Anyone tried an aircooled Flat 8, With two fours? Options

[Brando]

QUOTE (Aaron Cox @ Feb 27 2006, 06:00 PM)

i wanna say thats a photoshop..... nice 907/908 motor

Ding ding ding! We have a winner! It is photochopped.

[ClayPerrine]

FINALLY!!!

I was wondering when someone would pickup on the errors in my picture. (IMG:http://www.914world.com/bbs2/html/emoticons/wink.gif)



I actually would LOVE to do this. I have been thinking about it for a long time. I want to make molds of a 911 case, and make wax castings to cut apart to stretch. Then make molds for the stretched cases and cast them.


I would use a 3.6L case. If I were to do this, I would want to go BIG displacement!!!

[Brian Mifsud]

Photoshopped??!! Well, if I were designing this thing in CAD, you'd do almost the equivalent in terms of "cutting and pasting" (well sort of)... this picture is excellent inspiration though for a very doable flat 8 using 911 parts and some off the shelf V8 stuff...


Mike.. think Propane, propane, Propane......

[ClayPerrine]

The crank would have to be custom made. That would be the big expense. The cams and cam carriers could be made from existing 911 parts. Just cut and paste using a welder and a dial indicator for the cams. Setup each cylinder as if it were #1. Get the cams onto the proper lift with the crank at the correct degree setting and weld them together.


Make an extended oil pump drive shaft, and a flat fan. Use a distributor cap from a mercedes v-8.


It's doable, it would just take time, paitence, and money.



And it would be REALLY cool in a 914....... 4.8L air cooled flat 8.

[ClayPerrine]

Mueller... you up for making a couple of custom cranks?


(IMG:http://www.914world.com/bbs2/html/emoticons/biggrin.gif)

[Thorshammer]

Well Actually no, never thought about doing a type four engine, However, my little devious mind has always wanted to do a three liter V8 using two Hyabusa (GSX1300 Suzuki) That have been over bored using a billet block and a custom crankcase and dry sump oiling system. Thought I would put it in a small formula car for hillclimbs. Used to get 260-280 out of 1480cc Bus motors back in the day, So I would say 475-480 on good gas would be the number. BTW, the reason you can't get double the hp is due to friction. More parts means more friction, there is a point of diminishing returns when it comes to adding cylinders. That it why many F1 cars stopped development on V12's. V10 WAS The best choice. now just freaking V 8's they suck.

The other idea I had was to use two FZR400 Yamaha Cylinders and heads and a custom made crank using the stock bore, but reducing the stroke so that I retained 640cc. This would give me a really nice bore to stroke ratio, and after some intake port epoxy and a scatter cam (one inlet valve opens before the other one to promote swirl) I think I could make 130-135 hp out of this one. Very cool. Counter rotating barrel valves, and injection with 4 valve cylinder heads. Very high tech, and very cool sounding. Would be a great FSAE engine. Little tiny gasps of air through that 20mm orifice. Yes, yes, yes, Oops I soiled myself.


(IMG:http://www.914world.com/bbs2/html/emoticons/smile.gif)

Erik Madsen

[Brian Mifsud]

Hi Clay,

When you say a custom crank MUST be used, is that because the Porsche head and barrels are at too wide a pitch(i.e spacing of journals vs barrel width)??

Otherwise, just customize the parts AROUND the cheap crank.....

Intention would NOT be to be a 908 replica, but just a powerful lightweight flat 8 that can slip into the engine compartment without hacking it all up...

[ClayPerrine]

QUOTE (Brian Mifsud @ Feb 27 2006, 08:42 PM)

Hi Clay, When you say a custom crank MUST be used, is that because the Porsche head and barrels are at too wide a pitch(i.e spacing of journals vs barrel width)?? Otherwise, just customize the parts AROUND the cheap crank.....

Nope. The porsche crank uses a separate rod journal for each cylinder. So we need to add 2 more rod journals and 2 more main journals.


I suppose you could cut up a BUNCH of 911 cranks and put together something that would work. But I would not try it with a custom made case.


And I don't know what firing order to use either.


This idea really gets me thinking... This would be SO cool with 4 dellorto/weber style throttle bodies and electronic fuel injection. Bet it would sound really nice too... (IMG:http://www.914world.com/bbs2/html/emoticons/drooley.gif)

[alpha434]

If you do a different firing order, then you'll have to do custom cams to match the new crank.

I would just offset one engine's crank 45 degrees. Exactly. Then no two cylinders are ever firing at once, and you could use a V8 ignition system, since all timing would be evenly spaced.

We're all lucky that flat engines are naturally counterbalanced.

[Brian Mifsud]

QUOTE (ClayPerrine @ Feb 27 2006, 06:46 PM)

QUOTE (Brian Mifsud @ Feb 27 2006, 08:42 PM) Hi Clay, When you say a custom crank MUST be used, is that because the Porsche head and barrels are at too wide a pitch(i.e spacing of journals vs barrel width)?? Otherwise, just customize the parts AROUND the cheap crank..... Nope. The porsche crank uses a separate rod journal for each cylinder. So we need to add 2 more rod journals and 2 more main journals. I suppose you could cut up a BUNCH of 911 cranks and put together something that would work. But I would not try it with a custom made case. And I don't know what firing order to use either. This idea really gets me thinking... This would be SO cool with 4 dellorto/weber style throttle bodies and electronic fuel injection. Bet it would sound really nice too... (IMG:http://www.914world.com/bbs2/html/emoticons/drooley.gif)

OKAY, so that IS because of the Pitch (or spacing) of the Porsche cylinder that THEY use individual journals.... That doesn't mean it MUST Be engineered that way from scratch. The OFFset of one bank to the other would dictate whether I needed to use individual journals.. since I could control the offset.. I COULD use the chevy crank...(and distributor, rods, flywheel... maybe more...)

[eeyore]

QUOTE (Thorshammer @ Feb 27 2006, 06:42 PM)

The other idea I had was to use two FZR400 Yamaha Cylinders and heads and a custom made crank using the stock bore, but reducing the stroke so that I retained 640cc.

Just in case you didn't know, somebody is most of the way there

Drysdale

[alpha434]

Can't use a chevy crank for a flat 8.

[rick 918-S]

Here's a thought, use a crank from a V8 engine like a Chevy small block. Build a case around it, and add cylinders and a custom cam. Easy peasy... (IMG:http://www.914world.com/bbs2/html/emoticons/cool_shades.gif) (IMG:http://www.914world.com/bbs2/html/emoticons/screwy.gif) (IMG:http://www.914world.com/bbs2/html/emoticons/assimilate.gif)

[ClayPerrine]

QUOTE (alpha434 @ Feb 27 2006, 08:51 PM)

If you do a different firing order, then you'll have to do custom cams to match the new crank. I would just offset one engine's crank 45 degrees. Exactly. Then no two cylinders are ever firing at once, and you could use a V8 ignition system, since all timing would be evenly spaced. We're all lucky that flat engines are naturally counterbalanced.

Won't work. It's not a type 4. It's a flat 6 that is getting stretched to a flat 8.


And I already covered how to get the cams correct.

[Brett W]

The 180 degree 8 has a problem with second order imballance. It will shake at most street rpm levels. Most of you guys don't want to deal with that.

The 917 12s had problems with harmonics and crank vibration. This is why the fan and oil pump are mounted in the middle of the engine. You have to do this to keep those items alive.

You are better off just buying a Porsche flat eight. They aren't that expensive, when you look at what is involved in making your own.

[Thorshammer]

One of the problems must be the design of a crank that does not extend the overall length of the engine by too much. This could be a major problem. It will probably have to use rods that are adjacent to each other liek a small block to keep the cylinder bore spacing decent.

As for the previous comment about bevel drive gear Carrera engines needing 40 hours to build. Yes that is true, if they are a new parts build up. However, if the time is taken upon disassembly to check tolerances and shims are kept in the proper order, then it is less than that. many Carrera Maestros (HA, HA, HA) keep the black art thing going to ensure no one else plays with them. Ensuring they have a place from now forth. But the main issue with 4 cam engines is parts availability or the ability to make some part that are NLA. This is the real issue. and thats why only two guys in the country do most of the 4 cam work. its either MT or CT, anything else is just a myth. (IMG:http://www.914world.com/bbs2/html/emoticons/unsure.gif)
If you can work on a bevel drive Ducati, you can work on a carrera 4 cam.

BTW, why not make the V8 Type four monster use some Ducati Desmo air cooled cylinder heads. I have built many of those engines, the best we ever got in 750cc form was about 90-92 hp depending on the day. Which would mean 225 hp or so from 2.0 liters and 450 from 4.0 liters.
Just a thought.

Erik Madsen

[alpha434]

Why we couldn't use a Chevy crank:

Counter balancing, and angle offsets for timing.


A 60 degree V8 with a firing order 1-2-3-4-5-6-7-8

and shaped like this

1----2
3----4
5----6
7----8

The crank is at 0deg for 1. The crank is machined so that the piston one is -30 deg off center. Two is 45-30=15. Three is 60. Four is 95.

[ClayPerrine]

QUOTE (Brett W @ Feb 27 2006, 08:56 PM)

The 180 degree 8 has a problem with second order imballance. It will shake at most street rpm levels. Most of you guys don't want to deal with that.

The second order vibration issue was solved in the second generation crank for the 908 engine. At the Fort Worth parade I talked with a guy who does restorations on 908s about this. He sent me the 908 firing order,but I lost that email when I left MS. (IMG:http://www.914world.com/bbs2/html/emoticons/sad.gif)


Anything longer than an 8 in a 911 style engine would make the crank too long. That would produce the torsional losses that they found in the 917 engine that prompted the center drive setup on it. Even the output drive on a 917 is taken from the center.

I figure if this could be done, then it would require a flat fan. Any ideas on it?

[alpha434]

QUOTE (alpha434 @ Feb 27 2006, 07:03 PM)

Why we couldn't use a Chevy crank: Counter balancing, and angle offsets for timing. A 60 degree V8 with a firing order 1-2-3-4-5-6-7-8 and shaped like this 1----2 3----4 5----6 7----8 The crank is at 0deg for 1. The crank is machined so that the piston one is -30 deg off center. Two is 45-30=15. Three is 60. Four is 95.

Wait. I did that wrong.

You alternate add, subtract.


But the point is that with a flat crank, we're 180deg out. Not 60

[lapuwali]

QUOTE (Cloudbuster @ Feb 27 2006, 06:52 PM)

QUOTE (Thorshammer @ Feb 27 2006, 06:42 PM) The other idea I had was to use two FZR400 Yamaha Cylinders and heads and a custom made crank using the stock bore, but reducing the stroke so that I retained 640cc. Just in case you didn't know, somebody is most of the way there Drysdale

Not most of the way, but all of the way. Ian Drysdale started with FZR400 top ends (barrels and heads) on a custom case and crank. He did this in the mid 1990s, and has been continuing development for years both of his engines and the custom chassis he builds for these engines.

The Radical engine is essentially the same idea.

The wackiest design I've seen was a "V8" made by simply gearing the output shafts of two complete ZX-9 engines together to a common output shaft (one through an idler), with the engines sitting "cheek to cheek". This made complete engine changes very easy, as long as you had a supply of used ZX-9 engines. It was very wide, but was built for a class of sportcar racing that required two side-by-side seats, anyway, so the width wasn't a problem. I believe a pair of ZX-12 engines were used by the same guy in a different car.