Thread: Fitting the thru pipe to replace the muffler, worth doing?

I brought a second TD5 with a bent rod to use up a spare engine and it had the centre silencer removed. Despite my doubts it is great, no lag at all and heaps of power, fuel economy is ok at about 11.5 and the noise (drone) is not the problem I thought it might be, however I haven't done a long trip yet. (EGR removed as well)
Nick

Hand on heart I can't say I noticed a massive difference, I fitted a decat down pipe and straight through mid pipe ages ago.

Cruising I don't really notice the noise, wind noise with roof rack, talking and stereo etc mean it doesn't feel noticeable.

However, wide open throttle certainly is a lot louder, probably a bit too loud if I'm honest. If you are keeping the cat (if you have one) that may knock a bit of noise off and make it acceptable all the time. I have been considering putting the midbox back in lately to see what effect it has on EGT and driving.

Originally Posted by Pippin

I brought a second TD5 with a bent rod to use up a spare engine and it had the centre silencer removed. Despite my doubts it is great, no lag at all and heaps of power, fuel economy is ok at about 11.5 and the noise (drone) is not the problem I thought it might be, however I haven't done a long trip yet. (EGR removed as well)
Nick

Yes I was surprised how quick the turbo spooled up without the centre muffler. I have a boost gauge and it was noticeably quicker on the gauge. I actually had to wind back the wastegate, as I had adjusted it prior to the pipe going in, for it to sit on 20psi with the throttle wide open. It rarely did get to that. However, with the pipe in, I was hitting it all the time on hard acceleration, where I wasnt before.

In terms of performance gain from a seat of pants measure, I didn't really see anything significant though. It is a bit noisier, but I've gotten used to it. For $200 (I paid $195), I would say do it. It does sound better at idle. Get 2 new bolts for the front and the triangle gasket for the rear. Also just watch the downpipe doesn't move and rub on heat shielding before you tighten everything up. Otherwise you will need to undo it all and realign it like I had to

I also replaced all the rubber hangers (4 of them) they are only $4 each.

Another tip to get the pipe out and the hangers off and on. Get some silicon spray and spray it inside the hole in the hanger where it pushes onto the pin. It will make it a whole lot easier to get them off.

I cant say I really noticed any difference to EGT though.

I have a decat, silicon hoses and EGR removed (if that makes any difference)

I drove my td5 for seven years with a straight through pipe.

It immediately improved everything but after a while you just get used to it. I removed my egr at the same time, turned the wick up on the turbocharger as well.

did about 200,000km in that mode.

my fuel usage was more like 9-9.5 litres/100

with the taller tyres, rpm at 2000 I could get down to 8's down the newell and across NSW.

Don't do it if it's an auto and you tow regularly. Or if you have a significant other that each time it hits the right revs to drone will remind you that it wasn't necesary and is a pain in the arse. It might take some of the shine off and make you get a someone at a muffler shop to cut your nice new stainless straight bit of pipe and insert a muffler just to shut the other half up. Because the noise she was making was way worse than the drone. It will also cost you significantly more to do that. Which you may also be reminded of by the other half from time to time.

Fit a hotdog not a straight through. Benefits without the drawbacks.

Not surprising that you have improvements...

Back pressure on valves in turbo engine, is no concern... The turbo provides plenty so no burning valves with removing muffler...

The muffler on a turbo engine is to quieten the noise, Thus if you want the noise limited but a power increase then look at having a system that breathes well but makes the vehicle quiet...

To explain how much a muffler can effect power, I removed the mufflers on a truck I owned years ago... Gain another gear on hills and great fuel economy...But you could hear me coming from 3 miles away... Luckily in my case, it was all bush work, but in the city, the other drivers would probably complain about hearing damage....

The drone in the cab of a vehicle is probably the hardest to avoid, sound coming back into vehicle can be negated by using a down facing tail pipe and sound deadening in the floor...

Increasing pipe size and then using good quietening mufflers, may just give you the grunt you want with peace from the passengers seat...

Have fun....

I am prepared to believe that a straight through pipe might make the turbo behave differently, however, I would be very suspicious of anecdotal claims about how much better the vehicle performs.

I am convinced that it is natural for people to believe that if they are making more noise, they must be going faster or accelerating harder.

I have seen this phenomenon with motorcycles and with kayaks. Back in the 70's I was assured by a Honda SL125 rider that his bike went a lot better since he fitted his (louder) Pascoe aftermarket exhaust to his otherwise standard bike.. He was the same weight as me, so I line up my completely standard SL 125 beside him and we did several drag races.

There was absolutely no difference between the bikes on any of the runs. All he could say after that was, "Well it sounds better than it used to."

I have heard claims from a number of people about how fast those Hobie kayaks are with the Mirage pedal drive. None of them have been able to even get close to keeping up with me in my sea kayak. Even a couple in a double using both the pedals and their paddles couldn't keep up.

Their hull shape is so inefficient that as soon as you try to go fast they create a lot of gurgling noise and the loudness of that noise fools people into thinking they are going fast. They aren't. They are just stirring up the water a lot and making a lot of noise.

I'm sure the same effect can be seen with vehicles. The one making more noise just naturally seems faster.

That doesn't mean that there can't be an improvement with a louder exhaust, but it does mean that it is possible to be absolutely convinced of an improvement when there isn't one or to be fooled about just how great the improvement is.

(Maybe that explains the popularity of Harley Davidsons.)