bubblegoose Posted June 2, 2009 Share Posted June 2, 2009 to stop the spamming of kpr's dissusion of awsomeness me tinks zorst technologies should be discussed here disscuss 4-1 Vs. 4-2-1 GO! Quote Link to comment Share on other sites More sharing options...
KKtrips Posted June 2, 2009 Share Posted June 2, 2009 I prefer 4 into 1 - looks much tougher then 4-2-1 no idea which is better for power - but I reckon 4 into 1 allows for much longer primaries which theoretically means moar torque... Quote Link to comment Share on other sites More sharing options...
bubblegoose Posted June 2, 2009 Author Share Posted June 2, 2009 ive been looking at 15inch primary's with 26 inch secondary's but then get told that 4-2-1 is no good for anything other than a mildly pimped nana car and 4-1 is god i hate oppinions Quote Link to comment Share on other sites More sharing options...
mikuni Posted June 2, 2009 Share Posted June 2, 2009 ive been looking at 15inch primary's with 26 inch secondary's Sorry what is the engine? Like anything in the NA tuning world there seem to be a lot of different opinions. I always heard that 4-1 was for peak hp at max rpm and 4-2-1 was more mid-range torque but then I have seen a lot of race cars tuned for max hp having 4-2-1. There are various calculations for extractors too, some are very specific where others say that providing each primary is atleast the capacity of one cylinder then you should be alright. I think its important to keep the velocity up in the primary also, so you should keep size to a minimum, but from what I have read once its collected you can pretty much do what you want, providing it doesn't obstruct flow. Here are the extractors that are apparently perfect for a race tuned C20XE Opel 2L engine making 250-290bhp. "4.2.1 with 1 7/8" primary, 2 1.8" secondary 2 ½" Outlet. Designed to give the ultimate in torque & BHP" They seem to imply that 4-1 is only a compromise. The BTCC Supertouring cars that made over 300bhp from the same 2L engine also ran a 4-2-1 of the same (or very similar) dimensions, however I have seen one from a BTCC Honda Accord and it was enormous, with runners probably 2 metres long! Quote Link to comment Share on other sites More sharing options...
Brock-Lee Posted June 2, 2009 Share Posted June 2, 2009 I read somthing about how collectors actually suck. and the best results were gained by straight dumping the four primary pies into the biggest dia pipe you could fit under the car. discourse in 3,2,1,go! Quote Link to comment Share on other sites More sharing options...
BobbyBreeze Posted June 2, 2009 Share Posted June 2, 2009 I read somthing about how collectors actually suck. and the best results were gained by straight dumping the four primary pies into the biggest dia pipe you could fit under the car. Yuh, that was me. Philip H. Smiths book 'Scientific design of exhaust and intake systems' outlines this. He basically says for best results, all primary's should collect into a 'exhaust box' of sufficient diameter and volume (outlines it in the book). He then says if you don't have space for this (and says most cars etc don't), then use a merge collector and talks about how the angle is important. Quote Link to comment Share on other sites More sharing options...
Testament Posted June 2, 2009 Share Posted June 2, 2009 I think if you look at most professional race car series and you will probably find some kind of 4-2-1 BUT if you look at them, the primarys will be about as long as you might see on "regular" 4-1 system. basically the thing is if you are tuning for the 1st harmonic you need rather long pipes e.g. 5000rpm is nearly 1m. thats just tuning the cylinders as individual entities - if you want one cylinders pressure wave to help scavenge another cylinder things get a couple of orders of magnitude more complicated because while things will be better at one rpm they will be worse at another. Part of the reason it's often said 4-2-1 is better for mid range is that it is alot easier to fit in a effectively longer pipe with short primarys and longer secondarys. fitting in four long primarys takes up more space. Quote Link to comment Share on other sites More sharing options...
toyabusa Posted June 2, 2009 Share Posted June 2, 2009 check out the size being not much bigger after the collector than the primarys themselves and also the wicked merge angle Quote Link to comment Share on other sites More sharing options...
kpr Posted June 2, 2009 Share Posted June 2, 2009 keen to try make some 4-2-1's again. seems to be what everyones doing at the moment. the old 4-2-1's i had on the kp. actually worked pretty good. but were tuned for wrong rpm for my cams and looked shit have read a little about stepped headers . spose to be good for high rpm use. must be some drawbacks though as dont see them used alot. n/a is pretty tricky, pretty much gotta try stuff and see what works Quote Link to comment Share on other sites More sharing options...
Testament Posted June 2, 2009 Share Posted June 2, 2009 from kpr's discussion thread yeh same deal here, thats why i was running a 2" system to start with. but smaller exhaust for better torque, velocity scavaging etc, seems to be bs in my case at least. just been comparing the tune we used on the dyno with 2" exhaust, to the current tune. ive added 45% more fuel at 5000rpm! tapers down to not much at high rpm and low rpm, but have added fuel everywhere. have done other mods as well, but exhaust changes are responsible for most gains. huge midrange gain from changing to the bigger exhaust. pitty it scrapes like shit on everything as it is, otherwise i'd be tempted to try bigger. it's not so much the diameter of the tailpipe as the flow, e.g. you can have a big pipe with a shit muffler and it may work the same as a straight smaller pipe. But if your not actually "tuning" the tailpipe length then going on the larger side probably wont lose you anything. Although remember a 3" flows alot more than a 2.5" since area goes up by the square of diameter - so much bigger increase than 2.25" to 2.5" Quote Link to comment Share on other sites More sharing options...
kpr Posted June 2, 2009 Share Posted June 2, 2009 yeh pity there's compromise in a street car, with those pesky mufflers and must exit here rules. / ears bleeding. im saying from what ive found, after it has exited the extractors and the correct length and size collector. going huge from there on doesn't really matter, too small does. so best to go too big rather than too small. making it quiet and flow well is a cunt pretty much. Quote Link to comment Share on other sites More sharing options...
bubblegoose Posted June 2, 2009 Author Share Posted June 2, 2009 check out the size being not much bigger after the collector than the primarys themselves and also the wicked merge angle noticed when i was working on bikes that most merge angles on stock and performance upgrades are all pretty sharp, they all seem you use 421 aswell but with primarys much longer than the seondarys (guessung for the high rpms. the seconds were also almost as small (diameter) if not the same as the primes and the end pipe was still not much bigger eg. 42mm-45mm-50mm (cant argue with 200hp per liter now can you) Quote Link to comment Share on other sites More sharing options...
bubblegoose Posted June 2, 2009 Author Share Posted June 2, 2009 Sorry what is the engine? 4g63 bit of work 41mm primes-44mm seconds-57mm Quote Link to comment Share on other sites More sharing options...
kpr Posted June 2, 2009 Share Posted June 2, 2009 helmholtz is the pressure waves your tuning the length of the pipes to. its used alot in intake tuning helmholtz resonator, generally the first straight through muffler is helmholtz resonator design. google it, its pretty techo shit beyond what i can explain. high rpm stuff seems to use sharper collector angles, Quote Link to comment Share on other sites More sharing options...
bubblegoose Posted June 2, 2009 Author Share Posted June 2, 2009 true dat remember a custom pipe set up on a 245rwhp (@somewhere near 10krpm) zx10 the collectors were pretty much at a 120' loooong primary's though Quote Link to comment Share on other sites More sharing options...
Roman Posted June 2, 2009 Share Posted June 2, 2009 I cant find the page where it mentions it now, but the TODA racing website somewhere mentions that although a 4-1 setup gives marginally more top end, with a good 4-2-1 they were losing say... 1% top end but gaining crap loads of mid range and low end power. They show pipe diameters etc for Altezza 3S extractors here: http://www.toda-racing.co.jp/en/product ... i/3sg.html Presumably inside diameter for piping. Quote Link to comment Share on other sites More sharing options...
Truenotch Posted June 2, 2009 Share Posted June 2, 2009 Those toda ones look nice! $1700 + shipping..... My pipes are quite beefy, they're a big long 4-2-1. The primaries extend into the tunnel, then collect into 2 secondaries that are about 500mm long before being collected into 3" and finally down to 2.5". I'm getting keen to go back to a 3" exhaust just as an an experiment. They would need a bit of work to be ideal, but are good enough for now (and will stay for quite a while). Quote Link to comment Share on other sites More sharing options...
Truenotch Posted June 2, 2009 Share Posted June 2, 2009 Exhaust:The real value in extractor type exhaust manifolds only comes when camshafts & valve springs are changed so that peak torque occurs at higher revs. A simple design formula that appears to work OK is:- Primary pipe length in inches =((850 x ED)/rpm)-3. Where RPM is the “tuning” revs, typically being the max torque engine revs & ED is (180 + exhaust cam opening point BBDC). On a fast road engine with a peak torque point of say 3500rpm, this works out to be 134cm (53”), whilst for a race only engine at 5500rpm, it is 91cm (36”) We have always found that 4:1 systems work best. The 4:1 device is commonly called a merge collector & these can be purchased pre-made. It impossible to make a 4:1 on a road going MR2 with such long pipes, so you need to compromise with a 4:2:1 system, & get the total of the primary plus secondary pipes to be this length. ncreased size “cat back” exhaust systems continue to be widely used however the Catalytic convertor proves to be a major restriction. Others have shown that the total pressure drop in the system needs to be no more than about 14kpa (2 psi). To achieve this on our racer we had to remove the cat entirely, use a 80mm (3.25”) main pipe & a straight thru (but still efficient) muffler. Interesting ideas there, and brings back-pressure into play. Quote Link to comment Share on other sites More sharing options...
Roman Posted June 2, 2009 Share Posted June 2, 2009 I know where that's from, I'd read that 'modifying the 3S' guide with a grain of salt tbh. Quote Link to comment Share on other sites More sharing options...
Truenotch Posted June 3, 2009 Share Posted June 3, 2009 I know where that's from, I'd read that 'modifying the 3S' guide with a grain of salt tbh. Yeah I agree with you there, posted it as a discussion point more than anything. Quote Link to comment Share on other sites More sharing options...
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