carburated lt1 ???
08-30-2008, 09:07 PM
#21
TECH Senior Member
iTrader: (3)
Join Date: Oct 2006
Location: Decatur, TN (N-W of Athens)
Posts: 7,564
Likes: 0
Received 4 Likes
on
4 Posts
heh I know that Cap. But if I was even an idiot, I'd know that I had an LT5 and not an LT1.
Well running a much better intake is a different story, but what if he had run an FI system on that intake instead of comparing it to the stock FI setup? What makes me want FI over Card is all in how the fuel gets to where it's going. The carb's dump it in, and while they spray much better than before, the atomization of the injector is still much better since it's spraying fuel x8 instead of x4.
It has been proven that if it is a race car and streetabilty is not a concern carbs still make more power in all the tests I've seen. Hot rob did a 6.0L put a carb on the fuel injected single plain and gained 15hp or so. There are other test that I've seen the same results.
08-31-2008, 09:00 PM
#26
Banned
Join Date: May 2008
Posts: 64
Likes: 0
Received 0 Likes
on
0 Posts
This is a qoute off of another site. Enjoy
UNDER THE SCOOP
Carburetion Vs. Injection
One of the most oft asked questions is why do carburetors make more power then EFI and why do the car manufacturers use EFI if carburetors make more power?
A few years ago we used some contacts at General Motors to verify some simple facts from some dyno data we had received from a head to head comparison.
An engine was being constructed for Comp Eliminator style racing and the program was going to be electronically fuel injected. Well the system was giving the engine shop some questionable numbers. The shop removed the EFI system and installed some of our Pro Stock carburetors on the EFI manifold top so they could quickly compare systems.
The engine responded immediately with much faster acceleration rates and a 5 percent improvement in power.
The EFI designer was brought out to the site and try as he might he could not out perform those carburetors. When the session wrapped up carburetors were king by 24 horsepower.
I've heard similar stories and similar claims when comparing systems.
So when we analyze this information it really comes down to a simple fact. Carburetors and Electronic Fuel injection are two completely different systems. They share no concepts and each has a different theory.
EFI's claim is this: I will supply sprayed droplets of fuel at the proper air to fuel ratio all the time.
Carburetors claim: I will supply a pre-emulsed froth of fuel and air into the engine at a preset ratio.
The results proved the analysis of the concepts to be correct. In this case, the carburetor was supplying the engine in question with the proper air to fuel ratio, so the EFI's advantage was gone. Remember, EFI has a computer to tune the engine. You have you. If you know how to tune you'll have the advantage. Carburetors (at the risk of sounding chauvinistic) are a man's game. Guessing rarely works. You have to know how to actually tune an engine.
Remember a carburetor is an atomization/emulsion machine. An injection system is a proper air to fuel delivery ratio machine. Two different concepts. If a carburetor can be designed to supply the perfect air to fuel ratio all the time it should consistently outperform EFI. Its design lends itself to have an unfair advantage in atomization.
Obviously adiabatic expansion is the next question on the list. So if we take a good look at the carburetor we see its not only a perfect machine for atomizing fuel, it also has another advantage. The joule-thompson effect.
Tests performed using quartz plates and infra red sensors located in the plenum area beneath an NHRA Pro-Stock engine revealed an intake manifold temperature drop on a 85 degree day of almost 20 degrees as a result of the the carburetor creating this effect.
So when your neighbor with EFI is ingesting 85 degree air, your power-plant could be ingesting 65 degree air.
That's a nice advantage.
But let's not skip over the atomization advantage. In a high end designed carburetor the fuel is emulsed to lift it. Its a controlled froth. I won't kid you, it's very difficult to control. Its much easier to build a carburetor that operates on a vacuum to ratio concept. But the fogging advantage is gone. So when a customer asks, why is this carburetor more expensive than that builders carburetor as they look basically the same. Most of it is all in the emulsion package and the time spent flowing it and tweaking it to do its job. Remember in a high emulsion design .001 of an inch is a big deal. They're difficult to balance and require sophisticated equipment that many shops have never seen. Also, don't go poking things into the metering block passages to inspect them or look around. You might just lose 10 lbs of torque.
The disadvantage of carburetors used to be restriction. I remember back 20 years ago before booster technology really took off you had to size carburetors to operate on 1-2 inches of vacuum in the plenum at the starting line. The restriction alone was probably costing these engines a 2-3 percent power loss.
Tests we performed at Sonny's racing 5 years ago showed us numbers of about .6 in the plenum and spikes of about 1.1 to 1.3 in the runner at the finish-line. That's a pretty huge decrease and just for dynos sake when we built carburetors large enough to reduce this number by on average 40 percent we saw an increase of only about 3-5 horsepower on an IHRA Pro-Stocker. SO that advantage for EFI is now also gone.
Now that these same engines can operate on as little as .5 hg of vacuum at the starting line and only 1-1.2 at the finish-line, the restriction is nil. Really it all comes down to getting the air to fuel ratio correct. If a carburetor can do that, it should win the race every time. After all, by design, it's a superior emulsion machine.
Thanks for reading.
UNDER THE SCOOP
Carburetion Vs. Injection
One of the most oft asked questions is why do carburetors make more power then EFI and why do the car manufacturers use EFI if carburetors make more power?
A few years ago we used some contacts at General Motors to verify some simple facts from some dyno data we had received from a head to head comparison.
An engine was being constructed for Comp Eliminator style racing and the program was going to be electronically fuel injected. Well the system was giving the engine shop some questionable numbers. The shop removed the EFI system and installed some of our Pro Stock carburetors on the EFI manifold top so they could quickly compare systems.
The engine responded immediately with much faster acceleration rates and a 5 percent improvement in power.
The EFI designer was brought out to the site and try as he might he could not out perform those carburetors. When the session wrapped up carburetors were king by 24 horsepower.
I've heard similar stories and similar claims when comparing systems.
So when we analyze this information it really comes down to a simple fact. Carburetors and Electronic Fuel injection are two completely different systems. They share no concepts and each has a different theory.
EFI's claim is this: I will supply sprayed droplets of fuel at the proper air to fuel ratio all the time.
Carburetors claim: I will supply a pre-emulsed froth of fuel and air into the engine at a preset ratio.
The results proved the analysis of the concepts to be correct. In this case, the carburetor was supplying the engine in question with the proper air to fuel ratio, so the EFI's advantage was gone. Remember, EFI has a computer to tune the engine. You have you. If you know how to tune you'll have the advantage. Carburetors (at the risk of sounding chauvinistic) are a man's game. Guessing rarely works. You have to know how to actually tune an engine.
Remember a carburetor is an atomization/emulsion machine. An injection system is a proper air to fuel delivery ratio machine. Two different concepts. If a carburetor can be designed to supply the perfect air to fuel ratio all the time it should consistently outperform EFI. Its design lends itself to have an unfair advantage in atomization.
Obviously adiabatic expansion is the next question on the list. So if we take a good look at the carburetor we see its not only a perfect machine for atomizing fuel, it also has another advantage. The joule-thompson effect.
Tests performed using quartz plates and infra red sensors located in the plenum area beneath an NHRA Pro-Stock engine revealed an intake manifold temperature drop on a 85 degree day of almost 20 degrees as a result of the the carburetor creating this effect.
So when your neighbor with EFI is ingesting 85 degree air, your power-plant could be ingesting 65 degree air.
That's a nice advantage.
But let's not skip over the atomization advantage. In a high end designed carburetor the fuel is emulsed to lift it. Its a controlled froth. I won't kid you, it's very difficult to control. Its much easier to build a carburetor that operates on a vacuum to ratio concept. But the fogging advantage is gone. So when a customer asks, why is this carburetor more expensive than that builders carburetor as they look basically the same. Most of it is all in the emulsion package and the time spent flowing it and tweaking it to do its job. Remember in a high emulsion design .001 of an inch is a big deal. They're difficult to balance and require sophisticated equipment that many shops have never seen. Also, don't go poking things into the metering block passages to inspect them or look around. You might just lose 10 lbs of torque.
The disadvantage of carburetors used to be restriction. I remember back 20 years ago before booster technology really took off you had to size carburetors to operate on 1-2 inches of vacuum in the plenum at the starting line. The restriction alone was probably costing these engines a 2-3 percent power loss.
Tests we performed at Sonny's racing 5 years ago showed us numbers of about .6 in the plenum and spikes of about 1.1 to 1.3 in the runner at the finish-line. That's a pretty huge decrease and just for dynos sake when we built carburetors large enough to reduce this number by on average 40 percent we saw an increase of only about 3-5 horsepower on an IHRA Pro-Stocker. SO that advantage for EFI is now also gone.
Now that these same engines can operate on as little as .5 hg of vacuum at the starting line and only 1-1.2 at the finish-line, the restriction is nil. Really it all comes down to getting the air to fuel ratio correct. If a carburetor can do that, it should win the race every time. After all, by design, it's a superior emulsion machine.
Thanks for reading.
08-31-2008, 10:24 PM
#27
TECH Senior Member
iTrader: (3)
Join Date: Oct 2006
Location: Decatur, TN (N-W of Athens)
Posts: 7,564
Likes: 0
Received 4 Likes
on
4 Posts
Well that's a good read. So then to get the most out of your motor, you need to buy a $2K carb to get that extra 24hp?
I'm wondering what our gains would be if we lost 20ºF on IAT. I still want to outfit my intake with Peltiers to drop is far more than that.
I'm interested in a more off-the-shelf comparison.
I'm wondering what our gains would be if we lost 20ºF on IAT. I still want to outfit my intake with Peltiers to drop is far more than that.
I'm interested in a more off-the-shelf comparison.
08-31-2008, 10:36 PM
#28
TECH Fanatic
iTrader: (5)
Join Date: Mar 2004
Location: Melrose, MA
Posts: 1,196
Likes: 0
Received 0 Likes
on
0 Posts
Unless of course you just like/can tune carbs better, and can justify the 2k convesion cost.
09-01-2008, 12:22 AM
#29
TECH Senior Member
iTrader: (3)
Join Date: Oct 2006
Location: Decatur, TN (N-W of Athens)
Posts: 7,564
Likes: 0
Received 4 Likes
on
4 Posts
I mean they're talking about "why this guy's carb is better than the next" which leads me to believe that these carbs aren't mass produced. Thats my assumption at least. 
09-02-2008, 10:33 AM
#32
On The Tree
Thread Starter
iTrader: (4)
Join Date: Jul 2008
Location: New Jersey
Posts: 109
Likes: 0
Received 0 Likes
on
0 Posts
Sorry it took so long to respond. Yes this is an LT1 with Dominion 32 valve heads. I acquired the car and motor about a month ago. This is going to be my winter project. I took a couple of pics this weekend I will post them as soon as i can. thanks for the comments
09-02-2008, 12:20 PM
#33
TECH Senior Member
iTrader: (3)
Join Date: Oct 2006
Location: Decatur, TN (N-W of Athens)
Posts: 7,564
Likes: 0
Received 4 Likes
on
4 Posts
Best of luck to you though.
If you have the money, I'd say do that FI setup with the cross-ram velocity stacks that someone posted around beginning of last week. $2500 for the GM one, but is just so bad ***!!
09-02-2008, 05:55 PM
#34
You are going to need a fabbed intake, injected or carbed.
Far as injection vs. carbs, lots of variables come into play, some popular injectors have a very poor spray pattern, maybe that is what they used for the test.
Carbs certainly can work wonderfully but soon as the weather changes they are no longer perfect.
Far as injection vs. carbs, lots of variables come into play, some popular injectors have a very poor spray pattern, maybe that is what they used for the test.
Carbs certainly can work wonderfully but soon as the weather changes they are no longer perfect.
09-03-2008, 10:19 AM
#35
On The Tree
Thread Starter
iTrader: (4)
Join Date: Jul 2008
Location: New Jersey
Posts: 109
Likes: 0
Received 0 Likes
on
0 Posts
could possibly be the same car and motor combo. He never had it running and lost interest. It has a single plane intake already on it that has been converted to fit. Just so I can get this thing running for now I'll be using a Wilson throttle body. I'm gonna be changing the injectors up to something in the 96 range. I won't be able to really get into the car for about 2 months. So for now I'm just making my parts list.
09-03-2008, 05:24 PM
#36
09-03-2008, 05:31 PM
#37
Your joking right? If changing your injectors, and tune count as boltons then a carb shoud also.
Who made up that rule?
09-03-2008, 05:45 PM
#40
I have never heard that an intake manifold is not a bolt on. I know for a fact the fastest bolton LS1 list does not exclude intake manifold swaps. The fastest car on the list has a Fast manifold on it.