Improving a Cylinder head for better engine performance
Discussion
Does anyone know of anyways to increase the performance of an engine by altering things on the cylinder head? I've already done a bit of research on this and from what i understand, increasing the bore/diameter/width of the inlet and exhaust valves, you can increase air flow. Are there any equations or formulas to find out how much to increase them by or to work out the end output? Also, i heard that smoothing the actual inlet and exhaust ports can increase the airflow but polishing them can have adverse effects. Are there any equations/calculations for that?
Are there any formulas or equations that can be used to work out increased performance from alterations made in the cylinder head?
Thanks
Are there any formulas or equations that can be used to work out increased performance from alterations made in the cylinder head?
Thanks
thinfourth2 said:
Too hard to calculate most folk use a flow bench
P.S. Do we get a degree also for doing your homework?
See that's what i thought. But are there actual calculations cause according to the guys in my group, there are "loads" of them but from the research i did, i couldnt find a single one and the only thing that i could find was to use flow benches and stuff like that.P.S. Do we get a degree also for doing your homework?
Haha, you wouldn't want any of the marks for this report anyway. I've already done it but i'm trying to clarify or find some sort of justification for giving me 28%
doogz said:
It's not that smoothing them is good, and polishing them is bad, it's that smoother is better, to a point. Then boundary layer seperation occurs, and f
ks it all up 
Also, porting heads, i.e. smoothing out the exhaust ports on the head so that they match the size of the opening on the manifold is shown to produce better results at higher rpm, however, the "step" between the head and manifold that you'll find on most standard cars for some reason or another, helps driveability at low revs, possibly something to do with a bit of turbulent flow creating some backpressure? Dunno tbh.
I wanted to do my final year project on exactly this, but the guy in the Aero dept that "owned" the flowbench was a dick, essentially.
Yeah i know. I was just summing it up. Then again, from what i've seen there are very mixed feelings towards polishing and whether it actually does anything or makes things worse by not allowing the fuel and air to mix very well with the turbulence a rougher surface would give.ks it all up Also, porting heads, i.e. smoothing out the exhaust ports on the head so that they match the size of the opening on the manifold is shown to produce better results at higher rpm, however, the "step" between the head and manifold that you'll find on most standard cars for some reason or another, helps driveability at low revs, possibly something to do with a bit of turbulent flow creating some backpressure? Dunno tbh.
I wanted to do my final year project on exactly this, but the guy in the Aero dept that "owned" the flowbench was a dick, essentially.
So do you know any equations that are used to work this performance increase or is it literally just flow benches and dyno testing that find out whether or not the stuff you've done to the cylinder head have actually made a difference?
Reduce the valve angle, so the inlet goes straight down into the cylinder. Increases torque. Nissan used to do it with their engines, high port or something.
Try to induce more air swirl, but then I'd expect you'd want the air to swirl properly, not just stratify, which would require big calculations/modeling.
These would require custom made heads though.
Try to induce more air swirl, but then I'd expect you'd want the air to swirl properly, not just stratify, which would require big calculations/modeling.
These would require custom made heads though.
doogz said:
Silly idea perhaps, but why don't you go ask him/her?
I did actually ask about why he gave me 28% and he said it's because the others in my group did more. It's the most retarded thing i've ever heard. The fact that i was assigned the cylinder head (where there are almost no calculations i can do) and the others had pistons, valves, piston rings and some others where there are millions of calculations and modelling they can do, i still can't understand how that was justification. Oh well, i'm still fighting!!http://users.erols.com/srweiss/tablehdc.htm
for 40 dollars you could have just copied and pasted the software on this website. It's the first link if you google "calculations for predicting cylinder head flow"
for 40 dollars you could have just copied and pasted the software on this website. It's the first link if you google "calculations for predicting cylinder head flow"
snoopios said:
I did actually ask about why he gave me 28% and he said it's because the others in my group did more. It's the most retarded thing i've ever heard. The fact that i was assigned the cylinder head (where there are almost no calculations i can do) and the others had pistons, valves, piston rings and some others where there are millions of calculations and modelling they can do, i still can't understand how that was justification. Oh well, i'm still fighting!!
Being a second year student on a degree course they probably expected quite a bit of detail .. did you contact the likes of ricardo, caterpillar/perkins or cosworth (or any other engine research centres) to see if you could sit in for a few days and gather some knowledge? That might have got you a few marks. There's a host of engine development guys on PH too .. they're not difficult to find if you read the engines forum, and if you approach them properly and at least sound like an inquisitive person they might be able to help you in future.maniac0796 said:
If you move the head closer to the block, then it'll increase it. Either using a thinner gasket or skimming some material off the head.
Surely there are some calcs that can be done on that then. Also doesn't flowing work result in greater volumetric efficiency? If so there must be formulae relating to that.OP I don't know what formulae to use, or even if you can readily apply them, but surely you could have researched them and at least quoted them for greater marks?
snoopios said:
Are there any formulas or equations that can be used to work out increased performance from alterations made in the cylinder head?
A few minutes with Google suggests the Navier-Stokes equations may be the ones you seek. I'd have thought there would be absolutely tons of marks on offer if you could do anything intelligent with them - loads and loads of really difficult calculus would probably be a good place to start (but not for me!).
Out of interest, did the term 'CFD' appear anywhere in your report?
maniac0796 said:
wombat172a said:
Is the compression ratio not affected by the head?
If you move the head closer to the block, then it'll increase it. Either using a thinner gasket or skimming some material off the head. Thinner gasket (if available) will bring head closer to block and increase CR.
Skimming head can increase CR (depending on head design) but will never bring head closer to block, no matter how much you skim off.
snoopios said:
I did actually ask about why he gave me 28% and he said it's because the others in my group did more. It's the most retarded thing i've ever heard. The fact that i was assigned the cylinder head (where there are almost no calculations i can do)
What degree are you doing, out of interest?
This is a CFD coursework, with a small amount of mechanical foresight. To make more power you need to get more air into an engine (getting the extra fuel in is comparatively easy). So look at a straighter path for the air to take or inducing turbulent flow before corners (turbulent flow boundary layers are more viscous than lamina so will flow around corners with less separation) and so on so forth.
Then, crudely mock up two cylinder heads in CAD, one showing the characteristics you don't want, one with the characteristics you do, run them through a CFD package and demonstrate that one head flows more air than the other and could therefore make more power.
As for there being loads of equations, I can only assume these would be engine based equations to do with volumetric efficiency BMEP assuming a given flow rate through the head, which to me doesn't answer the question.
Then, crudely mock up two cylinder heads in CAD, one showing the characteristics you don't want, one with the characteristics you do, run them through a CFD package and demonstrate that one head flows more air than the other and could therefore make more power.
As for there being loads of equations, I can only assume these would be engine based equations to do with volumetric efficiency BMEP assuming a given flow rate through the head, which to me doesn't answer the question.
The book to get is this one by Heywood.
It would be best to get a copy from a library given the high cost.
Nevertheless it contains a lot of good material from an internationally respected author with a huge number of OEM clients.
http://www.amazon.com/Internal-Combustion-Engine-F...
It would be best to get a copy from a library given the high cost.
Nevertheless it contains a lot of good material from an internationally respected author with a huge number of OEM clients.
http://www.amazon.com/Internal-Combustion-Engine-F...
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