Pictures Of A Half-bp Build (large, Long)
06-30-2004 | 11:56 AM
#31
Senior Member
Joined: Dec 2003
Posts: 500
From: Minneapolis,MN
You can also look at this way. The smoother something is, the more surface area there is, which causes more friction. To decrease friction, you need less surface area, so you need something rough, like teflon. Microscopic views of teflon show that it is not smooth, but very rough, but it has less surface area, so it has less friction. Thats why it works so well.
Dont take this persaonally and get all pissed. You are absolutely and totally wrong there. It is all wrong. On top of you being wrong...what you kids dont understand is there is oil involved. Oil does a better job in an environment for which it was designed. These large bearings dont like thin oil.
I said this before and I will say it agian. Go talk to some engine builders on this one. Not a "Rotary" builder but somone who has experience building both and has some schooling involved with their background.
06-30-2004 | 10:16 PM
#32
Junior Member
Joined: Jun 2004
Posts: 2
I gotta back GMON on this one.
A surface covered in oil will definitely have less friction then one not.
Consider; Honda (I know in the Insight) roughes up (shotpeaned?) their piston skirts spacifically for the purpose of retaining oil to reduce the friction. Then again, it uses 0W-20 oil, but still, you get the idea
I understand the difference in the side-skirt senario is that it is more about oil retention for a part that gets oil sprayed at it (unlike the rotor bearings, where oils flows through it). However, it still comes down to the bottom line of that you are sacrificing a lot of reliability for a difference that is all but completely unnoticable in most applications (by my understanding, keep in mind, I'm no expert)
Just my thoughts!
A surface covered in oil will definitely have less friction then one not.
Consider; Honda (I know in the Insight) roughes up (shotpeaned?) their piston skirts spacifically for the purpose of retaining oil to reduce the friction. Then again, it uses 0W-20 oil, but still, you get the idea
I understand the difference in the side-skirt senario is that it is more about oil retention for a part that gets oil sprayed at it (unlike the rotor bearings, where oils flows through it). However, it still comes down to the bottom line of that you are sacrificing a lot of reliability for a difference that is all but completely unnoticable in most applications (by my understanding, keep in mind, I'm no expert)
Just my thoughts!
06-30-2004 | 10:25 PM
#33
Senior Member
Joined: Nov 2002
Posts: 925
From: Honolulu, Hawaii USA
Originally Posted by BDC' date='Jun 27 2004, 02:56 PM
I gave you both pictures of "backcutting" done on larger bridgeports as well as a practical explanation as to why it can only be done so much on the smaller cuts but you seem to have refused to acknowledge that. Refer to the older thread and you'll see my response to your assertion that "others would find my bridgeports to be laughable". You say my work would be considered "laughable", yet I haven't one time ever heard of a bridgeported car that you've done straight through. Can you honestly and actually tell me, with real-world, practical experience, how much of a difference backcutting would make on bridgeport cuts that are small like the ones I do? Did you even know that I do do a form of backcutting to help with the fact that the cut is made 90 degrees perpendicular to the port tunnel?
I don't need to prove anything in my experience.
The dyno sheet has the proof, if you know how to read it.
My customers do not require bridgeports for their needs.
So far, I have not had any customer who "needed" a BP.
I do have a potential customer that wants one, but I'm not holding my breath on it.
I do cringe when I read about these people who wants BP's "just for the sound".
How do you justify these "street" BP's?
But then again, the customer is always right, right?
-Ted
07-01-2004 | 07:29 AM
#34
Senior Member
Joined: Dec 2002
Posts: 947
From: Bayou-self Louisiana
Originally Posted by roadkill669' date='Jun 30 2004, 08:51 AM
You can also look at this way. The smoother something is, the more surface area there is, which causes more friction. To decrease friction, you need less surface area, so you need something rough, like teflon. Microscopic views of teflon show that it is not smooth, but very rough, but it has less surface area, so it has less friction. Thats why it works so well.
And also, man I wish my bridge turns out like that. I am starting it this Friday, so I hope I do a good job.
And also, man I wish my bridge turns out like that. I am starting it this Friday, so I hope I do a good job.
That why some intakes are dimpled to help flow and also fuel mixture.
On boats that drag they rough the pad to help break surface adhesion.(less surface contact)
Drag tires are slick more friction ...dont have the aquatread for better grip.
07-01-2004 | 09:39 AM
#35
Senior Member
Joined: Feb 2003
Posts: 564
From: Calgary
I don't think I need to stick up for BDC here but...
I do back cut my bridgeports, but as BDC says, there is also a limit to how much can be done,If you are basing your comments the racing beat catalog, or the using the H2MYRx-7 hand book as gospel when it comes to porting, most of that info is based on earlier engines, and is 20 years old, you should realize you can't go backcutting the **** out of the ports on the later engines due to the o ring groove being moved to the irons, in the earlier irons you had nearly an 1/8" of an inch more meat in the iron to back cut, you could put a pretty mean angle on the port projectory and still not worry about breaking through, on top of that the the 0-ring side wall pressure was on the aluminium housing, only really exerting pressure on the iron in one direction, where with the oring groove in the iron now, the thin cast wall has to retain the ring, another thing to keep in mind is using the FD corner springs, with more spring tension, puts more force on the bridge itself, I keep it thicker than I would with the old style spring.
Is there any benefit to this "lite" bridgeing?... Seeing as in the post about Bnr hybrids, people were pretty much hysterical when they saw full boost on the bnr hybrid at 4000 rpm, I laughed at this, with a partial bridge and p-trim 1.15 a/r turbine I saw full boost in 2nd gear at 3000 rpm rpm, I could never hit more than 6 psi of boost in 1st gear,but with the partial bridge, I could build 12 psi in 1 st gear. Boiling it down, the partial bridge if anything, made my car more streetable, it dropped my boost threshold by nearly 1300 rpm, I would say it sees positive manifold pressure sooner than a stock s4 with more than double the stock power output. The slightest throttle input with a partial bridge builds positive manifold pressure, on a turbo car you basically have boost all the time, its the closest my 13b has ever felt to my 440 v-8. My next engine will be a full bridge, there is no comparison between a street port and a bridgeported engine...maxt
I do back cut my bridgeports, but as BDC says, there is also a limit to how much can be done,If you are basing your comments the racing beat catalog, or the using the H2MYRx-7 hand book as gospel when it comes to porting, most of that info is based on earlier engines, and is 20 years old, you should realize you can't go backcutting the **** out of the ports on the later engines due to the o ring groove being moved to the irons, in the earlier irons you had nearly an 1/8" of an inch more meat in the iron to back cut, you could put a pretty mean angle on the port projectory and still not worry about breaking through, on top of that the the 0-ring side wall pressure was on the aluminium housing, only really exerting pressure on the iron in one direction, where with the oring groove in the iron now, the thin cast wall has to retain the ring, another thing to keep in mind is using the FD corner springs, with more spring tension, puts more force on the bridge itself, I keep it thicker than I would with the old style spring.
Is there any benefit to this "lite" bridgeing?... Seeing as in the post about Bnr hybrids, people were pretty much hysterical when they saw full boost on the bnr hybrid at 4000 rpm, I laughed at this, with a partial bridge and p-trim 1.15 a/r turbine I saw full boost in 2nd gear at 3000 rpm rpm, I could never hit more than 6 psi of boost in 1st gear,but with the partial bridge, I could build 12 psi in 1 st gear. Boiling it down, the partial bridge if anything, made my car more streetable, it dropped my boost threshold by nearly 1300 rpm, I would say it sees positive manifold pressure sooner than a stock s4 with more than double the stock power output. The slightest throttle input with a partial bridge builds positive manifold pressure, on a turbo car you basically have boost all the time, its the closest my 13b has ever felt to my 440 v-8. My next engine will be a full bridge, there is no comparison between a street port and a bridgeported engine...maxt
