Chamber Grooves - what do you guys think?

[greg_nate]

As always, testing shows the need for more tests! Great work though guys, have you noticed the 'view' count? Almost 15,000! You should have bought shares in a keyboard company!
One explanation of the torque gain would be that high RPM spark was pretty well optimized in the 'before' condition and thus gained nothing from a faster burn, as the spark became over-advanced, whereas at lower RPM it was slightly retarded and thus gained from both faster burn and optimized spark.
If the chance comes again, you might consider either tweaking spark to MBT before and after, or even backing off a few degrees for the 'before', which advance should increase power with the grooves if the theory is correct.

I would be one of the lurkers that is part of the 15,000 views.

I have been researching this for a while now, and am eagerly awaiting results. I've been following automotive breath's posts all over the internet. My next head purchase and what I do with those heads will be decided by this thread.

Thank goodness for this forum.

[hotrod]

I have said before that these grooves must work, but after seeing actual dyno results the improvements were not as much as I had suspected.

As already posted more questions than answers, but it would be useful to keep in mind that this chamber modification may be very productive for one family of combustion chamber designs and of little consequence for another design.

Now all we need is about 30 more dyno tests like this to tie up the loose ends regarding what tuning changes might be most suitable for the grooved chamber.

It is clear based on this first pass at testing that it produceds some improvements in the low mid rpm ranges where detonation is most likely.

It would also vote for a detonation sensitivity test series, with timing and mixture optimisation for each head configuration.

Now all we need is time and money

Larry

[putztastics]

Following your strip/dyno plan (assuming the dyno has or can be fitted with decent no-loss muffling), after you baseline the no groove configuration, back down the timing and then work it back up to borderline detonation using low enough octane fuel that significant retard (5 -8 degrees) is required. Now when you repeat with the grooves, you can compare power at A. same (retarded from MBT) spark advance, B. knock-limited low octane power and C. high octane power, as well as comparing SA requirements.

I still don't know what MBT is - maximum brake torque?

However if you want to test timing changes to actual spark knock read this;

Knock Sensor Signal - Compatible w/ LM-1?

What Klaus says about making your own knock sensor makes sense to me. I have read other places the human ear can pick up spark knock long before electronics can. In fact I read where tests done showed a female human ear was better than electronics so natually an man's ear would be better still, right guys?

Here is another;

Ways to spot knock?

This is appealing to me as I listen to engines with a stethescope, what would be even better is a setup like this, besides detonation maybe you could hear a mechanical problem before pieces departed their assigned places.

[hotrod]

I still don't know what MBT is - maximum brake torque?

From my experience there appears to be two equally popular usages of the term MBT. For practical purposes they are nearly the same but in some usages like detonation limited operation there is significant difference.

Some use MBT to mean simply "maximum brake torque" which is pretty self explanatory.

The other useage appears to be to use MBT to mean "minimum best torque timing". For this they found the ignition timing that gave maximum torque and then retarded timing slightly so that torque dropped approximately 1%. The resulting timing provided a safe reliable tune.

Larry

[automotive breath]

…Here is another;

Ways to spot knock?

This is appealing to me as I listen to engines with a stethoscope, what would be even better is a setup like this, besides detonation maybe you could hear a mechanical problem before pieces departed their assigned places.

I find this interesting because the only other person that I know of that listens to an engine with a stethoscope is Somender Singh. The quality of fuel in India is very poor and toying with compression can be a challenge. His work with a stethoscope started this whole concept.

For what it’s worth, I’ll explain how I tune my car at the drag strip. First, I normally build my engines with a compression ratio between 10.7:1 to 11.2:1. With this compression, running 100-octane low lead is doable. First, I jet the carb from previous experience. With a 750 Holley in cool air, I go with 82 jets square. I guess at ignition advance starting lower than what I think it can handle. With a new set of plugs, I advance the timing until I see dark speckles on the plugs. I then retard the timing 1 to 2 degrees. Back to the jets, I get the engine H2O temperature to 140 degrees at the starting line (measured at the head) and watch the temperature gauge at the finish line. If the temperature climbs more than 10 to 15 degrees, I add more jet. If the temperature holds steady I take jet out. I never have a need to go more than two numbers in either direction. If I take jet out, I watch the plugs close for dark specks, when I see them I reduce timing or add jet.

Detonation problems normally show up a one of two places, first when leaving the starting line, secondly when I put it in high gear.

[MadBill]

From my experience there appears to be two equally popular usages of the term MBT. For practical purposes they are nearly the same but in some usages like detonation limited operation there is significant difference.

Some use MBT to mean simply "maximum brake torque" which is pretty self explanatory.

The other useage appears to be to use MBT to mean "minimum best torque timing". For this they found the ignition timing that gave maximum torque and then retarded timing slightly so that torque dropped approximately 1%. The resulting timing provided a safe reliable tune.

Larry

A little late getting back on this, but yes, the latter was my meaning: Minimum spark for Best Torque is an OEM industry standard term, as is LBT: Leanest fuel for Best Torque. After determining these for a new engine calibration on a dyno, spark is backed off and fueling enriched by some modest percent of torque loss as a safety cushion.

[automotive breath]

… MBT - Minimum spark for Best Torque is an OEM industry standard term, as is LBT: Leanest fuel for Best Torque. After determining these for a new engine calibration on a dyno, spark is backed off and fueling enriched by some modest percent of torque loss as a safety cushion.

MadBill, Can you explain the process of determining MBT and LBT on a dyno?

[MadBill]

It's explained in great detail in each OEM's procedures manuals but basically, using either 100 octane unleaded or the owner's manual-recommended fuel(s) (depending on what data is desired) at each RPM step point (normally the same steps as the entries for the ECM's main spark and fuel tables), and with controlled air, coolant and oil temperatures, etc., the spark is advanced until a specified (low) level of knock develops or no further power increases are seen, then in the latter case, backed off to the point at which a loss develops. This done using either the production fuelling rate or with LBT fuelling, again according to what test data is required. The procedure is done at each step point and usually repeated one or more times until a good average value for each has been obtained.

To determine LBT, the production spark timing (or MBT, again depending on requirements) is used, and the fuelling rate increased or decreased in the same manner, to determine minimum pounds per hour of fuel flow at maximum power for that RPM and BSFC. (Brake Specific Fuel Consumption)

In the case of LBT & MBT together, 'loops' of fuel and spark adjustments are carried out until the optimum combination is found for each test point.

[liquigas]

Can you post closeups of the groove you used? Fuel use? Temps?

Also, singh's site cites max useful gains at low rpm's, not necessarily top-end.

Although I can see how getting to the top-end faster is way helpful.

What about running a third series with deeper or multiple grooves?

Something's cooking!

[peerless]

Hey guys,

New to the forum, but not new to engines or cars. Built a few and am working on another. I have been following this discussion avidly...well at least the last 2 hours reading and checking links.

I read an old popular science mag, and it had the article on Somander-Singh. I was skepticle but very interested. Tonight I found this link, and what a huge suprise to see so much interest in this subject.

My main interest in this concept is building torque. I certainly don't expect this grooving technique to give me tons more torque, but every little bit helps. I am building a BMW 2.7L, concentrating on torque.

If I could I would like to make some comments and rehash a few old pics, and throw in a couple new ones

First regarding the dyno test's that where done. While it seemed that this "grooving" technique didn't produce any significant results. I did notice a few things. One is the obvious drop in EGT's, This was without a timing or fueling change. That in itself says something. The other peice I noticed that nobody seemed to mention was the "smoothing" effect on the torque curve.

Take a second look:
http://www.revsearch.com/grooves/6200-4000.jpg

The 4000-2000 wide open throttle sweep tests proved to be more interesting. In the best case scenario there was a 6.5 ft. lb. average torque gain in the 2200-3500 RPM band.

Comparing the best before groove 4000-2000 wide open throttle test to the worst after groove test still shows a 2.68 ft. lb. average torque gain in the 2200-3500 RPM band.

Note to the results are the "Worst After Grove" results compared to the "Best Before Groove" results. And it is still gaining torque. So I am curious, what was the "Best" before and "Best" after groove comparisions/results?? Inquiring minds want to know??

Also following 2 pictures say a thousand words concerning complete fuel burn, remember there was no change in fueling or timing!
(See assumptions made by me)
Runs before grooves (reader assumes head was cleaned before dyno test?)
http://www.revsearch.com/grooves/beforegrooves.jpg
Runs after grooves (reader assumes this was after dyno pulls?)
http://www.revsearch.com/grooves/aftergrooves.jpg

Also backed up by this example:
http://members.cox.net/raunch/fabian%20r44.jpg

So it is obvious that the grooving technique is a seeminly positive improvement in combustion effeciency. I think that the power gains come from taking advantage of tuning with this improved volumetric efficiency.

In my opinion I think that another dyno testing session should be held and this time add more fuel and play with the timing, I bet you get some torque gains to talk about. So what ever you do don't let this idea be a fleating passing. I think it holds potential for a lot of enthusiast/racers/DIY's.

Promised some new pics.
Someone earlier mentioned metric mechanic, well here is a pic of there grooving technique, and a aritcle link for further info. They have some dyno proven gains. http://www.metricmechanic.com/pg28.htm


The picture above shown is a BMW 2.5L head and uses a crowned piston. The cylinder head my engine uses is a semi-closed chamber. I unfortunatly dont have a picture of my chamber, but has same valve arrangement and 2mm smaller valve size. Here is a picture of my new 9.5CR pistons, raised the dish to achieve higher CR. Compared to original cast piston:
http://img.photobucket.com/albums/v176/ ... iston3.jpg
http://img.photobucket.com/albums/v176/ ... iston2.jpg

Point being I want to build for torque, and what ever mods I can do safely and effeciently are on my top priority for the new engine. I will find a picture of the combustion chamber so maybe you could give me advice on how I should groove it.

Sorry for the long post

[automotive breath]

...My main interest in this concept is building torque. I certainly don't expect this grooving technique to give me tons more torque, but every little bit helps....

This link describes one of the engines I'm involved with. The post groove results are more pronounced in this case than any other example. Hopefully we will get some 1/4 mile results soon.

http://somender-singh.com/content/view/77/37/



**********************************************************

Another engine I’m involved with will be running in a Super Gas car at the division 4 points meet at NO Problem Raceway next weekend. No before/after results because we changed the entire combination.

[greg_nate]

Hey guys,

New to the forum, but not new to engines or cars. Built a few and am working on another. I have been following this discussion avidly...well at least the last 2 hours reading and checking links.

I read an old popular science mag, and it had the article on Somander-Singh. I was skepticle but very interested. Tonight I found this link, and what a huge suprise to see so much interest in this subject.

My main interest in this concept is building torque. I certainly don't expect this grooving technique to give me tons more torque, but every little bit helps. I am building a BMW 2.7L, concentrating on torque.

If I could I would like to make some comments and rehash a few old pics, and throw in a couple new ones

First regarding the dyno test's that where done. While it seemed that this "grooving" technique didn't produce any significant results. I did notice a few things. One is the obvious drop in EGT's, This was without a timing or fueling change. That in itself says something. The other peice I noticed that nobody seemed to mention was the "smoothing" effect on the torque curve.

Take a second look:
http://www.revsearch.com/grooves/6200-4000.jpg

The 4000-2000 wide open throttle sweep tests proved to be more interesting. In the best case scenario there was a 6.5 ft. lb. average torque gain in the 2200-3500 RPM band.

Comparing the best before groove 4000-2000 wide open throttle test to the worst after groove test still shows a 2.68 ft. lb. average torque gain in the 2200-3500 RPM band.

Note to the results are the "Worst After Grove" results compared to the "Best Before Groove" results. And it is still gaining torque. So I am curious, what was the "Best" before and "Best" after groove comparisions/results?? Inquiring minds want to know??

Also following 2 pictures say a thousand words concerning complete fuel burn, remember there was no change in fueling or timing!
(See assumptions made by me)
Runs before grooves (reader assumes head was cleaned before dyno test?)
http://www.revsearch.com/grooves/beforegrooves.jpg
Runs after grooves (reader assumes this was after dyno pulls?)
http://www.revsearch.com/grooves/aftergrooves.jpg

Also backed up by this example:
http://members.cox.net/raunch/fabian%20r44.jpg

So it is obvious that the grooving technique is a seeminly positive improvement in combustion effeciency. I think that the power gains come from taking advantage of tuning with this improved volumetric efficiency.

In my opinion I think that another dyno testing session should be held and this time add more fuel and play with the timing, I bet you get some torque gains to talk about. So what ever you do don't let this idea be a fleating passing. I think it holds potential for a lot of enthusiast/racers/DIY's.

Promised some new pics.
Someone earlier mentioned metric mechanic, well here is a pic of there grooving technique, and a aritcle link for further info. They have some dyno proven gains. http://www.metricmechanic.com/pg28.htm


The picture above shown is a BMW 2.5L head and uses a crowned piston. The cylinder head my engine uses is a semi-closed chamber. I unfortunatly dont have a picture of my chamber, but has same valve arrangement and 2mm smaller valve size. Here is a picture of my new 9.5CR pistons, raised the dish to achieve higher CR. Compared to original cast piston:
http://img.photobucket.com/albums/v176/ ... iston3.jpg
http://img.photobucket.com/albums/v176/ ... iston2.jpg

Point being I want to build for torque, and what ever mods I can do safely and effeciently are on my top priority for the new engine. I will find a picture of the combustion chamber so maybe you could give me advice on how I should groove it.

Sorry for the long post

I couldn't find any dyno numbers for the Metric Mechanics head modifications.

[putztastics]

Also following 2 pictures say a thousand words concerning complete fuel burn, remember there was no change in fueling or timing!
(See assumptions made by me)
Runs before grooves (reader assumes head was cleaned before dyno test?)
http://www.revsearch.com/grooves/beforegrooves.jpg
Runs after grooves (reader assumes this was after dyno pulls?)
http://www.revsearch.com/grooves/aftergrooves.jpg

Both of those pictures were taken when the heads were off for grooving, before the dyno testing with the grooves. The first one is the untouched chambers right off the dyno. The second picture was after the grooving, not the grooves dyno tests. I did not take heads off the engine after the grooves testing was over.

There was a layer of soot in the chambers, the engine was not shut down under load before the heads were pulled. I think the chambers would have looked different if the engine had been shut off under load. The sooty carbon dust easily wiped off the valves. That soot could have been from the Klotz + 91 fuel.

The engine posted its best ever hp and torque peaks on 100LL during the tests of Klotz HiTRATE + 91, 100LL and VP C-12. It still was within 1-2 chp and ctq of its best pre-groove numbers in the 6200-4000 range.

I did not retest the 4000-2000 range with the three different fuels.

[liquigas]

Baseline shows proof positive benefits. Undisputed. Now make it roar.

[liquigas]

Putzstats, what is the cost of a "best" groove configuration test?

timing, compression, gasses....