Thread: things to upgrade for high performance

been doing some more tinkering with the exhaust manifold and have been thinking about what has been said about how there made..
40mmNB tube has been used for runners which equates to 1256mm surface area
the exhaust port from measurements given are 36mmx48mm that equates to 1728mm surface area.
what my concern is thats a difference of 472mm surface area meaning that the 40mmNB tube has that much less surface area than the exhaust ports which means restriction doesnt it? unless the corner radius of the exhaust port timed by 4 equals approx 472mm then the surface area will match that of the 40mmNB tube.
anyone done the exact calcs?

Originally Posted by c.h.i.e.f

been doing some more tinkering with the exhaust manifold and have been thinking about what has been said about how there made..
40mmNB tube has been used for runners which equates to 1256mm surface area
the exhaust port from measurements given are 36mmx48mm that equates to 1728mm surface area.
what my concern is thats a difference of 472mm surface area meaning that the 40mmNB tube has that much less surface area than the exhaust ports which means restriction doesnt it? unless the corner radius of the exhaust port timed by 4 equals approx 472mm then the surface area will match that of the 40mmNB tube.
anyone done the exact calcs?

it actual starts with open surface area of the valve and dwell time etc, the cross section of the port and manifold etc etc has more to do with gas speed in the first instance. so you need to do that first.

so it will be allowable to have a slightly smaller tube diameter than the port and will not "choke" the flow of exhaust gasses but will increase gas velocity? enlarge the diameter of the tube by a bit and velocity will drop ?
i interpret this as the diameter of the tube shal be based on the valve opening rather than exhaust port size? from how i read what you have said...

Originally Posted by c.h.i.e.f

so it will be allowable to have a slightly smaller tube diameter than the port and will not "choke" the flow of exhaust gasses but will increase gas velocity? enlarge the diameter of the tube by a bit and velocity will drop ?
i interpret this as the diameter of the tube shal be based on the valve opening rather than exhaust port size? from how i read what you have said...

Yes Yes and no. but its where you start

an example, 225 wedge head, every one was fitting 318 valves, all i did was machine the wedge back from the valves, much better flow, but not applicable in our case.

so lift or valve drop so Pi R2 X lift gives your area. there is more maths for volume but we can cover that latter.

and yes smaller = faster

you could for example have small dia heaters to speed things up a bit to aid savaging ( such as it is) and to or spool up a turbo quicker. VNT turbos are just that all about making smaller to speed up the gasses for a quicker spool up.

the next thing is calculation sonic pulses. just like how a DB rattles out gear boxs at idle sonic pulses can damage a turbo ( or shorten life) if it is being asked to speed up then slow down 2 times per revolution. the log manifold is how to cheat your way out of this problem. the other way to do this is to head the pulses into each other head on, this is what the std manifold will do. 1 into 3 2 into 4 etc. or you can build a reflector into a header box pre turbo OR you can do that overly complicated funnel thing as talked about above but then for them to really work you need to be spinning at about 20 000 rpm

Originally Posted by c.h.i.e.f

so it will be allowable to have a slightly smaller tube diameter than the port and will not "choke" the flow of exhaust gasses but will increase gas velocity? enlarge the diameter of the tube by a bit and velocity will drop ?

another thing

smaller diameter is Less surface area do less paristic drag, but then this advantage may be lossed due to increased pressure increasing drag, more maths

Oh dear ...... Well with your maths what do you think about the 40NB tube would it be adequate ? Or is that a pointless question not knowing where randy may want his max gains from (low,mid or high rpm) ?

Originally Posted by c.h.i.e.f

Oh dear ...... Well with your maths what do you think about the 40NB tube would it be adequate ? Or is that a pointless question not knowing where randy may want his max gains from (low,mid or high rpm) ?

40 NB is what I used. At the time I found the cross section area a good enough match, but perhaps I used thinner wall thickness than you have - they come in many wall thickness (from memory, without looking up tables) Schedule 10 (thinnest), sched 20, 40 & 80, also light (same as sched 20), standard (same as sched 40), or extra strong (XS) weights (can't remember if sched 120 or XXS are readily available in 40 N.

Randy (carcrafter22) used 40 NB fittings for his manifold and the manifold kits for the Cummins 4BT also use 40 NB fittings.

Originally Posted by 85 county

Yes Yes and no. but its where you start

an example, 225 wedge head, every one was fitting 318 valves, all i did was machine the wedge back from the valves, much better flow, but not applicable in our case.

so lift or valve drop so Pi R2 X lift gives your area. there is more maths for volume but we can cover that latter.

and yes smaller = faster

you could for example have small dia heaters to speed things up a bit to aid savaging ( such as it is) and to or spool up a turbo quicker. VNT turbos are just that all about making smaller to speed up the gasses for a quicker spool up.

the next thing is calculation sonic pulses. just like how a DB rattles out gear boxs at idle sonic pulses can damage a turbo ( or shorten life) if it is being asked to speed up then slow down 2 times per revolution. the log manifold is how to cheat your way out of this problem. the other way to do this is to head the pulses into each other head on, this is what the std manifold will do. 1 into 3 2 into 4 etc. or you can build a reflector into a header box pre turbo OR you can do that overly complicated funnel thing as talked about above but then for them to really work you need to be spinning at about 20 000 rpm

Oh dear
The pulse converters you are referring to are used on and were developed by manufactures of large marine diesels as used in ships.

Your comment about needing to spin at about 20 000 rpm is way off and very missleading - how do you substantiate the 20 000 rpm comment?