Exh. biased cams..

[BlackBandit]

I didn't get that from from nicks post. I got that he had messed around with different cams in the same engine but not that he had set up a control engine to test cams on. I have mad respect for nick and I agree with everything he said it just didn't sound like he had done what Ttipe suggested. If i'm wrong about that i'm sure nick will clarify.

 

[Turbo6Smackdown]

I agree. But if one came netted a quicker average time than another, that's good enough for me

 

[Turbo6Smackdown]

Woops. I meant, "if one cam netted a quicker time than another"

 

[BEATAV8]

subscribed... interesting thread!

 

[Turbo6Smackdown]

This statement bothers me a bit. I believe your guy is a good head porter but is shows me that he has no idea of why short lobes were used in the first place on turbo cams. Why would you not want to get the exhaust out of the motor? What he is implying is that having the exhaust lobe bigger opens the valve too soon? This tells me he has not bothered to check the event timing to see when things happen or keep up on current turbo technology. Mike

you don't just run a cam with a "bigger" exhaust lobe on turbocharged engines.
look at most of the best off the shelf cams for a small block chevy- or even any stock cam for a small block Chevy- and they will have more lift and duration on the exhaust side. people have been putting higher lift rocker arms on the exhast side of engines to help clear out the exhaust better since people started modifying engines for more power.

Tell him to just drop the compression ratio and run a large intake lobe and see how much more power he harnesses. You want to get as much of the inert gas out of the cylinder as possible without increasing reversion or you cant fill the cylinder with a fresh intake charge. What a dope. Fwiw i run a 218/224 (and its advanced a couple degrees so that must be really bad for it) in my hyd stock block engine. How much power has he made with his engines? Maybe he has the secret everyone is dying to find out. There is plenty you can do to chitty emissions heads that these engines came with stock. At least you werent fooled and came to the correct place to ask questions.

Oh boy.. Now I'm REALLY confused. Dan Strezo just told me the opposite. He said you want more on the intake side, than the exhaust side. He sells the 210/206 cam, saying it's way better than a 206/210... Now I'm lost lol.... Not only is this information not similar, it's the exact opposite lol. I see more physics classes in my near future...

 

[dr_frankenstein]

I personally dont think anyone period can just reccomend a cam for your car.

ultimately it should be the job of the builder to KNOW the combo and to have chosen his cam based on the particular goals.

the agrument of which lobe that needs to be bigger has no definitive answer. as no 2 motors will ever be exactly the same.

in my OPINION, if your running a healthy flowing head, then you can take advantage of better breathing and hold the intake open longer since it took less effort to properly exhaust the charge from a better flowing port. you will make more power this way,

However, if your head is poor breathing as many stock or lightly ported 8445s are, then you need to favor the exhaust to get the inert gasses out of that restrictive and high back pressure port. which leaves you with a cleaner bore for the fresh incoming charge. thus the engine produces more power.

since your forcing the engine to breathe with a turbo, getting whats shoved in, back out as best as possible is the game.... thus the cam is opposite for better flowing heads, cause now your tying to cram in, what you easily have the ability to evacuate.

to me, its a trade off of flow.

cause in my crazy mind.... boost is mearly a function of flow.

A.j.

 

[bison]

Oh boy.. Now I'm REALLY confused. Dan Strezo just told me the opposite. He said you want more on the intake side, than the exhaust side. He sells the 210/206 cam, saying it's way better than a 206/210... Now I'm lost lol.... Not only is this information not similar, it's the exact opposite lol. I see more physics classes in my near future...

I have a DLS cam that has a longer duration on the ex than the intake. I am running some heads that flow really well on the intake side though. This engine makes more power than just about anything out there that is for street use and a stock block. The entire engine is built around squeezing a lot of power out of a hyd cammed engine with a lot of backpressure.

 

[Turbo6Smackdown]

I got a bit of tech help from my builder. He said basically, that you're ok with an exhaust biased cam, with ****ty flowing heads (ie 8445's. Even really ported 8445's)
It's when you start running like, for example TA's street eliminator heads, that you may want to run an intake biased cam. I see now.
Whew, I was starting to go in reverse. Just when I thought I got some solid advice from this board, a buick god tells me the exact opposite lol. I was like "Now I'm no further ahead, than when I knew absolutely nothing!" It was like math. Once cancelled the other out and left me with nothing lol.
I think on track now.

 

[bison]

for example TA's street eliminator heads, that you may want to run an intake biased cam. I see now.

Oh really?

 

[BEATAV8]

Oh really?

Haha... come on Brian spill some beans. What are your thoughts? Same as what you posted above?

Some folks around here do appreciate your insight. :biggrin:

 

[DailyDrifter]

Some folks around here do appreciate your insight. :biggrin:

I don't................... he keeps asking me when he can plow my sister when I talk to him on the phone

 

[BEATAV8]

I don't................... he keeps asking me when he can plow my sister when I talk to him on the phone

Ya I heard that about him... I think he has some "special" relationships around here. :biggrin:

I can dig it.

 

[EVIL]

I don't................... he keeps asking me when he can plow my sister when I talk to him on the phone

Is she hot!

 

[Turbo6Smackdown]

Oh really?

Ahh ****.... Here we go. Do intake biased cams not help with reversion Bison? I did a little research yesterday on reversion, and I got the basic outline of what it is. This article said "That's why intake valves are bigger than exhaust valves" So I was like ohh yea yea. I see. And went on my way. They claimed the only real acid test to see how much your set up suffers from reversion, is by tossing a little water in the exhaust, and see if it makes it up into the combustion chambers. I don't know though, I'm only 1 day old to this phenomenon so, I still have tons of studying to do.

The more I read on internal combustion theory, the more I become sort of like a hypochondriac with my car. The more I know, the more I worry. I'm OCD with my car, and how it's set up. I don't want to make educated guesses based off of theories or myths perpetuated by other people. I want to be ABSOLUTELY positive, based off of physics. Something that's positively quantifiable. Empirical data. I want to know that it's all there, and the only thing holding it back, is my lack of tuning knowledge. Not only do I want all of my components to be matched 100%, but the knowledge of how to do so as well. I don't like guessing, I like knowing absolutely.
And I also see that these classes I'm taking in college, only cover the basics. The info is put out, and you're to take that as gospel. Because when I ask the instructor "why", all he can say is "Well, that's what I was taught." and has no real scientific way to prove it to me, to show me how it actually happened. That's only half an education as far as I'm concerned.
Is there such a place, that can formally teach me theory, and does research as well?

 

[dr_frankenstein]

you will never know unless you try.

sometimes just experimenting tells you all you need to know.

A.j.

 

[Turbo6Smackdown]

That is true, but for example, like in the compression/quench thread here. They talk about "If you raise your compression, this is what happens." Now, I could do that, and raise my own compression, and note the changes, but that still doesn't tell my why & how that actually happened.

 

[Joe 1320]

Maybe I'm wrong, but it seems overlap has to play a part in whether the intake or exhaust bias comes out the winner.

 

[Mike Licht]

Maybe I'm wrong, but it seems overlap has to play a part in whether the intake or exhaust bias comes out the winner.

You are correct!

 

[V6gofast]

Maybe I'm wrong, but it seems overlap has to play a part in whether the intake or exhaust bias comes out the winner.

The fact of the matter is a large percentage of the grinds used are of such
short duration and lift that the overlap is minimal and of little use in that respect.
The idea behind the verse durtion is to minimize the backwash in
the exhaust when the back pressure becomes excessively greater than boost.
It can easily be identified when you look into your intake manifold and it looks
like an exhaust port.

 

[Big Turbo Scott]

Just measure CHAMBER PRESSURE across the torque curve and leave it that.

Ive been waiting and looking for time/pressure data for a long time with no avail. Till then...

Scott