Some years back anti-reversion exhaust manifolds were going to be the hot ticket, oversized primaries with cones to prevent eddy currents reversing back into the cylinders at low RPMs-......Torque and horsepower!
For some reason, (which I don't know) this never caught on (only reason I could find is "they worked too well" ...??????)

Has any tried this principle on the inlet runners - ie fat long tubes with cones at the plenum end. Or am I way too late with this idea?

 

Sorry Brit, never heard of that.

 

those anti-reversion baffles work great in the exhaust IF the EXHAUST is correctly designed for their use, the only reason I could find for the lack of use is the fact they work far more effectively without a muffler systems restiction behind the headers and the higher costs involved in the fabrication of the exhaust system. put bluntly they failed to sell well because correctly designed systems were not what was being sold by most of the companies, the designs being sold were modified for ease of production and performance to lower the price. a correctly designed system needs to have the cam timing,engine displacement,stroke, connecting rod length,compression ratio, engine torque peak,collector dia./lenght/tapper and primairy tube length ,ETC. matched to the systems design for the best cylinder scavageing efficiency. that would of course require dozens of differant headers for every car , makeing the cost of EFFECTIVE headers very high
the FEULING company pattened the baffles, and the costs involved made cost effective headers cost more than most consumers would pay.

btw for those of you not familiar with what we were talking about, gains of up to 80ft lbs of tq were available from a 350 chevy engine at some rpm ranges.
the feuling company baffles were basically small metal tappered short sections of pipe welded into the header primairy tubes that started at exhause port size and exited into a larger primairy about 1"-2" into the primairys that partly blocked the reversion pressure pluses from entering the exhaust ports, and maximized the negitive pressure pulse strength that scavanged the cylinder
http://www.victorylibrary.com/mopar/header-tech-c.htm

http://www.victorylibrary.com/mopar/header-tech-c.htm



[Modified by grumpyvette, 6:11 PM 5/8/2003]

 

Thanks for that, Grumpy, but what thoughts on using this principle on the inlet runners?

 

The reversion you seem to be associating with the TPI intake tract generally only occurs with cams with a good deal of overlap...Something that should be avoided at all cost on the long runner TPI setups.
-Jeb

 

exactly. that is why the tpi runners are long, to avoid reversion - (isn't it?). and that is why short LT1, miniram etc lose torque at low RPMs. I was thinking of big bore runners- to give high rpm perfomance , with anti reversion cones to give low Rpm grunt. L98 and LT1 in one package.

Or am I talking bul***t?


[Modified by britvette, 5:53 PM 5/9/2003]

 

That's not really the purpose of a tuned runner manifold but it does end up doing that in a way...However none of the factory cams nor most of the aftermarket one designed for the tuned runner intakes have much overlap (if any) anyway. I understand your position of effectively shortening the runners by way of enlargement and adding anti-reversion cones to allow more camshaft...But, you still run into the problem that you STILL have a lot of runner to deal with and anti-reversion additions or not you'll be above the ideal operating range of the manifold if you install a cam with lots of overlap...
-Jeb
PS- Forgot..If you want a cross between the LT1 and the L98 look at the LS (Gen3) engine family's intake design...


[Modified by jburnett, 5:09 PM 5/9/2003]

 

Thanks for your consideration and input, Jeb - I wont even mention reed valves.........


John :rolleyes:

 

You can effectively double the runner diameter with the siameses base; so far it has produced a substantial increase in top end breathing with a minor (apparently) loss of low end torque.

 

Sorry to be late to the party.

My information is that Jim Fueling did initial work on VWs and then on V8s.
There is an article I can dig up that cites his developments with the Pettys
of NASCAR. His A/R cone concept was commercialized - either Cyclone
or Heddman offered A/R headers for a few popular combos. That petered
out and an outfit with something to do with rail diesels was in the act for
a time but I never saw/heard of any product from them. A/R pipes for
Harleys and other bikes were sold for a time.

My opinion is that besides cust disapppointment from misapplication, mfr's
were also dissuaded by the issues involved with creating the A/R cone so
that it fulfilled the design criteria and could still be attached to the heads.
The siamesed ports on a SBC head are an example where the ideal
layout had to be compromised. Engine compartment dimensions meant
it was nigh impossible to meet the ideal of having a straight run for 6"
(IIRC) out from the port before introducing any directional transitions.

Perhaps as a consequence of issues implementing the A/R cone, step
headers began to be popular. The conventional flanges could be used
and followed by the necessary bends out of the ports, then changes
in pipe section (larger) were added further down the primaries where
space permitted. The increase in section creates a change in velocity
and the mechanical structure presents an interruption to the negative
pressure wave. People claimed these work - maybe, but not (IMO)
because they were anywhere close to the principals Fueling published.

FWIW - I have a set of A/R headers and a complimentary exhaust
system all built according to the principals laid out in Jim Fueling's
patent(s). The system includes a LARGE chamber intended to
represent atmospheric conditions to the exhaust prior to its
reaching the end of the tail pipe. This is for a BBC w/oval port
intakes and exhaust ports that have been raised 3/8".

As for the intake side of things. Design space for something like an
A/R cone is usually even more constrained at the intake than at the
exhaust port. Also, piston displacement while the valve is open
might be more of a factor than reversion is on the intake side.
Still, if it's been tried, I bet it was tried in NASCAR racing.

 

..Or just try these Runners.. :jester
http://forums.corvetteforum.com/zerothread?id=559252