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| extractors https://www.ausmini.com/forums/viewtopic.php?f=2&t=4231 |
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| Author: | sean [ Sat Jan 22, 2005 9:38 pm ] |
| Post subject: | extractors |
What difference do extractors make ? in terms of power etc |
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| Author: | min13k [ Sat Jan 22, 2005 9:45 pm ] |
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not alot unless you do other mod's but hell it will sound good |
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| Author: | Tinkz [ Sat Jan 22, 2005 9:59 pm ] |
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Power wise you will notice nothing really, they help the engine breathe better, give it a better note and increase fuel economy. If you take away the back pressure you will lose power and have to rev the bags out of it to get it up to speed.... well more than usual anyway. 
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| Author: | sean [ Sat Jan 22, 2005 10:03 pm ] |
| Post subject: | |
so I will have to rev it higher if I fit them |
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| Author: | Tinkz [ Sat Jan 22, 2005 10:08 pm ] |
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only if you have just a hotdog on it like "Beefa". A proper sports system will be the best option in my opinion. |
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| Author: | sean [ Sat Jan 22, 2005 10:23 pm ] |
| Post subject: | |
what is a hotdog ? |
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| Author: | Tinkz [ Sat Jan 22, 2005 10:25 pm ] |
| Post subject: | |
Pretty much a type of resinator, not muffler that looks just like a hotdog in bread. its only got fibreglass on its walls and has no baffles in it. its usually used as the last noise breaker on exhaust systems. |
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| Author: | sean [ Sat Jan 22, 2005 10:30 pm ] |
| Post subject: | |
so if I fit the extracters everything will be fine even though i have just a normal exhaust system on |
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| Author: | Tinkz [ Sat Jan 22, 2005 10:33 pm ] |
| Post subject: | |
Yes that will be fine if you do that. Your fuel economy will be better and your motor will have sufficient back pressure. |
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| Author: | sean [ Sat Jan 22, 2005 10:42 pm ] |
| Post subject: | |
Thanks mate |
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| Author: | gafmo [ Sun Jan 23, 2005 5:47 am ] |
| Post subject: | |
 if you lose power with a straight through Exhaust
Why then does the top fuelers v8's and sprint cars Etc run them 
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| Author: | grub [ Sun Jan 23, 2005 8:07 am ] |
| Post subject: | |
What the??? Excuse me if I am wrong but isn't back pressure BAD. The engine has to work harder to expell the exhaust gases. The engine wants to get rid of exhaust gas doesn't it? Then why are you trying to stop the gasses from expelling? You want the engine to work harder to try and over come back pressure? Don't think so! And what would happen if your engine has a longer period cam (overlap)? When one cylinder is still closing and removing exhaust gases, and the next cylinder is opening for intake, with back pressure there is a good chance that the exhast gasses will enter the new intake cylinder. Not good! What would be ideal is an exhaust system that actually "pulls" the exhaust gases out of the cylinder and system. The whole exhaust system needs to be tuned to help with this. Extractors being a part of this. Example: a cylinder fires, gases flow into the extractors, and make to to the point on the extractors where the pipes all meet. Then the next cylinder fires, and gases flow into extractors, the gases from the first firing have made it past the point when the pipes join and are heading out to the silencer (mufler). This first group of exhaust gases has a pulling effect which the second set of exhaust gases then joins. Then the third set of gases join, then the forth, etc... This would be an ideal setup where the exhaust system extracts the gases from the engine allowing more power produced from the engine to be used to drive the wheels. Why do you think they call them extractors? Two other bits are required for them to work correctly. One being a decent silencer. This is the first thing the exhast pipes go into from the extactors. Like what Tinkz said, you want a silencer that doesn't have baffles and allows the exhast gases to flow relatively freely through to the other side. If it's retrictive, then it is like having a lid on a coke bottle and trying to pour the coke out. It just ain't going to work. This creates "Back Pressure".... And the other thing that helps an exhaust system flow is pipe size. Small is not good as it is to restrictive. Like trying to blow up a baloon through a straw. Big is also *not good*. You often see people with huge exhaust systems on little cars. The gases do not flow effectively from this type of system. It all comes down to "gas speed". As I mentioned earlier you want an exhaust system that pulls the exhaust gases out. This effect is caused by "gas speed". When your pipes are too large then the gas speed is low and the exhaust doesn't leave the system efficiently. But I could be wrong above. I am new to this. I just read a book and now think I am an expert! 
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| Author: | lobby69 [ Sun Jan 23, 2005 8:45 am ] |
| Post subject: | |
with a hot cam u get alot of overlap....meaning both valves are open at the same time! at low rpm, (before thre cam kick in) u will find that the motor will tend to cof and splutter a bit as there is not enough momentum for the exhaust gasses to be expelled through the exhaust port, (called CAMMINESS) when the rpm rises, (say 2700rpm ON CAM) u start to get a flow, so u end up with greter volume of clean air with less burnt carbon, i read that out of TUNING BL's A SERIES, (very good book!) i found with extractors u end up with alot cleaner, and responsive engine, blake
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| Author: | Chris [ Sun Jan 23, 2005 10:18 am ] |
| Post subject: | |
gafmo wrote: :?: if you lose power with a straight through Exhaust
Why then does the top fuelers v8's and sprint cars Etc run them There has been big thick books written on this subject. |
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| Author: | mickmini [ Sun Jan 23, 2005 10:52 am ] |
| Post subject: | |
grub is right on every point. i hereby declare you expert 
extractor will give you more power and better fuel ecomomy at the same time for all the reasons grub quotes. the standard cast iron A-series manifold is woeful in terms of how much it restricts the gas flow. why do think that coopers and cooper s came from the factory with the 3-1 extractor (freeflow) system??? the cast iron ones are used by manufacturers because they are cheap.
your only question is how much improvement in power will extracotrs make. my experience with a bog stock 998 engine is that with no other changes, just fitting the 3-1 extractors and a 1.75" exhaust, with a big (for falcons & crummydores) muffler, i had a noticable power increase. This was limited by the valves bouncing at high revs, rather than the running out of breath, even with a standard 1.25" SU on a standard manifold with the exhaust half ground off. Never had it on a dyno before and after, so you could argue that it was just wishful thinking, rather than scientifically proven The reason i used that muffler, is because it is designed to flow enough gas from a standard 4 litre engine, although probably restrictive in that application, it will have bugger all restriction on a 1 litre engine. Ever seen some of the rotary boys saying that they are using a truck muffler? same theory applies. For the $200 odd for a LCB extractor and exhaust from karcraft, i reckon its worth it in a power increase even without doing anything else. michael |
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