Author Topic: 20r Carb Study Tagent... Why would anyone do that?  (Read 4515 times)

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H8PVMNT

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20r Carb Study Tagent... Why would anyone do that?
« on: May 03, 2017, 01:29:26 PM »
So now I'm really going nuts!  I have been doing some math (146 CI X 5,500 RPM / 3,456 x .85 = 197.50 CFM) and what I have found puts the 326 CFM 22r carb into the over-carbed zone for a typical 22r.  Now I don't think we notice this while sucking through the restrictive factory filter box, but when you free things up and start getting some throttle response, then things go awry.  Porky fuel economy, strange drivability etc.

I am running a 20r head and intake so this allows me to run a 22r carb with an adapter or the 20r carb strait up.

The 20r carb is supposedly 190 CFM, which should put it right in the sweet spot. It also has a vacuum secondary which is interesting and should be ideal for an overweight trail rig.  I have one on my 1980 pickup and have never felt disappointed in it.  I rebuilt one and rigged it up with a manual choke and took some of the junk off.  Maybe it will be great, maybe it will suck.  I'm sure everybody has been up at night just wondering how it might be to try this but you all have been afraid to ask :gap:.   One thing is the 20r carb is TALL.  Barely clears the hood with the open filter on it. 

We will see what happens...








« Last Edit: May 03, 2017, 02:34:08 PM by H8PVMNT »
“I would rather wake up in the middle of nowhere than in any city on earth.”
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emsvitil

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Ed
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86 SR5 XtraCab
22RE  W56B
31x10.50R15

Gnarly4X

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H8PVMNT,

I think the MPG you are getting is about right for your elevation 3300 to 3400 feet.  If you were to drive your Runner down here in AZ, I'd bet a 6-pack that you'd be getting around 19 to 20.. and that's about the average I got with my 1985 22R shortbed, 5-speed.

I did the Rubicon twice and the Dusey Irshim Trail twice - with my 1986 22RE, Longbed automatic.  The Dusy is about a 31 mile trail.  The Dusy trail goes up to about 9,600 feet elevation.

On the 2nd trip to the Dusy, I told the guys with the V-8 carb'd engines that their MPG was going to be 1 to 2 MPG... they laughed at me.   Every one of the carb'd V-8s ran out gas before we got to the end of trail, and had to share extra fuel some guys carried.

Gnarls.
« Last Edit: May 03, 2017, 04:02:10 PM by Gnarly4X »
1986 XtraCab SR5 22RE 5speed W56B, ~16,000 MI after break-in, DIM (Did It Myself) rebuilt engine - .020" over, engnbldr RV head, OS valves, 261C cam, DT Header. https://imgur.com/oACTHTR

God Bless Our Troops... Especially Our Snipers. The 2nd defends the 1st
MEMBER: WWP, T2T, VFW, NRA, GOA, SAF, Mammoth Nation, C2 Tactical, Hillsdale College, Humane Society of the U.S. - "We cannot solve our problems with the same thinking we used to create them." ~ Albert Einstein

H8PVMNT [OP]

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Yeah your probably right but I have to try :).  I'm pushing a lot of wind with this particular vehicle too.

My initial impressions, just watching the gas gauge, are this thing is even more of a porky hog than the 22r carb.  The secondary diaphragm is a little sticky and stiff.  You can feel when it crumples in abruptly.  I will replace it if I can get this thing to do all right.

Throttle response is a bit slower, acceleration is pretty on par with the 22r carb and the stock filter box.  Highway feels about the same with maybe a little more mid range staying power, probably due to the smaller primary.  Low speed feels identical.  Top end is less.  If you try to get the 3rd downshift and wrap it out pulling a steep hill you wheeze out.  This actually surprised me and it must have something to do with the vac secondary vs. mechanical. You can accelerate up to 5,000 rpm just fine, you just can ask for it abruptly like you can with the 22r carb.

I may put the stock filter setup on this and see what goes on.
« Last Edit: May 04, 2017, 07:55:08 AM by H8PVMNT »
“I would rather wake up in the middle of nowhere than in any city on earth.”
– Steve McQueen

"Except for maybe Seattle."  -H8PVMNT

"I plan to hit 300k in this truck"  :)bestgen4runner

 "I'm jealous of your shop. It has concrete and doesn't smell like pickles like the old shop  "  300K

H8PVMNT [OP]

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Hey Gnarls do you think our volumetric efficiency on an engine like this is north of 85%?  I didn't think so.
“I would rather wake up in the middle of nowhere than in any city on earth.”
– Steve McQueen

"Except for maybe Seattle."  -H8PVMNT

"I plan to hit 300k in this truck"  :)bestgen4runner

 "I'm jealous of your shop. It has concrete and doesn't smell like pickles like the old shop  "  300K

H8PVMNT [OP]

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This some-bitz is getting me right between 9 & 10 mpg!  :scared: I think I'll run it just long enough to replace the AAP and do some fine tweaking on my 22r carb and box this one up for my buddy's 76 2WD.

I would mess with it more but it's just not very game to give me good results.  The 20r carb is OK on a smaller truck with a 20r but I think I can eliminate any notions I had of less CFM working out.  I had to know for myself though, so I guess I succeeded in that.
“I would rather wake up in the middle of nowhere than in any city on earth.”
– Steve McQueen

"Except for maybe Seattle."  -H8PVMNT

"I plan to hit 300k in this truck"  :)bestgen4runner

 "I'm jealous of your shop. It has concrete and doesn't smell like pickles like the old shop  "  300K

Gnarly4X

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Hey Gnarls do you think our volumetric efficiency on an engine like this is north of 85%?  I didn't think so.

Here's a close estimate.

Attached Excel sheet.

Gnarls.

1986 XtraCab SR5 22RE 5speed W56B, ~16,000 MI after break-in, DIM (Did It Myself) rebuilt engine - .020" over, engnbldr RV head, OS valves, 261C cam, DT Header. https://imgur.com/oACTHTR

God Bless Our Troops... Especially Our Snipers. The 2nd defends the 1st
MEMBER: WWP, T2T, VFW, NRA, GOA, SAF, Mammoth Nation, C2 Tactical, Hillsdale College, Humane Society of the U.S. - "We cannot solve our problems with the same thinking we used to create them." ~ Albert Einstein

H8PVMNT [OP]

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That was interesting.  Nothing to see there.  I took it off and put the 22r carb back on :).
“I would rather wake up in the middle of nowhere than in any city on earth.”
– Steve McQueen

"Except for maybe Seattle."  -H8PVMNT

"I plan to hit 300k in this truck"  :)bestgen4runner

 "I'm jealous of your shop. It has concrete and doesn't smell like pickles like the old shop  "  300K

emsvitil

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 :therethere:
Ed
SoCal
86 SR5 XtraCab
22RE  W56B
31x10.50R15

Gnarly4X

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This some-bitz is getting me right between 9 & 10 mpg!  :scared: I think I'll run it just long enough to replace the AAP and do some fine tweaking on my 22r carb and box this one up for my buddy's 76 2WD.

I would mess with it more but it's just not very game to give me good results.  The 20r carb is OK on a smaller truck with a 20r but I think I can eliminate any notions I had of less CFM working out.  I had to know for myself though, so I guess I succeeded in that.

If the 20R carbs flow 190 cfm and the 22R carbs flow 326 cfm, why would a 20R carb work on a 22R? :dunno:

More FLOW... More GO.. :gap:

Gnarls.

« Last Edit: May 06, 2017, 03:51:58 AM by Gnarly4X »
1986 XtraCab SR5 22RE 5speed W56B, ~16,000 MI after break-in, DIM (Did It Myself) rebuilt engine - .020" over, engnbldr RV head, OS valves, 261C cam, DT Header. https://imgur.com/oACTHTR

God Bless Our Troops... Especially Our Snipers. The 2nd defends the 1st
MEMBER: WWP, T2T, VFW, NRA, GOA, SAF, Mammoth Nation, C2 Tactical, Hillsdale College, Humane Society of the U.S. - "We cannot solve our problems with the same thinking we used to create them." ~ Albert Einstein

H8PVMNT [OP]

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Well I just had to answer the question for myself :).
“I would rather wake up in the middle of nowhere than in any city on earth.”
– Steve McQueen

"Except for maybe Seattle."  -H8PVMNT

"I plan to hit 300k in this truck"  :)bestgen4runner

 "I'm jealous of your shop. It has concrete and doesn't smell like pickles like the old shop  "  300K

Gnarly4X

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Well I just had to answer the question for myself :).

Yep...that's exactly why I've spend so much time trying figure out the answers myself.  It's not that I don't believe the "experts" and all the posts I read, the suppliers, and my FSM..... "I just need to answer the question for myself".  :D

Gnarls. :inthedark:
1986 XtraCab SR5 22RE 5speed W56B, ~16,000 MI after break-in, DIM (Did It Myself) rebuilt engine - .020" over, engnbldr RV head, OS valves, 261C cam, DT Header. https://imgur.com/oACTHTR

God Bless Our Troops... Especially Our Snipers. The 2nd defends the 1st
MEMBER: WWP, T2T, VFW, NRA, GOA, SAF, Mammoth Nation, C2 Tactical, Hillsdale College, Humane Society of the U.S. - "We cannot solve our problems with the same thinking we used to create them." ~ Albert Einstein

 
 
 
 
 

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