Turbocharger power requirements

[pokeytemplar]

OK I have been researching for months and cannot find anything resembling an answer. Here it goes: I know that turbo's are more efficient than belt driven FI. However, you can closely estimate how much power is lost through the belt and driving the Supercharger. Has anyone seen how much power is lost spinning the turbo(due to increased back pressure)?

The simplest test could be done in three parts:

Test one: Disconnect the tubing from the intake manifold and open the wastegate for the least amount of restriction. Dyno the engine(for someone without a baseline).

Test two: While disconnected from the intake manifold allow normal operation of the wastegate and place a restrictor on the end to simulate the engine load to the turbo (thus creating boost may take more than one attempt to get boost number close to matching). Dyno the engine.

Test three: Hook everything up as normal and dyno the engine.

This one would only test one specific builds losses. I guess the most accurate way would be to place a wastegate in the exhaust of a stock truck and then increase the backpressure loads with each pull to see how much power is lost.

 

[Silverback]

I really do not think you would get what you are looking for.

 

[pokeytemplar]

I really do not think you would get what you are looking for.

Please explain why (if you have the time)?:dontknow:

 

[Coley 1334]

well i do know one thing you will always make way more power with a turbo because they dont have a belt to restrict there rpms

out wit the old in with the new

 

[pokeytemplar]

well i do know one thing you will always make way more power with a turbo because they dont have a belt to restrict there rpms

out wit the old in with the new

Really? A centrifugal is restricted by the rpms (unless you used a cvt). Twin screws produce a lot more boost at low rpms than a turbo. So the twin screw can make more average power than a turbo producing the same peak boost

Yes a turbo is more efficient because it is using wasted exhaust energy. I have read that gives it a 15% advantage. Meaning if the belt driven one required 100HP to build 1500HP on the 10's then the turbo would be using 85HP. I would just like to quantify it.

 

[DevilDawg3097]

The only way to really test the two is to use the same motor with a turbo and then the s/c. Also isnt it a given when they design the s/c, to make up for the hp loss due to adding another pulley in the mix.?

 

[pokeytemplar]

The only way to really test the two is to use the same motor with a turbo and then the s/c. Also isnt it a given when they design the s/c, to make up for the hp loss due to adding another pulley in the mix.?

I am not trying to quantify the losses incurred with a belt driven FI as that has been well documented. I am trying to quantify the losses (at the crank) incurred by a turbo (that has not). This is not a which is better battle but a we know the losses with belt driven FI, what is the losses with a turbo?

 

[DevilDawg3097]

The only real loss you get with a turbo is heat soak. If your intercooler isnt up to par you will loose power or improper setup, ie wrong size turbo inlet outlet etc, this is the stuff you know already. other wise I think you got me confucerated

 

[pokeytemplar]

The only real loss you get with a turbo is heat soak. If your intercooler isnt up to par you will loose power or improper setup, ie wrong size turbo inlet outlet etc, this is the stuff you know already. other wise I think you got me confucerated

The losses associated with a turbo due to the increased back pressure. The back pressure is what drives the turbine but also reduces the efficiency of the engine. I am wondering by how much. For example. Looking at Dom's build he is producing 1365HP to the wheels. The assumption would be he is producing 15% or more at the crank due to driveline losses (1570HP). How much more power is lost from the increased back pressure? Another 15%?

 

[DevilDawg3097]

I can check into it tommorow if you want, ask our turbo guy we use if you like? I would only be taking a guess at that.

 

[pokeytemplar]

I can check into it tommorow if you want, ask our turbo guy we use if you like? I would only be taking a guess at that.

Yes I would really appreciate it. Don't like the "it's just better" answer I always hear. Gives me flashbacks to when I was a kid ("because I said so"). Can't learn anything that way. I want to know the reasons why it is better (and worse). I understand the benefits of using wasted energy but nothing is free there is a "cost" associated with it (other than money ). I just want to know how much it costs..........

 

[viperhauler]

i'm intrigued by your question, pokey...

except i've drunk too much to explain it clearly...

although, i do know, your theory about the other 15% basically cancels out the drivetrain loss...the part of his particular turbo system is inclusive in that same 15%...

i think...

 

[pokeytemplar]

i'm intrigued by your question, pokey...

except i've drunk too much to explain it clearly...

although, i do know, your theory about the other 15% basically cancels out the drivetrain loss...the part of his particular turbo system is inclusive in that same 15%...

i think...

Thank you,

I look forward to your sober explanation!:rock:

 

[viperhauler]

might have to remind me...:rock:

 

[yellowfever#154]

I read somewhere that turbos take about .1% of the engine's total horsepower to turn for every 1psi of drive pressure. So at 10psi, that would mean 1% of the engine's total horsepower would be used to drive the turbo, 30psi 3%....and so forth.

1500HP = 37 HP loss driving the turbo if 25 lbs of boost is used

Probably lots of variables to get exact numbers, but like everyone says "Turbos are much more efficient than a supercharger". Your comment earlier about a supercharger vs a turbo with the same peak HP, that a supercharger gives a better average is true due to spool time. But who builds a turbo motor to run the 600hp the Roes are capable of? Us doing it are after 1000+.

 

[yellowfever#154]

Really? A centrifugal is restricted by the rpms (unless you used a cvt). Twin screws produce a lot more boost at low rpms than a turbo. So the twin screw can make more average power than a turbo producing the same peak boost

Yes a turbo is more efficient because it is using wasted exhaust energy. I have read that gives it a 15% advantage. Meaning if the belt driven one required 100HP to build 1500HP on the 10's then the turbo would be using 85HP. I would just like to quantify it.

How does a CVT make a centrifugal supercharger more efficient?

 

[Smokey]

How does a CVT make a centrifugal supercharger more efficient?

a variable rpm blower? isnt that a belt driven turbo:dontknow:

 

[Silverback]

The losses associated with a turbo due to the increased back pressure. The back pressure is what drives the turbine but also reduces the efficiency of the engine. I am wondering by how much. For example. Looking at Dom's build he is producing 1365HP to the wheels. The assumption would be he is producing 15% or more at the crank due to driveline losses (1570HP). How much more power is lost from the increased back pressure? Another 15%?

Back pressure does not drive a turbo. It's the expanding gases or energy that drives them.

 

[pokeytemplar]

a variable rpm blower? isnt that a belt driven turbo:dontknow:

CVT is a constant velocity transmission. Normally they are rpm based but can be electronically controlled. Infinitely variable ratio within its design parameters. Thus at 1000 engine rpm it could at a 6:1 ratio and at 6000rpm it could be a 3:1 ratio (or anywhere in between) thus keeping the centrifugal's turbine speed high.

 

[pokeytemplar]

Back pressure does not drive a turbo. It's the expanding gases or energy that drives them.

You are correct Silverback. I mean that Back Pressure is the negative byproduct of driving the turbo. Much like belt in-efficiencies affect the crank output in other FI solutions.