scoobyster

Hi All

I'm doing an engineering management project at uni where I have to compare given products on the market, work out customer enthusiasm models, reverse costings, etc. I need to describe how I would design my own product to better meet customer's requirements.

I think air filters for Scoobs would be a good one for this, especially given the sensitive MAF issues, and so little concrete evidence of which product is the best. Also it was a good excuse to buy a Green panel filter for my GL .

Does anyone (particularly those that have been rolling road-ing) have an idea of which products give what gains of power and torque? I'm interested for both N/A and Turbos. I've specifically written about the most popular choices that I know of - Green, Pipercross, K&N, HKS, Blitz, etc. Any info would be most welcome though. Particularly on the STi panel as I'm unsure on how that is constructed, I believe it's paper like an OE, but how is it 'better' than OE, and why did it appear to give a loss in Scoobymag's WRX when people seem to rave about it on here?

Just guesstimates will do, if you could say what power gains you've had from your own induction kit or panel filter I'd very much appreciate it. Please state what MY and engine you have, the chosen filtering method and the gains in power you think/know it have given over an OE paper filter.

I only put my own Green panel in last night and haven't reset the ECU yet. I went for a quick blast and it certainly feels torquier, maybe quicker but it could just be a placebo. I need a few good blasts out of 30s into NSL zones to decide properly.

Any info you could give would be much appreciated guys. There may be a 'what do you look for in an air filter' type survey popping up soon too .

Many thanks in advance.

Ben

Brun

You feel more torque out of a GL with a green panel?

TonyBurns

iTrader: (3)

I can give you the STi panel filter gains

Car:- MY03 WRX STi JDM Twin Scroll VF36 turbo (new)
Miles:- approx 2k
2 runs before on the rolling road, giving the result of:-

288bhp, 297lbs of torque.

STi panel filter fitted whilst car on the rolling road

2 runs after:-

299bhp 312lbs of torque.

Car with more miles on now has quite a few BHP and lbs of torque more than the above

Tony

PS, please note that the STi panel filter was designed for the JDM STi and has the best gains on this car.

scoobyster

Brun, as I say I only swapped it yesterday, but I think I feel more shove, which is how I would describe the feeling of torque, yes. The last ImprezaSport.net rolling road showed huge gains for those with aftermarket air filters, the N/As really seem to benefit from it, suprisingly.

Many thanks Tony, bet you were pleased with that gain. How can a filter be designed for a specific car though? At the end of the day an STi is sucking air through it the same as (albeit somewhat more than) a WRX or N/A would, surely?

Cheers

TonyBurns

iTrader: (3)

The filter was designed specifically for the JDM STi for Hologlomation(sp) purposes, its gains are seen greatest on the STi due to the standard car having a very restrictive paper filter, the gains i saw were around 4-5% which were quite good
Also unlike the UK who have Prodrive to tune the UK STi, the JDM cars have less tuning parts for them (BHP wise) with the panel filter being the most advantagious.
Previous to the STi panel filter the car felt restrictive above 6k rpm (8k redline) after the car flew up there no problem
Slightly noisier (but not by much) is about the only down side to adding one.

Tony

harvey

iTrader: (48)

Butty

iTrader: (2)

I'll be able to give a comparision of sorts next week at PE for an STi filter on a WRX PPP
The car was run as std in May at PE - the variables will mainly be inlet temp changes and mileage as I'd done about 10,000 back then.

dyno.scoobynet.co.uk will also give some info on power runs where various air filters were tried.

chrisp

You might want to buy the 1st edition of the new scooby magazine, some surprising results

TonyBurns

iTrader: (3)

Harvey,
I should have said accessories, JDM wise the only performance accessory that subaru japan do that has any major gains is the panel filter, the only other anything is the GeNome b/box.

Tony

scoobyster

All these views and only one reply with figures!

Cheers Butty I'll look forward to seeing your results. Thanks for the dyno link, I'd forgotten they were there. Not many have a comparisson where the same car has just had the filter changed, those that do often show a loss at the fly and gain at the wheels though, I'm confused now!

Chrisp, I do have Scoobymag, the results were part of the reason I decided on this for a project. I'm interested in why Tony's STi can pull more air through an STi filter than an OE, and a WRX less than an OE.

About the N/As by the way, over on ImprezaSport there's a 2.0 phase 1 (book is 115bhp) with just a Pipercross panel filter and Magnecor leads as performance mods, it made 126.5bhp and 118lb/ft. There's also a guy with 129.5bhp and 123lb/ft from a Pipercross Induction Kit, but has aftermarket backbox and 2nd decat.

Any other figures would be appreciated folks, just estimates are fine but please say that's what they are.

Thanks,

Ben

scoobyster

Could it be that an STi filter has to be really worked hard (ie. have a ~300bhp engine sucking through it) to really start performing properly? If that were the case surely and STi would have very peaky performance; was your power curve moved up proportionally Tony or is it mainly the peaks that are improved?

Brian the Sn@il

Would the WR1 have the STI panel filter fitted ?

TonyBurns

iTrader: (3)

Its actually a very smooth power curve, the performance isnt at all peaky, you have greater gains at higher RPM, so really its only as if the curve has moved rather than peaked.

Brian,
The WR1 runs a paper filter, you may find little or no gains in the STi panel filter due to the PPP (along with most PPP'd cars they have been designed to run the optimum with the given items, change could reduce performance believe it or not )

The STi panel filter is best used on unmodified cars or mapped in for its best performance

Tony

scoobyster

Thanks Tony, very useful info.

Any one else have anything to add? Would be appreciated.

johnfelstead

The main benefit of the STi panel filter is its higher airflow capacity. Going from a paper element to the STi filter doesnt show anything worth talking about until you get to 6000rpm, at which point the stock filter starts to strangle the engine (on a 276BHP spec engine), the STi filter lets it breath freely upto the 8100rpm limiter.

It's been shown to work well upto 350BHP/Lbft in the stock airbox. Another important benefit, especially on MY99/00 year cars, is the filter is dry, so you dont have problems of contaminated MAF sensors, which you can get with oiled filters on this model year of Impreza.

scoobymoo

I've got an STI filter in my P1 and it definately spools up quicker and pulls harder towards the redline than it did before (ITG filter). However I also had a new maf and ecu reset at the same time which may have improved things as well?

AndyC_772

iTrader: (2)

I can't help but observe that the only controlled experiment that's been done with any of these filters is the Scooby mag one - the conclusion from which really is that neither of the alternatives they tested makes a whole lot of difference one way or ther other.

Does anyone (as well as Tony) have any scientific evidence to the contrary?

cookwibble

on my 98 sport the pipercross induction kit seems to have had a small efect. throttle response is better and it pulls better in lower revs. not anythin hugely noticable though

harvey

iTrader: (48)

I spent quite a lot of time and money trying to find the most efficient panel filter using a rolling road but came to the conclusion that the performance differences were relatively small in relation to other variables efecting reliable readings. I gave it up as a well intentioned piece of investigation that did not give tangible results.
I settled on a K+N panel filter as it gave good filtration from what I could find out, it was reusable, cost effective and possibly one of the better performers.

DoMJoLLy

I maybe asking a silly question, but is it worth changing my filter in a wrx 01 PPP?

MikeWood

In our testing, changing air filter on a turbo Impreza makes an almost unmeasureable difference and any gain is probably down to the airflow over the sensor being slightly different. Changing to an induction kit normally loses you power as the air entering ther filter is normally warmer than std unless the filter itself is outside the engine bay.

On a normally aspirated engine there is no way that the filter is providing a restriction as on some cars it's the same filter as a 280ps turbo! Before anyone states that they have seen 125bhp or whatever from a phase 1 115ps Sport, we dyno tested a Forester which is standard other than a different silencer and it had over 140bhp at PE.

Mike

Butty

iTrader: (2)

Well the STi filter didn't do a lot of favours for me at PE today.

Test in May on an MY04 WRX PPP showed 182 bhp @ wheels which worked out as 265 bhp @ 5940 and 263 lbft @ 3667. Inlet temp was 21 deg C. Mileage 10,000

Today with just the STi filter added I again got 182 bhp @ wheels but this was now worked out at 256 bhp @ 5973 and 256 lbft @ 3784. Inlet temp 16 deg C. Mileage 16,400.

So no sign that the "fabled" STi filter does anything of note when simply swapped with the OEM one.

I'm curious as to why I can get the same power at wheels at the same RR but its calculated to be a different power at the flywheel - can anyone explain?

Nick

AndyC_772

iTrader: (2)

Different transmission losses. Maybe this time your gearbox oil is a bit warmer and less viscous, or the transmission has loosened up a bit. Either way, comparing RR figures from one day to the next is pretty meaningless, you're talking about just 9bhp out of 260 odd, which is just 3.5%. That's remarkably consistent just from one test to another, and all it's telling you about the filter is that it doesn't obviously make a lot of difference either way.