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v8 numpty questions
dan__wright - 16/6/09 at 11:41 AM

got a few v8 questions:

1: whats the normal firing order,

on a car its normally 1st rotation 1,3 2nd rotation 4,2

how does it fire on a v8, which order and then is it four sparks per rotation so you fire every 90 deg instead of 180?

also how are they numbered on a v8? left bank then right or left right left right etcc?

2) head / blocks

are the heads / blocks on v8s handed? ie a left and right block / head or are they just rotated 180 deg and the bottom end brings to two together and puts that water / oil paths in the right place?

craig1410 - 16/6/09 at 11:49 AM

Hi,

The Rover V8 is 18654372 firing order. The left bank is odd and the right bank even (as viewed from the driver's seat).

First rotation is 1865 and second rotation is 4372 and yes there are 4 sparks per rotation. The camshaft spins at half the RPM of the crankshaft.

I only really know about the Rover V8 engine but I believe there are other V8 designs which use what is called a flat-plane crankshaft and they have a different firing order.

I hope this helps,
Craig.

02GF74 - 16/6/09 at 12:28 PM

quote:
Originally posted by dan__wright
2) head / blocks

are the heads / blocks on v8s handed?


no.

the head gasket determines which water/oil ways are used.

the cylinders share same journal e.g. cyl 1 and 2 rods attach to same big end and the V is 90 degrees.

If you sat down, like I did, you can actually derive the firing order.

dan__wright - 16/6/09 at 12:32 PM

quote:
Originally posted by 02GF74
quote:
Originally posted by dan__wright
2) head / blocks

are the heads / blocks on v8s handed?


no.

the head gasket determines which water/oil ways are used.

the cylinders share same journal e.g. cyl 1 and 2 rods attach to same big end and the V is 90 degrees.

If you sat down, like I did, you can actually derive the firing order.


thats just what i wanted to hear,

so if you were to take two of the same straight 4, strip bottom end and turn one round you would have the starting block for a v8?

i know there is more to it than that but im just playing with ideas at the mo.

what engine was it that was twin crank? was in one of the W (12 or 16?) engines?

02GF74 - 16/6/09 at 01:01 PM

quote:
Originally posted by dan__wright

so if you were to take two of the same straight 4, strip bottom end and turn one round you would have the starting block for a v8?

i know there is more to it than that



exactly. sharing a journal sounds a bit weird as you'd think the rods would rub or some other problem but it is very successful.

means the engine can be compact due to a shorter crank.

it is how they make the v8 bike engines; there is a kawasaki z1300 V12 - bloke use specail narrow rods to use the same crank.

and there is a bit more to it than that - the firing order on the V8 has some cylinders out of sync and you'd expect the RH bank to fire follow by its shared journal LH partner (they are 90 degree apart).

As engine spins clockwise so you would expect:

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


which you mostly have if you rearrange the firing order:

21 8 65 43 7

note the piston will be at TDC but it can either on cpmpression stroke or on exhasut stroke which accounts for the above out of sequence numbers.

you need a piece of paper and pencil and some serious head scratching to wok it through.

[Edited on 16/6/09 by 02GF74]

dan__wright - 16/6/09 at 01:34 PM

im not planning a locost v8 bike engine

iank - 16/6/09 at 01:38 PM

quote:
Originally posted by dan__wright
im not planning a locost v8 bike engine


I believe the technical term for that is an oxymoron.

dan__wright - 16/6/09 at 02:03 PM

quote:
Originally posted by iank
quote:
Originally posted by dan__wright
im not planning a locost v8 bike engine


I believe the technical term for that is an oxymoron.


i was waiting for that......


lowercost than the commercial ones

02GF74 - 16/6/09 at 03:04 PM

here is v12 z1300 (but he lost 300 cc along the way!?)

<---- linky

Designing and building the V12 required plenty of thought even for Millyard, because this project was far more ambitious than the V8. The creation of the engine was similar, in that he once again retained the original cylinders as the front bank and grafted on a second set at the rear, using a shared crankshaft.

dan__wright - 16/6/09 at 03:08 PM

theres quite a few crazy engine builds people have done.

i remember seeing a mental one, i think it was 24 * single cylinder thumpers, 3 banks of 8 with the cranks linked by chain

[Edited on 16/6/09 by dan__wright]

02GF74 - 16/6/09 at 03:10 PM

quote:
Originally posted by dan__wright
quote:
Originally posted by iank
quote:
Originally posted by dan__wright
im not planning a locost v8 bike engine


I believe the technical term for that is an oxymoron.


i was waiting for that......


lowercost than the commercial ones


anything can be made given the right machinery and having the right skillg, but the clever part is knowing when to stop!!! ?

and yes, it does run, all 48 cylinders!!

dan__wright - 16/6/09 at 03:14 PM

that's the one i was posting about in my previous post, didnt think it was that many though!

Ninehigh - 16/6/09 at 06:35 PM

How did he manage to double (or more) the cylinders and LOSE cc? Surely the capacity would be increased exponentially?.

I know if I doubled my engine I'd have a 4l v8... Well at least I should have...

MikeRJ - 16/6/09 at 06:56 PM

quote:
Originally posted by 02GF74
and yes, it does run, all 48 cylinders!!


Reckon you could tell if one was missing?

Ninehigh - 16/6/09 at 07:08 PM

quote:
Originally posted by MikeRJ
quote:
Originally posted by 02GF74
and yes, it does run, all 48 cylinders!!


Reckon you could tell if one was missing?


Yeah, by the noise lol. It'd be something like:

pppppppppppp-ppppppppppp

rusty nuts - 16/6/09 at 07:43 PM

quote:
Originally posted by craig1410
Hi,

The Rover V8 is 18654372 firing order. ???

Could be wrong but I think 18436572 is the correct firing order

02GF74 - 16/6/09 at 08:07 PM

haynes RR book says:

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

mark chandler - 16/6/09 at 08:35 PM

Its definately 18436572 on rovers, infact most v8's.

If you have a scowl at the inlet manifold the firing order is usually cast on the surface somewhere.

You get the burble because do not fire equally, rllrlrrl (r = right, l = left) incidently