Race Engine Forum UK

Hi Guy,

I need your advice please on where to go from here to rectify my loss of power and torque on my Peugeot 205 gti (D6b engine 1.9)

I've had my full exhaust system replaced and now have lost power and torque (Not rolling road measure but rather can feel this loss when driving after the exhaust replaced)
Background to this- I've ordered brand new Weber DCOM carburetors, fuel pump, linkages and manifold from a weber agent here in New Zealand. Just awaiting the manifold to arrive in the country. I've not installed these yet. In anticipation of my installing all of this I decided to replace my exhaust system as It had been patched a few times, leaking and was well past use by date. The exhaust I had a local muffler shop install is 2 1/4 inch from the down pipe ( retained the original cast manifolding and downpipe) through to tail pipe. Looks about the next size up from original which I didn't measure but original was probably 1 7/8 or maybe 2 inch diameter.
Mufflers - In the middle I've now got a larger and longer than original center resonator ( bullet type straight through muffler) and just before the tail pipe a large oval straight through muffler ( well nearly straight through but has a slight kink in the path)
Results - The exhaust note is much deeper, a nice low note burble to it from Idle to about 2500. Quiet even just off the throttle. However from 3000 onwards the exhaust just drones in the background and I've lost low and midrange torque. Maybe even top end.

Solution to noise - the exhaust shop recommend installing another resonator at the very front near the downpipe to quieten it further.
Should I go ahead with this or go a smaller diameter pipe and rear muffler say 2 inch from the center muffler to the tailpipe else

To regain power - I need to know how the engine will respond after i install the webers. Will this bring the intake\exhaust back into balance and regain gas velocity and power ? Or is 2 1/4 just too big and will I need to go ahead and reduce the exhaust size. ?

Has anyone else had a similar issue

regards
Peter

Sure.

My money is on the centre box causing the problem, photos of the two boxes would help - size matters.I would not ordinarily run two boxes, one large rear one should be sufficient.
2.25" is not too big. But - with the two boxes you have fitted - if it doesn't evacuate properly now (based on your appraisal) it won't when you fit the Webers.
Don't overstate the value of 'resonators'. The placing and volume is critical - and yes, whilst the reduction in noise is real enough, my experience from dyno test is that any enhancement of lower-end torque is far outweighed by loss of torque higher up and power too. If anyone has the GC manual see dyno test P193.



GC

try fitting a 2" tail pipe to the rear muffler to correct the noise.