Hi Guys

Will a K&N filter increase my BHP and improve fuel or just increase BHP and drink more?

No. Won't increase anything.

It will increase power, but only by 1 or 2 bhp, and most people can't feel that. What you might feel is the car being a touch more lively, particularly if you want to rev it in neutral.

Probably the worst value for money power upgrade for an untuned diesel.

Nobody would notice 1-2bhp difference an that's if you gain that much. More performance gains to be had by skipping lunch.

Look up ALH engine tuning, or golf tdi110 or tdi90 tuning. Theres LOTS of information out there. In fact there is actually too much.

It will increase power, but only by 1 or 2 bhp, and most people can't feel that. What you might feel is the car being a touch more lively, particularly if you want to rev it in neutral.

How will it do that? Diesels aren't air-throttled.

Thats the first video I've seen where they have done a back to back dyno with any different type of air filter on a TDI. The fact they did it with no air filter really goes to show how good the stock system is, Question is would it have made any difference to the remapped engine?

Thats the first video I've seen where they have done a back to back dyno with any different type of air filter on a TDI. The fact they did it with no air filter really goes to show how good the stock system is, Question is would it have made any difference to the remapped engine?

I'd liked to have seen one without the airbox (open MAF) to see if there's any restriction in the filter housing and snorkel feed

How will it do that? Diesels aren't air-throttled.

You get a pressure drop through the filter, which means you have a lower mass air flow into the turbo, hence a lower one from these to the combusiton chamber, which as a result is less filled. This gives you a lower min pressure at the end of the power stroke, and hence less air to spin the turbo, giving lower boost pressure. Lower boost means that the EMS will fuel the engine less.

Oh and if you think diesels are completely fuel-throttled, take a TDI and open a boost pipe connection, then watch it smoke!

You get a pressure drop through the filter, which means you have a lower mass air flow into the turbo, hence a lower one from these to the combusiton chamber, which as a result is less filled. This gives you a lower min pressure at the end of the power stroke, and hence less air to spin the turbo, giving lower boost pressure. Lower boost means that the EMS will fuel the engine less.

There is a pressure drop through all filters. The difference in pressure between the stock filter and a poorly filtering K$N will need a very sensitive manometer to measure. We're talking total pressure drops which are less than a percent of atmospheric pressure. The difference between filters is less than that again.

The difference in pressure and hence density change beyond the filter is not big enough to affect the airflow through the engine in any way that can be felt.

To get 1-2hp difference, you would have to reduce pumping losses by 1-2hp. Power = pressure * flow. Tell me how much pressure difference you need for 110hp diesel at full song?

Oh and if you think diesels are completely fuel-throttled, take a TDI and open a boost pipe connection, then watch it smoke!

I know you understand engines better than that. So why make such a strange comment?

Diesels are completely fuel throttled. But electronic diesels limit fuelling bases on several constraints. Here are the main three.

First, torque request from the throttle pedal.

Second, torque limiters in the ECU.

Third, air-fuel calibration tables in the ECU.

It is the third that relies on air-flow, but only if fuelling isn't already limited by those first two. In all my diesels (3 currently) the air/fuel mix is not the current limiter on power. Which means introducing a few % more or less air does not have any effect on fuelling or power.

Diesels run significant amounts of excess air in combustion. Around 50% more than stoichiometric (A/F ~22:1 stock). You can pull down to about 17:1 before smoke becomes a problem.

Your above comment out opening a boost pipe connection means the engine is dumping air which the ECU has measured and is assuming to go through the cylinders. It's not relevant to air-filter discussion, nor does it show that diesels aren't fuel throttled. Because they are fuel throttled.

i once put an induction kit on a diesel and whilst the BHP gain is negligable and it drank moree fuel it made the car feel more free and more driveable but as a whole conclusion i find that with pro vs con this will leave you about exactly where you were to start with . . . much like this post

...There is a pressure drop through all filters. The difference in pressure between the stock filter and a poorly filtering K$N will need a very sensitive manometer to measure. We're talking total pressure drops which are less than a percent of atmospheric pressure. The difference between filters is less than that again...

+1

And it's a closed loop system where one of the inputs is measured air MASS flow after the filter.

Thanks guys after reading all your comments i just stuck in a standard air filter.

Remove your snorkel and replace it with a larger pipe that gives you a decent cold air feed. That'll give you more bang for your buck than an air filter.

OEM Paper filters are good for up to 200HP, which without serious modifications (read crank, pistons, rods, etc) you'll never get.

any pictures or links for the large pipe?