flynbludream

iTrader: (1)

Ok the G5 cam puts out some really good hp/tq numbers on a NA engine. As I understand it you need to have a cam with a bias toward the exhaust side if you want the best results from a turbo. Since this is how the G5 is setup, would it be a good choice for an FI setup with a turbo? TIA.

smokinHawk

iTrader: (48)

Most people are starting to say that the bias should be torward the intake side, which should spool the turbo well.

what are the specs

i went with and equal 22/224 cause i had conflicting information

BurnOut

iTrader: (1)

As someone who is going to go with the G5 when funds allow, I'll throw my $.02 in and say that it wouldn't really be a good FI cam.

It is ground on a 112 center, which is good for gaining power in the mid-range on these motors due to the valve overlap inducing a "pull-through" effect. Think of it kind of like opening two windows (on opposite sides of the room) in your house instead of one. With the two windows open, the "old" air (read: exhaust) has somewhere to go (out the second window) to make room for the "new" air (read: incoming fuel/air charge). Because of the greater overlap of a 112 LSA cam when compared to a 114 LSA cam (assuming all other things being equal), this "pull-through" is optimized at a lower charge velocity (read: RPM). Obviously, this concept results in a more complete cylinder fill; and therefore, more power. The cam on the 114 LSA doesn't reach it's "pull-through" sweet spot until charge velocity is higher (read: higher RPM).

What does all of that have to do with the G5 cam in a FI application?? Quite a bit, really. The G5 is ground on a 112 LSA, which is why it (and many other cams on a 112) produces such good numbers in the usable RPM range on N/A motors. The point that I am trying to make?? That on the LS1, a cam on a 112 LSA is a way to make sure that the cylinder gets as much fresh fuel/air as possible (within practical limits, of course).

FI applications negate the need for the "pull through" effect, as the fuel/air charge is pushed into the cylinder. Not only is the "pull-through" effect of the 112 LSA cam not needed, it is unwelcome. Because you are positively pressurizing the cylinders, a cam with more overlap will result in blowing fresh fuel/air charge out the exhaust. The result is wasted fuel, and lost boost.

All of that being said, with FI you generally want a wider LSA cam to reduce the "blow-through" effect that would result if a cam were used that had more overlap. In other words, I think I'd look for something on a 114 LSA (the G2 cam is offered on a 114), in addition to perhaps having a little bit less duration on the intake side.

Don't get me wrong, the G5 is an excellent cam that produces very nice results on N/A motors; I just think that there are better FI cams out there. My $.02...

<small>[ September 06, 2002, 03:21 PM: Message edited by: BurnOut ]</small>

Fenris Ulf

I would stay away from the G5, plenty of much better cams out there for NA and FI. I would suggest a XE-R 226/222 on a 114 lsa.

flynbludream

iTrader: (1)

Fenris, no flame intended but there is always a better cam than any other cam out there depending on your requirements, so you answer was not really helpful. Why would the cam that you suggested be good for an FI application?

Burnout, thanks for the response and explanation. I agree with your thinking. So would it mean that if you wanted to go with a higher boost application, you would want an even wider LSA? I guess ideally you would want an LSA set up so that you push out as much of the exhaust gasses and as little of the intake charge as possible right? So wouldn't that mean at higher boost i.e. more intake charge velocity, you would want your LSA to be greater? This would mean less overlap right?

Louis

iTrader: (7)

flynbludream,

I remember your story on the corvette forum, and the ride you got <img border="0" title="" alt="[Big Grin]" src="gr_grin.gif" /> I personally think that the G5 will work great. If you, and others dont think so, Call Lou up and have him get a custom one ground for your setup that will be better matched than anyother off the shelf cookie cutter cam. JMHO

Louis

BurnOut

iTrader: (1)

flynbludream- you're right on about the overlap. Something else to keep in mind, though, is how the engine performs while not under boost. As with most things, there has to be a compromise... the ideal cam for you may well end up with enough overlap to get the "pull-through" going in order to get the motor wrapped to a point where you're running a decent amount of boost. Obviously, this would also result in some "blow-through", as well.

For the most part, the whole reason for putting a bigger cam (bigger duration numbers, anyhow) in a motor is so it (the motor) can flow more air in the name of operation at higher RPM. With FI cars, airflow isn't really an issue... if you want more air/fuel into the cylinders, you can just increase the boost (read: airflow from the blower/turbo; there are a few side effects here, as well as practical limits) in order to make it happen. That being said, what we're after here is to get as much of the boost (as seen in the intake) into the cylinder as possible. Obviously, several things play into this, such as intake port shape/size, valve size, and yep, cam specs. You don't want RPM so much as you want as little of a pressure drop between the intake and the cylinder as possible. Look at some of the more serious Buick GN's... a lot of them don't spin past 5500 RPM or so. They don't need to. They are set up such that the turbo is capable of providing enough boost/airflow to make PLENTY of power by that engine speed. The sheet metal intakes, splayed valve heads, etc... are simply there to decrease the pressure drop between the turbo and the cylinders.

As you can tell, I am by no means an expert on FI LS1's; that's why all of my input has been pretty generic in nature. As Louis suggested, you'll be better off consulting someone who is more familiar with these motors on boost... that way you'll get an idea of what your specs are, as opposed to simply saying "I want more of this and less of that". <img border="0" title="" alt="[Smile]" src="gr_stretch.gif" />

Good luck, and let us all know how it goes.

flynbludream

iTrader: (1)

Louis,

Yeah that was me. Your dad is a class act. As soon as I am ready to get my car setup, you guys will be getting my business. Probably in the form of some low CR truck heads, custom cam and Cerra's single turbo kit. Maybe we can twist Godspeeds arm into helping out. <img border="0" title="" alt="[Big Grin]" src="gr_grin.gif" />

Burnout, thanks for the reply. I think we are running along the same thought patterns. The reason I am wondering why you would want so much intake duration is because it seems like with too much, you wouldn't have as much control over your cylinder pressures at a given amount of boost. It seems to me like you would want to regulate that with how much boost you are running. Just thinking out loud.