Which is faster carb or Fuel injection?

Rich Biebel · 07-26-2013, 07:41 PM

Quote:

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 · 07-26-2013, 08:29 PM

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

Mike Taylor 3601 · 07-27-2013, 02:55 AM

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 · 07-27-2013, 08:38 AM

Quote:

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 · 07-27-2013, 08:40 AM

Quote:

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 · 07-27-2013, 09:09 AM

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 · 07-27-2013, 04:11 PM

Quote:

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

Ed Wright · 07-27-2013, 09:42 PM

Quote:

Originally Posted by rawhide

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

That would make it 660 cfm, which about what I was told. Dave Layer told me my LT2 SS engine would be done about 8200 due to the throttle body restriction. It falls off a cliff about 8300 on the dyno. The 305" TPI cars have the same size, if I remember correctly (been a couple of years now.) Dave said the 305"s run right up to 8800/9000. Hope I remember the numbers correctly.

Adger Smith · 07-27-2013, 11:51 PM

Joe ask the question: All things being equal in a stocker, lift, valve, piston, head, etc.. what would be faster a carb or fuel injection?

The question has not been answered, yet, and probably will never be because of those first 4 words in his question. I'll add 3 more words that will always keep them unequal... Wet & Dry flow.

07-26-2013, 08:29 PM	#2
SuperStock 1890 Junior Member Join Date: Aug 2005 Posts: 87 Likes: 0 Liked 0 Times in 0 Posts	Re: Which is faster carb or Fuel injection? LT1 throttle body 783cfm at 28" If I remember right it was 660 cfm at 20" __________________ You don't know what you don't know yet.

07-27-2013, 02:55 AM	#3
Mike Taylor 3601 VIP Member Join Date: Oct 2008 Location: Somerset,Ky Posts: 1,374 Likes: 359 Liked 308 Times in 103 Posts	Re: Which is faster carb or Fuel injection? 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

07-27-2013, 09:09 AM	#6
Ed Wright Veteran Member Join Date: Mar 2005 Location: Sand Springs, OK Posts: 8,132 Likes: 896 Liked 390 Times in 170 Posts	Re: Which is faster carb or Fuel injection? 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". __________________ Ed Wright 4156 SS/JA

07-27-2013, 11:51 PM	#9
Adger Smith VIP Member Join Date: Dec 2001 Location: Texarkana Ark/TX Posts: 2,446 Likes: 575 Liked 880 Times in 311 Posts	Re: Which is faster carb or Fuel injection? Joe ask the question: All things being equal in a stocker, lift, valve, piston, head, etc.. what would be faster a carb or fuel injection? The question has not been answered, yet, and probably will never be because of those first 4 words in his question. I'll add 3 more words that will always keep them unequal... Wet & Dry flow. __________________ Adger Smith (Former SS)