Firing orders

[Parksy]

Hi all

This part of multi cylinder building always leaves me scratching my head. I'm building a v4 with a 90degree v block and crank throws 180 degrees apart. If I plan to have the engine run counter clockwise when viewing from the front the firing order will be 1 4 3 2. Now the part that confuses me is the four stroke part. The crank rotates 720 degrees to complete the otto cycle, the compression stroke then the firing stroke. Does the engine fire all cylinders in the first 360 degrees then go through compression the following 360 degrees? I know this isn't the case, but I can't figure out the numbers to have it fire evenly. My understanding also is that a v4 does not have an even firing order.

If anyone could assist me with this, this would be greatly appreciated.

Thanks for reading

Andy

 

[gbritnell]

Andy,
No. 1 fires at 0º
No. 2 fires at 0º + 180º = 180º
No. 3 fires at 180º + 270º = 450º
No. 4 fires at 450º + 180º = 630º
No. 1 fires again at 630º + 90º = 720º

 

[Parksy]

Andy,
No. 1 fires at 0º
No. 2 fires at 0º + 180º = 180º
No. 3 fires at 180º + 270º = 450º
No. 4 fires at 450º + 180º = 630º
No. 1 fires again at 630º + 90º = 720º

Thank you George.

Just to clarify, when you refer to no 1, no 2 etc, does this correspond to the firing order, eg 1 is 0 degrees, 4 is 180 degrees, 3 is 450 degrees etc? If I reversed the direction the firing order would change but the degrees would remain the same?

 

[Mechanicboy]

Here is the picture of firing order of the V4 engine..

 

[Parksy]

Thanks mechanicboy. I'll be honest, but that picture confuses me. Is it showing both a v4 and a straight 4?

 

[Mechanicboy]

Thanks mechanicboy. I'll be honest, but that picture confuses me. Is it showing both a v4 and a straight 4?

Yes, both straight4 and V4

 

[Parksy]

Thank you guys. I think I have it worked out. It was a case of me confusing myself with incorrectly numbered cylinders.
If I have it labelled as followed

Then the firing order will be 1 4 2 3.
I understand that I could label the cylinders with what ever numbers I like and the firing order would change accordingly, but the physical firing of cylinders would remain the same.
Another thing that I'm confusing myself with is that I'm assuming the one bank fires, then the other side fires.
If I go by Georges figures, then it follows a horse shoe pattern around. Is this correct?

I hope my ramblings make sense.

Cheers

Andy

 

[stevehuckss396]

This is how the Peewee is laid out. Also a 90 degree block

1 - 3 - 2 - 4

 

[Parksy]

This is how the Peewee is laid out. Also a 90 degree block

1 - 3 - 2 - 4

Does the peewee rotate clockwise when viewed from the front? Assuming cyl 1 is the front. Just to confirm that I know what's going on.

 

[stevehuckss396]

Does the peewee rotate clockwise when viewed from the front? Assuming cyl 1 is the front. Just to confirm that I know what's going on.

Yes. CW from the front. Idler gear between the crank and cam so the cam also rotates CW.

 

[Mechanicboy]

The firing order is difference due the crankshaft is not same as i showed the picture with firring order 1-3-4-2 who has 4 cranktap while the model Pee Wee V4 engine has 2 cranktap.

 

[Parksy]

Thanks for clarifying that mechanicboy.

I might label my cylinders in the same fashion as the peewee v4 and use the same firing order. This seems like a more 'balanced' firing pattern as it crosses across diagonally as opposed to the U shape if it fired in a CCW direction.

Thanks all