347 stroker
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It sure is when you're at maxed out levels.
Couldn't care less what it makes on a dyno. I tuned myself on the street via a PMS and a WB
Nice try though 
SVTCobra306
New Member
..According to math, 30's should be good to close to 375HP at .50 BSFC assuming 80 percent duty cycle. Considering that most street motors aren't exactly at .50 BSFC they probably aren't good for quite that.. however at less than 350 RWHP I ain't skeered yet.. Besides it only sees the track once every couple months. That's what my carb'ed race car is for 
SVTCobra306
New Member
Crap... Why do I always think in RWHP.. I guess when I upgrade my cam I will also upgrade injectors..
It sure is when you're at maxed out levels.
Couldn't care less what it makes on a dyno. I tuned myself on the street via a PMS and a WB
No it isn't. Higher the duty cycle, the better the mixture. The injector itself doesn't much care how long it stays open. And the butt dyno isn't that accurate of a device.
Kurt
Black95GTS
Active Member
Never heard this, can you go into more detail?
I know the argument that over sizing injectors makes it harder to tune, due to the larger injector opening and shutting at an increased rate of speed. But a competent tuner can compensate for this.
I mean... I compensated for this, doing my cousin's 347 at the age of 21 in my driveway with a laptop and LM-1. The almighty 42 pound injectors and LMAF combo.
Under WOT, you are still getting the same amount of air / fuel correct? You don't tune the mixture with the injector, that's what the computer and wide band are for. If you're running a smaller injector at a high duty cycle versus a larger injector at a low one, if the A/F is where you want it then that's all there is to it.
Import Performance Parts - How to Choose the Correct Fuel Injector
Great read specifically using the 5.0 as an example. All kinds of formula here.
Adam
I can say this about injectors and working them at and beyond the limit
when talking fuel pressure
Several years ago, a fellow who was a tech guy for Bosch used to hang
around on the various tuning sites
He basically said anything over the limit of pressure the inj was designed
for can alter the spray pattern
Several peeps challenged his info and he later posted a very in depth
tech white page kind of article showing just what he said was so
I used to have it but my old tuning laptop crashed and the file was lost
Now ... about duty cycle .......
Just look at Ford OEM applications such as
NA Stangs
Blown Stangs
Lightnings
Turbo T Birds
etc
I'd bet you won't find any of em running at 100% duty cycle
What is the reasoning many peeps seem to want to run an inj
at or beyond its limit
I feel that kind of thinking is a throw back from the old Fox body days
of mechanical fuel adjustment using AFPR's and mechanical spark
adjustment with dizzy twisting
Back in those days when you used 30's or larger ... (well, these days
too ... but, back then ... not that much pcm tuning was being done)
You usually had over rich issues at idle and cruise cause the pulse width
is quite small during those driving conditions and those big inj's spit
out too much fuel
These days with pcm optimization, you can easily deal with that
old time problem
Grady
when talking fuel pressure
Several years ago, a fellow who was a tech guy for Bosch used to hang
around on the various tuning sites
He basically said anything over the limit of pressure the inj was designed
for can alter the spray pattern
Several peeps challenged his info and he later posted a very in depth
tech white page kind of article showing just what he said was so
I used to have it but my old tuning laptop crashed and the file was lost
Now ... about duty cycle .......
Just look at Ford OEM applications such as
NA Stangs
Blown Stangs
Lightnings
Turbo T Birds
etc
I'd bet you won't find any of em running at 100% duty cycle
What is the reasoning many peeps seem to want to run an inj
at or beyond its limit
I feel that kind of thinking is a throw back from the old Fox body days
of mechanical fuel adjustment using AFPR's and mechanical spark
adjustment with dizzy twisting
Back in those days when you used 30's or larger ... (well, these days
too ... but, back then ... not that much pcm tuning was being done)
You usually had over rich issues at idle and cruise cause the pulse width
is quite small during those driving conditions and those big inj's spit
out too much fuel
These days with pcm optimization, you can easily deal with that
old time problem
Grady
Black95GTS
Active Member
I can say this about injectors and working them at and beyond the limit
when talking fuel pressure
Several years ago, a fellow who was a tech guy for Bosch used to hang
around on the various tuning sites
He basically said anything over the limit of pressure the inj was designed
for can alter the spray pattern
Several peeps challenged his info and he later posted a very in depth
tech white page kind of article showing just what he said was so
I used to have it but my old tuning laptop crashed and the file was lost
Now ... about duty cycle .......
Just look at Ford OEM applications such as
NA Stangs
Blown Stangs
Lightnings
Turbo T Birds
etc
I'd bet you won't find any of em running at 100% duty cycle
What is the reasoning many peeps seem to want to run an inj
at or beyond its limit
I feel that kind of thinking is a throw back from the old Fox body days
of mechanical fuel adjustment using AFPR's and mechanical spark
adjustment with dizzy twisting
Back in those days when you used 30's or larger ... (well, these days
too ... but, back then ... not that much pcm tuning was being done)
You usually had over rich issues at idle and cruise cause the pulse width
is quite small during those driving conditions and those big inj's spit
out too much fuel
These days with pcm optimization, you can easily deal with that
old time problem
Grady
I'm with you on this one.... if and when I get another mustang the injector's won't see over 80 percent duty cycle at WOT. I do the same thing when I design transmission lines. Say you need to send 600 amps down the line... you don't pick out cable that is sized for 600, you go up to 700 or 800 amp rated conductor.
Unfortunately I bought a house in January and now I am more concerned with repaving driveways then putting mustangs in them. Thus, do as I say not as I do.
Paul, I have never understood your car. It seems to buck all kinds of rules, both internet opinion and legit math. If I had your setup it would have 36s (if I could find them) or 42s.
Adam
"Butt dyno," = tuning the car based on how it feels in the seat of your pants vs. tuning it on a dyno.
This thing of running really big injectors is kind of a new thing. Back in the old days, for us old farts, we used to make do with nothing bigger than 30lbers. Anything bigger than that was so expensive, you just did without. I think the whole thing comes from the availability of larger injectors at cheaper prices. Theoretically, if the injector sprays for a longer period of time, then it mixes the fuel more evenly with the air, vs a larger injector that sprays for a shorter period of time. I think big injectors are overated. I mean, I've been making almost 600hp with the same 30lbers I've had for almost 10 years now. So, if they have made good power, and run fine for 10 years and 80,000+ miles, I don't see anything wrong with that. And I don't know how much the spray pattern changes, but I can definately say that I make good power with 95psi on the injector, so I don't see any reason to go bigger. So maybe going to be a bigger injector gives some people a sense of security, but I've seen enough small injector cars that work just fine.
Kurt
This thing of running really big injectors is kind of a new thing. Back in the old days, for us old farts, we used to make do with nothing bigger than 30lbers. Anything bigger than that was so expensive, you just did without. I think the whole thing comes from the availability of larger injectors at cheaper prices. Theoretically, if the injector sprays for a longer period of time, then it mixes the fuel more evenly with the air, vs a larger injector that sprays for a shorter period of time. I think big injectors are overated. I mean, I've been making almost 600hp with the same 30lbers I've had for almost 10 years now. So, if they have made good power, and run fine for 10 years and 80,000+ miles, I don't see anything wrong with that. And I don't know how much the spray pattern changes, but I can definately say that I make good power with 95psi on the injector, so I don't see any reason to go bigger. So maybe going to be a bigger injector gives some people a sense of security, but I've seen enough small injector cars that work just fine.
Kurt
My commen sense tells me it is foolish to argue with someone who has
successfully done a thing like you have done Kurt
I feel it is not fair to compare what you have done and what I've done
They are different methods :Word:
And ... We all know there are different ways to ... Skin a Cat
Grady
LOL! Thanks Adam. I see absolutely no reason to go any higher with my injectors as I can see and datalog real time the injector duty cycle. There is no doubt that you get better atomization of the fuel when the pressure is higher than when it is lower. In an NA combo I'll always run an injector that just gets the job done. Many people I trust; including racers, builders, and fellow enthusiast feel the same way I do. Why would you want to run a 42lb injector on a car like mine and have to either cut the pulse width way down, or the fuel pressure, or both as is often the case? I'd rather run the injector near its peak and at a sufficient pressure so that when it opens, the fuel is forced out and atomizes efficiently and correctly. I see no reason why more power couldn't be made doing it this way than to have a big lazy injector in there. I ran the 24's on my setup for 2 years without a single issue with the AFR165 heads.
In a boosted car I will always go a bit the opposite way on my feelings about injectors though. Because so much more can go wrong, especially in a turbo car (ie boost creep/boost spike) I plan to put an injector on the car with a bit more 'wiggle" room if you will than what I feel comfortable doing with my NA stuff.
Black95GTS
Active Member
I wonder what the difference is though? When is there too much pressure or too little? How much can you push the injector past spec? You would have to weigh the risk versus reward of better atomization versus burning an injector out at 7000 rpms.
:OT:
So..... buy some 90s, bolt that turbo on, and get your 9 second license.
Adam
Thanks for everyone's comments. I have been gone a few days, so I'm slow getting back to work. Had to head 1,000 miles north to check on my wooded property. Had a interesting encounter with a 350Z up in Kentucky. My G-37 did alright for a while, but I'm not into highway racing or street racing. Anyway thanks for the comments.
Looks like I will be ordering 3 shortblocks for myself and a couple of guys that want one as well.
Looks like I will be ordering 3 shortblocks for myself and a couple of guys that want one as well.
Excellent post. Thanks for the explanation. I know several tuners that will agree with you. I didn't understand why until now.
Well I purchased the block and a DIY stroker kit about 6 weeks ago, still waiting for delivery.
Items purchased so far. 1. scat crank 2. forged piston I beam 3. rings etc with kit. 4. afr 185 heads #1388. 4. flywheel 5. summit perfromance timing set. 6. crane pro street 1.6 roller rockers and hardened push rods. 6. Melhing oil pump and rod 7. milidon high flow alum. h20 pump. 8. about 100 different frigging gaskets. 9. Holly systemaxII intake. 10. 90mm maf. 11. arp head stud kit and bolt kit for oil pan. 12.plastigauge set. 13. end gap ring grinder. 14. comp cam xe282hr. 15. 255 lph whalboro fuel pump, installed. Thanks for the write ups on how to. 16. Redid the carpeting on the inside. 17. old motor and drive train pulled.
Still to buy: 1 throttle body 2. possible fuel rail. 3. 36# injectors 4. mini starter. 5. intake bolts 6. cam wheel to degree the cam. 7. more friggin gaskets.
Haven't even touched the drive train yet. Maybe the motor will get here by July so the shop will only be 145 degrees instead of 99 degrees F.
Plan on getting a tune at this place, down the road. Distributor of the Coolest Parts for the FFR They must of heard me pounding the key board, just received confirmation of shipment three minutes ago
Items purchased so far. 1. scat crank 2. forged piston I beam 3. rings etc with kit. 4. afr 185 heads #1388. 4. flywheel 5. summit perfromance timing set. 6. crane pro street 1.6 roller rockers and hardened push rods. 6. Melhing oil pump and rod 7. milidon high flow alum. h20 pump. 8. about 100 different frigging gaskets. 9. Holly systemaxII intake. 10. 90mm maf. 11. arp head stud kit and bolt kit for oil pan. 12.plastigauge set. 13. end gap ring grinder. 14. comp cam xe282hr. 15. 255 lph whalboro fuel pump, installed. Thanks for the write ups on how to. 16. Redid the carpeting on the inside. 17. old motor and drive train pulled.
Still to buy: 1 throttle body 2. possible fuel rail. 3. 36# injectors 4. mini starter. 5. intake bolts 6. cam wheel to degree the cam. 7. more friggin gaskets.
Haven't even touched the drive train yet. Maybe the motor will get here by July so the shop will only be 145 degrees instead of 99 degrees F.
Plan on getting a tune at this place, down the road. Distributor of the Coolest Parts for the FFR They must of heard me pounding the key board, just received confirmation of shipment three minutes ago
Black95GTS
Active Member
Good luck! Make sure to post pics as you go about your build. You might have a hard time finding the 36 pounders as I believe they are not made anymore. The 42s cost about the same and are readily available, FYI.
Adam
Adam
95Vert383AOD
15 Year Member
BTW i have 36's in my 383. I need 42's ....Picked them up a couple of years ago and they're too small. I've been shopping 42's lately so lemme know.
Chris
Chris
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