13 replies to this topic

[biga064]

Hi Im trying to find out whether a good set of extractors are better than the xu1 style headers i run on my engine . I ve been told that if i want the engine to reach its full potential , i need extractors. Any help from ones that know or anyone who has done some dyno testing would be much appreciated. Thanks Biga064

[Heath]

Shoulda put this in the Engine section rather than here by the way.

Anyway, not all extractors are the same - equal or unequal length runners, different diameters of primaries, secondaries, collector, different transitions etc but put simply, yes extractors will go a lot further than XU-1 headers.

Even mediocre ones will probably flow better and have a useful scavenging effect, assuming your motor is actually hot enough to need them. If it's a very mild motor, the XU-1 headers are probably advantageous over some extractors that are suited to a car that's supposed to sit at 6,000rpm on a speedway track

Edited by Heath, 13 September 2009 - 06:37 PM.

[rodomo]

A bit of chit-chat in this thread:
http://www.gmh-toran...=&hl=extracyors v headers&fromsearch=1

And you can troll through this search result:
http://www.gmh-toran...re&fromsearch=1

[Struggler]

I just dug up that old article in Street Machine from years ago.....

The XU1 manifolds were worth 9HP and 42 ft/lbs over the handmade extractors.

I could scan the article if your keen.

[Heath]

Am I missing something? Struggler, you are the last person I would have expected to rehash some specs from a Street Machine article as advice on a motor that you're not familiar with. Surely there is more to this topic that you could shed light on

[Struggler]

I would imagine there was something not right with the original extractors rather than the manifolds were that much superior.

I can tell you that I have seen some unbelieveable gains and losses on engine dynos and at the drag strip changing exhaust. Simple collector extensions on 4:1 pipes that pick up 90 ft/lbs on a 550Hp engine, almost 4 tenths ET gain by reducing collector diameter 1/4", the list goes on.
The 42 ft/lb increase is not that hard to imagine if the original pipes didn't have enough collector length.

The test only involved the original extractors and the manifolds (so there could well be something out there even better) but there are some lessons to be learnt by closely reading the article.

 XU1.jpg   444.58K   45 downloads

[Heath]

The test only involved the original extractors and the manifolds (so there could well be something out there even better) but there are some lessons to be learnt by closely reading the article.

Interesting read, especially about that paint on the pipe thing actually working so effectively!

But what pipes did it have on it in the first place? It really doesn't give any detail about that

[Struggler]

Guys, please be careful with this paint burning off myth.

Paint any pipe and the paint will burn off to a point about 4" from the open end. Cut the pipe and repaint, you end up cutting another 4" off. It doesn't really work. I have had most success with using 18" or 500mm (depending on what measure I have at the time)of pipe from the point where the cylinders merge in the collector.

I was once at Sams Performance in Sydney with a VN headed 355 on the engine dyno when Mark Arblaster walked in. "Try the paint burn collector length trick" he calls out, sure enough we end up cutting 4" off my 18" collector extensions. Lost 15 ft/lbs at 4000 rpm but maintained the same HP. Turned around and he was gone !!

Edited by Struggler, 14 September 2009 - 08:50 PM.

[Heath]

There are calculations availible for working out all kinds of exhaust dimensions that work well

[Dr Terry]

To answer the original question, unless you're building a race car, it's hard to go pass the cast iron headers.

Harry Firth used them for 3 Bathursts (including the 1972 win) before finding a set of extractors that worked as well across the rev range as the factory headers.

Sure, if your after peak power or peak torque any set a bent pipes will work in some fashion, but the question is, is it usable.

Dr Terry