2006 WRX!
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so is an uneven extractor good or bad?Originally posted by HENG@:technically yes. an extractor is basically the exhaust system -
aiyaa why dun just say exhaust... ahahahOriginally posted by HENG@:technically yes. an extractor is basically the exhaust system
i guess i will know why sooner or later. thanks for the info anyway
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yeah. i think indeed got 2.5L version. saw it from the pricelist i downloaded from motor image webby..price stated @ S$93k?? i dunno if they made an error on it.
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i really dunno how to answer this on an absolute level. Its too interwoven with so many factors like engine design and overall packaging and design of the car to make a judgement on whether is is good or bad.Originally posted by TwinTurbo_Supra:so is an uneven extractor good or bad? -
erm.....runnin 2.0bar boost on a stock rex is quite unbelievable(tink twice,its impossible) most likely engine wil blow ehehe.achieve power for turbo car is easy,but to achieve smooth power delivery is hard.tink thrice b4 doin tat to ur car.
*Peace* -
yea...becoz the WRX is using a small turbo...Originally posted by nitsujoey:erm.....runnin 2.0bar boost on a stock rex is quite unbelievable(tink twice,its impossible) most likely engine wil blow ehehe.achieve power for turbo car is easy,but to achieve smooth power delivery is hard.tink thrice b4 doin tat to ur car.
*Peace*
setting boost at 2 bar can only be tolerated by big turbos.... -
Can. Just adjust the gauge to let more air flow so as to simulate that it is boost to 2. When the real fact is that it is only at 0.5 boost.Originally posted by ceecookie:yea...becoz the WRX is using a small turbo...
setting boost at 2 bar can only be tolerated by big turbos....
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theoretically, bad.Originally posted by TwinTurbo_Supra:so is an uneven extractor good or bad?
uneven extractor lengths means dat the distances the exhaust travels are unique 2 each cylinder passing them out.
wad it essentially translate into is that for the same 4 stroke cycle, the exhaust from each cylinder travels at a different speed with respect to each other b4 they meet at the downpipe. this creates turbulence in the flow of the exhaust and the distinctive "boxer" note (exhaust coming out in "bubbles"). this reduces the efficiency of the engine. well tuned rexes nowadays have basically eliminated this prob (u dun really hear the "boxer note" from wrc rexes now do u?). -
Hmm... so the final product should come out sounding somewhat like Porsche's Boxers?
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theoratically, but we do not know for sure all the intricacies of the boxster engine do we? I suppose I can only say for sure it should sound like a flat config engine on a test bench.Originally posted by Kr0n:Hmm... so the final product should come out sounding somewhat like Porsche's Boxers? -
Hmm..let's see.
If the extractor lengths were different,
1. the firing order/timing of the pistons have to be adjusted according so that it won't mess up the crankshaft rotation and possibly cause premature detonation
2. compression ratio in certain cylinders might be different, to accommodate the difference in power output so as to help achieve better rotational balance in the crankshaft
3. exhaust system design will need more than the usual calculations to ensure proper exhaust flow rate.
If the extractor lengths were the same, then all of the above can be forgotten..
Correct me if I'm wrong please
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dun tok rot lah. the engine internals will melt before the turbo can hit 2 barsOriginally posted by ceecookie:yea...becoz the WRX is using a small turbo...
setting boost at 2 bar can only be tolerated by big turbos.... -
not really. each cylinder is in a different stroke at any one time so it's quite impossible 2 get any 2 to be doing the same thing at any given time. it is possible to seriously bend some internals with bad ignition timing but then again that is a problem with any motor, not juz boxers or engines with diff extractor lengths.Originally posted by Kr0n:Hmm..let's see.
If the extractor lengths were different,
1. the firing order/timing of the pistons have to be adjusted according so that it won't mess up the crankshaft rotation and possibly cause premature detonation
2. compression ratio in certain cylinders might be different, to accommodate the difference in power output so as to help achieve better rotational balance in the crankshaft
3. exhaust system design will need more than the usual calculations to ensure proper exhaust flow rate.
If the extractor lengths were the same, then all of the above can be forgotten..
Correct me if I'm wrong please
shouldn't fool around with compression too much either. as it is, the uneven extractors are giving a different set of parameters to the way the engine works. having unique CRs for each chamber isn't really an option to counteract this effect. in fact, u gonna give the ecu will have a hard time figuring out wad inputs to give the injectors and wad 2 do with the the map readings because it now has to get its readings from each individual cylinder due to the variations in CR.
well, its really how the gases meet at the down pipe, not how the exhaust is designed. a typically well set up exhaust system should consist of a set of extractors with equal flow rates relative to the primary and secondary pipes as well as a sufficiently free flowing center and muffler pipes.
all the above holds unless i'm not thinking properly tonite -
erm.. i'm new here so no offence intended to the some of the senior members here... correct me if anything...
WRX/STi have the boxer rumble simply because of the unequal length headers.. aka exhaust manifold.. swap it out .. with an equal length headers... you'll lose the rumble...
whether equal or unequal... it doesnt equal to better or worse.. though in theory.. equal length sounds more efficient... it doesnt make a difference whether the exhaust gas travels out at difference speeds from the cylinders.. what makes more of a real difference is the amount of backpressure.. from the upipe..downpipe and catback...the lesser back pressure.. the faster the exhaust flows out.. the more HP..
some well tuned rexs still have the boxer rumble... that depends largely on the exhaust manifold they use... or turboback they have... certain exhaust systems such as the HKS ti carbon catback.. actually deepens the rumble.. making it sound more pronounce...
and WRC car do have the rumble... just that its in a higher,sharper tone as opposed to modded rexs.. that have a deeper tone.. ... -
i just need to point out that last point u mentioned about WRC cars. ALL WRC car engines sound the same, so I do think that the impreza WRC car doesn't have the rumble. The high pitched rumbling u hear is more due to the sort of engine components typically used in WRC cars.Originally posted by shicane:erm.. i'm new here so no offence intended to the some of the senior members here... correct me if anything...
WRX/STi have the boxer rumble simply because of the unequal length headers.. aka exhaust manifold.. swap it out .. with an equal length headers... you'll lose the rumble...
whether equal or unequal... it doesnt equal to better or worse.. though in theory.. equal length sounds more efficient... it doesnt make a difference whether the exhaust gas travels out at difference speeds from the cylinders.. what makes more of a real difference is the amount of backpressure.. from the upipe..downpipe and catback...the lesser back pressure.. the faster the exhaust flows out.. the more HP..
some well tuned rexs still have the boxer rumble... that depends largely on the exhaust manifold they use... or turboback they have... certain exhaust systems such as the HKS ti carbon catback.. actually deepens the rumble.. making it sound more pronounce...
and WRC car do have the rumble... just that its in a higher,sharper tone as opposed to modded rexs.. that have a deeper tone.. ... -
talking about compression, who was it who once had a CR of 13:1 in their old EK or EG ah? Was it you? Or am I thinking of someone else?Originally posted by tailslide:not really. each cylinder is in a different stroke at any one time so it's quite impossible 2 get any 2 to be doing the same thing at any given time. it is possible to seriously bend some internals with bad ignition timing but then again that is a problem with any motor, not juz boxers or engines with diff extractor lengths.
shouldn't fool around with compression too much either. as it is, the uneven extractors are giving a different set of parameters to the way the engine works. having unique CRs for each chamber isn't really an option to counteract this effect. in fact, u gonna give the ecu will have a hard time figuring out wad inputs to give the injectors and wad 2 do with the the map readings because it now has to get its readings from each individual cylinder due to the variations in CR.
well, its really how the gases meet at the down pipe, not how the exhaust is designed. a typically well set up exhaust system should consist of a set of extractors with equal flow rates relative to the primary and secondary pipes as well as a sufficiently free flowing center and muffler pipes.
all the above holds unless i'm not thinking properly tonite 
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13:1??????? *faints*
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oh apparently the engine blew up after awhile.Originally posted by Kr0n:13:1??????? *faints* -
Heh later his reply is only
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back pressure is but one factor which accounts for the efficiency of the exhaust system. which as the name implies, operates as a system. meaning, no single component accounts for the factor "back pressure" on its own.Originally posted by shicane:erm.. i'm new here so no offence intended to the some of the senior members here... correct me if anything...
WRX/STi have the boxer rumble simply because of the unequal length headers.. aka exhaust manifold.. swap it out .. with an equal length headers... you'll lose the rumble...
whether equal or unequal... it doesnt equal to better or worse.. though in theory.. equal length sounds more efficient... it doesnt make a difference whether the exhaust gas travels out at difference speeds from the cylinders.. what makes more of a real difference is the amount of backpressure.. from the upipe..downpipe and catback...the lesser back pressure.. the faster the exhaust flows out.. the more HP..
some well tuned rexs still have the boxer rumble... that depends largely on the exhaust manifold they use... or turboback they have... certain exhaust systems such as the HKS ti carbon catback.. actually deepens the rumble.. making it sound more pronounce...
and WRC car do have the rumble... just that its in a higher,sharper tone as opposed to modded rexs.. that have a deeper tone.. ...
sure, more free flow pipe and muffler = lesser back pressure is great for power production, but having unequal extractors does have its drawbacks on how efficient these items work in tandem as one entire system.
imagine (i know nothing happens perfectly and as slowly in real life) each cylinder produces x cm3 of exhaust in a single exhaust stroke. it may take extractor primary 1 twice as long to transfer x amount of exhaust to the downpipe than extractor primary 4 which is shorter. while this is happening, the 2nd and 3rd and so forth exhaust strokes are creating 3x, 4x..... "clogging" up primary 1 compared the exhaust in primary 4 which may have already reached the down pipe.
multiply the effect in an engine typically operating in the range of 1k-6k rpms, u have pretty chaotic situation there. -
it was someone elseOriginally posted by HENG@:talking about compression, who was it who once had a CR of 13:1 in their old EK or EG ah? Was it you? Or am I thinking of someone else? -
orh. must be the porsche brakes WRX guy then.Originally posted by tailslide:it was someone else -
read again...i did not say put 2 bar on the WRX lah....Originally posted by tailslide:dun tok rot lah. the engine internals will melt before the turbo can hit 2 bars
i was saying 2 bar is only for those engine with big turbo and reinforced engine parts -
i understand what you're saying. and in theory, it does make perfect sense that unequal length exhaust manifolds has its disadvantages due to the different lengths the exhaust has to travel from the cylinders.Originally posted by tailslide:back pressure is but one factor which accounts for the efficiency of the exhaust system. which as the name implies, operates as a system. meaning, no single component accounts for the factor "back pressure" on its own.
sure, more free flow pipe and muffler = lesser back pressure is great for power production, but having unequal extractors does have its drawbacks on how efficient these items work in tandem as one entire system.
imagine (i know nothing happens perfectly and as slowly in real life) each cylinder produces x cm3 of exhaust in a single exhaust stroke. it may take extractor primary 1 twice as long to transfer x amount of exhaust to the downpipe than extractor primary 4 which is shorter. while this is happening, the 2nd and 3rd and so forth exhaust strokes are creating 3x, 4x..... "clogging" up primary 1 compared the exhaust in primary 4 which may have already reached the down pipe.
multiply the effect in an engine typically operating in the range of 1k-6k rpms, u have pretty chaotic situation there.
your explaination renders me helpless with this argument. cause it is true. in theory.
but... the cylinders dont fire off @ the same time, producing the same amount of exhaust, all at the same rate though. as far as timing is concern
if anything would render the efficiency of the whole engine more then anything esle in terms of the paths of the exhaust fumes after it exits the cylinders. it would have to be the piping diameter of the exhaust manifold, bents of the manifold.. and the amount of back pressure.. ....
i still stand by my opinon.... you did brought up a good point in a perfect situation though...
so my response to Twin turbo's post as to whether unequal exhaust manifolds are bad? .. in theory yes... in real application .. no...
and my layman respone to this would be.. if the unequal exhaust manifolds results in the EJ running @ a lower efficiency rate, i really dont think the engineers would have it on in the first place.. -
heng,
not all wrc cars sound the same though.. similar maybe but theres still a difference.. nvm... i wouldnt be able to discuss this with you till i can a chance to hear the different WRCs @ idleing... you might be right..
if only i had went down to the Corona Rally Mexico this yr.......