Racing with no air filter

All that has to do with the power train, gearbox, clutch, fuels and lubricants, etc. Generally the mechanical side of Formula One.
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JordanMugen
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Joined: 17 Oct 2018, 13:36

Racing with no air filter

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Watching the Monaco Grand Prix de Historique, I notice many of the cars running either with no air filters at all, or only mesh air filters. Perhaps, this is because that is how they were raced in period or perhaps it's the current owner's preference. What are the pros and cons of running a racing engine with no air filter? :)

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It also seemed popular to design some vehicles without ram air intakes, even as late as the Williams FW07. What was the advantage of that? Did the additional drag of the air intake duct outweigh the additional power the DFV engine could produce with it?

Or were the potential gains from optimising ground effects so much greater than the potential for a couple of extra engine horsepower from the trusty old DFV, that it wasn't worth Mr. Dernie's time to design an engine air intake (as the only person running the wind tunnel and designing all the aero bits)? Especially since with the data logging equipment at the time (or the lack thereof), there was little way to quantity the effect of different air intakes on engine power while on track?

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I notice some tuner street cars, like the Keiichi Tsuchiya Toyota AE86, also prefer the no air filter configuration:
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Would an errant stone entering the air intake be potentially problematic to either a street or racing engine, or would it be of no consequence? :)

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Stu
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Joined: 02 Nov 2019, 10:05
Location: Norfolk, UK

Re: Racing with no air filter

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JordanMugen wrote:
25 Apr 2021, 19:35
Watching the Monaco Grand Prix de Historique, I notice many of the cars running either with no air filters at all, or only mesh air filters. Perhaps, this is because that is how they were raced in period or perhaps it's the current owner's preference. What are the pros and cons of running a racing engine with no air filter? :)

https://i.imgur.com/FtC1tEP.jpg
https://i.imgur.com/OrwkkuY.jpg

It also seemed popular to design some vehicles without ram air intakes, even as late as the Williams FW07. What was the advantage of that? Did the additional drag of the air intake duct outweigh the additional power the DFV engine could produce with it?

Or were the potential gains from optimising ground effects so much greater than the potential for a couple of extra engine horsepower from the trusty old DFV, that it wasn't worth Mr. Dernie's time to design an engine air intake (as the only person running the wind tunnel and designing all the aero bits)? Especially since with the data logging equipment at the time (or the lack thereof), there was little way to quantity the effect of different air intakes on engine power while on track?

https://i.ytimg.com/vi/fQdCZarnl4g/maxresdefault.jpg

I notice some tuner street cars, like the Keiichi Tsuchiya Toyota AE86, also prefer the no air filter configuration:
https://www.drifted.com/wp-content/uplo ... ne-bay.jpg

Would an errant stone entering the air intake be potentially problematic to either a street or racing engine, or would it be of no consequence? :)
Just dust (which on a racetrack is likely to be combination of regular dust, brake and clutch dust, exhaust particles, etc, etc), will kill an engine in half the time (at least) as compared with using a good air filter.
Perspective - Understanding that sometimes the truths we cling to depend greatly on our own point of view.

wesley123
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Joined: 23 Feb 2008, 17:55

Re: Racing with no air filter

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I think that the main reason is the technology of the time, a lot of things that are common knowledge and/or well understood these days were either non-existant or not properly understood at that time.

I can imagine that when restoring a car, you'd want to keep it as true to its original as possible. If there suddenly is a modern air filter present that would either look weird and/or take a small chunk out of the cars worth.

What Stu names is an issue that is very much present. But how much of an issue is it really for a car that barely ever actually runs? Due to the cars status they'll most likely be serviced after events as well.

Although great for engine life and all, an air filter in the way would provide some sort of blockage for the air, which might be undesirable. If it's the case that you frequently rebuild the engine(or put in a new one) the gains would probably outweigh the disadvantages.
"Bite my shiny metal ass" - Bender

Tommy Cookers
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Joined: 17 Feb 2012, 16:55

Re: Racing with no air filter

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JordanMugen wrote:
25 Apr 2021, 19:35
....vehicles without ram air intakes, even as late as the Williams FW07.
ram air intake heights were earlier reduced by rule and further rules eventually banned ramming (mandating open exits)

Greg Locock
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Joined: 30 Jun 2012, 00:48

Re: Racing with no air filter

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The gain in power from removing the air filter is tiny, of the order of 0.5% from memory. The loss of power from not having a sensibly placed cool air intake can be 10% or so.

gruntguru
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Joined: 21 Feb 2009, 07:43

Re: Racing with no air filter

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The "errant stone" or small metal object will destroy the engine in seconds.
je suis charlie

Hoffman900
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Joined: 13 Oct 2019, 03:02

Re: Racing with no air filter

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gruntguru wrote:
27 Apr 2021, 06:20
The "errant stone" or small metal object will destroy the engine in seconds.
Rubber as well.

You even see it on the spark plugs. It’s what you think is metal from detonation only to realize it’s just melted / carbonized rubber.

Air filters done correctly result in zero power loss. Not running them in these applications is totally aesthetics. Other than the large particles, sucking in grit and dust will dirty up the oil quickly, and wear valve seats and pistons fast. Even with air filter technology, desert and dirt track builders still deal with dust damage.

Back in the day, you would see steel mesh over the butterflies to keep large chunks of stuff out (and over the throttle linkage). I know of one amateur racer who had a chunk of rubber cause the throttle to be stuck open!

UghThatMemeGuy
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Joined: 05 Dec 2022, 23:26

Re: Racing with no air filter

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I was looking for an answer on why it is that there are often times no air filters on racing engines. Someone correct me if i am wrong, but in NASCAR, aren’t the cars (and engines?) disassembled after each race to validate no cheating has occurred?

That said, for F1, if the teams get 3 engines to use per season and the primary engine of those three is supposed to be used all season where possible, then it would suffoce to say that at an average of about 100 min per race, w/ 7 races per season, that the engine needs to last 700 min or about 11.6hrs. Let’s say the avg speed is 161 mph and the engine puts on a total of about 1,878 miles per season. For grins, I would double or triple that mileage for practice sessions and qualifying etc. That said, if the oil is changed after every single use, then essentially, the engine only has to last for roughly 6,000 miles making an air filter of fairly little concerned… Yes there will be where on the engine and it won’t last as long, but aren’t they likely to rebuild the engine, Hon, bore, etc. after every season to prep for the following season?

If you get into NHRA they tear engines down after each race… So it seems relatively fruitless to worry about air filtration when tear downs and oil changes are so frequent... *shrug*

Thoughts?

gruntguru
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Joined: 21 Feb 2009, 07:43

Re: Racing with no air filter

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- there is potentially a small power loss when an air filter is added
- the small air restriction of an air cleaner is inconsequential on a turbo engine
- packaging can be very difficult, bulky and expensive where the engine has ITBs and multiple ram tubes
- accelerated wear is unacceptable on precision race engines - even those with a short life between overhauls
je suis charlie

Hoffman900
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Joined: 13 Oct 2019, 03:02

Re: Racing with no air filter

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UghThatMemeGuy wrote:
05 Dec 2022, 23:38
I was looking for an answer on why it is that there are often times no air filters on racing engines. Someone correct me if i am wrong, but in NASCAR, aren’t the cars (and engines?) disassembled after each race to validate no cheating has occurred?

That said, for F1, if the teams get 3 engines to use per season and the primary engine of those three is supposed to be used all season where possible, then it would suffoce to say that at an average of about 100 min per race, w/ 7 races per season, that the engine needs to last 700 min or about 11.6hrs. Let’s say the avg speed is 161 mph and the engine puts on a total of about 1,878 miles per season. For grins, I would double or triple that mileage for practice sessions and qualifying etc. That said, if the oil is changed after every single use, then essentially, the engine only has to last for roughly 6,000 miles making an air filter of fairly little concerned… Yes there will be where on the engine and it won’t last as long, but aren’t they likely to rebuild the engine, Hon, bore, etc. after every season to prep for the following season?

If you get into NHRA they tear engines down after each race… So it seems relatively fruitless to worry about air filtration when tear downs and oil changes are so frequent... *shrug*

Thoughts?
NASCAR engines use air filters. The engines have to last one race weekend, so figure 700-800 miles. They're torn down after each weekend and rebuilt. Hard parts are re-used; crank, heads, block, etc. Other stuff checked for wear (camshafts), but springs / rings, etc. are one and done. The blocks go about 8000-9000 miles between cycling out. Heads would be less. One thing to keep in mind, and part of rebuilding / swapping engines out every race, is to set the engines up for different track types, you're going to have different porting / camshafts / exhaust headers, etc. It's not exactly like taking an engine like a F1 engine where you have MORE than enough air and you can just tune it via other means (variable geometry turbo inlets, wastegate, MGU-H, MGU-K, variable length intake runners, etc.). You have plenty of tools at your disposable to shape the torque curve. On a naturally aspirated engine, you literally have to change parts out.

The Ilmor LS prodution based ARCA engines go about 1800 miles between rebuilds. The LS based IMSA engines go about 3000-3500 miles between rebuilds. RPM is a big factor. I know Ilmor has tested some of these LS based platforms to 10,000 miles on the test cells, but there is a tradeoff in power.

The DTM engines run about 3000 miles before rebuilds.

Again, everything has a cycle life and when you are pushing the limits of the rules in terms of tolerances, weight, tune, etc. You run it right up to your margin of safety. What might be junk to a NASCAR builder will be just fine on your average hot street or even drag strip engine. They just don't feel comfortable with it going another 700 miles at those rpm at those temperatures. There are a lot of wasted costs to a DNF.

saviour stivala
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Joined: 25 Apr 2018, 12:54

Re: Racing with no air filter

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All formula one power unites uses an intake air filter.

Jolle
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Joined: 29 Jan 2014, 22:58
Location: Dordrecht

Re: Racing with no air filter

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The lifespan between rebuilds is so short for those old engines, that a bit of extra wear due to dust or small debris is neglect-able compared to the gain of a free sucking engine. Now that PU’s have to be as durable as road engines, plus smaller tolerances (so smaller dust dies greater damage), air filters are used.

As for the ram intakes. If you calculate the amount of air sucked into an engine vs the size of the opening and speed of the car, the intake is almost at atmospheric pressure until you really really open up the scoop… so they banned big intakes halfway through the 1976 season.

But for why not… good chance that the gain of that, needs to be calculated in advanced due to the simple control electrics of the time. So good chance it was more a miss then a hit.

saviour stivala
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Joined: 25 Apr 2018, 12:54

Re: Racing with no air filter

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Advancements in intake air filtration design has rendered performance losses due to air intake filtration as 'virtually non-existent today. not only that but in some cassis air filtration can actually deliver added power.

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