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turbo upgrades


august

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there's been a good amount of talk about turbo upgrades / possibilities.. I figured i'd start a new thread to continue on...

GT28 looks good, but i'm not sure about the wastegate configuration? if you could rotate both halves so they could be N9 compatible it'd look good, but i'm not sure about it..

gt28_photo1.jpggt28_diagram.gif

also, check out the exhaust housing, it looks similar in size to the OEM N9T exhaust log, wonder how hard it would be to bolt up (???)

The other one that i was looking at was the GT28-RS Disco Potato hahah, what a name.. the .64 a/r version looks like it'd work pretty well for 'trackworthy' boost levels..

gt28rs_photo.jpggt28rs_diagram.gif

I'd like to get some more specs on both these units.. (couldn't find the garrett homepage :( , anyone know what it is?)

(also, the info and pictures above are from the Owen Developments garrett GT page, check it out!)

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T3/T4 Hybrids are a great turbo - but they're old technology... (They also go for $600 USD here now)

The GT series are the new replacements that at ball bearing - which means they spool to full boost aroung 500 RPM sooner.

That's huge for doing a turbo that still has the upper boost limits of the old style - if not greater.

There also not that bad a price - pretty much what the T3 cost back in the 80's and 90's...

T3/T4 would be a great upgrade for someone on a budget - but I'm hoping I can save my pennies and do it properly with a GT series turbo.

Rabin

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I think you can usually rotate both halves, and you can switch the wastegate mounting bolts with one of the other clamp locations. There are little load distribution washers that clamp the housings together to seal, and the wastegate bracket serves as one of those.. At least that's the way the stock turbo works but i think it's pretty standard?

Aren't the newer generation turbos supposed to have greater efficiency overall as well due to better impeller design? Maybe less turbulence / less heat?

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I think you can usually rotate both halves, and you can switch the wastegate mounting bolts with one of the other clamp locations.  There are little load distribution washers that clamp the housings together to seal, and the wastegate bracket serves as one of those..  At least that's the way the stock turbo works but i think it's pretty standard?

thats was i was thinking about the wastegate mounting, but there were some other pictures that made it look more fixed.. i'll have to find em again

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I see what you mean about the wastegate looking more 'fixed.' But take a look at the middle two pics and the wastegate mounting in relation to the compressor outlet. Doesn't it look like its in a different position in each of the pics?? Hmmm

I like the exhaust outlet as well... looks like it would be compatible with some good custom stuff. Although i have heard of performance differences when the wastegate joins the exhaust stream at different locations. I wonder how it effects exhaust flow by just dumping right in immediately like our oem turbos.

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T3/T4 Hybrids are a great turbo - but they're old technology...  (They also go for $600 USD here now)

The GT series are the new replacements that at ball bearing - which means they spool to full boost aroung 500 RPM sooner.

That's huge for doing a turbo that still has the upper boost limits of the old style - if not greater.

There also not that bad a price - pretty much what the T3 cost back in the 80's and 90's...

OK, thanks for the info. Fast spool up at lower revs and still the good old turbo kick is something I would like to have too. ;-) I haven't even considered a turbo upgrade yet but if I someday do, that GT series sounds like a good choice (if I've enough money to put for that purpose). I've been thinking that the next upgrade could be a front mount intercooler and maybe an adjustable fuel pressure regulator (and lambda sensor + meter).

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Although i have heard of performance differences when the wastegate joins the exhaust stream at different locations.  I wonder how it effects exhaust flow by just dumping right in immediately like our oem turbos.

One Finnish 505 Turbo owner has a custom made exhaust outlet. Wastegate has its own pipe (diameter is about 40 mm) that leads directly to the first muffler. I don't know how much that improves but the car is performing very well and he's happy with it. He told me that it was pretty expensive to have it done.

I haven't searched yet but maybe there are some examples on the net with other engine setups that shows how that affects performance.

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About turbos: That GT25 is nice alternative if you don't need any extra power but like to have spooling bit less rev :( DiscoPotato seems to be good one (there is couple of different models) for this size of engine. Many of Saab ovners in Finland have replaced original with that. I'd like to have one but price in here is too much, over 1000€ :(

V-M

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V-M's "bell mouth" downpipe with the divider for the wastegate gases is definitely better than stock - but from what I've seen and read the "ideal" is to have a divorced wastegate pipe that doesn't merge into the main pipe for at least 36" (~90 cm) if at all. Flow after the turbo is critical for velocity so the less turbulance created the better. I like the idea of running it into the first muffler - but on my car, I'm just having one muffler at the very back under the trunk - so I'd need to merge into the pipe under the car.

Another option I've seen is to keep it separate with a tiny muffler on it as well and just exit it out the side. (Muffler isn't really needed since off the turbo means it shouldn't be too loud. (Only time it goes off is on full boost too... :)

Rabin

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wouldn't adding a muffeler to a external wastegate pipe restric its flow causing some strange activity? spiking maybe? interesting though.

V-M: the GT25 does look like a great stock replacement, but the GT28 looks like it can handle a little more air eh? I'm ideally looking for something that'll help with good power improvement (i don't care quite so much about lag).

maybe i should continue looking at larger alternatives, and try to find something withOUT a wastegate, then run an external gate :)

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Dang - I thought for sure it was a standard T3 Flange...

Muffled wastegate pipe - mufflers can muffle without restriction - in this case it would just change the tone of the sound rather than actually muffling it. Don't think it's needed though - I've just seen it done.

As for sizing - I need response and airflow - but just to support 300 HP. I guarantee you that if you size a turbo properly for what you need and your design goal - it will FEEL so much faster than a car with 25% more peak power and turbo lag - especially since that power gain won't be till the upper reaches of the rev range.

That's just my 2 cents though... :)

Rabin

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August: Remember the wrx STI video i had claiming 385 whp? That guy had his wastegate flow straight out and down and just dump to atmosphere. There are pics somewhere but we'd have to ask Kenny. He said it was LOUD when that thing opened up...like serious loudness.

All this turbo+exhaust talk has me scheming about exhaust systems again.... hold me back plz i can't spend anymore money. I think the 3" system i put together is gonna turn out to be useless... but i still dont know yet. It was fun to make anyway. I'm too stubborn to reduce the pipe to 2.5 to get over the crossmember because it's just gonna be a big bottleneck anyway, and the downpipe transition has always been too ghetto for my taste. I keep thinking about a 2.5 turbo back, with a dedicated pipe (maybe 1.5" or so) for wastegate... oh dear would that be ridiculous. a little tiny striaght through muffler for the wastegate and a nice magnaflow for the 2.5". Of course that would require a new turbo and all... Well, let me know when you get your turbo august, we'll make the exhaust dreams a reality with your car... :)

Honestly right now i'd be happy with a stock system that hadn't been muffler-shop hacked, with a magnaflow 2.5" on the back. thanks mufflers-R-us and previous owner... :-/

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By the way, the honda crx turbo guys used to do some nice work with the old civic HF manifolds adapting them to T3 flanges. They basically used a fairly thick steel adapter with counterbored holes that bolt to the original manifold. Then the adapter had a T3 flange pattern in it too. It's probably possible with the N9t setup although it would push the turbo down a little... hmm, maybe too much. My vote would still go to just fabricating a new manifold. it can't be THAT hard :) Talk about TRICK! V-M knows how it's done.

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trevor: haha yeah i do remember that video.. i dunno though, i'd like to know how loud it *really* is.. what about mating the 1.5" wastegate pipe back into the 2.5 inch exhaust 8 or so feet after the turbo, would that be a no-no?

I really look forward to ripping into the danielson car, too may bills at the moment though :) going to have to wait a few months. i also have to deal with smog in december, so i'm not sure how that'll figure into the timing.. maybe i'll try to get all the parts, then after smog try to make it all happen. bleh!

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I'm sure it would work well but i figure if you're going to go 8 feet why not go all the way! <_< I guess theoretically it would be best to keep the two exhaust flows from ever joining to reduce turbulence but for most applications it probably wouldn't make a big difference anyway. I think most ppl join the gate into the main exhaust stream about a foot back from the turbo. Think about those champ cars, they didnt join the wastegate outlets with the main exhaust streams! haha.

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I like the idea of the wastgate pipe with a little muffler just venting to atmosphere- just aim it at the ground and it would disperse a lot of the noise as well. (Tailpipes that fire at the ground sound so much quieter than the ones that go straight out the back...

I was thinking of the 3" tail pipe dilemma on my own car and I think some options are to weld in a slight U-channel into the floor of the car to accomodate a 3" exhaust pipe over the cross member or split it into two 2" pipes before the cross member, and then into a 2 inlet, 2 outlet muffler, or if you like single exhaust a 2x 2" inlet / 1x3" outlet.

I have another thought of losing the rear tire hanger, putting the muffler in line with the exhaust, then cutting hole (s) through the rear valance so that the pipe (s)comes out in the middle of the bumper... <_<

Yep - I spend FAR too much time customizing my car in my head.... :)

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  • 2 months later...

I'd say that a wastegate without a silencer will give a hell of a noise. That's because the exhaust isn't going through the turbine, so it isn't dampened in any way.

I've read that the best solution is indeed the external wg with it's own exhaust pipe. If the exhaust must be joined, the farther from the turbine, the better.

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