Port comparison
Port comparison
(OP)
I have recently tested 6 different ports on a flow bench at 25" H2O. The ports are known to have a poor short-turn radius that is too tight. The port modifications were attempts to overcome the flow seperation that occurs in the std port.
The std port flows:
in: .05 .1 .15 .2 .25 .3 .35 .4 .45 .5
cfm: 26 51 74 96 115 127 136 139 142 144
One modified port flows:
in: .05 .1 .15 .2 .25 .3 .35 .4 .45 .5
cfm: 25 50 73 95 112 127 141 154 163 167
My query is in regards to possibility of onset of flow seperation. In the std port the volume of flow per .05 in of lift starts to decrease at .2-.25 a 12 cfm increase, at .25-.3 there is a 9 cfm increase and .3-.35 there is a 3cfm increase.
From this I get the impression that the flow is perhaps starting to seperate at .2/25 and the flow seperation get progressively worse, i.e. has greater detrimental effect on the overall flow rate.
Whereas the modified port reduces the impact or amount of flow seperation at the same lifts.
Is this a reasonable train of thought?
The std port flows:
in: .05 .1 .15 .2 .25 .3 .35 .4 .45 .5
cfm: 26 51 74 96 115 127 136 139 142 144
One modified port flows:
in: .05 .1 .15 .2 .25 .3 .35 .4 .45 .5
cfm: 25 50 73 95 112 127 141 154 163 167
My query is in regards to possibility of onset of flow seperation. In the std port the volume of flow per .05 in of lift starts to decrease at .2-.25 a 12 cfm increase, at .25-.3 there is a 9 cfm increase and .3-.35 there is a 3cfm increase.
From this I get the impression that the flow is perhaps starting to seperate at .2/25 and the flow seperation get progressively worse, i.e. has greater detrimental effect on the overall flow rate.
Whereas the modified port reduces the impact or amount of flow seperation at the same lifts.
Is this a reasonable train of thought?





RE: Port comparison
Regards
eng-tips, by professional engineers for professional engineers
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.
RE: Port comparison
Same valve and same single angle seat dimensions used in all tests. Port mods made to port floor only.
RE: Port comparison
RE: Port comparison
I would be a truckload for a 4 cylinder 16 valve about 1.5 to 2.2 litre engine
Regards
eng-tips, by professional engineers for professional engineers
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.
RE: Port comparison
RE: Port comparison
What have you been smoking?
2lt 8V?
Regards
eng-tips, by professional engineers for professional engineers
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.
RE: Port comparison
1: I do not smoke and I am unsure of what you are querying.
2: The heads from a 2 litre, 8 valve engine are used as the basis of a magazine article. They are used because they have a known problem, they are cheap and are representative of many heads of that period, these engines (8 valve, 4cyl) still form the basis of much of club level motorsport and marque classes.
3: the article series is looking at different solutions and what results are gathered. The intention is to start broadening the technical enquiry, which in current Australian magazines has been lowered to the stage that a porting article is 7-800 words, a photo of a head, a bloke holding die grinder and a finished head that then purports to flow X horsepower. None of which is particularly enlightening.
4: yes I could use 16v heads. Infact I could report of a 1600cc NA Honda engine that makes 147kW, but that is a $20k engine (not counting development cost) and not really in most people's budget.
RE: Port comparison
RE: Port comparison
RE: Port comparison
2 litre 8 valve 4 cylinder should have slightly lower lift than an American V8, but considerably more than a 16 valve 4 cylinder.
0.4 sounds pretty fair for high performance road car and 0.5 or a little more sounds about right for a race engine.
Regards
eng-tips, by professional engineers for professional engineers
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.
RE: Port comparison
RE: Port comparison
I wouldn't dare to suggest that our two observations might be related.
Regards
eng-tips, by professional engineers for professional engineers
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.
RE: Port comparison
Just my two cents
Scott