sprint exhaust diameter

[iandollysprint]

Just spoken to rimmers who were very helpful and informed me that the sports exhaust for a sprint is 50mm outside diameter (approx). I have a complete standard system which I have measured at 48mm.<br>
<br>
Surely 50mm isn't big enough if the engine is to be uprated. My little black book on tuning 4 strokes (can't remember authur) talks about 2.25 inch minimum for power greater than 140 bhp.<br>
<br>
Am I missing something here? Sprintparts do a primary pipe for £100 plus delivery VAT etc which is 2.25 inch (57mm). Seems a waste to stick a 50mm system on the back end of it.<br>
<br>
What size exhaust do I need if aiming for a 160-170 bhp engine.<br>
<br>
Thanks<br>
<br>
Ian

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[davepoth]

When you look at the labyrinthine route the standard system takes out of the car, running a much straighter pipe will provide much better flow even without having a bigger bore exhaust. I'm sure some of the other guys with better engines will chime in, but the 2" system I had built for my mildly warm engine has virtually no back pressure in it at all (farts like a morris minor on the overrun, but much louder <!--EZCODE EMOTICON START :D --><img src=http://www.ezboard.com/images/emoticons/happy.gif ALT=":D"><!--EZCODE EMOTICON END--> ) so I'm thinking anything more is starting to look like overkill. <br>
<br>
PS. The S-bend Janspeed system I had on the car before (which I think was used on the works rally cars) was 2" throughout.

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[MaddMart]

My track Sprint is 170 bhp at the flywheel & I'm running the standard s/s sports exhaust. It seems to run very well, but without trying a bigger bore exhaust I couldn't say if that would make an improvement or not. Not sure what size Scott's is using.

<p>Martin<br>
<br>
<!--EZCODE LINK START--><a href="http://www.dolomitesprint.com/" target="top">www.dolomitesprint.com</a><!--EZCODE LINK END--></p><i></i>

[Carsreunited]

Rimmer brothers standard sports stainless steel down pipe, in to 2" custom chrome thingy me bob with side exit. Mines 155 rwbhp.<br>
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<br>
<br>
<br>
<br>


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[davepoth]

I think Daz (ALG1K) uses 3" bore, but his is a bit of a special case...

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[Jod Clark]

Careful, not too wide or you'll lose the gas velocity.<br>
<br>
Jod

<p><!--EZCODE IMAGE START--><img src="http://www.towingandleisure.co.uk/images/bash.gif" style="border:0;"/><!--EZCODE IMAGE END--></p><i></i>

[MaddMart]

Darren doesn't use a Sprint engine (or any engine for that matter) that produces the same sort of power, so you can't really make any comparisons

<p>Martin<br>
<br>
<!--EZCODE LINK START--><a href="http://www.dolomitesprint.com/" target="top">www.dolomitesprint.com</a><!--EZCODE LINK END--></p><i></i>

[davepoth]

'tis a good point. Darren runs an 800hp+ sierra cosworth engine in his dolly, making such comparisons a bit pointless. Consider me suitably chastised. <!--EZCODE EMOTICON START :o --><img src=http://www.ezboard.com/images/emoticons/embarassed.gif ALT=":o"><!--EZCODE EMOTICON END--> <br>
<br>
<br>
<!--EZCODE EMOTICON START :D --><img src=http://www.ezboard.com/images/emoticons/happy.gif ALT=":D"><!--EZCODE EMOTICON END-->

<p></p><i></i>

[iandollysprint]

Thanks to you all<br>
<br>
2 inch sports system it is then<br>
<br>
Ian

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[dollyboy]

theres not much point in having anything with a bigger ID than the outlet of the manifold or downpipe. as mr poth says, the straighter the better and as jod says if the pipe's too wide you lose the speed of the exiting gas which is also counter-productive.<br>
<br>
making the zorst less restrictive is beneficial to a point but the bigger and more free-flowing the zorst is the more juice you're gona guzzle, and you'll only really notice the difference mid range, and have to aim higher up the rev range to get the benefit from it.<br>
<br>
2.25" is whats going on mine, but I'm expecting 180hp+ running fast road cam and 45 webers. im sticking with the cast turd and the zorst will be custom made, and will go under the axle rather than over it for more 'straightness'.<br>
<br>
theres also no point in getting all excited about .25", the goal in mine which will be basically a road car is as much about making sound evil as gaining a hp or two, if it sets off the odd beemer alarm so much the better! <!--EZCODE EMOTICON START :evil --><img src=http://www.ezboard.com/images/emoticons/devil.gif ALT=":evil"><!--EZCODE EMOTICON END--> <!--EZCODE EMOTICON START :lol --><img src=http://www.ezboard.com/images/emoticons/laugh.gif ALT=":lol"><!--EZCODE EMOTICON END--> <br>
<br>
happy zorsting!<br>
<br>
<!--EZCODE EMOTICON START :D --><img src=http://www.ezboard.com/images/emoticons/happy.gif ALT=":D"><!--EZCODE EMOTICON END-->

<p>project orange - slow progress<br>
project black - coming on, could be sold...<br>
project white - pimp my tolly, next year!</p><i></i>

[davepoth]

One thing to bear in mind, and this is especially pertinent if you have lowered the suspension on your sprint, is that the boot floor is not usually that good at taking the weight of a sports exhaust backbox on the single bolt that's usually used. With lowered suspension you'll end up smacking the pipe on speedbumps etc, and in my case, and up having the bolt come through the floor of the boot. Twice. <!--EZCODE EMOTICON START :eek --><img src=http://www.ezboard.com/images/emoticons/eek.gif ALT=":eek"><!--EZCODE EMOTICON END--> <br>
<br>
Get a steel plate welded in on top to reinforce the area, just to play it safe.

<p></p><i></i>

[MaddMart]

So Kev, will the fast road cam give another 10bhp+ over an STR91 (mine), or are you going to be blue printing your rebuild as well?

<p>Martin<br>
<br>
<!--EZCODE LINK START--><a href="http://www.dolomitesprint.com/" target="top">www.dolomitesprint.com</a><!--EZCODE LINK END--></p><i></i>

[dollyboy]

you're feeling playful tonight mr mart?! <!--EZCODE EMOTICON START :lol --><img src=http://www.ezboard.com/images/emoticons/laugh.gif ALT=":lol"><!--EZCODE EMOTICON END--> <br>
<br>
maybe i'll be disappointed then, who knows...<br>
<br>
<!--EZCODE EMOTICON START :lol --><img src=http://www.ezboard.com/images/emoticons/laugh.gif ALT=":lol"><!--EZCODE EMOTICON END-->

<p>project orange - slow progress<br>
project black - coming on, could be sold...<br>
project white - pimp my tolly, next year!</p><i></i>

[Carsreunited]

Kevs engine is from the same place as mine (coventry engine services or something similar) except his doesn't have forged pistons or 48's.<br>
<br>
We need to get into the habit of quoting rwbhp as well if we can. One thing I've learnt over the past couple of years is that there are lies, damn lies, and flywheel corrected figures!<br>
<br>
Ken Clarke quotes 193 rwbhp for his engine, 155 rwbhp for mine. Which explains perfectly why his car is 3 secs a lap faster around Brands Hatch than mine! Nothing to do with me being a pants driver!!<br>
<br>
<br>
<br>
<br>
<br>


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[MaddMart]

Kev, it was a serious question. I was just after trying to delve into the World-of-Kev to see what you were up to? <!--EZCODE EMOTICON START :D --><img src=http://www.ezboard.com/images/emoticons/happy.gif ALT=":D"><!--EZCODE EMOTICON END--> <!--EZCODE EMOTICON START ;) --><img src=http://www.ezboard.com/images/emoticons/wink.gif ALT=";)"><!--EZCODE EMOTICON END--> <br>
<br>
Anyway, as we all know, rollers vary from place to place. I think my 170 is conservative.

<p>Martin<br>
<br>
<!--EZCODE LINK START--><a href="http://www.dolomitesprint.com/" target="top">www.dolomitesprint.com</a><!--EZCODE LINK END--></p><i></i>