Obviously in any test, you could see some other aspect of the engine as a limiting factor. In those cases it may have been the camshaft, cylinder heads, other.

If none of the intakes are exceeding a certain power level or rpm....then it's safe to say some of those intakes are not the limiting factor.


As said, we'd all love to see these tests in a huge range of engines....not so easy to find someone to foot the bill for doing so

 

Normally I would agree, and you still may be right, but I think maybe there's more going on.

The part that sticks out to me is not just how consistent the cathedral manifolds peaked, but how high they peaked compared to the rectangle port manifolds. On one hand, you have the OEM LS3 peak at 6500 RPM, which seems pretty typical, but on the other, you have the OEM LS1 manifold that made peak power at 6900 RPM and the OEM LS6 that made peak power at 7000 RPM. That seems unusually high to me. I would think if the cathedral port tests were limited, they would not peak so high. If the rectangle port tests were limited, you would not see such variation.

 

I do find it strange they do peak so high.

I've had a variety of intakes, heads and cams on my cathedral over the years ( all with boost ), and pretty much none have ever been happy over 7k.
Yes I could hang on and ring the life out of it, but beyond 6700rpm or so you just knew it didnt want to be there. Only time I'd hang on much longer would be through the traps in either 4th or 5th depending whether 1/4 or longer distance event ( 5th would see 200mph around 6700rpm )
Even logging accel-g it's quite apparent where in the rpm range it slows down...and every time on mine it is before 7000rpm

I know if I could find a combo where it would make real strong power to 7-7300rpm it would help me a lot, even more so as I've changed to a Magnum and 5th is now shorter which will mean 200mph will require more rpms. I've bought one of the cheap crap Sniper intakes now to see if that might help me as mid range losses are of little concern and might actually be a benefit in terms of traction.

Interesting to note both the cathedral test and LS3 test use a camshaft with the same timings/lift. Although other dyno videos recently have proven all this square port/cathedral port camshaft is largely nonsense as there is negligible difference if you test them

LS3 " as many of these intakes were not designed for our mild cam-only LS3 crate motor (specs on our COMP 54-496-11 hydraulic roller measure 231/247 degrees at .050 and .617/.624-inch lift with a 113 LSA)"

Cathedral " The Comp 469 cam offered a 0.617/0.624-inch lift split, a 231/247-degree duration split and 113-degree LSA. Topping the 6.0L was a set of AFR LSX 230 V2 heads"

So clearly the cylinder heads could be the big factor here with the LS3 listed as just a crate motor...so presume stock heads ? Springs, rockers ?

 

Stock ls3 intake limits those heads pretty bad

 

I have had the same experience with them; not once have I ever seen an LS1/6 manifold peak so high. When Holdener posted it on FB, he said that the increased exhaust duration of the 231/247 cam was responsible. It doesn't seem to have the same effect on the LS3 as you said, as it peaked at 6500 RPM. It wasn't replicated in the cam test either though, where the cathedral headed combo only peaked at 6400 RPM with the same cam. It had a Dorman intake, which is equal to the TBSS manifold per Holdener, but the TBSS manifold peaked at 7000 RPM in the manifold test with the same 231/247 cam.

I'm critical of that cam test too. I think there was a flawed premise that the exhaust duration was the factor in a rectangle port camshaft. I believe the intake duration is the more influential factor. Since the big intake valve offers much more curtain area at each respective lift point, you can reduce overlap and the IVC point to make about the same power, but with considerable increases in low end power and driveability. Instead of going from a 239 to 247 exhaust duration, they should have gone down from a 231 intake duration to a 22x duration.

Or maybe Diet Coke is right. Maybe someone is pushing that 231/247 cam.

 

I would think it would be easy to rev cathedrals over 7k these days with the addition of the msd intake and the right cam. Or even shortening your own set of fast runners. My ls6 doesn't peak till 6400. It seems happy all the way to 7k

What did you use to log acceleration g's? I've been thinking of trying that

 

I can log on the VBox as a standalone but I also log on my ecu ( Syvecs ) which receives GPS/Accelerometer data from my Plex SDM-500 dash unit.

As said, I can easily rev to beyond 7000rpm...but you just know it isnt happy up there. Highest I've seen was just shy of 7500rpm but that was just last year as I'd broken 5th gear and getting highest trap for 1/2m even for a rwd car would have been easy just by hanging on in 4th.
Except I didnt want to hold 4th for the entire duration so was just trying to judge how long to hold in 4th but still win.....not easy to judge at all ! Ended up missing it by 1-2mph as I left it a little too late before going full throttle in 4th. But at the same time, didnt want to risk taking it on to 8k although it probably would have been fine.

Hopefully in a few weeks I can report on how the Holley Sniper changes anything up top.

 

Damned if you do and damned if you don't.

If they optimize the cam and tune for each manifold, people scream that the results are invalid because too many variables were changed.

If they keep everything the same and only change the manifold, people scream that the results are invalid because the setup wasn't optimized for the manifold design.

 

None of these manifolds are a one size fits all. The test does kinda tell you the operating range of these intakes but we would know more if they rung em out to 7500.

 

big hammer, I think you need to add E3 spark plugs to your mod list

 

That mf'r side gaps his ****

 

ITB's are too small, they are smaller than the inlet valve...

 

So THAT's the reason they underachieved?

 

They just needed bigggerer ones.

 

 

seems to me that for a LS3 headed engine that will spend most of its time under 6500 the crossram is the better choice - ie recovery rpm after shifts staying at 6k or more.

but the real king wasn't tested - the CID

 

I have 8x 55mm chokes, they are a hair bigger than the valves in my new AFR245's.

 

 

Which of these intakes(that fits under stockish hoods) would be best for suited for boost? 416 F1C procharger with trickflow 255 heads?

 

Now all you have to do is get FAST-like power out of it....