Exhaust downpipe restriction??

[ian710]

I have 2003 facelift model and I'm doing a bit of maintenance to the clutch, rust repair and cat removal.
When I was removing the heat shield of the down pipe (that was falling off anyway) and I noticed the absurd restriction in the flex joints. The ID of the flange is about 48mm dia. and deep inside the flexy part it goes down to 34mm dia.    s:shock: :shock: s:shock:  
Does anyone know why this is?
More importantly can I hack it out without damaging the flexy joint?
This 34mm dia is even smaller than the manifold tubes???  s:shock: :shock: s:shock:  
I need all the 140hp I can get and this must be sapping quite a bit.



What were the Toyota engineers thinking?
Regards
Ian

[nahk54321]

What ever you do just be careful not to damage them flexipipes. You can't buy them separately (Just the flexis pipes) from Toyota, they sell the full part only which will cost you an arm & a leg.

But you do have a good point.

[Joesson]

I would like to believe that Toyota R&D Engineers had some understanding of what they were doing.
Have a look at:
 m http://www.gomog.com/allmorgan/exhaustbackpressure.html m

The reference to increasing velocity by restricting an outlet, analogous to putting a finger over the end of a trickling hosepipe, is probably a good summary.

[shnazzle]

I would like to believe that Toyota R&D Engineers had some understanding of what they were doing.
Have a look at:
 m http://www.gomog.com/allmorgan/exhaustbackpressure.html m

The reference to increasing velocity by restricting an outlet, analogous to putting a finger over the end of a trickling hosepipe, is probably a good summary.

This. Thinner = faster flow = pull more vacuum from the exhaust so gases get sucked out of the exhaust valves better. Fine fine balance between flowrate and capacity. Also assuming Toyota did this for a good reason

[mrzwei]

This is also the same physics that MAY have designed the inlet pipe for the air filter. The narrow bit may speed the flow which means that when you replace it with a Markiii pipe you may shift the torque curve up the rev range a bit.

Designers are usually cost driven though but it would still seem more logical to just have used a constant diameter pipe.

Delving into the depths of my antique tuning knowledge then I seem to remember that for maximum power up top  you need to open everything up but for maximum torque low down then you need to create venturi type restrictions.

(Or something like that!   s:lol: :lol: s:lol:  )

[cptspaulding]

What ever you do just be careful not to damage them flexipipes. You can't buy them separately

You can have new flexes welded in. I already did when mine were leaking

[Alex Knight]

What ever you do just be careful not to damage them flexipipes. You can't buy them separately

You can have new flexes welded in. I already did when mine were leaking

This. I had new flexis welded in too.