PolyQuad - A new four valve power concept

[KLR142]

Originally Posted by Mikeyboy(uk)

Hmm, PQ on a motorcycle head-now there's an interesting thought. I think that the main area of interest would be for off-road uses, such Moto-X and Enduro, as all out race motors need all the power they can get, along with smooth, linear power curves. With Road Racing, if you put too much mid range into the motor you just burn the rear tyre too quickly in most Superbike races. However, off-roaders like to have power "Right Now" in most instances, so I think this may be the best area to explore with PQ.

Well, there are also those people, like myself, who are tooling around on a smaller displacement motorcycle in day to day use that could benefit.

Originally Posted by Mikeyboy(uk)

Keep it coming David, top quality articles are everywhere on this site.

Here here! Top quality articles are such a relief coming from a website I usually spend a good chunk of my time on. I will definitely be spending more of my time here now, where I can actually learn something and where the BS is kept to a minimum.

Cheers!

[crowkiller]

Anybody else signed up to do this work yet? T & L Engines does not seem to inclined to answer e-mail queries on this subject. Is there maybe a secret codeword or handshake thing I should be doing to get an answer???

[FlowSpecialist]

Originally Posted by Mikeyboy(uk)

My second point is regarding the valve periphery. With any 4 valve engine, the long timeframe (low rpm) allows much more reversal to take place at low rpm compared with a 2 valver. It is even worse with a 5 valve- a head design I have 20 years experience of playing with.(Old now you see!!!) A 5 valve is hyper sensitive to cam timing and in particular, seat duration. The excessive peripheral flow means that motors are sensitive to tiny cam timing changes. To give you an idea, on the flow bench, a 5 valve flow chart looks as though you have missed a station out and everything is moved one lift increment early. So what I am leading up to is, I think your article should have pointed out that the valve circumferences with PQ are less than a conventional 4 valve, so therefore this may account for some of the low end torque gains.

Firstly, hello folks, this is my first post in here and to DV just so you know who this is, sorry I keep losing you on the cordless phone when the batteries go flat. It seems that after 3 years they're completely buggered so I'll have to get some new ones before we speak again. I did try dialing with an old corded phone but it was pulse dialing not tone dialing and wouldn't work with my cheap call provider to the USA.

Anyway, very interesting concept in head design which I'm giving some thought to and will no doubt have more questions later. To respond to Mike's point above, if we make the assumption that increasing the diameter of one inlet valve by 1mm requires the other one to be reduced by 1mm to preserve the previous clearance between them then in fact the total valve circumference doesn't change. What is interesting though is the total area actually increases slightly the more you stagger the valve sizes. To demonstrate, if we take a head with two 35mm inlets and stagger them by 1mm at a time we get the following total area in sq mm.

35 & 35 - 1924.2
36 & 34 - 1925.8
37 & 33 - 1930.5
38 & 32 - 1938.4

The reason is straightforward. The total circumference (or diameter) is staying the same but we are steadily moving towards an ultimate situation of having only one valve of 70mm diameter which would have an area twice that of two valves of 35mm diameter. The effect is minimal over a small range of stagger though so we shouldn't actually be seeing any difference in flow potential over conventional heads.

In practice each time we change the valve sizes we really need to also change the guide position to maximise the utilisation of the combustion chamber so this is a concept optimally done at the factory rather than by trying to modify existing heads.

There is a further problem though. If we do have a chamber with the space optimally utilised with equal sized valves, i.e. they are both as close as possible to each other, the chamber walls and the spark plug as they can get then there is actually no scope for polyquading without sacrificing valve area. For ultimate race use it therefore seems to me that the conventional method may still be the best.

For road use with non-optimally filled chambers, which no standard head will ever have, then there is indeed scope for this so what we are really boiling down to is for a given amount of raw flow how important is extra swirl, or more specifically reduced ignition delay, to power or perhaps low rpm power?

I think to answer this properly we have to test with very carefully prepared heads that have the same amount of total flow. Any flow differences are going to mask the results. Now in general 4v heads already require less ignition advance than 2v ones so I've always believed that the tumble in 4v engines is superior to the swirl in 2v ones anyway. Is even more mixture agitation going to help, if so by how much, can we actually have too much of it as Mike surmises?

We ought to be able to answer this question from first principles based on the effects of decreasing ignition advance requirement on power. Theoretically of course the optimum is an instantaneous burn at TDC but the mechanicals would never stand up to that or even anything approaching it, like detonation.

As yet I'm not convinced that this concept is actually beneficial to high rpm power and that maybe the improvement on engines such as Ryan's was just down to better head work than to polyquading. I'm more persuaded that it has benefits at lower rpm for road or fast road engines. I'd certainly like to see more testing of the concept.

regards

Dave B.

[DavidVizard-GFN]

[quote=As yet I'm not convinced that this concept is actually beneficial to high rpm power and that maybe the improvement on engines such as Ryan's was just down to better head work than to polyquading. I'm more persuaded that it has benefits at lower rpm for road or fast road engines. I'd certainly like to see more testing of the concept.

regards

Dave B.[/QUOTE]

Dave,
Great to hear from you again after what must be several years (time flies!!!!).

As usual you have made some great observations and come to some sound conclusions. When I did this project the sole intent at the time was to boost low speed output with no top end penalty. That appears to have been achieved. The fact that PQ has been successfully used on racing engines (Including F1 and Indy) is almost a side issue. I do not make any money on such and as for fame and glory, well it's over rated and you can keep it - I would rather have a big bank balance any day.

Most of the points you bring up with regard to isolating the effect of PQ in the overall scheme of things I have tried and the bottom line is that for low speed it works.

AS I said in the article the gains seen from Ryans head was partly ports and partly PQ. The bottom line here is that producing a good race head, 2 or 4 V, is not as simple as it is so often portrayed.

A subject that I will b e dealing with shortly in 'Porting School' will be port and valve sizes.

Anyway Dave, thanks for your observations and input - as always it's much valued here.

DV

[FlowSpecialist]

Hi David,

Glad to be on board here and I'm full of admiration for the quality of the technical articles on display. As I said elsewhere it's a shame these aren't being seen by a wider audience as they deserve.

I've been re-reading the PQ article and followups and really it's a stunning concept. Probably the most innovative new concept in head design I've ever seen. In a way I'm miffed I didn't come up with it myself but if what I do is evolution then what you do is revolution and perhaps I simply don't have the brain design to reinvent the wheel on a regular basis as you seem to keep doing. Maybe there's a place for both types of thinking with me grinding away and evolving best practice and you leaping ahead to new lines of thought which I'll catch up to later. Damn it it's clever though.

Dave

[rsicard]

David: What is the RED and the BLUE coating on the Polyquad Cylinder Head VALVES? Please explain. Thanks.

Regards,

Rolland Sicard

[howieschoon]

This is under the picture of the valves:
"Seen here is the finished T&L PolyQuad Mitsubishi head. The red coating on the back of the intake valves has some insulating properties but it’s main asset is that carbon can not easily stick to it so the form of the back of the valve is not altered by carbon build up."

If the blue coating you are talking about is on the stems I would assume it is some kind of dry-film lubricant but I don't really know, but the above should answer one of your questions. It could also just be a reflection of the background, the machined surface on the ports appears to be a similar color.
Howard

[rsicard]

David:

In the picture of the polyquad cylinder head and valves, the valves are coated with thermal barrier, a blue coating on the stems and a red coating on the backside of the valves. What is the blue and red coatings and what are their properties? Please advise. Thanks.

[Dusty]

I can't speak for the red coating but the blue coating is created by a bombardment of photons of a particulair wavelength of about 475 nanometers. You can apply this coating in your own home with a piece of blue paper and a camera flash!!! Had you going for a second didn't I. Its just trick photography it gets real boring taking pictures of plain old metal all the time

[rsicard]

Dusty: Thanks for the answers. I was hoping that there was a coating which could be used on the backside of the valves to inhibit buildup of carbon. Or does using thermal barrier coating on the chamber side of the valves reduce heat transferred to the backside of the valve and thus inhibit carbon buildup?