Do 8 Stack EFI or Weber Carbs Run Good On The Street?

[Karl Bebout]

I've been running Weber 44 IDFs on my tiny SBF, I've put 14,000 miles on in 15 months of driving and once they were set up, have had no problems. Easy starting, great response, and a lot oh "holy sheetz" when the hood is open and people take a look. I've had it at sea level and at 10,000ft. elevation. Did notice less power at elevation, but not enough to worry me. Just had to be a bit more judicious in my passing decisions. That being said, I've never had stack injection (except the Crower mechanical on a C Altered 57 CHEVY, 45 years ago) I'd think the electronic stack would be the best of both worlds with its tune-ability and its uber cool appearance.

[fordracing65]

A lot of guys with big blocks the 48 Ida is too small. I think the efi stack guys run bigger trumpets to get big power.

[Gaz64]

Originally Posted by fordracing65

A lot of guys with big blocks the 48 Ida is too small. I think the efi stack guys run bigger trumpets to get big power.

Yes the 48 is too small, but you can buy 58 or 60 IDAs from Gene Berg.

[Dimis]

Originally Posted by Gaz64

Yes the 48 is too small, but you can buy 58 or 60 IDAs from Gene Berg.

Hey Gaz,

Is it not true that:
48s are suitably sized for street on an FE, even a big bore FE.
The limitation here however is that 48s will choke the engine starving it of air at high rpm. Therefore they are at their best in midrange power delivery, street flowing circuit type course use, as opposed to drag racing or oval track.
The 58s from Gene Berg that cost a motza (and are out of stock) shift the power to a higher rpm range, and intact could adversely affect street driving in the common low to middle band experienced in street driving, by reducing air velocity.

Or is my humble research ill informed?
Are you able to kindly clarify this?

On another note: I believe webers ARE workable for a street engine. EFI or otherwise. The only limitation is the the time energy money and inclination one has to invest it them. For a car that's driven as infrequently as most Cobras are, I've placed them in the who could be farked category, for now. As I'm unlikely to drive them often enough and far enough to resolve and sort the issues.
That said I still do find myself tempted. :

Thanks in advance.

[Gaz64]

Originally Posted by Dimis

Hey Gaz,

Is it not true that:
48s are suitably sized for street on an FE, even a big bore FE.
The limitation here however is that 48s will choke the engine starving it of air at high rpm. Therefore they are at their best in midrange power delivery, street flowing circuit type course use, as opposed to drag racing or oval track.
The 58s from Gene Berg that cost a motza (and are out of stock) shift the power to a higher rpm range, and intact could adversely affect street driving in the common low to middle band experienced in street driving, by reducing air velocity.

Or is my humble research ill informed?
Are you able to kindly clarify this?

On another note: I believe webers ARE workable for a street engine. EFI or otherwise. The only limitation is the the time energy money and inclination one has to invest it them. For a car that's driven as infrequently as most Cobras are, I've placed them in the who could be farked category, for now. As I'm unlikely to drive them often enough and far enough to resolve and sort the issues.
That said I still do find myself tempted. :

Thanks in advance.

Yes all true, up to a point.

I agree the 48s are good for mild to slight aggressive street manners, but on a big engine will limit top end.

Here is some beautiful 58s of a fellow member:

58 mm Berg IDA Carbs--Here They Are

Gary

[Gary(SF)]

Originally Posted by Dimis

The limitation here however is that 48s will choke the engine starving it of air at high rpm.

I have heard that before, but my 521 with Weber 48 IDA's pulls strong to the redline. Go figure.

[FUNFER2]

Can a cam be too big, that you have little vacuum, meaning do we need vacuum to run the system properly ?

Are there any other specs of the engine that will screw up the working of this type of injection, thus the engine will not run well ?

Any special engine build needs for this injection ?

[Dimis]

Originally Posted by Gary(SF)

I have heard that before, but my 521 with Weber 48 IDA's pulls strong to the redline. Go figure.

Great to know! Its always perplexed me how 8 trumpets theoretically can't supply enough air for each cylinder when compared to a single carb

If you don't mind kindly sharing please:
What are your cam specs?
Hydraulic or solid rollers?
and Rpm red line?

Thx

Originally Posted by FUNFER2

Can a cam be too big, that you have little vacuum, meaning do we need vacuum to run the system properly ?

Are there any other specs of the engine that will screw up the working of this type of injection, thus the engine will not run well ?

Any special engine build needs for this injection ?

My understanding is a wide lsa is required to limit reversion, and the more vacuum the better the end result. I'm no expert. I defer to greater minds for info on this.

[moore_rb]

Originally Posted by FUNFER2

Can a cam be too big, that you have little vacuum, meaning do we need vacuum to run the system properly ?

With Carbs (Webers) - Yes. With Throttle Body injection (TBI) - Yes.
With Multi-port injection (MPI) - It depends on the computer.

Speed density MPI (Also called "open loop") systems use manifold absolute pressure (MAP) as the primary air measuring device for calculating the injector pulse needed to achieve the correct A/F ratio for any particular throttle position; and cams with a lot of overlap will cause a lot of instability in the MAP, the same way they wreak havoc with vacuum. This makes the MAP sensor send erratic signals to the computer, making the computer think it has to make hundreds of adjustments per second. So tuning the idle and part throttle settings in a speed density controller can take lots of time, and lots of trial and error on the dyno, when you throw a big cam into the mix.

BTW- all the current crop of 8-stack style EFI systems out there today are speed density MPI designs, and so they will require this more sensitive tuning, (and probably more time on the dyno to accomplish it)

The other style of MPI is MAF/MAP "combination" (also called "dual circuit", "sequential" or "closed loop") systems. These systems use MAP for calibrating the WOT A/F ratio, and they use Mass Air Flow (MAF) to calibrate the idle and cruise throttle positions.

MAF systems are, hands down, the BEST EFI design for running with a large cam (especially in a street driven car); because the cam would have to be REALLY extreme to influence the air flow in front of the throttle valves.

The reason none of the 8-stack EFI systems use a closed loop controller is that there is no practical/feasible way to incorporate a mass airflow sensor into each air horn (yet), nor is there a controller out there that can aggregate 8 MAF Sensor signals into a single value that the computer can use. (This is what Olddog and I were talking about in the other thread you opened up about the Ebay manifold you had found)

Originally Posted by FUNFER2

Are there any other specs of the engine that will screw up the working of this type of injection, thus the engine will not run well ?

Any special engine build needs for this injection ?

Nah- the cam profile (overlap most specifically) is really about it. Tight lobe separation angles (below 112 degrees), and mega long durations (above about 230 at .050) are where you are going to start running into potential part-throttle hassles with a MAP sensor system (These values are just yardsticks, not hard values)...

[Ron61]

I have the Mega Squirt fuel injection on my Coupe and like it. I did have the power cut back on the engine when I quit racing it and it works very well on the street and in our mountain roads.

Ron

[redmt]

Originally Posted by Ron61

I have the Mega Squirt fuel injection on my Coupe and like it. I did have the power cut back on the engine when I quit racing it and it works very well on the street and in our mountain roads.

Ron

I don't mean to correct Ron but he has a TWM Borla setup with the Mega Squirt ECU. The engine was built by me and the M S system was setup and tuned by Brian Rebello of Rebello Racing. It's an easy system to check the tune if you have the correct and original program but you need to take it back to whomever tuned it, or have them rewrite a new program and send it to you if you want to do anything but run the fuel pressure up or down.