My Road Trip Motor Progress

[rick m]

ZACH....the truth of the matter is we are not settling on anything but what we know works.  Run what you like...There is really no argument because we are simply running what we have done and seen be efficient. We are not the only ones who have done this.  GM, DODGE, FORD and many other automotive engineers have designed motors and understand the benefits of the open chamber design.

Again, break out of that 7 to 1 compression paradigm being the only reason someone did a hemi type/open chamber head.  Neither Joel or myself is advocating that. In fact, I may even bump up my compression to 9.5 due to the K8 cam and overlap.   :-)

Rick M

[65bug]

Rick,
    Very interesting thread. I look forward to hearing how your motor runs! Should be a great runner with plenty of usable power. ZACH is on the cocktail train again! Keep us posted!




Thank you

[Zach Gomulka]

Relax fellas, it was a joke! Thanks for proving my point though, you just can't joke about religion, politics, or hemi-ing your VW chambers without someone getting their panties in a wad.

I'd still love to know why the engineers at Chrysler designed the modern hemi engine like this, if a true hemi is where it's at. Perhaps you know something they don't.

[Stripped66]

I'd still love to know why the engineers at Chrysler designed the modern hemi engine like this, if a true hemi is where it's at. Perhaps you know something they don't.

A true hemi is not necessarily "where it's at", nor is anybody arguing so. The combustion chamber shape is always going to be a compromise between quench, valve shrouding, valve clearance and volume (compression ratio). Why did Chrysler design their current head with a pentroof chamber instead of a true hemi chamber? For starters, the increase in chamber volume with a true hemi would decrease the compression ratio, and attempting to deck the head to reduce chamber volume would expose the intake valve seat and decrease the available valve to piston clearance. Compare that to a Porsche 911 chamber (aircooled). Why did they use a true hemi?

Joking or not, why do you insist on being contentious?

Read more: http://www.corvettefever.com/techarticles/corp_0611_chevy_big_block_cylinder_heads_pcv_valves/viewall.html#ixzz23YaGZQUT

While I am not a proponent of the semi-hemi chamber in our VWs, the open chamber Rick points us to in this article is a great example of where to open the chamber: behind the spark plug. One problem I see with the semi-hemi modification is opening the chamber opposite to the spark plug which increases the distance that the flame-front will travel; biasing the unshrouding and semi-hemi cut on the spark-plug side should mitigate this. However, having gone from a 12:1 CR, Supersquish piston, 91 octane engine to a 9:1 CR turbo engine with a lot of boost, I'm certainly rethinking the influence of my current chamber shape as I have a ton of deckheight (~.200"), reducing the effectiveness of my Supersquish pistons:

I could lay back the combustion chamber on the spark plug side to pick up more volume and reduce the deckheight to something marginally acceptable. 

[Zach Gomulka]

I am truly looking forward to your results, Rick. Especially if all other factors remain the same, especially deck height and compression. Otherwise, this conversation is a moot point.

[rick m]

Zach....agreed.  My whole intent was not to change everything on my motor.  Just go back to the open chamber quench set up I ran in my 2110. I will post my results once back up and running.

RM

[OC1967vw]

Stripped66,
great perspective on your openess to thinking about people improving on those techniques that have been known to work over the years and current applicability.

Many thanks to RickM and Joel for continuing to take the research and theory and convert it to the real world-in both their own motors, in Rodgers' motor description (especially at that elevation) and performance, and the Bulitta motor, Clyde's work over the years. It seems to me that the evidence is very substantial that this "new way" is a substantial performance improvement.

For those who question, congrats to you for raising the questions for it sharpens the work and effort that Joel and RickM have undertaken and will continue to do. While you may not agree with or accept their work, the reality is that their effort is the evolution of and improvement on conventional thinking. Thats a good thing. Its like looking at a 1965 Porsche 911 and 2012 Porsche 911-same original design theory but substantial improvement and evolution through the years.

Looking forward to seeing the results on the road

[Fastbrit]

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[K-Roc]

.

Exactly !  

[rick m]

Keith...no input??? :-)

RM

[Fastbrit]

Nope...

But I do recall the comment of an F1 race engineer friend of mine when viewing the engine in the Chop-Top: 'You do realise that for as long as you guys insist on running carburettors, two valves, single plugs and no management system, anything you might plan on doing with the engine is the technological equivalent of rearranging the deckchairs on the Titanic. It ultimately serves no real purpose.' Harsh, but it made me smile!

[Fasterbrit]

Keith, we are always faced with a certain 'prejudice' towards out humble flat fours. Curiously, we can easily make over 200 horsepower with, wait for it... carbs, two valves per cylinder and a crappy old distributor.

Cosworth engineers, spent millions on developing 16V heads, fuel injection, Cdi ignitions, complex management and a turbocharger to produce just 220  horsepower out of 2 liters when they souped up the Sierra.  The result? a car that struggles to do a fourteen second quarter in standard trim...

I bet, if your F1 guy watched our drag racers pitch up against all of today's supercars, he would dine out on his flat cap. 

Bugatti Veyron: 1000 hp, 4-wheel drive... half a second slower to the quarter than my old 2.1 liter Waterboxer from a 1980's VW Van, of all things.

As they say, the bullshit stops when the checkered flag drops 

[Fastbrit]

Keith, we are always faced with a certain 'prejudice' towards out humble flat fours. Curiously, we can easily make over 200 horsepower with, wait for it... carbs, two valves per cylinder and a crappy old distributor.

Cosworth engineers, spent millions on developing 16V heads, fuel injection, Cdi ignitions, complex management and a turbocharger to produce just 220  horsepower out of 2 liters when they souped up the Sierra.  The result? a car that struggles to do a fourteen second quarter in standard trim...

I bet, if your F1 guy watched our drag racers pitch up against all of today's supercars, he would dine out on his flat cap. 

Bugatti Veyron: 1000 hp, 4-wheel drive... half a second slower to the quarter than my old 2.1 liter Waterboxer from a 1980's VW Van, of all things.

As they say, the bullshit stops when the checkered flag drops 

I don't think you need to tell me of the flat-four's capabilities after all these years.  But what your argument does forget is that you're comparing a "slightly" modified VW to a production car. Wonder what the guys at Bugatti/VW would do if they built a purpose-built Veyron drag car? Also, the Sierra of which you speak is 25 years old – and, more importantly, was designed to a) meet certain emissions regs and b) drive a lot further at max rpm than 440yards. There's really no point in comparing the two and, as we all know, we have nothing to prove.

Perhaps a fairer comparison would be take take a stock 1600 GT Beetle and compare with a stock RS1600 Escort – same era and same engine cc. 

[Fasterbrit]

25 years ago is like yesterday... The So-Cal boys were running elevens forty years ago  Albeit a quarter mile per rebuild 

You're right about comparing apples with oranges, though. My point was mainly about the prejudice we always seem to face among racing 'peers'... They always seem to knock the VW even when it kicks their ass! 

Matt

[OC1967vw]

RickM,

appreciated your thinking. Could not agree more. Key point is longevity on the street. Keep up the thread.
Thanks to you and Joel for bringing fresh thinking into this enhancement and expansion of VW aircooled performance thinking

[Zach Gomulka]

Stripped, I understand there is a compromise involved. Isn't there with anything we modify? The Chrysler and Porsche engineers could (and did) easily get their CR back up with domed pistons. Not so easy for us...

There are aspects of this that I do like. Even pressure across the piston. And the ability to flycut the heads can make a wide stroker motor much more easy to deal with. Years ago, CB told me you could safely flycut .140" off an 044 casting. That's huge! I wonder what a "open chamber" flycut down .140" would CC at? Dish the pistons if needed, valve pockets of course. Stock width 2387cc N/A street motor sounds very feasible.

I still doubt that a single plug can efficiently light off a wide chamber like that. Twin plugs would really wake it up.

The first motor I built was semi hemi cut, and fly cut. And throughout the years, the only thing that more than 32° timing has done for me is make the engine much more difficult to start.

And as for me being contentious? For my amusement, purely

[rick m]

More food for thought from the website 351.net where V8 guys are sharing input on combustion chamber designs:

The 351C open combustion chamber head is superior to any wedge combustion chamber design. It makes as much power as the quench chamber version … its not prone to detonation any more than the quench chamber version. Poly-heads don’t depend upon squish for their power and resistance to detonation, those characteristics are achieved by the shallowness and poly-angle shape of the combustion chamber.

The 351C chamber is very shallow, the valve angles are merely 9-1/2 degrees. There is no dead space. The chamber cross-section is not wedge shaped. This shape evenly distributes the flame front over the entire surface of the piston dome.The best intake port in the world feeding a mediocre combustion chamber will not make big horsepower

Engine designers realize the combustion chamber is the heart of an internal combustion engine. The best designed intake port in the world cannot produce superior torque and horsepower if it is supplying fuel and air to a cylinder with a poor or average combustion chamber. The 351C had the highest volumetric efficiency of any mass produced push-rod (OHV) V8 not solely because it had well designed ports and large valves, but also because it had a well designed combustion chamber. Although it may not be intuitive, what you are looking at in the picture below is one of the best performing combustion chambers of any mass produced push-rod V8.

Look closely at the 351 head and then what Joel, I and others are doing with the open chamber VW head designs we are working with. Keep in mind you do not want a lot of deck.  I run "0" deck with a copper gasket.  I know Joel is running a tight deck too.  First we get the design, then we get the CC's we need...and then we assemble.  My personal decision of going to an open chamber design has come after hours and hours of researching VW and V8 heads and not to run low compression.  My focus is on going for efficiency in the head and the flame travel and pressure being applied across the entire piston.

Zach....with a tight deck and the correct cc in the head....you can get good flame travel with an MSD or any other hi energy ignition.  Ignition and spark intensity are important with these type combinations. The 351 motors did not run dual spark and they made great power.

Rick M

[Zach Gomulka]

I think those 351C guys are SEVERELY biased! I find it very hard to believe that the pinnacle of combustion chamber design was reached over 40 years ago. I am no head guy, but that picture does not impress me. Just look at that intake valve! Another thing the high compression 351C engines used (just like Porsche and Chrysler)... Domed pistons.

If you're limiting yourself to pushrod V8 designs, look at the most modern Neanderthal of the bunch, the GM LS series.

[rick m]

:-)..... Fun discussion....but I will not be running a computer, knock sensors, an engine management system or controlled spark timing like all the new stuff. Can't wait to get my together....

Rick M

[Zach Gomulka]

I wish you luck, and hope you prove me wrong. Too bad we're too late for a before/after dyno test.

[Joel Mohr]

Had a VERY interesting trip to the Monterey Historics this past weekend (Thanks again Don and Bill!). Talked to a Ford engineer about the NEW Cobra motor, and it's a 2 valve, full hemi. They tried a partial hemi, (he actually showed me a pic on his personal phone of the prototype) with squish area on both sides, and then re-tooled to make it a full hemi. 11.5 to 1 on pump gas and the full hemi made 10 % more power... And to top things off, I went through the pits to find out what most of the performance motors had for heads, and about 70 % were hemi or domed shaped with little or no squish, both 2 and 4 valve...even a 3 valve...and yes, regardless of age...

[rick m]

Zach....don't have to prove anything. It is already being done. I am not experimenting...I am implementing the hours and technology others have already found out works. Joel....your post confirms what a die hard FORD guy, one of my repair technicians, shared with me.  My heads are being flycut right now and I pick them up tomorrow.

Rick M

[Fasterbrit]

Rick, will you post a pic of the final combustion chamber shape post machining? I would be very interested to see the outcome and maybe even apply it to my next motor. I like and respect what you guys are doing - there's always alternatives that work, it just takes people to think outside the box a little. If the hemi style chamber hadn't worked, it would have been dumped years ago. Hell, even my Yamaha Rd500 (Rz500 in the US) two stroke V4 has domed type chambers and that seems to work very nicely.

Your findings regarding cooling and CR are very interesting. Less heat and pinging at the same CR has to be applauded. 

Regards, Matt

[rick m]

Matt,

I will take some shots this weekend as I start laying out the parts for assembly.  The chamber design on the first shot of this thread has not changed.  We just flycut the heads more to arrive at the 9.0 to 1 that I want to run.  I am running a .050 copper head gasket on the motor and setting the pistons to "0" deck before the copper gasket. Static compression should end up around 9.0 and dynamic compression around 8.0, based upon when my valve closes fully.

http://www.kb-silvolite.com/calc.php?action=comp

Attached is a great tool that Texas Tom sent to me.  I would recommend using it.  It is a great way to figure out the true compression when valves are closed all the way.  It takes into consideration rod angle, stroke, bore, gasket thickness and inside gasket bore diameter (copper gasket), valve timing and deck height.  I love the tool and have used it setting up my current motor.

Rick M

[Donny B.]

Yeah Rick, I just used that site to do an actual calculation on my engine.  It is set at 8.3 static and 7.0 dynamic.  I knew that it was just over 8 to 1, but now I know for sure.

[rick m]

Yeah...I really like how it takes into consideration the rod length, head gasket thickness, the actual valve closing and other critical measures.  It really helps dial things in. Texas Tom turned me on to it.  I will use it on all my motor combos now.

Rick M

[K-Roc]

Dynamic compression ratio changes through out the RPM range and the calculators have no way of knowing your true VE at a specific RPM
( unless you have this info from testing and can plug it in)  so unfortunately those calculators don't turn out to be that accurate. Still an OK tool but I wouldnt put too much faith in them.

We use Kiestler in cylinder pressure transducers  in all our dyno cells at Westport but for the average tuning shop they are quite expensive.
about 3-4 grand per cylinder with amplifier....
This is really the only way to get the actual dynamic cylinder pressure.

We now have 13  test cells at the vancouver location including 1 CVS dilution tunnel  that cost a cool 4.5 mil. 




 

[Fasterbrit]

Rick, thanks for the link 

Very useful tool that gives us a better understanding of true CR and for free!  Playing around with specs; It's interesting to watch your CR bleed off with more cam overlap... That's why 'big' cams need big CR.

[Jon]

Less heat and pinging at the same CR has to be applauded.

Less heat shows that there is less energy produced... And that is great for the street.

The more alu you remove from the head the hotter the rest of the remaining alu will be, I believe.

I used to believe that valve unshrouding was done to improve flow through the seat, and that you stopped once the numbers dropped of. If you keep going you will in the end have a flathead. I believe that the word hemi comes from how the head looks like after optimal unshrouding of valves (when the valves are close to 45 degrees apart). The powers of the actual word hemi is limited to the marketing department IMHO.

But like its being said, anything can be made to work with enough effort.  But can anything be made to work best
I must say there are some confusing things said in this thread, like a slow burn is not necessarily a bad thing.

I would love to run 911 heads on my engine... But not because they look like hemi's, ....but because they flow like hell.

[Stripped66]

I must say there are some comfusing things said in this thread, like a slow burn is not nessisarily a bad thing.

Agreed, especially since little context has been provided to validate the opinion. A slow burn isn't necessarily a bad thing if your timing has been optimized with respect to that characteristic, and the rise in cylinder pressure/heat does not ouptace the flame-front and cause detonation. A slow burn isn't necessarily a bad thing due to lean, high AFR at partial-throttle cruise. Too many generalizations...