47-55.1 EFI vs TPI

[mobileortho]

So... as i'm going through my "re-do" I'm finding more and more stuff to do. What was to be just shortening the bed has snowballed! I'm wanting to simplify things a bit and eliminate a bunch wires and go for the old school carb look and have been considering the Holly Sniper to replace the TPI. From what I'm seeing it looks pretty straight forward and is a much cleaner setup.

For those using it, how do you like it? (or the FiTech Fast EFI, ect) For reference, its a base 350 (10067353) with vortec heads.

[jwhotrod]

if you have a tune port motor there is nothing wrong with that setup baring any engine problems. Holley also makes a cpu/wiring harness setup for the TPI. ive had a tpi setup on a ZZ4 crate motor in my 34 chevyfor 15 years runs strong, added 25-30 hp to the already potent engine. That said I have friends that have converted their zz4 to a sniper and are very satisfied with that setup as well. I would caution you that whatever you to put a tank mounted pump in your setup, they are quiet and will last a lot longer than external pumps.

[mongocanfly]

Before considering a sniper you need to read up on all the issues that come with it..
Sweetk30 has documented his issues well ...as have others...
edlebrock proflow may be a better choice if that's what you want..

[mr48chev]

Why would you want to consider going backwards when it comes to performance? Those bolt on a 4 barrel intake FI units are basically 1976 Cadillac Seville technology.
It just flat doesn't make sense to take a tuned port injection off and retrograde to a throttle body injection.

Just as it makes less sense to take a Fi unit off and put an antique carb on to "'look cool". I've replaced a Fi unit with a carb simply because I was too broke to fix the FI unit on my wife's 76 Seville and put a carb I had on it so she could drive it to work. I lost three mpg in the process.

Do what you want to but spending probably 1500 bucks when you are done to take something that works great off to put something that you "think looks cooler" but doesn't perform as well doesn't make much sense in the real world.

[mobileortho]

EFI has come a looooong way since 76. And, as far as performance goes, plenty of comparisons out that show that a carb makes more peak hp over TPI, but the TPI shines when it comes to low end torq & drivability. The newer EFI units to me offer the best of both worlds plus it doesn't require sending in a chip the be reflashed when changing cams and there's not mile after mile of wiring.

[jwhotrod]

I was trying to say with minimal investment on your part, since you already have the TPI if it was me, I would by a Holley HP ecm and a TPI harness to connect it to your injectors and sensors and get self learning capability, no reflash needed to change configurations and the reason GM put that TPI unit on the camaros and corvettes was to add horsepower and torque without having to do engine upgrades. they took a basic 250HP engine and added 35-50 HP and lots of torque for minimal investment, I love what the TPI did to my ZZ4.

[1project2many]

Lots to consider if you want a detailed discussion. The TPI configuration with long runners and small diameter tubes provides a bunch of low end torque. This system performs well when combined with numerically low gears and/or overdrive transmission. If you plan to run at 1400-1700 RPM on the highway or love doing burnouts with a lower hp engine then TPI is a nice choice.

TBI like the Sniper or a GM system can provide more consistent fuel delivery than a carburetor. Your choice of intake manifold really determines whether or not the TBI makes power where you need it. If you replace the TPI on a stock engine with a short runner, small plenum production-type manifold with TBI it's possible you will feel the vehicle has lost performance off the line.

Tuning an efi system can be a challenge. Aftermarket systems often have features built in to make tuning easier. They don't always work as expected and you may need professional assistance. Tuning a GM computer can be more challenging. Most of the work to figure out what to change falls on the owner or tuner. Many folks figure it out but there is a steep learning curve. Some folks just offer to pay to have it done.

The age and power of the computer makes a difference in how well the vehicle responds. For example older TPI systems with a mass air flow sensor will benefit to an upgrade from a 90-91 Corvette or 91 Camaro ecm. TBI systems from late '80s to early '90s cars and trucks can benefit from an upgrade to the 94-95 GM Pickup truck pcm. These changes require reworking the wire harness and can be intimidating to some people. Aftermarket systems may or may not have more powerful and more reliable computers. Aftermarket companies may not have the resources available to spend millions of $$ on research, development, and testing of their controller.

I wish the answer was simple, but all those words really boil down to "It depends." Good luck.

[mobileortho]

Originally Posted by 1project2many

Lots to consider if you want a detailed discussion. The TPI configuration with long runners and small diameter tubes provides a bunch of low end torque. This system performs well when combined with numerically low gears and/or overdrive transmission. If you plan to run at 1400-1700 RPM on the highway or love doing burnouts with a lower hp engine then TPI is a nice choice.

TBI like the Sniper or a GM system can provide more consistent fuel delivery than a carburetor. Your choice of intake manifold really determines whether or not the TBI makes power where you need it. If you replace the TPI on a stock engine with a short runner, small plenum production-type manifold with TBI it's possible you will feel the vehicle has lost performance off the line.

Tuning an efi system can be a challenge. Aftermarket systems often have features built in to make tuning easier. They don't always work as expected and you may need professional assistance. Tuning a GM computer can be more challenging. Most of the work to figure out what to change falls on the owner or tuner. Many folks figure it out but there is a steep learning curve. Some folks just offer to pay to have it done.

The age and power of the computer makes a difference in how well the vehicle responds. For example older TPI systems with a mass air flow sensor will benefit to an upgrade from a 90-91 Corvette or 91 Camaro ecm. TBI systems from late '80s to early '90s cars and trucks can benefit from an upgrade to the 94-95 GM Pickup truck pcm. These changes require reworking the wire harness and can be intimidating to some people. Aftermarket systems may or may not have more powerful and more reliable computers. Aftermarket companies may not have the resources available to spend millions of $$ on research, development, and testing of their controller.

I wish the answer was simple, but all those words really boil down to "It depends." Good luck.

Great info! Thanks!