harvey_smith

While looking for something else I see that Scooby Clinic conducted a panel filter group test which was published in Japanese Performance July 2010. The panel filters tested were K+N, Pipercross, ITG, Do-Luck and Green. I don't remember the full detail of the article but when I recently asked Kevin what filters they used he said they stuck with K+N if it was a car that was going to be kept for any length of time. It may well be that on some cars where the filter is restrictive there are gains to be had from ditching the OE cardboard filter or whatever but the Subaru WRX and STi does not have these problems and like I said, the spread we had on testing four filters including HKS Green, K+N, OE Subaru disposable and STi disposable was less than 2 bhp. I was so surprised by this the test was repeated next day. We also did the test with and without the induction resonator box fitted. This is the resonator box that fits in the inner wing MY97 to 00 and despite the fact that people had been raving out how much power it created we actually found power output reduced from 335 bhp to 327 or was it 328 bhp. This too was a surprise and we repeated the same result the next day. It may be that after a remap there could be more power but removing the snorkel on its own should not be done. Perhaps those claiming that they had more power did not accurately measure accelleration or go to the trouble of getting back to back rolling road figures or they thought more induction noise equalled more power which it clearly does not.

Thank you Don. I understand it was touch and go. The Consultant said 9-12 months for full recovery and I had thought it might be 3 months and my GP has revised that to 6-9 months. I go to see the Consultant this Tuesday and again 1 June and the GP week after this. Best Wishes, Harvey.

Hi Gaz, do not believe all the glossy advertising and folklore that you can read on various forums, this one included. Some years ago I did a series of tests on the rolling road at TEG Sport, Carnforth, with Steve Simpson. The car in question was my STi Wagon which at the time was lightly tuned with a Simtec ECU running with the standard airbox, 440 injectors which were close to maxed out, one of my Hybrid front mount intercoolers, my ported headers and matched uppipe and 3" exhaust. The filters tested were a Green, foam, HKS panel, the OE filter (cardboard), K+N panel and STi which had a cotton wool type filter medium. The spread on the power output from "best" to "worst" was 1.8 bhp. The problem with the green foam was that it allowed through particles the size of sand grains. A new OE Subaru filter and a K+N both produced the same power and were good at filtering. The problem with the OE Subaru was that it would need changing every 3000 miles or so. The STi filter which was disposable and by far the most expensive had the least power output but the best filtration. The spread of results were from 334 to 336 bhp (HKS Green foam which I will not use). The OE cardboard is good but needs replacing frequently so I settled ont he K+N that I can clean and oil several times between service intervals at minimal cost. Like I said, glossy advertising regularly tells lies to bull up a product eg. BOVs that add power or improve accelleration, turbo timers that are not required, exhaust systems that add 50 bhp and other bullshit. Now some time later in one of the Subaru dedicated magazines I saw that Scooby Clinic repeated the tests, similar to me above, and the outcome was similar to the results above. So two individual sets of people have carried out these tests and come to the same conclusion. FWIW, on a Classic I will stick with the OE airbox all the way to 340-350 bhp and on a New Age to somewhere between 350 and 400 bhp.

If you alter the induction and it is beneficial you are ingesting more air for the same fuel and this means there is potential for the engine to run weak. This will cause an increase in temperatures and on an engine where there is a big difference you run the serious risk of picking up a piston in the bore. When I was still learning ten or twelve years ago I fitted my STi 6 Wagon to an APS cold air kit. Less than 25 miles later I had picked up number 2 piston in the bore. This was when APS kits were all the rage and the best thing since sliced bread. With a remap that problem would not exist. So when I got to the bottom of the issues I contacted APS and actually met with their engineering director and pointed out the deficincies/problems and suggested they put a warning on each kit about the potential to run weak and do damage. They continued to sell kits without the warning, despite their protestations that they had the customer's best interests at heart and they went on to preach about being Christian and wanting to help people. They came off my Christmas Card list as I thought they were hippocrites and many others including Bob Rawle now appreciae the potential problems caused by altering the induction and this can happen just be re-routing the air flow. Alter the induction and you need a remap of the fuel to be on the safe side as a minimum. I have found that the panel filters on Classics are good to 330-350 bhp and on New Age cars a bit beyond this. Fitting a K+N filter or any other aftermarket filter I have found does not add power or it is infantesimal. Some systems actually take away power but the advantage of the K+N is tht you can clean the filter and reuse every 3000 miles at very little cost.

Always remember that a little knowledge is a dangerous thing.

Look at your VIN plate. If you have a TY752 box these break in time and beyond 350 bhp, if you run it hard but they can go anytime. If you have a TY754, unlikely, that is good to another 100 plus bhp. If your car is M/Y97/98 (with the TY752) then you need a mappable ECU and the Simtek is a good choice. Better than but also more expensive than an Apexi. Ecutek is for M/Y 99 onwards.

Despite a lot of glossy advertising claims a lot of Octane boosters are snake juice. Nitrous Formula from Roger Clark Motorspot does work as we can prove with the additional ignition advance available but some have no effect so it is a rip off.

Common to all engines not just Subaru. A little bit of ware and it will be there. Nothing to worry about. Rings badly worn would probably smoke all the time. Don't worry about it and enjoy.

A P1 is M/Y 99-00 and all 99-00 ECUs can be remapped using ECUTEK software by an Ecutek licenced mapper. FYI a P1 is basically a 2 door STi 5 or 6 for the UK market intended to slow the flow of Grey Imports at the time. I suggest you get in touch with Bob Rawle who is very capable and mapped Paul's car above on several occassions as he went down the modification trail. rbr@brdevelopments.com Now Paul has a very capable P1 about to benefit from a six speed box. I also see Simon Roe, Jolly Green Monster is on here and he also does Ecutek.

All the MBC does is require a greater pressure before the waste gate actuator opens to release boost pressure. Locate it in the boost feed pipe to the WG Actuator.

OP. ECUs do not cause piston problems but poor mapping of the ECU can cause all sorts of issues so stick with a competant mapper.

Your P1 has a TY754 gearbox and rear diff ratio is 4.44:1. These are capable of working well, a long way past 400 bhp. You can take your car to 380-400 bhp on the O/E internals but to go further you do need a change of pistons and rods. At 380 bhp which is easy to achieve with the full supporting mods these are flying machines.

A puff of blue smoke on initial start is nothing to worry about as long as it does not persist. As the car stands a small amount of oil can form in the bottom of the bore or run down a valve guides and so this is burned on the first few revs. Drive the car gently when cold. As for boost, do not mash the pedal to the floor but apply full throttle smoothly. If your boost guage shows you achieving full boost and holding, it is merely that the sudden application causes a spike and it takes a couple of seconds for the ECU to sort itself out.

If you change to a different turbo you must remap. Your ECU is not remappable as such so you need an aftermarket ECU. Speak to the likes of Bob Rawle regards mapping. You need a front entru turbo for your car so any TD05 16G must be front entry. Other turbos that would do the job would be VF23,24,28,29,30. To exceed 300 bhp you need yellow 440cc injectors. Ensure your has these fitted. These can get you to 320 bhp plus subject to supporting mods. A Walbro fuel pump on a car of this age is advisable.

Typically you will start to max out beyond 320 bhp on 440cc injectors. We actually saw 335 bhp on a car with the standard FPR. As you have an adjustable FPR you can slightly bump the fuel pressure and extend the range of the injectors. 16% pressure increase gives approximately a 4% increase in fuel. With 440cc injectors and VF28 they may both reach the limit of their ability around the same power figure subject to your mods and efficiency of the engine. After 440cc you would need 550cc side feed injectors that are good to around 400 bhp.