What is the CFM

[Craven]

Just wondering if anybody knows the CFM of a 32/36 DGEV weber carb?

[The Scooby]

all the DGV series are 325cfm.

[RXTurbo]

I was under the impression that a 32/36 was a 180cfm carb, which comes from the same carb but Holley branded is a Holley 180, and Holley's naming convention was to name them by their cfm rating?

[GeneralDisorder]

The 32/36 DFV series is the same as the holley/weber 5200 series. It also has smaller venturi's than a DGV.... well at least the ford ones do. The Holley 5200 carbs on 70-82 Fords have a 23mm primary venturi. The DGV has 28mm primary venturi's....

 

CFM of a holley 5200 (DFV): 235

CFM of a 32/36 DGV: 330

 

P.S. Holley G180 is the Ausie version of the 5200... both are licensed from Weber.

 

GD

[Craven]

What I've been finding out here and over the web, the weber dgv is around 330 cfm and that not all holley 5200's are the same. Some Fords R7343 with 23mm primary venturi were rated at 235 CFM and the R9228 with 26mm primary venturi 280 CFM. The 5210 (same basic carb) that came on some of the Chevy Vega's were 250 cfm. Holley states 280 cfm for most of the 5200s except the R7343. All of which are more than a stock or slighty modifyed 1800 needs.

Using the cfm calculator here http://www.carbs.net/calc.asp and using a equation from Donlson air cleaners 180 cfm is all you should need. Unless you wind your engine higher than 6000 rpm.

[RXTurbo]

So what is the CFM rating of the Hitachi 28/32 the EA motors come with?

[JonOfScio]

I think the Hitachi is either 130 or 150cfm max.

[GeneralDisorder]

Using the cfm calculator here http://www.carbs.net/calc.asp and using a equation from Donlson air cleaners 180 cfm is all you should need

Your are forgetting that most of us are not interested in the maximum volume, but rather the low end torque that a BIG barrel gives you. That's why people run dual 40mm carbs on 1.6l VW's.....

 

GD

[Craven]

GeneralDisorder

 

A gasoline engine is just an air pump. The volume of air it can move is dictated by the displacment, Volumetric Efficiency and RPM. You can put as big a carb as you want on an engine as long as the air/fuel mix is correct and engine will pull only as much air as it can. Too big of carb and on the road and feel your throttle response go away and your low-speed power drop off. That's because big carbs have trouble metering fuel correctly at low thottle openings and will subsequently make less power down low, which is where you spend most of your time driving, unless you only drive at the Dragstrip. I'm not saying a Weber is to big by any means, but you are only using 180 CFM or so out of the 330 the weber can supply.

I think you are confusing low end torque with thottle response. The Weber is a very good carburator and regulates the fuel mix far better than the stock piece it replaces.

 

Craven

[GeneralDisorder]

Try a weber, and you will see what I mean about torque. The Hitachi is fine with throttle response. One of the biggest drawbacks is the vacuum operated secondary of the Hitachi. The progressive linkage of the Weber allows both barrels to be opened quickly. You are of course right that the engine can't really use the Weber to it's full capacity, but the progressive linkage and larger primary really help the low end.

 

Also remember that the total CFM of the Weber is 330 - that's with both barrels fully open. When your talking about partial throttle, the large secondary is closed, and the primary is only open part way. So the CFM of the Weber rises more quickly as you open the throttle plate. This changes the amount of air that the engine is allowed to draw at partial throttle, and gives rise to the better torque at lower RPM's.

 

Call it what you want - throttle response, low end - it's a marked improvment over the Hitachi in several ways. I use the term "low end" because as you have pointed out the high end won't be affected at all with the Weber. The engine just can't use it. Thus the improvements are to be gained on the low end of the RPM range. This has been my experience with Weber's.

 

GD

[Craven]

GD

 

Then we pretty much agree.

 

Craven

[RXTurbo]

Would there be any advantage to enlarging the stock throttle bodies to 32 and 36 rather than the 28 and 32 of the stock carb?

 

I have the tooling and ability to make a new throttle plate to replace the stock hitachi item with a larger bore and mechanically operated. Question is, would it be worth it? What about if it was say 32/32 so you get the advantage of the larger primary, but the suitable metering of the stock sized secondary? Any thoughts?

[GeneralDisorder]

I'm not sure I understand what you are talking about.... we are talking carbs here, not throttle body injection.... maybe we are mixing terminology....

 

Or are you saying you can make new throttle *bases* for the existing hitachi carb? If that's the case, then the answer is no - haveing a larger throttle base won't do you much good at all, since the venturi in the carb is so tiny. The size of the throttle plates is actually not very indicative of the flow rate of the carb - as we were talking about above, different versions of the same "32/36" carb have very different flow characteristics because of the different venturi sizes. The Ford holley/weber 5200 series has a flow of only 235 CFM, while the same "32/36" DGV Weber has a flow of 330 CFM - because of the venturi sizes.

 

Also - the EA series Hitachi's are not all the same. The EA81 used a 26/30 carb, and the EA82 used both a 28/30 (automatics), and a 28/32. Just thought I would toss that out for reference.... they also have different mounting surfaces between EA81 and EA82.

GD

[RXTurbo]

Yes, I was talking about a new throttle base for the hitachi carb, but if it is the venturi size that is the issue then fair enough. As for the interchangeability of carbs, This weekend just gone I swapped the throttle base from an EA81 carb onto an EA82 carb (as the EA82 one was leaking). The base had a 28 primary and a 32 secondary on both carbs. The EA81 carb I believe was from a brat/brumby although I can't be certain as the motor was in my '82 coupe which I am dismantling. Anyway the only difference in the base was the EA81 had a idle mixture screw and the EA82 one did not, no problem though as I just adjusted it until it ran smooth, it does idle a bit high but I think I may have bent the butterfly swapping it over (but that's another story...)

 

I guess an efi system is for me, I can't handle these carb things :-\

[GeneralDisorder]

Check the model number on the float bowl of the "EA81" carb you used. The model of an EA81 carb will be a DCP-306-??. The model on the EA82 carbs is DCZ-308-?? or DCZ-328-??. The "306", "308", and "328" indicate the size of the barrels. All EA81's thus have a 26/30, and the EA82's are 28/30, or 28/32......

 

GD