Polyquad for 5 valve motor?
Discussion
This question is primarily for David Vizard or David Baker.Of course if any other eminent engine builders have direct experience relating to my question,I'd like to hear of their results too.
Will the Polyquad concept have similar benefits for a 5 valve engine and if so how would it be achieved in practice.I'm in the process of flowing and big valving a 5 valver at the moment.I have acquired another spare head and fancy trying the concept out.I have made a start by welding the chamber as suggested by DV between the inlets and exhaust.I'm thinking of sizing the three inlets std size,+1mm and +2mm respectively to try and generate the correct flow bias characteristics.
I can appreciate how PQ works for 4 valvers but think perhaps it may not be nearly as effective or worthwhile in generating swirl with 3 inlet valves almost side by side as it were.
Your thoughts would be greatly appreciated.
Mark.
Will the Polyquad concept have similar benefits for a 5 valve engine and if so how would it be achieved in practice.I'm in the process of flowing and big valving a 5 valver at the moment.I have acquired another spare head and fancy trying the concept out.I have made a start by welding the chamber as suggested by DV between the inlets and exhaust.I'm thinking of sizing the three inlets std size,+1mm and +2mm respectively to try and generate the correct flow bias characteristics.
I can appreciate how PQ works for 4 valvers but think perhaps it may not be nearly as effective or worthwhile in generating swirl with 3 inlet valves almost side by side as it were.
Your thoughts would be greatly appreciated.
Mark.
What sort of results are you getting on your flow bench to encourage you this is the way to go?
Here is a link to a forum talking about Yamahas five valve head
http://www.r1-forum.com/forums/showthread.php?t=37...
Peter
Here is a link to a forum talking about Yamahas five valve head
http://www.r1-forum.com/forums/showthread.php?t=37...
Peter
Peter,
I've read all the stuff on that forum worth reading,but thankyou for the link.
Nothing there adresses the question I asked.
I don't own or have access to a flow bench,but I don't think that is relevant to my enquiry.
I respect and admire the work that DV publishes.When I read about PQ in his latest book it set in motion a train of thought regarding the compatability of the PQ advantages and 5 valve heads.A five valve head is what my engine has and I can't change that. If no one has direct experience then I will go ahead and follow my hunch.It's early days yet so I'm still hopeful of an answer.
Does DV still contribute here at all.If not where might I find him?
Mark.
I've read all the stuff on that forum worth reading,but thankyou for the link.
Nothing there adresses the question I asked.
I don't own or have access to a flow bench,but I don't think that is relevant to my enquiry.
I respect and admire the work that DV publishes.When I read about PQ in his latest book it set in motion a train of thought regarding the compatability of the PQ advantages and 5 valve heads.A five valve head is what my engine has and I can't change that. If no one has direct experience then I will go ahead and follow my hunch.It's early days yet so I'm still hopeful of an answer.
Does DV still contribute here at all.If not where might I find him?
Mark.
He only shows up when he's got a book to flog or a seminar to fill.
DB hasn't posted for a while, I seem to remember he was taking a break, moved house to Scotland so probably busy with that (maybe setting up a new workshop) or has little internet connection...
PQ is interesting, but have you found anyone who has done it and got before and after tests?
If it does work I can't see it not working on a 5v head.
Isn't it the case that swirl is a positive at low RPM, but has a negative effect at high RPM?
Sorry I can't be of more help.
DB hasn't posted for a while, I seem to remember he was taking a break, moved house to Scotland so probably busy with that (maybe setting up a new workshop) or has little internet connection...
PQ is interesting, but have you found anyone who has done it and got before and after tests?
If it does work I can't see it not working on a 5v head.
Isn't it the case that swirl is a positive at low RPM, but has a negative effect at high RPM?
Sorry I can't be of more help.
Edited by Evoluzione on Friday 8th March 09:48
I was asking about the flowbench as I was wondering how you were going to develop the changes so they work? What may seem good to the eye does not necessarily prove good to the engine power. You are not following anyone elses tested development so you are starting from base. A simple velocity probe in different areas of the ports valve throats might be interesting when developing the larger valve variant.
The work we have done in the early nineties on a genesis head would suggest it needs a lot of testing to make a larger valve to create swirl and have a really positive effect, it is very different from a two inlet valve setup.
Peter
The work we have done in the early nineties on a genesis head would suggest it needs a lot of testing to make a larger valve to create swirl and have a really positive effect, it is very different from a two inlet valve setup.
Peter
David Vizards latest book is titled "How to PORT & FLOW TEST Cylinder Heads" published by Car Tech ISBN 978-1-934709-64-1
All the comments are thoughtful.I am seeking mid range torque as a priority. I'm aiming to make the torque curve as wide as possible by improving swirl and combustion.The attraction of the PQ concept is that promotes a lot more swirl.But a five valve head is a completely different kettle of fish to a four valve.
In my own mind at least the potential advantages make the project worthwhile persuing.I'm no development engineer but it appears I'm blazing a trail with this. I find it pretty hard to believe that I'm the first to tread this path. It would be good to speak to someone who has done this already.
Mark.
All the comments are thoughtful.I am seeking mid range torque as a priority. I'm aiming to make the torque curve as wide as possible by improving swirl and combustion.The attraction of the PQ concept is that promotes a lot more swirl.But a five valve head is a completely different kettle of fish to a four valve.
In my own mind at least the potential advantages make the project worthwhile persuing.I'm no development engineer but it appears I'm blazing a trail with this. I find it pretty hard to believe that I'm the first to tread this path. It would be good to speak to someone who has done this already.
Mark.
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