19# injectors, Stock MAF, How much HP HP can they support

94-302-vert · Nov 15, 2005

Just as the title says. How much HP can they support if you raise the fuel pressure too (kinda overdrive the injectors)?

final5-0 · Nov 15, 2005

Chris

I'm gonna predict you've opened up a Can O Worms with this thread and you're gonna get a lot of opinions.

Here is mine

Maf first

I almost made it to 300rwhp with mine before it pegged.

The maf is all about air flow and really has nothing to do with inj size if you look at it from how things really work or how Ford does it in the first place.

A ball park answer to your Q might be in the range of say 285 to 310rwhp. Several things makes the answer one of those ... it depends on kinda things.

Now for the inj's

Let me be the FIRST to tell you ...... 300 hp.
You see it all the time on these forums and to that I say ................

that is misleading info at best

The reason I feel so strongly about that is ..................
That is motor hp and most of us Stangers think in terms of wheel hp.

Think about it as it really is!

15% driveline loss is 300 X .85 is 255rwhp

20% driveline loss is 300 X .20 is 240rwhp

When you look at it like that ...... it kinda makes you think about the fact that .......................
Ford put 24's in the Cobra.

IIRC, I think I've seen some say an auto trans combo will sap a bit MORE than 20% but I think you see where I'm goin with this by now.

As for the elevated fuel pressure thing ................

Yes it is true, elevated pressure will make the inj act bigger but IMHO ........

That method is messy & unstable cause the pcm is gonna try to correct things and over time........................

your final af ratio may not REALLY be what it was when you had it set on the dyno.

Grady

Black95GTS · Nov 15, 2005

final5-0 said:
Chris

I'm gonna predict you've opened up a Can O Worms with this thread and you're gonna get a lot of opinions.

Here is mine

Maf first

I almost made it to 300rwhp with mine before it pegged.

The maf is all about air flow and really has nothing to do with inj size if you look at it from how things really work or how Ford does it in the first place.

A ball park answer to your Q might be in the range of say 285 to 310rwhp. Several things makes the answer one of those ... it depends on kinda things.

Now for the inj's

Let me be the FIRST to tell you ...... 300 hp.
You see it all the time on these forums and to that I say ................

that is misleading info at best

The reason I feel so strongly about that is ..................
That is motor hp and most of us Stangers think in terms of wheel hp.

Think about it as it really is!

15% driveline loss is 300 X .85 is 255rwhp

20% driveline loss is 300 X .20 is 240rwhp

When you look at it like that ...... it kinda makes you think about the fact that .......................
Ford put 24's in the Cobra.

IIRC, I think I've seen some say an auto trans combo will sap a bit MORE than 20% but I think you see where I'm goin with this by now.

As for the elevated fuel pressure thing ................

Yes it is true, elevated pressure will make the inj act bigger but IMHO ........

That method is messy & unstable cause the pcm is gonna try to correct things and over time........................

your final af ratio may not REALLY be what it was when you had it set on the dyno.

Grady

Grady's right about fuel pressure, I just made this reply in a nitrous thread. If you want to play with it, buy a TwEECer or a PMS and mess with your a/f ratio that way. The T4M0 adjusts everything back to 39psi after a while anyway.

I guess age brings wisdom......

- Adam

final5-0 · Nov 15, 2005

Black95GTS said:
I guess age brings wisdom......

- Adam

Hummmmmmmmmmm

What are you trying to say ADAM ?

Grady

94-302-vert · Nov 15, 2005

Ok,

Thanks Grady.. Kinda what I thought and here is why I ask. Bud of mine has an H/C/I (GT40 cast iron, unknown, TFS) & S-trim w/ AODE car. he still has the 19# inj with higher presssure and the stock MAF. He still needs to be dyno tuned. BUT he ran some HP numbers with a g-tech and basically got 260-280ish on the g-tech. So we are trying to figure out what else needs to be upgraded (or should be) before getting Dyno tuned.

final5-0 · Nov 15, 2005

94-302-vert said:
Ok,

Thanks Grady.. Kinda what I thought and here is why I ask. Bud of mine has an H/C/I (GT40 cast iron, unknown, TFS) & S-trim w/ AODE car. he still has the 19# inj with higher presssure and the stock MAF. He still needs to be dyno tuned. BUT he ran some HP numbers with a g-tech and basically got 260-280ish on the g-tech. So we are trying to figure out what else needs to be upgraded (or should be) before getting Dyno tuned.

My thoughts would be he has to be running a FMU so he is working those tiny 19's really hard.

Lots of peeps do the FMU thing and it works for them without a doubt.

On the other hand .....................

Some peeps who use that method to tune have had them fail and then ............... BOOM.

Way too risky for me, and I have the kind of luck that ...... if 1 in 10 can have any kind of probs .............. dadgummit if I ain't always that 1 guy

Another thought I got about your friends combo ...................

Bet he's pegging the stock maf way before his redline

Grady

Black95GTS · Nov 15, 2005

94-302-vert said:
Ok,

Thanks Grady.. Kinda what I thought and here is why I ask. Bud of mine has an H/C/I (GT40 cast iron, unknown, TFS) & S-trim w/ AODE car. he still has the 19# inj with higher presssure and the stock MAF. He still needs to be dyno tuned. BUT he ran some HP numbers with a g-tech and basically got 260-280ish on the g-tech. So we are trying to figure out what else needs to be upgraded (or should be) before getting Dyno tuned.

I would tell your friend to upgrade to 42 pound squirters, ditch the FMU, get a 80mm MAF cal'd for them, and have at it with the stock FP. Going lean sucks period, but going lean with a power adder is certain disaster. I wouldn't even push it with the g-tech until he put in bigger injectors. Don't be afraid to go big on injectors either, I never understood where people are afraid of this. If you get them "too big" then it just wont get used. Say you need 38 pounds, you get 42s, the extra 4 lbs just wont get used and you have a safety factor to work with. Oh and I hope he also has a high flow pump to go with the bigger injectors.

I guess there are some tuning issues with bigger injectors and that scares people, but I'd rather have tuning issues then massive detonation issues.

adam

94-302-vert · Nov 17, 2005

Can we get away with lightning 42# injectors and a lightening MAF without the tune for now?

green95gt · Nov 17, 2005

I asked that question awhile back and everyone told me you have to have a tune with the lightning mass air meter or the car won't run with it.

94-302-vert said:
Can we get away with lightning 42# injectors and a lightening MAF without the tune for now?

CManT1914 · Nov 17, 2005

94-302-vert said:
Ok,

Thanks Grady.. Kinda what I thought and here is why I ask. Bud of mine has an H/C/I (GT40 cast iron, unknown, TFS) & S-trim w/ AODE car. he still has the 19# inj with higher presssure and the stock MAF. He still needs to be dyno tuned. BUT he ran some HP numbers with a g-tech and basically got 260-280ish on the g-tech. So we are trying to figure out what else needs to be upgraded (or should be) before getting Dyno tuned.

Your friend is insane to run 19lb injectors on a blown h/c/i car. Those FMU's are like bandaid's on a severed limb, they just don't do much IMHO. I'd get some bigger injectors on there asap, say 42's.

(there's a reason he's only making 260-280 with a h/c/i blown car too)

WhiteDevil · Nov 17, 2005

Yeah i have a 19# calibrated Pro-M and im making around 300rwhp and when i get to around 5,800rpm it starts to peg out around 4.97volts. So thats about the airflow limit for the stock MAF calibration. I ran 19#ers with the fuel pressure bumped for a while and i was making 250rwhp with the stock heads. Im sure their duty cycle was WAY up there though, lol. All in all it seems everyone here is on the same page with this.

CManT1914 · Nov 17, 2005

I'm gonna add one more thing as I don't know if it's been mentioned.

If you raise the fuel pressure to "overdrive" the injectors, assuming the PCM doesn't compensate for this and lower it back down again, you run the risk of wearing out the injectors a lot quicker.

WhiteDevil · Nov 17, 2005

CManT1914 said:
I'm gonna add one more thing as I don't know if it's been mentioned.

If you raise the fuel pressure to "overdrive" the injectors, assuming the PCM doesn't compensate for this and lower it back down again, you run the risk of wearing out the injectors a lot quicker.

THe computer will adjust your fuel duing Closed Loop using the KAMs to bring it back as close as it can, which is fine, but at WOT it will be in OL and you will get the extra fuel that you need. But yeah it will put more strain on the injector thats for sure.

final5-0 · Nov 17, 2005

94-302-vert said:
Can we get away with lightning 42# injectors and a lightening MAF without the tune for now?

Absolutely ... Positively ... NOT

I can see why that Q gets asked over and over but the truth of it is this

Ford does not cal their mafs to inj size like the aftermarket folks such as ProM, C&L, and the like.

Takes a while to explain all this maf stuff.

If you wanna learn as opposed to just knowing the answer to your Q

You can find a good bit of info on basic maf operation by many more peeps than me on this site with detailed explanations.

btw ... Don 95Vert does a great job of making this difficult concept fairly easy to comprehend ...... much better than me, lol.

My site has some stuff that might help as well.

Grady

94-302-vert · Nov 18, 2005

Thanks Guys,

I do understand how a MAF works but since my car is still basically stock I haven't looked into what it takes to upgrade it.

So does that make our best bet ($$ wise) to get the 42# injectors and an aftermarket 42# MAF? To at least keep the car safe until a tune.

WhiteDevil · Nov 18, 2005

94-302-vert said:
Thanks Guys,

I do understand how a MAF works but since my car is still basically stock I haven't looked into what it takes to upgrade it.

So does that make our best bet ($$ wise) to get the 42# injectors and an aftermarket 42# MAF? To at least keep the car safe until a tune.

Are you going to be supercharged?

daves302gt · Nov 18, 2005

How about 38# inj/MAF as a fix?

What if a regular 38# inj set and a MAF cal'd for 38 pounders was installed(or a 30/30 or 36/36 or 42/42- like 94-302vert said) , then the MAF curve would hold true, right? people do this swap all the time to upsize injectors... Plus if i did run into problems my ignition has the MSD boost retard, so that could be tuned to eliminate detonation at boost if the mixture got too lean from the slightly unmatched load curve, right? Naturally a tune would fix the load, but this should be a safe way to get the fuel press back to stock and reduce the chance of fuel syst failure.d
BTW, i'm the guy he wrote the post about.

CManT1914 · Nov 18, 2005

dave, a maf that is "calibrated" for a certain size injector (like a 30ln maf with 30lb injectors) is not actually calibrated for them. What's really happening is, the calibration on the maf, is tricking the computer into thinking less air is entering the engine than actually is. Let's say you throw some 30lb injectors on a motor, with a matching maf. If you divide 19 by 30, you get roughly .6333. So the maf tricks the computer into thinking that only .6333% of the actual airflow is entering the engine. The PCM then cuts back fuel accordingly, which kind of compensates for the oversized injectors.

While this method works decently, the ONLY REAL way to have a safe tune, is a custom chip of somesort.

daves302gt · Nov 18, 2005

Right, i understand the trickery involved, but I'm usually a little skeptical of the actual need for a tune for SAFETY on a mild setup. I understand the tune can give more power, but the companies who make the re-cal'd MAFs have to err on the rich side, otherwise EVERYBODY who bought one would be burning up pistons from going lean! How many guys have you (ya'll?) heard of burning pistons from a mild s/c setup and a recal'd MAF injector combo? (thats a real question, not a jab)

CManT1914 · Nov 18, 2005

dave, not too many guys I've heard of have burned pistons........ but a TON of guys blow head gaskets. No matter what the parts, a h/c/i BLOWN setup is not mild. A tune is a MUST HAVE either way you slice it. Unless you like tearing your heads off every weekend.

19# injectors, Stock MAF, How much HP HP can they support

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