2.5CR exhaust??? is it worth doing without dump pipe??

Ho there guys and girls just wondering i have noticed alot of you on here have commented in other threads that you noticed more difference form changing the rear mufflers or dropping the exhuast off compared to what other's say is more gain from doing that than the dump pipe???? if that makes sense.

I do fabrication for cars and performance stuff such as turbo manifolds and intercoolers/piping etc for work and could esily make up my own cat back/dump back system but if there is not much gain from changing the dump then i'll leave that for now???? thanks

Hi VEE8SS,

I used to work in air and vacuum systems a long time ago and if my memory serves me well, I think it goes something like this.

Every bend, restriction and reduction in diameter adds pressure as resistance to the flow of the gas. If you have a straight through exhaust, every bend (assuming they are all the same radius) adds the equivalent of that pressure to the cumulative or compounding of each other bend.

If the biggest restriction is at the dump pipe ie right at the very start of the system, then once the gas passes the restriction the restrictions are less than the dump, then theorectically, the clean pipe after the Dump, will make no difference whatsoever unless the cumulative bends after the restriction of the dump equal or are greater than the restriction.

Ie, adding a straight through exhaust to a vehicle up to a restrictive Dump pipe is a bit pointless as the maximum restriction is still in place.

Please correct me if I am wrong. I hope this makes sense.

Cheers,

Deejay

I've recently replaced the exhaust on mine. I started with the muffler and worked my way forward replacing with 3" stainless. To be honest I didn't find that much difference until I did the dump pipe. Seems to give better top end power now, although I was hoping it would improve lag, but that doesn't seemed to have been the case.
Of course a dyno would be the only way to know for certain.
That was my results anyway.

You are spot on Deejay. I wouldn't do the exhaust without doing the dump pipe, have a look at these pics I posted.

http://www.navara.asia/general-tech-talk/2271-what-dump-pipe.html

Yes i understand the logic as I fit dump pipes to most imports and fabricate my own on a weekly basis through my business but I read soemwhere on here that a few people had removed the rear muffler and thats when they noticed the most difference. so i wasn't sure.

On another note do the D22 2.5L need to have a cat for the engine to function properly??? as If not I will make up my own custom dump and a "hollow" cat for the purpose for now as I can't foot over 650 plus freight for justa dump pipe and cat from beudersert exhuast when its soemthing i can make with a bit of time stuffing around. doesn't look like theres much room in there though either.

Hey VEE8SS,

A catalytic Converter is not necessary to make the engine run right, but it is illegal to remove anti pollution equipment from cars so fitted.

A Catalytic Converter is a ceramic honeycomb material designed to be heated by exhaust gasses until they glow and then burn the impurities from the exhaust waste. They work better when mounted as close to the exhaust ports as possible to soak up maximum heat from the exhaust gas.

So if you're not worried about legalities or Nissan Warranty, then remove it and make your own Dump pipe.

Cheers mate,

Deejay

I'll just second DeeJay's advice above, and point out that the fine if you're caught removing the CAT is somewhere in the region of $13,000. As improvement modifications go, that's an expensive one.

I realise the legal impliactions and Am lookign into a higher flowing cat than the ones tat exhuast shops currently provide on there systems. I am looking into the whole thing but it seems obvious I must have mis read when i thoght i'd read a few times on here that people have made the most difference by deleting or putting a straight through pipe in the rear.... thanks for your help I will post up some pics of what i come up with

I was told by a guy who works at cummins that its legal to remove a cat if you spend alot of time offroad as they can cause a grass fire.

Never heard of it before but worth looking into.

Dave.

Dave,

The owner's manual for my Commodore said I should not drive though long grass because the Catalytic Converter would set the grass on fire.

If there's an exemption for off-road use, then use it!

Ha Ha yeah the fines are in excess of $10000 per missing cat on the road though.... I know from my mates personal experience in his twin turbo commodore. they have 2 cats standard and we had removed both due to not being able to find a suitable cat that could hold up to the heat and power level without disintergrating and after being caught twice and being warned he ended up getting the fine and the car was deemed unregisterable until returned to stock standard.... but yeah that was a while ago now but i don't need that hassle.


HAs anyone got a picture of a standard cat and a cat that comes with a beaudesert system or similar they can post up here????

Hey VEE8SS,

If you can do fabrications, could you copy the Beaudessert 2.75" or 3" stainless dump pipe and sell here to members for a cheaper price than currently available ?
I have the 3.0 lt Navara and would consider buying if you can provide either dump pipe or complete system.

Cheers STC

Yes I could but I was thinking of making my own as it is over 650 to purchase a dump and cat from them just to copy... I will have to post up soem pics of my work so people can see

Any photos yet VEE8SS?????

i know there is a bunch of threads on dump pipes and exhasust systems so im gonna reuse an existing thread and hope someone can help me.

i have an 09 d22 and when i purchased the nav 2nd hand in mint condition over a year ago it already had an existing 2.5" system on it with sports muffler. i thought sweet another bonus not to add all the other stuff he ahd already done to it. my point is the factory dump pipe is still in tis location bolted behind the turbo and bolting onto the 2.5" system that was done.

now its come time to replace it and i now know why people charge arm and leg for full exhaust systems that require a dump pipe. they are an expensive lil unit. i have found the lowest quote to be $500 but thats reusing the factory dump and putting a flange and pipe on it. Sounds crap to me so i never rang them back. next was $550 with new turbo flange pipe in any size i wish and a 100 cell high flow cat installed anwhere i wish(installing near gearbox/transfer).

Is this $550 price a lil hectic? or is it what i am paying for since i havent done any exhaust mods of my own to the car? i dont mind the price and it sounds good to me. noone does a dump pipe that bolts onto the factory exhaust sytem so it has to be a custom jobby.

Rusty

I have been reading all of your comments thanks for advice, does anyone know of any good exhaust places in eastern suburbs victoria? who have had a full exhaust done thanks.