[projectfolly]

This subject may have been covered elsewhere, so sorry if its a rehash.
I've been considering a FAST EZ EFI system for my 455. As I understand things the throttle body is a square bore. I'm currently running a stock intake with a q-jet which obviously is spread bore. I don't want to run a square bore to spread bore adaptor so it looks like an intake swap is the solution.
The question is, which intake would be the best?
The Edelbrock Performer and Performer RPM both have a dual carb pattern which would work, however I currently have a Edelbrock P4B square bore with (I think) the wide runners. Given the narrower plenum dimensions, would this restrict power or work well for the square bore?
Anyone have experience with this?
Any input would be appreciated.

[Mr_GTO]

I don't think finding a used Performer or RPM is going to break your budget and they will provide better airflow than your P4B.

[Engo]

A single plane intake would be a lot better both for flow and for placement of injectors.
There is no need for a dual plane intake on a EFI engine.
I would look for T2.

[Mr_GTO]

Originally Posted by Engo

A single plane intake would be a lot better both for flow and for placement of injectors.
There is no need for a dual plane intake on a EFI engine.
I would look for T2.

http://www.fuelairspark.com/ezefi/

That's the system he's going with. Not a port system.

[Engo]

Originally Posted by Mr_GTO

http://www.fuelairspark.com/ezefi/

That's the system he's going with. Not a port system.

I does not matter if it is port injected or not.

There is no advantage for a dual plane intake in a fuel injected engine. Only disadvantages...compared to a single plane intake.

(BTW. It looks like that system also has a port injection option)

[Skip Fix]

I think a TBI system with a single plane would still suffer the same potential issues as a carbed single plane as a decreased low end compared to a dual plane. But a single plane does allow the upgrade to port injection for the future. Maybe a Torker II EFI manifold with the injector bungs plugged and the TBI then future upgrade to port injection.

Since we are in the boost section if boost is used the single plane would be a better deal as fewer issues with low end

[Engo]

Originally Posted by Skip Fix

I think a TBI system with a single plane would still suffer the same potential issues as a carbed single plane as a decreased low end compared to a dual plane. But a single plane does allow the upgrade to port injection for the future. Maybe a Torker II EFI manifold with the injector bungs plugged and the TBI then future upgrade to port injection.

Since we are in the boost section if boost is used the single plane would be a better deal as fewer issues with low end

You need to think harder about this Skip.

The fuel is injected. There is no need for a vacum signal like there is for a carburator.

[projectfolly]

Thanks for the input guys.
Sorry, I wasn’t more specific, the F.A.S.T. EZ system I was referring to is the throttle body version as Mr. GTO had surmised.
Sounds like in the case of throttle body injection, the intake choice may not be as critical as I thought.

[Skip Fix]

Yes but Throttle Body pod injects the fuel at the same level as a carb and does needs some vacuum to get the fuel mixture to travel in continued suspension down the runners compared to port injection. The more imnportant issue is runner length,it still comes into play even with EFI -look at SBC Tuned port vs LT-1 runners vs LS runners. TPI longer runners have a better bottom end than LT-1 short runners. Most dual planes have longer runners than single planes so you have runner length chages depending on the intake so you still get that into the peak rpm equation. Pretty sure the first TBI GM intakes were dual plane also.

[77HANDMEDOWN]

Skip is right. It has to do with runner length. Modern direct injection engines, even diesels, have variable runners.

[Engo]

Originally Posted by 77HANDMEDOWN

Skip is right. It has to do with runner length. Modern direct injection engines, even diesels, have variable runners.

What do you want to say with this statement?
Do you claim that any dual plane intake would generate more low rpm torque than any single plane intake on a tbi-engine?

[Engo]

Originally Posted by Skip Fix

Yes but Throttle Body pod injects the fuel at the same level as a carb and does needs some vacuum to get the fuel mixture to travel in continued suspension down the runners compared to port injection. The more imnportant issue is runner length,it still comes into play even with EFI -look at SBC Tuned port vs LT-1 runners vs LS runners. TPI longer runners have a better bottom end than LT-1 short runners. Most dual planes have longer runners than single planes so you have runner length chages depending on the intake so you still get that into the peak rpm equation. Pretty sure the first TBI GM intakes were dual plane also.

Vacuum cannot move anything out of the plenum! Vacuum is static!

Suction from a cylinder intake runner during the induction phase can though, and that is something different.

You are right about runner lenght being important in a true fuel injection design manifold. But that again has nothing to do with dual plane carburator manifold design.

Please explain you theory about a single plane intake giving a decreased amount of torque compared to a dual plane intake, in a fuel injected engine, as you said in previous post.

Please also explain your theory about the injector placement and the the need for vaccum as you said.

You guys that think Skip is on to something might want to look at some engines with intakes that is designed with injectors. Many have injectors that spray straight into the plenum! Others have them at the start of runner or close to the valve.

[Fishin2Deep4U]

Its about velocity at low rpm and a wall wetting component. At low rpm, the fuel can fall out of suspension wetting everything in its path. at higher rpm this is less of an issue.

Bottom end torque and feel will suffer from a tbi with a dual plane. The same rules apply just as out does for a carb. The fact that a computer sets the rate of fuel vs vacuum through a carb has zero effect other than ease of fuel curve adjustment. If this were a high rpm engine with little emphasis on bottom end you could even place the injectors outside the plenum area entirely.

Stock or performer for tbi/carb steer apps. Single plane for high rpm carb our port efi.

Dave

[Region Warrior]

Have to agree with Skip and 77HMD.
Is it street, street/strip, or strip only?
Whats the engines power band?

[projectfolly]

Originally Posted by Region Warrior

Have to agree with Skip and 77HMD.
Is it street, street/strip, or strip only?
Whats the engines power band?

Its a street car - '68 Firebird.

On the dyno, peak TQ was 542 @ 3400 rpm. Peak HP was 435 @ 5200 rpm.

The engine is a 455 with '71 #96 heads, stock intake, late 70s Q jet, through ram air manifolds with 2 1/4 outlets. Not a real radical engine as I wanted a smooth idle, tractable behavior and a good vacuum signal.

[Engo]

Originally Posted by Fishin2Deep4U

Its about velocity at low rpm and a wall wetting component. At low rpm, the fuel can fall out of suspension wetting everything in its path. at higher rpm this is less of an issue.
Dave

This reasoning apply to carburetor engines first hand. Of course, wall wetting can happen to a fuel injected engine also, but that is an event that can happen regardless of what type of intake the engine has.

Again, a dual plane (and single plane) intake manifold were designed for carburetors. The fact that OEM engines that have TBI uses the same intake as carburetor engiens does not change the design criteria of the manifold. I venture to guess that it has more to do with bean counting on part of the OEMs.

Originally Posted by Fishin2Deep4U

Bottom end torque and feel will suffer from a tbi with a dual plane.

Agreed.

Originally Posted by Fishin2Deep4U

The fact that a computer sets the rate of fuel vs vacuum through a carb has zero effect other than ease of fuel curve adjustment. If this were a high rpm engine with little emphasis on bottom end you could even place the injectors outside the plenum area entirely.

Actually, the fact is that the computer primarily uses RPM and LOAD to calculate the fuel needed (assuming speed density strategy). Of course CT and MAT also goes into the equation in most good systems.
And to add to the statement of fact, if the engine runs in Closed Loop with a wide band O2 sensor it will compensate for ill effects like wall wetting of the intake tract and other stuff that might affect the fuel on its way to the combustion chamber.
And lets also face this fact, it is what happens in the combustion chamber that counts when we talk about power&torque.

Originally Posted by Fishin2Deep4U

Stock or performer for tbi/carb steer apps. Single plane for high rpm carb our port efi.

That statement is valid for carburated engines but not för fuel injected engines.

[Engo]

Originally Posted by projectfolly

This subject may have been covered elsewhere, so sorry if its a rehash.
I've been considering a FAST EZ EFI system for my 455. As I understand things the throttle body is a square bore. I'm currently running a stock intake with a q-jet which obviously is spread bore. I don't want to run a square bore to spread bore adaptor so it looks like an intake swap is the solution.
The question is, which intake would be the best?
The Edelbrock Performer and Performer RPM both have a dual carb pattern which would work, however I currently have a Edelbrock P4B square bore with (I think) the wide runners. Given the narrower plenum dimensions, would this restrict power or work well for the square bore?
Anyone have experience with this?
Any input would be appreciated.

If you are going to spend the cash for a EFI system there are better systems out there than a TBI style injection.Spraying the fuel into a plenum (be it into two plenums such as a dual plane intake OR into one plenum such as a single plane intake) can or will lead to different negatives as pointed out above. Such as distribution issues and wall wetting etc. The point is, they were NOT DESIGNED FOR fuel injection.

ALL intakes available for our pontiac engines are designed for carburators not for fuel injection.

If you want a intake designed for fuel injection you will have to have one custom made.

If you still want to use a carburator intake for your fuel injection, it is best to look for one that has as equal length and size runners as possible.
A Torker 2 intake that I suggested in my first post is a very good choice (it actually also works very well even with carburators)
And it is fairly easy to have a good location of the injectors on a T2.

[77HANDMEDOWN]

So Engo. It seems like you are saying that efi or carb can change the torque curve and power band of the engine from the fueling swap itself. I have heard this before that the two will have the opposite effects, one shifting the power band down and the other shifting the power band up. I have always thought people were just confused and dismissed this.

School me... seriously no disrespect. I am open to learn something.

How does simply changing from a carb to tbi or multiport change the effects of reversion and intake resonance? Long skinny runners = air velocity and torque and larger squaty runner favor higher rpm power. Generally speaking. Late model OEM intakes with 2 sets of runners have long narrow runners for low rpm and switch to large fat ones for high end hp which would go against what you are saying.

[Skip Fix]

"Please explain you theory about a single plane intake giving a decreased amount of torque compared to a dual plane intake, in a fuel injected engine, as you said in previous post."

Again runner length measure a RPM runner length then go measure a Torker,Tomahawk,Victor. The single planes will be shorter-why the generally have a higher TQ peak even with a carb and often lower TQ on the bottom end. My RAIV 400 we dynoed with a massaged HO, Massaged T1 and a T2. All three had the same peak HP, both single planes had a much higher TQ peak and when swapped in the car had a much softer bottom end even with a 4500 stall. Yes a carb but runner length was the variable.

The EZ TBI is basically a cross between a carb and injectors-using a spray to inject at the top end but still relying on some vaccum/suction (for most the vacuum produced in an engine we think of is suction produced by the cylinder pull and dynamic) to get the fuel down those runners-otherwise it would just puddle under the TB unit, and mixture controlled by computer vs jets/PV.

I agree multiport injection is a better ideal but he is asking about a TB system.

With closer to port injestion reversion is not as big a factor as the fuel is being introduced deepr in the tract so little chance for fuel standoff above a carb/TBI where it is at the top of the tract. Still possible but just back up the runners. Reversion is often as much from exhaust issues. In fact the RAIV had bad reversion until I went to a smaller header and more intake duration on the cam-it had 85% E/I and on that it would flow 90% on the exhaust backwards.

Runner length affects the resonance and TQ rpm peak-lots of various formulas for that on the intake and exhaust side. GM went to a shorter runner on the LT-1s over the TPI motors and it affected their TQ/HP curve as you would expect.

[Engo]

Originally Posted by Skip Fix

Again runner length measure a RPM runner length then go measure a Torker,Tomahawk,Victor. The single planes will be shorter-why the generally have a higher TQ peak even with a carb and often lower TQ on the bottom end. My RAIV 400 we dynoed with a massaged HO, Massaged T1 and a T2. All three had the same peak HP, both single planes had a much higher TQ peak and when swapped in the car had a much softer bottom end even with a 4500 stall. Yes a carb but runner length was the variable.

I understand what you are saying and agree with it as far as it concerns a carburated engine on a very general level.
You are however over simplifying the comparison between different single plane intake (and other intakes unspecified however).
Generally, runner lenght is equally important to a carburated and a injected engine, of course.But that is not the issue discussed by me.

Originally Posted by Skip Fix

The EZ TBI is basically a cross between a carb and injectors-using a spray to inject at the top end but still relying on some vaccum/suction (for most the vacuum produced in an engine we think of is suction produced by the cylinder pull and dynamic) to get the fuel down those runners-otherwise it would just puddle under the TB unit, and mixture controlled by computer vs jets/PV.

The fuel are going down the runners regardless if it was introduced thru a carb booster or an injector.
Why would the engine produce more torque with a (generic) dual plane intake than a (generic) single plane intake in a tbi-engine? i.e. why would the tbi act exactly the same as a carburator? (remember the tbi does not need a vacuum signal to pull fuel from the booster as a carburator would)

Originally Posted by Skip Fix

With closer to port injestion reversion is not as big a factor as the fuel is being introduced deepr in the tract so little chance for fuel standoff above a carb/TBI where it is at the top of the tract. Still possible but just back up the runners. Reversion is often as much from exhaust issues. In fact the RAIV had bad reversion until I went to a smaller header and more intake duration on the cam-it had 85% E/I and on that it would flow 90% on the exhaust backwards.

Reversion ( if it occurs) is, for the most part, the same problem in a carburated and fuel injected engine. But I don´t see what You say is the problem between the two intake manifold designs. IF reversion is a problem, you will have it in a dual plane intake manifold engine as well as in a single plane manifold engine.

Originally Posted by Skip Fix

Runner length affects the resonance and TQ rpm peak-lots of various formulas for that on the intake and exhaust side. GM went to a shorter runner on the LT-1s over the TPI motors and it affected their TQ/HP curve as you would expect.

I agree 100%.