Chamber Grooves - what do you guys think?

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Keith Morganstein
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Postby Keith Morganstein » Mon Feb 20, 2006 11:33 pm

putztastics wrote: Accurate BSFC numbers depend on the instantaneous fuel flow matching the exact RPM/HP that fuel flow occurred at. If you think about it they can't possibly match exactly during sweep testing an engine with a carburetor.

This is an interesting thread. I think BSFC is the best indicator of increased efficiency. I appreciate the dyno testing but have a question on the stutska. Aren't you able to hold the program at rpm intervals and measure at stabilized conditions?

My experience is with superflow and I never did like their sweep test for reliable, repeatable BSFC measurement.

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Postby putztastics » Tue Feb 21, 2006 12:54 am

putztastics wrote:I think there would have been more gains in the 2200-3200 rpm range with the grooves if I would have retarded the timing a couple degrees. That tuning change would have been supported by the decrease in the EGTs in that RPM range. The decrease in EGTs in that range could have meant the burn was faster because of the grooves. The problem with that move though is that 2200 RPM is pretty low to pull an engine with a peak tq rpm of 4500. Add to that my hunch the engine didn't want less timing up on top, I think top end power would have dropped with less timing.

I am going nuts, I was looking at the egt drop in the throttle stop tests in the 2200-3200 range. One reason the timing decrease entered my head is that I increased the timing 2 degrees with the Klotz + 91 octane mix when I switch to it from the 100LL I had been using. That is on page one of the octane booster thread.

Bill I don't follow what you are saying in your last line about timing and MBT.

Any BSFC comparisons would have to be done in the exact same weather conditions because BSFC will vary with brake hp, brake horsepower will vary with the weather.

I could have and should have done some steady state tests.

Automotivebreath, put steady state tests on your list for the dyno testing you plan.
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Postby MadBill » Tue Feb 21, 2006 7:59 am

automotive breath wrote:..One thing I would like to test is if the modified engine is more resistant to detonation, any ideas on a good approach?

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.
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Postby F1Fever » Tue Feb 21, 2006 11:12 am

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.
They obviously appear to work, but my question is about the effect of heat transfer into the head on the quench pad and how they would work on a nitrous injected engine...
I was no longer driving the car consciously. I was driving it by a kind of instinct, only I was in a different dimension.
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Postby greg_nate » Tue Feb 21, 2006 2:40 pm

MadBill wrote: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. :notworthy:

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.

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Postby hotrod » Wed Feb 22, 2006 6:37 am

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 ;)

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Postby putztastics » Wed Feb 22, 2006 10:40 am

MadBill wrote: 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.
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MBT

Postby hotrod » Wed Feb 22, 2006 11:22 am

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

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Postby automotive breath » Wed Feb 22, 2006 1:33 pm

putztastics wrote:…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.

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Re: MBT

Postby MadBill » Wed Feb 22, 2006 10:29 pm

hotrod wrote: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.
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Re: MBT

Postby automotive breath » Wed Feb 22, 2006 10:34 pm

MadBill wrote:… 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?

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Postby MadBill » Wed Feb 22, 2006 11:03 pm

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.
Felix, qui potuit rerum cognscere causas.

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Postby liquigas » Thu Feb 23, 2006 4:36 am

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!
-insert pithy comment here-

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Postby peerless » Thu Feb 23, 2006 11:47 pm

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
Image

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 :wink:
Robert
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Postby automotive breath » Fri Feb 24, 2006 1:17 am

peerless wrote:...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/

Image

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

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.

Image


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