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Discussion Starter #1
what is the difference, response, power, tunability wise, between a well set up carb, and a well set up efi system.

is it HUGE?
 

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when the MSD/eledbrock setup for the Gen3 came out... who ever built the engine.. a gen3 LS1 made around 450hp injected.. when the Edelbrock/MSD carbed kit was installed after tuning... the difference was around 3ftlbs TQ and 5hp peak....

I am sure as peak hp rises the percentages will remain very close.. but like any thing.. as the numbers get larger the percentage stays the same but the numbers rise accordingly
 

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I have on my 383. I would not enjoy going back to a carb. I really cannot tell any difference in power but... razor throttle all the time no matter what the under hood temps are, more finite tuning ability, able to store a performance map and a fuel economy map and only change a thumb wheel to switch between the two. Run a knock sensor which has come in handy a couple of times. Control cooling fans and a/c clutch control with the efi box. Individual cylinder tuning for timing and fuel in wanted.
This is my 5th year on fuel injection, started small and have gotten more sophisticated over the years. My system has been reliable, you just need to get over the initial fear...
Tg
 

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CyanJaguar, I am in the same boat you are and it may look like that I am trying to hijack this thread, I am not. IF I have done so, please let me know.

There's no "ownership" of threads. This is a public discussion forum. You can ask or answer questions in any thread. Paul W.


Mr Griffin,

please explain more on what system you have, the complications you occured during your install and any other tips for CyanJaguar and others ( ME!!) might be thinking on taking that "giant leap" in the near future..


I was told that my specific cam, XE274H was too radical and I should stay with the use of carburetors. I would like to step-up to the TBI set-up, ( Holley Pro-Jection 700 CFM series ) or go with a system from Affordable Fuel Injection, and proceed to have fun but, I wanted to hear from someone that has gone thru this and is able to debunk some myths.

If it all possible, here is a quick look at my motor:

355 4-bolt
64cc 1.94/1.50
9.73 comp ratio
Duration @ 0.050": 230° / 236°
Max Lift w/ 1.5RR: .487" / .490"
Lobe Separation: 110°
Intake Centerline: 106°

Should there be an issue with using the Holley system or an aftermarket TBI set-up? I know that TPI or direct fuel injection is alot better but, I would like to make baby steps before leaping with both feet.


Thanks in advance.

Dan
 

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I started with the edelbrock pro flow system then updated to the holley commander 950 pro system. Now I am using the FAST XFI system.

My suggestion is to skip the TBI setup completely and go directly to some type of multi-port injection. I am not sure why your cam would not work... how much vacuum does it have at idle? Most systems seem to want at least 10". I have run two mechanical roller setups and now have a hyd roller setup with no problems.

The system and support you get will probably determine how much you like fuel injection. Poor designed systems with poor tech support = headache and frustration.

I bought my XFI setup from Hartline performance, Cal got me a startup program and helped me tune it from there. For me the installation was simple and no problem at all, each plug is clearly labeled. Just install the intake, throttle body and sensors. Make the fuel system mods and plug everything together. Tuning is a little overwhelming at first if you have never done it, just need some patience and good tech support at first.

The options are dependent on the system. To me... holley is an OK system, however it is really getting out dated. Edelbrock was rock solid, just a basic system w/o many options, however they have updated their stuff.

Tg
 

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I have the edelbrock pro-flo. Not a bad system. They take all the guess work outta it if you go with their heads and cam. JR
 

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Discussion Starter #9
does anyone else have efi vs carb comparison?

looking for info on throttle response and part throttle driveability
 

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does anyone else have efi vs carb comparison?

looking for info on throttle response and part throttle driveability
Im solly, that was you original question too. Maybe not answered specifically cause when a guy swaps out a carb for EFI on the same engine there are so many other things that get swapped out too its just not a good comparison.

But I have driven both carbed 350s and EFI 350s in a similar car and my observation...

FI, snap throttle response. Never driven a carbed car with exacting throttle response. And the larger the carb the worse it gets. Off idle, FI is right on, mid RPM cruising, tap the throttle, its on the juice now. Get a small enough carb though and cruise response is pretty good, people tend to over carb their STREET engines.

And dont forget about the electronics. You dont have any mechanical advance with FI. Computer controls the advance. I look at mechanical advance like I do a carb. Is a slow progression to where you want to be when you stab the throttle.

Electronically controlled fuel metering and spark is faster than mechanically controlled spark and fuel. Oh man, waiting for the volume of air to increase (RPMs) to draw fuel on a carb. Stab the throttle, low vacuum, wait for Rs to come up to pull more fuel, a carb. LOL And it does happen so much faster than I just wrote, but thats the simple idea of it.

Prolly works good in a tractor, but for a modern car I just dont see it. OH wait!!! I was only talking about a street car. 1/4 mile car, carbs still have a place. Why?? Cost.. For 1/4 mile its about dumping fuel. You can dump large amounts or fuel for less money than you can with FI. But there are FI systems that can dump as much fuel as you want, money, money....

More?? Fuel economy. Oh, and you can run a higher compression ratio also, street car. I could go on and on.

Why a carb??? Cost, plain and simple. JR
 

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Discussion Starter #11
Im solly, that was you original question too. Maybe not answered specifically cause when a guy swaps out a carb for EFI on the same engine there are so many other things that get swapped out too its just not a good comparison.

But I have driven both carbed 350s and EFI 350s in a similar car and my observation...

FI, snap throttle response. Never driven a carbed car with exacting throttle response. And the larger the carb the worse it gets. Off idle, FI is right on, mid RPM cruising, tap the throttle, its on the juice now. Get a small enough carb though and cruise response is pretty good, people tend to over carb their STREET engines.

And dont forget about the electronics. You dont have any mechanical advance with FI. Computer controls the advance. I look at mechanical advance like I do a carb. Is a slow progression to where you want to be when you stab the throttle.

Electronically controlled fuel metering and spark is faster than mechanically controlled spark and fuel. Oh man, waiting for the volume of air to increase (RPMs) to draw fuel on a carb. Stab the throttle, low vacuum, wait for Rs to come up to pull more fuel, a carb. LOL And it does happen so much faster than I just wrote, but thats the simple idea of it.

Prolly works good in a tractor, but for a modern car I just dont see it. OH wait!!! I was only talking about a street car. 1/4 mile car, carbs still have a place. Why?? Cost.. For 1/4 mile its about dumping fuel. You can dump large amounts or fuel for less money than you can with FI. But there are FI systems that can dump as much fuel as you want, money, money....

More?? Fuel economy. Oh, and you can run a higher compression ratio also, street car. I could go on and on.

Why a carb??? Cost, plain and simple. JR
thanks for the informative reply.

unfortunately Ive only driven a vacuum secondary carb but I would imagine with a double pumper throttle response would be pretty darn good with dual squirters for those low vacuum situations.

Ive put the carb in the box and Im going to forge ahead with the EFI system.
 

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I don't think you will regret it... just allow time to learn the tuning process. Some of the initial problems you might run into are:

*Surging idle (normally lean condition)
*Bog on acceleration
*Hot/Cold start conditions

Just have patience and ask for help, if you go with MS, they have a GREAT forum.

Tg
 

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I would be the last person to sell a carburator short. A well tuned carburator on a well thought out engine combination is a thing of beauty. Get the distributor curve right, pick the right convertor & gears, and you are in for great driving experience.

EFI does the same thing that a carburator and mech/vac distributor does. The difference is, (on a closed loop system) it can be more precisely controlled/regulated. EFI offers the 'potential' for better driveability, better fuel economy, and better performance. Just like with a carburetor, it is largely dependent on choosing the right combination of parts.

What I like about EFI is that it is always ready to do it's thing at the turn of the key. (Regardless of temperature or weather conditions.) With carburators, I was always tweaking and tuning before a trip to the dragstrip. With EFI, once it's right, no extra tweaking is required. It even adjusts for altitude changes.
 

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I think these guys have covered it pretty well, but if I can toss in my $.02

Think of getting in your Nova. Carb'd. Fast. Probably cold natured, needs a little help to warm up on a cold morning, or maybe on every morning even. Might have to pump the throttle a time or two before turning the key to get it to start quickly. Might have to hold the thottle a bit after it fires to keep it running if it's really cold. Once warm, throttle response is fairly good, but could probably be a bit more crisp. If it's more of a race car than a street car, you likely find you need some fine tuning for differing ambient conditions at different tracks due to elevation and weather conditions.

Now hop in your '08 full size truck. It's a 15degF morning, but you turn the key and it fires right up. You can take off immediately if you want to and it's not going to complain for an instant. We all know that's not ideal for the motor, but for arguments sake the motor is running well enough when it's cold that you 'could' do it. Throttle response is snappy. You could take this thing to a thousand different race tracks (if you like to race your truck) and it doesn't give a crap about elevation or weather conditions. More accurately, it does care, but it took care of it for you and made the needed adjustments. You might still run a hair slower or faster due to conditions, but you don't run dangerously lean due to conditions, your tune doesn't dramatically change because the EMS recognized the weather changes and compensated for it.

Now combine the two. Your hot rod does everything your truck does, but it's made to RUN. When you lay into it it makes pretty much all the power it ever did. Sometimes a hair more as you're able to get the tune spot on in areas where you previously had to compromise with the carb. Sometimes a hair less if the EFI manifold you used isn't as efficient at a certain RPM as the carb intake was. But the bottom line is EFI let's you put the Air/Fuel ratio EXACTLY where you want it under all conditions.

So all the power is there when you're on it. And driven easier it's got the best manners it could possibly have. It takes a little bit more to set it up, but properly setup it's very nice.
 

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If it's more of a race car than a street car, you likely find you need some fine tuning for differing ambient conditions at different tracks due to elevation and weather conditions.
Oh yeah, I forgot one, elevation changes. I seemed to have forgotten about that. Kinda diff but I have an old motorhome, carbed 400. Im at sea level, when I go to about 2500ft I REALLY notice it. Like Im driving with the brakes on. EFI doesnt suffer there. JR
 

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Discussion Starter #16
But the bottom line is EFI let's you put the Air/Fuel ratio EXACTLY where you want it under all conditions.
this is exactly why Ive decided to convert. the ability to change my fuel ratio on the fly and the ability to design and tweak my own custom ignition curve is what I find extremely exciting.
 
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