Playing with my turbo...

[Poodle]

Been thinking a lot about reaming the exhaust housing and it's potential uses/benefits and wanted to have a go at it myself. I thought while i was there i might as well make a guide for anyone as clueless as myself. This is specifically for a GT15, no idea if the K03's are similar enough for this to be useful, i would have thought so... The tools you will need:



That's pipe grips, 10mm spanner (i've got two there, one's a rathcet jobby cos i'm lazy), 8mm spanner, 8mm socket, 150mm wobble bar, ratchet, hammer. Will also want the all important dremel that i somehow seem to have missed out of the pic... :blink:

Having acquired a gt15 for the princely sum of £35 (absolutely immaculate condition Gareth, thanks again), i decided that yesterday was the perfect day to have go at ruining it. First things first, turbo's are no where near as complex/scary as people seem to think, so don't be afraid to have a go yourself, just make sure all the moving parts are kept very clean. I've never even looked at one that carefully before yesterday, but the whole process took less than 3 hours and that's bearing in mind i'm a bit of a perfectionist (read anal-retentive), so a good hour of that was spent fettling and tidying, probably unnecessarily. Please note if your turbo is still on the car, i would recommend multiplying that time by a factor of ten or so, absolute pig of a job getting them off/on - see hdi power's guide for details lol.

I would recommend taking a few detailed pre-op pictures of the turbo, so you've got something to compare when checking the profile later on. So, take one turbo...

To remove the hotside there are four bolts that need undoing, the turbo needs to be clamped to be able to get the leverage necessary. Be careful of the wastegate arm and oil lines when you clamp her.



It's a bit tight in places, so an open ended spanner is recommended (10mm in this case)...



When you've undone all four, the two plates they were holding the hotside in place should come away easily...



You will also have to somehow deal with the wastegate as it bridges the hot- and cold-sides. I opted to move the turbo in the clamp so i could get to the boost can's bracket and unbolted it from the cold side (8mm socket with knuckle/wobble bar)...



and disconnected the boost hose (pipe grips).



I would note that doing it like this had the side-effect of leaving the WG flapping around whilst i was trying to work on the outlet, so if you've got a better idea go for it! I just couldn't be bothered to deal with the circlip that secures the arm to the lever, got a history with circlips... :badair:

Now unless you've got a nice shiny turbo (in which case, why the hell are you poking it?), then chances are the hotside will need a bit of persuasion to let go of the cartridge, cue one hammer and a piece of wood...



Shouldn't take much, one gentle rap against the ex-mani port had mine spinning freely. Carefully remove the exhaust housing, taking care not to bash the blades of the turbine...



Remove the remaining chunk of turbo from the clamp and replace it with the hotside, can have it facing whichever way you want, depends what's easiest for you to work on. A good light source nearby becomes very helpful at this point as this is where you let loose with the grinding head on the dremel, the result...




After you've removed almost as much material as you want to, i would stop to check your progress. Thoroughly clean all the metal filings off/out of the exhaust housing and slide it back onto the body of the turbo, just to check that everything is still lining up as it should - ideally you want the gap between the internal face of the housing and the turbine blades to be the same all the way around. Make a note of any areas requiring attention then return it to the clamp to "adjust" as necessary. I actually found it easier to use the coarse sanding head for this, as the grinding head was taking off rather more than i wanted to at the time.

This next part probably isn't necessary, but i did it because i like things to look tidy:
Put the fine sanding head on the dremel and go over your work removing any burrs or bumps, can also take the opportunity to reform (poorly imitate) the progressive edges that existed before you started grinding (this is where you want to be referring to those pictures you took). I also found it a lot easier using the fine sanding head to make any minor adjustments to the shape/curve of the surface to get it just how i wanted. Finally, to get a nice, smooth finish i took the 1200 grit to it, shiny!!

[ginge191]

Im looking at getting a GT15, aiming to get some nice low end boost.
What does this gain exactly? just merely a cleaning process?

[Dan!]

Taking material off the hotside of the turbo means there is more of a gap between the edges of the turbine blades and the housing. Usually turbos are produced with this gap being as small as possible, to make it efficient. When the gap is made bigger (as poodle has done by grinding some material away) more hot exhaust gas (which is used to turn the turbine blades/shaft) can escape past the blades and out of the gap. So in a normal setup and application a GT15 may for example (these are guess figures, but kinda accurate) spool up at 1.5k and then run out of puff by 4k, where once it has been ground/reemed out, more gas can escape so spool time will be lengthened and maximum 'flow' at the top end extended. So Poodles turbo may now operate more in the range of 1.8k round to 4.3k.

In reality this is a fairly crude 'bodge' way of getting more top end flow (and thus more lag, also..) and how well it actually works hasnt reallly been proven by anybody. A few people have done this to T2's on XUD's, Ha11, Matthew, Max tait? But nobody has given any proper evidence it works, and like I say it quite crude really, and in theory will just replicate fitting a slightly larger less efficient turbo.

Hope that makes sense mate, if not just say and il try break it down a bit more

[ginge191]

makes perfect sense Dan, cheers love!
pointless for what im after, im after the opposite, quick spool, out of 'puff' at 4kmax, with some nice low end torque!

nice to know all this though

[Poodle]

Exactly as Dan says: low-rent way of increasing the turbo's flow capabilities. So many downsides it's barely worth it, only real upsides are to reduce back-pressure and make it a bit easier to rev. Only really reposted it to get some content on here for Scott and Foobs to play with tbh lol.

[Matt]

That's awesome dan for someone like me(who is just reading, and have no turbo and no idea on turbos) that's really understandable. Poodle awesome stuff there. Gave me something to read and it's awesome to see what people can do to turbos lol

[Dan!]

That's awesome dan for someone like me(who is just reading, and have no turbo and no idea on turbos) that's really understandable. Poodle awesome stuff there. Gave me something to read and it's awesome to see what people can do to turbos lol

Cheers Matt, thats nice to hear 8-) I usually just type out a load of crap as im thinking about it, but sometimes it comes out quite well and understandable

[Dave]

I found it made a hell of a difference to my t2, remember your backpressure is a total killer and this releives quite abit. I would imagine it would work quite well on a gt15 but as Dan says your still only overspinning a smaller turbine and compressor to an airflow its less efficient at flowing, but in reality I hardly noticed any difference in lag and it spread my torque out lots more and it didnt suffer the dreaded backpressure surge you get at about 4k with one of these stock turbos where you feel like your engines gonna die.

[Poodle]

It's also something to bear in mind if you want to make a home-brew hybrid, will take a lot of trial and error to get it right though, not to mention plenty of blue lol. I'll report back once i've run mine for a while and seen how it goes.