Hey, any HR guys spinning well past 7500rpms
01-16-2011, 10:27 AM
#65
comp 943 IS a PAC 1243 
I'm not running them yet, but i'll let ya know later this year. The advantage to that spring is MASS. You can set them up at 1.89 or so and run .750 net, which lets you use a +.100 valve instead of a .200 or .250, there's a few grams savings. It's a 1.55 spring vs a common 1.625 you'd set up at 2.00" which saves you another 30+ grams of spring + retainer mass. Obviously the entire spring is not moving, but lets say ~15 grams of moving mass saved. Also you can run a cheap 731 style titanium retainer from trick titanium for 200 bucks as well.
Those 20 grams saved are the equivalent of a hollow stem valve ($$$) but you can still run a solid stem severe duty and run the same rpm. On an 8000 rpm motor, every 10 grams you can take out of the valve side is 300 rpm or so. From the folks I've talked to that run the 1243, valve spring life is better and more consistant than their lifters! I'm giving away alot of my secrets here
but there's <10 members in this section who could actually use this data so whatever 
I'm not running them yet, but i'll let ya know later this year. The advantage to that spring is MASS. You can set them up at 1.89 or so and run .750 net, which lets you use a +.100 valve instead of a .200 or .250, there's a few grams savings. It's a 1.55 spring vs a common 1.625 you'd set up at 2.00" which saves you another 30+ grams of spring + retainer mass. Obviously the entire spring is not moving, but lets say ~15 grams of moving mass saved. Also you can run a cheap 731 style titanium retainer from trick titanium for 200 bucks as well.Those 20 grams saved are the equivalent of a hollow stem valve ($$$) but you can still run a solid stem severe duty and run the same rpm. On an 8000 rpm motor, every 10 grams you can take out of the valve side is 300 rpm or so. From the folks I've talked to that run the 1243, valve spring life is better and more consistant than their lifters! I'm giving away alot of my secrets here
but there's <10 members in this section who could actually use this data so whatever Thanks a ton - the day after I wrote that I got the results back from my shop and found that I can in fact run the springs
. To be on the safe side I had them checked for #'s at various lifts and coil bind and everything checks out good.I will have .046" coil bind clearance at max lift, plenty of room...looks like .73X" and 8000 RPMs is a go
.It's just another street car
. 
01-16-2011, 01:01 PM
#67
01-16-2011, 01:25 PM
#68
So, your response is confusing me...
01-16-2011, 02:40 PM
#69
Although the computer is programmed differently for the earliest of LT1s, coming form the factory using a UV erasable PROM chip, the computer hardware itself is subject to the same limitations as the other OBDI computers.
01-16-2011, 05:08 PM
#70
Like stated, that is due to batch-fire(well, technically bank fire) vs sequential, which does not matter at all. It purely effects idle manners, emissions, and low rpm fuel economy. During WOT all the injectors are basically open, and batch/sequential does not matter.
Although the computer is programmed differently for the earliest of LT1s, coming form the factory using a UV erasable PROM chip, the computer hardware itself is subject to the same limitations as the other OBDI computers.
Although the computer is programmed differently for the earliest of LT1s, coming form the factory using a UV erasable PROM chip, the computer hardware itself is subject to the same limitations as the other OBDI computers.
Also, wouldn't IPW affect max RPM if injector driver switching time was the limiter? Put some big *** injectors on for a short pulse width and more time to switch the drivers on and off?
01-16-2011, 05:33 PM
#71
So, you are saying the different computers have the same injector drivers? I know the physical effects of batch vs. sequential but I haven't had the various computers open to check hardware.
Also, wouldn't IPW affect max RPM if injector driver switching time was the limiter? Put some big *** injectors on for a short pulse width and more time to switch the drivers on and off?
Also, wouldn't IPW affect max RPM if injector driver switching time was the limiter? Put some big *** injectors on for a short pulse width and more time to switch the drivers on and off?
It is not a matter of the IWPs either, it is a matter of the computer not being able to order the injectors to fire X times over Y seconds. As RPM increases, no matter the injector size, it still has to fire the same amount of times, whether it is for a short pulse width or a long one. Not to mention big injectors have a horrible time atomizing fuel at very low IPWs. People like Gizmo have actually picked up vital time in SE cars by actually running SMALLER injectors at a higher PSI to help atomize the fuel.
Excuse my over-simplified explanations, just trying to word it in a way that makes sense. The "what" is a lot easier to explain then the "how".
Hopefully someone more "in the know" like Ed or Wicked will chime in.
01-16-2011, 05:50 PM
#73
Here is a graphical representation of what I am thinking.
Time available @ say 7000 rpm to fire injector: [__________]
I will use X for injector on time, I for ecu turn on, O for ecu turn off and _ as extra time.
Small injector @ 100% duty [IXXXXXXXXO]
Huge injector @ 50% duty [IXXXO_____]
The small injector model is out of time but the big one has ages of time left. If you get to the point where the time is like this [IO] or this [I] I think the engine would have leaned out a long time before.
Time available @ say 7000 rpm to fire injector: [__________]
I will use X for injector on time, I for ecu turn on, O for ecu turn off and _ as extra time.
Small injector @ 100% duty [IXXXXXXXXO]
Huge injector @ 50% duty [IXXXO_____]
The small injector model is out of time but the big one has ages of time left. If you get to the point where the time is like this [IO] or this [I] I think the engine would have leaned out a long time before.
01-16-2011, 06:26 PM
#74
Here is a graphical representation of what I am thinking.
Time available @ say 7000 rpm to fire injector: [__________]
I will use X for injector on time, I for ecu turn on, O for ecu turn off and _ as extra time.
Small injector @ 100% duty [IXXXXXXXXO]
Huge injector @ 50% duty [IXXXO_____]
The small injector model is out of time but the big one has ages of time left. If you get to the point where the time is like this [IO] or this [I] I think the engine would have leaned out a long time before.
Time available @ say 7000 rpm to fire injector: [__________]
I will use X for injector on time, I for ecu turn on, O for ecu turn off and _ as extra time.
Small injector @ 100% duty [IXXXXXXXXO]
Huge injector @ 50% duty [IXXXO_____]
The small injector model is out of time but the big one has ages of time left. If you get to the point where the time is like this [IO] or this [I] I think the engine would have leaned out a long time before.
.Duty cycle has nothing to do with the computer not being able to keep up with the injectors at 7000/7200 rpms, and is a totally different problem that has more to do with low speed drivability and idle problems with large injectors then it does high rpms
.Although they seem similar on the surface, not being able to control an excessively short pulsewidth(too large injector, too low fuel pressure) is different from not being able to fire an injector X times in X seconds(computer cannot keep up, cannot process information fast enough).
Hopefully Wicked can chime in, I know he has a deeper workings of the stock systems shortcomings and why exactly it has trouble at high rpms.
PS: I think I explained it pretty good that time, but I'm on my third Bacardi and Apple Juice so who knows how it'll look to me tomorrow
. I miss these discussion filled conversations that are now so often buried under "What exhaust should I run" or "Whats the biggest cam I can put in my stock LT1" 
. 
perhaps?
01-16-2011, 07:02 PM
#77
At XXXX RPMs you need the injector to fire the same amount of times over any given period of time no matter what the pulsewidth is. Pulsewidth is how MUCH fuel the injectors deliver per activation, but the RPM limit is due to how many TIMES the injector has to fire over a set period of time. Smaller or larger pulsewidths both fire the same amount of times at the same RPMs, and increasing the pulsewidth or injector size will not affect how many times it opens at 7000/7200 rpms .
Duty cycle has nothing to do with the computer not being able to keep up with the injectors at 7000/7200 rpms, and is a totally different problem that has more to do with low speed drivability and idle problems with large injectors then it does high rpms.
Although they seem similar on the surface, not being able to control an excessively short pulsewidth(too large injector, too low fuel pressure) is different from not being able to fire an injector X times in X seconds(computer cannot keep up, cannot process information fast enough).
Hopefully Wicked can chime in, I know he has a deeper workings of the stock systems shortcomings and why exactly it has trouble at high rpms.
PS: I think I explained it pretty good that time, but I'm on my third Bacardi and Apple Juice so who knows how it'll look to me tomorrow. I miss these discussion filled conversations that are now so often buried under "What exhaust should I run" or "Whats the biggest cam I can put in my stock LT1" .
.Duty cycle has nothing to do with the computer not being able to keep up with the injectors at 7000/7200 rpms, and is a totally different problem that has more to do with low speed drivability and idle problems with large injectors then it does high rpms
.Although they seem similar on the surface, not being able to control an excessively short pulsewidth(too large injector, too low fuel pressure) is different from not being able to fire an injector X times in X seconds(computer cannot keep up, cannot process information fast enough).
Hopefully Wicked can chime in, I know he has a deeper workings of the stock systems shortcomings and why exactly it has trouble at high rpms.
PS: I think I explained it pretty good that time, but I'm on my third Bacardi and Apple Juice so who knows how it'll look to me tomorrow
. I miss these discussion filled conversations that are now so often buried under "What exhaust should I run" or "Whats the biggest cam I can put in my stock LT1" .
Originally Posted by robsquikz28
this thread sux
01-16-2011, 07:26 PM
#78
.
01-16-2011, 08:49 PM
#80