Ah,if racing were about which car sounded best..
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Originally Posted by thirtythird
(Post 1577999830)
Ah,if racing were about which car sounded best..
http://www.youtube.com/watch?v=hoXuoARdX74 |
The major draw back of the flat plane (or more correctly) 180 degree crank is a major increase in engine vibration harmonics. Its main benefit is it isolates the two sets of adjoining intake runners and two sets of exhaust ports that fire next to each other in sequence with the 90 degree crank instead of being evenly spaced and alternating in the 180 degree crank. A 180 degree header solves the exhaust side but not the intake side. A 60 degree V-12 (Ferrari V-12/P-51 Rolls Merlin) is naturally timed and naturally balanced and creates that silky smooth, gorgeous purr that sounds so good. A 180 degree crank is naturally timed but not naturally balanced so it sounds good but has a lot of internal stress in the crank.
Gary |
There's nothing like the scream of the old V12's. The engines they have now, and AFAIK what they are moving to next year, even smaller, are just dull.
Originally Posted by Hercules Rockefeller
(Post 1578000235)
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http://www.kingscrankshaft.com/kings...ft_llc_009.htm - They can do one for USD$2500.
I've been given the name of CHRIS PADGETT to talk to at Comp Cams to do the billett cam for it. From memory lingefelter have comp cams make their cams for them, so I'll touch base with them to see what they can do for a tuning package. Anyone know if the factory ECU can have its firing order modified, or do I ditch it out and put in a Link or such instead? |
It would be easier to just lengthen the wires on the harness so you can move the coil connectors to the new firing order.
Gary |
Are there any figures that show flatplane to crossplane and why the torque is so much different?
I can see why the ferrari engines have less torque, as they have a very short stroke in comparison to the LS7, but theoretically I would have figured the LS7 flatplane would keep the same torque, just be able to spin up faster. Going to have to talk to some tuners to see what comparable figures there are.
Originally Posted by AirBusPilot
(Post 1577493039)
You forgot to add that it takes RPM, very high RPM, to be able to use the short gearing needed to get the at the wheels torque up. That high rpm comes at a price.
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Ah, good call!! Someones thinking....
Originally Posted by 40YRW8
(Post 1578009114)
It would be easier to just lengthen the wires on the harness so you can move the coil connectors to the new firing order.
Gary |
The exhaust note...
As a 31 year locomotive field service mechanic...I can tell you that the crank design has nothing to do with the exhaust note...Its all about how many cylinders you have, the design of the combustion chamber and specific exhaust system you run.
Originally Posted by Hercules Rockefeller
(Post 1577487121)
Would it be possible, when rebuilding an LS7, to build up the motor with a flat plane crank as opposed to the standard cross plane crank that comes with the stock motor? As far as I know, no matter what exhaust, headers, etc you use, the cross plane crank is the primary reason we can never get that wild sound you expect from a high end exotic or a real racing motors. Most high end motors, and practically all racing motors (except NASCAR of course), use flat plane cranks while cheaper less exotic engines (i.e. everything from trucks to vettes) use cross plane.
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Very true...180 degree headers have the similar effect on this C5 here:
http://www.youtube.com/watch?v=MSZTbR6C6Lw So far easier, if your doing this for sound, than a whole new crank, cam, exhaust, and tuning solution. I'm looking at it for the throttle response and overall performance, but yet to see exact figures that show which was is better for my purposes. For out and out performance I've seen that flat-plane is the way to go, but for all around purpose, cross-plane works just as well. |
Originally Posted by Bud Meyer
(Post 1578010323)
As a 31 year locomotive field service mechanic...I can tell you that the crank design has nothing to do with the exhaust note...Its all about how many cylinders you have, the design of the combustion chamber and specific exhaust system you run.
Here's a video clip that perfectly illustrates the difference in sound I'm talking about. Both cars have V8's, but the first is clearly the sound of a flat plane crank, and the second is the sound of the cross plane crank in the LS7: http://s1134.photobucket.com/albums/...ossPlaneV8.mp4 What I want is for my exhaust to sound like the note we hear earlier in the video. And I'm sure I'm not the only one. |
That vids not the best comparison, seeing as its a vette in the foreground, and we dont know what the car in the background is.
It would need to be a LS7 vette as well, at the same rev's to be able to compare. If your just after the sound, research "180 degree headers", which will get you the sound if thats what your after. ( check my vid link above ). I'm researching this more for the response and power capabilities than anything else. If, by what is becoming apparent, throttle response, and power curve is snappier, then thats what I want. This matched to ITB's and the right exhaust setup to make the most of it is what I want. |
To each there own of course but it seems like a pretty big mod just for exhaust sound. I'm not so sure that many 'Vette owners want the car to sound like a Ferrari instead of the V8 muscle it is. :thumbs:
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I'm not doing this for the exhaust sound, a 180 degree header would achieve this.
There's potential throttle response, and power-band benefits with moving to a flat plane crank that I'm researching. It's possible this will be with a minor loss of torque at low-rpm, but over-come with a wider more progressive torque curve....thats the part that I'm confirming. And to be honest, USD$2500 for a crank, a bit more than normal for cams, is a lot less that what some people will spend on pretty rims. I dont do normal, and frankly the vette V8 sounds the way it does because the design is in-efficient. If it was the way to go, most exotic high performance cars would use it, but they dont, they use flat plane. Same if not more horsepower with smaller engines. So, if I go flat plane, with larger capacity ( LS7 ), I should theoretically have a faster responding, high horsepower engine, and this is before I get to work on ITB's and more down the track. |
One of the better descriptions on the difference....its regarding bikes, but I'm thinking the overall theory applies:
http://darkriderindia.blogspot.com/2...rankshaft.html |
Here's a question. If you had a 90 degree flat plane crank V8, would the crankshaft essentially be the same configuration as a cross plane straight 8?
Also, while the 180 degree header does sound interesting, it still doesn't have that flat plane sound (but then again, it's hard to tell what something sounds like in real life until you hear it in person). |
So what is the goal for this build? Do it for the sake of having done it? Do you want to make X amount of power?
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Originally Posted by SteveRiellyNZ
(Post 1578012143)
I'm not doing this for the exhaust sound, a 180 degree header would achieve this.
There's potential throttle response, and power-band benefits with moving to a flat plane crank that I'm researching. It's possible this will be with a minor loss of torque at low-rpm, but over-come with a wider more progressive torque curve....thats the part that I'm confirming. And to be honest, USD$2500 for a crank, a bit more than normal for cams, is a lot less that what some people will spend on pretty rims. I dont do normal, and frankly the vette V8 sounds the way it does because the design is in-efficient. If it was the way to go, most exotic high performance cars would use it, but they dont, they use flat plane. Same if not more horsepower with smaller engines. So, if I go flat plane, with larger capacity ( LS7 ), I should theoretically have a faster responding, high horsepower engine, and this is before I get to work on ITB's and more down the track. Speaking of free! If you get a .25M minimum order of flat plane cranks, you'd likely see a $2500 per unit rate... else it's gonna be mad expensive. I'd be curious how one would even go about slapping balance shafts into the mix. edit: IIRC, NASCAR experimented with flat-planes and well, there's a reason that "low brow non-exotic" engine still outclasses a heck of a lot of Euro engines. |
Yes, flat plane came first, and it was two american car companies (Cadillac and peerless ) that came up with cross plane. They tried to patent it each, and ended up agreeing to share.
Due to the firing order a balancing shaft isn't needed, hence cheaper development costs, but does require the heavy counter weights. http://en.wikipedia.org/wiki/Crossplane It also does say that most racing teams use flat plane ( they're not to fussed about balancing really ), and from what research I've done, with the right associated forged, light weight components, the extra vibration would be minimal. What I would lose in a bit of low end torque ( and I do mean just a little bit ), I would potentially gain in a wider, faster responding, more usable powerband. Its that faster responding part that really interests me. I would have overall about the same torque, but faster access to it. In track work I "think" this would mean when two comparable cars are powering out of a corner, the cross plane would have slightly more torque, which would equate to extra power, but its going to be accelerating slower that the flatplane, which has slightly less torque, but is climbing up in revs' faster. That's the theory anyway, and what I'm trying to find actual provable figures that show exactly that, or that its not the case. There's a lot of "this is how it works", but from people that are just stating what they think, not what they've actually tested and know for fact. |
Originally Posted by OKsweetrides
(Post 1578032553)
IIRC, NASCAR experimented with flat-planes and well, there's a reason that "low brow non-exotic" engine still outclasses a heck of a lot of Euro engines.
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