Exhaust vs Firing Order

[Mrfuel]

Hi I am currently designin up some headers and are a little confused at the firing order vs the exhaust header

The firing order of the lexus v8 is 18436572. To get these to match and have the cyclinder pulse at equal intervals surely you would want to 1 with 6, 2 with 3, 4 and 7, 5 and 8.

This way you would get an even 45deg pulse between cycles. Most header seem to be joining just on oneside and don't have any interaction between the two banks of the enginge. How have people over come this in their system.

I have also done some calculations and come up with a header pipe length of about 0.4m for a 2" pipe. What are people recommending?

Any help would be much appreciated.

 

[madmont]

If you want you could go for something like this

2inch diameter 400mm long is a bit unrealistic for a 1UZ

 

[JBrady]

Hi I am currently designin up some headers and are a little confused at the firing order vs the exhaust header

The firing order of the lexus v8 is 18436572. To get these to match and have the cyclinder pulse at equal intervals surely you would want to 1 with 6, 2 with 3, 4 and 7, 5 and 8.

This way you would get an even 45deg pulse between cycles. Most header seem to be joining just on oneside and don't have any interaction between the two banks of the enginge. How have people over come this in their system.

I have also done some calculations and come up with a header pipe length of about 0.4m for a 2" pipe. What are people recommending?

Any help would be much appreciated.

While I applaud your enthusiasm and creativity... what is your goal?

If you are building for a street driven vehicle you will not want such large pipe. Also, the length has a few considerations. Scavenging during overlap and separation of pulses. The stock cams are very mild with virtually no effective overlap. With a full exhaust system the effect is even less apparent. Separation of pulses for 90 degree timing has been used on a few engines but notice that even racing engines do not worry about this.

I think a small tube header with pipe length more for fitment with most effort placed on transitions and an effective collector design will give you the best compromise.

Again, back to my question, what is your goal?

 

[Mrfuel]

Hi All

Thanks for the helpful reply. I am putting my motor into a cobra chassis. And a stock exhaust is not going to work so i am design one of my own. Look at the firing order i thought crossing over would give the best performance from an engineering point of view (Mechanical Engineer).

The picture look similiar to what i was think apart from i was think about putting my collectors at the side of the Motors V bank.

Basically have put bigger injectors in and i am look for some more horsepower but nothing stupid. Maybe 400hp.

Looked all over the web even in Engineering journals but could find much on tuning lengths. I was using 2" as it had small bend radius that i could use for mocking up.

How much benefit vs loss would i get from a system as pictured?

Interesting topic that i think has been over looked by most people design headers for these engine. Worth a bit of discussion.

Cheers

 

[Mrfuel]

Just wondering why you said 400mm at 2inch is unrealistic? What would you suggest 1.5" at something else?

 

[madmont]

On this forum some people have made some nice headers . J Brady gives good advice. All you have to do is have a look through the exhaust system threads

 

[Cobber]

I'm running 1 3/4" headers out to 2" (for originality's sake) then merge 4 into 1 joining into 3 1/12" and running 26" of 2 1/4" spiral louver muffler in my cobra replica. I know it's not the best performance design but it sounds awesome and suits the car. I used mild steel for the headers and stainless steel for the side pipes. I built 5 pairs but have sold them all now, I might make another batch this year if I can get motivated.

I don't think it's worth the effort in building a bundle of snakes for a couple of hp, just bolt on a blower instead

If I were to do it again I would bolt a turbo on either side.

 

[GT8 Sorpresa]

I don't think it's worth the effort in building a bundle of snakes for a couple of hp, just bolt on a blower instead

Or you could do both.

 

[markstoys]

Here's mine. The pipes are 1 3/4", and 38" long, which is longer than I wanted, but as short as would physically work. You will find that it is impossible to have short primaries if they must cross over from one side too the other.










I went this way for the sound. This motor is in a Corolla, and I wanted it to sound different. Not that I have anything against that V8 rumble--I also have a 1967 Camaro with a 327 and I love how it sounds.

When I get back home next week (I am currently working in Singapore), I will take some video so you can hear it.

Oh, and I agree with GT8 Sorpresa, mine has an M112 on it as well.

Mark

 

[Crambo]

With V12's you can make 180deg pairs on each bank.



Have a look on V-eight.com there's lot's of exhaust tech.

 

[GT8 Sorpresa]

All beautiful work, It,s geat to see some one go the extra mile (we all know how long that mile is too) to make a system like that. I love the sound of a 90 degree exhaust system on a V8, the V12 is just to easy to do (just jealous) I did my best to do a 90 degree system on my twin turbo V8 1uz-fe, but it was just to much pipe.
Credit to you Mark