Why does reducing resistence in the intake give an increase in power?

[speedsix]

I'm talking about aftermarket TIPs and freer flowing air filters.

If your car is requesting X amount of boost and meeting that, why would decreasing intake resistence give more power? I'm assuming the turbo has to work less hard (spin slower?) to meet the requested boost?

Will this...

A. give reduced charge temps ergo enabling you to run higher levels of boost?

B. give more power at the same level of boost? (why?)



Cheers

Dom

 

[Mitchy]

Its something i dont understand either buddy

I just cant get my head around why an induction kit/uprated panel filter will benefit a turbocharged car?

The air passes through the filter, through the MAF and on down to the turbo where it is spun at 150,000rpm. Any benefit from how well (freely) the air passed through the filter in the 1st place is surely lost here as it changes in volume/pressure and its velocity

The air is obviously heated up having been pressurised by the turbo, then it is passed down to the intercoolers to be cooled before it is fed up into the inlet manifold for combustion.

Surely its the efficiency of the intercoolers that determine the air temperature of the pressurised air coming from the turbo and into the inlet manifold and not the air filter/box/induction kit etc.

However if the air passes in through the filter say 5c cooler, will it come out at the other end 5c cooler, or is the air pressurised to a certain temperature from the turbo that it doesnt matter what temperature the air comes in at? Its how well the intercoolers then cool that air down?

It confuses the sh*te out of me mate I do have a BMC kit but i dont know why and if it is beneficial

I can understand why it is beneficial in N/A terms, but not in turbocharged terms

 

[speedsix]

It's making my brain hurt

Say for example you had 2 cars, one with standard induction, the other with a freer flowing filter and TIP. Both cars request the same levels of boost.

I assume the turbo on the standard car has to work harder to maintain the requested boost but why does that mean the modified car makes more power??

Confuzzled

 

[Saul]

its the same theory behind how altitude effects the running of cars

its the temperature change vs pressure thats important

 

[speedsix]

But if your turbo isn't having trouble making requested boost, what does it matter if it has to work a bit harder?

Like a car at altitude.

 

[DPJ]

Surely what's important is the MASS of air going into the turbo. A poor induction will restrict this mass, a freer induction will let a larger mass in. The MAF measures the mass of air inducted and the ecu fuels accordingly.

(Ie a poor induction is stiffling what the turbo is capable of breathing.)

 

[ibizacupra]

intake pressure ratio.

 

[Tallpaul]

I have an AGU 1.8T (K03 turbo, with REVO) and have repeated logs of each of the following setups:

OE everything and REVO
Green Panel Filter (OE Intake) and REVO
Green Panel Filter (80mm 'Cold Air' Intake) and REVO
Green Panel Filter (80mm 'Cold Air' Intake) and Forge TIP and REVO

I must have done at least 3 4th gear 2000 - 6200ish RPM logs for each setup, all on the same stretch of road.

I never hit more than 146g/s peak flow and when plotted out, the shape of the curve 'g/s v's RPM' is exactly the same for each, they overlay perfectly.

The only conclusion i can reach from that is that the intake side of the turbo is completely unrestrictive to a K03 in the 1.8T. Completly contrary to the claims of loads of Golf owners and a host of VAG tuners.

I'm probably over simplifying, but surely if at no point in the rev range is any more air entering the turbo then no additional power is being produced?

 

[max_torque]

You need to look at the wastegate duty required to meet the boost target.

A more restrictive intake (pre compressor) will result in a lower pressure at the compressor intake. The post compressor pressure will be the same regardless (i.e. that set by the ecu mapping). To make this post compressor pressure the wastegate soleniod will be driven to a duty cycle (i.e. controlling the amount of exhaust gas that bypasses the turbine). The pressure ratio across the compressor will increase as the pre-compressor pressure falls, hence the compressor will be required to do more work, which does 2 things

1) heats up the charge air more - so for the same IC efficiency the plenum air temp will be higher
2) requires more work from the turbine

to meet this greater demand for turbo shaft power the wastegate will be closed more, allowing less exhaust gas to bypass the turbine via the wastegate, and increasing pre turbine pressure. This increase in pre-turbine pressure also has 2 effects:

1) means the piston must work harder to expel the burn gasses into the exhaust manifold on the exhaust stroke, which reduces crankshaft torque

2) reduces the pressure ratio across the engine (plenum pressure is the same as before, exhaust manifold pressure is higher) so actual airflow through the engine will reduce, limiting torque

This is further complicated by the ME engine management actually requesting a target air mass flow, not a plenum pressure, so it will actually have to increase plenum pressure to restore the target airflow, which also causes all the above effects.

This is why the more boost you run the harder and harder it is to make more power, i.e. the 1st 5psi boost increase gets you 20bhp, the next 5psi only 10bhp etc.

Pre compressor pressure losses are a real problem on high boost turbo engines, and most turbo's will loose approx 1.5 - 2 bhp per kPa increase in pre-compressor pressure loss.

(still awake at the back?? lol)

 

[DPJ]

Good explanation. Cheers!

 

[Tabintab]

I'm talking about aftermarket TIPs and freer flowing air filters.

If your car is requesting X amount of boost and meeting that, why would decreasing intake resistence give more power? I'm assuming the turbo has to work less hard (spin slower?) to meet the requested boost?

Will this...

A. give reduced charge temps ergo enabling you to run higher levels of boost?

B. give more power at the same level of boost? (why?)



Cheers

Dom

Seen some great replies, but I thought I should mention another point. With a free flowing air filter your turbo is going to spin up faster & at lower revs i.e. less turbo lag, so more boost and faster.

Tab

 

[max_torque]

Seen some great replies, but I thought I should mention another point. With a free flowing air filter your turbo is going to spin up faster & at lower revs i.e. less turbo lag, so more boost and faster.

Tab

You will find that, unless you have a stupidly restrictive intake, it won't make too much difference to the spool up or boost threshold, as when the turbo isn't spooled up there isn't very much airflow through the system, so there is a low air velocity, so there is low pressure losses, hence the pre compressor pressure is high and the compressor is efficient. You may find that it seems as if it spools up quicker simply because you can hear the turbo whistle much more at lower rpm.

 

[sssstew]

a great technical discussion, thanks all especially max_torque for his explaination. This is the sort of stuff i like reading, no hear say or guesses just facts.