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the only super well designed equal length runner manifold I have ever seen come on Greddy turbo kits (I.e. the tdo5H-18G kit for the new SI). From what I remember, the manifold looked cast, but it actually had a channel that went OVER the hroizontal tube section that made cyl's 2 and 3 equal length of 1 and 4, and they all emptied into the turbocharger. it was about the size of hrc's manifold, or just a little bit bigger. tubular manifolds are more prone to cracking under extreme temps. they usu. have to hold up a turbocharger, and usu, don't have any support brackets of their own, and that hurries the crackign process along pretty quick. I think that that is the reason the front manifold on my vr-4 is tubular, and the rear is cast( the rear is in a HOLE). the front also has good sized brackets on the turbo assembly (manifold, turbo, o2 housing), where as the rear's extra support isn't as extensive (If I rememebr correctly, only one extra bracket, with 1 bolt). I believe all the major racers use tubular manifolds is because 1. most of them can repair the cracks that they get for little of nothing, and don't mind fixing them, 2. equal-length runners do help performance a little.....it is different when compairing this to headers....I can explain that in the next paragraph, 3. casting your own custom manifold is a LOT more expensive than bending header pipe and welding it together. 4. they usu. invest in enough header wrap, and ceramic coating and heat shields that they keep a lot of heat in (sometimes at the expense of the metal's life.....but that is up for discussion at a different time).
when you talk about 4 into 2 into 1 headers and 4 into 1 headers and turbocharging, it is really 2 different concepts (now, I am not the "guru" of flow technology, but these are just a few things that I have learned over the years). when you have a 4 into 2 into 1 header, that design usu. helps mid range and torque, whereas 4 into 1 usu. only helps top end......do you know why? from what I understand you have to think of the whole process in slow motion. number 1 cylinder fires exhaust gas out, and then #3 (I am pulling random numbers in this example. don't reem me if I ge tthe firin order wrong). then number 2 then number 4. when 1 fires, it shoots out exhaust, and actually pulls a little bit of vaccuum from the other cylinders it is connected to in the header or manifold (in this case #3), and then #3 fires. the exhaust gas doesn't have to fight a lot of backpressure because of the vaccuum caused by #1 firing. This helps flow, and increases torque. Since it is just a LITTLE vaccuum caused by this, it really doesn't benefit that much in a standard manifold because of the excess space in the wrong directions (not in the direction of flow I mean). 4 into 1 headers make more top end power because they have less to restrict them (no joins or funky bends). they don't usu. make as much mid range power as the 4-2-1 because of the first theory I spouted. when you have a turbocharger in the way, there is usu. too much backpressure in the manifold to apply the vaccuum theory (that's where turbo-spec cams can help.......I will explain that at a later time as well). the faster the exhaust gasses get past the turbo, the less pressure you have, and then the first rule begins to apply again, but that only last for a short time (usu. on top end, higher rps, where the wastegate is open). at this time, you really just want the most flow anyway, so running all kinds of funky pipe aren't to your advantage (just gives more time for the manifold to radiate heat). plus the shorter the distange from the head to the turbo (flow wise) the easier it is to pressurize the exhaust manifold, and generally, the quicker your turbo response will be (i.e. less lag).
now, the new edge racing manifold doesn't look too shabby. it actually looks pretty good, but I would just make sure that those welds are SUPER GOOD. beleive me, there have been SEVERAL instances of manifolds cracking because they just weren't strong enough, and unfortunately, the only way people find out stuff like that is either with long drawn out physics equations, or experience. I personally like the hrc kit because they test all their stuff for LONG periods of time before they sell it (beleive me, I had been itching, calling, and scratching for a LONG time before they released the stage 5 to the public). I hope to end up with the ultimate street turbo setup for my car, and I think I am on the right track so far. now If I could just get it to run..........
bring it on............
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So if anything it would get rid of heat better because there is more flow in the manifold.
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