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Theory of 4 valve poly quad cylinder heads.

General engine tech -- Drag Racing to Circle Track

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hoffman900
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Re: Theory of 4 valve poly quad cylinder heads.

Post by hoffman900 » Wed Sep 11, 2019 11:09 am

LoganD wrote:
Wed Sep 11, 2019 10:36 am
hoffman900 wrote:
Wed Sep 11, 2019 9:29 am
A lot of this is why I think performance on the 4 valve conversion heads suffer, just lack of knowledge of how these heads work.

Would love to see someone rip off a modern Sport bike head (like a Ducati twin, with a 4.5” bore) and apply it to a pushrod V8 shortblock. Obviously it would cost a fortune, but the head would be billet and the valvetrain would be the same design and all OTS.
I mean, bolt on Coyote's are making 500 whp on regular pump fuel. People are going 9's in Coyote stock (sealed factory stock engines). Making 700 hp from a Coyote is not hard. The aftermarket frequently makes two mistakes:

1. Deleting VVT, the Coyote's biggest advantage
2. Improperly degreeing aftermarket camshafts (a big mistake). You can't just install aftermarket cams and go with a DOHC design as your actual cam timing is dependent upon how they are installed.
Of for sure. I meant the 4 valve conversion heads on old style blocks.
-Bob

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Re: Theory of 4 valve poly quad cylinder heads.

Post by sbcharlie » Wed Sep 11, 2019 6:44 pm

never heard of this poly quad idea. back in 2002 and on we used to install 2 different size valves in the crf 450 honda on the weak side on intake we use 2mm over valve with 50 degree seat and standard other side. work quite well. saw no reason to do it on exhaust.. the new designed head are interesting. we working on the new Kawasaki 450 head for next year they are a real puzzle. sbc

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Re: Theory of 4 valve poly quad cylinder heads.

Post by Truckedup » Wed Sep 11, 2019 7:40 pm

LoganD wrote:
Wed Sep 11, 2019 10:36 am
hoffman900 wrote:
Wed Sep 11, 2019 9:29 am
A lot of this is why I think performance on the 4 valve conversion heads suffer, just lack of knowledge of how these heads work.

Would love to see someone rip off a modern Sport bike head (like a Ducati twin, with a 4.5” bore) and apply it to a pushrod V8 shortblock. Obviously it would cost a fortune, but the head would be billet and the valvetrain would be the same design and all OTS.
I mean, bolt on Coyote's are making 500 whp on regular pump fuel. People are going 9's in Coyote stock (sealed factory stock engines). Making 700 hp from a Coyote is not hard. The aftermarket frequently makes two mistakes:

1. Deleting VVT, the Coyote's biggest advantage
2. Improperly degreeing aftermarket camshafts (a big mistake). You can't just install aftermarket cams and go with a DOHC design as your actual cam timing is dependent upon how they are installed.
I know it's easier to make more power per inch with a smaller engine and bike emissions are a bit easier than cars...But the bikes roll out the showroom floor with 3 plus hp per cubic inch...And the best two cylinder Ducati sport bikes have cylinders as large as a Coyote and make far more power per cylinder stock than a modified Coyote....
Motorcycle land speed racing... wearing animal hides and clinging to vibrating oily machines propelled by fire

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Re: Theory of 4 valve poly quad cylinder heads.

Post by hoffman900 » Wed Sep 11, 2019 7:41 pm

sbcharlie wrote:
Wed Sep 11, 2019 6:44 pm
never heard of this poly quad idea. back in 2002 and on we used to install 2 different size valves in the crf 450 honda on the weak side on intake we use 2mm over valve with 50 degree seat and standard other side. work quite well. saw no reason to do it on exhaust.. the new designed head are interesting. we working on the new Kawasaki 450 head for next year they are a real puzzle. sbc
What’s puzzling about them, Charlie?
-Bob

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Re: Theory of 4 valve poly quad cylinder heads.

Post by 4vpc » Thu Sep 12, 2019 4:46 am

hoffman900 wrote:
Wed Sep 11, 2019 6:36 am
4vpc wrote:
Wed Sep 11, 2019 4:23 am
LoganD wrote:
Tue Sep 10, 2019 10:10 am
You don't want swirl in a gasoline spark ignition engine. If you're seeing combustion efficiency improvements with the introduction of swirl then the system simply didn't have enough charge motion to begin with. Tumble is what you want in a gasoline SI engine. High swirl rates produce fuel/air separation and move the fuel away from the spark plug (centripetal acceleration) producing a localized lean zone by the spark plug....and that's the exact opposite of what you want.

This is why you've seen the move away from steep valve angles in 4-valve cylinder heads to much shallower valve angles without a major change in port angle. The amount of tumble in a new 4-valve cylinder head (anything post 2018) is crazy, and this is how they're getting 32 bar BMEP on 91 octane.

This WAS a debate for a long time, but it turned out that the steep valve angles and large ports in 90s 4-valve heads, particularly those from Honda and Mitsubishi, just didn't have any charge motion at low pressure drops. Modern heads to not have this issue. You do sacrifice some flow for any charge motion, so some manufacturers have compromised with moderate valve angles and some sort of flap that will help charge motion at low pressure drops. Ford did this with the Coyote V8, it has "CMCV" plates or charge motion control valves.

We measure this now with a flow index. We have a tumble meter on the flow bench and we rate the heads by (flow*tumble)/valve size. You're looking to maximize tumble while still utilizing as much of the valve curtain area as possible with a given valve size. Mercedes are the absolute leaders in this, it's borderline witchcraft how good they've gotten at balancing this.
If it wasn't needed the manufacturers wouldn't be building it in.
The latest engines have DI so go by different rules to the port injected ones we are discussing.
Not true. The high performance Superbike engines do not have DI. Those applications are 12.5:1+ compression on pump gas and make north of 3hp/ci from the factory. no swirl to speak of, all tumble.

Read white papers on the Honda tech site. The manufacturers not only tune the axis of tumble, but also direct it to the center of the bore via the piston top.
I'm not sure where you're coming from really, you seem to have agreed and disagreed all in one? There is no swirl in a 4 valve, it's in a 2v.
What you'd call the biased motion in an unequal port/valve/cam 4v I dunno, swumble maybe?
In one of those papers Honda say they utilised steeper ports in conjunction with DI and used a shroud adjacent to the valve in the combustion chamber to change the flow direction.
There is no S on the end of RPM.

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Re: Theory of 4 valve poly quad cylinder heads.

Post by sbcharlie » Thu Sep 12, 2019 8:04 am

the Kawasaki kx450 head puzzle. first these bikes do very well in Moto cross racing. in flat track racing not so good. lots of people have tried to modify these heads and its seems its like safety porting these heads. seen where they welded or clay up the intake to increase port velocity . my views intake port no centered to the valves . over the years manufactures have made intake port a straight shot. the valve seat profiles are very odd. the contact seat width is .020. no critical angle above the seat. there is only one angle below seat, its at 86 degree, than contact 45 angle. what is strange the lower angle is oblong at 90 degree and 270 degree area to increase width in this area. these heads flow lots of air.... have a few months to figure out how to make these heads work . per AMA rules can not change valve diameter, I like to go smaller valve

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Re: Theory of 4 valve poly quad cylinder heads.

Post by LoganD » Thu Sep 12, 2019 12:30 pm

Truckedup wrote:
Wed Sep 11, 2019 7:40 pm
LoganD wrote:
Wed Sep 11, 2019 10:36 am
hoffman900 wrote:
Wed Sep 11, 2019 9:29 am
A lot of this is why I think performance on the 4 valve conversion heads suffer, just lack of knowledge of how these heads work.

Would love to see someone rip off a modern Sport bike head (like a Ducati twin, with a 4.5” bore) and apply it to a pushrod V8 shortblock. Obviously it would cost a fortune, but the head would be billet and the valvetrain would be the same design and all OTS.
I mean, bolt on Coyote's are making 500 whp on regular pump fuel. People are going 9's in Coyote stock (sealed factory stock engines). Making 700 hp from a Coyote is not hard. The aftermarket frequently makes two mistakes:

1. Deleting VVT, the Coyote's biggest advantage
2. Improperly degreeing aftermarket camshafts (a big mistake). You can't just install aftermarket cams and go with a DOHC design as your actual cam timing is dependent upon how they are installed.
I know it's easier to make more power per inch with a smaller engine and bike emissions are a bit easier than cars...But the bikes roll out the showroom floor with 3 plus hp per cubic inch...And the best two cylinder Ducati sport bikes have cylinders as large as a Coyote and make far more power per cylinder stock than a modified Coyote....
It's really about revs, and you can't make a passenger car engine rev like a bike and pass emissions and have acceptable NVH. Bike owners are willing to tolerate a lot more noise and vibration than car owners, and bike emissions are WAY easier than vehicle emissions. There's also the giant issue of maintenance, again bike owners are MUCH more willing to deal with higher maintenance than car owners.

Porsche have just about hit the limit with the current GT3 RS engine, they're making well over 2 hp/ci but have emissions and NVH that destroy any bike engine.

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Re: Theory of 4 valve poly quad cylinder heads.

Post by ptuomov » Thu Sep 12, 2019 10:24 pm

LoganD wrote:
Wed Sep 11, 2019 9:20 am
Modern turbocharged engines run a huge amount of tumble. Not only does this help with mixture uniformity, it actively cools edges in the cylinder and prevents hot spots. It's like....having a fan on the inside of the cylinder before combustion starts.

This is true even for port injected engines, probably the best production example is the Ricardo designed McLaren V8. Those heads rate very high on the tumble index. The reason you don't see DI on superbikes is that they need all the valve area they can get and it's not possible to package central DI with their valve sizes and cooling jackets. As was stated earlier, superbike engines have quite a bit of tumble, although not as much as say....the new Civic Type R engine or A45 AMG engine.
Why is it beneficial to transfer heat from the cylinder walls, piston, and combustion chamber roof into the charge on a pump gas, knock limited engine? This is not a rhetorical question.

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Re: Theory of 4 valve poly quad cylinder heads.

Post by gruntguru » Fri Sep 13, 2019 12:15 am

hoffman900 wrote:
Tue Sep 10, 2019 6:45 am
gruntguru wrote:
Tue Sep 10, 2019 12:08 am
GARY C wrote:
Mon Sep 09, 2019 10:44 pm

It seems like swirl would just force the fuel out of suspension and onto the cylinder walls.
There must be several billion 2 valve engines with swirl out there.
We’re talking about 4 valve powersport application with power goals of 2.5hp/ci here. Not truck engines.
OK. So "swirl will force the fuel out of suspension and onto the cylinder walls" on a four valve powersport engine but not a truck engine. Silly me.

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Re: Theory of 4 valve poly quad cylinder heads.

Post by Truckedup » Fri Sep 13, 2019 6:52 am

LoganD wrote:
Thu Sep 12, 2019 12:30 pm
Truckedup wrote:
Wed Sep 11, 2019 7:40 pm
LoganD wrote:
Wed Sep 11, 2019 10:36 am


I mean, bolt on Coyote's are making 500 whp on regular pump fuel. People are going 9's in Coyote stock (sealed factory stock engines). Making 700 hp from a Coyote is not hard. The aftermarket frequently makes two mistakes:

1. Deleting VVT, the Coyote's biggest advantage
2. Improperly degreeing aftermarket camshafts (a big mistake). You can't just install aftermarket cams and go with a DOHC design as your actual cam timing is dependent upon how they are installed.
I know it's easier to make more power per inch with a smaller engine and bike emissions are a bit easier than cars...But the bikes roll out the showroom floor with 3 plus hp per cubic inch...And the best two cylinder Ducati sport bikes have cylinders as large as a Coyote and make far more power per cylinder stock than a modified Coyote....
It's really about revs, and you can't make a passenger car engine rev like a bike and pass emissions and have acceptable NVH. Bike owners are willing to tolerate a lot more noise and vibration than car owners, and bike emissions are WAY easier than vehicle emissions. There's also the giant issue of maintenance, again bike owners are MUCH more willing to deal with higher maintenance than car owners.

Porsche have just about hit the limit with the current GT3 RS engine, they're making well over 2 hp/ci but have emissions and NVH that destroy any bike engine.
Do the 700 HP Coyote engines meet noise and emission control standards? With bikes it's not accepting more noise and vibration ,it's a whole different vehicle that is far more of a mechanical expereince than a car...New bikes have Cat convertors and sound quieter that the burbly exhaust of late model muscle cars or PU trucks. And I might be wrong, but isn't wide open throttle power excluded from emision standards? More maintence is true with Ducatis but not so much with Japanese sport bikes ridden with some sanity..
But to be honest comparions like this are never really valid...
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Re: Theory of 4 valve poly quad cylinder heads.

Post by ptuomov » Fri Sep 13, 2019 7:23 am

gruntguru wrote:
Fri Sep 13, 2019 12:15 am
hoffman900 wrote:
Tue Sep 10, 2019 6:45 am
gruntguru wrote:
Tue Sep 10, 2019 12:08 am
There must be several billion 2 valve engines with swirl out there.
We’re talking about 4 valve powersport application with power goals of 2.5hp/ci here. Not truck engines.
OK. So "swirl will force the fuel out of suspension and onto the cylinder walls" on a four valve powersport engine but not a truck engine. Silly me.
Maybe it's diesel vs, gasoline. Or that tumble is better than swirl but swirl is better than no motion.

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Re: Theory of 4 valve poly quad cylinder heads.

Post by hoffman900 » Fri Sep 13, 2019 8:51 am

gruntguru wrote:
Fri Sep 13, 2019 12:15 am
hoffman900 wrote:
Tue Sep 10, 2019 6:45 am
gruntguru wrote:
Tue Sep 10, 2019 12:08 am
There must be several billion 2 valve engines with swirl out there.
We’re talking about 4 valve powersport application with power goals of 2.5hp/ci here. Not truck engines.
OK. So "swirl will force the fuel out of suspension and onto the cylinder walls" on a four valve powersport engine but not a truck engine. Silly me.

I mean, If you want to change the ports on something already developed to make 2.5-3+ hp/ci to add swirl, then give it a shot.
-Bob

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Re: Theory of 4 valve poly quad cylinder heads.

Post by LoganD » Fri Sep 13, 2019 8:58 am

ptuomov wrote:
Thu Sep 12, 2019 10:24 pm
LoganD wrote:
Wed Sep 11, 2019 9:20 am
Modern turbocharged engines run a huge amount of tumble. Not only does this help with mixture uniformity, it actively cools edges in the cylinder and prevents hot spots. It's like....having a fan on the inside of the cylinder before combustion starts.

This is true even for port injected engines, probably the best production example is the Ricardo designed McLaren V8. Those heads rate very high on the tumble index. The reason you don't see DI on superbikes is that they need all the valve area they can get and it's not possible to package central DI with their valve sizes and cooling jackets. As was stated earlier, superbike engines have quite a bit of tumble, although not as much as say....the new Civic Type R engine or A45 AMG engine.
Why is it beneficial to transfer heat from the cylinder walls, piston, and combustion chamber roof into the charge on a pump gas, knock limited engine? This is not a rhetorical question.
Hot spots act like a spark plug. Controlling hot spots is more important than an increase in pre-combustion air temp. On modern high-BMEP production engines there's also the issue of material longevity, this is an issue particularly on the exhaust side.

This is the same reason they use oil squirters on pistons.

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Re: Theory of 4 valve poly quad cylinder heads.

Post by ptuomov » Fri Sep 13, 2019 9:03 am

LoganD wrote:
Fri Sep 13, 2019 8:58 am
"Why is it beneficial to transfer heat from the cylinder walls, piston, and combustion chamber roof into the charge on a pump gas, knock limited engine? This is not a rhetorical question."

Hot spots act like a spark plug. Controlling hot spots is more important than an increase in pre-combustion air temp. On modern high-BMEP production engines there's also the issue of material longevity, this is an issue particularly on the exhaust side.

This is the same reason they use oil squirters on pistons.
Ok, so if the problem is low speed preignition, I can see how more tumble is better. If the problem is spark knock, then more tumble is not necessarily always better.

If so, for downsized passenger car engines, or engines running very high octane fuel, more tumble the better. For a "tuner engine" running on pump gas and making power at higher rpms, there may be a point where more tumble is no longer better.

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Re: Theory of 4 valve poly quad cylinder heads.

Post by hoffman900 » Fri Sep 13, 2019 10:39 am

ptuomov wrote:
Fri Sep 13, 2019 9:03 am
LoganD wrote:
Fri Sep 13, 2019 8:58 am
"Why is it beneficial to transfer heat from the cylinder walls, piston, and combustion chamber roof into the charge on a pump gas, knock limited engine? This is not a rhetorical question."

Hot spots act like a spark plug. Controlling hot spots is more important than an increase in pre-combustion air temp. On modern high-BMEP production engines there's also the issue of material longevity, this is an issue particularly on the exhaust side.

This is the same reason they use oil squirters on pistons.
Ok, so if the problem is low speed preignition, I can see how more tumble is better. If the problem is spark knock, then more tumble is not necessarily always better.

If so, for downsized passenger car engines, or engines running very high octane fuel, more tumble the better. For a "tuner engine" running on pump gas and making power at higher rpms, there may be a point where more tumble is no longer better.
I think Logan’s posts are super interesting on this ratio of flow vs tumble. The McLaren engine is really awesome. 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.
-Bob

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