Throttle Response - Dump Pipes & Hi Flo Cats

[r33freely]

sorry there late... havent been online for a while

here are some pics of the cesracing twin dump i fitted to my R33

Dave

Edited October 23, 2005 by r33freely

[Bobjones]

Thanks for that...

Not a fan of the location of the O2 sensor...its angled below horizontal...they don't like working at that angle...

[r33freely]

angled below horizontal??

surley the sensor dosent know if its upside down or not?... could you please explain to me how it is that they dont work like that?

Dave

Edited October 27, 2005 by r33freely

[Bobjones]

Actually, the 02 sensor obtains condensation during initial start up,cold start, and if operated at an angle below horizontal then the sensor can fail quite quickly...

This is pretty common knowledge...the heater element also is liable to fail...

[r33freely]

mmm, thats interesting?

is there anyone that has had a sensor fail due to the twin dump?

got me worried now..lol

[siksII]

i am seeing if people are interested in a group buy for magic cats, so if you need one go to the group buy section and have a look

[MLCrisis]

The exhaust system does not give your engine it's backpressure.

The turbo does. By changing the exhaust system you allow the turbo to extract gasses more freely which means that turbo response INCREASES. Boost will come on sharper and you will be less likely to spike or overboost.

The smaller the exhaust system, the less boost you are able to run.

I know the above to be fact, however, I will say this:

I don't personally have dyno proof of when the power change is in a 3 inch system but I can assure you that it definately won't make it laggier. It will only remain the same or increase response.

<{POST_SNAPBACK}>

Sorry, mate. I know this is a bit late since your post, but your opening statements are basically wrong, although right in some respects. The whole of the exhaust system from the exhaust valves to the exhaust tip contribute to "backpressure". This is simply the resistance to flow that the exhaust gases experience before they exit at the exhaust tip, in other words the pressure drop through the system. This means that there is a base pressure that has to be made in the cylinder to enable flow to occur. That pressure is effectively the "backpressure". Naturally, the reciprocating motor overcomes this backpressure and then some.

The greatest contributor to the overall pressure drop is more than likely to be the exhaust wheel in the turbo, but every bit of pipe, every bend and every restriction plus the valve and ports in the cylinder head contribute to that pressure drop.

To say that the turbo "extracts" the gases is just plain wrong. The turbo would only extract gases if it was driven by something else. But the exhaust gases drive the turbo. Reducing the pressure drop downstream of the turbo exhaust wheel enables a higher gas flowrate and increases the relative pressure drop across the exhaust wheel, thus increasing the driving force to the exhaust wheel.

Your conclusion about responsiveness, etc., is correct - but you got there by the wrong route.

Or do you understand all this and you just didn't express it very well? Sorry to go on, but there are a lot of incorrect ideas mixed up with fact in explaining how a turbo works on the forums. We need to get it right. So if anyone can add to what I have said, I would welcome their input.

Cheers.

[Cubes]

Reducing the pressure drop downstream of the turbo exhaust wheel enables a higher gas flowrate and increases the relative pressure drop across the exhaust wheel, thus increasing the driving force to the exhaust wheel.

Thats spot on... I like to think of it being similiar to airflow through a radiator.

High pressure one side, low pressure in the engine bay will see good airflow through the radiator.

Higher the pressure in the engine bay the less airflow through the radiator.

Which I think is 'similiar' to what happens inside a turbo, lots of back pressure inside the scroll trying to escape out past the turbine wheel, place a low pressure area after the turbo's turbine wheel and you will most definitely have improved flow over having both sides with high pressure.

The gas will move faster as a result spool/response/power will improve.

Edited November 27, 2005 by Cubes