What is your turbine inlet pressure (TIP)?

[drag-200stang]

What is your TIP? Don't know? How can you tune a turbo car and not know? It's like not dialing in your new cam shaft. You can't guess and hope it will be alright.

For your turbo to run right you need to know your:
boost pressure
air-fuel ratio is under boost
timing under boost
turbine inlet pressure
it wouldn't hurt to know your exhaust gas temperature either

Turbine inlet pressure is the pressure measured before the turbine. It can be measured by drilling and tapping an 1/8" NPT and using a common fuel pressure gage with a metal line. Use the longest line to dampen pulsations. It only needs to be checked if you make a change to your turbo system. Remove it after checking.

I can see I'm not explaining this very clearly but simply, the closer TIP is to boost pressure, the more efficient your turbo will run (more power, cooler running). Generally more than 2:1 turbine over boost pressure is not good. Of course a quicker spool is going to cause a higher TIP. Higher TIP is going to cause higher cruisin fuel consumption due to the engine fighting itself.

As with everything there are compromises. But if you're cruisin at 70 mph, 3 lbs boost and you've got 20 lbs turbine pressure - you have a problem.

I don't have the exact numbers but let's check and see where we're at and what changes help the performance.

Maybe some of you guys can elaborate more eloquently than I have.

 

[Bort62]

Just to clarify, you mean exhaust pressure ?

It would seem to me that a high ratio of TIP to manifold pressure would indicate the the turbine was acting as a significant restriction. This would be indicative of a turbine mismatch, IE turbine section is too small for the engine.

Am I on the right page ?

 

[drag-200stang]

Yes, with some clarification (I hope). TIP would be measured before the turbine (in the region you'd put the waste gate). Unless I'm not thinking right, any restriction of the turbine housing AR, turbine wheel size, down pipe, mufflers, and exhaust tips would still add up and be measured as a total at that location.

I guess I would think of exhaust pressure, as being TOP - turbine outlet pressure - after the turbine, and now that I think of it, it wouldn't hurt to measure that either. TOP would be the restriction downstream of the turbo (down pipe, mufflers, etc.) and TIP would be the total restriction.

TOP really kills spool up. No back pressure is good for a turbo.

 

[Bort62]

Well, I don't have a lot of specific knowledge about turbo's, this application is all relatively new to me.

But I do know a little about fluid dynamics, and that's all an engine is anyway.

The reason that back pressure, or TOP, is bad for spool up, is because it decreases the deltaP across the turbine. The power with which the turbo spins is a factor of pressure drop across the turbine as well as volumetric flow rate. Flow rate is directly coupled to engine HP, so that's not something you can adjust directly. Pressure drop, however, is the sum of the TIP and TOP. You can lower TOP by removing restrictions after the turbine (muffler, bends, small exhaust pipe, etc).

Now, if you had some way to increase TIP (without reducing flow rate ) you could actually increase spool up... but you don't (well, not without doing weird stuff like injecting water into the exhaust)

Now, stepping into the engine - since it's just a piston pump, it behaves the same way. "Backpressure" or, in the case of a turbocharged system, TIP, reduces the pressure drop across the engine. As a result, it means that it takes more power to evacuate the cylinder. This robs power from your engine... so these two things are sorta at odds. You want a high TIP in order to spin your turbo better, but you want a low TIP to reduce pumping losses from the engine.

So, like everything, it's a balance.

I'm not sure if that makes any sense. I don't have the time right now to really re-read and try to make things more clear.

 

[wallaka]

you could actually increase spool up... but you don't (well, not without doing weird stuff like injecting gasoline into the exhaust)

You've just described anti-lag devices, my friend. Works extremely well, kind of hard on compressor blades, though.

 

[Anonymous]

You've just described anti-lag devices, my friend. Works extremely well, kind of hard on compressor blades, though.

Actually, it gets the turbine blades hot enough to do damage if allowed to

 

[wallaka]

You've just described anti-lag devices, my friend. Works extremely well, kind of hard on compressor blades, though.

Actually, it gets the turbine blades hot enough to do damage if allowed to