Tony D Posted November 3, 2006 Share Posted November 3, 2006 What do you know? Threads discussing "Anti Reversionary Headers". http://www.kiwibiker.co.nz/forums/archive/index.php/t-11713.html http://forums.bimmerforums.com/forum/archive/index.php/t-449389.html http://www.riveraengineering.com/cat05/sect/Exhaust_Section.pdf (Page 8 mentions the AR Headers) https://www.headersbyed.com/stepped.htm http://www3.bc.sympatico.ca/Volvo_Books/maint4.html (probably most directly related to the discussion) http://cgi.ebay.com/ebaymotors/Anti-Reversion-Cones-Torque-Cones-For-Harley-Shovelhead_W0QQcmdZViewItemQQcategoryZ35573QQitemZ4598093594 (Bit extreme, but they call them "torque cones") Dealing with the Intake end of it: http://www.magnafuel.com/products/accessories/revPlates/index.htm http://productengr.com/shear_plates.htm (introduces me to the name "shear plate" which I was formerly unfamiliar with) A photo of what V-8 Guys install as "anti-reversion shear plate" under their carbs, same thing can be manufactured or machined into individual runner intakes, or done with the "step" I mentioned in the post above. From this website: http://www.rehermorrison.com/indexStart.htm Tech Article here: http://www.popularhotrodding.com/enginemasters/articles/pontiac/0606em_pontiac_racing_engine/pontiac_engine.html BANNED in some racing classes: http://www.elkospeedway.org/lmr.html My gawd, a thread involving (shudder) Corvettes with someone discussing the same anti-reversion technology specifically relating to port-matching and details their technique of a 'reversion wall' at the head-intake juncture of .202 to .030" (so about 1mm total diametrical difference): http://forums.corvetteforum.com/showthread.php?t=1409861 This one shows the technique has been around for some time...Ford Flathead anti-reversion steps!!! http://www.flatheadv8.org/bishop/porting1.htm So the terminology of "Anti Reversion" is applicable in both Internal Combustion Exhaust and Intake design---though not gas pipelines! LOL Some of that should get you the understanding of the phenomenon I was referring to above. Quote Link to comment Share on other sites More sharing options...
Zmanco Posted November 3, 2006 Share Posted November 3, 2006 Yasin where did ya pick up those rasps?? I have a set from Harbour Freight but .. ehh Ryan, I found a few non-ferous tools at AAA Trading post. They didn't have much of a selection and they're not cheap. Good news is they don't clog. Quote Link to comment Share on other sites More sharing options...
Dragonfly Posted November 3, 2006 Share Posted November 3, 2006 so how can you have backflow anyway?Yasin During valve overlap when both valves are open and the piston is still moving upward you can get "backflow" into your intake. If you are turbo charged and your intake pressure is greater than your cylinder pressure at the time it will push everything out the exhaust valve. As I recall anti reversion as seen in the automotive world was discovered by racers and has been used to help with scavaging exhaust out of the cylinders. Dragonfly Quote Link to comment Share on other sites More sharing options...
Cethern Posted November 3, 2006 Share Posted November 3, 2006 Ok Now that I got a N-42 and I was thinking about port matching, Something I have long thought to be a goodthing. Now I read I should pretty much leave it alone and run it... Did I miss something? Yes I would like to have a lonewolf but for right now I can put money in other places. Cethern Quote Link to comment Share on other sites More sharing options...
naviathan Posted November 3, 2006 Share Posted November 3, 2006 :GolfClap: Bravo Tony, excelent sources. Looks like I have some reading to do today...lol Quote Link to comment Share on other sites More sharing options...
slownrusty Posted November 4, 2006 Author Share Posted November 4, 2006 I quickly browsed some of those links - the intake threads only. The 4barrel carb plates are simply "bore extenders" as even described by Magna and also the Shear Plate - there is no wall or lip to prevent reversion. There is no step with their product and their product is more designed for "the prevention of fuel from dripping from the base of the carburetor's bores". The Corvette thread talks of a lip of 0.5mm (0.020") which is TINY! I have easily that on my head to intake face. Curious why all the intake links are all Domestic V8 related with no discussion or use in more modern or import engines? Alos many of those links talk about using this anri-reversion running what sounds like really wild or radical camshafts as many of the Domestic guys run, which is not applicable to us Turbo guys. Thanks for taking the time for finding posting those links. Must get back to assembling my engine. Yasin Quote Link to comment Share on other sites More sharing options...
Tony D Posted November 4, 2006 Share Posted November 4, 2006 I quickly browsed some of those links - Alos many of those links talk about using this anri-reversion running what sounds like really wild or radical camshafts as many of the Domestic guys run, which is not applicable to us Turbo guys. Again, take it for what it's worth, JeffP's engine was ported with an anti-reversion step by BCG, and it's a turbo motor like yours. The pre-eminent head porter of L-Engines during the heyday of Electromotive's Development of turbocharged headwork says it helps, and I take him at his word. I have seen Jeff's intake before and after the mod... Like I said in the beginning, it's for overlap at low speeds with big cams. If you think what is applicable to domestics is not applicable to imports, I'm not going to change your mind. If you can't see the advantages of a dynamic check-valve of sorts in either on or off-boost operation, again I am not going to change your mind. Someone may benefit from it, it's not B.S. I just am not going to take the time to search exhaustively to convince someone what works and what doesnt. Good luck with that intake. BTW, there was import stuff on there or maybe it was some stuff from the mitsu and bimmer sites that doesn't count... A Turbo usually has higher exhaust pressure than intake pressure, if you like exhaust gas reverting into the intake for the first three inches of the runner... Quote Link to comment Share on other sites More sharing options...
Administrators RTz Posted November 5, 2006 Administrators Share Posted November 5, 2006 Like I said in the beginning, it's for overlap at low speeds with big cams. Well said, Tony A Turbo usually has higher exhaust pressure than intake pressure I'll second that... and I'll go so far as to say always has higher exhaust pressure than intake. Quote Link to comment Share on other sites More sharing options...
Tony D Posted November 5, 2006 Share Posted November 5, 2006 Well, someone with a hybrid turbo did some exhaust pressure readings compared to intake pressure and he was running 23psi in the exhaust to 23psi in the intake.... that is as good as some old F1 Turbo setups! Same setup now with bigger exhaust turbine, anti-reversion step in the intake, and much less reversion than when he had equal exhaust and intake pressures! But I digress.... Quote Link to comment Share on other sites More sharing options...
Administrators RTz Posted November 5, 2006 Administrators Share Posted November 5, 2006 Interesting Tony, I didn't think anybody had reached that level of efficiency. Cool stuff. Quote Link to comment Share on other sites More sharing options...
Tony D Posted November 6, 2006 Share Posted November 6, 2006 Scary thing is the turbine is larger now, the cam is bigger now, and the intakes flow more now! He is actually thinking that he may be out of fuel slightly over 18psi now, quite a bit earlier than what he projected. The thing is literally eating air as he mashes the throttle. It will be interesting to see what the pressure surveys come back with when they get done this round of mods! Quote Link to comment Share on other sites More sharing options...
Administrators RTz Posted November 7, 2006 Administrators Share Posted November 7, 2006 It will be interesting to see what the pressure surveys come back with when they get done this round of mods! You're expected to share Quote Link to comment Share on other sites More sharing options...
peej410 Posted November 8, 2006 Share Posted November 8, 2006 my minimal work in header design has taught me to not ignore the pulses created by the valves opening and closing. dont forget theres a pressure wave AND a sound wave. im assuming intakes work similarly but i may be wrong. Quote Link to comment Share on other sites More sharing options...
naviathan Posted November 8, 2006 Share Posted November 8, 2006 The pulses created in a header are caused by positive pressure bursts into the runner. An intake has a negetive pressure therefor doesn't suffer the same pulses as a header. Even in a forced induction, the pressure being pushed into the intake is steady and doesn't have pulses or they are negligible. The principles to keep in mind with an intake is air speed, fuel atomization, and air fuel metering. When an intake valve closes the air obviously comes to halt. Thanks to valve overlap the flow isn't just stopped instantly, which would cause a sudden pulse, but it is slowed by the the piston pushing up before the valve closes. It's really hard to explain with out a whiteboard and some representative drawings. Quote Link to comment Share on other sites More sharing options...
peej410 Posted November 8, 2006 Share Posted November 8, 2006 very interesting, i never thought to take into account the pos vs neg pressure. cool stuff! Quote Link to comment Share on other sites More sharing options...
Tony D Posted November 8, 2006 Share Posted November 8, 2006 The pulses created in a header are caused by positive pressure bursts into the runner. An intake has a negetive pressure therefor doesn't suffer the same pulses as a header. Even in a forced induction, the pressure being pushed into the intake is steady and doesn't have pulses or they are negligible. The principles to keep in mind with an intake is air speed, fuel atomization, and air fuel metering. When an intake valve closes the air obviously comes to halt. Thanks to valve overlap the flow isn't just stopped instantly, which would cause a sudden pulse, but it is slowed by the the piston pushing up before the valve closes. It's really hard to explain with out a whiteboard and some representative drawings. If you think an intake manifold does not have pressure pulses, nor sonic tuning that makes a difference you are sadly mistaken. There are pulese in an intake tract, and there IS a reverse flow phenomenon that can be combatted using anti-reversion porting techniques. The highlighted portion in the quote is one of the reason there are pulses, but the portion of the stroke that is being affected is that portion of the flow talked about (I won't get into it) in the underlined portion of the quote. it the the portion of time as the airstream is slowing----when that exhaust valve is open and there is still pressure above intake pressure left in the cylinder, where anti-reversion designs optimize the airflow and minimized intake charge dilution through either contamination of exhaust gasses (built in EGR), or by keeping speed high and impedeing any reverse flow as best possible. We can get into changing the phase angle of the injection event so as to have the air/fuel mass coincide with an open intake valve allowing leaner fuel metering charts.... there is a lot of stuff that is high-end tuning that people simply dismiss as "hogwash" because they have never taken the time to investigate it, or to look how high-end successful racing orginisations design intakes and etc... Quote Link to comment Share on other sites More sharing options...
MrFancypants Posted November 8, 2006 Share Posted November 8, 2006 On the subject of porting tools, I have used Eastwood's stuff: http://www.eastwoodco.com/jump.jsp?itemID=15223&itemType=PRODUCT I'd be very cautious using a burr on soft aluminum. On slip could ruin your day. 80 grit sanding drums/tapers are much safer. Also dont forget to get the grinders grease. Coupled with a $5 Harbor Freight die grinder, and youre all set. - Greg - Quote Link to comment Share on other sites More sharing options...
naviathan Posted November 8, 2006 Share Posted November 8, 2006 Ok, Tony, I see where you're saying there could be a pulse during the overlap from exhaust to intake. I don't see that happening however because the piston dropping as the intake opens would neutralize any pressure difference before pulling from the intake and closing the exhaust. I'd really rather not start a huge debate on this subject, but as I've said before Tony is extremely intelligent in these areas. On this particular point though I think I'd have to disagree. An exhaust gets a huge burst of pressure being released where as an intake is a smooth flow drawing in and a slight push out. The pressure in the intake neutralizes before changing direction therefore stopping any sort of pulse from being created. Anti-reversion efforts are used in intakes to help balance the tranistions from cylinder to cylinder and keep from creating a huge positive pressure pocket within the intake that could cause things like pre-fire which can seriously damage seals, sensors, injectors, jets, valves, etc... When you start doing some serious fine tuning for things like that you're looking at a high race engine with a heavy cam and lots of overlap. Anyhow, I digress. Again, I need a white board. Quote Link to comment Share on other sites More sharing options...
peej410 Posted November 8, 2006 Share Posted November 8, 2006 ugh, you guys make me want to go back and finish my degree! Quote Link to comment Share on other sites More sharing options...
naviathan Posted November 9, 2006 Share Posted November 9, 2006 One of these days maybe I'll get one. Until then I'll make do with the internet and books. Quote Link to comment Share on other sites More sharing options...
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