Which is faster carb or Fuel injection?

[Bench Racer]

Does anyone know what cfm a 48mmGM throttlebody flows? I would guess maybe 580cfm but this is a wild guess. I cant see how it would be close to a Q-jet's cfm. Just thinking out of the box but I would think the performance advantage of the efi would be a imediate throttle response with improved low rpm torque, with the carb making more total top end power while giving up some on the bottom end. The larger LS-1 or the drag pack efi I think would be superior to a carb in all rpm ranges. Just my $0.02. Don Jackson.

[Tom keedle]

well, seeing how a throttle body (port fuel setup) flows ONLY air and not a fuel/air mix, I can see a less cfm TB flow as much air as a Q-jet....just my opinion...


is a carb flowed "wet"?

[art leong]

Originally Posted by Bench Racer

Does anyone know what cfm a 48mmGM throttlebody flows? I would guess maybe 580cfm but this is a wild guess. I cant see how it would be close to a Q-jet's cfm. Just thinking out of the box but I would think the performance advantage of the efi would be a imediate throttle response with improved low rpm torque, with the carb making more total top end power while giving up some on the bottom end. The larger LS-1 or the drag pack efi I think would be superior to a carb in all rpm ranges. Just my $0.02. Don Jackson.

Don. The smaller throttlebody only flows air not a mixture.
I had a real hard time grasping throttlebody do's and dont's. I might not be right now. But the way I under stand it (simplified) the throttlebody is basicly feeding one cylinder (at max) at a time.
I had a 65mm throttlebody (probably over sized) on my 4 cylinder Neon and a box manifold feeding all 4 cylinders. I switched to 4 Individual Throttlebodies each one directly feeding a cylinder. Each throttlebody is 52mm. It took a long time to sink into my brain that this setup wasn't way to big. But it finally sunk in that the motor was only feeding one cylinder at a time (100%) and one throttlebody over each hole needed to be big enough to feed that cylinder.

[Rich Biebel]

Originally Posted by Bench Racer

Does anyone know what cfm a 48mmGM throttlebody flows? I would guess maybe 580cfm but this is a wild guess. I cant see how it would be close to a Q-jet's cfm. Just thinking out of the box but I would think the performance advantage of the efi would be a imediate throttle response with improved low rpm torque, with the carb making more total top end power while giving up some on the bottom end. The larger LS-1 or the drag pack efi I think would be superior to a carb in all rpm ranges. Just my $0.02. Don Jackson.

If the 48mm throttle body was too small an LT-1 engine would likely run weak when built as a SuperStock engine....The throttle body would limit performance.....and thats what I thought when I raced one in Stock...

From the numbers I have seen those engines run in SS/IA or SS/JA or in a GT car......they run very well.....so I think the 48 mm throttle body's ability to move air can not be directly compared to a carb like a Q-jet that flows air and fuel....

[SuperStock 1890]

LT1 throttle body 783cfm at 28"
If I remember right it was 660 cfm at 20"

[Mike Taylor 3601]

If memory is right Holley is flowed dry @ 17''
Q-jet can't remember but some reason dry @ 12'' is coming to mind?
Have info on Q jet but have to dig out,but not tonight, well this morning.
I always heard Carter's ratings were wet flow #'s ?

Going back there was huge difference in tunnel ram w/660's vs Crower injection.
My Dad has Crower he bought new around 1970 back then cost $ 375.00 is what he always told me,he sent to Kinsler and had redone in late 80's cost about $3000.00

Mike Taylor 3601

[Ed Wright]

Originally Posted by SuperStock 1890

LT1 throttle body 783cfm at 28"
If I remember right it was 660 cfm at 20"

That is more than I was told. Dave Layer knows. Maybe he will see this and let us know.

[Rich Biebel]

Originally Posted by SuperStock 1890

LT1 throttle body 783cfm at 28"
If I remember right it was 660 cfm at 20"

Very good info right there that I had never heard before and it explains why an LT-1 can run
pretty fast as a SS'er or a Stocker...

[Ed Wright]

But, if carbs are flowed at 12", that makes the LT1 throttle body smaller. Quadrants are 750 & 800 at 12", right? That throttle body won't be that at 12".

[rawhide]

Originally Posted by Ed Wright

But, if carbs are flowed at 12", that makes the LT1 throttle body smaller. Quadrants are 750 & 800 at 12", right? That throttle body won't be that at 12".

Holley four barrel carbs are flowed at 1 1/2" of mercury which is a little more than 20" of water. I don't know what others are tested at. The two barrel carbs from Holley are tested at 3" of mercury from what I have read.
Roland