Rob Day

iTrader: (78)

Im unsure of the current filter so im going to replace it but dont know which to go for

2001 UK300 PPP WRX

I was thinking of doing the snokus removal and opting for the Cold AIr kit, but im unsure if this is worth while for my mods:

Sti Pink Injectors (cleaned and flow tested) NOW FITTED
VF30 (Brand New) NOW FITTED
Sti Turbo Up pipe (Brand New) NOW FITTED
3" full decat Stainless (Brand New) CURRENTLY FITTING
Sti TMIC (2nd hand, refurb) TO FIT
Walbro 255 fuel pump (New From Lateral) AWAITING DELIVERY
Panel filter - YET TO RESEARCH AND PURCHASE

Id appreciate some feedback and your expirences please.

Thanks Rob

zs_phil

iTrader: (1)

green cotton

Splitpin

Don't bother removing the resonator, you won't gain anything worth having and lose a little accuracy in the mass airflow measurement.

Panel filter - Green is fine, so is K&N. Lightly dab some tissue over both to remove any excess oil prior to fitting.

harvey

iTrader: (48)

Changing from the O/E Subaru cardboard to an aftermarket will not create any more power.
I tested four filters on two separate occassions because I did not believe the results but they were the same on each occassion. Four pannel filters were all within less than a 2 bhp range. The HKS foam filter was "best" but let through dirt the size of large sand grains. The K+N and O/E were the same and filtration was good. The STi had least power by 1.7 bhp but had best filtration qualities.
If it is a car that will be kept, my choice would be a K+N but only because it is reusable otherwise O/E is good and cheap.

As Splitpin says, snorkle removal is a bad idea. My tests without adding any link pipe to substitute for the snorkle removal and without remapping showed a loss of 8 bhp, probably because of an adverse effect on the MAF Sensor. The power was restored when the snorkle was refitted.

Rob Day

iTrader: (78)

Cheers Harvey, Good write up.

I think the Snorkle/Snokus removal/delete is a conflict of interest. I have read many reports saying that this is the way forward, and many more saying dont do it...

Here is a thread i was reading on another Subaru members site, this is NOT my words or experience:

I did the air intake silencer removal, and used 90 degree and a 45 degree 3" PVC street bends (one of each) to pull air out of the lower fender. (There is a post here some where that talks about this, I just can't find it).

Along the way I borrowed some temperature probes from my office and collected some data on intake air temps.

Here are my conclusions, below is the data:
1)You cant do much better for intake air temp then the factory set up, it just works really well.
2)Any intake the draws air from the engine compartment, even the front edge is likely to make the situation worse not better.
3) The Snorkus removal makes the throttle a bit more responsive, and gives a good sound (but not so loud you can hear it over a loud radio). Also the Snorkus removal and air intake from the fender doesn't impact air intake temps in any noticeable way.


In the Stock 2004 WRX Wagon I measured a 2 degree rise of temp in the air on the engine side of the air filter above ambient air (measured on the front edge of the hood scoop, this probe was checked against one hanging out the window, and seemed to accurately reflect ambient air while the car was moving).

With the Snorkus out, and drawing air from the fender, with the factory RAM intake still in place, just blowing into the fender I saw about 4 degrees rise above ambient in the air box.

With the Snorkus and the factory RAM intake pulled out I saw about 2 degrees rise in the air box.

Measuring the air in the engine compartment while the car is moving its about 5 degrees above ambient (over on the air box side). But when the car slows below 20MPH or stops it spikes to much greater.

These numbers are accurate with in 2 degrees, and are measured in deg C

Rob Day

iTrader: (78)

Green filter bought, thanks guys

harvey

iTrader: (48)

Thanks for that Rob.
I think that removing the snorkel will have a different effect on different cars depending on how it is done. Just removing the snorkel and ingesting the air from the inner wing on a Classic most certainly results in a power drop if nothing else is done and after a bit of investigation I concluded it was because the air was in a turbulent condition past the MAF sensor and in to the inlet tract. The power drop was 8.5 bhp or thereabouts on two occasions and the power was restored when the snorkel was refitted along with the duct from the top of the headlight to the inner wing.
The car used for test purposes did not have a mappble ECU and I was not prepared to put more time in to it so I cannot comment on what might happen if it was possible to add some sort of link pipe to smooth out air flow or whether any mapping after that was done would improve the situation. This was on a Classic and I suspect much the same will apply to a New Age but there is a possibility you could pick up marginal gains with some form of link pipe and mapping but until that was done I know that just removing the snorkel on a Classic is a big no-no unless you want to drop power and possibly alter the AFRs which has to be a big risk.
I did not expect to drop power because I had read elsewhere that this was a good mod and when I set off to do this it was simply to check how much power I gained from this popular mod. The fact that I did not gain anything and indeed lost a significant bit of power resulted in me repeating the operation on the rolling road the following day and I am happy as to the care and attention that was paid and have no reason to doubt the findings.
You do get more induction roar and it does sound sportier if that is what you want but 8 bhp plus loss is not what I was after. Had I gained any power I would have gone with that mod.

Splitpin

The problem with reading anecdotal reports is that you don't know how much of the information you're reading is accurate, and, frankly, how much is bullsh*t, or placebo effect (numpty does mod, numpty thinks mod is brilliant, because it's a mod and modz are brilliant), or the usual Scoobynet myth (someone does mod because they saw someone on Snet saying it was top banana, and it must be brilliant cos someone on snet says so).

Harvey has datalogged this, and told you what he found. So have I, and in a variety of configurations from simple delete, to replacement with the proper Subaru smooth pipe, to a cold air feed from the wing straight into the filter box, to running a hybrid configuration which takes a cold air feed from the wing and then runs through the resonator before going through the filter.

I can dig up reams of datalog info that will bore you silly, but demonstrates beyond reasonable doubt (at least on my test configuration) that there is nothing significant to gain from this mod in terms of power, and, depending on your circumstances, potentially a loss, due to the impact on mass airflow measurement accuracy.

For what it's worth the best configuration I found was to run the cold air feed into the resonator, as you maintain the MAF accuracy but get colder inlet air most of the time. However, in order to take full advantage of it, you must have an ECU that measures and responds properly to inlet temp variation - which rules out almost all standard Subaru units, as the ones that do use IAT as an input deal with it in a pretty slipshod manner.

Rob Day

iTrader: (78)

Thanks for the info guys, when i say there appears to be some conflict of interests, I mean exactly what you have said Obviously there is a majority of Subaru owners that think putting on a full decat system to create more sounds = more power...... they obviously unlike myself have not done any homework and think this mod is great. I have done all i can in terms of research and have listened to all advice including yours (splitpin & Harvey) and have hopefull gone down the right route for the car i have.

All the below are being bolted onto the car now by my mechanic all at once and then mapped this Friday. STI pinks, STI Intercooler, Full Stainless 3" (42mm decat up), VF30, Green cotton, Walbro,.. all this was purchased with the advice from people like you. Im hoping that the information i have been given is the best for what im trying to achieve. But it goes to say that people do listen to what they read and hear, so if myths and theories are published then your always going to get the what "if question"