Injector Sizes
 

I need help with Injector Size, here is the motor i'm building and i've used desktop dyno 2000 for some dyno results.

350 CI L31 4 blot main 350 9.0 CR shortblock.
World Sportsman II 64CC assembled heads 2.02 int/1.60exh 1.5 Roller Rockers
CompCams Extreme Hydraulic Roller 224/230 .503 int/.510 exh 112 LSA
Holley Stealthram 52 mm throttle body, ADFPR
2400 stall B & M Torkmaster.



As said above I've used Desktop Dyno and it came out to peak 420 HP@6000 RPM and 421 FT LBS TQ... I'm wondering What Size Injector i'm in that range where i could get away with 24 LB or 30 LB injectors, but i want to make sure I get the right ones before I order them. Any help or experiece would be appreciated.

If that is all the horse power you plan to put out you could get away with 24 # or take your max HP X 0.45 if you are naturally aspirated and then divide that by 8 that will give you lb-hr.


edit by mod:

0.50 for "average" engines
0.55 for Supercharged engines
0.65 for Turbocharged engines

You get the sticky award today.

-- Joe

Really thanks:D

I have close to that horsepower range and I'm using the 24# injectors. With a 20% loss I'am at 412HP. My duty cycle is right at 80% max with 43.5 pounds of fuel pressure. The fuel pressure can be upped to 50 pounds for a little more horsepower/wiggle room. With my next round of mods I'm going to 30# injectors. I'm embarrassed to say what DynoSim says my HP will be. :)

At what Fuel pressure are the Ford injectors rated at.

What is the formula to see what 30lbs ford injectors are at gm Fuel pressure

They're rated at the same pressure (3 bar or 43.5psig) so there is no conversion.

Re: Injector Sizes
 

the 30lb ford racing injectors i bought a few years ago out of summit was rating theres at 38psi, unless they have changed?

Re: Injector Sizes
 

Nah, they were always rated at 43.5. Just a lot of idiots back in the day that claimed they ran at the lower rail pressures ford runs 'em at.

-- Joe

Re: Injector Sizes
 

With your combo 24s would be good.

Don't mean to rain on your parade but doubt that your
combo is going to put out that HP & Torque with the compression and cam setup your running. :2cents:
I ran a couple of those programs on setups before I
built my latest and when we put them (On) the dyno
the truth came out.
Later:)

Re: Injector Sizes
 

I had an almost identical combo, 9;1, sportsman II heads, same cam, stock TPI setup. 380hp. The HSR is probably good for another 20hp or so. I think about 400 is near close for his combo. Not sure why his compression is soo low. Mine was, because I was going to add a blower the following season.

-- Joe

Re: Injector Sizes
 

Agree, with (Good) tuning.

I was figuring 575 with mine, lite valvetrain,Rev kit,
lift at almost .6, duration up there, comp almost 11.0.
33 more cubes.
I barely broke 500:(
But we used a throttle body and 1/78 dyno headers which
were a mismatch for combo now running MR and 1/34
headers.
After good tune, in ground rollers will tell.
Its called real world:)

Later

Re: Injector Sizes
 

Some more injector info....LS1 injectors will work with TPI....of course a little modification needs to be done first. LSx injectors are longer (and don't have retention clips on the tops). For my car, we milled down the fuel rail enough to get the rail to bolt to the intake. Not the safest way to do it, and if I were to do it again I would take material off the intake (where the rail mounts). No worries on the lack of clips either. They don't move anymore than the original injectors! Best part is LSx injectors are less money, and have a better spray pattern!!! I will try to get the different flow values for everyone, but I know the dark gray ones are good for mid 30 lb/hr flow rates.:thumbsup:

Re: Injector Sizes
 

"Nah, they were always rated at 43.5. Just a lot of idiots back in the day that claimed they ran at the lower rail pressures ford runs 'em at."

Excuse me! Ford injectors are ALWAYS rated at 39.5 psi, not 43.5 as thought by some of us. I work at Ford and for the first 4 1/2 years sat next to a Ford fuel specialist. I check with him on this matter. Sure enough they are fuel checked at 39.5 psi and the catalog states 40 psi. The catalog people rounded up 39.5... CASE CLOSED.

Re: Injector Sizes
 

The equation for max supported Hp at the flywheel is:

Hp = (inj flow rate) x (# of injectors) x (duty cycle) / BSFC

with BSFC = app. 0.50 (for 3rd gen EFI engines), hopefully I have the acronym correct,,, and BSFC = 0.60 for SC and turbos
and most peolpe rcommend 80% DC or 0.8

Turn the equation around to calculate the required injector flow for a given Hp. And we get:

injector flow = [(engine Hp)] x BSFC / [(# of inj) x DC],,, for a V8 and 80% DC, we have:
injector flow = [(engine Hp)] x BSFC / 6.4

Example: if you are building an engine & the target flywheel Hp is 450 Hp, then you need 35.2 #/hr injectors, So you would want to install 36#/hr injectors (round up to the next possible injector size).


Also, to adjust the injector flow rate when the fuel rail pressure changes, we have:

new inj flow = (injector flow @ old pressure) x sqrt(new fuel pressure/old fuel pressure)

Therefore: a 30#/hr Ford injector in our cars would flow about 31.5 #/hr...

30 x SQRT(43.5/39.5) = 31.5

I hope this helps....

Re: Injector Sizes
 

Case closed? I don't see any documentation in this thread.

Why have all the ford injectors I've had tested, flowed exactly what they were supposed to, but at 43.5?

I've sent sets out, and other members have sent sets out. Did you review the old thread from years ago? They all flowed exactly what was advertised, but at 43.5 PSI. They didn't flow any extra at that pressure as folks had thought.

Here is the first thread I posted about it back in 2004 when I had my first set tested:

https://www.thirdgen.org/forums/tpi/...ow+ford+cruzin

Another member had some 30s tested. I've since had my 30s (red tops) tested a well. The only injectors I have not had tested were the popular 24s. I can't see why ford would rate the 24s at 39.5 psi, when the 30s and 36s are obviously rated at 43.5psi.. (since we have documented proof of their flow testing to back it up)

I think you need to prove a little more on the subject before you call it case closed. I have actual data, not just what some co-worker told me. But I have been wrong in the past, so please back it up. If you have some flow data, from a trusted flow bench I'd like to see it. I won't take anyones word for it though, I don't care where they worked or what they did. :)

-- Joe

Re: Injector Sizes
 

Would the 2006 Ford Racing catalog do anything for you?

You talk about actual data, that is fine, but did you check the appartus and instruments on the day of the test. I am an mechanical Engineer and I wish a had one dollar for everytime someone told me that so and so was tested and here are the results; and I find out later that the proper test procedure was not run correctly because they had to substitute some component, transducer, or whatever.

Look at the chassis dynos, you can take your car to three different dynos in the same day and get three different answers,,, which one is correct?

I know that we have argued this in the past, I can only confirm for the Ford test procedure given what the Ford fuel specialist told me,,, dont shoot the messenger! Besides, I reported that the 30#/hr injectors would flow 31.5#/hr, a 5% increase if flowed at 43.5psi instead of the rated 39.5psi. There are many tests run today in auto and other industries with a 5% error possible in the test results. I've tested stuff for 35 years, and I can tell you it is far from a perfect world. And also, the flow rate law based on the square root of the pressure is not exactly correct. I am not a fluid dynamics expect, but at least i know that there are other minor factors that are not being accounted for in that simply equation, like maybe wall friction or cavitation.

So if you dont want to accept Ford's flow specifications thats OK, we are only dealing with a few % difference.

Re: Injector Sizes
 

Maybe. Does it have the injectors I tested listed? The red top 30's that were in the v6 turbo cars, the dark blue 36's, the green top 42s, etc..

Well, I'm not going to get into a debate. If you want to contact Cruzin Performance thats fine. I trust that the services I paid for were delivered properly..


I'm not shooting the messanger, I'm shooting the data. Again, i've been proven wrong in the past. Prove me wrong, then we can call Cruzin Performance and ask him whats up with his machines.. But I'm willing to bet....


But I still want to see the data. The 39.5 you speak of btw, is the first time I've heard that number. In the past members have quoted '33, 35' and so on. Why don't you scan what you have and post it.

I'm also wondering if their is a labeling issue at hand. For example, lets pick the red top "30s".

Does ford say they are 30# at 39.5psi, or 28# ??

See I wonder if people are confusing which pressure they are labeling them at. Everyone 'knows' a red top is 30#, was that because the first guy that tested one on a SAE pressure labeled it as 30#, but now years later people (say) ford uses a lower pressure so now people think they are 32-33#, when really ford was labeling them as 28# the whole time?

This obviously needs more discussion, and more data.

-- Joe

Re: Injector Sizes
 

The Ford Racing catalog list about 10 injectors 19#, 24#, 30# etc, in both EV1 and EV6 connectors. The note at the bottom of this section states that the flow values are measured at 40psi (rounded from 39.5).

I am not trying to prove you wrong, just stating what I know from my experience here at Ford. You are one of the most respected contributors to this board. Whats very ironic for me is that I have been a Camaro guy my whole life and now I find myself specing tires for Mustang and Focus!!!!

Rich @ Cruzin performance is a great guy, you can only trust in him to do the best and get the best data that he can. In fact, 7 or so years ago, Rich flow tested my Ford 24s, now I need to find the flow sheet.

Re: Injector Sizes
 

In general, injectors are usually rated at 43.5psi (3bar), including ford injectors that are made for ford by other companies. I haven’t tried a new set in the last year or 2, but older ford injectors test correctly at 43.5 just like any other.

As far as the ford racing catalog, it just appears to be screwed up. Every one since 2004 list a different delta test pressure, the 2008 one lists 39.15psi and list the same flow numbers for the same part numbers as they did in 2006 at 40psi and earlier at 43.5. I'd believe that the catalog is wrong before I'm going to believe that the same injectors change flow every year...

Re: Injector Sizes
 

I read somewhere that the ford injectors do not work well at idle speeds because our ecm drivers are not compatible. Anyone have a comment on this?

thx

Jeff

Re: Injector Sizes
 

That's totally not true. The Ford injectors are high impedance injectors just like the factory units. These are also known as Saturated drivers. If you were using low impedance injectors they would not work, but none of the Ford Motorsport line of injectors are low impedance. Bosch (they manufacture the Ford Motorsport line of injectors) does have some low impedance injectors but they are for mostly european models and come in factory vehicles.

The Ford Motorsport injectors have the same specifications electrically as the OEM TPI injectors. The OEM TPI injectors are more prone actually to electrical shorts and leaks versus the Bosch counterparts. The TPI injectors are 1.4mm longer but I've bolted up dozens of sets of the Bosch 19lb and 24lb injectors in TPI systems before and never had a leak. Some people like to grind down the fuel rail posts but it's not necessary.

Re: Injector Sizes
 

They’re the same length but the o-rings are spaced a different distance apart.

Electrically they’re similar (all high Z injectors sort of fall in a range), but the difference is that they spray in a different pattern, which in theory should dictate a different injector mounting location. OTOH, I have a set of ford 36pph blue top injectors in one of my TPI cars and some 22.5pph pink top injectors in another.

Re: Injector Sizes
 

I'm sorry if this is off topic, but I have world sportsman II heads, 1.6 roller-rockers, hooker 1-3/4", 3" collector headers, h-pipe and dual bullet mufflers. Along with a TPIS airfoil, and the intakes fully ported, see pics. On my site. I am running 24# SVO ford injectors, and out of a GM High tech motor, that was making 329 horses at the wheels he ran 14* of timing, along with 38PSI to the injectors, and found the best results and horsepower, but have any of you experienced more power on the dyno, at 43.5 PSI?

I'm going to add some more photos to my site tonight and maybe a good quick video, but I'll add some more.

Re: Injector Sizes
 

so Ford racing are rated at 39,5 or 43,5 PSI ? that is kinda important for me with setting MegaSquirt

best regards

Re: Injector Sizes
 

Well it doesn't really matter, but which injectors are you using?

-- Joe

Re: Injector Sizes
 

actually it does, it makes 2lbs difference and makes possibility to go over 90% of injector efficiency and that is not good idea, also by knowing exact inj capibility it is easier to fine tune fuel with megasquirtII

best regards

Re: Injector Sizes
 

No, it doesn't matter.

Your pulsewidths are going to be what they are regardless. It doesn't matter if you tell it it's a 30# injector or a 32#..

There is nothing wrong with going over 90% duty cycle either.

The smart thing to do is figure out the appropriate ratio of injector size and fuel pressure to maintain idle at a sane injector pulsewidth, and provide enough fuel for WOT operation.



-- Joe

Re: Injector Sizes
 

i'm not 100% convinced but as You have bigger experience in all this i'll just put 32

best regards

Re: Injector Sizes
 

well http://www.fordracingparts.com/ are saying this :

Target Injection Pressure = 39.15 psid

And that info have been there for some years now, I checked several different injectors and they all say 39.15 PSI as target pressure.

Also making the injectors work at a lower duty cycle will make them work longer :)
The injectors (todays injectors) can work good at 90% DC but the lower duty cycle the longer it will last. Same for the fuel pumps..

Re: Injector Sizes
 

TheKing: thank you. So much has been written on this business, I am tired of it.

Re: Injector Sizes
 

Yeah that is what it says. I've looked at the spec sheet for the 42# injectors as well from Ford.

My guess is that, ford rates injectors at 39 psi, however, some injectors that have been used over the years (i.e, dark blue top) people have flowed and described them as what they flowed at SAE.

For example, Say I find a pair of injectors on an 80 something ford. I put them on the flowbench using sae pressure, using a testing fluid with a specific gravity of gasoline, and i get a result. That result is 36. I then say "these ford injectors with this part number is 36#".. A year later, some guy on a forum says those injectors are 36# - but ford rates them at 39psi, so they must be bigger than 36#..

If ford puts it in a box, and specifies flow rate, pressure, etc than I'll believe it. If it's in an OE vehicle, I don't care what the forum says. I'm having it tested to see what it really does.

Injectors don't know what their duty cycle is. Don't be silly.. Duty cycle is a number calculated based on time between firing. If an injector is open 9 milliseconds, and it can only be open for 10 milliseconds max before the spark plug fires, it has no idea.

What if we're shifting at a lower RPM, and now our window is 12 or 14 milliseconds. Does it being open for 9 now becomes ok because on paper it's a lower duty cycle? c'mon.. silly logic.

-- Joe

Re: Injector Sizes
 

Now but making something work harder will make it last shorter.
If you make something work hard at 99% instead of 75% the unit who works at 75% will last longer then the one working at 99% (This is IF you have a to small injector, it have to work all the time, maybe at 100% to deliver the fuel that isnt good for a long life injector....)

(example: an engine running 7000rpm non stop and an engine running 3500rpm wich one will last longer ?.. not the 7000rpm, same for injectors)

so if you have calculated #30 injectors and thats on the close side, go with little larger instead and they wont have to work at so high rate..

The injectors dont know OFCOURSE what duty cycle they are at, but they will feeel, heat, stress etc for working "on the edge" or close to what they can deliver...

Well Ford have speciefied and put it in their boxes :)

Well lets drop this all, The info is at Ford Racing about the pressure, so now we all can sleep again :)

Re: Injector Sizes
 

Generally this is true, however you are forgetting something. The higher the RPM, the shorter the window is for the injector to fire. So in theory, the higher the RPM the less the injector can work.


You don't understand. The engine at 7000RPM has was less time to fire than the engine at 3500 rpm.

The injector is on or off, for a period of time calculated by the ecm. The whole 'duty cycle' theory, is simply us saying how long it's open vs the window of time we have. Like I said before, if the injector pulses for 9 milliseconds at a time, and the window is 10ms it is at 90% dutycycle, and everyone says "omg that is bad". Yet if the window was 20ms, it's now at 45% duty cycle and everyone feels great. However, BOTH INJECTORS ARE FIRING AT THE SAME RATE, so they are both working just as hard.

Duty cycle is an illusion.


-- Joe

Re: Injector Sizes
 

the 7000RPM example wasnt for the injectors, I was just saying, and carb engine or any engine working at constant 7000rpm would last shorter then an working at 3500rpm (mechanical...)

And yes, the higher rpm the less time open, But if you have a TO SMALL injector it will work hard on idle, mid and high range..

I get your point, but the main thing was the 39.15 PSI info about the Ford, sorry for making you debate this :)

Re: Injector Sizes
 

That's fine.

In regards to the 39psi thing, I'm sure the FMS injectors are rated at that because they say so.

I do know other injectors have been flow tested and I'm aware of what they flow.

-- Joe

Re: Injector Sizes
 

Actually, 39psi is what the original fox mustangs shot for. As far as "ratings," it seems like every year that the FMS or SVO (depending on year) had them rated at a different PSI and still said that they were the same size (I know that I've seen everything a range of high 30's/low 40's). I believe that they are _actually_ rated at 43.5psig just like most other injectors (that's what they test closest to there rated flow on a flow bench)

Re: Injector Sizes
 

hey all if you want a source for 30# injectors for dyno testing and don't want spend 300.00+ to find out they're not big enough or too big......buicks, pontiacs, oldsmobile, and chevys i think from 1989-1994 with the quad four motors run 30 lb/hr injectors stock(info from a head tech. at gm dealership)......if someone would want to test one before running out to the bone yard or the local auto parts store i have two sitting here. i'll ship them out to any one who has the proper equipment to test and give the info back to the forum at no cost. just pm me

Re: Injector Sizes
 

IF using an aftermarket EFI system that supports Open Valve Injection with Start-of-Injection or End-of-Injection Angle Timing, where you're injecting fuel primarily after overlap and before the intake valve closes (at WoT); closed valve injection is still generally used at idle / startup, a 20% to 30% injector sizing is used.


The seemingly huge Injector Dynamics injectors make much more sense when looking at a 20% sizing for OVI.

This strategy requires injectors that perform predictably at low pulse widths and with low-ish latencies; tuning will require high quality injector categorization data, that's also not available from all sellers of injectors.


Adam

Re: Injector Sizes
 

You noticed the last post in this thread was 12 years ago, right?

-- Joe

Re: Injector Sizes
 

Yep. And if you search for “injector sizes” it comes up high on the list of results. Now it will return 2022 answers.


Adam