Real drop in mpg after inlet manifold change

**signum_rob** · 6th February 2013, 22:08

I hope someone can help as its really bugging me, i recently replaced the inlet manifold on my cdti 150 including new gaskets etc, all went back together fine. She started at the turn of the key and runs like a dream. No smoke on startup which i was getting with the old worn manifold, picks up fine on the pedal. But before the change the computer was saying 49 mpg, then with taking the battery off for a few days and replacing with new inlet the computer now only shows 43 which seems quite a drop as it should have gone the other way. One thing i have noticed is a slight whiff of exhaust on startup and thats it. Other than that she runs like a dream. Can anyone help???

**wickedwillie** · 7th February 2013, 13:48

I would reset the trip, I would then take it a long M Way drive (20 odd miles) at a fairly constant speed. If you get less than say 49 MPG, I would say there is a problem. Maybe you just need to accumulate more miles to get a true Trip reading.

**GazVXLINE170** · 7th February 2013, 14:00

Stupid question but have you torqued all bolts up correctly? A drop in mpg and a whiff of exhaust sounds like a leak coming from the EGR valve area. Only a guess though.

**signum_rob** · 7th February 2013, 23:37

Well ive had a good look underneath and turns out theres a break in the exhaust flexi, maybe coincidence maybe not but would this lower the mpg, seems to rasp under acceleration also?

**GazVXLINE170** · 8th February 2013, 00:00

Originally Posted by signum_rob

Well ive had a good look underneath and turns out theres a break in the exhaust flexi, maybe coincidence maybe not but would this lower the mpg, seems to rasp under acceleration also?

Yes possibly. A custom exhaust place should be able to sort it for £80 roughly.

**Sebastian** · 8th February 2013, 00:07

Originally Posted by GazCDTI150

Yes possibly. A custom exhaust place should be able to sort it for £80 roughly.

also look on carparts connexion mate , bought new flexi from saab dealer for 65£ delivered

**signum_rob** · 8th February 2013, 01:08

On the signum its not welded to the cat section so have just bought connecting pipe and flex for £36, hope this sorts it. If not ive read somewhere about egr cooler pipes, new one to me.