35 replies to this topic

[Almag]

Ford is releasing a flat-plane crank 5.2-liter V8 in the upcoming GT350.

 

One curiosity about Ford's crank - the layout they're using is unusual. The throws do not have the usual inline-four-cyl-like "up down down up" pattern we're using to seeing in Ferrari and, well, any other flat plane crank V8 I can think of. Ford's crank is "up down up down". Are you visualizing this?

 

This results in a different firing order and sound... but it would seem to me to also have a negative effect on vibration. Namely it would introduce a first order rocking moment from end to end; something not found in the traditional FPC layout. Can anyone confirm that this would indeed be the case, or what's going on here? 

Edited by Almag, 14 January 2015 - 23:24.

[Greg Locock]

got a picture?

[Almag]

More images here: 

http://www.enginelab...ne-photos-here/

http://www.hotrod.co...-crank-5-2l-v8/

 

[desmo]

The pistons look almost like F1 pistons from maybe 20 years ago.

[pugfan]

You could use 2 counter rotating shafts at double engine speed to balance a 'traditional' flat plane v8, or, you could use a single counter rotating shaft (to engine rotation) to balance this sort of flat plane v8, ala I3.

 

Edit: It's hard to tell from the photo posted but I wouldn't have said that was flat plane. None of the photos in the links look conclusive either.

 

Edit Edit: Oops, I think you only need one counter rotating shaft at twice engine speed for a 'traditional' flat plane v8 versus 2 for a I4.

Edited by pugfan, 15 January 2015 - 04:54.

[BlinkyMcSquinty]

I found this interesting post concerning this very situation.

 

http://www.bimmerfor...8886-Flat-crank

 

The only reasons for this sacrifice in introducing a new set of vibrations could be the exhaust sound (it would be very unique) or to tune the firing order for some presently unknown performance increase. Could there be some enhancement within the intake manifold due to the manner of pulses? The intake manifold is common to all eight cylinders, so there would be a resonance effect going on.

 

Is there a NASCAR influence, with their Tri-Y exhausts? The engine does have a variation of the Tri-Y, but the collectors do not meet equally.

 

 

This has become an interesting engine.

[manolis]

Hello BlinkyMcSquinty

The two arrangements:

L-R-R-L and L-R-L-R (post #6)

have the same inertia vibrations:

a strong inertia force of 2nd order (if it is to be completely balanced, it requires a pair of counter-rotating balance webs rotating at double crankshaft speed),
a weak inertia moment of 2nd order (it comes from the offset of the connecting rods that share the same crankpin),
a negligible 4th order inertia torque.

In comparison, the conventional V-8 with the cross-plane crankshaft is rid of the inertia force and of the inertia moment abovementioned.

The difference between the L-R-R-L arrangement (Ferrari etc) and the L-R-L-R is in the balance webs of the crankshaft.
The first needs not balance webs (so the crankshaft can be lightweight), while the second needs relatively heavy balance webs (about 60% of those used in the conventional V-8 with the cross-plane crankshaft) otherwise it suffers from a strong unbalanced rotating 1st order inertia moment.

Easy to check with the balance.exe program at Teaching section of the http://www.pattakon.com website.

Thanks
Manolis Pattakosi

Edited by manolis, 15 January 2015 - 06:08.

[Lee Nicolle]

The pistons look almost like F1 pistons from maybe 20 years ago.

The rods look like rods from 60 years ago. And are probably the 'cracked' metal type. So are probably worse than 60 years ago!

[gruntguru]

It says somewhere they are sintered so quite possibly "cracked caps" as well.

[BJHF1]

Whatever the case, this engine will most likely (imo) be far more reliable and cheaper to maintain than any European V8 revving north of 8000rpm 

Edited by BJHF1, 18 January 2015 - 19:50.

[gruntguru]

Does anyone have information on the reliaility of sintered rods or cracked caps?

[PJGD]

Several heavy duty diesel engines that are designed to go >1 million km between overhauls use cracked rods.  They make for a much more rigid joint than dowelled, stepped, or saw-tooth joints.

[gruntguru]

That makes sense - thanks.

[bigleagueslider]

Does anyone have information on the reliaility of sintered rods or cracked caps?

PM steel conrods have been widely used in the auto industry for many years. Not as good as forged steel conrods in fatigue, but definitely much cheaper to mass produce, and better than cast conrods both in terms of fatigue and cost. Also, PM steel conrods can be made extremely lightweight since it is easy to mold very detailed features in the pre-formed part. These conrods also use a cracked joint because it is low cost and provides very precise alignment when re-assembled.

[Lee Nicolle]

PM steel conrods have been widely used in the auto industry for many years. Not as good as forged steel conrods in fatigue, but definitely much cheaper to mass produce, and better than cast conrods both in terms of fatigue and cost. Also, PM steel conrods can be made extremely lightweight since it is easy to mold very detailed features in the pre-formed part. These conrods also use a cracked joint because it is low cost and provides very precise alignment when re-assembled.

And are generally just ok for their application. A few engines these days have bad reps from weak rods. Read thes 'cracked metal' ones.

Eg Do not use them in any performance application. The cost of reasonable steel rods these days really means that using fragile factory items is unecesary. They are at best a one time item. 

[BJHF1]

Not bad for a stock unopened engine with sintered rods  ....

 

[gruntguru]

. . .  stock unopened . . . . 

i.e. - not a performance application.

[Lee Nicolle]

Several heavy duty diesel engines that are designed to go >1 million km between overhauls use cracked rods.  They make for a much more rigid joint than dowelled, stepped, or saw-tooth joints.

Low RPM under stressed road engines. Do not pull them apart and reuse them however. Though to be fair if maintaned properly they do not need to be.

Performance orientation though is different. The alloy Chev v8s in particular have a poor reputation even as standard engines. most performance use requires aftermarket steel rods. unlike the old Small Block that the factory rods were good [when in good order] for 7000 plus RPM. Though good aftermarket rods there is still preferred. 

I have heard the same stories about a few others. But have seen broken late Chev ones that seem to have broken for no real reason at 6000 rpm. Pistons seemed fine, bearings were fine but broken!  not pretty!

[Almag]

The rods in the Ford engine above appear to be forged (non PM) and cracked. This is done in closed die 'flashless' forgings.

 

They also appear to be steel. I expected Ti due to the long stroke (i.e. to help address the vibration). 

[Greg Locock]

I must live in some parallel universe, what is this "pull them apart and reuse them" for a standard road car lark?

[bigleagueslider]

Cracked conrods are assembled/disassembled a couple times during manufacture. After being fractured, they are reassembled to finish machine the bolt holes and bearing bore, since the fracturing process yields the material a bit. Then they are taken apart for cleaning, and finally put together again during the engine assembly.

[Lee Nicolle]

I must live in some parallel universe, what is this "pull them apart and reuse them" for a standard road car lark?

I show my age. I am used to be able to rebuild an engine not just bin it. Far too many engines are junk when they break where in the past you would rebuild/ recondition it.

And alloy Chevs are often rebuilt even now. Too rattly swap it out, in Commodores lousy sump design coupled with a too small pick up swap it out etc.

Most holden dealers have a V8 swap bay. not quite as bad as they were.

5.4 Modular Fords too are as bad.

Though both are being rebuilt in the factory to be used as another changeover.

Some Japanese and Korean makes too are having similar dramas. 

Though when a rod breaks they may save the heads!

[gruntguru]

Back in the day, when engines could be rebuilt, I remember a Holden HQ 6cyl might last 100,000 miles between rebuilds. A "rebuild" meant re-bore (the bores were totally"stuffed"), valve grind etc etc. This was providing the engine was lucky enough not to have disintegrated a piston and destroyed the block and crank. The rest of the car was simple and rugged and could probably survive several engine rebuilds.

 

Today, most engines last at least 300,000 km without ever opening the engine. By that time the (very complex) car is technically obsolete, ridden with electrical and electronic failures and unreliability and generally decayed to the point where it is far more economical to scrap it in favour of something a little younger. If the engine doesn't last that long, most engines in the wrecking yards will make a perfectly good substitute given the longevity so why rebuild? Furthermore, a new car these days, is far cheaper than the old HQ further reducing the economics of "rebuilding" all or part of it.

[Magoo]

I posed this very question to the Ford engine guys responsible for this deal today.

 

Their answer: Starting from scratch, there are three ways to do a flat crank in terms of up/down phasing of the pistons front rear Up = U; Down = D. 

 

UUDD 

UDDU (conventional 4-cyl crank) 

UDUD

 

Upon running through all the analytics, they found that UDUD created the least amount of cylinder-to-cylinder variation and interference, including within the common intake manifold plenum. So then they built two physical engines using two of these crank configurations (They wouldn't say which two, but it's not hard to guess) and ultimately, validated UDUD.

 

In the ensuing conversation, it was remarked that another flat crank road V8, the Ferrari California, runs a UDDU crank and a separate manifold plenum for each bank. FWIW. it was also noted that this is the largest flat crank V8 now in production by a good little bit. 5.2 liters, 94mm x 93mm. 

[Bob Riebe]

Flat-crank, hmm.

Will probably make the same sound you get when you pull a blade of crab-grass tight  and blow on it.

[gruntguru]

Many years ago I had the pleasure of see a couple of DFV powered F1 cars driven in a field of F5000s. Sure the DFV was higher revving but - OH - that sweet music of blown crab-grass.

 

BTW I have also heard a flat plane SB Chev in a field of 90 degree SB powered speedway cars. No rpm advantage but sweet nonetheless.

[Magoo]

Flat crank exhaust sound: 

 

 

https://youtu.be/mahe7UorTq8

[gruntguru]

Sweet.

[Bob Riebe]

It sounds like a MV Agusta 750 at about 4,000 rpm with GP pipes with the sound deadener removed but end caps on.

 

Ford is playing to the Euro crowd and that does make good monetary sense.

 

Grunt you would have liked an MV with chrome stubbie headers and muffler megaphones removed.

Let's just  say, when I came home from the bar, people a block away with doors closed knew I was home.

Edited by Bob Riebe, 08 June 2015 - 05:49.

[gruntguru]

I would have rushed out of my house just to hear you go by (and watch the neighbours shaking their fists at you).

[bigleagueslider]

Engines with even firing intervals always sound great. Conversely, the exhaust note of an engine with unequal firing intervals never sounds quite right. Personally, I can't stand the uneven exhaust note produced by the typical 60deg V-twin Harley engine.

 

It's pretty impresswive that Ford engineers managed to design a 5.2L production V8 engine with a flat-plane crank. But the configuration of the exhaust headers is a bit unusual.

 

I remember how much trouble Cosworth had with reliability of their 4.0L DFL V8 race engine.

[desmo]

Harley-Davidson is a 45 degree v-angle.

[bigleagueslider]

Harley-Davidson is a 45 degree v-angle.

OK, 45 degrees. Still sounds like crap.

[Catalina Park]

OK, 45 degrees. Still sounds like crap.

To be fair most air compressors sound that bad.

[Lee Nicolle]

Back in the day, when engines could be rebuilt, I remember a Holden HQ 6cyl might last 100,000 miles between rebuilds. A "rebuild" meant re-bore (the bores were totally"stuffed"), valve grind etc etc. This was providing the engine was lucky enough not to have disintegrated a piston and destroyed the block and crank. The rest of the car was simple and rugged and could probably survive several engine rebuilds.

 

Today, most engines last at least 300,000 km without ever opening the engine. By that time the (very complex) car is technically obsolete, ridden with electrical and electronic failures and unreliability and generally decayed to the point where it is far more economical to scrap it in favour of something a little younger. If the engine doesn't last that long, most engines in the wrecking yards will make a perfectly good substitute given the longevity so why rebuild? Furthermore, a new car these days, is far cheaper than the old HQ further reducing the economics of "rebuilding" all or part of it.

Lots of 70s cab engines did 600000km on LPG. Holdens, Falcons. Usually to be fair with some minor maintenance. Falcon cab engines still do those km.

BUT a cab engine seldom gets cold, seldom uses more than about 3000 rpm. So have a good reason to last many km.

Though many modern car engines last longer as a family car than in the past. But IF it fails is bin it. 

And since I am in the car trade I see too many modern engines being binned, in fact the whole car really as they are too high tech to repair

[gruntguru]

I see too many modern engines being binned, in fact the whole car really as they are too high tech to repair

Exactly my point. The engine usually outlasts the car so there is a supply of good, cheap used engines when one fails - so yes - bin it.