Exhaust Headers

[humding]

Does anybody have experience of designing & building decent exhaust headers. Is a 4 into 1 or a 4 into 2 into 1 better. If the latter which ports should be matched together in pairs.What sizes would you reccommend.

[DmaxMaverick]

There are headers available. If you have a turbo now, or in the future for the engine in question, don't bother. The headers won't offer much appreciable gain with a turbo, as exhaust scavenging does not occur with a pressurized exhaust system. The effects on an N/A engine will be very similar as with a gas engine. The headers have to be mapped differently, due to timing and valve overlap differences.

I suggest you either wait for a reply here, or post a thread in Dr. Lee's forum. He'll be much more informative.

[Craig M]

Stray Cat is going to do some dyno testing on stock manifolds vs custom equal length headers. Will get some real number to look at rather than speculation.

[humding]

Thanks Lads. Its a 6.2 NA in a Land Rover so standard items don't fit. I have 4 into 2 into 1 at the moment but having measured the pipes I find that where ever two pipes join into one the cross sectional area decreases. Surely this does not help. The current engine has three cracked mains so I am waiting on a custom engine to come from The Diesel Depot.
I also imagine I need to join the correct ports not just the front two and the back two as they are at the moment, so that I get the best gas flow.

[humding]

I have been checking up again and what I am looking at is joining the primary pipes from the following:
Cylinders 1 & 5
Cylinders 3 & 7
Cylinders 6 & 8
Cylinders 2 & 4

This would mean the RH header would have the front two ports joined and the two rear ports joined. The LH header would be more awkward as the first & third ports would be joined and the second and fourth ports would be joined. Does anybody know if this is correct or if I am off on the wrong track

[grape]

not sure a 4 into 2 into 1 is what a diesel needs. We use them in a wide rpm range like a motorcycle or our race engines that turn 5600 off the corner to 9600 at the end of the straight. The tri-y acts like a long length primary in lower rpm ranges then switches to only seeing the shorter length before the first merge when the pulses get closer together. You can actually see when this happens on the engine dyno, because with a carburetor velocity gets extrememly unstable and it is hard to hold in one place rpm wise. Not sure it's needed on an engine that idles at 600 and turns to a max of 3600.

and you want to join cylinders that fire farthest apart from one another in crank degrees, I dont' know what the firing order is.......but if they are 180 from one another it's a plus.

[Stray Cat]

I hope to have the engine running on the dyno this weekend. I will begin with it N/A with stock manifolds. The first thing I plan to change is the stock Manifolds to headers (4 long-pipe). So, I hope to have some measured results soon. As to long pipe vs. Tri-Y headers, my understanding is that both are better than stock manifolds; between each other, long pipes are better for open throttle horsepower (racing), Tri-Y's are better for low-end torque and mileage (normal driving).

[humding]

Thanks lads again. From the bits of infoI have got from other sites the tri-y is better for normal driving/low end torque. With regards to matching the primaries I was aiming to even out the pulses so that I would get bang-gap-bang-gap rather than bang-bang-long gap. Its not going to work out 100% as there are two bangs together on one bank but I think it will be as close as can be got. FYI firing order is 1-8-7-2-6-5-4-3. I look forward to the Dyno results as I still have 3-4 weeks until I get my customised 6.2 shipped in from the diesel depot.

[Stray Cat]

The header test results are in! Look at "6.2TD engine experiment", under "6.2 forum", for results!