Heads & Cam......Injectors?
05-07-2006, 02:17 AM
#1
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Heads & Cam......Injectors? Alright tried searching this and couldnt realy come up with anything. Anyways i'm putting a cam(specs in sig), dart 225's, and upping the DCR to 8.56, so i'm curious to know if my stock injectors will be up to the task.
Thanks
Justin
Oh yea i have a walbro 255, also.
Thanks
Justin
Oh yea i have a walbro 255, also.
05-07-2006, 02:35 AM
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sorry just relized this would prolly be better in the fuel and injection section. If one of you mods could move this for me that would be great.
Thanks
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05-07-2006, 10:37 AM
#8
Some people get away with the 28# injectors at up to 450 rwhp. But you risk going lean and the injectors are well over the 80% duty cycle that is a recommended safe maximum.
I would go with the svo 30's (something like 34.6lbs at ls1 fuel pressure)unless you are planning on some nitrous later. This is what I am using.
It is best to go as close to what you need as possible. An injector that is way too large wont work as well for various reasons which I dont remember right off hand.
The svo 42# green tops would also work well. But the 30's are probably closer to what you need.
You can also find some good deals on these in the for sale section. I got mine for 150 shipped. Make sure they are the red ones.
I would go with the svo 30's (something like 34.6lbs at ls1 fuel pressure)unless you are planning on some nitrous later. This is what I am using.
It is best to go as close to what you need as possible. An injector that is way too large wont work as well for various reasons which I dont remember right off hand.
The svo 42# green tops would also work well. But the 30's are probably closer to what you need.
You can also find some good deals on these in the for sale section. I got mine for 150 shipped. Make sure they are the red ones.
05-07-2006, 02:29 PM
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thanks a lot guys, I figured i would need some bigger injectors i just wanted to make sure.
Anyways svo 30's seem to be my best bet from what i'm gathering then?
Anyways svo 30's seem to be my best bet from what i'm gathering then?
05-07-2006, 04:04 PM
#11
i have dyno graphs and logs from a H/C car that puts down about 430rwhp (through a 12 bolt) on svo 30s, and it's so maxed out, that you see the power on the dyno graph flutter past 5500rpm.
30s are perfect for simple bolton only, or tiny cam applications, but i wouldn't use them for anything beyond that. i only have a z06 cam on stock headers/heads and i'm at 85% duty cycle with the 30s at 6200rpm.
don't believe the hype, just log and see for yourself, and make sure your injectors aren't miscalibrated either.
30s are perfect for simple bolton only, or tiny cam applications, but i wouldn't use them for anything beyond that. i only have a z06 cam on stock headers/heads and i'm at 85% duty cycle with the 30s at 6200rpm.
don't believe the hype, just log and see for yourself, and make sure your injectors aren't miscalibrated either.
05-07-2006, 04:25 PM
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thanks a lot for the heads up, so maybe the lucas 42lb or somthing simular. Maybe i'll give my tuner a call tomorrow and ask him what he thinks.
Justin
Justin
05-07-2006, 08:16 PM
#13
Every car is different.
Many h/c cars run the #30 svo's and they work great.
That is what I am running and dont expect any problems.
Hell...some people even use the stockers on h/c.
Its up to you.
Their is a nice injector flow calculator that would probably help. Dont know where it is though. Maybe someone else knows.
Many h/c cars run the #30 svo's and they work great.
That is what I am running and dont expect any problems.
Hell...some people even use the stockers on h/c.
Its up to you.
Their is a nice injector flow calculator that would probably help. Dont know where it is though. Maybe someone else knows.
05-07-2006, 08:43 PM
#14
'work great' is a relative term. every time someone with such a combo shows up i ask them for logs, and they all either get really quiet or just don't have them. the few h/c cars i tuned myself and logged the hell out of they all were way past svo30s' range. if your h/c isn't maxing out 30s, you're missing a lot of power somewhere.
think about it, where does power come from? air and fuel. air you get 'for free' but fuel you have to deliever. to produce 400hp from a controlled explosion, you gotta have approximately the same amount of fuel and air. whether they get there by the means of big cubes and many cylinders or high boost and few cylinders, it doesn't matter.
and that nice injector flow calculator is mine, you're welcome
think about it, where does power come from? air and fuel. air you get 'for free' but fuel you have to deliever. to produce 400hp from a controlled explosion, you gotta have approximately the same amount of fuel and air. whether they get there by the means of big cubes and many cylinders or high boost and few cylinders, it doesn't matter.
and that nice injector flow calculator is mine, you're welcome
05-08-2006, 08:27 AM
#16
Well...according to the fuel injector calculator the svo 30 injector will support 512 crankshaft horsepower before it is at 80% duty cycle.
Assuming they run at 34.6 lbs in an ls1 system, which is what I have always been told.
It also says 450 crank horsepower will be supported at 80% duty cycle with a straight up 30lb injector.
If you use 90 percent duty cycle. A regular 30lb injector will support 500 crank horsepower.
Here is the calc I used...http://www.rceng.com/technical.htm
Assuming they run at 34.6 lbs in an ls1 system, which is what I have always been told.
It also says 450 crank horsepower will be supported at 80% duty cycle with a straight up 30lb injector.
If you use 90 percent duty cycle. A regular 30lb injector will support 500 crank horsepower.
Here is the calc I used...http://www.rceng.com/technical.htm
05-08-2006, 10:24 AM
#17
so you're saying that a calculator where you plug ballpark numbers is better than real world numbers that you get out of a purpose built scanner? do you also know that injector pulse width is useless to describe ability of an injector, until you take rpm into consideration? at 6000rpm 20ms is your time window to do all your fueling in. at 8000rpm it goes down to like 15ms. look at pulse width and you won't see it, look at duty cycle and it will show you some scary numbers.
in theory, there is no difference between theory and practice. in practice, there is.
in theory, there is no difference between theory and practice. in practice, there is.
05-08-2006, 04:04 PM
#18
Just thought it was kinda strange that a car making less than 500 at the crank was causing the injectors to go lean at 5500 rpm...,.I have never heard of such a thing. People have run the stockers on that kind of power....they are well over the duty cycle...but the power is supported.
The 405 hp zo6 also comes with only 28.8 lb injectors. A guy on this board just did dart 205s and an f14 or 15 cam...put down about 450 to the wheels and has no problems with going lean. And those run about 5lbs less than an svo 30
That is why I said every car is different...I am not doubting that you got those results and you obviously know more than I do about fuel injection systems.
But from what I have gathered and seen people run on this board I can only assume that the svo 30 would support his mods. Is it possible they wont?...sure. But I am betting they will be fine for most.
Ill be running them and have a graph up in june...hopefully the car wont go lean. If it does I guess Ill have to get some 42's. But I highly doubt it...someone just ran almost my same exact package on stock injectors and put down about 440 to the wheels...and didnt go lean.
The 405 hp zo6 also comes with only 28.8 lb injectors. A guy on this board just did dart 205s and an f14 or 15 cam...put down about 450 to the wheels and has no problems with going lean. And those run about 5lbs less than an svo 30
That is why I said every car is different...I am not doubting that you got those results and you obviously know more than I do about fuel injection systems.
But from what I have gathered and seen people run on this board I can only assume that the svo 30 would support his mods. Is it possible they wont?...sure. But I am betting they will be fine for most.
Ill be running them and have a graph up in june...hopefully the car wont go lean. If it does I guess Ill have to get some 42's. But I highly doubt it...someone just ran almost my same exact package on stock injectors and put down about 440 to the wheels...and didnt go lean.
05-08-2006, 05:19 PM
#19
From UltraZLS1
"But you risk going lean and the injectors are well over the 80% duty cycle that is a recommended safe maximum."
Even if a car doesn't go lean on too small of injectors on the dyno, and you are at say 115%, the chance is it will down the road. For $200-$300, do you really want to risk a $10,000 motor on that? Wouldn't you rather play it safe than saving a few bucks??
"But you risk going lean and the injectors are well over the 80% duty cycle that is a recommended safe maximum."
Even if a car doesn't go lean on too small of injectors on the dyno, and you are at say 115%, the chance is it will down the road. For $200-$300, do you really want to risk a $10,000 motor on that? Wouldn't you rather play it safe than saving a few bucks??
