Loyale 2.7 Turbo Posted August 6, 2015 Share Posted August 6, 2015 ... Make an exhaust too large with little back pressure and it causes issues. How much back pressure is ideal? How do you measure that pressure? From where the exhaust exits the head or 3 metres away? ... In fact, your boxer engine does Not need any "Backpressure", it is a pretty usual confusion, what they need is to join the Left head's exhaust to the Right head's exhaust, in a "Y" shaped pipe (other designs works as well) in order to gain the proper Scavenging effect. So, your exhaust needs Scavenging, not Backpressure. Kind Regards. 1 Link to comment Share on other sites More sharing options...
Loyale 2.7 Turbo Posted August 6, 2015 Share Posted August 6, 2015 It is easy to see how this misunderstanding arises. Lets’ say that Max puts a 3-inch system on his normally aspirated car. He soon realises that he has lost power right through the power band. The connection is made in his throbbing brain …. put on 3" pipe = loss of backpressure = loss of power. Max erroneously concludes that you need backpressure to retain performance. He has ignored the need for exhaust gas velocity to get that scavenge effect. ~► http://www.miata.net/garage/KnowYourCar/S4_Back.html Back pressure at it's most extreme form can lead to reversion of the exhaust stream - that is to say the exhaust will flow backwards, which is not good. The trick is to have a pipe that that is as narrow as possible while having as close to zero back pressure as possible at the RPM range you want your power band to be located at. Exhaust pipe diameters are best suited to a particular RPM range (remember the pulses!). A smaller pipe diameter will produce higher exhaust velocities at a lower RPM but create unacceptably high amounts of back pressure at high rpm. Thus if your power band is located 2000-3000 RPM you'd want a narrower pipe than if your power band is located at 8000-9000 RPM. ~► http://www.gomog.com/allmorgan/exhaustbackpressure.html Kind Regards. 1 Link to comment Share on other sites More sharing options...
Loyale 2.7 Turbo Posted August 6, 2015 Share Posted August 6, 2015 (edited) There's a Friend in England, he's also here @ USMB, Running a Blue Brumby / Brat \ MV ute, with SUB4 modified EA81. Have you seen it? ... ~► http://www.ultimatesubaru.org/forum/topic/122906-the-awesome-older-generation-picture-thread/page-26?do=findComment&comment=1064468 SUB4 is pretty similar to RAM engines. Kind Regards. Edited August 6, 2015 by Loyale 2.7 Turbo Link to comment Share on other sites More sharing options...
tweety Posted August 7, 2015 Share Posted August 7, 2015 Very interesting reading. Think I'll read it twice lol Here is my trike exhaust with that common pipe. 1 Link to comment Share on other sites More sharing options...
culater Posted October 4, 2018 Share Posted October 4, 2018 (edited) I have the Ram Dual intake EA81 heads with stainless oversized valves, bronze guides and HD springs with only 25 hours of use. I also have the Ram custom Aluminum Dual intake with a like new Weber 38 carb. Serious HP gains with this set up! I also have a custom single intake with a like new Weber 32/36 carb. I will entertain any offers. I can be reached at 860-86six-61zero4 or PM me Edited October 4, 2018 by culater 1 Link to comment Share on other sites More sharing options...
jono Posted October 6, 2018 Share Posted October 6, 2018 goodness me ! I wonder if it was made to fit under the standard height bonnet? Is there a specific cam to go with it? Is something like this also good mud puddle crawler or would it dig your way through the other side of the world? Link to comment Share on other sites More sharing options...
el_freddo Posted October 8, 2018 Share Posted October 8, 2018 It's good for flying with Jono! i hunk it's got a flat torque curve - an important feature of an aircraft engine as far as I know. Cheers Bennie Link to comment Share on other sites More sharing options...
culater Posted October 25, 2018 Share Posted October 25, 2018 On 10/5/2018 at 9:57 PM, jono said: goodness me ! I wonder if it was made to fit under the standard height bonnet? Is there a specific cam to go with it? Is something like this also good mud puddle crawler or would it dig your way through the other side of the world? These heads will work with any cam and also fit under your bonnet. A K&N high flow air filter also comes with it. these Ram heads with the custom intake and Weber carb were over 2500.00 I will sell for 800.00 plus shipping Link to comment Share on other sites More sharing options...
83subaruGLchick Posted October 25, 2018 Share Posted October 25, 2018 On 10/4/2018 at 4:58 AM, culater said: I have the Ram Dual intake EA81 heads with stainless oversized valves, bronze guides and HD springs with only 25 hours of use. I also have the Ram custom Aluminum Dual intake with a like new Weber 38 carb. Serious HP gains with this set up! I also have a custom single intake with a like new Weber 32/36 carb. I will entertain any offers. I can be reached at 860-86six-61zero4 or PM me I’d be very interested in knowing how much you’d get rid of the DOHC heads and intake manifold for. Link to comment Share on other sites More sharing options...
culater Posted October 25, 2018 Share Posted October 25, 2018 1 minute ago, 83subaruGLchick said: I’d be very interested in knowing how much you’d get rid of the DOHC heads and intake manifold for. 800.00 + shipping Link to comment Share on other sites More sharing options...
el_freddo Posted October 25, 2018 Share Posted October 25, 2018 7 hours ago, 83subaruGLchick said: I’d be very interested in knowing how much you’d get rid of the DOHC heads and intake manifold for. Not double over head cams! ”Just” dual intake heads. Very custom and I’d imagine very well built. I’d be keen to see a set these in the flesh just for curiosity. Cheers Bennie Link to comment Share on other sites More sharing options...
83subaruGLchick Posted October 25, 2018 Share Posted October 25, 2018 14 hours ago, culater said: 800.00 + shipping Pmed. Very interested Link to comment Share on other sites More sharing options...
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