I'm interested in getting a few new fuel components and of course injectors are on the list. Is there such a thing as getting too large of injectors? If so, what would be the reason that it's overkill?
Injector sizes
- Thread starter casper35404
- Start date
yes there is.
too big means more fuel overall meaning that right off the bat you will be injecting more fuel per injector pulse. Easy way to flood out an engine
too big means more fuel overall meaning that right off the bat you will be injecting more fuel per injector pulse. Easy way to flood out an engine
Thanks for that answer. Does anybody know the recommended HP range for the different injector sizes?
Old School rule of thumb:
100CC per 100hp.
So our stock 440cc injectors can hold UP TO 440hp at the CRANK ( not whp)
550cc=550hp
750cc=750hp and so on.
-Jonathan
100CC per 100hp.
So our stock 440cc injectors can hold UP TO 440hp at the CRANK ( not whp)
550cc=550hp
750cc=750hp and so on.
-Jonathan
Ok. Thanks for that info. That gives me the upper end of the range of HP. How about the lower end? Does anybody have any info on the recommended lowest HP of a certain injector?
Its kind of vague really...all depends on the duty cycle the injectors can run at. Some are better at lower cycles than others. The bigger you go though the richer they will run on the bottem period.
BUT:
If you have a tuning mechanism i.e. the Apexi SAFC, you can turn down the duty cycle in the given rev range.
-Jonathan
PS: Just put it this way, the car will run richer at idle if you upgrade the injector sizes, period. But as I said you can combat that "groggy" idle by using a fuel tuning computer ( SAFC ).
BUT:
If you have a tuning mechanism i.e. the Apexi SAFC, you can turn down the duty cycle in the given rev range.
-Jonathan
PS: Just put it this way, the car will run richer at idle if you upgrade the injector sizes, period. But as I said you can combat that "groggy" idle by using a fuel tuning computer ( SAFC ).
I was planning on getting the MAFTpro setup and either 550CC or 720CC injectors. Does anybody see me having any problems with that?
Well you might as well accept that you are NOT going to have a nice idling car!
Set your idle high!
Put that comment this way:
I had ( still have ) a Lexus AFM. It made the car run slightly richer at idle so it was significantly more "lumpy" at idle ( people thought I had cams LOL )....so I turned the idle up to 1000rpm and eliminated the tendancy of the car wanting to die at idle.
NOTE: I have a 1987 turbo with the adjustable idle/air control valve (post 89 cars do NOT ).
What cams are you going to go with? Duration/Lift?
Reason I ask is that with cams you could be changing the scenario.
-Jonathan
Set your idle high!
Put that comment this way:
I had ( still have ) a Lexus AFM. It made the car run slightly richer at idle so it was significantly more "lumpy" at idle ( people thought I had cams LOL )....so I turned the idle up to 1000rpm and eliminated the tendancy of the car wanting to die at idle.
NOTE: I have a 1987 turbo with the adjustable idle/air control valve (post 89 cars do NOT ).
What cams are you going to go with? Duration/Lift?
Reason I ask is that with cams you could be changing the scenario.
-Jonathan
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I'm trying to go for 550HP eventually. I'm not sure about cams. For one I don't know about the differences between all of them and nobody that I've talked to says that I wouldn't need to change my cams. I know that 550s would be all I would need, but I don't want them to be maxed out.
Believe me, the stock cams are 200 degree duration.
I see that you might not understand fully how cams are chosen...but here is my interpretation.
Out of 360 degrees of rotation on a cam, you need a "lifting" point to push the valve open.
Our stock duration is 200 degrees. That means that out of 360 degrees, the cam is open 200 degrees of the time.
Imagine running REALLY FAST ( simulating HIGH rpms, the reason you need cams). If you breath fast...your not going to fair very well...if you have a slow deep breath...you will pretty much be fine.
Fast breath ( small duration...good for low end torque)
Slow breath ( large duration ...good for high end power)
So all in all, the larger the duration you can get the better the engine will breath at high rpms.
Maybe you have noticed the car "stops pulling" at about 5500rpm?
Now lift of the cam is another thing. Thats how far the valve is pushed open via the litteral height of the cam.
I am opting for the stock lift ( so I do not have to change the valve shims out for thicker ones. ) but higher duration. 256 is what I am aiming for.
To make 550hp, you can do it on stock cams...but the boost you will be pushing...you can take some stress off the turbo and save fuel if you add cams.
They can make up to 50hp on the stock system, JUST CAMS ALONE!!!
So I think you may want to consider the cams!
-Jonathan
PS: If any of this is WRONG PLEASE CORRECT ME GUYS!
I see that you might not understand fully how cams are chosen...but here is my interpretation.
Out of 360 degrees of rotation on a cam, you need a "lifting" point to push the valve open.
Our stock duration is 200 degrees. That means that out of 360 degrees, the cam is open 200 degrees of the time.
Imagine running REALLY FAST ( simulating HIGH rpms, the reason you need cams). If you breath fast...your not going to fair very well...if you have a slow deep breath...you will pretty much be fine.
Fast breath ( small duration...good for low end torque)
Slow breath ( large duration ...good for high end power)
So all in all, the larger the duration you can get the better the engine will breath at high rpms.
Maybe you have noticed the car "stops pulling" at about 5500rpm?
Now lift of the cam is another thing. Thats how far the valve is pushed open via the litteral height of the cam.
I am opting for the stock lift ( so I do not have to change the valve shims out for thicker ones. ) but higher duration. 256 is what I am aiming for.
To make 550hp, you can do it on stock cams...but the boost you will be pushing...you can take some stress off the turbo and save fuel if you add cams.
They can make up to 50hp on the stock system, JUST CAMS ALONE!!!
So I think you may want to consider the cams!
-Jonathan
PS: If any of this is WRONG PLEASE CORRECT ME GUYS!
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I've always heard that for turbo, the better cam would be a high lift/short duration. You don't want too long of a duration because there will be more overlap between the intake and exhaust cams, where turbo pressure may be lost. The high lift, because you're forcing air into the cylinder so velocity isn't as critical as n/a. you want volume, which is achieved by the bigger opening.
and to keep this somewhat on topic, why is it that injectors are always rated by hp? peak torque is when the most fuel is required, is it not? so what if an engine makes 400tq but it quickly plumets to only 250hp would 250cc injectors deliver enough fuel? not likely. on the other hand i've seen 400hp from 440cc injectors on a 1.6 honda motor (not very much torque but it holds it to 9k). mind you thats on 4 injectors...
and to keep this somewhat on topic, why is it that injectors are always rated by hp? peak torque is when the most fuel is required, is it not? so what if an engine makes 400tq but it quickly plumets to only 250hp would 250cc injectors deliver enough fuel? not likely. on the other hand i've seen 400hp from 440cc injectors on a 1.6 honda motor (not very much torque but it holds it to 9k). mind you thats on 4 injectors...
Which is why the stock GTE cam was ground the way it was.
Horsepower is how fast the torque is being used, or total work being done. With more horsepower, the injector has to be on longer or more frequently.
You need to try and explain your question better. Horsepower is a function of engine torque and RPM. The airflow characteristics of the cylinder head, camshaft timing, and intake manifold design determine when peak torque and horsepower will occur.
yes, it needs to open/close faster @ higher rpm, but but that's irrelevant. flow, as measured by the mfg, is tested at 100% duty at a predetermined pressure, not by how fast it can open/close. duty cycle is higher at peak torque than at redline, where torque declines, is it not?
Let me give it another try. Suppose you want a quick spooling, small turbo that maxes out low in the rpm range and peaks @ 400tq, but runs out of breath up top, and only makes 200tq at 6500rpm, that translates to only ~250hp. Using the formula "100cc=100hp" mentioned above, you'd only need 250cc injectors. I really doubt that will supply enough fuel.
Let me give it another try. Suppose you want a quick spooling, small turbo that maxes out low in the rpm range and peaks @ 400tq, but runs out of breath up top, and only makes 200tq at 6500rpm, that translates to only ~250hp. Using the formula "100cc=100hp" mentioned above, you'd only need 250cc injectors. I really doubt that will supply enough fuel.
diy guy said:
nope
the most power is developed at torque peak but you can go WELL above and beyond that point of consumption by revving the hell out of the motor.
figgie said:
My exact thoughts. The higher the revs, the more boost your pushing, the more fuel you need.
And its better to run rich at high rpm's anyways because of the immense heat imposed on the piston/combustion chamber!
-Jonathan
siman said:
and to add
that is the reason why you want to keep revs DOWN. It helps in fuel economy
figgie said:and to add
that is the reason why you want to keep revs DOWN. It helps in fuel economy
Word!:biglaugh:
Either way, I still find that the CC=HP "formula" if you will is about right. You should not really worry about how LOW of a HP number your injectors can run...but how high.
-Jonathan
I think I may opt for the 660CC venom injectors. Would that still be overkill if I tuned it correctly on a near-stock setup?