MD,
There is little information avaiable on anti-reversion chambers at first glance. if you want to dig reallly deep I'm sure you can come up with more than I have.

REVERSIoN is the secondary pressure wave that travels back up the primary pipes and enters into the cylinder on valve overlap. As this pressure wave travels back up the pipe, it brings with it all the residual gases still left in the pipe. This is what contaminates the fresh intake charge. Enter in stepped headers and ANTI-REVERSIoN chambers, placed at strategic locations in the primary pipes. These methods are employed to tune the arrival of the exhaust wave and to diminish the effects of the high pressure in the pipes. The results are higher volumetric efficiency and more power.

I think the secret location they are placed is based on the resonant length (target torque peak) Remember the speed of sound varies as a function of the air temperature.


one of the things I dug up was a motorcycle trick they use to prevent reversion in Harley drag pipes

AR POWER CoNES and White Brothers TORK VALVES are a few of the names associated with the product

Torque Cone: A conical device slipped inside an exhaust pipe near the flange that reduces the initial inside diameter of the pipe to create backpressure.

Basically the anti-reversion step is right after the port in the head. is that the best idea? well only the dyno can tell you for sure, but my guess that it's not.

My idea is along the lines of the stepped header/anti reversion chamber. use tow lengths of pipe, bevel the end of one, and flare the end of the other like a slip-on pipe so it's ID is the same as the other's OD.

1- normal primary ID
2- step to larger ID (reflect negative wave back up)
3- taper down and accelerate
4- back to primary ID

for the anti-reversion properties you can see the 2 to 1 change in diameter, and the beveled end may have an effect there.

Or maybe not.


comptech 4-2-1 stepped

Hytec header with anti-reversion chambers

 

In the pictures, the Hytec header is pairing 1/2 and 3/4, but the Comptech header pairs 1/4 and 2/3. Does that have anything to do with whether it is a 4-1 header or a 4-2-1 header?

 

No,
4-1 means all four primaries merge into one collector, while the 4-2-1- means four primaries merge into two Y pipes, then those two secondaries merge into a third Y

 

4-14-2-1

. IIIIIIII
.W YY
.IY
.II

 

In the pictures, the Hytec header is pairing 1/2 and 3/4, but the Comptech header pairs 1/4 and 2/3. Does that have anything to do with whether it is a 4-1 header or a 4-2-1 header?





The Hytech is a 4-2-1 or tri-Y header. It is not a 4-1 header. It just happens to be what we call a "hybrid" header. It has the long equal length, sequential primaries of a 4-1 but also has a tri-Y 4-2-1 layout.
The secondaries are also long. So both primaries and secondaries are long.

Here they are side by side (Hytech vs. Comptech Street)

Look at the Comptech street tri-Y in comparison. It not only pairs 1-4, 2-3 but the primaries are short. Compare it also to the Comptech race hybrid header below.





Quote: Originally Posted by SMSP and also quoted in our header tech article here...
...the firing order is 1-3-4-2, if we add a few more cycles so we repeat, it looks like 1-3-4-2-1-3-4-2-1 etc.

So with a 4-cylinder engine how many tri-y configurations can we have? :

If cylinder #1 is paired with #2, then #3 and #4 are paired.

If cylinder #1 is paired with #3, then #2 and #4 are paired.

However, both these set-ups are considered sequential pairing because each secondary gets 2 back to back pulses.

remember that the 4 stroke inline 4 cylinder only has 2 firing orders possible that doesn't cause excessive vibrations:

a)1-3-4-2 (which is what the Tegs use)

b)1-2-4-3

 

John told me that they used to use reversion chambers in WW1 biplane engines (Snoopy vs. the Red Baron? LOL). Then Feuling "patented" the chambers (even though they weren't his original idea...explain that one to me... LOL) and used them on the bikes and Oldsmobile turbo Quad 4 cylinder that he built. When the patent expired, John used them on his headers. Then John patented them...LOL The guy who invented reversion chambers originally must be laughing for sure...

 

No,
4-1 means all four primaries merge into one collector, while the 4-2-1- means four primaries merge into two Y pipes, then those two secondaries merge into a third Y

Yeah, I knew that, but I wasn't clear with my question. I'll try again.

Did they pair the primaries differently because of the configuration? Why didn't they pair both configurations the same? I was just wondering if it made a difference that the pulses were going down a longer tube in the 4-1 config before they were collected. It seems like to me the pulses would all arrive at the collector about the same for either pairing in a 4-1 and you wouldn't get the benefit of the closer pulse. Wouldn't you only get that forward flow "kick" in a 4-2-1 header?

 

So in summary, sequentially paired primaries results in more kick at the higher rpms leading to more top end power gains whereas nonsequentially paired primaries tend to give more kick in the midrange rpms and broaden the powerband width.

if you want more top end (and if you are looking for a faster NA Integra, you usually focus on gaining power above 6000 rpm using the B18C1 or B18C5 gearing), the sequential design gives you what you are looking for. This thread explains why.

it's all about where the part design makes power and if that lines up with your gearing.

 

I don't know about you but I've noticed that SMSP has gone back to using nonsequential pairing in some of their latest longer hybrid headers.

Perhaps this is done to broaden the powerband further so that the exhaust system is more "forgiving" if you can't line up the powerband with your gearing using tuning methods?

Anyone care to elaborate or add their 2 cents on this?

 

Terry,

I'm using John's Hytech Street hybrid header with the anti-reversion chambers high up and early on in the primaries.

I wish we had some VE numbers comparing headers without chambers vs. headers with, on the same engine.

The Titan Motorsports Great Header Test 3 had a Hytech going against a couple of other hybrid headers without reversion chambers. This test was done on a GSR test mule with ITR pistons, Jun2 intake cam, ITR exh cam, 255 Accel injectors, and a full 2.5 in. system and was fuel tuned for each header.

Here's the Hytech vs. Comptech Race Hybrid Header (no chamber) which has the same overall length and by most accounts was a "clone copy" of the HyTech.

Here's the Hytech vs. DTR (an SMSP-cloned header but the welds aren't as good as the original and I don't think the dimensions are the same either but I'm guessing there) that was actually slightly longer than the Hytech in that test and they chose to run this dyno comparing open headers:

The Hytech (even if it was shorter) out-torqued the other hybrid headers after both were tuned properly from 6000 rpm and up.

Is it the chambers? I have no clue. Could be the differences in collector design or diameters used too. If it was the chambers then the copycats can't clone it on their's for copyright infringement reasons.

 

I would imagine that the chambers are partially the cause of this, but I can't see the pics of the different headers here at work. I know John uses longer primaries and secondaries which gives it more midrange torque, maybe the chambers are what carries that gain throughout the rest of the powerband.

 

if you refer to that pic above that acompanies the dynos, Id say they all were similar or knockoffs when it came to lengths. just from the visual I'd say the anti reversion chambers make a difference.