In what situation do you have to ....
In what situation do you have to ....
...Change to larger secondary injectors? I ran a search, but didnt come up with anything concrete.
If one were to do all reliability mods... as most of you know of ..... plus a little bit more would it be nessicary??
thanks in advance,
Edwin
If one were to do all reliability mods... as most of you know of ..... plus a little bit more would it be nessicary??
thanks in advance,
Edwin
Re: In what situation do you have to ....
Originally posted by CANRX7GX
...Change to larger secondary injectors?
...Change to larger secondary injectors?
Originally posted by SpeedKing
You'll need larger injectors if you'll be running over 12PSI
You'll need larger injectors if you'll be running over 12PSI
Originally posted by moehler
You only have to go to larger secondary injectors if you run boost levels over 12 psi.
You only have to go to larger secondary injectors if you run boost levels over 12 psi.
The only real way to know when you need larger secondaries is to monitor your A/F ratio and your injector duty cycle. You need to have larger secondaries when you need to add more fuel to your A/F ratio and your current sized injectors are maxed out.
That's definitely not 12 PSI on the stock twins as many people have run and continue to run 15 PSI on the stock fuel system without any problems.
Originally posted by Mahjik
Not true.
The only real way to know when you need larger secondaries is to monitor your A/F ratio and your injector duty cycle. You need to have larger secondaries when you need to add more fuel to your A/F ratio and your current sized injectors are maxed out.
That's definitely not 12 PSI on the stock twins as many people have run and continue to run 15 PSI on the stock fuel system without any problems.
Not true.
The only real way to know when you need larger secondaries is to monitor your A/F ratio and your injector duty cycle. You need to have larger secondaries when you need to add more fuel to your A/F ratio and your current sized injectors are maxed out.
That's definitely not 12 PSI on the stock twins as many people have run and continue to run 15 PSI on the stock fuel system without any problems.
Originally posted by SpeedKing
Over 12PSI, injector duty cycle typically is @ 90 - 95%. Assuming that, IMO, it would be safer to run bigger injectors at this point.
Over 12PSI, injector duty cycle typically is @ 90 - 95%. Assuming that, IMO, it would be safer to run bigger injectors at this point.
Originally posted by Wade
"Safely" is a relative term, safety doesn't have as much to do with the duty cycle of your injectors as it does everything else like charge temp, a:f ratio, timing. PFS is right on this one, think of PFS whatever you want (good or bad, I couldn't care less) but an FD can certainly make 400 rwhp with the stock injectors, it has been done.
I'm not sure why so many people freak out about hitting high duty cycles with stock injectors. Here are some things to consider:
1) I don't know anyone who has had an injector failure from driving the stock ones at high duty cycles, and a lot of people have done this for YEARS
2) I DO know several people who had enlarged injectors fail
3) There is no reason why an injector should fail just because it is staying open instead of clicking on and off several times per second... someone explain to me their reasoning on this!
4) It is the fuel injection companies that are telling you that beyond 85% duty is a bad thing, big surprise
5) I think beyond 85% *IS* a bad thing in a sense because it leaves no more room for mods if your a:f is exactly where you want it, you could lose tuning flexibility... but I wouldn't freak out about thinking my engine would blow because my duty cycles are high
6) High duty cycles only occur right near redline anyway, we're talking about a second or two when raking through the gears unless you are going for a top speed run at Bonneville
My conclusion is there is no need to upgrade injectors until there is a NEED to upgrade injectors. I run 15psi of boost with stock injectors and pressure and have been hitting 100% duty for almost 4 years now. If one of my injectors fails I'll know it and I highly doubt I'll blow my engine because of it.
Wade
"Safely" is a relative term, safety doesn't have as much to do with the duty cycle of your injectors as it does everything else like charge temp, a:f ratio, timing. PFS is right on this one, think of PFS whatever you want (good or bad, I couldn't care less) but an FD can certainly make 400 rwhp with the stock injectors, it has been done.
I'm not sure why so many people freak out about hitting high duty cycles with stock injectors. Here are some things to consider:
1) I don't know anyone who has had an injector failure from driving the stock ones at high duty cycles, and a lot of people have done this for YEARS
2) I DO know several people who had enlarged injectors fail
3) There is no reason why an injector should fail just because it is staying open instead of clicking on and off several times per second... someone explain to me their reasoning on this!
4) It is the fuel injection companies that are telling you that beyond 85% duty is a bad thing, big surprise
5) I think beyond 85% *IS* a bad thing in a sense because it leaves no more room for mods if your a:f is exactly where you want it, you could lose tuning flexibility... but I wouldn't freak out about thinking my engine would blow because my duty cycles are high
6) High duty cycles only occur right near redline anyway, we're talking about a second or two when raking through the gears unless you are going for a top speed run at Bonneville
My conclusion is there is no need to upgrade injectors until there is a NEED to upgrade injectors. I run 15psi of boost with stock injectors and pressure and have been hitting 100% duty for almost 4 years now. If one of my injectors fails I'll know it and I highly doubt I'll blow my engine because of it.
Wade
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Ganted this is only my opinion (and I've been wrong before 
), but if your hitting high duty cycles, you hitting the limit of what your car can handle. For instance if your at 95% injectory duty and have a boost spike on a cold day you could possibly max out the injectors and blow no matter how well tuned you car is or how well you understand your A/F ratios. I don't see any reason to max out the injectors if you don't have to... they're pretty cheap and worth while IMO.
Just b/c some people have done it for years with no problem doesn't mean that some else will be so lucky. I ran my car 11-13 psi on stock ECU and stock injectors for 3 months (I didn't know any better at the time
) with now problems, but that doesn't mean it's a good idea.
), but if your hitting high duty cycles, you hitting the limit of what your car can handle. For instance if your at 95% injectory duty and have a boost spike on a cold day you could possibly max out the injectors and blow no matter how well tuned you car is or how well you understand your A/F ratios. I don't see any reason to max out the injectors if you don't have to... they're pretty cheap and worth while IMO. Just b/c some people have done it for years with no problem doesn't mean that some else will be so lucky. I ran my car 11-13 psi on stock ECU and stock injectors for 3 months (I didn't know any better at the time
) with now problems, but that doesn't mean it's a good idea.
Originally posted by moehler
Ganted this is only my opinion (and I've been wrong before ), but if your hitting high duty cycles, you hitting the limit of what your car can handle. For instance if your at 95% injectory duty and have a boost spike on a cold day you could possibly max out the injectors and blow no matter how well tuned you car is or how well you understand your A/F ratios. I don't see any reason to max out the injectors if you don't have to... they're pretty cheap and worth while IMO.
Just b/c some people have done it for years with no problem doesn't mean that some else will be so lucky. I ran my car 11-13 psi on stock ECU and stock injectors for 3 months (I didn't know any better at the time ) with now problems, but that doesn't mean it's a good idea.
Ganted this is only my opinion (and I've been wrong before
), but if your hitting high duty cycles, you hitting the limit of what your car can handle. For instance if your at 95% injectory duty and have a boost spike on a cold day you could possibly max out the injectors and blow no matter how well tuned you car is or how well you understand your A/F ratios. I don't see any reason to max out the injectors if you don't have to... they're pretty cheap and worth while IMO. Just b/c some people have done it for years with no problem doesn't mean that some else will be so lucky. I ran my car 11-13 psi on stock ECU and stock injectors for 3 months (I didn't know any better at the time
) with now problems, but that doesn't mean it's a good idea.
If you have a boost spike, it doesn't matter if your injectors are already at 100% or at 60%. Your injectors are only supplying what the ECU is telling it to supply. So, if you spike to 17 PSI, it's not going to matter if you are running 1600cc or 850cc injectors; if you aren't tuned for that amount since the ECU won't know to throw more fuel at it anyway so it will still be flowing the same percentage.
A/F ratio is much more important than injector duty cycles. You can have 70% injector duty cycle and an extremely high A/F ratio which can cause detonation. However, you can have good A/F ratio and high duty cycles and there is no problem.
Originally posted by Mahjik
If you have a boost spike, it doesn't matter if your injectors are already at 100% or at 60%. Your injectors are only supplying what the ECU is telling it to supply. So, if you spike to 17 PSI, it's not going to matter if you are running 1600cc or 850cc injectors; if you aren't tuned for that amount since the ECU won't know to throw more fuel at it anyway so it will still be flowing the same percentage.
If you have a boost spike, it doesn't matter if your injectors are already at 100% or at 60%. Your injectors are only supplying what the ECU is telling it to supply. So, if you spike to 17 PSI, it's not going to matter if you are running 1600cc or 850cc injectors; if you aren't tuned for that amount since the ECU won't know to throw more fuel at it anyway so it will still be flowing the same percentage.
...
Originally posted by Mahjik
You should read a post by Wade (who probably has the most knowledge about the FD fuel system on the forum currently):
You should read a post by Wade (who probably has the most knowledge about the FD fuel system on the forum currently):
http://www.newwave.net/~flanham/wlan...l/fuelfaq.html
As he states at the end of point #1, "I would still recommend upgrading the fuel system if you regularly see over 85% injector duty." FWIW...
aka KingDrunk
Joined: Apr 2003
Posts: 738
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From: Atlanta, GA
also to add to mahjik's point, the reason the spike will occur at 100% or 60% duty is due to the lack of a mass air flow sensor. witout out 1, a set ammount of fuel is going to be fed to the engine regardless the ammount of air. if our cars had 1, tuning and moding would be much eaiser.
Originally posted by SpeedKing
As he states at the end of point #1, "I would still recommend upgrading the fuel system if you regularly see over 85% injector duty." FWIW...
As he states at the end of point #1, "I would still recommend upgrading the fuel system if you regularly see over 85% injector duty." FWIW...
Point still remains that high injector duty cycles are not as signifigantly important as the A/F ratio. The A/F ratio is 10x more important and should be correctly setup first. I've been around for a while and I've yet to hear someone blow their engine and directly relate it to high injector duty cycles. Blown engines from bad A/F ratios? You bet!
Last edited by Mahjik; Jan 13, 2004 at 08:31 AM.
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Originally posted by SpeedKing
Over 12PSI, injector duty cycle typically is @ 90 - 95%. Assuming that, IMO, it would be safer to run bigger injectors at this point.
Over 12PSI, injector duty cycle typically is @ 90 - 95%. Assuming that, IMO, it would be safer to run bigger injectors at this point.
Senior Member
Joined: Jan 2003
Posts: 253
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From: Madison, WI
While it is not really necessary to upgrade the secondaries to 1300 cc/min, I would like to point out that it's not like they're going to hurt your car. If spending the money is worth the piece of mind to someone even if there's not an actual need to do so, then I don't see the harm. For whatever reason some people would prefer to run low duty cycles and if the car will run fine then that's their business.
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