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Theory of 4 valve poly quad cylinder heads.

General engine tech -- Drag Racing to Circle Track

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Truckedup
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Re: Theory of 4 valve poly quad cylinder heads.

Post by Truckedup »

hoffman900 wrote: Fri Sep 13, 2019 10:39 am
Ducati has spent a lot of time and work on it to make a 4.5” bore work at 13,000rpm+, on pump gas, and a single plug. That said, Ducati has going down in bore size for improved combustion characteristics.
Ducati has gone to a V4 in their top of line bike....
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Re: Theory of 4 valve poly quad cylinder heads.

Post by hoffman900 »

Truckedup wrote: Fri Sep 13, 2019 12:35 pm
hoffman900 wrote: Fri Sep 13, 2019 10:39 am
Ducati has spent a lot of time and work on it to make a 4.5” bore work at 13,000rpm+, on pump gas, and a single plug. That said, Ducati has going down in bore size for improved combustion characteristics.
Ducati has gone to a V4 in their top of line bike....
Yep. A lot of reasons why, but part of that is to shrink the bore.
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Re: Theory of 4 valve poly quad cylinder heads.

Post by Truckedup »

hoffman900 wrote: Fri Sep 13, 2019 1:06 pm
Truckedup wrote: Fri Sep 13, 2019 12:35 pm
hoffman900 wrote: Fri Sep 13, 2019 10:39 am
Ducati has spent a lot of time and work on it to make a 4.5” bore work at 13,000rpm+, on pump gas, and a single plug. That said, Ducati has going down in bore size for improved combustion characteristics.
Ducati has gone to a V4 in their top of line bike....
Yep. A lot of reasons why, but part of that is to shrink the bore.
Probably more HP, more RPM and smoother....214 HP, 14,000 rpm in a bike lighter than a modern aluminum car V8 interesting injection with variable length trumpets
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Re: Theory of 4 valve poly quad cylinder heads.

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An opps...
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Re: Theory of 4 valve poly quad cylinder heads.

Post by hoffman900 »

Ducati has released its 214-hp desmodromic-valve Panigale V4, ending development of ever-larger V-twins in favor of a direct connection to all the company has learned in MotoGP. The 1299 Panigale pushed cylinder bore to an amazing 116mm, straining the limits of combustion control. In future, engineers say, 100mm will be the largest bore produced (in the form of the Panigale 959)
https://www.cycleworld.com/new-ducati-p ... p-forward/
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Re: Theory of 4 valve poly quad cylinder heads.

Post by digger »

they arent making any higher BMEP than what was done 15-20 years ago so why would they have issues on pump fuel when they pulling around a low mass, there is also a time factor the knock which works in favour of high rpm. two (2) inlet valves 34mm feeding a tiny cylinder like on the ductaui youd hope that 3+hp/cube would be achieved
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Re: Theory of 4 valve poly quad cylinder heads.

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digger wrote: Fri Sep 13, 2019 6:32 pm they arent making any higher BMEP than what was done 15-20 years ago so why would they have issues on pump fuel when they pulling around a low mass, there is also a time factor the knock which works in favour of high rpm. two (2) inlet valves 34mm feeding a tiny cylinder like on the ductaui youd hope that 3+hp/cube would be achieved
There were factory stock street bikes in the 1000 cc class 15-20 years ago meeting 2019 cyle emissions and noise standards making 3.1 HP per cubic inch like the current Ducati that has an advertised 14-1 compression ratio.. ? It's a whole new game for Ducati and the other European and Japanese bikes are also there.
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Re: Theory of 4 valve poly quad cylinder heads.

Post by gruntguru »

I have just re-scanned this entire thread and there is a lot of ignorance regarding swirl vs tumble. For most of history nearly all automobile engines had swirl and no tumble. I am talking of course about 2 valve engines. In the correct dose, swirl is highly beneficial. All the texts from Ricardo, Taylor, Heywood etc have sections on optimum swirl rates.

The link below was posted elsewhere in this thread. If you haven't read it yet I recommend you do. It tells you a lot about polyquad.

http://www.motortecmagazine.net/the-fut ... e-engines/
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Re: Theory of 4 valve poly quad cylinder heads.

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gruntguru wrote: Fri Sep 13, 2019 7:34 pm I have just re-scanned this entire thread and there is a lot of ignorance regarding swirl vs tumble. For most of history nearly all automobile engines had swirl and no tumble. I am talking of course about 2 valve engines. In the correct dose, swirl is highly beneficial. All the texts from Ricardo, Taylor, Heywood etc have sections on optimum swirl rates.

The link below was posted elsewhere in this thread. If you haven't read it yet I recommend you do. It tells you a lot about polyquad.

http://www.motortecmagazine.net/the-fut ... e-engines/
David makes a lot of claims that I’m curious of the source

The 11:1 compression ratio argument doesn’t hold (see the 14.1 compression on 91 octane on those Ducati’s with port injection, and many other examples well over 11:1), the lower depressions don’t either - 4 valves heads have enough valve area where they can be smaller to maintain velocity without giving up valve area, and that the tumble decays as the piston rises up (but swirl does not), that 4 valve heads give up torque (design a 4 valve engine to peak lower and it will) - actually because of the increased valve area you run shorter duration cams for a given rpm range (we saw this at the EMC the year the 4 valve Fords destroyed the 2 valve engines which had more aftermarket race oriented parts to the modified OEM Ford pieces), lastly the crossflow is a function of valve timing - what’s the typical valve margin between an intake valve and exhaust valve on a race oriented 2 valve head? You absolutely have charge going out the cylinder when you’re talking designs where the valves are close enough to have overlapping valve seats.

Everything I’ve read from Toyota, Honda, and observed with other marques (bikes and cars) shows that a lot of that just isn’t true. Maybe on 4 valve heads from 40 years ago, but not today. Then the Ford 2L test in the article - throw out there the name Roush to make it sound important, certain % gain at 1500rpm (would love to know the dyno type and how it was loaded between the runs), then of course there never was a full dyno pull - but of course those egghead engineers would never admit they were out witted.... I would love to hear the other side of this story, I bet it doesn’t play back the same ;)
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Re: Theory of 4 valve poly quad cylinder heads.

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I did read a white paper where Honda leaves one of the exhaust valves closed until about 2000rpm. They found doing this increases the port turbulence, which causes any remaining fuel to be burnt off faster, which in turns causes the cat to heat up sooner. The other benefit is that it kills low rpm exhaust flow down which helps with reversion, which is where the power benefit came from. Above 2000 rpm, they’re both on.
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Re: Theory of 4 valve poly quad cylinder heads.

Post by ptuomov »

To me, it's self evident and clear that if you put a two-valve head and a four-valve head on the same short block and size them (and the cams) to make the same peak hp at the same rpm, then the four-valve head is going to make more low rpm torque and be overall a lot nicer to drive. However, what's self evident to me isn't necessarily self evident to others, or even necessarily true...
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Re: Theory of 4 valve poly quad cylinder heads.

Post by SchmidtMotorWorks »

gruntguru wrote: Fri Sep 13, 2019 7:34 pm I have just re-scanned this entire thread and there is a lot of ignorance regarding swirl vs tumble. For most of history nearly all automobile engines had swirl and no tumble. I am talking of course about 2 valve engines. In the correct dose, swirl is highly beneficial. All the texts from Ricardo, Taylor, Heywood etc have sections on optimum swirl rates.

The link below was posted elsewhere in this thread. If you haven't read it yet I recommend you do. It tells you a lot about polyquad.

http://www.motortecmagazine.net/the-fut ... e-engines/

From the article:

Arao four valve heads

Anyone ever seen an Arao head?
Not worthy of being used as a testing platform.
The test done showed as much a 7% increase in low speed output (1500 rpm) with no loss of top end output. That extra low speed torque would make this 2 liter engine drive as if it had 2.14 liters. Was Ford interested? Seemingly not – but there again I have been in this position many times. It seems an outsider coming up with a better idea than the guys on the inside threatens job security. That is the real reason the ‘not invented here’ syndrome comes about – but that’s life.


When Ryan ran back to back tests on a chassis dyno in Florida on a very hot and humid day the PolyQuad head showed a gain of 98 hp and 105 lbs-ft on 5 lbs less boost. Ryan also later reported that the drivability (and this engine had some fairly big race cams) was greatly improved. The first dyno session netted a peak rear wheel output of 827 hp on wrinkle wall slicks.
Engine testing on a chassis dyno with slicks?

Difficult to take seriously.
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Re: Theory of 4 valve poly quad cylinder heads.

Post by hoffman900 »

The Arao head is what I had in mind when I was talking 4vpc conversion heads. Just because it has 4 valves doesn’t mean it’s better, especially when most of what we’re talking about isn’t considered.

Curious to see who (outside the OEMs) can consistently start at a dyno pull at 1500rpm. :shock:

Supposably that Mitsubishi has ports “you can drive a truck through” and was mentioned by a tuner you can half fill it with epoxy and make more power. Logan hit on that about the 1990s trend of Honda and Mitsubishi making the ports wayyy to big to realize any real tumble, especially at lower depressions.
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Re: Theory of 4 valve poly quad cylinder heads.

Post by ptuomov »

So what are the best papers to read on that Honda R&D site?
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Re: Theory of 4 valve poly quad cylinder heads.

Post by hoffman900 »

ptuomov wrote: Sun Sep 15, 2019 7:19 am So what are the best papers to read on that Honda R&D site?
The ones on Formula One engine development are great. Just search “engine” and use the drop down to select motorsports. They also have one on turning the IRL engine into a ALMS/ FIA engine that have to utilize restrictors.

If you search “tumble”, you’ll get some great ones. The ones where they get into their test engines to validate their CFD / burn models are super cool. They map port velocity on steady state benches using optical sensors that measure particle motion in the port - no pitot tube to influence the outcome. Lots of other cool sensors measuring cylinder motion, burn rates, etc. too. Once they correlate things, it’s all computer development from there which they also get into.

I’ll make a list later.
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