Can someone pleas help me. i want to know what the best way is to measure exaust back presure. Do i just Connect a boost gauge to the mid pipe and take a reading at WOT, or is there more to it what sort of figures am I looking for.

Thanks in advance.

Erdin

 

Drill and tap the exhaust manifold and measure it there. Bit pointless measuring it after the turbo unless you know your exhaust is really restrictive.

 

Thanks mate, A couple of more questions if im gone get my reading from the exhaust manifold before the turbo what sort of a gauge should I used as there is going to be alot of extreme exhaust heat there and what sort of figures should I be looking for. Also is it werth taping both runers or just the one, i assume both readings should be equal.

thanks

Erdin

 

aren't you more interested in the pressure after the turbo ? i.e the difference between atmospheric at the exhaust tip to just after the turbine section.

how you tap the exhaust is very important too, you want a sharp edged hole (no burrs but also no chamfers at all) that is perpendicular to the exhaust flow otherwise you will end up measuring some combination of the dynamic pressure and static pressure and not just the static pressure.

 

Yes after the turbo sounds more like what i am intrested in, what sort of figures should i be seeing. in a turboed car surly the less back pressure there is after the turbo the quicker it will spin up which is good.

 

for a silenced exhaust on a car ... not a clue.

 

Weld a piece of brake line to your exhaust pipe just ahead of whatever you suspect is creating backpressure.(Drill a hole of course) You could do it in a few places. The brake line will allow some cooling of gasses and metal so you can use clear rubber hose to run to a magnehelic guage. Mine is a 15" + or - . The less backpressure the better. Our race car exhaust barely measures a couple inches, of course it's over 100db.

 

Jgrewe, Thanks thats the information i was looking for il keep everyone posted on what i find out.

 

I cored an old spark plug with same thds as O2 sensor. Tapped it and used standard copper/brass fittings and 1/8" copper tubing. Make a "pig tail" in tubing to shake off some heat, then hook to hose and a low pressure gauge. Use instead of stock O2 sensor for testing.

 

Who was it that made the dual pressure guage? Was it Autometer or HKS? You could measure pressure going into the engine and exhaust backpressure as well...or IC pressure drop, whatever your heart desires. It was a BIG gauge though. I owned one for a bit.

 

My car has a boost gauge so im thinking I could use the reading from that to compare, but are you suggesting there should be a particular relationship between the pressure going in and the pressure coming out of the engine. You could try this company for the dual gauge but I don’t think they are very reliable as main broken dawn twice but that could be my luck. www.spa-uk.co.uk