Need some guidance for cold air intake and fuel injector size

roldy

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I have a 351W crate that is rated at 575 HP and 575 TQ. Upper intake is an Edelbrock Super Victor EFI with an Edelbrock Intake elbow. I'm not sure what fuel injector size or brand I should go with. I originally planned on 60lb injectors and getting an 80mm throttle body. I'm thinking that maybe 60 lbs is a bit much. Way later down the road I plan on doing a twin turbo setup. What do you guys suggest I do? What brands do you guys like for injectors, throttle bodies, and MAF's?
 
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nickyb

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42's or 46's will do for naturally aspirated, brand is up to you but keep in mind "you get what you pay for" . I'm sure that crate 351 was a pretty penny so don't cheap out on injectors or maf. Post some pics for us.
 

Steel1

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I run 42s on my n/a 393 without issue, but if you plan on boost in the future might as well get the 60s now.
 

roldy

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I run 42s on my n/a 393 without issue, but if you plan on boost in the future might as well get the 60s now.
That was also my line of thought. The ones I was looking at are 60 lb DeatschWerks injectors. As for throttle body and MAF, I'm not sure what size I should be running for my application.

 

Steel1

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Old rule of thumb is to have maf slightly larger than tb.
If you already have 80mm tb then you could go with something like a 90mm maf, keep in mind though
when you start getting into larger mafs etc. you will need some way to tune ecu .
I'm currently SD so no maf, running off a Pimpxs.
 

jrichker

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I have a 351W crate that is rated at 575 HP and 575 TQ. Upper intake is an Edelbrock Super Victor EFI with an Edelbrock Intake elbow. I'm not sure what fuel injector size or brand I should go with. I originally planned on 60lb injectors and getting an 80mm throttle body. I'm thinking that maybe 60 lbs is a bit much. Way later down the road I plan on doing a twin turbo setup. What do you guys suggest I do? What brands do you guys like for injectors, throttle bodies, and MAF's?

Fuel injector sizing & injector photos

Revised 26-Dec-2014 to add statement about figures are for flywheel HP and not rear wheel HP

Injector HP ratings: this flywheel HP, not rear wheel HP.
Divide flow rating by.5 and multiply the result by the number of injectors. This uses a 100% duty cycle. These ratings are for naturally aspirated engines at the flywheel.

Example:
19/.5 = 38, 38 x 8 = 304 HP
24/.5 = 48, 48 x 8 = 384 HP
30/.5 = 60, 60 x 8 = 480 HP
36/.5 = 72, 72 x 8 = 576 HP
42/.5 = 84, 84 x 8 = 672 HP

The preferred duty cycle is about 85% maximum, so for a safety factor multiply the final figure times .85.

19/.5 = 38, 38 x 8 = 304 HP x .85 = 258 HP
24/.5 = 48, 48 x 8 = 384 HP x .85 = 326 HP
30/.5 = 60, 60 x 8 = 480 HP x .85 = 408 HP
36/.5 = 72, 72 x 8 = 576 HP x .85 = 490 HP
42/.5 = 84, 84 x 8 = 672 HP x .85 = 571 HP

Remember that the above ratings are at 39 PSI. Increasing the pressure will effectively increase the flow rating. Example: a 19 lb injector will flow 24 lbs at 63 PSI, and a 24 lb injector will flow 30 lbs at 63 PSI.

See http://users.erols.com/srweiss/calcpchg.htm to get the calculators used in these examples.


Here's the duty cycle explanation. Duty cycle is how much of the time the intake valve is open that the injectors are turned on. The 85% figure means that for 85% of the time the intake valve is open, the injectors are spraying. The idea is that you want some percentage of the duty cycle left over so that you have some room to grow the process.

If you are at 100% and you need more fuel, all you can do is turn up the fuel pressure. That means the whole fuel curve from idle to WOT is affected. Maybe you are already too rich at idle, and turning up the fuel pressure makes it worse. If you had some injector duty cycle left to play with, a custom tune could use that where it is needed. That would not over richen the whole range from idle to WOT.

If you did turn up the fuel pressure, you might be able to change the injector duty cycle to get the air/fuel mixture ratio you want since the injectors will have extra fuel delivery capability.

With larger than stock injectors or higher that stock fuel pressure, you will need an aftermarket MAF that matches the injector size. The MAF “lies” to the computer to get a fuel delivery schedule that meets the engine’s needs and isn’t too rich or too lean. The best strategy is an aftermarket MAF and a custom tune to insure the best air/fuel ratio over all the RPM range.

Don't forget to increase the fuel pump size when you increase injector size or significantly increase the fuel pressure

Copied from the FORD RACING PERFORMANCE PARTS catalog:

PROPERLY SIZING FUEL SYSTEM COMPONENTS


Fuel Pumps
The following information is presented assuming the above information has been taken into consideration regarding BSFC, fuel pressure and specific gravity of the fuel being used. Most fuel pumps for electronic fuel injection are rated for flow at 12 volts @ 40 PSI. Most vehicle charging systems operate anywhere from 13.2v to 14.4v. The more voltage you feed a pump, the faster it spins which, obviously, will put out more fuel. Rating a fuel pump at 12 volts then, should offer a fairly conservative fuel flow rating allowing you to safely determine the pump’s ability to supply an adequate amount of fuel for a particular application.

As previously mentioned, engines actually require a certain WEIGHT of fuel, NOT a certain VOLUME of fuel per horsepower. This can offer a bit of confusion since most fuel pumps are rated by volume, and not by weight. To determine the proper fuel pump required, a few mathematical conversions will need to be performed using the following information. There are 3.785 liters in 1 US Gallon. 1 gallon of gasoline (.72 specific gravity @ 65° F) weighs 6.009 LBS.

To be certain that the fuel pump is not run to its very limit, which could potentially be dangerous to the engine, multiply the final output of the fuel pump by 0.9 to determine the capacity of the fuel pump at 90% output. This should offer plenty of ‘cushion’ as to the overall “horsepower capacity” of the fuel pump.

To determine the overall capacity of a fuel pump rated in liters, use the additional following conversions:
(Liters per Hour) / 3.785 = Gallons
Multiply by 6.009 = LBS/HR
Multiply by 0.9 = Capacity at 90%
Divide by BSFC = Horsepower Capacity
So for a 110 LPH fuel pump:
110 / 3.785 = 29.06 Gallons
29.06 x 6.009 = 174.62 LBS/HR
174.62 x 0.9 = 157 LBS/HR @ 90% Capacity
157 / 0.5 = 314 HP safe naturally aspirated “Horsepower Capacity”

Safe “Horsepower Capacity” @ 40 PSI with 12 Volts
60 Liter Pump = 95 LB/HR X .9 = 86 LB/HR, Safe for 170 naturally aspirated Horsepower
88 Liter Pump = 140 LB/HR X .9 = 126 LB/HR, Safe for 250 naturally aspirated Horsepower
110 Liter Pump = 175 LB/HR X .9 = 157 LB/HR, Safe for 315 naturally aspirated Horsepower
155 Liter Pump = 246 LB/HR X .9 = 221 LB/HR, Safe for 440 naturally aspirated Horsepower
190 Liter Pump = 302 LB/HR X .9 = 271 LB/HR, Safe for 540 naturally aspirated Horsepower
255 Liter Pump = 405 LB/HR X .9 = 364 LB/HR, Safe for 700 naturally aspirated Horsepower

Note: For forced induction engines, the above power levels will be reduced because as the pressure required by the pump increases, the flow decreases. In order to do proper fuel pump sizing, a fuel pump map is required, which shows flow rate versus delivery pressure.

That is, a 255 liter per hour pump at 40 PSI may only supply 200 liters per hour at 58 PSI (40 PSI plus 18 lbs of boost). Additionally, if you use a fuel line that is not large enough, this can result in decreased fuel volume due to the pressure drop across the fuel feed line: 255 LPH at the pump may only result in 225 LPH at the fuel rail.


My Comments:

A lot of people oversize the fuel pump by buying a 255LPH pump thinking that the fuel pump regulator will just pass the excess gas back to the tank. It does, but… Did you ever consider that circulating the fuel around as a 255 LPH pump does will cause the gas to pickup engine heat? What happens to hot gasoline? It boils off or pressurizes the fuel tank! With most of the 5.0 Mustangs having the carbon canister removed or disabled, the car stinks like gas, and the gas mileage drops since the hot fuel evaporates away into the air.



Diagram courtesy of Tmoss & Stang&2birds
Ford_Injector_Guide.jpg


See the following website for some help from Tmoss (diagram designer) & Stang&2Birds (website host) for help on 88-95 wiring http://www.veryuseful.com/mustang/tech/engine/ Everyone should bookmark this site.

Ignition switch wiring

Fuel, alternator, A/C and ignition wiring

Complete computer, actuator & sensor wiring diagram for 88-91 Mass Air Mustangs

Vacuum diagram 89-93 Mustangs

HVAC vacuum diagram

TFI module differences & pinout

Fuse box layout
 
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roldy

New Member
Jul 22, 2020
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Fuel injector sizing & injector photos

Revised 26-Dec-2014 to add statement about figures are for flywheel HP and not rear wheel HP

Injector HP ratings: this flywheel HP, not rear wheel HP.
Divide flow rating by.5 and multiply the result by the number of injectors. This uses a 100% duty cycle. These ratings are for naturally aspirated engines at the flywheel.

Example:
19/.5 = 38, 38 x 8 = 304 HP
24/.5 = 48, 48 x 8 = 384 HP
30/.5 = 60, 60 x 8 = 480 HP
36/.5 = 72, 72 x 8 = 576 HP
42/.5 = 84, 84 x 8 = 672 HP

The preferred duty cycle is about 85% maximum, so for a safety factor multiply the final figure times .85.

19/.5 = 38, 38 x 8 = 304 HP x .85 = 258 HP
24/.5 = 48, 48 x 8 = 384 HP x .85 = 326 HP
30/.5 = 60, 60 x 8 = 480 HP x .85 = 408 HP
36/.5 = 72, 72 x 8 = 576 HP x .85 = 490 HP
42/.5 = 84, 84 x 8 = 672 HP x .85 = 571 HP

Remember that the above ratings are at 39 PSI. Increasing the pressure will effectively increase the flow rating. Example: a 19 lb injector will flow 24 lbs at 63 PSI, and a 24 lb injector will flow 30 lbs at 63 PSI.

See http://users.erols.com/srweiss/calcpchg.htm to get the calculators used in these examples.


Here's the duty cycle explanation. Duty cycle is how much of the time the intake is open the injectors are turned on. The 85% figure means that for 85% of the time the intake valve is open, the injectors are spraying. The idea is that you want some percentage of the duty cycle left over so that you have some room to grow the process.

If you are at 100% and you need more fuel, all you can do is turn up the fuel pressure. That means the whole fuel curve from idle to WOT is affected. Maybe you are already too rich at idle, and turning up the fuel pressure makes it worse. If you had some injector duty cycle left to play with, a custom tune could use that where it is needed. That would not over richen the whole range from idle to WOT.

If you did turn up the fuel pressure, you might be able to change the injector duty cycle to get the air/fuel mixture ratio you want since the injectors will have extra fuel delivery capability.

With larger than stock injectors or higher that stock fuel pressure, you will need an aftermarket MAF that matches the injector size. The MAF “lies” to the computer to get a fuel delivery schedule that meets the engine’s needs and isn’t too rich or too lean. The best strategy is an aftermarket MAF and a custom tune to insure the best air/fuel ratio over all the RPM range.

Don't forget to increase the fuel pump size when you increase injector size or significantly increase the fuel pressure

Copied from the FORD RACING PERFORMANCE PARTS catalog:

PROPERLY SIZING FUEL SYSTEM COMPONENTS


Fuel Pumps
The following information is presented assuming the above information has been taken into consideration regarding BSFC, fuel pressure and specific gravity of the fuel being used. Most fuel pumps for electronic fuel injection are rated for flow at 12 volts @ 40 PSI. Most vehicle charging systems operate anywhere from 13.2v to 14.4v. The more voltage you feed a pump, the faster it spins which, obviously, will put out more fuel. Rating a fuel pump at 12 volts then, should offer a fairly conservative fuel flow rating allowing you to safely determine the pump’s ability to supply an adequate amount of fuel for a particular application.

As previously mentioned, engines actually require a certain WEIGHT of fuel, NOT a certain VOLUME of fuel per horsepower. This can offer a bit of confusion since most fuel pumps are rated by volume, and not by weight. To determine the proper fuel pump required, a few mathematical conversions will need to be performed using the following information. There are 3.785 liters in 1 US Gallon. 1 gallon of gasoline (.72 specific gravity @ 65° F) weighs 6.009 LBS.

To be certain that the fuel pump is not run to its very limit, which could potentially be dangerous to the engine, multiply the final output of the fuel pump by 0.9 to determine the capacity of the fuel pump at 90% output. This should offer plenty of ‘cushion’ as to the overall “horsepower capacity” of the fuel pump.

To determine the overall capacity of a fuel pump rated in liters, use the additional following conversions:
(Liters per Hour) / 3.785 = Gallons
Multiply by 6.009 = LBS/HR
Multiply by 0.9 = Capacity at 90%
Divide by BSFC = Horsepower Capacity
So for a 110 LPH fuel pump:
110 / 3.785 = 29.06 Gallons
29.06 x 6.009 = 174.62 LBS/HR
174.62 x 0.9 = 157 LBS/HR @ 90% Capacity
157 / 0.5 = 314 HP safe naturally aspirated “Horsepower Capacity”

Safe “Horsepower Capacity” @ 40 PSI with 12 Volts
60 Liter Pump = 95 LB/HR X .9 = 86 LB/HR, Safe for 170 naturally aspirated Horsepower
88 Liter Pump = 140 LB/HR X .9 = 126 LB/HR, Safe for 250 naturally aspirated Horsepower
110 Liter Pump = 175 LB/HR X .9 = 157 LB/HR, Safe for 315 naturally aspirated Horsepower
155 Liter Pump = 246 LB/HR X .9 = 221 LB/HR, Safe for 440 naturally aspirated Horsepower
190 Liter Pump = 302 LB/HR X .9 = 271 LB/HR, Safe for 540 naturally aspirated Horsepower
255 Liter Pump = 405 LB/HR X .9 = 364 LB/HR, Safe for 700 naturally aspirated Horsepower

Note: For forced induction engines, the above power levels will be reduced because as the pressure required by the pump increases, the flow decreases. In order to do proper fuel pump sizing, a fuel pump map is required, which shows flow rate versus delivery pressure.

That is, a 255 liter per hour pump at 40 PSI may only supply 200 liters per hour at 58 PSI (40 PSI plus 18 lbs of boost). Additionally, if you use a fuel line that is not large enough, this can result in decreased fuel volume due to the pressure drop across the fuel feed line: 255 LPH at the pump may only result in 225 LPH at the fuel rail.


My Comments:

A lot of people oversize the fuel pump by buying a 255LPH pump thinking that the fuel pump regulator will just pass the excess gas back to the tank. It does, but… Did you ever consider that circulating the fuel around as a 255 LPH pump does will cause the gas to pickup engine heat? What happens to hot gasoline? It boils off or pressurizes the fuel tank! With most of the 5.0 Mustangs having the carbon canister removed or disabled, the car stinks like gas, and the gas mileage drops since the hot fuel evaporates away into the air.



Diagram courtesy of Tmoss & Stang&2birds
Ford_Injector_Guide.jpg


See the following website for some help from Tmoss (diagram designer) & Stang&2Birds (website host) for help on 88-95 wiring http://www.veryuseful.com/mustang/tech/engine/ Everyone should bookmark this site.

Ignition switch wiring

Fuel, alternator, A/C and ignition wiring

Complete computer, actuator & sensor wiring diagram for 88-91 Mass Air Mustangs

Vacuum diagram 89-93 Mustangs

HVAC vacuum diagram

TFI module differences & pinout

Fuse box layout
Thanks for this. Is there something similar in regards to a table for throttle body size selection?
 

My92cashtrap

Member
May 11, 2019
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These resources may help:

CFM rates of common TB's: technical-support-faq
Fuel Injector sizing: https://www.promracing.com/injector.php/

From a Stangnet post:
Accufab said:
Here are some CFM ratings on "an engine", based on displacement and RPM's, but without any "CFM losses" due to heads, intakes, exhaust, etc.

Disp. (in cu. in.)..........CFM @ 6000 RPM.........6500 RPM............7000 RPM
280.....................................486....... ..........527....................567
290.....................................503....... ..........545....................587
300.....................................521....... ..........564....................608
310.....................................538....... ..........583....................628
320.....................................556....... ..........602....................648
330.....................................573....... ..........621....................668
340.....................................590....... ..........639....................689
350.....................................608....... ..........658....................709
360.....................................625....... ..........677....................729
370.....................................642....... ..........696....................749
380.....................................660....... ..........715....................770
390.....................................677....... ..........734....................790
400.....................................694....... ..........752....................810
410.....................................712....... ..........771....................830
420.....................................729....... ..........790....................851
430.....................................747....... ..........809....................871

These CFM ratings are all "naturally aspirated" of course. I'm not suggesting that you only use a TB or a carb that is equal to these ratings, but (a), it won't hurt if you do, and (b), it won't help if you use one much bigger than what the engine can use.

And another Stangnet post:
Guys, in the vast majority of cases, the throttle body is not the weak link or restrictor in these N/A engines. I do not understand why people make such a big deal about getting the 'biggest and baddest.'

At 6,000 rpm a 347 can flow 600cfm. That is with NO restriction. Any 347 or similar has a ton of restriction. That cfm rating does not include a heads, cam package on it. The cam only is open for little amounts of time. So the cfm rating is further cut.

Guys are routinely sticking on throttle bodies that flow two to two and half times greater than their engine sees at it's peak.:nono:

I have to ask...why?

If you've got a throttle body that delivers 100% of the peak air requirements of your engine when the throttle plate is fully open, you have control of the air throughout 100% of the throttle position range. If you go to an oversized TB that delivers 100% of the air that your engine can consume while the throttle plate is only 60% open, you have given up usable throttle-control range for no advantage.

Guys that are constantly defending the oversized throttle bodies are only talking about wide open performance (WOT). What about the 99% of the time that we cruise around at part throttle?

Throttle modulation becomes more difficult. The gas pedal modulation becomes touchier.

Again, look somewhere else for a restriction, not an oversized throttle body.

An Accufab (for example) 65mm throttle body flows more than enough for a 347 stroker with 664cfm continously, while the 347 would see 600cfm if it had no heads, cam, or intake on it, which of course is impossible.

Enthusiasts need to quit ignoring the facts.

Read an article from the top throttle body maker themself and let them tell the tale:

http://www.accufabracing.com/article 3.htm (No longer active)
 
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Dan02gt

10 Year Member
Mar 2, 2003
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Greenville, NC
I have a 351W crate that is rated at 575 HP and 575 TQ. Upper intake is an Edelbrock Super Victor EFI with an Edelbrock Intake elbow. I'm not sure what fuel injector size or brand I should go with. I originally planned on 60lb injectors and getting an 80mm throttle body. I'm thinking that maybe 60 lbs is a bit much. Way later down the road I plan on doing a twin turbo setup. What do you guys suggest I do? What brands do you guys like for injectors, throttle bodies, and MAF's?
The guy that tuned my car really liked the Siemens Deka 80s. I'm running them in a H/C/I 302 and it runs great. Common forum thinking is that they would be way to big for my setup. I think the key is having an injector that very accurately delivers the fuel that it's rated for so you can get your fueling correct in your tune.
 

96pushrod

I think they're a little easier to get off
May 15, 2018
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If buying new, there’s literally no reason not to buy deka 80s. They’re the best injector for under $400 and they’ll run awesome. They won’t be “too big”
 

a91what

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You will do well to get at least an 80lb injector and a 340lph pump at a minimum for a big inch turbo engine. I have a twin turbo 393 and this is what I run and I am still limited to what the fuel pump can support.
 

roldy

New Member
Jul 22, 2020
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If buying new, there’s literally no reason not to buy deka 80s. They’re the best injector for under $400 and they’ll run awesome. They won’t be “too big”
What is your experience with the cold start on using the deka's? I've seen a video of a guy talking about problems tuning these injectors.
 

Dan02gt

10 Year Member
Mar 2, 2003
759
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Greenville, NC
What is your experience with the cold start on using the deka's? I've seen a video of a guy talking about problems tuning these injectors.
No problems whatsoever with cold startup. I did have to drop the pulse width on hot start up significantly to get it to start without flooding though. That with a Quarterhorse on a stock ECU though.

Believe it or not there are tons of fake injectors out there so if you’re thinking about getting some make sure to get them from a legitimate source like poweraddersolutions.com.
 

96pushrod

I think they're a little easier to get off
May 15, 2018
993
600
103
29
Savannah
What is your experience with the cold start on using the deka's? I've seen a video of a guy talking about problems tuning these injectors.
Zero issues anywhere. I don’t know why there would ever be an issue with a cold start and injectors.