|
|
|
|
Joined: Sep 2000
Posts: 9,602
Hard-core CEG'er
|
Hard-core CEG'er
Joined: Sep 2000
Posts: 9,602 |
Originally posted by Travis:
1. As said before primary and secondary valve opening/durations mean NOTHING. They are there for emissions only and a possible 100 rpm longer power band in either direction.
2. Seat duration doesnt mean ANYTHING in the production of power either. Its the amount of meat under the seat that counts. A better number would be the 0.050 durations.
1. They uses separate lobe designs because the airflow to each valve is "completely" separate and therefore has different velocity, density, and cylinder filling ability.
They produce a tremendous change in the power curve when used together. It makes 2 complete different power curves and the IMRC point is put at were they cross to make the best power under the curve.
This was done to retain low speed drivability (TQ - Mainly for ATX's IMO) and still make & sustain good high rpm HP & TQ.
Definitely NOT done for emissions!
Why do you hold to this incorrect and very basic understanding of the cam & intake design?
2. I agree that Duration by itself is meaningless.
It is the valve timing points that play a large role in power production and when & where it will be produced. "Meat under the seat" as you put it is not the tell all either.
2000 SVT #674
13.47 @ 102 - All Motor!
It was not broke; Yet I fixed it anyway.
|
|
|
|
|
Joined: Sep 2000
Posts: 9,602
Hard-core CEG'er
|
|
Hard-core CEG'er
Joined: Sep 2000
Posts: 9,602 |
Originally posted by gearhead98:
how does that cam add hp, the duration on the intake, which doesn't list the primary and secondary valves duration. Plus the duration listed is the same as the seecondary duration on the SVT, and the exhaust duration is lower, the SVT exhaust duration is 262. so how does this increase hp,
These are stock cams reground with a slightly longer duration.
No they are not even to the level of SVT cams. Yes the intake has the same "duration" but the valve timing points are very substandard. Why I do not know, maybe they were limited to the amount of material they had to work with.
The max lift of the regrind is reduced by 8-9% as well! So I just do not see these beating the stock cams by much even with the changed valve timing and "slightly" longer duration.
Yes the price may be lower but IMO you would not even get what you pay for in this deal. If you are interested in custom cams and the SVT set is too tame for you then look at the CAT Cams. (I.E Stage 3 intake & Stage 2 exhaust)
However once you price out the cost to build up of a reliable NA engine you may just save a chunk of that money and go with a turbo setup. 
2000 SVT #674
13.47 @ 102 - All Motor!
It was not broke; Yet I fixed it anyway.
|
|
|
|
|
Joined: Dec 2001
Posts: 3,570
Hard-core CEG\'er
|
|
Hard-core CEG\'er
Joined: Dec 2001
Posts: 3,570 |
Forgive a noob question, but would using the SVT cams in a non-SVT duratect require a custom computer program? Or do the cams operate completely independant of the computer?
|
|
|
|
|
Joined: Jun 2003
Posts: 1,145
Hard-core CEG\'er
|
|
Hard-core CEG\'er
Joined: Jun 2003
Posts: 1,145 |
thanx demon i knew i wont crazy when i thought these cams would no make any hp if at all keep what we have, i just had the wrong reason for this thinking
98.5 Black SE ATX
S&B filter, SVT MAF, optimized SVT TB, mesh grille, removed orange reflectors, painted rear reflector, gutted pre-cats, optimized SVT LIM, 19lb injectors, resonator removed
cant afford an svt but lookin for 1 in nc
|
|
|
|
|
Joined: Oct 2003
Posts: 283
CEG\'er
|
|
CEG\'er
Joined: Oct 2003
Posts: 283 |
Reaaallllyy.... Actaully you have 3 tuning states. But the diffrence between 8 degrees of seat duration especially on an oem application where ramp rates are slow for longevity It has the possibility of being worth 1 or 2 horsepower 2-3 ft lbs of torque difference. Cam timing plays very VERY little roll in intake manifold tuning. Thats all im going to say on the subject.
Ex-cat cams dealer. Today we do motor mounts.. Tommorow. Intake manifolds 
|
|
|
|
|
Joined: Sep 2000
Posts: 9,602
Hard-core CEG'er
|
|
Hard-core CEG'er
Joined: Sep 2000
Posts: 9,602 |
Originally posted by Travis:
Cam timing plays very VERY little roll in intake manifold tuning. Thats all im going to say on the subject.
Please explain that statement because it goes against most standard design theory and thinking.
Cam & intake design usually go hand in hand.
If it does not then - Why not get a long duration cam with early opening points and run it on an intake designed to make a low rpm power curve via it's port volume and overall runner length & design.
Using your thinking there would be nothing wrong with a setup like that and it is plainly obvious you would be overcamming your intake's ability and thus building an engine that makes a terrible power curve.
The split port cam has 2 separate patterns because each respective port has different airflow characteristics. How can you not see that reasoning?
If we were talking about oval port heads and intakes then it would be a different story but we are not.
I think that the best design for NA power would be oval port heads with custom single pattern cams and a custom intake.
2000 SVT #674
13.47 @ 102 - All Motor!
It was not broke; Yet I fixed it anyway.
|
|
|
|
|
Joined: Oct 2003
Posts: 283
CEG\'er
|
|
CEG\'er
Joined: Oct 2003
Posts: 283 |
Well this is my whole quim in a nutshell with this system. Whenever you tune an intake manifold you tune the cylinder as whole. Whenever you "tune" an intake manifold you tune the runners by volumn length and crossection. Basically volumn because the other 2 equal V.
Whenever the valve opens Thats when the air starts moving in the ports. Whenever it starts to move this starts the pressure waves that help tune the engine to supercharge it. Whenever you have 2 intake runner lengths like that you only get half the ramcharging effect. But thats not the only disadvantage. Because the volumns are diffrent for each runner the pulse is also weakened this way as well. Because whenever you tune for low rpm you want a long small cross section runner. Whenever you go for high rpm you want a thick short crossection runner. If you try to go half and half the pressures waves arnt nearly as strong for either. It gives an incredibly flat curve. BUT its an all out effort for drivability. You sacrifice alot at the top and in the midrange for your thickness at 2000 rpms.
THats just the intake manifold part. THe cam timing part is a mystery to me. Because the entire time you have a cylinder open you want the maximium amount of air flowing into it. Everyone goes after rocker arm crushing ramp rates that take 400 lb springs for a reason. If the valves are going to be open in a cylinder they want them open damnit. By having a cylinder open past bdc you are loosing power across the board if your intake manifold isnt ram charging the cylinder. Its simply going to push the air back out. It doesnt help the tuning of the intake manifold to any degree. A slightly larger lobe requires a slightly longer runner and vice versa for a smaller lobe to tune to the same rpm.
The diffrence inflow between 8 degrees of seat duration just isnt anything though. 8 Degrees of seat duration is probably only 2 or 3 degrees of .050 duration. Just not enough diffrence eto make a large impact.
On the zetec engines our first cam upgrade to street/strip is usaully about 40 degrees of seat duration and 28 degrees of .050 duration. And the ramp rates of the cams are MUCH more aggresive so that change is even more radical then 40 degrees of oem seat increase.
Every penny counts but on a larger scale the diffrence of 1 valve opening at a diffrent point is just not much to get excited about. Im pretty convinced that it causes a swirl effect in the cylinder like others have stated for a slightly better burn and a better sniffer test.
Last edited by Travis; 04/21/04 12:20 AM.
Ex-cat cams dealer. Today we do motor mounts.. Tommorow. Intake manifolds
|
|
|
|
|
Joined: Feb 2003
Posts: 52
CEG\'er
|
|
OP
CEG\'er
Joined: Feb 2003
Posts: 52 |
I did ask Piper Cams few questions and they replyed:
The rocker ratio of the engine is in fact 1.8 and the 1 : 1 listed in the
catalogue is a miss print. The cams we provide is on your own std units
which we reprofile to the fast road specification.
Ford Mondeo GT mk1 sedan 1996 2.5L Duratec
|
|
|
|
|
Joined: Jan 2003
Posts: 45
New CEG\'er
|
|
New CEG\'er
Joined: Jan 2003
Posts: 45 |
So Demon I have a question those cams wont make a huge difference (if any) on an SVT but out about for those of us (with regular duratec) who alway wanted to upgrade to SVT cams? would it be worth it? or should I just try to buy an SVT motor?
99 contour se sport
mods: scautosports intake, custom exaust(2.5" pipe slipt into 2.25 into two mufflers)
H&R springs
B&M short shihter
bsa rims 17"
too much audio to list
|
|
|
|
|
|
|
