×
INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS

Log In

Come Join Us!

Are you an
Engineering professional?
Join Eng-Tips Forums!
  • Talk With Other Members
  • Be Notified Of Responses
    To Your Posts
  • Keyword Search
  • One-Click Access To Your
    Favorite Forums
  • Automated Signatures
    On Your Posts
  • Best Of All, It's Free!
  • Students Click Here

*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

Students Click Here

Jobs

4 Cylinder Header Design

4 Cylinder Header Design

4 Cylinder Header Design

(OP)
Currently this engine uses a 4-2-1 Setup with a crossover a few inches away from the exhaust port(on the header primaries), only on cylinders 2 and 3(which is well before the first collector)

This Engines Firing Order is 1-2-4-3


The Crossover linking Cylinders 2 and 3 confuses me since they are not paired. Since Cyl 2 Fires then next to fire is Cyl 4, so there isn't any scavenging from these two (Cyl 2 and Cyl 3). I believe this is done to alter the sound of the exhaust, is my assumption correct?


I have an idea to create a dual exhaust system which

(Cyl 1 and Cyl 2)
and
(Cyl 4 and Cyl 3)

Are paired

So the exhaust is a Dual 2-1 system. But, now two cylinders will not receive scavenging (Cyl 1 and Cyl 4)

To Remedy this I propose to put crossover pipes on the header primaries between

(Cyl 4 and Cyl 2)
and
(Cyl 1 and Cyl 3)

So now all cylinders can receive scavenging.



What are your opinions on the system? Is there any literature on crossover pipes in headers?

RE: 4 Cylinder Header Design

Not enough information. Is it a 2 stroke or 4 stroke? What is the crank configuration? What problem are you trying to solve?

"Schiefgehen will, was schiefgehen kann" - das Murphygesetz

RE: 4 Cylinder Header Design

(OP)
Sorry, it's a 4-Stroke 4 Cylinder engine. Each cylinder is 180 degrees apart using a Flat Plane Crank.

The Problem- Instead of running a traditional 4 to 1 setup, I propose to run a dual 2 to 1 system that can produce similar performance when compared to a 4 to 1 setup. So the ultimate question is how do crossovers by the headers function, and if there is a book that talks about them I can read so I can optimize them. The two Engine books I have do not speak about them. Also I would like to hear some opinions about this.

RE: 4 Cylinder Header Design

(OP)
That would be unsequential pairing, I believe sequential paring gives the most power, am I wrong? Can you explain?

RE: 4 Cylinder Header Design

1 with 4 and 2 with 3 is sequential. The sequence is every alternate cylinder by firing order.

The reason is that the exhaust gas pulse then has equal separation, ie 360 deg between each cylinder. Closer is better, but then you get uneven with a bit to close then a lot to far apart ie 180 then 540 then 180.

In my experience 3 into 1 works really good, but 4 into 1 also works fine.

Pipe layout is but one aspect of this.

Regards
Pat
See FAQ731-376: Eng-Tips.com Forum Policies for tips on use of eng-tips by professional engineers &
http://eng-tips.com/market.cfm
for site rules

RE: 4 Cylinder Header Design

(OP)
Hmmm, I must of gotten confused with all what I was reading, and would appear you are correct. Also now I can picture a 4 stroke engine properly, When Cyl 1 is in power stroke, Cyl 2 will be in power stroke when Cyl 1 Opens its Exhaust valve. So there is no scavenging until 540deg with my current idea. If we do it every 360deg then each cylinder will get the same size pulse.

So could you give your opinion and Help me better understand the Stock Engine's 4-2-1?

It pairs 1 and 2, and 3 and 4 with a crossover on 2 and 3 so these two receives 360 deg Scavenging, the other two receive 540 scavenging from its primaries and then all cylinders receive a weaker scavenging effect from the final collector. . . But The same engine just greater displacement gets rid of the crossover, otherwise it's the same setup. I cannot see why they would give the greater displacement engine less scavenging?

Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

Red Flag Submitted

Thank you for helping keep Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.

Reply To This Thread

Posting in the Eng-Tips forums is a member-only feature.

Click Here to join Eng-Tips and talk with other members!


Resources