X Force Or Nizpro Exhaust? Plz Help

[JETURBO]

^^^ this guy ^^^

[old_mate]

Oh dear

[Impellor]

Turbo cars don't need any back pressure.. They are completely different from an NA engine where engine displacement comes into play when picking the right exhaust..

In short for turbo cars:

Bigger = Better

To the OP this doesn't address your question, for that I apoligise, but it may be of some value to you.

Generally what you are saying is correct. But I'd just like to try and explain a couple of things. Firstly, for a dyno bigger, is definately better. This is based on the fact that you don't have any pressurised air moving under the car. So exhaust gas cooling is very, very minimal. But in the real world when driving on the road, the exhaust system has a large surface area and is being subjected to rapid (external) air flow. Which is a very effective cooler, as we see many motorcycles and past cars such as Porshe, only using air to cool an engine. So what we are seeing is the exhaust gas will be starting to cool as soon as it leaves the cat. By reducing the pipe diameter (further down the system) you are able to maintain the heat/ speed (veloscity) that the exhaust is moving. Because you can push more volume through a small hole if it is travelling at a greater veloscity. By having an exhaust the same size all the way through, as the gases cool they slow veloscity. So even though you have a larger exit point, it doesn't equate to better flow in a turbo engine, due to the much higher exhaust temps.

Just on a side note, I am wondering whether a better designed exhaust could actually assist with helping to maintain/ stabilise boost pressure.

Hopefully with F1 cars going back to forced induction (1600cc) next year, there will be much greater advances with turbo technology, that at some stage this info will filter down.

But I don't believe in this case bigger is better. A balanced system will provide a better and more consistent result.

As far as I'm concerned, I believe that Ralphie's exhaust (in its entirety) is probably the benchmark at this point in time.

Cheers

[xr6t_ute]

Cheers I still disagree

[Never had any say Panda]

So bear with me.. But following the typical "Heat Expands, Cold Contracts" theory.. (I got something out of engineering here)..

So due to this rapid cooling your exhaust gases are contracting (ie: taking up less space), so by tapering down the size of the exhaust you maintain a semi-constant velocity of the flow of gas..

Which would also effect the noise the system makes as there are less gases bouncing around?

[JETURBO]

Iam bouncing around

[mic]

Cheers I disagree too cheers the turbocharger itself creates back pressure and the only reason the stock exhaust clamps down 2 inch is to keep it quiet. Cheers chairs chores ha

[Ralph Wiggum]

Backpressure and reduction in diameter to maintain velocity = not same/same. Where did I mention the reduction in diameter adding in creating backpressure? I does close to the opposite, it stops the high temperature gas that is travelling at a higher velocity from tumbling into the slower moving cooler gas.

In a forced induction engine that has two states, idle and WOT full boost pressure then yes no exhaust is better than any exhaust, but our car don't spend there lives in either of those two states. They spend 99% of there time in transient state and this is where maintain the velocity is important

If the system is good enough for the like of Jim from Tunehouse (who originally commissioned smb to produce the step down system) and Brian Lord's (BCL) 600 odd rwkw F6 is good enough for my humble old BA.

Here's a tip whether you like it or not ALL exhaust systems created back pressure, otherwise the air wouldn't come out the end.....

[JETURBO]

I was reading (I know rite) somewhere a n/a engine needs to see close to 7psi worth of back pressure for optimum operation but a turbo charged car needs around the 2psi of back pressure ( so it still needs some )

[Ralph Wiggum]

*right