Thoughts of a flat-plane V8.

[Looneybomber]

For those that don't know, many of the european sports cars use flat-plane cranks as opposed to the more american cross plane crank. Think Ferrari sound vs. mustang cobra sound.
http://en.wikipedia.org/wiki/V8_engine
[youtube]http://www.youtube.com/watch?v=MwUnXOboPFI[/youtube]

So, bored here at work I got to thinking about converting a Ford 4.6DOHC into a flat plane design. I was thinking about the parts that would need to be changed. All I could think of, if doing it on a budget, would be the crank and cams, assuming most balancing could be done by the crank. After doing more research, I came across this...

Lingenfelter flat-plane LSx.
http://www.lingenfelter.com/LPEforumfil ... .php?t=899
http://www.lingenfelter.com/LPEforumfil ... .php?t=904

Why would I like a flat plane v8? The sound. Listening to the engine above, it still does not have the italian sports car sound despite the similar rev range. The next step would be tuning the exhaust and intake runners.

[MinisterofDOOM]

I've always wondered why more performance V8s (and bigger) aren't flat-plane. Sure in many applications, the smoother running provided by the offset-angled crank makes sense. But not in a ZR1 or Viper.

Interesting tidbit:
McLaren's Nissan-derived M838t has a flat plane. It sounds exactly how I'd expect a flat-plane VH35 to sound. Listen:
[youtube]http://www.youtube.com/watch?v=4YJVAagU9yY[/youtube]

[RCA]

Why would I like a flat plane v8? The sound. Listening to the engine above, it still does not have the italian sports car sound despite the similar rev range. The next step would be tuning the exhaust and intake runners.

That is a lot of work for an exhaust note.

I would shoot for a V8 that has 3.5L or less. Take that to 10,000rpm

[Looneybomber]

I would shoot for a V8 that has 3.5L or less. Take that to 10,000rpm

Funny you should mention that. Powertec makes an engine (3.2L) that will rev past 10k. I don't know if this vid is of the 2.7L or the 3.2L. Originally they mated two Hayabusa engines together and stuck with the flat plane design and have progressed from there.
[youtube]http://www.youtube.com/watch?v=f70AeryyDAE[/youtube]

I think the key is figuring out header tube lengths so that all eight combine with evenly spaced pulses? After that, you'll have to tune the silencer so that it creates increased 2nd and 4th order harmonics (because the odd order harmonics tend to be displeasing), and/or create chambers which will resonate at specific frequencies...

I think it would be a fun project, so long as I could get funding. The conversion to a flat-plane is just a whole lot of math and then some testing. The creation of the exhaust is, again, more math and then listening once the engine is done, tuning it like an instrument. It would make for an awesome senior project, but too bad I'm going electrical and not mechanical.

[RCA]

That car sounds awesome.

By the looks of it, your solution is more acoustic based than it is L/cylinder. Just thinking about the math involved hurts my head a bit but if you attempt this I will definitely be a cheerleader. Epic project will be epic.

[Looneybomber]

That car sounds awesome.

By the looks of it, your solution is more acoustic based than it is L/cylinder. Just thinking about the math involved hurts my head a bit but if you attempt this I will definitely be a cheerleader. Epic project will be epic.

I doubt that 1. the school will let me (because I don't have money to spend on a project like this without having a platform to put the engine in) and 2. I would have the capability to pull something like this off correctly (wrong field of study). I was just curious, although I would love to pull something like this off. However, if the only thing that needed to be done was cams and crank, it could be possible.

I have seen projects that involved hybrid and all electric designs, which makes sense for electrical engineering. As a senior project, maybe I could attempt my turbine powered hybrid I've been thinking about for a couple years. Honestly, the turbine powered hybrid/electric car has real world potential and a flat-plane v8 conversion is just a flavor-of-the-week idea that I have.

[MinisterofDOOM]

I think the key is figuring out header tube lengths so that all eight combine with evenly spaced pulses?

You can do this without a flat-plane crank, too. 180-degree headers.

[youtube]http://www.youtube.com/watch?v=KXSrWWQGzzE[/youtube]

[Looneybomber]

I think the key is figuring out header tube lengths so that all eight combine with evenly spaced pulses?

You can do this without a flat-plane crank, too. 180-degree headers.

Holy crap that sounds good. However, it's still very lopey like normal american V8s. I think you'd need a combo of the even flat-plane firing order and lots of header and exhaust tuning. I have a feeling resonators will need to be tuned to a high frequency which goes against conventional american thinking of low deep rumble bumble.

[MinisterofDOOM]

The lopeyness of the GT40 is due to the design of the engine itself, not the headers. It IS an American V8. It just has 180 degree headers. Slap them on a more "exotic" DOHC V8 and it sounds like a more exotic DOHC V8 with 180 degree headers.

[Looneybomber]

Well yeah, the lopey staggered fire is by design, but the deeper rumble could be mitigated with different muffler tuning...although that would be counter productive for gt40. Going to a dohc v8 would help, but that firing order would also need to be modified to smooth it out.

I wonder, with some nicely tuned exhaust, how close a 98, 01 cobra could sound in comparison to say an F430...

In related fashion, in '09, yamaha went from a flat-plane crank in their R1 to a cross-plane and the sound difference is dramatic (and not very pleasing IMO).

[youtube]http://www.youtube.com/watch?v=-CILvXMartA[/youtube]

[youtube]http://www.youtube.com/watch?v=ofxXsoZ3uH8[/youtube]
At 1:15 that Honda is a vtwin so you can compare it with the I4 crossplane and the gixxer I4 flatplane.