Hi Malcolm,
OK maybe a little harsh but even on petrol engines backpressure is not a
requirement appropiate gas velocities are though which are tuned via
pipe diameters and length's. Interestingly a exhaust manufacturer here
supplies a set of headers fro the hilux 3L 2.8L diesel engine and the
primary size and length they chose give a primary resonance at over
6000rpm I have never driven a 2.8 hilux that will rev that hard.
I hope I can post tables. Here is one for non turbo petrols, diesel use
requres bigger pipes.
pipe dia inches
power
2
100
2.25
150
2.5
200
3
300
3.5
350-400
2.5 Motorsport use no turbo
150-200
3 Motorsport use no turbo 200-250
3.5 Motorsport use no turbo 250-350
4 Motorsport use no turbo 350-425
4.5 Motorsport use no turbo 425-500
5 Motorsport use no turbo 500-650
For a diesel add upto one third to power output and check pipe size and
you will be in the ball park.
Cheers,
Craig.
Malcolm Bagley wrote:
>Craig,
>
>Perhaps a little harsh on a well proven field - exhaust tuning - for petrol,
>non turbo engines, resonance wouldn't be possible without the pipework and
>that causes a backpressure.
>
>I am always amazed at the way of diesels to make increased exhaust sizes, I
>would imagine it's no easy job to make a 3 1/2" exhaust to fit, perhaps why
>2 1/4" or 2 1/2" was suggested with some technical mumbo jumbo to smooth it
>over.
>
>
>Malcolm Bagley
>Stafford, UK
>1975 FJ45 Pickup (In Work)
>_______________________________
>
>
>-----Original Message-----
>From: [Email address removed] [mailto:[Email address removed]] On
>Behalf Of Craig Vincent
>Sent: 03 July 2006 21:07
>To: [Email address removed]
>Subject: Re: [ELCO] exhaust
>
>Hi Simon,
>Here we go the backpressure old wives tale. Yes it maybe applicable as a
>bandaid to help a poorly tuned petrol engine. The gas volume of a turbo
>diesel is larger than a petrol engine at most loads and speeds. 2 1/4"
>is miles too small as is 2 1/2" (toyota used 2 3/8" for reasons of
>cheapness not performance) 3" is the best option although 3 1/2" would
>do no harm (especially on a 24v, a turbo is happiest with no back
>pressure and no exhaust system at all except maybe a foot or so of 7
>degree divergent cone straight off the very back of the turbo). These
>guy's
http://www.beauexhausts.com.au/ make a very nice 3 1/2" dump pipe
>(that bolts on where the cast iron elbow on the back of the turbo goes,
>it has provision for a pyro but I prefer pre-turbo) that has a smooth
>transition into 3" pipe to help spool the turbo up and reduce
>backpressure in this critical area. One good high performance muffler is
>all you need after that such a flowmaster motorsport diesel muffler
>(very good noise reduction with near zero backpressure e.g. part #
>953540-10 but that is a 3.5" muffler, very quiet no louder than stock
>but a much deeper bass tone).
>The fact that they mention preserve backpressure would be enough for me
>to probably shop else where.
>
>Cheers,
>Craig.
>
>Simon Hughes wrote:
>
>
>
>>Hi All
>>
>>Gareth, do you have the 24 valver? I am thinking that with the 12
>>valves 2.5 may be enough but I was told by longlife that 2.25 or a max
>>2.5 to preserve the back pressure??
>>
>>All the best
>>
>>
>>Simon Hughes
>>
>>Tel: 020 7549 3663
>>Mobile: 07973 288061
>>Mail: [Email address removed]
>>
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