Flat plane a 928 engine?
08-20-2006, 06:37 PM
#16
Inventor
Rennlist Member
Rennlist Member
I don't think you'd even need the 4-cyl heads, just swap the cams into the 16V towers or onto the 32V heads.
What to do with the left side? The cam gear will be on the wrong end, right? Or the offset and firing order will be wrong?
What to do with the left side? The cam gear will be on the wrong end, right? Or the offset and firing order will be wrong?
08-20-2006, 06:54 PM
#17
Nordschleife Master
Join Date: Sep 2004
Location: Not close enough to VIR.
Posts: 9,429
Likes: 0
Received 2 Likes
on
2 Posts
On the left side you'd just swap the cams to the correct side. Firing order could be a problem for balance, but in a 90* V8 the timing between firings would be fine without any mods. 1-4 would fire at 0-180-360-540 and 5-8 would fire at 90-270-450-630
08-20-2006, 06:59 PM
#18
Rennlist Member
ALL Ferrari V8s are flat plane, excepting only one odd development for Lancia. Dont seem to have a rep for rough running AFAIK. Audi made flat plane racing cranks for the German touring car series by flattening a 2 plane unit, and Chebby cast some of theirs flat and twist them to 2 plane. Might be a toss up whether to start from scratch or flatten an existing and machine it down.
jp 83 Euro S AT 50k
jp 83 Euro S AT 50k
08-20-2006, 07:19 PM
#19
Gluteus Maximus
Rennlist Member
Rennlist Member
Thread Starter
Join Date: Nov 2004
Posts: 6,365
Likes: 0
Received 0 Likes
on
0 Posts
I think Audi claimed they twisted theirs to get a flat-plane engine past the rules, but they probably really made it from scratch.
I don't think anyone would twist a cast crank, it's easy enough to cast it in a cross to begin with. But most forged cranks are initially forged flat and then twisted into a cross. However this introduces some extra stress. Now you can buy "non-twist" cranks that are forged directly into the cross, but they're quite a bit more expensive than a normal forging as the machinery to do that is complex and expensive.
In 1992, Audi left the German DTM racing series after a controversy around the crankshaft design of their V8-powered race cars. After using the road car's cross-plane 90°-crankshaft for several years, they switched to a flat-plane 180° version which they claimed was made by "twisting" a stock part. The scrutineers decided that this would stretch the rules too far.
08-21-2006, 01:59 AM
#20
Burning Brakes
I'll be watching this very closely... I've really wanted to put NA 944 heads on a 4.5l block and see how the cams changed how it ran.
Don't you have to weld up some coolant passages on the 944 heads for them to work right? Are the valves any bigger than the 928 heads have?
4.5 blocks are a dime a dozen, this could be really cool...
Don't you have to weld up some coolant passages on the 944 heads for them to work right? Are the valves any bigger than the 928 heads have?
4.5 blocks are a dime a dozen, this could be really cool...
08-21-2006, 02:26 AM
#21
Banned
Join Date: Feb 2002
Location: Ft. Lauderdale FLORIDA
Posts: 5,248
Likes: 0
Received 4 Likes
on
3 Posts
My understanding on this is that:
1. An even-firing V8 like the one in the 928 [Ferrari V8 engines do not fire with even intervals; the time between firings varies due to the flat plane crank] has quite a bit less vibration, and
2. An even-firing V8 has better intake characteristics at the lower engine speeds that the M28 normally exists at. At higher RPM's the flat plane breathes better; that is why the stock-block based Infinity V8's at Indy run a flat plane crank while the cars are normal even-firing. Then again...what RPM's do those Indy V8's run at-?
3. An even firing V8 has a "staccato" rumble caused by the exhaust pulses alternately doubling themselves/cancelling themselves out. A flat plane can't do this, and it winds up sounding like a Japanese motorcycle. A higher pitch sound, and more of a scream than a rumble.
-This last is the only reason that I can see for trying to flat-plane an M28 engine. It would certainly be fascinating to hear! But I'll bet you'll spend upwards of $5000 to produce those nice noises...while not enjoying any performance advantage at all. It seems to me that a good exhaust costs a hell of a lot less!
Good idea!
Keep up the good work...
N!
1. An even-firing V8 like the one in the 928 [Ferrari V8 engines do not fire with even intervals; the time between firings varies due to the flat plane crank] has quite a bit less vibration, and
2. An even-firing V8 has better intake characteristics at the lower engine speeds that the M28 normally exists at. At higher RPM's the flat plane breathes better; that is why the stock-block based Infinity V8's at Indy run a flat plane crank while the cars are normal even-firing. Then again...what RPM's do those Indy V8's run at-?
3. An even firing V8 has a "staccato" rumble caused by the exhaust pulses alternately doubling themselves/cancelling themselves out. A flat plane can't do this, and it winds up sounding like a Japanese motorcycle. A higher pitch sound, and more of a scream than a rumble.
-This last is the only reason that I can see for trying to flat-plane an M28 engine. It would certainly be fascinating to hear! But I'll bet you'll spend upwards of $5000 to produce those nice noises...while not enjoying any performance advantage at all. It seems to me that a good exhaust costs a hell of a lot less!
Good idea!
Keep up the good work...N!
08-21-2006, 05:47 AM
#22
Nordschleife Master
Yeah good idea, but there are no real benefits to this.
Sure its cool to say flat plane crank but 90% of "gear heads" wont even know what the hell that is. I first learned of these in 2001 When BMW was using these in their 4.0L V8 M3's. They are vibration prone by design, they go away with revs, but racing cars are in the 9,000-12,000 rpm range, not to mention 20,000 for formula 1, but 928's are heavy cars. Torque i would rate higher than HP in these machines. You are intending this for a street ca correct?
If you would want to study these study the DTM series i bet Mercedes, uses this in their touring cars. You would need to do serious R&D to get it to work i would expect to replace everything, your oiling system would need attention i would replace all moving parts in the lower end, not to mention the cams for which no one has prototyped for a 928, i am sure that is simple though you just take your lobe profile and adjust it in deg on the cam so that it works with the new firing order. You would spend years making the whole system work though, with what to gain, honetly maybe you get more hp and more RPM but that would be due to the fact that you put in modern, new components that are lighter and open up heads which would be the most likely answer for the increase in performance. Sure "flat plane" is an exotic word to many people, but there is no benefit to converting this engine which was designed from the outset to have a cross plane crank to one with a flat plane. You mentioned the sound, it does sound different but you can get the same sound by running a different header deisgn that would collect from primaries off both banks and match them up in whatever firing order you want. That would take up allot of space. But what else are you trying to acheive with this idea?
Dont get me wrong, its a neat idea, its exotic but there is no real benefit to this design. The engines that use this design, these engines are designed fromt he outset with this type crank, and i dont have any experience with them, but i am sure there are issues specific to this type design that anyone could miss.
If your so dead set on this just buy yourself a ferrari V8 and stuff it in there you can find one for about $20,000, they have al the flat plane noise you want, or hell just spend $30,000 and put in a v12 from a 550 and you then have added cylinders and a flat plane crank and it will be allot more sound then something put together by a DIYer with parts from the local machine shop and the JE piston catalog.
I think there are other things to put your attention to on these engines that will give you far greater bang for your buck, what with displacement, cams, valves intake system, exhaust, hell the crank is probably the last thing in the world that the 928 could use improved upon honestly, most people would replace rods pistons valves intake all that crap before messing around with crank design, but if you have money to burn, by all means go for it.
Sure its cool to say flat plane crank but 90% of "gear heads" wont even know what the hell that is. I first learned of these in 2001 When BMW was using these in their 4.0L V8 M3's. They are vibration prone by design, they go away with revs, but racing cars are in the 9,000-12,000 rpm range, not to mention 20,000 for formula 1, but 928's are heavy cars. Torque i would rate higher than HP in these machines. You are intending this for a street ca correct?
If you would want to study these study the DTM series i bet Mercedes, uses this in their touring cars. You would need to do serious R&D to get it to work i would expect to replace everything, your oiling system would need attention i would replace all moving parts in the lower end, not to mention the cams for which no one has prototyped for a 928, i am sure that is simple though you just take your lobe profile and adjust it in deg on the cam so that it works with the new firing order. You would spend years making the whole system work though, with what to gain, honetly maybe you get more hp and more RPM but that would be due to the fact that you put in modern, new components that are lighter and open up heads which would be the most likely answer for the increase in performance. Sure "flat plane" is an exotic word to many people, but there is no benefit to converting this engine which was designed from the outset to have a cross plane crank to one with a flat plane. You mentioned the sound, it does sound different but you can get the same sound by running a different header deisgn that would collect from primaries off both banks and match them up in whatever firing order you want. That would take up allot of space. But what else are you trying to acheive with this idea?
Dont get me wrong, its a neat idea, its exotic but there is no real benefit to this design. The engines that use this design, these engines are designed fromt he outset with this type crank, and i dont have any experience with them, but i am sure there are issues specific to this type design that anyone could miss.
If your so dead set on this just buy yourself a ferrari V8 and stuff it in there you can find one for about $20,000, they have al the flat plane noise you want, or hell just spend $30,000 and put in a v12 from a 550 and you then have added cylinders and a flat plane crank and it will be allot more sound then something put together by a DIYer with parts from the local machine shop and the JE piston catalog.
I think there are other things to put your attention to on these engines that will give you far greater bang for your buck, what with displacement, cams, valves intake system, exhaust, hell the crank is probably the last thing in the world that the 928 could use improved upon honestly, most people would replace rods pistons valves intake all that crap before messing around with crank design, but if you have money to burn, by all means go for it.
08-21-2006, 06:11 AM
#23
Addict
Rennlist Member
Rennlist Member
550 and any other V12 Ferrari all have normal V12 cranks. Nothing special or out of the ordinary in there. Boxer and Testarossa have 180 degree V12 crank instead of true boxer engine but that's other matter. Ferrari didn't change anything special in their 3L V8 when they did cross plane version for Lancia Thema 8.32. For $20k one gets entire V8 Ferrari like 308 or Mondial, not just engine.
All it would take in 928 is new crank and different cams. All else can remain exact same except firing order. No need to make different heads or anything else. Stock exhaust would work fine. Sound would be clearly different, peak hp would be little higher and occur in higher rpm. Low end torque would be lower as a tradeoff. Easiest way to do it is to order billet crank from Moldex. Might cost little more than standard stroker crank. Nothing magical about it.
All it would take in 928 is new crank and different cams. All else can remain exact same except firing order. No need to make different heads or anything else. Stock exhaust would work fine. Sound would be clearly different, peak hp would be little higher and occur in higher rpm. Low end torque would be lower as a tradeoff. Easiest way to do it is to order billet crank from Moldex. Might cost little more than standard stroker crank. Nothing magical about it.
08-21-2006, 07:47 AM
#25
Addict
Rennlist Member
Rennlist Member
Originally Posted by Normy
Yes you can do it but why would you want t?
It's true there are easier ways to get few hp more but very few are more interesting ones. Whole point in my last reply was that it's not some rocket science which require huge amount of modifications.
08-21-2006, 08:09 AM
#26
Banned
Join Date: Feb 2002
Location: Ft. Lauderdale FLORIDA
Posts: 5,248
Likes: 0
Received 4 Likes
on
3 Posts
Originally Posted by Vilhuer
Because you can.
It's true there are easier ways to get few hp more but very few are more interesting ones. Whole point in my last reply was that it's not some rocket science which require huge amount of modifications.
It's true there are easier ways to get few hp more but very few are more interesting ones. Whole point in my last reply was that it's not some rocket science which require huge amount of modifications.
N!
PS: Anyone have a good recipe for turkey burgers? I've got a couple that deal with onions and shallots.....
08-21-2006, 08:54 AM
#27
Gluteus Maximus
Rennlist Member
Rennlist Member
Thread Starter
Join Date: Nov 2004
Posts: 6,365
Likes: 0
Received 0 Likes
on
0 Posts
To me the 928 offers a unique opportunity to try this since there are interchangable 4 cylinder heads. I'm not aware of any other mass produced V8/I4 combo like this.
As such, it must be done.
As such, it must be done.
08-21-2006, 09:37 AM
#28
Gluteus Maximus
Rennlist Member
Rennlist Member
Thread Starter
Join Date: Nov 2004
Posts: 6,365
Likes: 0
Received 0 Likes
on
0 Posts
Originally Posted by Normy
My understanding on this is that:
1. An even-firing V8 like the one in the 928 [Ferrari V8 engines do not fire with even intervals; the time between firings varies due to the flat plane crank] has quite a bit less vibration, and
1. An even-firing V8 like the one in the 928 [Ferrari V8 engines do not fire with even intervals; the time between firings varies due to the flat plane crank] has quite a bit less vibration, and
The vibration in a flatpane is due to a 2nd order (ie, small) effect - caused by the connecting rods - which also affects any inline 4 cylinder, and can be prevented with balance shafts. The vibration is small enough that racing engines, motorcycle engines, and small car engines (less than 2L) don't need balance shafts. However the vibration does get stonger with heavier pistons, so bigger non-race inline 4's usually have them. Not sure how much vibration there will be in a 928 w/o balance shafts.
Originally Posted by Normy
2. An even-firing V8 has better intake characteristics at the lower engine speeds that the M28 normally exists at. At higher RPM's the flat plane breathes better; that is why the stock-block based Infinity V8's at Indy run a flat plane crank while the cars are normal even-firing. Then again...what RPM's do those Indy V8's run at-?
However, this does bring up an interesting point that a stock 32v intake wouldn't work well for a flatplane (ITBs anyone?). For the 16v, with it's common plenum, this wouldn't be a problem. Infact it would make it easier to convert a 16v into a dual plenum just by putting a divider in the plenum.
The exhaust on a crossplane would be similarly improved by tying together the two banks like a 32v intake. However this is very hard to do on a crossplane V8. Tom the Powerbroker did this and saw an almost 50 ft-lb. torque increase (note to make use of the better exhaust he also added a piggy-back).
Note the complicated piping and the fact that the headers have to be very long to make this work. A flatplane would give you this same increase with normal headers.
08-21-2006, 10:06 AM
#29
Drifting
I think its a great idea. Go ahead and keep us informed just like greg does and the FI guys. Then we will all have alternatives to spice up our cars if we choose. What about a hybrid deal with the lighter materials greg is using combined with this flat plane crank? I hope you give this a shot.
08-21-2006, 11:29 AM
#30
Nordschleife Master
Join Date: Sep 2004
Location: Not close enough to VIR.
Posts: 9,429
Likes: 0
Received 2 Likes
on
2 Posts
Originally Posted by sublimate
To me the 928 offers a unique opportunity to try this since there are interchangable 4 cylinder heads. I'm not aware of any other mass produced V8/I4 combo like this.
As such, it must be done.
As such, it must be done.
I think this would be a great idea for somebody already looking at building a stroker. I wouldn't think the cost would be much different and in theory should be less than a dual plane forged crank.