Just looking at the Isspro Performax gauges and i came across the drive pressure gauge. What exactly does this measure and when would it be useful??

 

Probably not the best description, but drive pressure can roughly be described as the resistance to exhaust flow or back pressure. It is the force of the exhaust gasses exerting against the turbine wheel in the turbocharger. As the exhaust gasses turn the turbine, the compressor wheel turns and compresses air that you read as boost... as this boost goes up, it is increasingly harder to turn the tubine and creates the back pressure or Drive Pressure.

It is valuable in higher HP engines to measure this to find when a turbo is outside its MAP or efficiency range. Mostly, when turbos are operating properly there is a 1:1 ratio of boost to drive pressure. When a turbo is outside the map, DP goes way up in relation to the boost provided. Too much DP can pop a head gasket.

 

that makes sense, thanks!

 

so how the opie kit helps keep you from lifting the head or just the freexe plugs. i know its taped into the water system but how does that stop dp or does it not?

 

No, Opies kit does not have anything to do with DP. It helps cool between 5&6
and relieve the pressure there to prevent the blowing out of the freeze plugs.

 

BINGO!!!!!!!!!!!

 

In simple terms:

Drive Pressure = Exhaust Pressure

 

I see the answer has pretty much been given but i enjoyed the ease of reading the newest issue of Diesel Power. They explained every part of a diesel and how it works. Im pretty sure drive pressure was in there. So go pick an issue up

 

Darn soulzoo, who stole your user name and posted this rubbish. I know you know better than that!


A turbo's map has little to do with DP, it can be higher or lower when the compressor is in or out of its map. DP is a function of the hot side housing and size not the compressor. A large turbine turbo can be out of its efficieny map and still have relatively small DP in relation to boost.

Oh, one other thing, I really don't think a HG that is capable of containing 1500-2000 psi of cylinder combustion pressure is gonna be bothered by 60, 70, even 80 psi of drive pressure. Considering DP is not ever working directly on any part of the HG it simply amazes me people think it can effect it. Popping an HG is heat or combustion pressure not boost or DP.

 

The ratio of drive pressure to boost is however, important.

 

What your missing is not the drive pressure but the actions it creates.
Excessive drive pressure ( TIP = turbine inlet pressure) creates timing and the timing is what lifts the head.
So in a nut shell excessive TIP (DP) will wipe out a head gasket.

 

Creates timing???

Timing lifts the head????


Not sure what you are trying to say here but there is no timing involved in boost and drive pressure. Cylinder pressure causes HG failure, generally from too much air and fuel and/or the generated heat in-cylinder.

Once the compressor is out of its efficiency range boost curve starts falling while DP can go higher due to restrictions but that pressure is out of the cylinder and any backflow will actually drop cylinder pressures. One can pop an HG on 1st gen and I guarantee DP is not an issues there.

Looking at boost and DP is too simplistic as rpm's, fueling, and inj timing play major roles. Just saying DP will cause HG failure is way too broad and misleading.

 

Advanced timing raises cylinder pressure.

 

What I said was TIP causes timing that pops the gasket!

Turbine inlet pressure once over 1-1 ratio will create timing, and yes timing will lift a head gasket.
Each cycle with a excessively high TIP causes a incomplete scavenging of the cyl, next stroke you pour same fuel but less air in (already some left over hot air in there) and this preheats the mix and that cyl now fires sooner. Read timing.
This action compounds over cycles creating excessive EGTs and more TIP and will result in lifting the head.

Hope your not so confused now.

 

Reduced O2 from an incomplete exhaust cycle (due to high back pressure) may increase cylinder heat but will reduce peak cylinder pressure due to incomplete burn of the fuel charge. More fuel does not always mean more pressure.