Building your own flat-plane "P65" engine

[Green-Eggs]

Building your own flat-plane "P65" engine

Introduction:
It's time to unveil a project we've mentioned here and there, but haven't been ready to talk about. We wanted it to get far enough along to ensure it would become a reality.

Background:
Almost all V8's produced are built in a "cross-plane" configuration. A cross-plane crank positions the rod journals every 90-degrees. Because of the 90-degree positions, large counterweights are required to balance the crankshaft. A cross-plane runs very smooth and is easy to manufacture. Most importantly, cross-plane engines are very reliable and have that throaty V8 sound everybody knows and loves.

What is a flat-plane crank?
A flat plane crank is different. Instead of rod journals positioned every 90-degrees, a flat-plane crank positions the rod journals every 180-degrees. The flat-plane crank can come in different configurations, but the most common is Up-Down-Down-Up -- exactly like two banks of 4-cylinder engines. The flat-plane crank has smaller counter weights, so it is much lighter. Lighter means it revs higher too. Higher revs typically means more power.

If you've ever driven next to a Ferrari and noticed it sounds totally different than any other engine you've ever heard, most likely you've been listening to a flat-plane crank engine. Besides Ferrari, the Shelby Mustang GT350 and GT350R use a plat-plane crank. That's how rare it is to find a flat-plane crank in a production car.

There are downsides to a flat-plane crank; the biggest is vibrations. Even though it's inherently balanced, engine builders like to say a flat-plane engine wants to saw itself in half. So now you go back to slightly larger counterweights, and very precise balancing to fix it.

Another concern is the V8 configuration. V8's typically come in 90-degrees. But some V8's are configured as 45, 60, and 72-degrees. Because the flat-plane crankshaft has it's rod centers every 180-degrees, only a 90-degree V8 can be converted to a flat-plane engine. The S65 is a 90-degree V8.

Here's a short video that visually shows the difference between a cross-plane and flat-plane crankshaft.

Building your own flat-plane engine
There are many obstacles to building a flat-plane engine. Assuming you can get a custom made flat-plane crank, you still need to get the camshafts to match. You can't use factory camshafts built for a cross-plane crank because the firing order is very different and assumed to be every 90-degrees. On the S65, this presents a very big problem: where do you get the flat-plane cams? It's not like you can call up your local BMW performance shop and order them. These cams must be custom made, or made by somebody who has S65 cam blanks and can make them with 180-degree firing order.

But suppose you can get the crank and cams, you might need to change the valve train components too: cam followers, valve springs, maybe even need to change the valves (depending on which cam followers you choose). If you're going to this much of an expense to build a flat-plane engine, it's doubtful you'll want to use the heavier hydraulic lifters in the factory S65. Most likely you'll want to change the lifters to mechanical with a radius cup (radius cup reduces wear). That's when it gets interesting. Whatever cams you make, they must match the valve train. You can't buy cams for mechanical lifters with radius cups and use them either on hydraulic lifters or lifters with a flat cup. The cams and cam followers must be thought out and built to match each other.

Since the flat-plane engine has a different firing order, you'll need to solve that problem too. There's three ways to solve it: 1) rewire the harness to change the order of the coils and injectors; 2) convince the MSS60 to change the firing order; 3) use a standalone ECU. All three of these are pretty straight forward.

Now that you've decided to move forward, it's time to order the parts.

How this project got started:
This project is Bert's: Bert @ BEBearings. We (Auto Talent) work with Bert and help him with parts, and occasionally lend him our engine builder. Bert started this project over a year ago, but I think he got the idea long before that. Bert also works with Dinan for machine shop work, and knew they had shut down their P65 race engine program. The P65 is BMW's flat-plane S65 racing engine.

I asked Bert why he wanted to do this, and he said: "because nobody's done it before."

Some time in 2016 Bert was at Dinan taking care of Sergei's S65 engine dyno when he asked if he could photograph the flat plane crank. Fast forward a year or so, and Bert was back at Dinan to pick up a machined block when he asked Dinan if they had any spare P65 parts they'd be willing to sell. Specifically he needed the cams because that's the part Bert couldn't get made by himself. Surprisingly, a deal was made that day to buy an 83mm flat-plane crank and full set of cams at a very reasonable price. Bert walked out happy.

P65 in 2018/2019
Worried that the 83mm crank was too much stroke, Bert wanted to have a new crank made at 81mm. Bert contacted Van Dyne Engineering and had them order an 81mm flat-plane crank, a set of rods, and set of pistons.

With Van Dyne's advice, Bert decided that the crankshaft would not be designed to use a BMW rod journal. Instead this design uses a smaller and well know racing journal that has many different sizes of over/under sized bearings available. This approach solves three problems: it lightens the rotating mass of the crankshaft, adds a little more surface area because the bearings are wider, and allows Van Dyne to dial in the clearance to anything they want. Clevite offered to donate the bearings for the project.

The Carrillo connecting rods were made to match the race journal size crankshaft. Due to the smaller rod big-end, the connecting rods are noticeably lighter than a standard Carrillo S65 connecting rod.

The pistons were made by CP-Carrillo using the PD-14 coating to make it compatible with the BMW Alucil block. The pistons are 93mm bore.

Total displacement is 4402 CC's.

Solving the valve train issue:
Since these Schrick cams were already made for the P65 race engine, the specs were unknown. We had no idea of the lift, duration, and whether they required hydraulic lifters versus mechanical lifters or required a radius cup versus flat cup. After multiple emails back and forth with Schrick, the specs were given as follows:

12.6mm lift, 292-degrees duration, mechanical lifters, radius cup. Schrick provided the firing order with the specs of the cams (very helpful).

Those are great specs, but they present big problems. The cam followers ("lifters") Dinan used were supplied by BMW Motorsport, manufactured by Del West, and measure 32mm diameter. The factory hydraulic lifters are 28mm diameter. So either we need to machine the head for the 32mm cam followers, have a batch of cam followers custom made, or figure out another solution. Dinan insisted the factory S65 head and racing P65 heads, though 95% identical, are not compatible to machine the cam follower bores to 32mm. Bert remained skeptical, but without a full set of the 32mm Del West followers, it was a moot point. (Dinan provided one sample as a loaner.) Bert contacted various manufacturers who make cam followers, and was told they could make anything except a radius cup. Luckily a solution presented itself to "do something else" -- but we're not saying what it is. All we can say is that it's a rock solid proven solution and guaranteed to work. It's even rather inexpensive.

Del West Cam followers



Using this "rock solid" solution also means we can keep the factory valves. If we had custom made cam followers, almost surely we would also have to replace the valves with longer tip valves. The lucky solution allows us to keep the factory valves, save the money, and use the Schrick racing valve springs to match the cams.

The block and final bits and pieces:
Once the pistons arrived, the block was sent to Dinan for bore/hone. The block was returned and ready for use. The only remaining delay was for the crankshaft to finish being manufactured.

The crankshaft took 6-months to make, and cost about 20% more than a typical stroker crankshaft. The crankshaft was completed early December 2018 and immediately picked up. Bert drove down to Van Dyne to inspect it, shoot some photos, and get ready for the build.

Everything is in place. The block is bored; the crankshaft, rods, pistons are all made. Cams are ready and the valve train is not an issue. The engine is ready to assemble. The build will start in early 2019.

Best news of all:
Probably the best news of all is Schrick is willing to make more of these cams (if you know what they are and how to order them). These are not cams found on the shelf, and you cannot call Schick and ask them to make you a set. Through his contacts with Schrick, they promised to make Bert more cams if he wants. Bert already has two people lined up, asking for a flat-plane S65 of their own. The 83mm flat-plane crank Bert didn't use, is already sold and should be appearing sometime later in it's own P65 project.

Pictures: (click the pictures to enlarge)

Full Photo Album:
http://www.rcollins-home.org/photobu....php?album=279

Flat-Plane Crankshaft


Connecting Rods


Pistons


Camshafts


All Together Now




What does a flat-plane S65 sound like? Enjoy!

[StripclubDJ]

The main question , we ALL have....







Which rod bearings are best for this
Wpc,vac,or BE.




Lmao
Jk
Nice work

[Aktavate]

Very cool project, cant wait to hear/see this thing running!

[Shmelgy]

Wow

[VictorH]

Super cool project. Are you taking the opportunity to use different sized crank main bearing journals rather than BMW spec?

What's the approach for the exhaust headers and how will you optimize those?

[LostPanda]

Well I guess I have a reason to start saving monies now...

[deansbimmer]

Thanks for posting it and not keeping this a secret. Have wanted to do this for a while, glad to see someone bringing it to life!

Strokers? Meh... Flat plane builds are the new cool.

[EnVe46]

What a project! Tuned in for more

[jcolley]

Originally Posted by Green-Eggs

Bert already has two people lined up, asking for a flat-plane S65 of their own.

Who on earth would that be?

[Makaveli7]

what a project! so happy to hear that schrick is accepting to do these in the future!

Sorry if this sounds incorrect but would the flat crank setup freeze the Vanos in 1 place now ? and would the 4.4 and flat crank use a vibration damper?

[tdott]

Amazing.

[SYT_Shadow]

This is killing me!! Do it already!!!

Thank you Bert for always pushing the envelope of BMW M engines!

[M3 Number 86]

///F3RRARI lol

[Richbot]

I have a raging pulsating nerd-on

[serranot]

I asked RRT about building me a flat plane engine. I can’t believe this is happening. Timing for me is awful but would buy in another life.

Curious what you will use to run the engine. Can you revise the stock engine computer?

[IanMan]

Originally Posted by serranot

I asked RRT about building me a flat plane engine. I can’t believe this is happening. Timing for me is awful but would buy in another life.

Curious what you will use to run the engine. Can you revise the stock engine computer?

Honestly, if you're going to go all out and build a flat plane engine, you might as well run a standalone engine management system that doesn't hold you back in certain aspects.

[roastbeef]

Pardon my ignorance, but if you aren't stroking it, what is the benefit? (Besides being cool)

[GORDON.M3]

This is amazing, way better than supercharger kits!

[Redd]

Originally Posted by roastbeef

Pardon my ignorance, but if you aren't stroking it, what is the benefit? (Besides being cool)

Higher rpm power?

[M3SQRD]

Originally Posted by roastbeef

Pardon my ignorance, but if you aren't stroking it, what is the benefit? (Besides being cool)

It is...4.4 L

[derbo]

oh this is going to be good.

[serranot]

Originally Posted by roastbeef

Pardon my ignorance, but if you aren't stroking it, what is the benefit? (Besides being cool)

I would think a flat plane crank would be lighter than a cross plane because of the lack of balance weights. For starters.