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Location:
Sydney
Registered:
June 2004
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mandrel bend or standard bend exhaust
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Mon, 26 July 2004 06:42
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im trying to find out if i should go mandrel or not and want to know what the real benefits are?
for the price difference between standard bend and madrel bend is so large i would like to know what is the actual power gain?
is it really worth the extra money?
if it is worth it, should i do mandrel all the way or just CAT back?
PLEASE people i dont want answers like 'it looks good', 'sounds good', 'yeah you get 100HP extra' (unless its true)
i just want good honest answers so i can make up my mind on what to get done
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Registered:
February 2003
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Re: mandrel bend or standard bend exhaust
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Mon, 26 July 2004 06:56
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bang for your buck - definately just go standard bends.
When I got my exhaust done, I went to a few places and they didn't even recommend manrel bending. Only a select few places have mandrel bending machines, so i'd imagine it'd cost u an arm and a leg if you wanted this done.
I'd suggest to just get standard press bends and go from headers back
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Location:
Terrigal
Registered:
May 2002
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Re: mandrel bend or standard bend exhaust
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Mon, 26 July 2004 07:03
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Hmm.. i gotta disagree with you there mate, it does depend on what you are after and like you say bang for buck..
Though I reckon for a turbo car a mandrel bent exhaust is VERY important! and i'd never run anything else.
Thats just my opinion though..
If you want press bent exhaust, stick with a NA car 
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Location:
Terrigal
Registered:
May 2002
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Re: mandrel bend or standard bend exhaust
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Mon, 26 July 2004 07:05
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Sorry should have put why..
Mandrel will help exhaust gas flow a lot as press bent each bend is restricted. Mandrel there is no restrictions of pipe diameter in the bend.
So your turbo will spool up quicker and produce more boost. Free power? 
Ultimately you want a mandrel exhaust from the turbo back, but if you cant afford that right away just get a 3" cat and 3" mandrel exhaust from there back. Then later get the dump pipe done.
Cheers
Joel
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Location:
Brisbane
Registered:
May 2002
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Re: mandrel bend or standard bend exhaust
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Mon, 26 July 2004 07:17
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Actually I'd get a good mandrel-bent dump pipe and cat BEFORE the cat-back exhaust every time. That's what makes all the difference.
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I Supported Toymods
Location:
Glenmore Park, NSW
Registered:
March 2004
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Re: mandrel bend or standard bend exhaust
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Mon, 26 July 2004 07:18
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yeah its a bit like what turboRA28 sez.
problem with say a 3" press bend vs a 3" mandrel bend is any where the press system makes a turn / bend the diameter of the piping lessens ie its prob for eg 2.5" around the bends due to the pipe being 'pressed' as such.
where as with manderel bends no diameter is lost on the bends.
and then going by 'a chain is only as strong as its weakest link' whats the point in a 3" press bent system when its restricted to 2.5" on the bends?
some people say its a huge diff others say you cant even notice the diff. Me personally ive yet to get an exhaust system on any of my cars so all i know is the theory behind it all.
Hope this helps.
Cheers
Nathan
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Location:
Terrigal
Registered:
May 2002
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Re: mandrel bend or standard bend exhaust
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Mon, 26 July 2004 07:18
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Yeah true.. I did mine arse-end-about 
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Location:
Sydney
Registered:
June 2004
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Re: mandrel bend or standard bend exhaust
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Mon, 26 July 2004 07:20
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cool thanks for that...
now i know bout the free flow of gases and how that helps to spool turbo and stuff like that but would it increase boost? down the 1/4 if i did 12s on standard bend then what theoretically would i get with mandrel? if its 11.9 then screw that but if its .5" lower WELL THATS DIFFERENT...
anyine else got any idea/opinions
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I supported Toymods
Location:
sydney.au
Registered:
August 2002
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I Supported Toymods
Location:
Glenmore Park, NSW
Registered:
March 2004
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Re: mandrel bend or standard bend exhaust
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Mon, 26 July 2004 07:58
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i think its more a case of getting to max set bost pressure sooner rather than making more boost. ?
Nathan
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Location:
sunny coast, qld
Registered:
October 2002
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Re: mandrel bend or standard bend exhaust
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Mon, 26 July 2004 08:05
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so on the topic of "the weakest link"
could you say that a 3" press bent exhaust with the bends going down to 2.5" would be equivalent to a 2.5" mandrel bent exhaust?
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I Supported Toymods
Location:
Glenmore Park, NSW
Registered:
March 2004
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Re: mandrel bend or standard bend exhaust
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Mon, 26 July 2004 08:14
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i wouldnt say yes because i have no testing proof on this.
but i do think if you ran them both on say a flow bench to see which had less restrictions id be inclined to say the manderel system would win hands down everytime.
think of it this way ... whats easier?
pushing a 3" sponge thru a 2.5" hole - bit of force required but it gets there
or pushing a 3" sponge through a 3" hole - effortless.
thats the way i see it... gas makes it out qwiker with less restrictions.
Cheers
Nathan
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Location:
Baulko Hillo
Registered:
April 2004
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Re: mandrel bend or standard bend exhaust
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Mon, 26 July 2004 08:19
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If it's turbo, spend the money on a nice 3" mandrel system dude. Every turbo car I have had (except the Skyline) had 3" mandrel piping from the turbo back and it's definately what you want. Boost will rise as there is less restriction. Yes, I know, the wastegate should not let it etc.... But it does.
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Location:
Brisbane
Registered:
May 2002
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Re: mandrel bend or standard bend exhaust
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Mon, 26 July 2004 12:32
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When it comes to NA cars, bigger is better (the same as a turbo) but the law of diminishing returns kicks in much earlier. In other words, a really big exhaust is rarely beneficial unless it's a big engine (like 5.0 litres or more). For an atmo 4A, any more than 2.5" will do nothing except make more noise!
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I supported Toymods
Location:
sydney.au
Registered:
August 2002
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Re: mandrel bend or standard bend exhaust
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Mon, 26 July 2004 12:34
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so the downpipe doesnt matter if its press bent?
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Location:
Brisbane
Registered:
May 2002
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Re: mandrel bend or standard bend exhaust
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Mon, 26 July 2004 13:42
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Probably not a huge amount, but that part of the exhaust is close to the engine and thus flow capacity is much more important than the rest of the exhaust. Pre-bent mandrel tubes are not expensive so there's no reason you can't have a mandrel-bent downpipe for not much more than the cost of a crush-bent one.
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Location:
Kita-Ku, Sapporo, Japan
Registered:
January 2003
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Re: mandrel bend or standard bend exhaust
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Mon, 26 July 2004 14:03
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i would use mandrel bends if i needed a bend greater than about 45 degrees, or if i needed a tighter radius, to make shit fit, than press bending allowed.
the mandrel bends i used for my extractors had a radius of about 15-20cm, whereas the press bends were more like 30cm radius.
if a 180 degree press bend is about $10-15... what are you worried about. (unless you are making V8 headers )
Cya, Stewart
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Location:
Lost in the K hole
Registered:
May 2002
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Re: mandrel bend or standard bend exhaust
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Mon, 26 July 2004 14:08
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im a big believer in the following:
"an exhaust is only as good as its first 5 feet"
after that - who gives a fuq? spend your money on an awesome flange and dump +- screemer pipe, drop it through a high quality cat, and from there? meh...
i think youll find what becomes an issue is the fact that most places dont have dies to press bend anything over 2.5" anyway, so if you want a 3" system, youve really go no choice.
all becomes a bit academic doesnt it
cheers
ed
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Location:
Sydney
Registered:
June 2004
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Re: mandrel bend or standard bend exhaust
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Mon, 26 July 2004 15:52
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well the car is currently mandrel all the way to the diff section where it goes to press... so basically mandrell from turbo down, through CAT, couple turns to make 3" fit all mandrel and then at diff it is press through to straight through muffler and out to tip
but that is a normal exhaust... i am really asking so when i go stainless i know what i should do... so ed you recon i should copy the exact same system for my stainless...  need more thinking... i know ill find out exact price difference... if its a $100-200 more than meh do it but more than that gotta think cause i could buy a turbo for that much OR complete gasket rebuild kit OR.....
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Location:
Melb
Registered:
June 2004
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Re: mandrel bend or standard bend exhaust
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Tue, 27 July 2004 02:27
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Was reading a book on modern engine tuning recently that discussed this at length. They conducted a series of tests with different cars, na and turbo- hot and stock running different exh setups.
Findings, in summary, were that running a mandrel bent system showed no more than (from memory) 0.2- 0.4 percent power increase. Even on a fairly wild Sierra Cosworth!
Further to this, they looked at running larger diameter piping (relative to the rest of the system) for the last few feet of the exh and found that it made no difference to the flow at all.
I would have to strongly agree with some of the points made about the first few feet of the exh being the most important, there is substantial data and theory to support this.
It really boils down to what you want for your car, if you have the cash and are building a wild machine that you want to wring everything out of- then sure it is common sense that a press bent system will have slightly more restrictions. For a car not so pushed to the limit, i would suggest you may not notice it. It is probably more important to get an exh that is well made, had good bends and joints that flow well. Sorry about the long post, thats my five bucks worth. Tom
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I Supported Toymods
Location:
Glenmore Park, NSW
Registered:
March 2004
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Re: mandrel bend or standard bend exhaust
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Tue, 27 July 2004 06:37
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here here.
what he said ^^^
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Location:
south east - melbourne
Registered:
March 2004
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Re: mandrel bend or standard bend exhaust
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Tue, 27 July 2004 07:03
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ok hile were at it , will a 2.5 inch mandrel system work well with a 3 inch cat ,
assuming that the flages at the cat can be widened to fit the 3 inch diameter wont it flow better cause the cat wont be restrictive cause its a 3 inch and the rest of the system 2.5
what i saying is ,with the restriction in the cat the flow will drop to equal somewhat which a 2.5 pipe can flow anyway
any ideas
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Location:
Kita-Ku, Sapporo, Japan
Registered:
January 2003
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Re: mandrel bend or standard bend exhaust
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Tue, 27 July 2004 08:00
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it's not just about size, but also pipe length.
the cat is the first major restriction in a modern exhaust, and being a fairly solid item, it reflects the exhaust pulse differently than does the join at a collector, or from an open pipe, so if you wanna get all techanical abotu it....
anyways, same as for intakes, an exhaust is only flowing it's maximum amount of gas at WOT and highest rpm.
with the cossie, its hard to say how much difference the bends would make if the exhaust design is adequate anyway...
to be safe, have a look at the decrease in diameter of the press bends (and if you want, you can calculate the 'effective length and effective restriction) and compare to the mandrel bends, and then decide from there..
bugger it, just use mandrel none of this "pennypinchin" 
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I Supported Toymods
Location:
Glenmore Park, NSW
Registered:
March 2004
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Re: mandrel bend or standard bend exhaust
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Tue, 27 July 2004 08:07
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cant see any probs there. 3" cat on a 2.5" system should have no more restriction that a 2.5" cat on a 2.5" system.
like running a 500hp turbo at 400hp as aposed to a 400hp turbo running at 400hp. 400 is 400.
thats just an illustration.
Nathan
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