Ok, I don't have any facts here, but let me say my Seat of the Pants meter is up there with the best.


I had run a wide open plate for years, and I just put in one of the middle plates (it was about 3/4 full or so), and I gotta say instantly I can notice an increase in low-end torque, and with the 3/4 plate it is still very loud. Also, I didn't seem to lose any top-end whatsoever when I revved it up to 5.8-6k.


I have a 98 T/A M6 4.10 , Lid, homemade ram air, under drive pulleys, full exhaust w/ mid headers.


I mean no doubt the car drives better. I had left it off for years b/c of the 4.10s. I figured I had 4.10s so my low-end torque was fine, but you know how it is, the adrenaline addiction, you always want more power once you start driving it, so I made the change.

I may try out the 1/2 plate but I don't want it too quiet. Anyway, I just figured I would let everyone know who was interested that there is indeed a difference in throttle response and perhaps benefits to running smaller plates.

That is of course, if you have a motor with mods similar to mine.


Have fun out there, I gotta say I have been having a blast driving mine. LS1 (and LT1) F-bodies are just great cars.

 

since my LTs install......i cant use no plate option......tooooo much rasp

 

I swap mine out about every three weeks from full closed to the middle sized hole plate. Only difference for me is sound volume lol. I have a 232/238 cam, LT's, and no cats. Also running Richmond 4.10's so the gear whine isn't as noticeable with the open plate in. Sometime down the road I'd like to install an electric cutout.

 

I think the torque may not be higher, but there certainly is a throttle response increase with the lower plate. I think it helps at super low-rpm, like below idle-2000. Even RPMs you never drive at come into play when you take off the line. As you slip your clutch or your converter slips the engine has to move through that low-rpm area. When you are moving 1 mph, even if you are slipping the clutch your torque at that moment is still partially based on what RPM you would be driving at if the gear is fully engaged. That's why the converters/clutchs slip to give that weak RPM area more power. I find that with the better throttle response, my car seems to be more responsive as I move through that area.

Of course it could be all in my head too. Either way, I dont think the sound is that much different with the 3/4 plate than Wide open.

 

I would venture to say its all in your head. Anyone who tells you backpressure is good is full of crap or trying to sell you a shitty muffler. The rasp isnt coming from the borla itsself its coming from a poorly made y-pipe most likely. I had long tubes and wide open borla many years ago and it sounded great IMO

 

Plate vs Non-Plate is their a horsepower gain ?

 

No, I like the rasp, I put the plate in purely for low-end throttle response.


Backpressure may not be the correct term, apparently preserving exhaust flow contributes to torque and response. contribution to low-end torque/throttle response is NOT a marketing ploy sold by muffler companies, it is true.



Catalytic converters shift the power band down, why? Restriction and backpressure. It is a known fact cats cause a car to have a bit more low-end.


This is not in my head, I drove the car everyday for a month and I switched it out and I immediately can tell the difference.

Like I said, my seat of the pants meter is very good, I can't feel a 5-10 ft-lb difference under WOT, but I can detect THROTTLE RESPONSE. No Doubt, Throttle Response is Better Down Low With Smaller Plates, I am not the first person to notice this.


It has been dynoed and the middle size borla plate makes a small bit more HP.

The real issue I am talking about is not peak torque, but low-end torque and throttle response.



I kind of look at it like the thumb at the end of the hose. If you put your finger on it too much you restrict the flow but the water comes out fast.


If you leave it wide open, yes the max amount of water is coming out, but at any given time the pressure of the water is lower.

The perfect amount to put your thumb over the hose is that which increases the pressure of the water without slowing the flow of it down.


In this analogy that means that completely closing the plate will likely hurt performance a bit, so what we want to find is the happy middle ground.

Leaving a huge 3 inch pipe out the right side of the exhaust wide open is not conducive to ideal throttle response, this isn't an illusion, it is real.

 

The borla muffler is a straight through, perforated pipe though, so leaving the cutout closed would just add two more turns in the 3" system, no added restriction right? My car has a 3500 stall, that may make a difference between our cars since yours is an M6.

 

Yeah it really doesn't cause it to turn more, it just redirects it through the muffler.


Yeah, automatics trick the seat of the pants meter, and make it more difficult to judge. I think I would be unlikely to notice a difference w/ an auto, there is just much more feedback on manual. Of course, doesn't matter b/c your torque converter can multiply torque anyway.

 

any gains in rwhp between plate/no plate/1/2 plate etcc?

 

I have heard there are small gains w/ the 1/2 plate vs. closed or open. I think they are minimal when dynoed like less than 5hp.

 

the tsp y has a good merge......but then it necks down from 4-3 1/2 to 2 3/4 for the pipe.....not good in my book......i bet thats where the rasp is

 

RASP is usually going to come from a few things. Firing order and resonance from an AL block have a lot to do with that noise. That is why you still get rasp with open headers. A dookie exhaust system will usually just amplify this already existing annoyance. Unless you truly like the raspy noise. Which I find hard to believe.

 

With no cats too, I will bet...

 

Speed Inc. says it's from an unideal Y-Pipe merge, and of course when you de-cat.