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Discussion Starter #1
It was the best of times, it was the wost of times.....

do I have to loose torque for sound. Can the torque fairy dash a little horsepower in for my lost torque. Is their a happy go lucky medium. Where do babies come from. I am lost.
 

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whenever you do exhaust working, you will lose torque, BUT you will gain top end, so it's a trade off, throwing x pipes or such on there keeps some torque i hear, anyways, i don't worry about it much cause what you lose in torque you gain in top end, that's what everyone fails to mention,
 

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Have the Torque Fairy drop in some 3.73's ... that should fix the low end loss feeling... :) or if you dont like that idea a nice Higher Stall TC should do the trick....
 

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Jason said:
Have the Torque Fairy drop in some 3.73's ... that should fix the low end loss feeling... :) or if you dont like that idea a nice Higher Stall TC should do the trick....


o yeah, and under drives do provide some low end torque gains too if i'm not mistaken :)
 

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crossovers (x's and H's) haven't helped the torque in any tests I have seen
 

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Discussion Starter #6
I think we are in desperate need of an "Invention":D
 

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what tests have you seen?....im pretty sure they do raise it slightly.....i have nice low end tq still but i have almost 0 mods
 

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birdmandan said:
I think we are in desperate need of an "Invention":D
The proper name for the "invention" of which you speak is "roots supercharger". LOL!!!

Mmmmmm, Forced Induction.... (wipes drool from chin) :znanner:
 

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There are some newer BMW's that have an electrically operated bypass valve in their mufflers that promote low end torque but open up at high revs to boost high-end power.
 

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I have a Car Craft laying around here somewhere with an exhaust test in it, and I saw one on Horsepower TV or something once too. The cross overs gained power but lost torque.
 

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Embalmer said:
There are some newer BMW's that have an electrically operated bypass valve in their mufflers that promote low end torque but open up at high revs to boost high-end power.
Exactly. It's like what the motorcycle industry did, starting with the Yamaha EXUP (exhaust ultimate power valve). It allowed radical cams with good overlap (good for top end) to be combined with a large tube, open exhaust (also good for top end) and a throttle actuated valve that opened as the throttle and rpm increased. So at low rpm use, it restricted the exhaust flow, and limited the amount of reversion the pressure waves underwent, while allowing the valve to go to full open at higher rpm (and exhaust velocity, where reversion wasn't a factor) to get full hp. There have been a few cars to do something similar, but I haven't payed much attention to the results.

Works so good on motorcycles, that now, almost 14 years later, almost every sport bike manufacturer (to include Buell, if you consider that a sportbike) is doing something similar.

Anyone want to give it a try? You'd be famous (or something).
 

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shouldn't be that hard right? the eec already grabs data from the TPS, should technically be another "if, then" statement no?
 

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Embalmer said:
There are some newer BMW's that have an electrically operated bypass valve in their mufflers that promote low end torque but open up at high revs to boost high-end power.
BMW's have had that feature for quite a while. It really doesn't have anything to do with promoting low end torque. it is really for the European sound laws. It carries over to the US and the torque thing is just kind of an additional feature. :cool:
 

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bigmarty said:


BMW's have had that feature for quite a while. It really doesn't have anything to do with promoting low end torque. it is really for the European sound laws. It carries over to the US and the torque thing is just kind of an additional feature. :cool:
If you look at the motorcycle manufacturers reasons for using it (with the exception of Yamaha, who started using it in the 80's for emissions of all things) they are using them to promote mid-range torque and little to no regard to sound. Motorcycle exhausts are quiet, and non restrictive, and don't hinder most motors from making more horsepower per litre than most production car motors. However, midrange torqe has always been a concern, as the rider can't always be turning over 8000 rpms.

However your sound statement does hold credence, and these valves in most iterations do in fact produce a more quiet exhaust at low rpm.

And with regard to JamesD statement, you are exactly correct, as Yamaha started to go with a combination of tps and rpm to determine how far to open the valve in 1997 with the YZF 1000R, and into the YZF R1. I'f you want, e-mail or pm me and I can point you to some websites that have detailed information on these. I really don't think it's impossible, but I'm not sure how much would be to gain on the normal car, due to bore / stroke ratios etc. But heck... I guess anything is possible with enough effort. :thumbsup:
 

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I just put in a 2.5" dual set up on a few weeks ago and I was expecting to feel a loss in the lower end but it sure feels like I picked up power all the way through the
RPM range. Sounds strange but that's how it feels.
 

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scott said:
I just put in a 2.5" dual set up on a few weeks ago and I was expecting to feel a loss in the lower end but it sure feels like I picked up power all the way through the
RPM range. Sounds strange but that's how it feels.
Heck Scott,

With the setup you have... I wouldn't be surprised! Nice setup... must have taken you a while.

But, the answer in your case may have been that the exhaust restriction was already holding you back (with the bigger injectors, PI stuff, TB etc).

Now let's put a true dual 3" setup on there and watch what happens to your bottom end :)

I thought I would drop the bottom out on my 357 in my Bronco by putting hi flow cats and dual 2.5" pipes, with Dynomax Bullet mufflers. But I swear it gained all around power, and I actually picked up almost a full mpg city (woohoo.... one more mpg and I'll have double digit city mileage). Apparently my 2" duals and turbo mufflers were holding some back. I don't honestly know the exact "mix" of what it takes. I guess that's why folks like Rousch make all the big bucks... and I'm still getting paid by the taxpayers, and tinkering on the side :)
 

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Fzrdan. You maybe right and the old exhaust was holding me back. I should have mentioned that I still have the 2 stock cats so that might be giving me the back pressure I need. ( ?? )
 

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Like I said Scott, I really don't know the mix. I've spent countless hours talking to engineers and engine builders, and I still can't do the math on it. It sucks that we have to figure things out by trial and error sometimes... but someone has to be the pioneer. That's why I get p1ssed when people start the "that won't work with your combo" replies. What if I do something subtle that is different, and it produces results?

Glad yours worked out for you, and I hope it stands as an example of something to try.
 

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backpressure is overrated

Just ask dom when he put a offroad exhaust on his mustang and gained horsepower and torque from his stock setup.

Till you dyno it calibrated *** hairs aren't as accurate as you think they are.
 
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