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Re: JTS v hurricane v Hi-tec Headers

Subject: Re: JTS v hurricane v Hi-tec Headers
by jmac on 2009/1/27 7:52:13

1000coupe - I was talking tri-ys on v8s where eac 'side' has 4>2>1 (which is 3 Ys - 1 for each of the primaries to secondary pipe, then a final one (per side) from the secondary to the main collector. I wasn't suggesting they are popular on 4s, just aiming at a quick once over as far as why they exist at all. There are indeed tri-ys for 6s - 6 into 2 into 1 - but I'd suggest they are done to make for less total piping/space taken up, 6>1 still work better.Sorry if my post is confusing - I'm far from an expert, but my biggest drama is I tend to understand stuff a little bit better than I can effectively/clearly discuss it!

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opkey dokes - in that one the final pipe out of the collector might be tucked inside the 4-1 flange. Here is a pic (it was done for another forum some time back so please ignore the fact there are only 3 primaries - it was done to show an inline 6 with 6-2-1 pipes. The 'blue' area shows where it would trap heaps of exhaust flow. On some I've had (one for a hemi 6 in fact) the final pipe tucked a good 1.5 inches inside the flange, making a big obstruction to flow. In your example, nobody could say without cutting it off. If you cut carefully around the weld you could pop the pipe out without cutting all the way through, then flare that same pipe and re-attatch.

The second picture is as referenced in the first post - at the top is a 'typical' extractor - where the flange obstructs the port exit ever so slightly. The second is 'port matched' which is good, but the bottom one is opened a touch further to create an anti-reversion step (if the exhaust tried to go back in the port, it'd hit that step/edge and less would get in there). The green on that final picture is to show that in some cases, you might have to add weld (mig is good if you have access, I've actually done it by oxy a couple of times, because that is what I had) on the outside meeting point of flange and primary pipe.

Last thing I'll show - is photos of some extractors a mate got for a hemi 6. The port 'holes' in the flanges weren't cut straight - so when it looked 'lined up' on the outside, it wasn't on the ports. In the worst case, it blocked more than 1/4 of the port on the worst one. That had to be welded up to buggery to get it to line up - I had to actually add steel to the flange because I had to grind out past the end of the flange to line them up!! On which note, they were coated (they weren't manufactured by) jet-hot - a great coating. but since they had to be modified, that coating had to go for the welding to be done. I'd _strongly_ suggest sourcing extractors as is, then ensuring they fit optimally (or making them do so) and then and only then get them coated if you wish to.

The extractors were fitted originally at an exhaust place, and when it started to leak, we took them off to look, and you can see by the carbon deposits how far off they were. In the last pics, you can see that the entire left wall of the flange is actually new material. Given the amount I had to add to them, I thought for sure they wouldn't last, but they ended up on the car for a fair amount of time (approx 12 months) and didn't crack (he ended up upgrading to new pipes with larger primaries anyway)

The only other thing that comes to mind - Although I discussed the rpm sweet spot of headers vs their primary pipe diameter, it should be noted that pretty much _any_ extractors (the aforementioned issues notwithstanding) will provide a power boost - simply because they (combined with a freer flowing exhaust from there back) reduce exhaust backpressure vs the factory cast iron style stock (the GX ones, that I've only seen pics of, are likely a different story) and less heat under the carb - all of which boost power. What it's about however, is getting hold of all the potential gains - the drop in backpressure/heat _as well as_ the gains from optimal pipe sizing.