Simon,

It is mint isn't it?! Still laughing everytime I boot it...!

Regarding the MBC, yes I fitted it myself. I suppose the correct way IS to have it remapped, but if you were to do that, you wouldn't need a MBC, as the remap would raise your boost levels anyway, along with the fuelling and timing.

If you're going to do it yourself, this is how I'd do it:-

- Always run the car on Optimax, or at the very least Esso SUL.

- Purchase a new universal lambda sensor from a Motor Factor, and a new MAF sensor from a Subaru dealer.

- Purchase and set up a boost gauge, an AFR gauge, and a Knocklink.

- Understand what they are telling you.

- Purchase and set up the MBC. Start off with a boost level similar to standard (11/12psi).

- Drive around using different engine speeds and loads, and make sure the AFR gauge and Knocklink are happy.

- If they are, turn the boost up another 1psi and repeat the above step.

- If you plan on going any higher than 17psi, you'll need a FCD (fuel cut defender). However, if you're still running the stock turbo and TMIC, you'll find that 16.5psi/17psi is pretty much as high as it's capable of efficiently boosting to.

- Eventually, one of 2 things will happen. The Knocklink will start to get twitchy, or the performance of the car will feel no faster (or possibly even slower) than the previous boost level.

- You now have 2 options. Turn the boost back down to the previous level, or purchase some NF Race octane booster.


If you do all of these things, you should be relatively safe. Bear in mind that if you then make further modifications, particularly breathing related, your max boost may be increased without actually touching the MBC. Samco intercooler hoses are a good example of this (although they should really be fitted before messing with the boost, but I didn't...), so keep a very close eye on your AFR gauge and Knocklink. If you haven't fitted a FCD, also keep a very close eye on your boost gauge! Fuel cut is a very scary (and dangerous) thing indeed. Particularly if it occurs in the middle of a bend, or when overtaking somewhere you shouldn't be... ()

Having it rolling roaded after you've finished setting it up is a good idea, to ensure everything is running correctly...

 

Stevie 1,

Useful thread!

It will obviously affect your warranty, so you need to weigh up the pros and cons really. But it does more than change the exhaust note, believe me!

 

Just fitted my H&S downpipe & centre section to match my H&S backbox.

Was a bugger to fit as one of the turbo to downpipe stud bolts had been cross threaded (I assume from factory) so the stud had to be cut off, turbo removed, stud removed, drilled, helicoiled before refitting .....

So finally finished & was it worth all the hassle ???

Ooh yes. It seems to pulls harder thru the rev range & the sound is fantastic

Booked on the rolling road Thursday morning

 

wrxsmo,

I've also noticed my higher gears are performing much better than before. 4th in particular is amazing...!

 

so why are people mensioning running lean when removing cats,so do i remove the cat ,get a new back box or wot,will everything be safe and run ok,thanks for your advise lads.

 

It's quite possible that the people who mention running lean as a result of removing the cats, already had a problem that the removal of the cats emphasised. For instance, say you had a failing MAF sensor. You would already be running lean, but maybe not bad enough to start detting. You then remove the cats, helping the exhaust side of the breathing considerably. This increases the volumetric efficiency of the engine, so it creates more power, which in turn creates more boost, which makes the already lean fuelling even leaner, resulting in det. Just a theory...

As mentioned in the "Useful Thread" above, because of your PPP, you already have increased boost levels, more ignition timing advance, and modified fuelling, which was set up to run with the downpipe cat in place. Removing the cat improves the VE, as mentioned above, which could cause overboost. This in theory could also cause leaner running, depending on the current state of things like your MAF sensor, fuel pump/regulator, injectors, etc. But it's easily fixed with a restrictor with a larger bore. A turn of the wastegate actuator arm can also help.

It's entirely up to you whether or not you do this mod, but if a problem arises as a result of doing it, I wouldn't have thought it would be difficult to fix. Have you got a boost gauge, AFR gauge, and Knocklink...?

 

got none of above not sure on what half of them are either mate.

 

I have the 99dB H&S system as well. Heh heh...Awesome at idle. Lovely sound on full throttle.....definitely the best exhaust I have ever heard.

Unfortunately, the thing I DON'T like about this exhaust is the amount of noise on the motorway. NO, I SAID ON THE MOTORWAY! I've got a Legacy saloon, and it's got more sound deadening. Everything else about this exhaust is the mutts nuts (apart from starting the car early in the morning.....wake the neighbours much?).

I keep wishing I had a way of turning it "off / on".

 

stevie 1,

Boost gauge measues boost pressure, AFR gauge measures air/fuel ratio (reading taken from lambda sensor in exhaust), and Knocklink listens for detonation.


Turbo_Steve,

Mine's absolutely fine on the motorway... strange. But then my music's always louder than anything else!

 

Would like to say thank you for all the kind words they are much appreciated.

Ian

 

No problem keep up the good work!

 

Well another thumbs up for Ian with another good result !

Dyno'd today, my '98 Wrx made (with a full H&S decat system & a green panel filter) 289hp & 269 lb ft/tq.

No sign of detonation & a nice clean torque curve too ! Well pleased

Chris

(& I can't remember if I mentioned how good it sounds )

 

judge,what can i say had the decat done by scooby clinic last friday and it has made a big difference to the power ,it feels like its been chipped or something ,and what lag it had is now gone ,it sounds ace and goes like joe **** mate

 

Nice one guys. It's still my 4th gear that's changed the most. It pulls like 3rd used to. Weird (but nice!)...

Re my Knocklink flash at 3500rpm, used up my last bottle of Millers with my regular dose of Optimax. No more flash. Which is nice. Then at next fill, used 1ml/litre of NF Race. Still no flash. However, I'm not certain 1ml/litre is as good as a bottle of Millers. Car doesn't feel as eager. Will try 2ml/litre next fill-up...

 

judge,could you or anyone tell me what a knocklink is and what it does.

 

You can find some good info on it here.