straight pipe losing power on TD? not enough back pressure

[rwnslux]

Hey guys, i have 2 exhausts for my 04 3Ltd.

one with a smallish oval muffler - sounds ok
one with a straight pipe - sounds wickid

want to run the straight pipe but it seems i loose power? feels like the boost hit that id normally get is softer, more linner power

does that mean i have gained more down low or lost up top, feels no more down low to be honest

mods are dump pipe and Tunit ECU

[jap]

Are both the exhausts EXACTLY the same except for the muffler?

[rwnslux]

pretty much, yet the straight pipe one is 2.5 and the one with a muffler is 2.25

weird

[lais817]

My understanding is you don't need backpressure in a turbo system mate, as the turbo is a restriction in flow as it is. The quicker you get that gas out the better I was taught Probably the only way to know for sure is do a dyno run with both exhausts, otherwise we're just stabbing in the dark

[Quinny34]

Is it an auto? If so I was told by the crazy thia racing lads that straight through 2.5 with a kink or s Ben is the go ... provides initial restriction then flows like a bought one...

[rwnslux]

I always thought that too. the turbo is just 1 big muffler so therefor no real need for a muffler. and the older 3Ltd have an s bend in them anyway

nar quinny its manual mate

[jap]

I'd say there is a bit of a placebo effect going on.

Throwing it out there, with the small pipe, more restriction, spool up higher in the rev range
Bigger pipe, quicker spool time at a lower rpm so it is not felt as much, but carries across the rev range

[fgk228]

I'd say there is a bit of a placebo effect going on.

Throwing it out there, with the small pipe, more restriction, spool up higher in the rev range
Bigger pipe, quicker spool time at a lower rpm so it is not felt as much, but carries across the rev range

X2

sounds like the boost curve starts earlier and is less aggressive with the bigger exhaust

[rwnslux]

Thanks guys, probably me just thinking its going slow but its not really

will give it more testing guys thanks

[LowVp]

i noticed this also with my turbo dunnydore ute when i went from 2.5" up to 3" but it was only under 2500rpm that i noticed it but i picked up more power up top and a quicker spool

[brusa]

The bloke that built the exhaust for my road bike told me "the larger diameter and more open flowing pipe you use, the further up the rpm the power moves"

[Drew]

You still need some back pressure in a turbo system. The people who made my exhaust said I'd gain power ant torque. I did, I got back what the 33's sapped out they also said don't replace the muffler with a straight through pipe as I will lose power. It's a 3litre 4cyl motor not a v12 quad turbo cummins lol it's all about flow and no restrictions, the turbo wants the least amount of back pressure possible but the motor still wants it's usual back pressure so a compromise has to be made, the trick is getting it right. It all depends on the amount of fuel and air going in. A turbo forces huge amounts of airn in and that all needs to get out as easily and smoothly as possible. A stock exhaust is made to comply with pollution laws, you can go a bit bigger and gain the smoother flow and more power, add more fuel and air and you can go bigger again to accommodate the extra volume of gas needing to get out.

[Alby]

I was speaking with a well known diesel performance specialist today and I asked him about this subject and how he explained it is that if you get too big a pipe you end up loosing the air velocity because the turbo cannot maintain a good air flow so you actually start to create a restriction in the system again as you are back to pushing the exhaust out rather than utilizing the velocity that you had before. Similar to water through a pipe, bigger pipe same amount of water and you lose the flow velocity.
So with the larger exhaust you get the most benefit at the higher revs when the turbo is spooled up. He then told me of a 200 series that he fitted a 3 inch system to that he did not recommend but client insisted. The vehicle lost towing power down low and used 4 litres per 100 more fuel.
He suggested that there is nothing much wrong with the OEM system just change the muffler for a hi flow one on the D4D.

Sounded like a good explanation to me and pretty much is in keeping with the experiences that have been posted.

[rwnslux]

thanks for posting that alby. my dump pipe is only 2.5" so not much point going any bigger than that

[Luxasaurus]

Now im rather afraid of getting a straight through

I did a fully sick custom home job, Cut my muffler off and its just a noise machine now, It doesnt pull as hard, Miller noticed as i was driving behind him i started slowing up more than i usually do

Sorry if im stealing the Thread Rwns but now im curious

So say for an 04 3l Turbo diesel, getting a 3' is a bad idea?

I want it to sound like a Mac when im giving it the beans and a louder whistle from the turbo, but i want power gains too!!!

[jap]

Put a Cummins in it

[rwnslux]

i hear what your saying Luxasaurus thats what i mean.

i think im going to go with the 2.5 bit keep a tiny muffler on the rear

[Quinny34]

2.5 minus cat and straight through for the win!

[rwnslux]

mine never had a cat, even with stock exhaust =S is that normal lol

[jap]

Not sure if the earlier models had cats, thought they come in when the hilux went aftercooled?