Grooves in heads/cylinders: Snake Oil or a Good Idea?

[rags]

I searched the web and never found an answer. Does it have to do with the reduced area of the combustion chamber when the charge is ignited or because of the increased movement of the charge into the area of ignition?

[HowlerMonkey]

A sequential injector scheme with a very good spray pattern would reduce the need for turbulence in the combustion chamber.

 

Eventually somebody will go Direct injection making turbulence a non-issue.

 

I wonder when the GM direct injection systems will start showing up in junkyards.

[rsicard]

There are two reasons for detonation. Quench or squish surpresses detonation by way of mixture turbulence the more squish the more turbulence and the faster and more completely the mixture in the cylinder will be burned. The faster the mixture burns, the less BTDC timing lead is needed to achieve the power pressure peak at approximately 12-15 ATDC. Timing lead BTDC and progressive burn from spark ignition is a time of NEGATIVE WORK. The less timing lead needed for the same power pressure peak in the cylinder. Therefore LESS NEGATIVE WORK (more power?).

[JMortensen]

There are two reasons for detonation. Quench or squish surpresses detonation by way of mixture turbulence the more squish the more turbulence and the faster and more completely the mixture in the cylinder will be burned. The faster the mixture burns, the less BTDC timing lead is needed to achieve the power pressure peak at approximately 12-15 ATDC. Timing lead BTDC and progressive burn from spark ignition is a time of NEGATIVE WORK. The less timing lead needed for the same power pressure peak in the cylinder. Therefore LESS NEGATIVE WORK (more power?).

Sounds good, but I don't think that is exactly right. Quench does produce turbulence which can lower the amount of timing needed to get max power. You'll occasionally hear people say that they run less because they have a high quench head, but I've heard of Datsun racers running LOTS of timing and saying that they make more power that way. I think Dennis Hale was running in the mid to high 40's when it was all in, and the curve kept on going as the rpms get higher, as opposed to your usual mid 30's all in by 2500 rpm. Dennis's engine in his autox 510 is the hottest build Rebello does, so you know it's a high quench setup. I can't recall the compression ratio, but it's got to be 14 or 15:1. I think zredbaron was running a hell of a lot of timing on his setup too.

[rsicard]

Sounds good, but I don't think that is exactly right. Quench does produce turbulence which can lower the amount of timing needed to get max power. You'll occasionally hear people say that they run less because they have a high quench head, but I've heard of Datsun racers running LOTS of timing and saying that they make more power that way. I think Dennis Hale was running in the mid to high 40's when it was all in, and the curve kept on going as the rpms get higher, as opposed to your usual mid 30's all in by 2500 rpm. Dennis's engine in his autox 510 is the hottest build Rebello does, so you know it's a high quench setup. I can't recall the compression ratio, but it's got to be 14 or 15:1. I think zredbaron was running a hell of a lot of timing on his setup too.

Well, if they are running as much as 40 degrees lead timing, they DEFINITELY NOT have fast burn in the cylinder chambers. Suggest reading David Vizard's books and articles as I have been following these CLOSELY. Mr. Vizard does A LOT of testing to prove theories concerning Internal Combustion Engines. He has several books out regarding building HIGH PERFORMANCE engines on a BUDGET. He works together with T & L engines in North Carolina and they build some of the most powerful Small Block Chevrolet V8's. One would think that Robello would select cylinder heads with the best quench/squish and then order from JE pistons a custom piston to enable best quench/squish. If not, they are BEHIND the times as this is exactly what GM has done on their latest Corvette/Camaro engines in addtion to enhancing intake mixture flow.

[JMortensen]

Well, if they are running as much as 40 degrees lead timing, they DEFINITELY NOT have fast burn in the cylinder chambers. Suggest reading David Vizard's books and articles as I have been following these CLOSELY. Mr. Vizard does A LOT of testing to prove theories concerning Internal Combustion Engines. He has several books out regarding building HIGH PERFORMANCE engines on a BUDGET. He works together with T & L engines in North Carolina and they build some of the most powerful Small Block Chevrolet V8's. One would think that Robello would select cylinder heads with the best quench/squish and then order from JE pistons a custom piston to enable best quench/squish. If not, they are BEHIND the times as this is exactly what GM has done on their latest Corvette/Camaro engines in addtion to enhancing intake mixture flow.

Your response is too absolute. Do you think it's even possible to get 14 or 15 to 1 compression and not have quench? I'm not sure that it is. I know that Sunbelt cut the chamber up and fit the piston to the chamber to get quench when they built John Coffey's head, and his motor was ~13:1. Not sure, but I would suspect that a hot Rebello L16 that was $20K+ would be running the 219 head which has 1.5" ports out of the box and a closed chamber, but I don't know that for sure. I would suspect that regardless of the chamber they're using or how it is modified, the piston has to be so close to the head that there would have to be quench just to get the compression that high. I think it's pretty unwise to ASSume that they don't.

[rsicard]

Your response is too absolute. Do you think it's even possible to get 14 or 15 to 1 compression and not have quench? I'm not sure that it is. I know that Sunbelt cut the chamber up and fit the piston to the chamber to get quench when they built John Coffey's head, and his motor was ~13:1. Not sure, but I would suspect that a hot Rebello L16 that was $20K+ would be running the 219 head which has 1.5" ports out of the box and a closed chamber, but I don't know that for sure. I would suspect that regardless of the chamber they're using or how it is modified, the piston has to be so close to the head that there would have to be quench just to get the compression that high. I think it's pretty unwise to ASSume that they don't.

Jon: Quench/Squish is ALL IMPORTANT. The small the chamber in the head the better. But to go along with this, the chamber and piston should have a FLAT area between the two and an unobstructed path for FAST flame travel. I don't know Sunbelt, am somewhat familiar with Rebello, but that does not mean that either of these has adopted MODERN combustion methods. David Vizard is using CUTTING EDGE proven combustion methods.

 

Strongly suggest researching David Vizard's methods first and giving them adequate thought.

[johnc]

David Vizard is using CUTTING EDGE proven combustion methods.

 

Vizard is behind the curve. For cutting edge combustion chamber design you need to look at F1 and MotoGP where they are getting around 35% thermodynamic efficiency from a normally aspirated gasoline powered ICE.

[JMortensen]

Jon: Quench/Squish is ALL IMPORTANT.

Right. That's why the 1000 hp Skyline motor builders cut the quench pads out of the chamber on one side. Again you're too absolute.

[rsicard]

Right. That's why the 1000 hp Skyline motor builders cut the quench pads out of the chamber on one side. Again you're too absolute.

Did not expect John C to chime in. I should have specified the type of ICE that I am talking about. That is NORMALLY aspirated, PUSHROD activated, two valve WEDGE head production engines. The kind that NASCAR uses NOT formula 1 NOR Supercharged/Turbocharged engines. Can't compare apples to oranges.

[JMortensen]

Did not expect John C to chime in. I should have specified the type of ICE that I am talking about. That is NORMALLY aspirated, PUSHROD activated, two valve WEDGE head production engines. The kind that NASCAR uses NOT formula 1 NOR Supercharged/Turbocharged engines. Can't compare apples to oranges.

So since the L head is not pushrod driven, does that mean your rules don't apply?

 

I fully agree with you about what is usually right, by the way. I just think you're not leaving any room for other ideas at all. I know those motors are high quench motors, and they have found power on the dyno by experimenting with the timing. When I heard about it I was pretty surprised too, but hey, experience > theory.

[rsicard]

So since the L head is not pushrod driven, does that mean your rules don't apply?

 

I fully agree with you about what is usually right, by the way. I just think you're not leaving any room for other ideas at all. I know those motors are high quench motors, and they have found power on the dyno by experimenting with the timing. When I heard about it I was pretty surprised too, but hey, experience > theory.

With ALL due respect to John C and yourself, I did not expect such rash answers. John C is one of the best fabricators and one great asset to Hybridz. You are also an asset to Hybrid Z. I forgot that the L6 is an overhead cam ICE. Yet it is a dated design. I tend to follow David Vizard and the newest GM Corvette/Camaro and Dart designed cylinder heads. GM uses Computation Fluid Dynamics (CFD) and perhaps flow bench simulations to validate CFD designs. I would expect Formula 1 engine designers to use CFD also but those are 4 valve per cylinder dual overhead cams with pneumatically actuated valves. Therefore the comment concerning comparing apples to oranges. Dart has designed cylinder ports and chambers based on extensive flow bench and windows on the flowing ports.

 

I don't think that anybody, other than the designer, that grooves in the quench/squish portion of the cylinder head toward the spark plug has been closely investigated by way of Flow Bench simulation SIMILAR to what Dart Cylinders heads is doing. They actually use a fluid similar in viscosity to gasoline that illuminates under black lamp through a window in a test port. There is only one firm that I know, based in Texas, that can data record the combustion pressure pulse in a firing cylinder head compared to the angle of the crankshaft and camshaft. The actual mapping of mixture swirl, quench/squish, tumble and their effects to my mind may be still in its infancy. But Dart, AFR and F1 engine designers have the most amount of experience in designing cylinder heads.

[johnc]

The current research direction is away from spark ignition and more towards Controlled Auto Ignition (or CAI), Homogeneous Charge Compression Ignition (HCCI) at least for steady state cruise. This should push the thermodynamic efficiency of normally aspirated gasoline engines close to or beyond the current F1 level of efficiency. And we'll be seeing combustion chamber designs very different then what we're used to looking at now.

[rsicard]

The current research direction is away from spark ignition and more towards Controlled Auto Ignition (or CAI), Homogeneous Charge Compression Ignition (HCCI) at least for steady state cruise. This should push the thermodynamic efficiency of normally aspirated gasoline engines close to or beyond the current F1 level of efficiency. And we'll be seeing combustion chamber designs very different then what we're used to looking at now.

John: Where can I research via the internet on CAI and HCCI? Please advise. Thanks.

[johnc]

http://www.sae.org

[rsicard]

http://www.sae.org

John: Having been in the Design and Certification portion Aviation Electronic Industry for 38+ years I have been down the SAE road before. The statement "And we'll be seeing combustion chamber designs very different then what we're used to looking at now" is a WAITand SEE statement. GM and Dart have been doing much work on PRODUCTION cylinder heads and have been getting proficient at it. GM also has been experimenting FVVT valve trains. It is conceivable to imagine present combustion chamber designs advanced further through Dart Cylinder Heads flow bench with a WINDOW on Flow Characteristics. Just happens that Dart is in Troy Michigan within the greater Detriot area. Therefore, information and data may be shared between GM and Dart. It also somewhat easy to see that valve timing will be controlled electronically in the future. Microprocessors are getting faster all the time. I would guess that Fully Variable (Electronically controlled) Valve Trains are already being tried at GM. To inject EGR as varying rates will be easy with Electronics Controls. Just need some very experienced embedded apps Engineers/Designers.

[Careless]

lola engine management, here we go

[Xnke]

Rsicard, google the EVIC mk1. The "electronic camshaft" has been done by a total amateur QUITE a while ago, and works, the limitations are solenoid heating plus valve pulsewidths. BTW, the EVIC models run over 10K rpm, and you can run them with absolutely NO throttle plate whatsoever. Just vary the intake valve timing, and GO!

 

Anyway, the fully variable valve timing has also been done on a full sized engine, we did it on an old 327 in the engineering department at the college I used to go to. GM's corvette plant is across town, and we did a LOT of work with the go-fast team that works there. Again, the problems we ran into were solenoid minimum pulsewidths that still allowed for valve control, dumping enough current to activate the solenoid without burning it up, and still being able to overcome the valve springs fast enough.

 

Biggest downside was the heads we were modifying didn't really have much room to mount the solenoids we used, and the ones we used really were not powerful enough to fully control the valve, it's gonna take some serious effort to really get that kind of thing under control.

[rsicard]

Xnhe: Thanks very much for your post. Did as you said and googled EVIC mk1. VERY interesting. I know the concept has been proven. Now it is a matter either electromagnetic/electronic, pneumatic/electronic or hydraulic/electronic control and actuation of the engine valves. The other difficulty with PRODUCTION of this concept is the software executive loop times MUST be very fast in order to accommodate the upper RPM ranges. The software will have to contend with the delays from signal activation to actual activation of the valves.

[roger280zx]

Back to the grooves. My fathers 13.5:1 283 had "Flame Trails" on the piston domes and chambers. That thing was built in the early seventies, but stories told about it say that it idled smoother than stockers and ran low 12s in a '55 chevy wagon with absolutley no weight reduction.