I've never seen a hard ad fast rule about it, but considering the placement in the Mustangs the duct from the MAF to the TB is about 18" long and has a 90 degree bend in it.  I would suppose if it was too close to the TB it could pick up the turbulence from opening and closing the throttle blade. 

Probably within inches on a straight run.

My thoughts are to use a 4150/4160 base as a throttle body with the MAF above it a couple of inches going into an air filter housing.

Or into a typical single blade throttle body with the MAF in same position as above.

This is to stay under a stock hood.

The Holley throttle blades are not going to seal off airflow as well as the machined butterfly of a factory throttle body, which may adversely affect idle speed motor operation.
Let us know how this works out. It is great to see experimentation.
I always wondered how a sidedraft weber would work on a 5.0 efi intake. Probably not well…

The BIG issue there is programming.  No idea what they did for the MAF transfer tables, etc.  IMO, if you are going that custom, and are going to need to tune it anyway why not just go SD and not have to worry about the MAF?  This is why almost every aftermarket system is SD. 

One thing I can say for certain is that you must keep the MAF away from turbulence.  I "fixed" a lot of idle problems on Fox bodies by simply shielding an exposed air filter from the air currents created by the fan.  The car would sound like it had a cam that 6sally6 would like before. 
 

RTM wrote:

TKOPerformance wrote:

The BIG issue there is programming.  No idea what they did for the MAF transfer tables, etc.  IMO, if you are going that custom, and are going to need to tune it anyway why not just go SD and not have to worry about the MAF?  This is why almost every aftermarket system is SD. 

One thing I can say for certain is that you must keep the MAF away from turbulence.  I "fixed" a lot of idle problems on Fox bodies by simply shielding an exposed air filter from the air currents created by the fan.  The car would sound like it had a cam that 6sally6 would like before. 
 

 
Forgive my lack of knowledge on this but doesn’t the MAF system have greater tuning abilities than the SD or has things changed over the years? I recall on the ford SD systems you couldn’t run to big of a cam or it would run like crap. More curious than anything.

The idea is that an MAF based system self learns and self adjusts better than SD.  SD can't do much once you improve airflow in and out by more than 10%.  MAF in theory can adjust itself until you reach points which are outside the bounds of the lookup tables in the ECU.  In practice though there is still a lot of benefit to tuning via programming an MAF system.  So if you are already going to be doing that you lose nothing by simply ditching the MAF and going to SD, and you gain simplicity.  Properly dialed in there is no difference in power between MAF and SD.  I watched an episode of Engine Masters where they found no difference between batch fire and sequential EFI in terms of power.  From a lot of the testing I've seen I've come to think a lot of the "improvement" in EFI over the years was done for better fuel economy, emissions, and diagnostics.  Not that those are bad things, but in an application where emissions compliance is a non issue you should weigh the benefit of a couple percent better fuel economy and somewhat better diagnostics with the added complexity of the system. 
 

Sump'in like this LT !??
6sal6

Last edited by 6sally6 (11/20/2023 6:02 PM)

I have always subscribed to the KISS principle. Just give me a carb that works. All that EFI stuff is too compulcated for my old brain.....

In a non stock application I would avoid anything with OBD2.  IMO the benefit of the EECIV system is that its pretty bare bones, yet works extremely well.  I would call it the best factory EFI ever from a hot rodding standpoint. 

If it don't 'cut-up' when itz idling ....you'll be destined to never smile when ya drive it !
( I still get "excited" when I pull up next to a bunch of cars at a traffic light...the 'echo' off the other cars never gets old !!sorry)
6sal6

You still need to be somewhat careful on your cam selection with MAF, particularly when you look at the LSA and overlap.  EFI cams are always ground on a wider LSA (112-114), and they tend to favor higher lift numbers and lower duration to reduce overlap.

The biggest advantage to sequential EFI in a performance application comes when you are running nitrous or boost.  The ability to trim the fueling in each cylinder doesn't really make any more power, but you can keep 1 or 2 holes from going lean which may save the engine from a catastrophic failure. 
 

Nos681 wrote:

Raymond…my understanding when I look at the wiring diagrams and schematics is the “injectors” fire in a batch not the ignition system. Plugs fire one at a time just like points.

Ford also had two types of speed density.
Sequential and batch.
This controls the injectors and spark is distributed via the distributor as triggered by PIP.

You are 100% correct, the plugs definitely fire per cylinder and yes Ford did make the transition (if you're speaking about Fox Mustangs) to a sequential SD system then MAF. That's why swapping an SD Mustang to MAF is so darn easy. However their trucks remained batch fire until they went MAF and why you have to change an SD truck's injector harness if you're swapping to a MAF or aftermarket setup to be sequential. I am sure I am being pedantic, but it's worth pointing out.

With regards to sequential and fully sequential, I should have been more clear on when I was speaking about aftermarket or modern systems vs the 90's tech Fox stuff The PiP signal is OK for early model sequential, but you really need both a cam and a crank sensor to be truly full sequential. Holley kind of "cheats" with their dual sync distributors, but again you gain real precision with a proper crank and cam sensor.

I feel bad that I've contributed to a big time thread derail, I'll be quiet now!
 

The issue with a factory SD system is it is tuned for the engine it was on from the factory.  Its is highly reliant on lookup tables, which were created based on the airflow ability of the engine it came on.  Now, if you can tune it you just change the lookup tables to work with your new engine.  You would need a way to datalog A/F ratios and then adjust the tables accordingly.  They have some ability to learn, but its not great.  A decent performance cam, even an EFI grind is going to give it fits.  You'll be rich at idle and lean at WOT, basically a recipe for disaster. 

If you don't want to have to tune it, or don't know anyone who can I would steer you to an MAF system if the engine is going to be stockish, or an aftermarket system if its not.