Runners
08-31-2017, 09:06 AM
#41
Le Mans Master
Here's an article where they tested a 5.4L 4v Ford engine with variable runner lengths. Again, no other changes were made. Going from 20" runners to 11" runners netted an increase in power of 34hp with no other changes at all.
Wave Action Theory for Tuning of Intake and Exhaust Manifold tells us specifically that wave tuning can help or hurt engine performance, which speaks directly to my point about TPI intakes.
Both of these articles point out something which I had been missing, but which is alluded to by those who discuss larger-bore runners: the rpm (frequency) of the tuning effect varies proportionately to the square root of the area of the runner. That is, the bigger the diameter of the runners, the higher the resonant frequency will be. So to some extent, it is true that large-bore aftermarket TPI intakes will improve the rpm/power ability of the engine. The problem is that intake port of the head is also part of the volume being considered in the Helmholtz equation, and that is a relatively fixed-port. It not only brings down the total area/volume of the intake system, but it also prevents one from going nuts with giant-bore runners because they would have to neck way down at the manifold base to transition into the intake port. So the head design (and ultimately the max valve diameter) really constrains what one can do with the intake runner area. It's by far easier to change the runner length. What Chevy did with the LT engines was effectively to throw all the wave tuning in the trash can in favor of a less restrictive manifold at all rpms.
Wave Action Theory for Tuning of Intake and Exhaust Manifold tells us specifically that wave tuning can help or hurt engine performance, which speaks directly to my point about TPI intakes.
Both of these articles point out something which I had been missing, but which is alluded to by those who discuss larger-bore runners: the rpm (frequency) of the tuning effect varies proportionately to the square root of the area of the runner. That is, the bigger the diameter of the runners, the higher the resonant frequency will be. So to some extent, it is true that large-bore aftermarket TPI intakes will improve the rpm/power ability of the engine. The problem is that intake port of the head is also part of the volume being considered in the Helmholtz equation, and that is a relatively fixed-port. It not only brings down the total area/volume of the intake system, but it also prevents one from going nuts with giant-bore runners because they would have to neck way down at the manifold base to transition into the intake port. So the head design (and ultimately the max valve diameter) really constrains what one can do with the intake runner area. It's by far easier to change the runner length. What Chevy did with the LT engines was effectively to throw all the wave tuning in the trash can in favor of a less restrictive manifold at all rpms.
Last edited by MatthewMiller; 08-31-2017 at 09:41 AM.
08-31-2017, 10:01 AM
#42
Here's an article where they tested a 5.4L 4v Ford engine with variable runner lengths. Again, no other changes were made. Going from 20" runners to 11" runners netted an increase in power of 34hp with no other changes at all.
good
Wave Action Theory for Tuning of Intake and Exhaust Manifoldt tells us specifically that wave tuning can help or hurt engine performance, which speaks directly to my point about TPI intakes.
Both of these articles point out something which I had been missing, but which is alluded to by those who discuss larger-bore runners: the rpm (frequency) of the tuning effect varies proportionately to the square root of the area of the runner. That is, the bigger the diameter of the runners, the higher the resonant frequency will be. So to some extent, it is true that large-bore aftermarket TPI intakes will improve the rpm/power ability of the engine. The problem is that intake port of the head is also part of the volume being considered in the Helmholtz equation, and that is a relatively fixed-port. It not only brings down the total area/volume of the intake system, but it also prevents one from going nuts with giant-bore runners because they would have to neck way down at the manifold base to transition into the intake port. So the head design (and ultimately the max valve diameter) really constrains what one can do with the intake runner area. It's by far easier to change the runner length. What Chevy did with the LT engines was effectively to throw all the wave tuning in the trash can in favor of a less restrictive manifold at all rpms.
good
Wave Action Theory for Tuning of Intake and Exhaust Manifoldt tells us specifically that wave tuning can help or hurt engine performance, which speaks directly to my point about TPI intakes.
Both of these articles point out something which I had been missing, but which is alluded to by those who discuss larger-bore runners: the rpm (frequency) of the tuning effect varies proportionately to the square root of the area of the runner. That is, the bigger the diameter of the runners, the higher the resonant frequency will be. So to some extent, it is true that large-bore aftermarket TPI intakes will improve the rpm/power ability of the engine. The problem is that intake port of the head is also part of the volume being considered in the Helmholtz equation, and that is a relatively fixed-port. It not only brings down the total area/volume of the intake system, but it also prevents one from going nuts with giant-bore runners because they would have to neck way down at the manifold base to transition into the intake port. So the head design (and ultimately the max valve diameter) really constrains what one can do with the intake runner area. It's by far easier to change the runner length. What Chevy did with the LT engines was effectively to throw all the wave tuning in the trash can in favor of a less restrictive manifold at all rpms.
08-31-2017, 01:25 PM
#44
Good point, I thought about mentioning a while back, BUT they learned something and changed the overall design of the runners. They are long and low, also notice what it did to the torque curve of the LS over the l98.
The L98 tpi is bad for performance is multiple ways all being too small to run a cam, heads, or cubes. I think that is what you are missing.
The Larger TPI aftermarket stuff fixed some of the size issues, except the small plenum and the configuration of the long tube runners that the LS solved.
LS kept the torque and grew in revs. The engineers learned.
08-31-2017, 01:27 PM
#45
Keep your thoughts where they are. Done providing mechanical engineering facts and physics to a know it all.
08-31-2017, 01:53 PM
#46
Le Mans Master
Member Since: Oct 2002
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Congratulations Matt, it reads like you have insight on how complicated this pulse wave theory can become or actually is. And it's the whole engine combination that achieves the desired results as you have spoken your self how camshaft profile affects this. And you will find circle track racers spend a great deal of effort to got their exhaust tuned. I have to explain a little how the exhaust effects the power curve so much that many circuit track racers have begun to use unequal length exhaust primary tubes as this spreads the power band rather than have a single large power peak. And they spend plenty of time working the collector length. Don't want to go off-topic here but just trying to make the point how much science we are dealing with here - it's really a big animal and difficult to say what one owner needs w/o a whole lotta information.
But to appreciate the mini ram/LT1 users data those short runner intakes show how much restriction there is in the competing intakes and a broad power curve can desirable. TPI will port their mini ram for even more power as the plenum can be enlarged in areas to help flow. How the air turns inside the plenum is an unseen effect along with smoothing corners rather than sharp corners. I guess I'm suggesting if you can cut and weld the intake accurately there are improvements to be had w/o even changing runner length.
Ok, I've blaborated enough and nearing off topic territory. Hope this can help more than it hurts someone.
But to appreciate the mini ram/LT1 users data those short runner intakes show how much restriction there is in the competing intakes and a broad power curve can desirable. TPI will port their mini ram for even more power as the plenum can be enlarged in areas to help flow. How the air turns inside the plenum is an unseen effect along with smoothing corners rather than sharp corners. I guess I'm suggesting if you can cut and weld the intake accurately there are improvements to be had w/o even changing runner length.
Ok, I've blaborated enough and nearing off topic territory. Hope this can help more than it hurts someone.
08-31-2017, 03:24 PM
#47
Team Owner
Pro Mechanic
What I would really like to see is a controlled test where the same engine gets a really large-bore TPI intake that flows identically to a MR or LT1 intake or whatever short-runner intake you want to choose. Then bolt each one to the engine and dyno them. The differences in power would then be due only to resonance effects in the TPI-style intake. I am not aware of such a test having ever been run, but it would be interesting. On edit: This test could be run on an engine dyno more directly by just using eight straight, vertical intake runner with a common plenum and TB on top (think old-school Hillborn injector manifold without the eight individual throttle blades). You could sub in various lengths of runner tubes easily enough, retaining the same diameter, and run each configuration to see how the lengths change power at various rpm.
08-31-2017, 03:57 PM
#49
Team Owner
Pro Mechanic
Kind of. It SORT of supports Matthew Miller's theory that LTR is workable on a stockish combo; the engine has a mildish cam (for it's size) and it made more HP with long(er) runners. Still, the runners were shorter than TPI runners, and shortening some still increased hp. It would have been nice if they had tested a wider range of runner lengths.
It's data, though.
Matt's posts in this thread are spot on, and that is why we see some modern cars w/variable length intakes; so they can exploit the advantages of of tuning...w/o the disadvantages.
It's data, though.
Matt's posts in this thread are spot on, and that is why we see some modern cars w/variable length intakes; so they can exploit the advantages of of tuning...w/o the disadvantages.
08-31-2017, 05:35 PM
#50
Drifting
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I never compared regular Tpi intake to an LS1 intake.I don't need Your Lessons on how things work.So shut your Pie Hole 856Speed.
Last edited by steven mack; 08-31-2017 at 05:48 PM. Reason: add info
08-31-2017, 06:15 PM
#51
Team Owner
Pro Mechanic
^Yikes!
All "LS" engines (all Gen III, IV and V) use fixed length runner. Pretty sure the Phord does too.
The diff between them and TPI (as it relates to this thread) is that the Gen III^ intake runner lengths are geared to boost tq near the top of the RPM range, rather than in the middle. It is my opinion that they did that to help bolster the top end on a very mild cam.
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The diff between them and TPI (as it relates to this thread) is that the Gen III^ intake runner lengths are geared to boost tq near the top of the RPM range, rather than in the middle. It is my opinion that they did that to help bolster the top end on a very mild cam.
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Last edited by Tom400CFI; 08-31-2017 at 06:40 PM.
08-31-2017, 06:27 PM
#52
Le Mans Master
It's worth noting that the Ford Coyote uses cam phasing to bolster to tune its output for various rpms and loads. I am guessing that this makes a true variable-length intake less important. The variable overlap of the cams would tend to make a single-length intake more appropriate to different rpms and loads. The LS engine makes up for its lack of variable-length intake runners and variable cam phasing with shear cubic inches, while keeping itself compact and light. Like Tom wrote, it would make the best use of intake tuning toward its peak-power rpm.
PS - I do think it would be useful to experiment with the addition of a pie hole on an intake. That might provide the ideal solution to maximizing wave tuning.
PS - I do think it would be useful to experiment with the addition of a pie hole on an intake. That might provide the ideal solution to maximizing wave tuning.
Last edited by MatthewMiller; 08-31-2017 at 06:28 PM.
08-31-2017, 07:29 PM
#55
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St. Jude Donor '05
if one gets an opportunity take a look at a runner off a FAST lsx intake
The shape/taper allow that runner length to do what it does, same with the volume of the heads. Big volume/decent airspeed
The shape/taper allow that runner length to do what it does, same with the volume of the heads. Big volume/decent airspeed
08-31-2017, 07:30 PM
#56
this thread went to sh...by knuckheads.
Last edited by 856SPEED; 08-31-2017 at 07:51 PM.
08-31-2017, 09:09 PM
#58
Team Owner
