[Mk2] [Turbo] GT3076 upgrade

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androo007
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[Mk2] [Turbo] GT3076 upgrade

Post by androo007 »

Hi Guys,

As part of phase 2 I’m looking at upgrading my current turbo to the GTX version.

I’ve had a good look around, and from what I can see there seems to be a few variations on what people say!

1) The GTX3076 (.63 exhaust side) will perform as well as a GT3582 (Unlikely!)
2) The GTX3076 will increase spool by 300rpm, but give +20-30hp top end power
3) The GTX3076 will do nothing.

Currently I have a GT3076 with a .50 AR compressor side that’s milled out to fit the compressor wheel. Air intake is the standard 2.75” up to an ARC air intake.

I plan to upgrade to the GTX with a 4” intake (standard) which sadly means the ARC will have to go :( but at least I can get a whopping 4” intake on the go instead.

There’s a few reasons that are swaying me away from a GT35…..

1) For a complete refresh, including GTX wheel, Cover, backing plate and CHRA etc done – £660 all in.
2) GT35 spool up is like 5k. No use for me because I’m not a redline driver and I want to keep spool.
3) It’ll still bolt straight up to my existing running gear so its unplug-plug.

What do you guys think? Stupid waste of cash?
Dale_V
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Re: [Mk2] [Turbo] GT3076 upgrade

Post by Dale_V »

what are your aims?

at .63 thats still quite small, id be looking to change the whole lot if youre doing the compressor intake/ chra with billet wheel

ive currently got a GTX3076r 0.82 t4 exhaust 450bhp @ 1.45 bar. kick in the ar$e starts at about 4200rpm. Theres plenty more left in it... I just need to sort my fuelling out
androo007
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Re: [Mk2] [Turbo] GT3076 upgrade

Post by androo007 »

Oh really?

If i wanted to upgrade the exhaust side to a .83

a) Would it still bolt right up to existing downpipe?
b) Would there be a different exhaust wheel needed?

I'm at 422hp @ 1.75bar - so you can see the difference in effiecincy / things i need to improve.

What fuelling are you running?
ashley
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Re: [Mk2] [Turbo] GT3076 upgrade

Post by ashley »

androo007 wrote:
a) Would it still bolt right up to existing downpipe?


Yes the turbine housings are externally the same dimensions (as long as you make sure you get the same footprint (T3/ T4/ etc)

androo007 wrote:
b) Would there be a different exhaust wheel needed?


No- the turbine wheels are the same size (30), it is the ratio between the area of the entrance to the wheel and the radius from the midpoint of the wheel to where you measured the entrance area. On a larger AR the entrance area is larger, so allows greater flow of gas into the compressor wheel before creating back pressure in the entrance to the turbine housing.
androo007
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Re: [Mk2] [Turbo] GT3076 upgrade

Post by androo007 »

Thanks Ashley.

Although I do wonder, I'm not convinced that the .63 would be choking yet..... what do you think?

The extra 300-400rpm lag is quite a lot for minimal top end gain. I personally think i'll gain more from compressor upgrades over exhaust. Sound about right?
ashley
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Re: [Mk2] [Turbo] GT3076 upgrade

Post by ashley »

Generally speaking with the 3S engine design, the main barrier to power is getting the gases out of the head quick enough, these engines hate back pressure.

And from what I've seen, generally on Garrett based turbos, the compressor wheels are able to flow higher rates than the turbine wheels they are paired with.

So in the absence of any other build-specific detail, I would say you should be looking to the hot side to improve flow...and 0.63AR is small for big power. So going to a 0.82AR housing would be a good approach, and the difference in spool may be ~200rpm. If you already have the billet compressor wheel, then you shouldn't be struggling to get on song anyway.

BUT that's all very general stuff- the correct answer would be to do some testing and data analysis on your specific setup, and then decide what you want to do...
Dale_V
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Re: [Mk2] [Turbo] GT3076 upgrade

Post by Dale_V »

androo007 wrote:

What fuelling are you running?


800cc sards & walbro 255.

although I feel that changing the fueling to chase more power might be a bit silly and only for the fact that I know theres more in it. Its quick enough as it is and it SEEMS reliable. chasing figures would just be for the sake of it, and obviously induces more stress.
androo007
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Re: [Mk2] [Turbo] GT3076 upgrade

Post by androo007 »

Awesome help as ever, thanks gents.

Ashley, you are a fountain on knowledge! I guess I have 2 options: uprate hotside only, or sell and buy a new complete unit.

This turbo has only done 6-7k (5k on low power too!) so seems daft to have it completely stripped and rebuilt already.
androo007
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Re: [Mk2] [Turbo] GT3076 upgrade

Post by androo007 »

Ahhhhhhh balls you only live once. Let's spend more money :lol:
ashley
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Re: [Mk2] [Turbo] GT3076 upgrade

Post by ashley »

Just don't, whatever you do, buy anything from Owens...else Sheppy might have a fit :wink:
androo007
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Re: [Mk2] [Turbo] GT3076 upgrade

Post by androo007 »

It's impossible to! I tried again and just plain gave up :roll:

I've put the whole turbo unit up for sale now - if it doesnt sell i'll just upgrade the hotside for £110 and the cold side to a .60 A/R for £100 as it is pretty much new.

Drove the car yesterday for the first time in yonks to get new tyres for the rear, forgot how quick it was!
Martin F
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Re: [Mk2] [Turbo] GT3076 upgrade

Post by Martin F »

Dale_V wrote:what are your aims?

at .63 thats still quite small, id be looking to change the whole lot if youre doing the compressor intake/ chra with billet wheel

ive currently got a GTX3076r 0.82 t4 exhaust 450bhp @ 1.45 bar. kick in the ar$e starts at about 4200rpm. Theres plenty more left in it... I just need to sort my fuelling out


Ditto on this question, you have spent quite a bit on this car, you have barely had a chance to drive her since getting over 400 bhp, why are you looking at spending another 1-2 k on a few more bhp ?
Imo i would wait until the weather gets better then give your build a chance to shine, by may/june you will not only have a better understanding of your car but be able to assess exactly what you want from her. Surely going down this route will help you choose the correct way forward and stop you wasting money.... :-k
androo007
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Re: [Mk2] [Turbo] GT3076 upgrade

Post by androo007 »

At the moment Martin pal it's about effeciencies....

Currently banging out 1.75 bar for 422hp isnt efficient.

My thoughts turned to the bottlenecks; either the chargecooler (new one bought) or the turbo, so looking to see the improvements there.

Anyway, for £250 i can replace the compressor and exhaust housings to a 0.60 A/R and .82 respectivly. So thats what I've done :mrgreen:
Martin F
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Re: [Mk2] [Turbo] GT3076 upgrade

Post by Martin F »

androo007 wrote:At the moment Martin pal it's about effeciencies....

Currently banging out 1.75 bar for 422hp isnt efficient.

My thoughts turned to the bottlenecks; either the chargecooler (new one bought) or the turbo, so looking to see the improvements there.

Anyway, for £250 i can replace the compressor and exhaust housings to a 0.60 A/R and .82 respectivly. So thats what I've done :mrgreen:


I would agree with the chargecooler being a potential bottleneck but these turbos only start to shine at higher boost levels.
The power you are getting is normal for that turbo at that boost, as you are probably aware you can change the a/r and get that power at lower boost with a little bit more lag (not that you will particularly notice it).
My point was simply that you keep changing your mind, upgrading and spending more money. If you step back for a minute, give yourself a chance to enjoy the two as she is now then in a month or two you will have a better understanding as to what you actually want.
Saying the turbo isn't efficient at 1.7 bar so you need to upgrade things is what you (i hope) are telling the wife however Imo follow the above and decide what you actually want from the car.
By following your recent endevours i would recommend getting a BW turbo (£800 odd(same footprint as your garrett)), bigger injectors and going for around 550 bhp, otherwise you will just keep coming back and spending (wasting) more money until that kind of power is reached, you're thinking it, i'm saying it :wink:
Martin F
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Re: [Mk2] [Turbo] GT3076 upgrade

Post by Martin F »

Martin F wrote:
androo007 wrote:At the moment Martin pal it's about effeciencies....

Currently banging out 1.75 bar for 422hp isnt efficient.

My thoughts turned to the bottlenecks; either the chargecooler (new one bought) or the turbo, so looking to see the improvements there.

Anyway, for £250 i can replace the compressor and exhaust housings to a 0.60 A/R and .82 respectivly. So thats what I've done :mrgreen:


I would agree with the chargecooler being a potential bottleneck but these turbos only start to shine at higher boost levels.
The power you are getting is normal for that turbo at that boost, as you are probably aware you can change the a/r and get that power at lower boost with a little bit more lag (not that you will particularly notice it).
My point was simply that you keep changing your mind, upgrading and spending more money. If you step back for a minute, give yourself a chance to enjoy the two as she is now then in a month or two you will have a better understanding as to what you actually want.
Saying the turbo isn't efficient at 1.7 bar so you need to upgrade things is what you (i hope) are telling the wife however Imo follow the above and decide what you actually want from the car.
By following your recent endevours i would recommend getting a BW turbo (£800 odd(same footprint as your garrett)), bigger injectors and going for around 550 bhp, otherwise you will just keep coming back and spending (wasting) more money until that kind of power is reached, you're thinking it, i'm saying it :wink:



ooops :oops: , just noticed you have already said you have bought the .82, my wisdom may come back to haunt you, it may not, Image
androo007
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Re: [Mk2] [Turbo] GT3076 upgrade

Post by androo007 »

Haha! Martin, you're right!

Although, there's a line I have to draw and I'm pretty much there.

Clutch is rated to 500
Injectors will top out even with raised pressure at 475ish
New fuelling would be 700 quid.

Clutch is the major one. I simply can't go higher without then spending 1300 on a better setup and I refuse to do that.

This is the last hurrah and them I'll enjoy it all summer I promise!!!! Haha

Plus don't you get another 50hp with your setup? Maybe it's my tune.

Anyway.... I need something to keep me busy :mrgreen:
Martin F
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Re: [Mk2] [Turbo] GT3076 upgrade

Post by Martin F »

androo007 wrote:Haha! Martin, you're right!

Although, there's a line I have to draw and I'm pretty much there.

Clutch is rated to 500
Injectors will top out even with raised pressure at 475ish
New fuelling would be 700 quid.

Clutch is the major one. I simply can't go higher without then spending 1300 on a better setup and I refuse to do that.

This is the last hurrah and them I'll enjoy it all summer I promise!!!! Haha

Plus don't you get another 50hp with your setup? Maybe it's my tune.

Anyway.... I need something to keep me busy :mrgreen:


Lol, I understand, 8-[ , I am getting a bit more but i have higher boost, different exhaust, ecu, fueling (small differences), different mapper, intake and a 2049 cc engine (give or take), that's why they say every car is different :wink:

After much thought along the same lines i'm not going to waste more money going down this exact route we are discussing, in fact i am pretty close to going the opposite way and calling it a day with the mr2s.
I'm getting older and would rather just have the one car for a change, something not so quick that i can't have fun on 'B' roads with or even something i don't have to fight against to simply get out off to fill up with petrol....

This is where things go doo-lally for me though, finding a daily that fits my bill is doing my head in, for example i have gone from a e46 m3 to a TTrs, from a noble to buying a 350 nizmo and paying for a turbo to be fitted.
I am going for a test drive this weekend in a 08 audi rs4, i have absoulutely no idea where i am going and may end up as i am and just saving even more :-k

I'm looking forward to seeing how much these changes will squeeze from the car, any idea when your hitting the dyno next ?

Sorry for nattering on, had a couple of beers :tumbleweed:
androo007
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Joined: Mon Mar 03, 2014 1:43 pm

Re: [Mk2] [Turbo] GT3076 upgrade

Post by androo007 »

haha understood Martin.

At the end of the day the car is a second hobby car for me. Like many others, something to tinkle with, try and improve and tweak over time to get the best i can from it. This last hike is definately the last hurrah for the '2 as now on the hunt for a 335d to replace the daily hack.

Truth be told if i ended up with the same power but at say 1.4 bar i'd leave it at that.

Next session is at Abbey Motorsport on their hub dyno to dial in the final tweaks with some other MR2 owners getting the full works at the same place as me.
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