Go Back   EcoModder Forum > EcoModding > General Efficiency Discussion
Register Now
 Register Now
 

Reply  Post New Thread
 
Submit Tools LinkBack Thread Tools
Old 05-17-2014, 08:47 AM   #1 (permalink)
EcoModding Lurker
 
Join Date: Apr 2014
Location: Central OK
Posts: 24

Slow Silver - '09 Chevy Cobalt XFE Coupe
90 day: 37.56 mpg (US)

GMC pickup - '86 GMC C1500

Hephaestus - '09 Kawasaki Vulcan 900 Custom
90 day: 47.13 mpg (US)
Thanks: 1
Thanked 2 Times in 2 Posts
Multiple Throttle Plates

While I was cleaning/rebuilding the carburetor on my old truck, I thought about how it works as compared to the eTB of my car. I remember from experience and the handy-dandy Haynes manual (best 40$ you can spend IMO), that the secondary throttle plates dont open until the engine looses vacuum. So the old Q-Jet would operate at normal temps and cruising as a small two-barreled carb at WOT, which is what made it so efficient (for a carb). It was only when pedal to the floor that the HUGE secondary's would open to give the engine all 650cfm the carb has.

So my query is this: If a 4-barreled carb operates as a small, unrestricted two-barrel at anything below WOT, would a multiple throttle plate system be of any use to a modern EFI? As in, staged throttles which could provide *unrestricted* flow but still not full power flow. If that makes any sense?

Anyway, that old truck would do 16-18mpg so long as I kept it about 60mph, I thought that was alright for a brick of steel as old as me and no overdrive.

  Reply With Quote
Alt Today
Popular topics

Other popular topics in this forum...

   
Old 05-17-2014, 10:28 AM   #2 (permalink)
Master EcoModder
 
Join Date: May 2012
Location: Tampa, FL
Posts: 1,561

Volt, gas only - '12 Chevrolet Volt Premium
90 day: 38.02 mpg (US)

Volt, electric only - '12 Chevrolet Volt Premium
90 day: 132.26 mpg (US)

Yukon Denali Hybrid - '12 GMC Yukon Denali Hybrid
90 day: 21.48 mpg (US)
Thanks: 169
Thanked 346 Times in 240 Posts
I dont think so. With efi the computer keeps a specific ratio of air:fuel. Having a smaller throttle would limit power but the ratio would.be unchanged. Kind of like the testing done regarding dirty air filters on efi engines.
__________________




  Reply With Quote
The Following User Says Thank You to ksa8907 For This Useful Post:
Cobb (05-17-2014)
Old 05-17-2014, 11:17 AM   #3 (permalink)
Too busy for gas stations
 
Superfuelgero's Avatar
 
Join Date: May 2013
Location: The intersection of TN/MS/AL
Posts: 460

Turtle - '92 Honda Civic Vx
Team Honda
90 day: 67.09 mpg (US)

Rolla - '10 Toyota Corolla Le

Beast - '91 Chevy V2500

Bus - '01 VW Eurovan MV

Speed - '93 Harley bored and storked Harley w/ turbo/ nitrous
90 day: 53.09 mpg (US)

Cal - '68 Ford Mustang GT/CS
Thanks: 87
Thanked 175 Times in 113 Posts
Yes and no. On carbs, its to keep the velocity up at the throttle plate. On efi this isnt needed since fuel isn't added there.
Read this
AutoZine Technical School
__________________
Shooting for 600 miles of range at 65-70 mph out of a vx.

  Reply With Quote
The Following User Says Thank You to Superfuelgero For This Useful Post:
Mista Bone (05-21-2014)
Old 05-17-2014, 04:07 PM   #4 (permalink)
It's all about Diesel
 
cRiPpLe_rOoStEr's Avatar
 
Join Date: Oct 2012
Location: Porto Alegre, Rio Grande do Sul, Brazil
Posts: 8,637
Thanks: 0
Thanked 951 Times in 842 Posts
Some newer engines don't even have a throttle plate anymore, relying only in the valve timing for that matter.
  Reply With Quote
Old 05-17-2014, 07:47 PM   #5 (permalink)
Master EcoModder
 
Join Date: May 2012
Location: USA
Posts: 2,643
Thanks: 1,503
Thanked 276 Times in 226 Posts
I know the early water cooled vws had a secondary throttle that opened up at like 75% throttle. With its CIS injection system you can feel and hear it when that secondary opened up. VVVvvvrrrroooooommmmmmmm.
  Reply With Quote
Old 05-18-2014, 05:47 AM   #6 (permalink)
It's all about Diesel
 
cRiPpLe_rOoStEr's Avatar
 
Join Date: Oct 2012
Location: Porto Alegre, Rio Grande do Sul, Brazil
Posts: 8,637
Thanks: 0
Thanked 951 Times in 842 Posts
Quote:
Originally Posted by Cobb View Post
I know the early water cooled vws had a secondary throttle that opened up at like 75% throttle. With its CIS injection system you can feel and hear it when that secondary opened up. VVVvvvrrrroooooommmmmmmm.
An uncle of mine had a Brazilian Volkswagen Pointer GTi, basically a rebadged Ford Escort with a Volkswagen EA827 engine, and I don't remember it having a secondary throttle plate. But I do remember some carburettors which featured a dual-stage throttle, such as the Weber 450, locally known as "mini progressivo".
  Reply With Quote
Old 05-18-2014, 10:40 AM   #7 (permalink)
Master EcoModder
 
Join Date: Jan 2012
Location: United States
Posts: 1,505

spyder2 - '00 Toyota MR2 Spyder
Thanks: 93
Thanked 292 Times in 229 Posts
Quote:
Originally Posted by cRiPpLe_rOoStEr View Post
Some newer engines don't even have a throttle plate anymore, relying only in the valve timing for that matter.
Actually they do have throttle plates, but they're not used in normal operation. They are there for limp-mode and possibly cold start.
  Reply With Quote
Old 05-18-2014, 10:54 PM   #8 (permalink)
Master EcoModder
 
Join Date: May 2012
Location: USA
Posts: 2,643
Thanks: 1,503
Thanked 276 Times in 226 Posts
Cool







Quote:
Originally Posted by cRiPpLe_rOoStEr View Post
An uncle of mine had a Brazilian Volkswagen Pointer GTi, basically a rebadged Ford Escort with a Volkswagen EA827 engine, and I don't remember it having a secondary throttle plate. But I do remember some carburettors which featured a dual-stage throttle, such as the Weber 450, locally known as "mini progressivo".
  Reply With Quote
Old 05-19-2014, 08:59 AM   #9 (permalink)
Spaced out...
 
spacemanspif's Avatar
 
Join Date: Jul 2013
Location: Dirty Jersey
Posts: 748

The New Focus - '07 Ford Focus ZX5
90 day: 32.44 mpg (US)
Thanks: 142
Thanked 204 Times in 148 Posts
The quadrajet that came factory on my Monte Carlo used a similar setup with 2 small primaries that were good for easy cruising and 2 BIG secondaries for when your foot got heavy. Others with better tuned engines than mine have reported getting close to 25mpg highway. Best I ever saw was around 18.

I don't think multi-carb intakes work in the same manner. Usually a dual quad setup has a runner dedicated to each port on the carbs. However, a stock 6-pack intake might use the 2nd and 3rd carbs in progression to keep up with needed power...not sure how exactly the worked though.
__________________
-Mike

2007 Ford Focus ZX5 - 91k - SGII, pending upper and lower grill bocks - auto trans
1987 Monte Carlo SS - 5.3/4L80E swap - 13.67 @ 106
2007 Ford Focus Estate - 230k - 33mpg - Retired 4/2018
1995 Saturn SL2 - 256K miles - 44mpg - Retired 9/2014

Cost to Operate Spreadsheet for "The New Focus"

  Reply With Quote
Old 05-19-2014, 11:10 AM   #10 (permalink)
EcoModding Lurker
 
Join Date: Apr 2014
Location: Central OK
Posts: 24

Slow Silver - '09 Chevy Cobalt XFE Coupe
90 day: 37.56 mpg (US)

GMC pickup - '86 GMC C1500

Hephaestus - '09 Kawasaki Vulcan 900 Custom
90 day: 47.13 mpg (US)
Thanks: 1
Thanked 2 Times in 2 Posts
I'm thinking that a properly tuned American small block v8 powering a relatively light weight vehicle, such as a small pickup or mid sized RWD car, should be capable of low 30's mpg. Of course there are many many variables that would have to be sorted out, and building one of these vehicles for FE is nearly anathema to the whole point of putting an American v8 into a lightweight car....but I don't really see why we couldn't haul mass while growing grass.

  Reply With Quote
Reply  Post New Thread


Thread Tools




Powered by vBulletin® Version 3.8.11
Copyright ©2000 - 2021, vBulletin Solutions Inc.
Content Relevant URLs by vBSEO 3.5.2
All content copyright EcoModder.com