RealQuick

iTrader: (14)

I am looking to log back pressure thru hptuners and was wondering what sensor you guys use for this? This sensor will go on the downpipe to see how much of a restriction my single 3" downpipe is.

thanks!
Jon

truckdoug

iTrader: (25)

backpressure (also called drive pressure) is usually measured before the turbine.

I put mine as close to the turbine, but before the gate, as possible.

I use the $16 ebay 0-100psi .5-4.5v sensor and had good luck with it. I did add a .045" restrictor and turned the sample rate down in HPt for that sensor to smooth the exhaust pulses.

RealQuick

iTrader: (14)

Thanks for the info. I may put one pre turbo, but post turbo single 3" dp is what I am interested in at the moment.

forcd ind

iTrader: (7)

Curious what kind of numbers you are looking for on back pres.-what's good, what's bad.
Thanks

Nali6.2

I used a 3 bar map sensor in the collector just before the turbo. I also used a diffuser to try to kill egt before it hits the sensor. I don't think ive seen people monitor downpipe pressure

svslow

Ideally it would be 1:1 with boost pressure, but that is hardly ever the case. A decently matched combo would be in the 1:2-1:5 range.

dburt86

iTrader: (2)

If hes talking about post turbine pressures, i would think as close to 0 as possible would be ideal.

I dont know at what point you decide that an exhaust/DP has too much BP tho.

93camaro_zzz

iTrader: (13)

Just curious, why would you want to put it pre wastegate? I would figure that I would want to know EXACTLY the pressure that is driving my turbine, not at any other point in the system.

3 window

iTrader: (1)

Is it really gonna matter? Backpressure is going to be the same anywhere in the system.

roastin240

iTrader: (13)

I have done it exactly as truckdoug shows...coiled copper tube to dissipate the heat that was feeding an omega pressure transducer (much more expensive than the ebay ones so I dont recommend them unless you get them free like me). The pressure transducers typically start to fail at like 80 deg C if I recall...

And yes pressure should be pressure upstream of the orifices (which would be the turbine and the wastegate)....doesnt matter if its before or after.

stevieturbo

Not necessarily.

If the sensor was literally beside the gate...there is no question it will read lower when the gate is in operation than if it was placed say at the furthest point on the exhaust manifold close to an exhaust valve.

And obviously pre turbine pressure will be different to post turbine pressure.

As a compromise for pre turbine pressure....install it literally pre-turbine.

Ideally post turbine should be as close to zero as you can get, although even 1, 2, 3psi isnt terrible.

Pre turbine...it seems single setups suffer far more than twins. On my twins rarely does it exceed 1:1 ( MAP vs EMAP ) except at the very highest loads.
So an efficient setup is very doable. I'm still going to try larger turbine housings anyway.

I'm sure some will see much higher pressure ratios though and perform superbly.

truckdoug

iTrader: (25)

the reason i stated "I put mine as close to the turbine, but before the gate, as possible." is because my gate is right on the turbine housing.

placing it after the gate would be kinda difficult.


with my 5.3 and the "OG" gt45 I was seeing close to 18psi drive pressure to make 14psi manifold pressure.

hopefully I can maintain a ratio like that with the six liter and the billet 7875