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Author
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Topic: what size
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two89w
Gearhead Posts: 314
From: sydney australia
Registered: Sep 2002
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posted 07-08-2004 06:32 AM
   
The picture below is my new efi set up.I have two choices when it comes to throttle body size 45mm or 50mm.
What size should I use?
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JCQuinn@work
Gearhead Posts: 898
From: Lakewood, CO, USA
Registered: Jun 2001
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posted 07-08-2004 10:16 AM
What is the airflow of each size?A stock 289/302 is happy with 600cfm, a modified engine can use up to 750cfm. Bigger engines of course can use more but it really depends on the RPM range you are going to be operating in. Looks extra cool, I want one. John
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wildfire466
unregistered
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posted 07-08-2004 11:07 AM
Here ya go! I cant get it to line up but the first number after CFM is with one plate. The next number is with two plates, ect.
LesThrottle body size for # of plates CFM 1 2 4 8
1007 CFM = 86mm 62mm 45mm 32mm
957 CFM = 84mm 61mm 44mm 31mm
906 CFM = 82mm 59mm 43mm 31mm
856 CFM = 80mm 58mm 41mm 30mm
806 CFM = 78mm 56mm 40mm 29mm
755 CFM = 75mm 54mm 39mm 28mm
705 CFM = 73mm 53mm 38mm 27mm
655 CFM = 70mm 51mm 36mm 26mm
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http://www.geocities.com/wildfire1mustang/
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Daniel Jones
Gearhead Posts: 872
From: St. Louis, MO
Registered: Aug 99
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posted 07-08-2004 06:26 PM
> A stock 289/302 is happy with 600cfm, a modified engine can use up to 750cfm.That sort of sizing information is for a plenum intake and does not
apply to independent runner induction. 48mm IDA's are restrictive above
480 HP or so. Shelby ran 48IDA's on his road race 289's. However,
the EFI throttle bodies flow better than IDA's. The EFI throttle
bodies are available in various sizes from 45 to 58mm. The 58mm units
are used on big block applications such as 427 (or larger stroker versions)
FE Fords in Cobras. The primary problem with going too large is throttle
sensitivity. You'll get a very large percentage of maximum power for a
small throttle opening. This can be minimized with a non-linear throttle
linkage. It's critical to get the throttles synchronized and a have a
non-binding linkage. I've been told for my application (410+ cubes),
a throttle body slightly larger than my intake valve is desirable. With
my 2.19" intake valve and the available throttle bodies, I'm looking into
56mm. Dan Jones
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JCQuinn@work
Gearhead Posts: 898
From: Lakewood, CO, USA
Registered: Jun 2001
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posted 07-09-2004 10:26 AM
Thank you Daniel, you are always a source of interesting information. I have always heard that IR systems need more airflow but this is the first time I have seen a specific guideline.John
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Fastymz
Moderator Posts: 20622
From: Reno Nv USA M&M#1240
Registered: Apr 2001
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posted 07-09-2004 01:18 PM
I can't help you, but that is one BAD set up.  ------------------
SCOOP oddly obsessed with big scoops on little Mustangs 65 coupe,351w,C4,Big Boss 429 hood scoop,8" 3.40 TracLoc. My Pics The older I get
The better I was
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Buster
Gearhead Posts: 1551
From: Hurricane alley
Registered: May 2002
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posted 07-13-2004 09:29 PM
quote:
Originally posted by two89w:
The picture below is my new efi set up.I have two choices when it comes to throttle body size 45mm or 50mm.
What size should I use?
I don't know what size you should use.... However, I think that setup is just bad to the bone!!!! Now that's something I would like to try.....
[This message has been edited by Buster (edited 07-13-2004).]
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TomP
Gearhead Posts: 6000
From: Delta BC Canada
Registered: Dec 99
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posted 07-13-2004 10:08 PM
As you can interpret from the chart if each cylinder flowed 250cfm (2000cfm total for 8)then 45mm would be barely adequate.
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