Pelican Parts
Parts Catalog Accessories Catalog How To Articles Tech Forums
Call Pelican Parts at 888-280-7799
Shopping Cart Cart | Project List | Order Status | Help



Go Back   Pelican Parts Technical BBS > 1- Porsche Technical Forums > Porsche 911 Technical Forum

Reply
 
LinkBack Thread Tools Rate Thread
Author
Thread Post New Thread    Reply
Moderator
 
Bill Verburg's Avatar
 
Join Date: Dec 2000
Posts: 22,268
Garage
Quote:
Originally Posted by 911st View Post
......

Is there any cooling advantages due to the timing of adjacent cylinders.
.....
in a US 90* V8 w/ 90* or cross-plane crank 2 cylinders on the same bank fire consecutively but they are not adjacent cylinders

Quote:
Originally Posted by 911st View Post
......
I guess it has to be a 90 deg to be an even fire....
there are several configurations that can be even fire
2 of them are
1) 90* V8 w/ a 180* crank(aka flat or plane crank)
2) 180* H6 w/ a 120* crank(aka stock 911)

a typical US or German V8 has a 90* V and a 90* crank. This combination makes them odd fire, which necessitates a more complicated exhaust. The simplest of the more complicated exhaust setups is a cross-pipe after the collectors. The cross pipe provides relief for the over pressure of 2 consecutively firing cylinders in each bank.

The cross pipe is also sometimes used for acoustic attenuation even on even fire engines.
__________________
Bill Verburg
'76 Carrera 3.6RS(nee C3/hotrod), '95 993RS/CS(clone)
| Pelican Home |Rennlist Wheels |Rennlist Brakes |
Old 01-14-2011, 08:21 AM
  Pelican Parts Technical Article Directory    Reply With Quote #81 (permalink)
Registered User
 
Join Date: Jan 2004
Location: Sacramento
Posts: 7,269
Thanks Will,
I got it, no potato's and any even fire motor.



Bill,

Good stufff.

I am wondering it there might also be a small cooling advantage when they get rid of the 2 consecutively firing cylinders in each bank with the 180 crank?

And or, might there also be a possible firing order change from a more typical lay out that might also be at work in this regard?

Fun stuff!
Old 01-14-2011, 09:44 AM
  Pelican Parts Technical Article Directory    Reply With Quote #82 (permalink)
Moderator
 
Bill Verburg's Avatar
 
Join Date: Dec 2000
Posts: 22,268
Garage
Quote:
Originally Posted by 911st View Post
T....

I am wondering it there might also be a small cooling advantage when they get rid of the 2 consecutively firing cylinders in each bank with the 180 crank?

And or, might there also be a possible firing order change from a more typical lay out that might also be at work in this regard?

Fun stuff!
If there is I've never seen it mentioned in the literature

the 8 cyl. engines seems to be where there are the most 3 of different crank and firing order options that work.

In the 908s the first 2 cranks tried were 90*, combined w/ a 180* V this makes for an even fire engine, again w/ a relatively simple exhaust, the last and final iteration was a 180*(flat or plane) crank and odd fire pattern( where 5 follows 8 and 1 follows 4). This last was chose as the secondary inertial forces for this configuration all cancel. The 90* crank also has to be heavier due to the necessary counter weights, a flat crank doesn't need the counter weights, it is thus lighter and revs more quickly. Note that the drivers hated the final config even though lap times were as good or better.

__________________
Bill Verburg
'76 Carrera 3.6RS(nee C3/hotrod), '95 993RS/CS(clone)
| Pelican Home |Rennlist Wheels |Rennlist Brakes |

Last edited by Bill Verburg; 01-14-2011 at 11:54 AM..
Old 01-14-2011, 11:22 AM
  Pelican Parts Technical Article Directory    Reply With Quote #83 (permalink)
Registered User
 
Join Date: Aug 2002
Location: Orchard Park, NY
Posts: 10,522
Great stuff, Bill....as usual.

I believe the firing order used at the 908 race intro ( was it Monza, '68?), had vibrations that caused problems,...someting like crank breakages or less-severe like alternator brackets breaking...right?. I thought the later firing order iterations resulted in *smoother* running?. Perhaps the answer is not smoother running.... but less of a certain kind of harmonic that was developed?
__________________
Wil Ferch
85 Carrera ( gone, but not forgotten )
Old 01-15-2011, 08:03 AM
  Pelican Parts Technical Article Directory    Reply With Quote #84 (permalink)
Moderator
 
Bill Verburg's Avatar
 
Join Date: Dec 2000
Posts: 22,268
Garage
Quote:
Originally Posted by Wil Ferch View Post
Great stuff, Bill....as usual.

I believe the firing order used at the 908 race intro ( was it Monza, '68?), had vibrations that caused problems,...someting like crank breakages or less-severe like alternator brackets breaking...right?. I thought the later firing order iterations resulted in *smoother* running?. Perhaps the answer is not smoother running.... but less of a certain kind of harmonic that was developed?
yes, the first appearance of the 908 was at LeMans practice in April '68, engine vibration above 7k rpm was an issue. 1st race appearance was April '68 at Moza, 3 cars were entered, best(only) finish was 19th. 1st win was at the ADAC-1000 km-Rennen auf der Nürburgring in May '68. vibration was still an issue hemce the experiments w/ firing order but keeping the crank and cams the same(middle above) and finally the crank change. the change to the 180* crank was made for Sebring '69 preliminary practice

this issue was on the engineers minds when the 917 was developed, the 917 is essentially 2 120* 901 cranks w/ a central power takeoff. Here are the fundemental and 1st order vibrations for the 917
__________________
Bill Verburg
'76 Carrera 3.6RS(nee C3/hotrod), '95 993RS/CS(clone)
| Pelican Home |Rennlist Wheels |Rennlist Brakes |
Old 01-15-2011, 09:07 AM
  Pelican Parts Technical Article Directory    Reply With Quote #85 (permalink)
Registered User
 
AlfonsoR's Avatar
 
Join Date: Apr 2010
Location: Houston, Tx
Posts: 951
^^^ So was the vibration issues completely addressed on the 908 by going to the 180* crank?
Old 01-15-2011, 10:51 AM
  Pelican Parts Technical Article Directory    Reply With Quote #86 (permalink)
 
Now Available for Ordering:   101 Projects For Your BMW 3 Series 1982-2000  [more info]
Registered User
 
Join Date: Aug 2002
Location: Orchard Park, NY
Posts: 10,522
Bill....thanks again.....but I unfortunately need to ask about this part of your statement on the 917 ( engine type 912)----> " the 917 is essentially 2 120* 901 cranks w/ a central power takeoff..."

??.....the 901 cranks ( same as 911, right?) were 120 degree cranks, right?,.... not flat cranks like 917? There was a main bearing journal between any two adjacent cylinders in 901/911.....whereas ( as shown in the 917 pic and your own text), the 917 was a flat crank with two con-rods alongside each other, to avoid a main bearing between *each* cylinder ( which, if done, would have made this very long engine maybe 1.5x as long !!).

901 different than 911?
__________________
Wil Ferch
85 Carrera ( gone, but not forgotten )
Old 01-15-2011, 11:34 AM
  Pelican Parts Technical Article Directory    Reply With Quote #87 (permalink)
Max Sluiter
 
Flieger's Avatar
 
Join Date: Mar 2006
Location: So Cal
Posts: 19,580
Garage
Will, you are right. It is more of a twin 911 crank- a long 911 crank with two rods on each throw.
__________________
911S
1971 chassis, 2.7RS spec MFI engine, suspension mods, lightened

Suspension by Rebel Racing, Serviced by TLG Auto, Brakes by PMB Performance
http://www.flickr.com/photos/max_911_fahrer/
Old 01-15-2011, 11:43 AM
  Pelican Parts Technical Article Directory    Reply With Quote #88 (permalink)
Moderator
 
Bill Verburg's Avatar
 
Join Date: Dec 2000
Posts: 22,268
Garage
Quote:
Originally Posted by AlfonsoR View Post
^^^ So was the vibration issues completely addressed on the 908 by going to the 180* crank?
yes, as far as reliability was concerned. that was the final configuration.
__________________
Bill Verburg
'76 Carrera 3.6RS(nee C3/hotrod), '95 993RS/CS(clone)
| Pelican Home |Rennlist Wheels |Rennlist Brakes |
Old 01-15-2011, 12:00 PM
  Pelican Parts Technical Article Directory    Reply With Quote #89 (permalink)
Moderator
 
Bill Verburg's Avatar
 
Join Date: Dec 2000
Posts: 22,268
Garage
Quote:
Originally Posted by Wil Ferch View Post
Bill....thanks again.....but I unfortunately need to ask about this part of your statement on the 917 ( engine type 912)----> " the 917 is essentially 2 120* 901 cranks w/ a central power takeoff..."

??.....the 901 cranks ( same as 911, right?) were 120 degree cranks, right?,.... not flat cranks like 917? There was a main bearing journal between any two adjacent cylinders in 901/911.....whereas ( as shown in the 917 pic and your own text), the 917 was a flat crank with two con-rods alongside each other, to avoid a main bearing between *each* cylinder ( which, if done, would have made this very long engine maybe 1.5x as long !!).

901 different than 911?
120* yes
901/911 are the same design. 908 was a take off of the then current 901 series of 6 cylinder in fact the type 908 engine initially used the same bore & stroke(84x66) as the current 901 but the bore was enlarged to 85mm for '67 LeMans(2926cc to 2996cc). The changes to the bottom end from the street 6 were 2 extra main bearings, 2 crank throw and a longer oil pump shaft. Of course the top end was totally different being taken from the DOHC 916
908 engine


In July '68 design work on the 912(917 engine) was started. It was was based on but still different from the 901/911. The 901/911/96/993/996/7 GT3 are all 8 bearing(7 main and 1 overhanging) 120* designs w/ a single rod per throw. 912(917 engine) used the same connecting rod length, valve & port sizes, bore& stroke(85x66) as the 3 liter 908, 912 displacement was 4494cc., Same valve timing too. 912 has 8 main like the 6 but big end diameter was reduced from57 to 52(compared to 908)
917
__________________
Bill Verburg
'76 Carrera 3.6RS(nee C3/hotrod), '95 993RS/CS(clone)
| Pelican Home |Rennlist Wheels |Rennlist Brakes |
Old 01-15-2011, 01:04 PM
  Pelican Parts Technical Article Directory    Reply With Quote #90 (permalink)
Moderator
 
Bill Verburg's Avatar
 
Join Date: Dec 2000
Posts: 22,268
Garage
Quote:
Originally Posted by Flieger View Post
Will, you are right. It is more of a twin 911 crank- a long 911 crank with two rods on each throw.
Nope, see post #90
__________________
Bill Verburg
'76 Carrera 3.6RS(nee C3/hotrod), '95 993RS/CS(clone)
| Pelican Home |Rennlist Wheels |Rennlist Brakes |
Old 01-15-2011, 01:05 PM
  Pelican Parts Technical Article Directory    Reply With Quote #91 (permalink)
Moderator
 
Bill Verburg's Avatar
 
Join Date: Dec 2000
Posts: 22,268
Garage
Here's a list of the specs for 904-917, from Barth, unfortunately it gets shrunk a bit too much

__________________
Bill Verburg
'76 Carrera 3.6RS(nee C3/hotrod), '95 993RS/CS(clone)
| Pelican Home |Rennlist Wheels |Rennlist Brakes |
Old 01-15-2011, 03:08 PM
  Pelican Parts Technical Article Directory    Reply With Quote #92 (permalink)
Registered User
 
Join Date: Feb 2010
Posts: 66
As stated earlier in the thread, the only reason for Ruf to do this was to stay in business. You can buy a new Porsche 911 in every configuration and flavor possible. Ruf had nothing to offer that was significantly different and charges outrageous prices.

I think it's pretty silly to stick even a compact V8 like that in the back of a 911, but it doesn't really matter what I think. It matters what people with more money than brains or taste think. That's the tuner market.

What would be an interesting application would be for Ruf to offer a V8 kit for Caymans. All those used Caymans out of warranty coming on the second hand market cheap. It would give them an exciting new life and power to put them in Ferrari 458 Italia land.
Old 01-15-2011, 03:49 PM
  Pelican Parts Technical Article Directory    Reply With Quote #93 (permalink)
Bland
 
RWebb's Avatar
 
Join Date: Jul 2007
Location: Greater Metropolitan Nimrod, Orygun
Posts: 41,941
Garage
P AG will not like Alois anymore if he did that...
Old 01-15-2011, 04:23 PM
  Pelican Parts Technical Article Directory    Reply With Quote #94 (permalink)
Registered User
 
Join Date: Jan 2004
Location: Sacramento
Posts: 7,269
Came across this sentence in reference to the hybrid "Porsche 918 Spyder concept ".

Quote:
It is motivated by various combinations of its 500-plus-hp, 3.4-liter V-8 (derived from the RS Spyder LMP2 car)
The 3.4 is a 90 deg 10k rpm motor. Wonder if it is a 180 deg crank?

Thus, Porsche seems to have some very high performance V8's in the pipe line.

If RUF has access there could be some possibility of it being sort of a parts shelf build.

Don't get me wrong, RUF knows there stuff and is probably very capable of doing this on there own.
Old 01-16-2011, 02:49 PM
  Pelican Parts Technical Article Directory    Reply With Quote #95 (permalink)
Moderator
 
Bill Verburg's Avatar
 
Join Date: Dec 2000
Posts: 22,268
Garage
Quote:
Originally Posted by 911st View Post
Came across this sentence in reference to the hybrid "Porsche 918 Spyder concept ".



The 3.4 is a 90 deg 10k rpm motor. Wonder if it is a 180 deg crank?

Thus, Porsche seems to have some very high performance V8's in the pipe line.

If RUF has access there could be some possibility of it being sort of a parts shelf build.

Don't get me wrong, RUF knows there stuff and is probably very capable of doing this on there own.
I've never seen the specs on the 3.4L 90* V8 RS Spyder's crank, but...
Most pure race 90*v8s do use flat cranks, Porsche used a flat crank on their 90* Indy V8. Look at the exhaust it tells you whether or not it is even fire or odd fire.

here is the exhaust as raced
__________________
Bill Verburg
'76 Carrera 3.6RS(nee C3/hotrod), '95 993RS/CS(clone)
| Pelican Home |Rennlist Wheels |Rennlist Brakes |
Old 01-16-2011, 03:43 PM
  Pelican Parts Technical Article Directory    Reply With Quote #96 (permalink)
Registered User
 
Join Date: Aug 2002
Location: Orchard Park, NY
Posts: 10,522
Bill:
Maybe we need to start another thread.....my core point was that the 911 is not a flat crank, its a 120 degree crank, and uses a main bearing between any 2 adjacent cylinders.

In contrast, the 917 crank is ( in reality) a "180 degree V-12".....not a "flat-12-boxer" like the 911 is considered a "flat-6-boxer". The 917 has two adjacent con-rods...two cylinders alongside one another....without a main bearing in-between. No "boxing". So it *is* different and wouldn't be like 2 911's stuck together.....right?....unless I'm severely misunderstanding you.
__________________
Wil Ferch
85 Carrera ( gone, but not forgotten )

Last edited by Wil Ferch; 01-17-2011 at 08:29 AM..
Old 01-16-2011, 05:11 PM
  Pelican Parts Technical Article Directory    Reply With Quote #97 (permalink)
Registered User
 
Join Date: Jan 2004
Location: Sacramento
Posts: 7,269
Good point on the exhaust. Looks like a flat crank then.

I guess if each side goes from un equal events to equal events it might have a small help in cooling.

I do not recall the spacing on a domestic V8 but if it is something like 180,120,180,180 deg and goes to a 180, 180, 180, 180 deg it would allow more even time to transfer heat between events.
Old 01-16-2011, 05:28 PM
  Pelican Parts Technical Article Directory    Reply With Quote #98 (permalink)
Moderator
 
Bill Verburg's Avatar
 
Join Date: Dec 2000
Posts: 22,268
Garage
Quote:
Originally Posted by Wil Ferch View Post
Bill:
Maybe we need to start another thread.....may core point was that the 911 is not a flat crank, its a 120 degree crank, and uses a main bearing between any 2 adjacent cylinders.

In contrast, the 917 crank is ( in reality) a "180 degree V-12".....not a "flat-12-boxer" like the 911 is considered a "flat-6-boxer". The 917 has two adjacent con-rods...two cylinders alongside one another....without a main bearing in-between. No "boxing". So it *is* different and wouldn't be like 2 911's stuck together.....right?....unless I'm severely misunderstanding you.
Will, I'm not arguing w/ you
I said 'essentially' not exactly, also from post#90
Quote:
120* yes
901/911 are the same design. 908 was a take off of the then current 901 series of 6 cylinder in fact the type 908 engine initially used the same bore & stroke(84x66) as the current 901 but the bore was enlarged to 85mm for '67 LeMans(2926cc to 2996cc). The changes to the bottom end from the street 6 were 2 extra main bearings, 2 crank throw and a longer oil pump shaft. Of course the top end was totally different being taken from the DOHC 916
908 engine

and
Quote:
In July '68 design work on the 912(917 engine) was started. It was was based on but still different from the 901/911. The 901/911/96/993/996/7 GT3 are all 8 bearing(7 main and 1 overhanging) 120* designs w/ a single rod per throw. 912(917 engine) used the same connecting rod length, valve & port sizes, bore& stroke(85x66) as the 3 liter 908, 912 displacement was 4494cc., Same valve timing too. 912 has 8 main like the 6 but big end diameter was reduced from 57 to 52(compared to 908)
yes, when 2 rods share a journal in a flat confiuration it is properly called a 180*V not a boxer, but I never did call it a boxer did I. A boxer design is a flat engine w/ a single rod per journal and yes a 911 is considered a boxer. But it is a modified one. A true boxer will be flat, have a single rod per journal and a 180* crank, like a VW or Subaru.
__________________
Bill Verburg
'76 Carrera 3.6RS(nee C3/hotrod), '95 993RS/CS(clone)
| Pelican Home |Rennlist Wheels |Rennlist Brakes |
Old 01-16-2011, 05:35 PM
  Pelican Parts Technical Article Directory    Reply With Quote #99 (permalink)
Registered User
 
Join Date: Aug 2002
Location: Orchard Park, NY
Posts: 10,522
Just lookin' for clarity Bill....which I think you cleared up here. No arguments either...
__________________
Wil Ferch
85 Carrera ( gone, but not forgotten )
Old 01-17-2011, 08:30 AM
  Pelican Parts Technical Article Directory    Reply With Quote #100 (permalink)
Reply

Thread Tools
Rate This Thread
Rate This Thread:

 


All times are GMT -8. The time now is 01:28 AM.


 
Powered by vBulletin® Version 3.8.7
Copyright ©2000 - 2018, vBulletin Solutions, Inc.
Search Engine Optimization by vBSEO 3.6.0
Copyright 2017 Pelican Parts LLC - Posts may be archived for display on the Pelican Parts Website -    DMCA Registered Agent Contact Page
 

DTO Garage Plus vBulletin Plugins by Drive Thru Online, Inc.