3" Exhaust/Question???

[ein bora]

Well I finally got around to installing a 3" exhaust on my 1.9 IDI - TD. The catalytic converter is gone now too but I'm not seeing any improvement at all, if anything I think it's worse as it doesn't seem to have the same amount of pep as it had before and now it seems like I'm really having to wind it out to get the thing moving? Could it be that it will work better once I do some other modifications. I am planning on the boost pin mod shortly and so for now I'm thinking it's a back pressure thing.  
Any thoughts appreciated.

[Jettagli16v]

If the car is a Turbo Diesel, (did they make a 1.9 NA? I am not familiar enough)
you need no backpressure at all.
Backpressure assists in preventing turbulence, and increasing the siphon effect in the exhaust gasses. In the case of a turbo, it smooths and pulls the exhaust from the head, so you want it to fall right out of the turbo.
Any backpressure on a turbo reduces the flow, and power.

If the car is NA, you can certainly put on an exhaust that is detrimental to performance. Restrictive bends, or too large a pipe will make more noise and less power.

I installed a 3" turbo-back on my 1.6TD, with the only other mods being a 3" intake, and MBC set at 19PSI, and the gains were appreciable.

Exhaust improvements are usually not a remarkable stand-alone mod for a car, but when you look at the whole picture, are essential to increasing the efficiency of your diesel powered air compressor.  That is one of the most restrictive elements on the car, and one of the places the factory robs you of power.
That being said on a NA car, stick with something like Techtonics or another nice fabricated system.

-Brad

[53 willys]

I think zero backpressure can feel like a low end loss...I have felt it on my cummins...I put 5" straight pipe on it...when it got to loud I put a 5" straight through muffler on it and gained some nice lowend pep...so yes I believe you when you say you feel a lose in pep. some backpressure can be good if it does not hurt the over all egts at WOT...but thats just my .02

[Vincent Waldon]

My opinion would be that you've discovered that the stock system is actually not that restrictive for a stock engine with stock fueling... at least not to the point of tripping the butt dyno.

On the other hand, I bet you would have noticed a reasonable drop in EGTs... a drop that now gives you room to start adding fuel safely.  With more fuel will come more boost and more exhaust.. exhaust that will now make its way out easier.

Great first step.. and your real fun is about to start !


Vince

[allsierra123]

I have wondered this as well As I am going to be running a 3" down pipe and straight pipe system. But some have mentioned that it would cause to much turbulence but I don't see how it would on a TD.

[RabbitJockey]

I have wondered this as well As I am going to be running a 3" down pipe and straight pipe system. But some have mentioned that it would cause to much turbulence but I don't see how it would on a TD.

 a friend of mine put a 4" downpipe on his wrx and they place that dynoed it told him it was too big and it hurt more than helped because of turbulence, i believe the turbine side of the turbo is only 2.25" anyway.  so i can see why it would create issues.  but i don't have anything to say solidly that it will hurt performance.

[1outof5]

can I jump in with another question?

is there any sense in a bigger diameter exhaust down pipe than the turbo outlet? a part from dropping EGT.

I've seen a lttle software that enabled to see the results of diameter  vs flow but I can't find it anymore (here or vortex ?)

[8v-of-fury]

can I jump in with another question?

is there any sense in a bigger diameter exhaust down pipe than the turbo outlet? a part from dropping EGT.

I've seen a lttle software that enabled to see the results of diameter  vs flow but I can't find it anymore (here or vortex ?)

Dropping the EGT would be sense enough, no?

Means you can drive it harder, make longer pulls, up the fuel some more.. :P

i think its a good investment if you like to drive it hard.