dj55b

iTrader: (2)

back to the sleeves look at it like this maybe. Getting flame suit on first. Alright think of that sleeve as an intake valve angle on a piston engine. Do you ever seel any valves positioned at 90 degrees? As in have the rod then and basically have a round plate just attached in there. As oppose to a smoothed out pattern. If you wish to see difference in flow (just various angles) look here:

http://www.carcraft.com/techarticles...gle/index.html

Should tell you the smoother the air the more flow that can be driven to the engine hence increasing power. Get where i'm going with this though?

Roen

iTrader: (2)

I don't deny that the theory behind it is sound. Just like more exhaust gas scavenging should increase power? Empirically, doesn't do squat on stock engines though, I'm afraid, in real life.

Unless, of course, you have a dyno graph?

dj55b

iTrader: (2)

About the exhaut scavenging ... thats basically how you have a good/bad headers. THe better ones produce a more "controlled" scavenging effect and thus making more HP out of an engine than other ones. I say controlled because they all basically provide a scavenging effect (that is headers not manifolds). I could be wrong on that one but thats the way I see it,.

Roen

iTrader: (2)

anything that collect will provide the scavenging effect, turbulence in the collector, length of tube before collector and other factors all play a part in it.

The point is, everything should be taken with a grain of salt, unless it is an axiom or unless you have empirical proof.

anewconvert

iTrader: (1)

An equal length header will always provide some sort of scavenging. The difference between headers is where the peak flow and scavenging happens. A small diameter long(er) primary header will see its best flow at lower rpms. A large diameter short(er) primary will see its power up high. Mixing and matching those simple properties, and then adding in bends and collectors and coatings etc wis what seperates a good header from a bad one. Its really based on your application. Also, by short and long I am not refering to shorties vs long tubes. Shorties are WAY too short for almost any einge and only see improvements on an engine where the stock manifold is horribly restrictive. Short and long are in reference to each other, not in refernce to the type of header.


As for the dyno. dyno's measure work over a frame of time. without a spark signal to measure the engines time frame the dyno can only provide horsepower based on its time frame. In otherwords how fast the roller is being accelerated. Thats why a first gear pull with no spark reference would lead to 1700 hp. The rollers were accelerating fast, so thats the only thing the dyno had to operate from. If it has a spark signal it can figure out the gearing, mathematically get the reduce the hp and get the correct wheel tq. At least thats how I understand it.


BC

Roen

iTrader: (2)

That's how I had thought dynos to work too, and that to me implies that they measure wheel torque directly and derive power from it.

I had thought that if they measured power directly, regardless of the transmission gear torque multiplier, an engine can only make a certain amount of power, so I would conclude that dynos would measure the same no matter what gear you're in.

Now that I've had one reply for each suggestion, I'm doubly as confused.

anewconvert

iTrader: (1)

Think about it liek this. Hp is work done over time. If you are in a lower gear you do more work in less time. So without a reference as to the engines frame of time the dyno just has to go strictly on the work that it is seeing accomplished in its time frame. So if you arent in a 1:1 gearing set up you are going to get an inflated hp number unless you can remove the gearing from the equation manually.


BC

GtoRx7

iTrader: (5)

Well, even in 1:1 gear ratio, you still have a 4.10:1 rear end ratio, and then the tire diameter vs. roller diameter. Horsepower is work over time, and you said it best. I think the dyno can see a large acceleration, but only for a short period of time, giving it accurate HP numbers. (Large torque, short time HP = small torque, long time HP) The exception is in 1st gear like mentioned, but I think its caused from such a short sample rate, the computer cant capture the run accurately. Third gear, and fourth gear will dyno pretty close to one another from what I've seen, difference being frictional loses between gear loading. Sometimes the longer dyno run in 4th gear actually makes for more heat soaking, and less power. But I could be wrong, I'm tired

Roen

iTrader: (2)

Even if they are mathematical derivatives of one another, the dyno still has to measure one to get the other. Does it measure torque directly, or does it measure power?

GtoRx7

iTrader: (5)

That depends on the dyno. On a non-loading dyno, aka inertia dyno, it measures power. As it sees how fast it accelerates a set weight drum, for how long to determine horsepower. Then it can calculate torque once it knows the engine rpms, vs drum rpms.
Dynos like the Dyna-pack, and mustang dyno measure wheel torque production by placing a load against it. Then figures horsepower once the gear ratio, and engine rpms are put into the equation. This is why dyna-packs and mustangs are pretty badass.

Roen

iTrader: (2)

ah......cool, thanks for educating me on the two different types of dynos.