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exhaust system

 
  #1  
Old 07-28-2005, 03:45 PM
racer956
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exhaust system

I am buying a exhaust system for my truck and am looking at the 4 inch turbo back or the five inch turbo back I am told with the five inch I will loose tourque, Is this true or is the five inch just a waist of money please let me know thanks
 
  #2  
Old 07-28-2005, 04:03 PM
arninetyes
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For performance with a nearly stock engine (stock turbo, injectors, etc), the 5" is unnecessary and will NOT improve performance. Is it a waste of money? Depends. I just liked the way it looks and sounds, so for me, it wasn't a waste.

Does it make less torque? Yes, and no. I have talked about this with people who know MUCH MUCH more than I do about making diesels run. They say that you will not lose torque because the necessary backpressure for the engine is provided by the turbo, and is unaffected by the exhaust system after the turbo. Of course, boost CAN be affected by what is after the turbo, as a restricted exhaust can prevent proper turbo spin up - plus the usual EGT problems.

That having been said, here is my take on how the 5" affected my truck - actual torque has not been reduced. Cruising down the road, whether using stock tune or the Edge Evolution tune, torque is there and plentiful - very little throttle is necessary to keep it at 70, and very little push on the pedal runs it past 80 very quickly.

Now, let's talk about off-idle response - There has been a decrease in off-idle response. I have to push the pedal farther to get it moving, but once it starts moving, all the torque is there. Is this because of the 5" exhaust, or the 4" DP? - or both?

Of course, I have discussed this with one expert. He said to try disconnecting the batteries and 'reset' the computer. Let it learn the different flow characteristics of the new exhaust. He said that may take care of it - or most of it. For best effect, a custom burned chip would take care of the rest.

Should you get a 5"? No - if you want to save some money and performance is all you want, say "NO" to the 5 - inch. Put the extra money somewhere else - like the transmission, as you will need to sooner or later.

Me? I like my 5". Very happy with it. But that is me. I have a plain, unnoticeable truck. It is the only extravagant thing on it.
 
  #3  
Old 07-28-2005, 05:01 PM
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nice info arninetyes... i just want to know if you know... what is the difference in sound between a 4" system and a 5" system...?
 
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Old 07-28-2005, 07:38 PM
racer956
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exhaust

wow thanks for all the info
 
  #5  
Old 07-28-2005, 11:45 PM
arninetyes
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johnny8, unless you hear one next to the other - not much. But I happened to hear a couple of trucks and just liked the slightly deeper tone of the 5".

However, I have to say that the sound can be altered radically by the muffler design, probably even more than by the size of the pipe. Mine sounds a lot different than the last 5" I heard more airy, less rumbly. But other things contribute to sound, too. I have a stock turbo with stock compressor wheel. So, it doesn't whistle as much as most modded trucks do (it is on my list) and lends an 'airy' sound to the exhaust.

As a result, my truck, at some throttle settings, sounds very deep, very smooth, very nice - at anything over 1/2 throttle it is very authoratative without the bark of a straight pipe. At some throttle settings (very light) it almost sounds like a jet with lots of air passing through the exhaust backed up by the turbine whistle.

Then there is the exhaust flutter - apparent at certain low throttle settings, but only if the right window is open. If the right window is closed and the left is open, I hear no flutter at all. If both are closed, I hear more turbo whistle then stock, but when pushed there is a very deep tone that wasn't there with the stock exhaust.

Hmmm. Best I could do. I've tried to record it, but my recorder sucks and doesn't even get close.

I could have done just fine with the 4". I just got carried away...
 
  #6  
Old 07-29-2005, 09:01 AM
Mark at DPPI
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racer956,

The issue is on stock trucks only, we sell a lot of 3.5 inch down pipes for stock truck system that then go to 4.0 inches. The stock truck with a 4.0 is a little sluggish off idle, although very and I mean very few people notice it. The typical exhaust buyer is going to get or has already gotten a programmer or chip and then the 4.0 is the wonly way to go. The back pressure thing is a hoax, none of our trucks need back pressure to operate at their best. People have debated it for years but it just not necessary at all.

99% of our customers get all the sound/tone they are after with a 4.0 inch system, we do sell 5 inch systems and they are great but be prepared for a little more volume and in some cases drone as well. It also makes a big difference if you get a 5 inch system with a real muffler, lots of them have no packing material and the muffler while also a restriction because it has no packing turns into a "drum" and resonates too!

Call us if you have any questions etc, we stock all the MBRP 4 icnh systems and have 5 inch systems available too.

Mark @ DPPI
 
  #7  
Old 07-29-2005, 10:51 AM
racer956
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Thanks I will let you know when Im ready.
 

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