Go Back   EcoModder Forum > EcoModding > EcoModding Central
Register Now
 Register Now
 

Reply  Post New Thread
 
Submit Tools LinkBack Thread Tools
Old 02-08-2018, 09:15 PM   #51 (permalink)
EcoModding Lurker
 
Join Date: Feb 2018
Location: Los Angeles, California, USA
Posts: 20
Thanks: 1
Thanked 3 Times in 2 Posts
Quote:
Originally Posted by Isaac Zackary View Post
Many late model carbureted cars did get grids under their carburetors for emissions purposes.
Yes, the key here is "for emission purposes". These grids are not flow restrictors or turbulence geherators. They are electric heaters that temporarily warm up the intake before water jacket warms up the intake manifold.

Venturi is the narrowest opening in the carburettor and the place where fuel is injected. Maximum speed of air flow through the Venturi facilitates fuel pulverization. Creating flow restriction elsewhere will reduce air speed at the Venturi and thus worsen the pulverization.

  Reply With Quote
Alt Today
Popular topics

Other popular topics in this forum...

   
Old 02-08-2018, 10:30 PM   #52 (permalink)
Full sized hybrid.
 
Isaac Zackary's Avatar
 
Join Date: Apr 2015
Location: Colorado
Posts: 602

Suzy - '13 Toyota Avalon Hybrid XLE
90 day: 37.18 mpg (US)
Thanks: 369
Thanked 108 Times in 84 Posts
Quote:
Originally Posted by sser2 View Post
Yes, the key here is "for emission purposes". These grids are not flow restrictors or turbulence geherators. They are electric heaters that temporarily warm up the intake before water jacket warms up the intake manifold.

Venturi is the narrowest opening in the carburettor and the place where fuel is injected. Maximum speed of air flow through the Venturi facilitates fuel pulverization. Creating flow restriction elsewhere will reduce air speed at the Venturi and thus worsen the pulverization.
My theory is that if you really want to avoid reducing air speed at the venturi then your only option is to remove the throttle.

Yes at full throttle any restriction along the intake will not allow the highest venturi air speed. But at part throttle your biggest restriction is the throttle, and I don't see how any restriction along the intake will have any effect at part throttle.

Yes, a dual throat carb can allow the use of a smaller venturi. But I'm not ready to modify the engine to accept a different carb right now.
__________________
  Reply With Quote
Old 02-08-2018, 11:46 PM   #53 (permalink)
Master EcoModder
 
freebeard's Avatar
 
Join Date: Aug 2012
Location: northwest of normal
Posts: 27,562
Thanks: 7,738
Thanked 8,554 Times in 7,041 Posts
When all four cylinders are sucking through the venturi, there will be skin friction all along the path. A restriction at 1/4th" of that path prolly has less effect than the skin friction throughout the full length.

The mass of air will speed up locally, suffer a lot of turbulence and then slow down again.
__________________
.
.
Without freedom of speech we wouldn't know who all the idiots are. -- anonymous poster

____________________
  Reply With Quote
The Following User Says Thank You to freebeard For This Useful Post:
Isaac Zackary (02-09-2018)
Old 02-09-2018, 12:00 AM   #54 (permalink)
Master EcoModder
 
Join Date: Jun 2010
Location: Australia
Posts: 253

Delivery 'Boy - '86 Suzuki Mighty Boy
90 day: 37.15 mpg (US)

SkipSwift - '13 Suzuki Swift GL
90 day: 35.44 mpg (US)
Thanks: 0
Thanked 53 Times in 42 Posts
Quote:
Originally Posted by Isaac Zackary View Post
My theory is that if you really want to avoid reducing air speed at the venturi then your only option is to remove the throttle.

Yes at full throttle any restriction along the intake will not allow the highest venturi air speed. But at part throttle your biggest restriction is the throttle, and I don't see how any restriction along the intake will have any effect at part throttle.

Yes, a dual throat carb can allow the use of a smaller venturi. But I'm not ready to modify the engine to accept a different carb right now.
Well there goes suggesting you get something other than the most basic carburettor ever to be fitted with a choke. You *could* modify one to have an annular discharge venturi, or a booster, or a central discharge point (all of which will improve atomisation) but that's all more difficult to do than finding another manifold and modifying it to fit a progressive dual-throat carb.

This will help atomisation by nature of the high airspeed through the plate and the turbulence immediately after it. It can't *not* do that, assuming the atomisation of the carb is poor to start with.

You can also make up for *some* of the restriction by detailing the carburettor, ie knife edging the throttle body, making the throttle shaft more aerodynamic, repeating that for the choke, making sure the venturi has no casting marks (but don't make it bigger), and so on. Those won't affect the operation of the carburettor but will increase the flow.

Have you got any kind of manifold heating? It seems like that would help, assuming you can avoid pinging.
__________________







Quote:
Originally Posted by Crazyrabbit
In God we trust. All others: bring data
  Reply With Quote
The Following User Says Thank You to BLSTIC For This Useful Post:
Isaac Zackary (02-09-2018)
Old 02-09-2018, 12:34 AM   #55 (permalink)
(:
 
Frank Lee's Avatar
 
Join Date: Jan 2008
Location: up north
Posts: 12,762

Blue - '93 Ford Tempo
Last 3: 27.29 mpg (US)

F150 - '94 Ford F150 XLT 4x4
90 day: 18.5 mpg (US)

Sport Coupe - '92 Ford Tempo GL
Last 3: 69.62 mpg (US)

ShWing! - '82 honda gold wing Interstate
90 day: 33.65 mpg (US)

Moon Unit - '98 Mercury Sable LX Wagon
90 day: 21.24 mpg (US)
Thanks: 1,585
Thanked 3,555 Times in 2,218 Posts
Quote:
Originally Posted by Angel And The Wolf View Post
My ex-brother-in-law went into business with a friend. The friend had built a plate to fit between the carburetor and the manifold. screwed into the plate, at three points from the sides, were three ultrasonic vibrators from a dishwasher.The theory was to pulverize the fuel, and tests on a 390 Galaxie produced 50 mpg. they were blocked at every turn from manufacturing the plate, and ended up selling the rights to Texaco. Someone should give it a try.

__________________


  Reply With Quote
Old 02-09-2018, 01:52 AM   #56 (permalink)
Full sized hybrid.
 
Isaac Zackary's Avatar
 
Join Date: Apr 2015
Location: Colorado
Posts: 602

Suzy - '13 Toyota Avalon Hybrid XLE
90 day: 37.18 mpg (US)
Thanks: 369
Thanked 108 Times in 84 Posts
As far as the Jet-A-Vator is concerned, I am planning on trying the system out both with and without it to see what gets me better fuel mileage. I do think the fine tuning of the carb jetting and the digital ignition map will get me a whole lot better fuel mileage than the Jet-A-Vator will. I just think it's worth the try since I have it.

Quote:
Originally Posted by BLSTIC View Post
...but that's all more difficult to do than finding another manifold and modifying it to fit a progressive dual-throat carb.
I'd need to find one that has a smaller venture than the one I already have. Weber makes a progressive carb, but it seems to have a 32mm main barrel. I'm not sure what the actual venturi size is but it's likely not much different than the 26mm venturi I already have. Also I'd lose my heated air cleaner and the dual heat risers unless I built my own intake manifold and air cleaner.

Deluxe Center Mount Progressive (DFAV/DFEV) Carburetor Kit, Reline, DP Type 1, K1410 - Aircooled.Net VW Parts

Quote:
Originally Posted by BLSTIC View Post
Have you got any kind of manifold heating? It seems like that would help, assuming you can avoid pinging.
Yes, and I got about the best you can get on a VW. It a called a dual heat riser manifold, which are rare in the US since they were only put on 1974 Californian VW's.



As opposed to the much more common single heat riser manifold:

__________________
  Reply With Quote
Old 02-09-2018, 12:18 PM   #57 (permalink)
Master EcoModder
 
freebeard's Avatar
 
Join Date: Aug 2012
Location: northwest of normal
Posts: 27,562
Thanks: 7,738
Thanked 8,554 Times in 7,041 Posts
Quote:
Well there goes suggesting you get something other than the most basic carburettor ever to be fitted with a choke. You *could* modify one to have an annular discharge venturi, or a booster, or a central discharge point (all of which will improve atomisation) but that's all more difficult to do than finding another manifold and modifying it to fit a progressive dual-throat carb.
https://en.wikipedia.org/wiki/Reece_Fish_Carburettor

Quote:
Volkswagen downdraught set

The pictures below show a pair of Reece Fish carburettors with manifold tubing suitable for an air-cooled Volkswagen engine. Note that Reece Fish manufactured the tubing and manifolds as part of an after-market kit for this vehicle.
__________________
.
.
Without freedom of speech we wouldn't know who all the idiots are. -- anonymous poster

____________________
  Reply With Quote
The Following User Says Thank You to freebeard For This Useful Post:
Isaac Zackary (02-09-2018)
Old 02-09-2018, 02:11 PM   #58 (permalink)
Full sized hybrid.
 
Isaac Zackary's Avatar
 
Join Date: Apr 2015
Location: Colorado
Posts: 602

Suzy - '13 Toyota Avalon Hybrid XLE
90 day: 37.18 mpg (US)
Thanks: 369
Thanked 108 Times in 84 Posts
Quote:
Originally Posted by freebeard View Post
That would be interesting to try some day!
__________________
  Reply With Quote
The Following User Says Thank You to Isaac Zackary For This Useful Post:
freebeard (02-09-2018)
Old 02-09-2018, 03:24 PM   #59 (permalink)
Full sized hybrid.
 
Isaac Zackary's Avatar
 
Join Date: Apr 2015
Location: Colorado
Posts: 602

Suzy - '13 Toyota Avalon Hybrid XLE
90 day: 37.18 mpg (US)
Thanks: 369
Thanked 108 Times in 84 Posts
Quote:
Originally Posted by BLSTIC View Post
Well there goes suggesting you get something other than the most basic carburettor ever to be fitted with a choke.
I did base my carb selection on the reputation it has in the VW community, although there are quite a few that stick by their favorite carb "just because".

It has taken me five years to get this car running. And right now I need it for commuting. Some day I might try different carburetors and such, but not right at the moment.
__________________
  Reply With Quote
Old 02-09-2018, 04:13 PM   #60 (permalink)
Master EcoModder
 
freebeard's Avatar
 
Join Date: Aug 2012
Location: northwest of normal
Posts: 27,562
Thanks: 7,738
Thanked 8,554 Times in 7,041 Posts
My Superbeetle needed a 34PICT and I couldn't [at the time] find the one I had laying around. My VW shop ordered the 32PICT and adapter instead. They said it was a more tunable/maintainable/known. ¯\_(ツ)_/¯

__________________
.
.
Without freedom of speech we wouldn't know who all the idiots are. -- anonymous poster

____________________
  Reply With Quote
The Following User Says Thank You to freebeard For This Useful Post:
Isaac Zackary (02-09-2018)
Reply  Post New Thread


Thread Tools




Powered by vBulletin® Version 3.8.11
Copyright ©2000 - 2024, vBulletin Solutions Inc.
Content Relevant URLs by vBSEO 3.5.2
All content copyright EcoModder.com