just pours in) and no matter where I turn the idle mixture screw in or out there is no change in idle or rpm's. Had followed the beginning of this thread just can't seem to get this carb to play nice. Checked all my vacuum lines had replaced most of them during the install.
__________________
85' CJ7, 258 I6, "Team Rush" Weber 38/MSD 6A, T-176 4-speed, twin-stick Dana 300, DANA 30 fore - AMC 20 aft with stock 2.73 gears, 31" tires, 8k winch, "Dirtworx" rear bumper/tire carrier. My Daily Drive, JustEmptyEveryPocket
SJ85CJ7 is offline   Reply With Quote
Unread 09-01-2011, 09:40 PM   #207
mcmud
Web Wheeler
1983 CJ8 
 
Join Date: May 2008
Location: N.E. Alabama
Posts: 2,650
When we see the mixture screw having little or no effect to idle quality it is a real good indicator that the throttle plate is opened too far... allowing enrichment fuel to be drawn past the plate.

If we see fuel spilling from the axillary (booster) venturi its a real good indication of a float out of adjustment/bowl overfill and the primary throttle plate being open, drawing fuel from the well.

Remember that during the initial tune procedure that the idle speed screw is to be set to a maximum of 1-1/2 turn in once the tip contacts the stop lever and within that point that no vacuum signal is seen at the 'S' nipple at idle speed.
In order to set this screw you must first maintain the choke plates open while you open/close the throttle plate in order to clear the fast idle linkage from any interference.

If the carb is jetted near to the need of the engine you should then see result with begining at say 3 to 3-1/4 turns out with the mixture screw and work it inward from there. In this thread you will find the process of a lean best setting clearly defined.

If you haven't already done so, check on the float setting.
mcmud is offline   Reply With Quote
Unread 09-01-2011, 10:45 PM   #208
SJ85CJ7
Registered User
1985 CJ7 
 
Join Date: Jun 2011
Location: Some place between Heaven and Hell, Tennessee
Posts: 75
Looks like I'm going to do a rebuild on it, just to make sure that everything is ok inside. Bought it used and should of rebuilt it first PO said it only had 2K miles since last rebuild.
__________________
85' CJ7, 258 I6, "Team Rush" Weber 38/MSD 6A, T-176 4-speed, twin-stick Dana 300, DANA 30 fore - AMC 20 aft with stock 2.73 gears, 31" tires, 8k winch, "Dirtworx" rear bumper/tire carrier. My Daily Drive, JustEmptyEveryPocket
SJ85CJ7 is offline   Reply With Quote
Unread 09-02-2011, 10:57 AM   #209
uptillnow
Member
 
uptillnow's Avatar
 
Join Date: Mar 2009
Location: Placentia, California
Posts: 475
Quote:
Originally Posted by SJ85CJ7 View Post
Looks like I'm going to do a rebuild on it, just to make sure that everything is ok inside. Bought it used and should of rebuilt it first PO said it only had 2K miles since last rebuild.
I see you bought this used. There is ussually nothing wrong with that except the "Weber" 32/36 DGEV for use on a Jeep ussually starts out with the jetting something very close to this:
.75mm Primary idle jet
.60mm secondary Idle jet
1.45mm pri & sec main fuel jets
1.70mm pri air jet
1.60mm sec air jet

Follow mcmud's basic set-up, about 1 1/2 turns in on the idle speed screw with ZERO vacuum at the "S" advance port or ported vacuum, then you can find the lean best idle. This should get you in a place to start diagnosing any problems you might have from this point forward.
There are many people who are very well versed when it comes to tuning a real "Weber".
Good Luck
UPTILLNOW
uptillnow is online now   Reply With Quote
Unread 09-02-2011, 12:03 PM   #210
John Strenk
Moderator
 
John Strenk's Avatar
1976 CJ5 
 
Join Date: Feb 2005
Location: Shalersville Ohio
Posts: 12,966
Quote:
Originally Posted by medic-11 View Post
Has anyone used a weber 32/36, 34 or 38 on a turbo in a blow through application? Im considering buying a 38 carb kit, but will hopefully be bolting on a turbo soon.

Quote:
Originally Posted by swatson454 View Post
I've never boosted a carbed engine but I do have some thoughts. I certainly wouldn't do it on a 32/36, who's progression circuit is already too small. Boost and lean aren't allowed to play in the same sandbox.

You'll most-likely need to "boost reference" the power valve so it works correctly and I don't know how to do it on a Weber. Maybe you can google some good information on "boost referrenced power valves."

Sounds fun though
Interesting, I have a neighbor that builds 4bbl Holleys for such applications. I wonder if he can do it on a small 2bbl Holley.

I actually tried to get a 2bbl Solex to work in a sealed box, boosted with a Paxton supercharger. The guy thought that pressurizing the whole carb would help with keeping the mixture metered properly. It kinda worked. Gave it up for a set of twin 45-DCOE's.

I actually like this better. But has nothing to do with a Weber post.
dsc00010.jpg  
John Strenk is offline   Reply With Quote
Reply
Thread Tools


Suggested Threads





Jeep, Wrangler, Cherokee, Grand Cherokee, and other models are copyrighted and trademarked to Jeep/Chrysler Corporation. JeepForum.com is not in any way associated with Jeep or the Chrysler Corp.