qbic2007
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| posted on 14/3/15 at 08:09 PM |
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custom exhaust header - open discussion
Hello fellow builders
I need a custom exhaust header for my Dax Rush. I'm thinking of designing a 4-1 (or 4-2-1) myself and having the pipes bend and welded
in a workshop.
Reason I wanna do it myself, pure fun, no standard available for my engine, no good exhaust tuner in the neighborhood, ... :wink:
The following is work in progress and me thinking out loud, I'd appreciate your experienced opinions.
Knowing my driving style, on the road I usually keep it relaxed, on track or occasion I tend to rev to the end. I suppose a 4-1 would fit my driving
style.
Also the damper will need a cat unit, it is the long damper model, probably leaving me little room for a 4-2-1 system.
My engine: Ford Zetec-SE 1.6 (ford focus 1.6) (DOHC)
My tuning:
- Direct to head throttle bodies
- uprated injectors and cams
- standard valves and ports (for now anyway)
My exhaust ports measure ~34mm diameter, next size up I can order is 38x1.5 or 38x2mm
ZSG 416 1,595 cc (1.595 L; 97.3 cu in) (79 mm (3.1 in)x81.4 mm (3.20 in)) I4 (std)100 PS (74 kW; 99 hp)@6000 146 N·m (108 lb·ft)@4000 11
Valve inlet 1.4/1.6 16v Zetec SE 30.0mm
Valve exhaust 1.4/1.6 16v Zetec SE 24.1mm
If I'm correct I should be able to calculate diameter and length with the above data.
One would go out from a primary diameter being slightly larger then the exhaust ports?! Correct?
>> 34mm port size >> 40x1.5mm or 40x2mm tube size
For the length, I found a few formulas, however I need some assistance filling the values correctly: (or if you have any other good formulas)
http://www.wallaceracing.com/header_length.php
http://www.mez.co.uk/mezporting/exhaust_length.html
(next step making some screenshot of how I filled the formula pages)
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qbic2007
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| posted on 14/3/15 at 10:10 PM |
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Got around confirming the diameter, this should be about it:
ID (inside diameter)
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Peak torque rpm = Primary pipe area x 88,200 / displacement of one cylinder
>> primary pipe area = peak torque rpm x displacement of one cylinder / 88200
>> ID Area = 5000 x 97.3 / 4 / 88200 = 1.37
diameter = SQRT( area / PI ) * 2 = 1.32 >> inch to mm = 33,6 mm
Confirmed with the bending workshop, they can do 38,1 x 1.27mm (1.5 inch) in SAE 304 (ID = 38.1- 2*1.27 = 35.56mm)
Would this be sufficient wall thickness for the exhaust header? (Naturally aspirated, no turbo plans)
[Edited on 14/3/15 by qbic2007]
[Edited on 14/3/15 by qbic2007]
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Davey D
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| posted on 15/3/15 at 01:25 PM |
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1.2mm wall thickness will be fine. That is what I used for the system I built on my car.
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