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#1 Jhope

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Posted 20 November 2000 - 19:32

with all the talk of Renault using an engine that has a V-angle of 111 degrees, I want you all to know that the Honda RA302 of 1968 used a V-8 that was angles at 120 degrees. it was 88 X 61.4cm and was rated at 395bhp at roughly 9000 rpm.

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#2 Ali_G

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Posted 21 November 2000 - 14:12

JHope: As mentioned by my post on V Angles it all depends on how many cylenders the engine has. Natural V angle is depended on how many cycenders you have. In the case of a V10 there are 5 cylenders on each side. So that gives an angle of 72 degrees. ie. 360/5 = 72 degrees.

So with a V8 it is easier to widen the angle as its natural angle would be 90 degrees.

Niall

#3 david_martin

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Posted 21 November 2000 - 14:41

Originally posted by Ali_G
JHope: As mentioned by my post on V Angles it all depends on how many cylenders the engine has. Natural V angle is depended on how many cycenders you have. In the case of a V10 there are 5 cylenders on each side. So that gives an angle of 72 degrees. ie. 360/5 = 72 degrees.

So with a V8 it is easier to widen the angle as its natural angle would be 90 degrees.

Niall


Nice theory - not sure I agree. The "natural angle" as you call it is 72 degrees for a V10, but it is a ignition cycle consideration:

10 cylinders x 72 degrees = 720 degrees = two crankshaft rotations = 1 complete cycle of a 4 stroke engine.

This symmetry make life rather easy from a firing interval perspective.

For a V8:

8 cylinders x 90 degrees = 720 degrees = two crankshaft rotations = 1 complete cycle of a 4 stroke engine.

Ditto.

The only production vehicle I can think of with a V10 is the Dodge Viper - it has a 90 degree 8.0 litre V10. It uses an assymetrical 90/54 degree alternate firing interval which works just fine. With computer controlled fuel injection and ignition systems this kind of firing cycle is relatively straightforward to implement.

Changing the V-angle of an 8 or 10 cylinder engine presents exactly the same ignition control issues. To suggest that it is easier to widen the V angle of a V8 compared with a V10 is utter nonsense.

#4 DangerMouse

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Posted 21 November 2000 - 15:10

David_martin, spot on, in the old days when you may have had to calculate and do the cam grinding by hand as well as the ignition timing etc etc symmetrical firing orders and straight forward V-Angles were the order of the day (scuse the pun!) for simplicities sake.

Now in the computer age expect all sorts of wacky firing orders and V-angles all the data can be shoved into a computer and the cams will be ground without human intervention (expect camshafts to be gone from F1 within 5 years) crankshaft balance can be ground into intrinsically out of balance V angles though clever computer programmes, ignition timing will also be worked out on the fly.


#5 AndersF1

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Posted 21 November 2000 - 16:42

What about 144 degrees V10:s? Then you should still be able to have a symmetric 72 degree ignition cycle, i.e. 72 degrees rotation of the crankshaft between each ignition.

#6 desmo

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Posted 21 November 2000 - 19:51

Ford makes an SI V-10 truck engine that is, I think, an even firing unit.

I don't think it is important for a racing engine to have an even firing order anymore. As DM points out, with modern manufacturing techniques the designers have pretty much a free hand now.

#7 marion5drsn

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Posted 22 November 2000 - 18:31

Jhope; You failed to mention the crankshaft as to whether it was a 90 or 180-degree pattern. This makes it impossible to figure out just what is the firing pattern and order. Any engine that has an opposed engine or one of 120-degree bank angle is difficult to place in a car. This due to the width of the engine. One of the primary reasons for the V-8 engine being so universal is the shape which is almost a cube and for exterior volume versus cubic piston displacement it is the smallest ratio one can find.
Try to visualize a V-12 427 cubic inch (7L) in a Pontiac, Dodge or Ford in the 1960s or 70s and you will see what I mean.
Also no one has mentioned the Millions of V-6s made at 60 or 90 degrees and the method they used to keep them operating smoothly. I suspect there are several extra crank arms or offset pins to achieve this. The old Odd fire G.M., Ford and Chryslers with Odd fire cranks where certainly noticeably rough. And it may have affected the life of the engine.
NASCAR mechanics did notice a difference in the life of racing engine between the V-6s and the V-8s and then they all went to V-8s as being cheaper to run over a period of time. Whether this was due to the offset crankshaft pins I don’t know.
One thing we should try to ascertain is the engine that used these Odd Bank/Firing angles and just how successful they were. Did anyone copy them and if so, for how long.
One of the Ferraris had a Vee 6 bank angle of 120 degrees from 1981 to 1987 then changed to 90 degrees in 1987-88 the next year the F-1 went to non-supercharged engines. And Ferrari went to a V-12. That’s enough to make one pause and ponder! What year were they right? If at all! M. L. Anderson



#8 Paolo

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Posted 01 December 2000 - 00:42

A question :
everybody speaks about the advantages on the center of gravity due to the widening of the V angle. Now, I would like to calculate this advantage. The problem is : what is (more or less) the relative weight of block and heads ?
Anyone has got data ?

#9 PDA

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Posted 01 December 2000 - 01:29

There is also the problem of where to put the exhausts as the angle approaches 180. No doubt there will be other problems of air flow past the engine. If one balances the other, then it is OK. Presumable Renault have done their homework and the plusses outweigh the minuses.

#10 desmo

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Posted 01 December 2000 - 07:37

Just doodling with pencil and paper leads me to two conclusions about v-angle:

First any angle greater than ~150 degrees will have the exhaust headers needing some nasty kinks to clear the undertray.

Secondly, any angle greater than ~120 degrees makes a single central airbox look pretty dicey. Huge packaging ramifications there.

#11 Mellon

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Posted 01 December 2000 - 08:40

Wouldn't it be possible to put the exhausts above the engine when the angle is very large (>150?) ??

#12 marion5drsn

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Posted 01 December 2000 - 19:01

Many exhaust systems have been made with exhausts on the inside of the Vee. This being true of Vee-8s of L-head designs as the old Cadillac’s. Some Ferraris, BRMs and so forth. These using DOHCs with the intakes in the same area as the exhaust pipes.
Some of the most interesting are the pictures in the book Philip H. Smith Scientific design of Exhausts and Intakes opposite page 127 these all being of the Ford V-8 of the 1960s.
The real problem is not the exhaust but the positioning of the intake passages after you put the exhausts in the center of the Vee, the intakes are low down to the ground and since this is truly dirty air you must by necessity filter the incoming air. This being especially true if you put the intakes on the outside of the lower camshaft.
One of the most intriguing is the picture of an old BRM with center exhausts but the pipes are of an exhaust typical of a 180 degree crankshaft. A highly unusual exhaust manifold. (BRM P261)
There doesn’t seem to be any reason to put the exhausts on the inside of the Vee on the V-10s at 72 degrees as the Vee doesn’t have enough room to provide the space necessary to provide the curved pipes for proper flow.
Any bank-included angle of less than 90 degree seems to be not useful as the pipe diameter is of such proportions as to exclude the area necessary to flow the gases in an efficient manner. One must remember that there are five of these big pipes on each side.
Just visualize the air intake on a 144-degree Vee and just how low to the ground they would need to be if the necessary piping were provided. The same problem as Desmo states on the exhaust pipes.
As with many things the best engineering is the best compromise with the circumstances involved. M. L. Anderson
[p][Edited by marion5drsn on 12-01-2000]

#13 Amadeus

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Posted 01 December 2000 - 19:31

Ok, engines are not my strong point, but Subaru make a big virtue of thier horizontaly opposed turbo 4-cylinder (multiple WRC winner), which I presume is what we are refering to by a 180 degree angle. Surely extending that to a V8 (or even V10) would be pretty simple? Would it also have advantages in centre of gravity, since it would be lower? And firing order should be pretty simple to work out? Apologies if all this is way off the mark (electronics are simple - the rest I leave to people with dirty fingernails!)



#14 desmo

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Posted 01 December 2000 - 19:52

One of the big problems of using a horizontally-opposed layout in F1 is the clutch diameters are now so miniscule-and thus the crankshaft so close to the ground- that there is nowhere to put the exhaust plumbing for a boxer. As well, this puts obstructions into the critical undercar aerodynamics. For these reasons alone, I cannot see any boxer F1 engines appearing in the future.

#15 westendorf

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Posted 03 December 2000 - 03:39

I do believe that the Ferrari "flat" 12 of the 1970's were actually referred to as 180degree vee engines. They were not boxers. They fired as vee engines. [p][Edited by westendorf on 12-03-2000]

#16 Paolo

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Posted 03 December 2000 - 12:12

To Westendorf,and other engine people : what's the difference in firing order beetween a boxer and a 180° engine ? If there is any difference, which of the two firing orders allows the absence of second order vibrational moments, for which flat engines are famous ?
And why should one renounce that advantage and use the other firing order instead ?

#17 Tracy

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Posted 04 December 2000 - 02:27

I seem to recall that Mercedes built a monoblock 180 degree V12 engine for its LeMans/Sportscar effort in the mid 90 ies. As far as I can remember the exhausts exited from the top of the Cylinder head between the Cylinders. This gave a a completely flat engine with a low C of G. whilst this design sounds hidiously complex, it could be the ideal solution for modern narrow f1 cars where engine length is not really an issue and low C of G is of paramount importance. I seem to remember when the engine/Chassis package was optimised the car was neigh on unbeatable.

Whilst I'm here does anybody have any more info on the new Renault F1 engine?

#18 david_martin

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Posted 04 December 2000 - 06:18

The Mercedes engine I think you are talking about was the M291 that was used in the Sauber/Mercedes C291 group C racer that ran in 1991. That engine was a 3800(ish) cc 180 degree 12 cylinder, and did, indeed, have the exhaust take off points on the top side of the head.

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#19 Marco94

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Posted 04 December 2000 - 09:03

Paolo,

With a 180 degree V-engine, two opposing pistons are connected to the same crank. When one piston moves to the right, the opposing one will do so as well. A boxer on the other hand has a seperate crank for each piston. In this case when one piston move right, the other one move left and vice versa.

david_martin, the M291 can't have been more 3500 cm^3 according to the rules. I do have a great see-through in the German "Auto, Motor und Sport" magazine. I'll see if I can find it soon. No promises though.

Marco.

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#20 david_martin

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Posted 04 December 2000 - 10:18

Sorry everyone, that should have said 3500 cc (should not try and post before breakfast :) ). As Marco rightly points out, 1991 was the first year of the 3500cc atmo formula (ie. formula 1 engines) which basically killed off Group C as we knew it in the 1980's. Kudos to Bernie Ecclestone for that.

#21 andy_bee

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Posted 04 December 2000 - 10:54

Subaru used (I say used as I believe it was a Moterni Moderni engine) a Boxer engine in 1990 with the Coloni team and Mr Teargas himself, Bertrand Gachot.

It failed to prequalify on each occasion!!!

does anyone know how many cylinders it had etc. BTW, the air for the engine was taken in by the little extensions on the sidepod.

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#22 david_martin

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Posted 04 December 2000 - 11:13

The Motori Moderni was a 180 degree V12. Apart from Japanese money helping to pay the bills and having a Subaru name somewhere on it, the engine was an all Italian affair. It was designed by Carlo Chiti, of Alfa-Romeo fame, and was really an update of the flat 12 concept that Brabham ran during the mid-late seventies, which in itself was inspired by the famous and highly successful Ferrari flat 12 of the same era. Coloni gave up after 8 failed pre-qualifying attempts and ran customer DFR V8's. Did not help much....

#23 Tracy

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Posted 04 December 2000 - 22:06

I'm still non the wiser. Can anybody explain why engine manufactures arn't adopting a similar approach to the MB sportscar engine? There must be some limitations as, as far as I know, the current MB/IIlmor is only a 72 Degree V. I would have thought a modern 180 degree 10 cylinder would be enormously beneficial in terms of Aero efficieny and Low C Of G. Not sure if you could get it to run at 17000 rpm without shaking the car to bits - careful grinding of crank required me thinks.

#24 david_martin

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Posted 04 December 2000 - 22:29

That MB flat 12 was no light weight - nearly 180kg, and they had quite a few engine failures because of oil scavanging from the heads because of the exhaust arrangement IIRC.

The big killer in an F1 car is the width of the engine and the problems with ducting to get air to it. The width means big compromises around the rear of the car which will definitely effect the efficiency of the diffuser and rear wing. The current roll over protection rules mean that it is mandatory to have a rather massive and rigid structure behind the drivers head. Whether you choose to take air through it to the engine is your choice, but the drag penalty in using a scheme like the Coloni chassis is not insignificant. With a flat 10 the latter idea is probably just about the only way to get air into the engine. While the introduction of periscope exhausts might make the situation a little easier, the possible exhaust position is also not great for a single seater. The bottom located exhaust would foul the floor and the top located exhaust would not make the overall height much less than a modern 72 degree layout. So while the engine offers potential COG benefits, the package is not nearly as attractive as it was when Ferrari went that way with a transverse gearbox in the early 70's - or in a sports prototype, hence MB choice for Group C racing.

#25 marion5drsn

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Posted 04 December 2000 - 22:42

Marcos. I have been working on the firing order of a 12 cylinder for about two days now and find that the ordinary 180-degree flat engine and the ordinary 60-degree engine fire the same. Will you please give me the firing order and the crankshaft layout of a so-called “boxer” engine? At this point I don’t believe it has ever existed!
My sketches show that it would require a thirteen main bearing layout and so many extra crank arms as to be virtually fruitless. Can you give me a definite engine made by a reliable manufacturer that worked! I can say for a certainty that I know of none that exist or ever existed.
Please do nor count the ones that are figments of someone’s imagination. Especially those of Road and Track magazine.
I think that what we need here is a very definite description of a “Boxer” engine. I for one know of none! I wonder if it isn’t a misinterpretation of a German Word? And this by someone who knows “Foreign” words no better than I. Yours, In a state of perplexity, M. L. Anderson


#26 desmo

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Posted 05 December 2000 - 05:34

As far as I know, in English the terms boxer and horizontally-opposed or flat are all synonymous. All the common "flat" engines I am familiar with- VW, Porsche, Subaru, Alfa etc. all have a seperate crank throw for each cylinder, one more main bearing than the total no. of cylinders and the throws at 180 degree intervals. Anyone know of some counter-examples?

#27 Paolo

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Posted 05 December 2000 - 14:51

About the Ferrari flat 12 of the 70ies :
Where were the exhaust plumbings locted, on the top or on the bottom ? Any pictures of that wonderful engine ?


#28 marion5drsn

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Posted 05 December 2000 - 22:09

Paolo; The engine you may be refering to is the 1970 312B Flat 12 180 degree three liter. This engine had the intakes on the top side but if you looked at it from the outside of the car it looked as if the they may of been on the inside of the vee of the camshafts. This on the F-1 engines. In 1980 they went to the turbo V-6. If you have the book Ferrari Monoposto you will see this beautiful engine on pages 126 to 155.
There is another set of engines on the road cars of which I have not enough information to give a definite answer.The 512 TR had the injectors on the top and the exhausts on the underneath side.
I'm sure there are some cars that had the exhausts in the top Vee and the intakes in the valley between the camshafts, but which ones I havn't any pictures or information.
The only place that exhausts on the top would make any sense is if they put the intakes in the middle of the camshaft Vee. The intake on the bottom of the cylinder head would make a very diry air pickup and/or a lot of air passage plumbing. However it would make a very low center of mass for the engine. But one must also remember the clutch diameter.
M.L. Anderson

#29 desmo

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Posted 06 December 2000 - 01:27

Here's a pic of the 312 Boxer motor in a sports car:

Posted Image

Not the greatest picture, but you can see the intake trumpets above the level of the head. At the time the clutch diameters were sufficiently large to allow routing the exhausts from the bottom of the head in flat engines.

Routing the intake ports between the cams became impractical after the narrow included valve angle became standard after it's overwhelming success in the Cosworth DFV.

#30 DangerMouse

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Posted 06 December 2000 - 18:38

I suspect that wide V-Angle and flat engines sacrifice weight as the crankcases have to be built strong enough to support weight in two distinct areas, narrow V angles have the banks as good as attached to each other, I’m surprised we haven’t seen a design like the VW VR series of engines, the ultra narrow angle meaning that a fairly light block can be built for the given engine configuration – COGs probably the killer there!

And why don’t they stagger the cylinder bores (imaging two honey comb bacnks of 5 cylibders).....

O-O-O
-O-O-

-O-O-
O-O-O

The shape of the casting (less straight areas) would substantially strengthen the block (meaning it could be made much lighter) as well as shortening the engine close to that of a V8.

Loosing the camshafts would make this formation much easier to achieve.

#31 Ray Bell

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Posted 07 December 2000 - 00:02

This idea has definite possibilities, Dangermouse, and even before camshafts are lost to us, I would think. Clever design could see the inlet cam on the outer cyliners become the exhaust on the inner ones, and perhaps a fifth cam to operate the inlets on the inner cylinders! Separate heads may be required...

#32 Alvega

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Posted 07 December 2000 - 12:04

Desmo,

As far as I know Ferrari choosed a "flat" 12 configurantion becaused it allowed designing a simpler and stonger cranckshaft, with only four main bearings an one throw for each pair of opposing cilinders.

The road version of this engine, as used in the 512BB and the Testarrossa, was also a "flat", although it is usually referred incorrectly as being a "boxer".



#33 Alvega

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Posted 07 December 2000 - 12:18

AndersF1,

I remeber that around 1980, when Audi was introducing 5 cilinder engines in their's saloons, Mr. Ferdinand Piech, who was then in charge of Audi, defended that the best design for a 3000 cc F1 engine was indeed a 144 deg. V10.

#34 Ali_G

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Posted 07 December 2000 - 14:32

Alvega: Now that you have brought up about Audi's 5 cyclender engine one thought springs to mind. A 11 cylender engine has not been banned yet by the FIA.

Would it be possible to have a set up with 6 cylenders on one side and 5 on the other with a udd cylender on the side with the 5 to keep the engine well balanced.

I know it would be a lot easier to do if the engines were in line ala the Alfa Romeo 156 which I think has an in line 5 cylender engine. Any thoughts.

Niall

#35 david_martin

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Posted 07 December 2000 - 14:49

From the FIA technical regulations:

5.1.4) All engines must have 10 cylinders and the normal section of each cylinder must be circular.

seems pretty clear to me.

That Alfa engine is a diesel BTW. There are a few 5 cylinder Otto cycle engines about - Volvo use some in the S60 and V70, and Fiat used one in the recently discontinued Coupe. And as DangerMouse points out there is the Volkswagen VR5, which a very narrow angle V5 designed to reduce the engine width for transverse mounting in narrow FWD engine bays. Apparently GM was playing around with a prototype VR5 engine in the late 80's but could not solve the problems associated with the layout and gave up.




#36 Ali_G

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Posted 07 December 2000 - 19:50

Sorry. I thought the rule was that V12 were banned but anything else was allowable.

Niall

#37 marion5drsn

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Posted 08 December 2000 - 22:11

AndersF1: Finally got around to 144-degree bank angle problem after some difficulty with a somewhat “sure” way to see if it would be a possibility to achieve an Even and not an Odd firing pattern. After making a paper wheel and a V-angle of 144 degrees. The firing order is #1-8-9-2-3-10-5-4-7-6 where as the 72 degree angle is #1-10-9-4-3-6-5-8-7-2.
Whether the engine is now prone to Primary and Secondary Shake is unknown by me? Altho the pistons left to right do arrive at the top at the same time. This seeming to be a prerequisite for disallowing this troublesome feature. Whether or not the crankshaft would be troubled by Torsional problems is also unknown to me! It’s too bad that some engineering book doesn’t get into this whole engine question and “solve” it. This engine has a five plane crankshaft!
I’ve also purchased a book on the V-8 engine of 75 degree bank angle used in the TVR and there isn’t enough information on it’s design to make any observation on it’s claim to being a great design and freedom from the V-8-180-degree crankshaft disease. Yours, M. L. Anderson[p][Edited by marion5drsn on 12-12-2000]

#38 DangerMouse

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Posted 12 December 2000 - 18:10

All these V angle calculations I assume are based on the theory that the crank throws are on the same plane. With today's techniques I don't think this is necessary anymore! I wouldn't be surprised if the Illmor already has a weird crank configuration meaning a remarkable (namely big bang) firing order - hence the strange sound of the engine.

#39 Halfwitt

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Posted 12 December 2000 - 18:14

That picture of the crank posted the other day on the Steel Crankshafts thread didn't look like the cranks were on the same plane. They looked to be all over the place.

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#40 Mellon

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Posted 12 December 2000 - 21:08

DangerMouse: Wouldn't a big bang engine sound as if it was running lower RPM. I thought the sound of the McL had a higher pitch than other F1 engines.

#41 Paolo

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Posted 12 December 2000 - 22:21

Excuse an engine profane,
but would someone please explain to a poor aerodynamicist why big bang engines require throws not to be on the same plane ?
And, about throws : it's a technical English word I never met before.
I assume it is the "out of rotation axis" part of the crankshaft, I.E. the one where the piston rod is connected. Is that right ?

#42 marion5drsn

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Posted 12 December 2000 - 22:58

Paolo; the word throw refers to the "bend" in the crankshaft. A 10 Cylinder engine has 5 throws with two connecting rods on each throw. The same hold true of a "
flat" 10 cylinder.That is if one exists. 12 cylinder engines have 6 "throws" each having 2 connecting rods per "throw. All "true" Vee engines have two connecting rods per throw. All Vee engines made with the standard bank angle as 72 degees for a ten cylinder do not have any offset in the outside diameter of the connecting rod bearing. I hope this does not confuse you more. M. L. Anderson

#43 Paolo

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Posted 13 December 2000 - 15:18

Everything clar, Marion,
except for the "offset" part. One of the reasons I follow this forum is to learn on topics I don't know.
Thanks.

#44 marion5drsn

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Posted 13 December 2000 - 18:44

Paolo; The term “offset” refers to the cylindrical portion of the bearing having two distinct diameters as opposed to only one long diameter. One must always remember any Vee type engine made with the “Natural” bank angle has one outside diameter twice the width of one connecting rod. But one with an offset has two different diameters on different axis. The best example I know of in the U.S.A. was made at the time of the big switch from V-8s to V-6s sometime in the late seventies or early eighties. This was done to prevent the 90-degree bank angle from interfering in the “Even Firing” of the engine every 120 degrees. The original V-6s had an “Odd fire Pattern”. Or # 1 @ 0 degrees # 6 @ 150 degrees
# 5 @ 240 degrees
# 4 @ 390 degrees
# 3 @ 480 degrees
# 2 @ 630 degrees
Odd Fire above.

# 1 @ 0 degrees
# 6 @ 120 degrees
# 5 @ 240 degrees
# 4 @ 360 degrees
# 3 @ 480 degrees
# 2 @ 600 degrees
Even Fire above.

As you may be able to ascertain the crank pins must be Offset or extra crankarms used to achieve the Even Fire pattern as the firing order is the same and the bank angle is 30 degrees off of the “Natural” firing order. Also you know the manufacturers are not going to go to any more trouble and expense to build Even Fire engines at any time. I don’t believe that either the Odd or the Even Fire engines caused any problems. Except the Odd Fire were somewhat rough in low speed situations. M. L. Anderson


#45 Jonathan

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Posted 13 December 2000 - 20:07

Originally posted by Amadeus
Ok, engines are not my strong point, but Subaru make a big virtue of their horizontaly opposed turbo 4-cylinder (multiple WRC winner), which I presume is what we are refering to by a 180 degree angle. Surely extending that to a V8 (or even V10) would be pretty simple? Would it also have advantages in centre of gravity, since it would be lower? And firing order should be pretty simple to work out? Apologies if all this is way off the mark (electronics are simple - the rest I leave to people with dirty fingernails!)


The Subaru production engine uses a wet-sump lubrication system, so in essance the configuration of this motor is something like a "T" when viewed head on. The cylinders are actually a good 4-5 inches (10-12 cm ?) above the low-point (cranckcase sump) of the engine. F1 cars typically rely on a dry sump lubrication system, that allows the engine to sit far lower than a production engine. While the Subaru has many advantages over a typical inline production engine, its centre of gravity is actually much higher than a typical F1 "boxer" or "Vee" engine configuration.

#46 Ray Bell

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Posted 13 December 2000 - 21:53

A good and popular example of the offset crankpins is the Peugeot/Renault/Volvo V6. It still has an uneven firing pattern, however, but is nice and smooth. It's a 90 degree Vee.
I'm stuck on the term you use there, too, Marion, the "offset diameter of the connecting rod bearing."
But I fear that your explanation will be difficult... sorry.

#47 AndersF1

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Posted 14 December 2000 - 14:56

Isn't a "Big bang" engine an engine where all the cylinders ignition happens at the same time, every second rotation? (I don't know of any 4-stroke Big bang engines, but I think some of the MotoGP-engines work in this way, except that the ignition happens every rotation as they are 2-stroke engines.) If so, is it really possible with a Big bang V-engine?

I thought the 72-degree(and 144-degree) V10s had 5 crank pins, with 72 degrees between each of them, so you have 2 pistons (one in each bank) in the upper position each time you rotate the crankshaft 72 degrees. Is this correct, or should I stick to aerodynamics? :)

Marion: I guess your description of the number of crank pins relates to V-engines, because I've seen straight 4/6s that have separate crank pins/throws for each piston.

#48 marion5drsn

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Posted 14 December 2000 - 18:20

Offset connecting rod diameters; possibly the easiest way to mentally “see” an offset diameter is to draw a cylinder and then divide it in half. Making sure you have drawn a centerline thru it. After dividing it in half, move one of the two halves straight upwards (Or downwards).
Only move it about 1/3 of the diameter. You now have an offset crankpin! Most crankpins are not moved this much. The ones in the Chevrolets were moved about .901” (22.885mm) or 30 degrees. Just how many tens of millions of V-6s that have been manufactured since the changeover I don’t know. G.M., Ford and Chrysler all used this method to the best of my knowledge.
My Toyota V-6 is a sixty-degree and this has a changed firing order, firing pattern turned 180-degrees and apparently no offset crankpin outside diameters. Whether it has six counterweights I don’t know, but I shan’t take it apart to find out. Most cars these days don’t get taken apart enough for the mechanics to know whether or not the cranks have counterweights or not. I do know that G.M. V-6 cranks only have 4 counterweights. Yours, M. L. Anderson


#49 Ray Bell

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Posted 14 December 2000 - 21:26

It will please you to know that I get into mine enough to know what's in there, and I keep some bits and pieces lying around, too.
I guess my consternation with your description was in the terminology. I see 'diameter' as an abstract sort of thing, a dimension, not a component. Maybe others do as well.
So perhaps we should take the time here to invent some more descriptive terminology so these offset crankpins have a proper name that readily describes them.
'Offset crankpin' isn't necessarily it, as it could be a single pin offset to the front or rear of the engine (there are engines with these, I seem to recall... dodgy stuff!).
What about 'split crankpin,' as it really is split in appearance?
There's not much difference in the sections of the crankpins of the V6 Peugeot, either, maybe a little more than the GM version you quote.
Plenty of them around to look at, the die-cast alloy blocks have a penchant for allowing galvanic action to take a premature toll on them where inhibitors aren't kept up to scratch in the coolant.
Other than that, a very nice engine from most points of view. Shame they were asked to tug around such a heavy car.

#50 marion5drsn

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Posted 24 January 2001 - 19:19

Boxer engine.
BMW twin cylinder motorcycle engine is a “true” boxer as the two adjacent pistons are going in the opposite directions at the same time. Old VW flat four was similar. As is the Subaru, Corvair and Porsches.
As the number of cylinders increases the problem of engine length increasing due to the extra crank arms needed to achieve the boxer effect becomes increasingly important. A flat eight has the same problems (Primary Moment) as a 90-degree V-8 in that the crank is antisymetrical longitudinally and needs eight counterweights to balance the crankshaft at higher speeds. Ferrari has made so many different configurations of engines that I wonder how they missed this one!
Marion L. Anderson
[p][Edited by marion5drsn on 01-25-2001]