Fairhurst111

Hi,

Can anyone tell me their views please.....

The exhaust is blowing slightly at the flexi pipe (between CAT and back section).

Would this cause any power loss / lesser performance ? Im wondering if it effects the turbo in any way ?

Looking forward to your response

2000TLondon

I'm sure it affects the performance. It wouldn't necessarily affect the turbo as such, but as the gasses aren't being expelled properly, you will start to notice a loss in power, as I remember......

J4CKO

iTrader: (1)

I wouldnt have thought so, turbos dont rely so much on the exhaust being tuned, just a way of blowing out fumes as quickly as possible, especially with a cat, however sometimes a lack of back pressure can cause oil to blow past the turbo seals, what will be apparent is a bloody annoying blowing noise and fumes coming up the side of the car.

That may all be bollocks, just my current understanding.

Fairhurst111

Im not sure - I cant see it making a huge difference but I have had conflicting views from 2 saab specialists. The cars in for a new pipe this week any way but im curious to know. one dealer said that it wont make much difference and the other said because it is loosing pressure through the leak the turbo struggles to maintain a constant pressure......any other views ?

Mark in Ireland

It won't make any difference apart from noise from the exhaust.
Don't go to the second dealer again as he doesn't know what he is talking about!

Fairhurst111

cheers for your response

fatscoobyfella

It will make a difference.The lambda sensor is smelling nice clean air being pulled into the exhaust through the crack in the flexi,so it richens the mixture,because it thinks its to lean..
Basically you will have rich mixture a lot of the time,so expect minimal drop in MPG and performance...But it will make a difference!!!

Mark in Ireland

Quote...The exhaust is blowing slightly at the flexi pipe (between CAT and back section).

The lambda sensor on Saabs is usually located on the bend from the turbo, the leak is underneath the car about 2-3 ft away, no way will it be affected in this position.

fatscoobyfella

Mark...Yes it will..Even if your backbox is blowing,the lambda will still smell the air ingresss.The blowing of the exhaust doesnt have to be "downwind" of the sensor.

Believe me mark as a Motorsport Diagnostic engineer its my job to know these things

Fairhurst111

interesting debate here...thanks to all for responding. The pipe is being done tomorrow so I will soon find out. Cheers

Mark in Ireland

Not doubting your experience, but I cannot get my head around the fact of how to get air to ingress into a pressurised system and then move upstream against a considerable gas flow. My 2.3 Saab has a straight thru 3" system so using your theory my lambda will be seeing oxygen from the open end....or am I missing something?

fatscoobyfella

Ok mate,

Simply a Lambda sensor is built to see air,that is its job.But each Lambda is different,and OE exhausts are built to keep the Lambda for there specific vehicle in OE spec..

So,lets just say that a Lambda for your scoob is designed to recognise a certain amount Co 2 and O2,inc the hole in the end of your exhaust.When more air is introduced into the system,the lambda instantly recognises this,and reacts accordingly.The sensors are very sensitive,they have to be to do there job.The exhaust on any modern car has to be completely sealed(obviously not the tailpipe),for the lambda and cat to work correctly.

As for your question as "how does the air get into a pressurised system"?
Well what happens is the "venturi effect".When pressured air is passed quickly over a tiny hole,it draws air into the pressured pipe.Bit like old carb technology.

The amount of air drawn in may well be tiny,but it will change the balance of the gasses seen in the complete exhaust,and the sensor(s) will react to it,wherever they are in the exhaust.Admittedly,some cars do react more than others.

This is why so many cars fail emmisions test for MOT that have blowing exhausts..Its not because of the noise of the exhaust,its because of the way the sensors are acting on recognising the fault.

HTH..

Mark in Ireland

Thanks, excellent post!

fatscoobyfella

Glad to be of assistance!!