GT17 opinions/thoughts

[strictly_perv]

The plans for the sedan are for it to be a fast road car so I'm after comfort (as much as a 306 will offer) and a torquey fast spooling reliable engine.
After being in Ruans Nanstone I was pretty impressed at the GT17S it has in it albeit fairly laggy with the not so efficient hit side but it pulls bloody well once it's spooled.
So what I'm wondering is what sort of power can these handle without shitting themselves and whether it's even with the effort. I'm only looking for 150-160BHP.
The plus side is the they are plentiful and cheap. I do have a TD04 ready to bolt on but I feel I'd rather something that more usable with an instant low RPM kick.
I know a VNT is the obvious option but I can't be bothered with the hassle and setting up.

[Jenkosowls]

I had been talking to a member of the "derv mafia" and was advised to go for a gt17 and would make respectable power and good drive ability. From what I remember he had said it responds well with 11mm pump. And I'm pretty sure the same person had pulled 170 on a very very smoke tune on 12mm with gt17 when he attended the pug dyno day last year. He is crazy mind!

[darrenjlobb]

Personally I would say no....hotside is to small, gt20 imo.

[ginge191]

well you know how the nanstone responds; besides the chronic lag it's not a bad turbo at all..

[Anton]

GT20...

[Ricky]

I think a 17 would be too easy to kill, GT20 minimum imo.

[darrenjlobb]

well you know how the nanstone responds; besides the chronic lag it's not a bad turbo at all..

No offence meant to you, or ruan, or james, given its his turbo....but IMO it drives like shite....well ok, not shite...but I promise you Ruan will agree, and its his own bloody car....theres nothing worse than a turbo like that to drive, smashing the limiter at k, change gear, and still nothing due to such high lag...there will be GT17 turbos that respond much better, which are in correct exhaust housings, but imo GT20/22 suits applications so much better...espically for giving wide range....

[ginge191]

No I completely agree Darren, and Ruan told me a this; but the delivery from standard turbos is quite awesome; but a decent set up '17 isn't horrendous by any measure

[James]

I don't normally bother posting on the forum but considering it's my turbo in question I suppose I should comment!

The good points with the turbo is
reliability ( I did x k miles then a "short term loan to Ruan" who promptly put 20k miles on it and now a extended unknown loan to the southern members).
power is 160-170
cheap and easy to buy.

The only main downside with that turbo is probably my main mistake and I decided at the time to save time and effort and to have a T2 exhaust housing machined to to fit the gt17 turbine which I think makes the horrendous lag.

So fit one of these directly or as Anton says a gt20 or the current safe common (boring?) way a TD04

James

[darrenjlobb]

( I did x k miles then a "short term loan to Ruan" who promptly put 20k miles on it and now a extended unknown loan to the southern members).

rofl

[strictly_perv]

Money is a main factor in it and generally 20's go for more but I guess it's all about knowing what to search.
I do have a TD04 all ready to go on but let's be honest, they're laggy unless you chase the limiter which is not what I want for the sedan.

[strictly_perv]

Does anyone know what the difference is between a GT2052 and a GT1752?

[Anton]

What are the turbos both of? There are a few variances...

[strictly_perv]

Both off Saabs I believe

[Tom]

GT2052 is bigger and better?

[strictly_perv]

I do have a TD04 ready to bolt in but I'm not sure if it will give me what I want.

[Piggy]

gt1749s is what I would do if I was building another 1.9 and will do if the 2.1 goes bang!

great turbo, cheap and available, spool time is brilliant and power gains certainly suitable

[strictly_perv]

Have you had one piggy?

[Anton]

You want early spool yes? A 17 or a 20 will both give that. I believe my 20 spools quicker than Ruans 17 but you know why...

What reliable power are you looking for? So different to a KO4 in a 205.

[strictly_perv]

Yes I want really quick spool, not mega power just around 160bhp. The K04 was laggy I'm not gunna lie, full boost just after 3k but when it got going to properly flew!

[Piggy]

Have you had one piggy?

[cwspellowe]

TBH.. i really don't see the need for a 1749 when a 2052/56 spools very nearly as quick and is much more in its comfort zone at 150-160bhp. Mine's hitting 20psi by just over 2krpm which I would hardly class as laggy.

Yes there's the cost, but some people are making out that the GT20's are laggy.. far from it. I'd advise anyone considering a newer GT to give one a try if you can find someone with one fitted.

[Tom]

Im confused as to how to the '17 on the nanstone is laggy? Has Ruan been playing with the hotside or something? Surely the smaller '17 would spool faster? Not that you need it at 2000rpm your only going to slip the clutch spin the wheels or lift the head or something gay.

[Ruan]

People are getting horribly confused with "big" turbos...

There's more than one thing that affects the "bigness" of a turbo - I'll list the ones that really affect us anyway.

1. Compressor wheel size - on GT series this is in -indicated by the last two numbers i.e. GT1752 - That means the compressor (i.e. sucky cold side that everyone sees) has an EXDUCER size of 52mm (that's the widest part - google Inducer and Exducer if you want to know more, some people refer to the inducer size, but seeing as we're mostly Garrett, we'll stick to exducer size). The Compressor wheel size almost directly translates to how much air the turbo will move at a given RPM - but obviously the bigger the wheel the heavier, therefore less air. Also the "generation" of wheel makes a massive difference, an old T25 compressor ends up turning into a hair dryer most of the time, it can't move that much air and makes it hot - less efficient - whereas a modern "GTB" i.e. 3rd generation GT series can move a serious amount of air, whilst being very small and not making things very hot.

2. Turbine wheel size - this isn't as easy to see - it's GENERALLY implied by the "frame" size - i.e. GT17 or GT20 - but isn't directly comparable - obviously the bigger the turbine wheel, the more air you can pump through it - great! But the bigger the turbine wheel the more air you need to have to be able to pump through it, when you've only got 1.9 litres of displacement and an 8v head, that becomes a bit of a challenge. That's not the end of the story.

3. A/R Ratio - You'll have heard me bang on about this, essentially, get one of those pocket fans - grab a straw and blow as hard as you can into the fan - it'll probably begin to spin up! Grab a piece of drain pipe and blow as hard as you can into the fan - notice it doesn't move for shit... It's all to do with the velocity of the gas that enters onto the tips of the turbine blades. But notice also, when you blew down the straw, you really struggled to get much air through it, you can blow as hard as you like, but all that happens is you're putting loads of pressure in (and going red in the face..) and not really getting anywhere, but with the drain pipe you can put shitloads of air through, but it's not really moving very quick at all...

That's exactly what affects turbos - that's why my GT17 performs worse on a 1.9 8v than a GT22 with a small A/R. This is why it's always best to get a turbo off a Diesel engine - Petrol turbos tend to have big A/Rs - they usually have 16v heads, spin to 8000+ rpm - that's a LOT of airflow - whereas Diesel has an 8v head and spin to 5000rpm max. But of course, the other way round, if you get a baby HDi GT15, you end up strangling the engine because it simply CANNOT get the gas out fast enough.

This A/R is exactly what VNT turbos adjust - therefore you have all the advantages of a big hotsided GT28 being able to throw shitloads of air through it at higher RPMs, but you're able to get it spinning low down by forcing the gas through it at high velocity.

Essay over - essentially it's more than "get a gt20" or "get a td04" - remember a TD04 would actually be a pretty good turbo, if you had a small A/R on it - it's purely because it's off a 2.0 16v 7000rpm petrol that it lags a bit! However, if you make it much smaller, you'll run into Surge... And that's next weeks lesson.

[Ruan]

https://vimeo.com/23868417

Just in a way to show HOW quickly a GT20V spools... When you see it just ra*e the tyres, that's just me planting the throttle up a very steep hill...

You can see the boost gauge - black gauge on the left, 60psi gauge, so first increment is 10psi, 2nd is 20psi... Running around 20-22psi of boost, overboosts as usual when you first mat the throttle, you can hear it surge a little also for the people who haven't really hear surge, that's that "clicking"/"ticking"/"hissing" noise you hear when you floor the throttle and it hasn't quite picked up.

[Piggy]

ruan rules again

[ste91]

Did you get my PM asking about the TF035 turbo Ruan?

[silverzx]

Ruan strikes back.

[Tom]

The revenge of the Ruan.