I ceramic coat all manifolds, turbine housings and DPs on all my turbo vehicles. The positive effects on power, heat retention, spoolup and consistency are amazing. Also believe with everything coated you can venture up a size on the turbine housing and retain spoolup close to what a smaller housing yields. Don't understand why more people don't cash in on the benefits of heat coatings. Just the added life alone to underhood components alone is worth the cost.

 

ok so im gonna be ordering the piping to make my exhaust. I still cant decide im thinking 3.5", im gonna be using the stock evo 8 turbo for now, so im thinking 3.5" with a 2.25" dump tube. and having the turbo and stock manifold portedthen wraping everything with exhaust wrap
and thoughts?

 

I have to agree with this. You have to think as scavenging having 2 'stages'.

First you have your manifold and the size of that tubing will effect the scavenge effect on your engine. The less scavengine going on, the piston is wasting power not going to the crank, rather pushing exhaust out.

Then you have the tbe, the less scavenging going on, the turbine blade is wasting power not going to the compressor speeding up, rather pushing exhaust out.

So just putting on a 4" cutout (big opening, short exhaust) as some suggested, you will have no scavenging at all, and the turbo will be working relaly hard to push that exhaust out, as opposed to it be assisted by the exhaust being sucked out... the syphon or scavenge effect.

Of course too small us bad too, as you have plenty of scavenge effect, but not enough for the flow of exhaust, and now the turbo is pushing against the slow scavenging exhaust.

Lets say you have a tub of water and you put a hose in it. You suck untill the water is syphoned out, lets say with this dia. hose, the water syphons out at 5psi. But since there is no one sucking the end of the hose to start this syphon, the syphone has to be started with the pump. So the pump will work hard untill 5psi is achieved, once 5psi is acheived the syphone will start to suck water out and aid the pump putting much less load on the pump.

SO at 5-9psi the pump is still only pumping 5psi worth, at 6psi the pump has more of a load than the 5psi, but still very little load. And 7psi slighly more load ect. Then there is a point, when you try to push the little 5psi pump up to 10psi, now this little pump just can't do that, it pumping against the syphoned water and it really loads the pump down and can damage it.

Now put a hose twice the dia, it takes 10psi for the syphone to occour. so at 3psi its working hard, 5psi harder 8psi very hard, but once 10psi is reached, it has a very low load on it. And it can last up to 20psi before you start to damage it.

Or lets just put the pump at the top of the water level. It might only take 3psi to push the same amount of water out, and it will never change, the pump will stay the same load throughout the prm range. This is just like a cutout. It doesn't have the medium load, to low load, to high load, it just stays medium. Or if your exhaust is too big, it will be just like a cutout and it will be medium load, untill enough pressure builds and allow the very high load untill you get enough pressure to start scavenging, at which case it will dramatically lower.

An engine is the same way, the engine is a 'pump', and the turbo is a 'pump' and exhaust is a fluid as water is. The more load you put on the engine or turbo expelling exhaust, the less energy can be used to turn the crank/compressor.

There is only one optimum size for exhaust, but since we don't have variable exhaust diameters, we chose what is best.

If you go too big, you are only hurting your low down tq, BUT if you go to small you cold damage things, but as long as you don't reach that point, a smaller dia exhaust is better for your down low tq. and will slow your top end power, and then damage your engine if you go too much.

One thing is for sure on any exhaust, always stay the same dia through, OR start small and end big, never start big and end small.

But the TBE has nothing to do with cylinder scavenging, or direct engine tq, just turbo scavenging, and turbo spool... which could be seen as tq.

 

bump

 

Since this thread was bumped and I just finished up a catback on my car, I figured I'd post up a little more on this. Bad form I guess to quote myself, but it's worth restating.

The catback I built I used ONE 3" 90 degree bend and had probably 15-20 degrees left over from it. Further, I used mandrel bends with a 9" bend radius and they fit like a glove. Could not have asked for a better fit to the car IMO. The 9" bend radius has about the same pressure drop as a striaght piece of tube of nearly equal length.

Of that 70-75 degrees of bend I used it included about 20 degrees just to make the tip come straight out the back. Had I gone "JDM YO!!!" it would have only taken 50-55 degrees of total bend, but I think that looks like ***.

It feels like the catback with hangers weighs about 6-7 pounds as it's mufflerless and made of aluminum.

 

Pics? old vs new?