|
|
Joined: Sep 2000
Posts: 4,693
Hard-core CEG'er
|
Hard-core CEG'er
Joined: Sep 2000
Posts: 4,693 |
Originally posted by bnoon:
Originally posted by AirKnight:
Originally posted by Big Jim:
If you port and polish the SE heads you should be able to pretty much replicate the extrude honed SVT heads.
No, you can't replicate the extrude hone process with port and polish. Hand porting the intake passages with curves is not going to be as good as extrude honing it.
Not true. The main reason for extrude honing is the ease and speed at which the gains can be replicated from piece to piece. The next reason EH would be used over hand P&P is being able to reach intricate details inside impossible to reach ports, such as the UIM on a 2.5 Duratec. Outside of that, one has no gain over the other. The air doesn't care how the material was removed as long as the right material was taken from the correct spots. That's where an experienced P&P'er comes into play with flow numbers to back up their data. BTW, hand P&P numbers can surpass EH numbers and vice-versa depending on how much work has been done.
I believe that someone with talent and experience could do a better job porting heads than could be done with extrude honing. Certain intake manifolds are another matter.
Jim Johnson
98 SVT
03 Escape Limited
|
|
|
|
|
Joined: Jun 2001
Posts: 1,541
Hard-core CEG'er
|
|
Hard-core CEG'er
Joined: Jun 2001
Posts: 1,541 |
Actually, one of the benefits to Extrude Hone is the surface finish when compared to port/polish with a rotary tool.
With EH, you get a uniform finish that IS NOT mirror smooth (when viewed microscopically).
With rotary tools, you get a very smooth finish. And, if done poorly, you get "ridges" (for lack of a better word) where tool passes overlap.
The inherent "roughness" of the EH finish is better for fluid flow when compared to a smooth finish. Something about laminar shear and the fluid (air) along the smooth surfaces moving slowly, and the EH finish "disturbing" the fluid along its surfaces and not allowing it to slow down at the edges. (Sorry, I never took fluid dynamics, so I can't give a better explaination. But I have read this in the past, and it made complete sense at the time.)
All in all, it is my understanding that when comparing two ports that have the same cross-sectional surface area for flow, the EH will flow better than a rotary tool finished surface.
|
|
|
|
|
Joined: Jun 2000
Posts: 2,621
Redneck Troll
|
|
Redneck Troll
Joined: Jun 2000
Posts: 2,621 |
Originally posted by PA 3L SVT:
Actually, one of the benefits to Extrude Hone is the surface finish when compared to port/polish with a rotary tool.
With EH, you get a uniform finish that IS NOT mirror smooth (when viewed microscopically).
With rotary tools, you get a very smooth finish. And, if done poorly, you get "ridges" (for lack of a better word) where tool passes overlap.
The inherent "roughness" of the EH finish is better for fluid flow when compared to a smooth finish. Something about laminar shear and the fluid (air) along the smooth surfaces moving slowly, and the EH finish "disturbing" the fluid along its surfaces and not allowing it to slow down at the edges. (Sorry, I never took fluid dynamics, so I can't give a better explaination. But I have read this in the past, and it made complete sense at the time.)
All in all, it is my understanding that when comparing two ports that have the same cross-sectional surface area for flow, the EH will flow better than a rotary tool finished surface.
That would be one of the minor benefits of the EH, but hardly a benefit in any street driven engine. If you're trying to get that last few HP on restricted engines in competition, like say, NASCAR, then every last air particle counts and it makes sense to EH. The benefits on a street engine are nil unless the porting can't be done properly by hand.
http://www.bnmotorsports.com
"And I will strike down upon thee with great vengeance and furious anger those who attempt to poison and destroy my CEG brothers. And you will know I am the Moderator when I lay my vengeance upon you."
|
|
|
|
|
Joined: Sep 2000
Posts: 4,693
Hard-core CEG'er
|
|
Hard-core CEG'er
Joined: Sep 2000
Posts: 4,693 |
Don't get me wrong, I think extrude honing is a great process, but a talented porting technician can do a better job in every respect including final finish. One of the huge advantages of porting is that you can better alter and control shape. You just don't have much control over that with gritty putty getting forced through a port. Any claims about a better finish with extrude honing is just in someones mind. In areas that you don't have good access to, like the twists and turns in many manifolds, it can be a completely different matter. At least that is my opinion.
Jim Johnson
98 SVT
03 Escape Limited
|
|
|
|
|
Joined: Mar 2003
Posts: 22
New CEG\'er
|
|
New CEG\'er
Joined: Mar 2003
Posts: 22 |
I think Extrude Hone has the advantage of less port to port, runner to runner flow variablity..by nature it will port the tighter area more and more open areas less. But the cost of removing lots of material with E. Hone and the inability to alter shape are in favoer of hand porting. Therefore, I suspect the BEST solution would be hand porting to basic shape & size FOLLOWED by 1-2 Extrude Hone passes to equalize flow, fine "flow tune" the shape and put a nice finish on things..SCC and other tuner mag writeups have talked about this favorably.
1999 Amazon Green SVT
A few mods...179.2 FWHP so far
|
|
|
|
|
