Chamber Grooves - what do you guys think?

[automotive breath]

There was a torque gain of about 3% in the 2200-3500 RPM range in the 4000-2000 WOT tests.

Thanks Jessie for your careful planning and enthusiasm. You took the time to give the modification a fare chance in a very professional manner.

[Unkl Ian]

Did the BSFC change ?

[putztastics]

Of course the BSFC was slightly better in the 4000-2000 WOT test - that would correspond with the power gain in the 2200-3000 range.

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 because the fuel flow to a carb will always lag behind the fuel being flowed through the carb boosters when the engine RPM or load is changing. I think the only way to get accurate BSFC numbers is with steady state testing, or by measuring actual carb booster fuel flow, or by running fuel injection where there is no fuel bowls and floats involved. It is not a fuel flow meter problem, I have a $2500 EG&G fuel flow meter on my dyno. It is a fuel flow metering lag problem caused by where the fuel flow is being measured. As you would know the fuel flow to the carb will lag behind the fuel being flowed in carb boosters because the floats do not react instantly to changes in booster fuel flow. This will skewer sweep test BSFC numbers. I have a hunch most dyno operators don't think about this too much. Here is something to try at your next dyno session with a carbed engine; have the dyno operator do both an upsweep and down sweep and see if the BSFC numbers are the same. I think you will find they won't be, and the faster the sweep rate the bigger the difference will be. Not only are the BSFC numbers off during sweep testing, the dyno's A/F ratio will not be correct either because of this fuel flow lag problem with carbs. The A/F ratio will be different between upsweeps and downsweeps and again the faster the sweep rate the bigger the difference will be. This is the reason I spent $800 getting set up with a LM-1 O2 based A/F meter for accurate A/F ratio readings.

BSFC numbers will change with the weather as they are based on the brake hp not the corrected horsepower.

In retrospect I should have done some steady state tests, especially in the 2200-3500 rpm range where the grooves showed a power gain. That might be something for the next dyno test session- do some steady state or RPM hold tests to get the most accurate BSFC readings possible.

[Nwguy]

Have you, or will you be posting the results?? Thanks for all the hard work, and sharing of information. Now we will all start to test different depths and lengths of grooves, and local tracks will outlaw grooved combustion chambers. LOL

[putztastics]

I'm going to talk to automotivebreath before posting detailed results.

Unkl Ian, did I answer your question?

[putztastics]

Grooves Testing Results

What you see is how a putz from North Dakota (where's that?) tests grooves.

Please note there was no followup testing like timing or jetting changes with the grooves. The testing attempts to show the difference the grooves alone made.

Testing like this can raise more questions than it answers.

It can drive you, (well, me anyway) nuts, (which might explain a few things, I know.)

Thanks.

[Fatman]

Putz:
I would have liked too see the motor tuned to suit the grooved heads. i think that would have been a more suitable comparison.
A well tuned standard headed motor against a well tuned groove headed motor.
thanks for sharing the results.

[Unkl Ian]

Yes,thanks.

Unkl Ian, did I answer your question?

Like you said, testing raises more questions.

Thanks for your efforts on this.

[putztastics]

Putz:
I would have liked too see the motor tuned to suit the grooved heads. i think that would have been a more suitable comparison.
A well tuned standard headed motor against a well tuned groove headed motor.
thanks for sharing the results.

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.

There was a difference in the A/F ratio before and after grooving, it got leaner. But lean is mean, so would one really wanted to richen it up? What would have that done to the top end?

These are the thoughts that drive men nuts.

Even when the testing is over it's not over.

I will be doing some fuel testing on that engine, the Klotz HiTRATE mix, 100LL and VP C-12. I will see how the 100LL before grooves tests match up with the 100LL after grooves tests.

I expect C-12 to be the best.

We don't have a great selection of race fuel available here.

[MadBill]

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.

[automotive breath]

..... 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....
… So would one really wanted to richen it up? ...

I to believe it will respond to less timing and more fuel. It would be great if you could prove this while it’s still on the dyno.

I should get my assembly back from balancing this week. My combination is a bit different, results should be interesting. I’m going with more compression and camshaft. I think my topline heads have a different valve angle and larger squish to bore ratio compared to the Dodge heads.

To add a different twist I decided to tune the engine ungrooved in my 68 Camaro at the drag strip first. When I’m convinced the performance is documented I will pull it, dyno test, groove and test again. And of course back to the track post groove. Then we can compare dyno results and ¼ mile performance.

….. Even backing off a few degrees for the 'before', which advance should increase power with the grooves if the theory is correct…

This makes sense; I may give it a try.

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

[Keith Morganstein]

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.

[putztastics]

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.

[MadBill]

..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.

[F1Fever]

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...