The Myth: Resonance Tuning vs. BackPressure
Registered User
Joined: Feb 2004
Posts: 291
From: Abbeville , LA
"The Scientific Design of Intake and Exhaust Systems"
by Phillip H Smith
is a very good recommendation
Mr. Smith did pioneering work Morrison pressure indicator
check out that section in his book also
more than 15 years ago i 1st purchased his book, its been a great referrence to this day
all his data/results are rock solid
i've spent last 15 years dyno testing engines with SuperFlow
SF-901 doing thousands of exhaust tests and just about close to 90.0 % PerCent follow what Dr. Phillip H Smith's predictions would indicate
i've watched Racers com to my dyno and try the Paint/Burn/Cut method to determine where collector length should be ...
Paint/Burn/Cut Method= you Paint a line along length of collector and make a dyno test..wherever the paint stops burning you cut it off, and according to that Myth , thats the perfect length
the only problem is , its not the perfect length , and by LUCK will this method only work !!
if you would again paint another mark along length of collector and make another dyno test...you would find out that the burn mark has now shifted in new location
if you continually repeat this cycle, you will have no more collector left , along with LESS TORQUE . you will be fooled by this method
in fact in all my testing , this method is very much worse than a 50/50 coin toss in accuracy ...it appears to be only 1 out 10 times by chance it happens to work
if you use and develope equations from Mr Smith's book, you will be 70 to 90 % percent correct
by Phillip H Smith
is a very good recommendation
Mr. Smith did pioneering work Morrison pressure indicator
check out that section in his book also
more than 15 years ago i 1st purchased his book, its been a great referrence to this day
all his data/results are rock solid
i've spent last 15 years dyno testing engines with SuperFlow
SF-901 doing thousands of exhaust tests and just about close to 90.0 % PerCent follow what Dr. Phillip H Smith's predictions would indicate
i've watched Racers com to my dyno and try the Paint/Burn/Cut method to determine where collector length should be ...
Paint/Burn/Cut Method= you Paint a line along length of collector and make a dyno test..wherever the paint stops burning you cut it off, and according to that Myth , thats the perfect length
the only problem is , its not the perfect length , and by LUCK will this method only work !!
if you would again paint another mark along length of collector and make another dyno test...you would find out that the burn mark has now shifted in new location
if you continually repeat this cycle, you will have no more collector left , along with LESS TORQUE . you will be fooled by this method
in fact in all my testing , this method is very much worse than a 50/50 coin toss in accuracy ...it appears to be only 1 out 10 times by chance it happens to work
if you use and develope equations from Mr Smith's book, you will be 70 to 90 % percent correct
Registered User
Joined: Oct 2002
Posts: 2,931
From: Upstate NY
Originally posted by MaxRaceSoftware
i've spent last 15 years dyno testing engines with SuperFlow
SF-901 doing thousands of exhaust tests and just about close to 90.0 % PerCent follow what Dr. Phillip H Smith's predictions would indicate
i've watched Racers com to my dyno and try the Paint/Burn/Cut method to determine where collector length should be ...
in fact in all my testing , this method is very much worse than a 50/50 coin toss in accuracy ...it appears to be only 1 out 10 times by chance it happens to work
if you use and develope equations from Mr Smith's book, you will be 70 to 90 % percent correct
i've spent last 15 years dyno testing engines with SuperFlow
SF-901 doing thousands of exhaust tests and just about close to 90.0 % PerCent follow what Dr. Phillip H Smith's predictions would indicate
i've watched Racers com to my dyno and try the Paint/Burn/Cut method to determine where collector length should be ...
in fact in all my testing , this method is very much worse than a 50/50 coin toss in accuracy ...it appears to be only 1 out 10 times by chance it happens to work
if you use and develope equations from Mr Smith's book, you will be 70 to 90 % percent correct
Good info, MaxRace. I forgot about the P/B/C method. Watch out or you may start a new trend here!
Welcome aboard.
Ever watch Victory By Design on SPEED TV? It's interesting to study the exhaust systems on some of the oldest cars they drive. I especially like the Brooklands "Silencer". It's like the terminator box that can be used to tune the collector in a system that continues past optimum collector length.
Registered User
Joined: Feb 2004
Posts: 291
From: Abbeville , LA
Alexandria , LA ? straight north of me
"The Scientific Design of Intake and Exhaust Systems"
by Phillip H Smith
one of the only things in his book that i found to be incorrect was
the very last couple of paragraphs in one of the last Chapters right before he goes to Emissions
Mr. Smith talking about being puzzled over a Paper a colleague
published in it stating => as Compression Ratio is increased...
Volumetric Efficiency decreases
Smith doesn't actually state he agrees with theory, but doesn't say anything to deny it
in all my dyno testing,....everytime Compression Ratio is increased..then Volumetric Efficiency is also likewise increased !
As CR increases ...peak torque RPM point seems to relatively stay at same RPM point as before, but the RPM point of Peak Horsepower seems to shift upwards slightly higher, sometimes as much as 200 RPMs higher than before CR increase
and Ve % also increases over a wide RPM range more than before with lower CR
"The Scientific Design of Intake and Exhaust Systems"
by Phillip H Smith
one of the only things in his book that i found to be incorrect was
the very last couple of paragraphs in one of the last Chapters right before he goes to Emissions
Mr. Smith talking about being puzzled over a Paper a colleague
published in it stating => as Compression Ratio is increased...
Volumetric Efficiency decreases
Smith doesn't actually state he agrees with theory, but doesn't say anything to deny it
in all my dyno testing,....everytime Compression Ratio is increased..then Volumetric Efficiency is also likewise increased !
As CR increases ...peak torque RPM point seems to relatively stay at same RPM point as before, but the RPM point of Peak Horsepower seems to shift upwards slightly higher, sometimes as much as 200 RPMs higher than before CR increase
and Ve % also increases over a wide RPM range more than before with lower CR
Thread Starter
Registered User
Joined: Sep 2002
Posts: 655
RE: CR increase vs. VE% Increase
Is that because the volume above the piston at TDC is less,
allowing for better "suction" or draw of the intake runner?
Similar idea to: too large of an exhaust primary will shift the
power up the RPM band when the motor can create enough
exhaust gas volume to make use of the large primary.
In other words, if there was 100 cc of volume above the piston at TDC (as opposed to 80 cc ) , the VE % would decrease because
the movement of the piston at the intake valve (low pressure)would not be felt "instantly"?
Is that because the volume above the piston at TDC is less,
allowing for better "suction" or draw of the intake runner?
Similar idea to: too large of an exhaust primary will shift the
power up the RPM band when the motor can create enough
exhaust gas volume to make use of the large primary.
In other words, if there was 100 cc of volume above the piston at TDC (as opposed to 80 cc ) , the VE % would decrease because
the movement of the piston at the intake valve (low pressure)would not be felt "instantly"?
Registered User
Joined: Oct 2002
Posts: 2,931
From: Upstate NY
Originally posted by MaxRaceSoftware
Alexandria , LA ? straight north of me
That was in 1971!
"The Scientific Design of Intake and Exhaust Systems"
by Phillip H Smith
one of the only things in his book that i found to be incorrect was
the very last couple of paragraphs in one of the last Chapters right before he goes to Emissions
Mr. Smith talking about being puzzled over a Paper a colleague
published in it stating => as Compression Ratio is increased...
Volumetric Efficiency decreases
Smith doesn't actually state he agrees with theory, but doesn't say anything to deny it
in all my dyno testing,....everytime Compression Ratio is increased..then Volumetric Efficiency is also likewise increased !
I just ran a few CR sims on EA Pro for a 500+ hp 383. 2 points of compression was worth about 5% torque and 6.7 % hp, but the calculated VE DECREASED about 1% around torque peak when the CR was raised! I've never tried that before on a simulator. Curious.
Oh, the calculated VEs at power peak were closer (within .2%). Intake tuning pressures had been opitimized with cam & exhaust selection, and peak intake tuning pressure was the same at VE peak, but slightly HIGHER for the 9.1 CR than the 11.1 below VE peak (5000). Curiouser...
I'm going to look into this some more. Thanks for bringing this up.
As CR increases ...peak torque RPM point seems to relatively stay at same RPM point as before, but the RPM point of Peak Horsepower seems to shift upwards slightly higher, sometimes as much as 200 RPMs higher than before CR increase and Ve % also increases over a wide RPM range more than before with lower CR
I'm not seeing this on the simulation. I'm going to "unoptimize" the tuning and see what happens.
This is fun.
Jon
Alexandria , LA ? straight north of me
That was in 1971!
"The Scientific Design of Intake and Exhaust Systems"
by Phillip H Smith
one of the only things in his book that i found to be incorrect was
the very last couple of paragraphs in one of the last Chapters right before he goes to Emissions
Mr. Smith talking about being puzzled over a Paper a colleague
published in it stating => as Compression Ratio is increased...
Volumetric Efficiency decreases
Smith doesn't actually state he agrees with theory, but doesn't say anything to deny it
in all my dyno testing,....everytime Compression Ratio is increased..then Volumetric Efficiency is also likewise increased !
I just ran a few CR sims on EA Pro for a 500+ hp 383. 2 points of compression was worth about 5% torque and 6.7 % hp, but the calculated VE DECREASED about 1% around torque peak when the CR was raised! I've never tried that before on a simulator. Curious.
Oh, the calculated VEs at power peak were closer (within .2%). Intake tuning pressures had been opitimized with cam & exhaust selection, and peak intake tuning pressure was the same at VE peak, but slightly HIGHER for the 9.1 CR than the 11.1 below VE peak (5000). Curiouser...
I'm going to look into this some more. Thanks for bringing this up.
As CR increases ...peak torque RPM point seems to relatively stay at same RPM point as before, but the RPM point of Peak Horsepower seems to shift upwards slightly higher, sometimes as much as 200 RPMs higher than before CR increase and Ve % also increases over a wide RPM range more than before with lower CR
I'm not seeing this on the simulation. I'm going to "unoptimize" the tuning and see what happens.
This is fun.
Jon
Registered User
Joined: Feb 2004
Posts: 291
From: Abbeville , LA
Todd Wasson 's Straight Line Simulator has a
"Filling and emptying" Model , combined with intake gas momentum model ...in his 1/4 mile simulation program
if you "Increase Compression Ratio" in Mr. Wasson's computer model ..it predicts that Volumetric Efficiency "Increases" ....
and to my surprise...Ve % and RPM point of Peak HP occurrence "ALSO moves upward" in RPM point
his model verifies my actual dyno test data in those respects !
http://performancesimulations.com/
-----------------------------------------------------------------------------
http://www.proracingsim.com/
ProSim is also known as DeskTop Dyno , which is simpler version of original "Dynomation" computer model
both DeskTopDyno and Dynomation again calculate that when Compression Ratio is increased .... Volumetric Efficiency is also Increased !
again verifing my dyno data .
However, both DeskTop Dyno and Dynomation do not reveal or show a slight upward shift in the Peak HP RPM point like my actual dyno data or like Todd Wasson's simulator.
but only a 1/3 or so in my data did the Peak HP RPM point actually move upwards , the rest of the time, that point remained where it was originally .
Also, 100.0 % PerCent of time in all my tests, Ve % did always increase with increases in Compression Ratio, no matter what name brand or size engine i was dyno testing at the time .
"Filling and emptying" Model , combined with intake gas momentum model ...in his 1/4 mile simulation program
if you "Increase Compression Ratio" in Mr. Wasson's computer model ..it predicts that Volumetric Efficiency "Increases" ....
and to my surprise...Ve % and RPM point of Peak HP occurrence "ALSO moves upward" in RPM point
his model verifies my actual dyno test data in those respects !
http://performancesimulations.com/
-----------------------------------------------------------------------------
http://www.proracingsim.com/
ProSim is also known as DeskTop Dyno , which is simpler version of original "Dynomation" computer model
both DeskTopDyno and Dynomation again calculate that when Compression Ratio is increased .... Volumetric Efficiency is also Increased !
again verifing my dyno data .
However, both DeskTop Dyno and Dynomation do not reveal or show a slight upward shift in the Peak HP RPM point like my actual dyno data or like Todd Wasson's simulator.
but only a 1/3 or so in my data did the Peak HP RPM point actually move upwards , the rest of the time, that point remained where it was originally .
Also, 100.0 % PerCent of time in all my tests, Ve % did always increase with increases in Compression Ratio, no matter what name brand or size engine i was dyno testing at the time .
Last edited by MaxRaceSoftware; Feb 10, 2004 at 03:14 PM.
Thread Starter
Registered User
Joined: Sep 2002
Posts: 655
I'm not disagreeing with any of the posts, but I have something to
say about Desktop Dyno:
I have the latest version, which includes flow files for cylinder heads and
camshaft profiling.
Even when matching up my compression ratio, using the Sportsman II
flow files and @ 0.050" specs for my camshaft, the power curves
were totally off.
I don't know where I went wrong, but knowing my mechanical compression ratio down to within 0.5 pts., where else could the difference be?
When compared to my chassis dyno graph (Dynojet), the TQ and HP
peaks were both off (by several 100 RPM), the shape of the curves
were nothing alike...and of course, Desktop Dyno seemed to think
I would make 421 HP @ 6500 RPM, whereas the dyno shows
270 HP at 5800 RPM.
That's quite a loss through the drivetrain (assuming DD is crank power)!
say about Desktop Dyno:
I have the latest version, which includes flow files for cylinder heads and
camshaft profiling.
Even when matching up my compression ratio, using the Sportsman II
flow files and @ 0.050" specs for my camshaft, the power curves
were totally off.
I don't know where I went wrong, but knowing my mechanical compression ratio down to within 0.5 pts., where else could the difference be?
When compared to my chassis dyno graph (Dynojet), the TQ and HP
peaks were both off (by several 100 RPM), the shape of the curves
were nothing alike...and of course, Desktop Dyno seemed to think
I would make 421 HP @ 6500 RPM, whereas the dyno shows
270 HP at 5800 RPM.
That's quite a loss through the drivetrain (assuming DD is crank power)!
Registered User
Joined: Feb 2004
Posts: 291
From: Abbeville , LA
Desktop Dyno seemed to think
I would make 421 HP @ 6500 RPM, whereas the dyno shows
270 HP at 5800 RPM.
----------------------------------------------------
DeskTop Dyno and Dynomation both calculate "higher" than reality Horsepower and Torque amounts.
especially the Peak Torque amounts !! are pretty far off from reality .
but, DD does have value and is a useful tool in showing you "relationships/interactions" in engine operation.
you should probably only seen no more than a .76 percent loss from chassis dyno (single-roller) to engine dyno (steady-state)
that would be about 355.3 HP on engine dyno..instead of 421
Automatic/Converter = .76 to .85 percent efficiency
Standard/Clutch= .85 to .90 percent efficiency
depending on acceleration test rate and if chassis dyno software accounts for rotational inertia
if all rotational inertia components are being accounted for
then
Automatic/Converter = .89 to .92 percent total drivetrain efficiency
Standard trans/clutch= .95 to .99 percent total drivetrain efficiency
usually in text books , Automatics=.85 Standards= .90 % as ballpark
i have Engine Analyzer Pro, DeskTop Dyno, Dynomation, Engine Expert, etc and other programs..they all show you useful relationships/interactions in engine operation, but you can't use them to get an exact real HP / TQ numbers
they are good at showing you trends only
use a real honest, correctly calibrated chassis or engine dyno instead .
I would make 421 HP @ 6500 RPM, whereas the dyno shows
270 HP at 5800 RPM.
----------------------------------------------------
DeskTop Dyno and Dynomation both calculate "higher" than reality Horsepower and Torque amounts.
especially the Peak Torque amounts !! are pretty far off from reality .
but, DD does have value and is a useful tool in showing you "relationships/interactions" in engine operation.
you should probably only seen no more than a .76 percent loss from chassis dyno (single-roller) to engine dyno (steady-state)
that would be about 355.3 HP on engine dyno..instead of 421
Automatic/Converter = .76 to .85 percent efficiency
Standard/Clutch= .85 to .90 percent efficiency
depending on acceleration test rate and if chassis dyno software accounts for rotational inertia
if all rotational inertia components are being accounted for
then
Automatic/Converter = .89 to .92 percent total drivetrain efficiency
Standard trans/clutch= .95 to .99 percent total drivetrain efficiency
usually in text books , Automatics=.85 Standards= .90 % as ballpark
i have Engine Analyzer Pro, DeskTop Dyno, Dynomation, Engine Expert, etc and other programs..they all show you useful relationships/interactions in engine operation, but you can't use them to get an exact real HP / TQ numbers
they are good at showing you trends only
use a real honest, correctly calibrated chassis or engine dyno instead .
Registered User
Joined: Jun 2002
Posts: 243
From: TN
Originally posted by Zero_to_69
Even when matching up my compression ratio, using the Sportsman II
flow files and @ 0.050" specs for my camshaft, the power curves
were totally off.
Even when matching up my compression ratio, using the Sportsman II
flow files and @ 0.050" specs for my camshaft, the power curves
were totally off.
Thread Starter
Registered User
Joined: Sep 2002
Posts: 655
I've tried both methods of cam specifications. DD still likes to embellish.
FWIW, I can learn what certain mods do with respect to power band
shifting, torque production, and play with cam/valve timing as a
"relative" measurement (as mentioned above).
FWIW, I can learn what certain mods do with respect to power band
shifting, torque production, and play with cam/valve timing as a
"relative" measurement (as mentioned above).
Thread Starter
Registered User
Joined: Sep 2002
Posts: 655
Mailman came today with a nice present!!!
I'm the proud owener of "Scientific Design of Exhaust and Intake
Systems".
I dont' know why I'm so happy about this...maybe because I feel
100 times smarter just being able to hold it!
Get ready for the questions in the near future boys and girls.
I'm the proud owener of "Scientific Design of Exhaust and Intake
Systems".
I dont' know why I'm so happy about this...maybe because I feel
100 times smarter just being able to hold it!
Get ready for the questions in the near future boys and girls.
Registered User
Joined: Oct 2002
Posts: 2,931
From: Upstate NY
Originally posted by Zero_to_69
Mailman came today with a nice present!!!
I'm the proud owener of "Scientific Design of Exhaust and Intake
Systems".
I dont' know why I'm so happy about this...maybe because I feel
100 times smarter just being able to hold it!
Get ready for the questions in the near future boys and girls.
Mailman came today with a nice present!!!
I'm the proud owener of "Scientific Design of Exhaust and Intake
Systems".
I dont' know why I'm so happy about this...maybe because I feel
100 times smarter just being able to hold it!
Get ready for the questions in the near future boys and girls.
Nope, I've never found the Cliff Notes for it.
Thread Starter
Registered User
Joined: Sep 2002
Posts: 655
OK, here come the questions! I', not quite finished the first chapter
yet, but I want to make sure I'm grasping the terms before moving
on too far.
1. "Gasification" means to change the fuel from its liquid state to
a gas state, correct? All I'm thinking is atomization at this point.
Is there more to this such as "conditioning" the intake charge?
2. Risidual exhaust gas in the chamber after the exhaust stroke
is completed, heats up the intake charge and displaces volume
for the intake charge. This is more apparent at low RPM because
exhuast gas velocity is not high enough to scavenge the cylinder
as the exhaust manifold dimensions are also not tuned for this
range. This residual effect acts very similar to an EGR circuit.
The question is about Thermal Efficiency. Is this referring to optimal
chamber temperatures for combustion, or quality of the intake
charge?
3. Blowdown when using a supercharger: This causes fresh intake
charge to over-shoot the chamber and enter the exhaust manifold.
The higher inlet pressure allows for total scavenge of the combustion
chamber which is beneficial for the power stroke torque production.
My question is...will the charge 'over-shooting' the chamber reduce
volumetric efficiency, or is there enough charge coming in that
a sufficient amount will be trapped?
I think I just answered my own question...but he talks as if it's a
good thing that fresh charge is wasted. I guess it's a "Give and
Take" trade off (VE% vs. full scavenge)?
yet, but I want to make sure I'm grasping the terms before moving
on too far.
1. "Gasification" means to change the fuel from its liquid state to
a gas state, correct? All I'm thinking is atomization at this point.
Is there more to this such as "conditioning" the intake charge?
2. Risidual exhaust gas in the chamber after the exhaust stroke
is completed, heats up the intake charge and displaces volume
for the intake charge. This is more apparent at low RPM because
exhuast gas velocity is not high enough to scavenge the cylinder
as the exhaust manifold dimensions are also not tuned for this
range. This residual effect acts very similar to an EGR circuit.
The question is about Thermal Efficiency. Is this referring to optimal
chamber temperatures for combustion, or quality of the intake
charge?
3. Blowdown when using a supercharger: This causes fresh intake
charge to over-shoot the chamber and enter the exhaust manifold.
The higher inlet pressure allows for total scavenge of the combustion
chamber which is beneficial for the power stroke torque production.
My question is...will the charge 'over-shooting' the chamber reduce
volumetric efficiency, or is there enough charge coming in that
a sufficient amount will be trapped?
I think I just answered my own question...but he talks as if it's a
good thing that fresh charge is wasted. I guess it's a "Give and
Take" trade off (VE% vs. full scavenge)?
Last edited by Zero_to_69; Feb 16, 2004 at 10:39 AM.