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.

 

Good information there!

 

GM actually Tested what the best runner length would be for their Ls series motor. .They came up with 12"s And That's what they have on their LS series motors.

 

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.

 

You forgot to mention or have no knowledge about those composite intakes. They are variable length. Air flow is redirected to a shorter path depending on engine vacuum and other matters. They are LIGHT YEARS AHEAD of your TPI intake. Same way with the Coyote series Ford Engines. They don't run on 12 inch intake runners full time.

Keep your thoughts where they are. Done providing mechanical engineering facts and physics to a know it all.

 

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.

 

HERE YOU GO...

 

Thanks, is a good read!

 

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.

 

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.

 

^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.


.

 

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.

 

I believe they already did that It was called the Edlebrock Big Mouth intake.

 

shut your pie hole little boy...you bother me.

 

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

 

sure you did...You indicate GM preferred a long runner length on the ls motors.

this thread went to sh...by knuckheads.

 

No it went off base By PIE HOLES like you .In England they would tell you to SHUT YOUR CAKE HOLE.

 

What kind of cake or pie are we talking about before I decided to do it the US way or England way?

 

Well in the U.S. they call it eating humble pie.