AustenW

Deciding on a new turbo for the ST170 turbo build

Debating a GT35 HTA but concerned it will be too laggy for road driving

The Gt3082 sounds a good unit but I'm concerned it will surge due to the 60mm exh wheel and the 82mm comp

The GT3076 is a good unit with the .8 exh housing but has a limit of 580 bhp

What are people running?
Whats the spool like?

Its sounds nice down the pub to have 600bhp plus but if the thing doesn't spool till 5k rpm its no good IMO

Coments from people actually running a big turbo and not internet gossip would be great

Esp people running GT3071 or over please? (or equivelant)

gus

iTrader: (1)

i think ratboy has a t61 on his (could be wrong but its certainly big enough!)


maybe worth a pm

Chip

iTrader: (3)

The difference between a GT3071 and a GT35 is absolutely night and day in terms of spool.

Rob's astra and my nova have very similar spec engines, but he is on a 3071 and im on a 35

There is 2,000rpm in it for how long it takes to spool, his is going properly just under 3K, and mine is more like just under 5K

3076 sits neatly in the middle and TBH im sure my car would be quicker with one, but as I have the 35 and I dont mind revving the engine (limiter is over 8K as im on solids etc) I have left it for now.

If 600+ is your aim though (mine isnt, 450-500 is all I want), it needs to be a 35 of course.

Luca

iTrader: (2)

Gt3071 on mine had zero lag and spun up like a NA car. (340-380hp)
Light car helps! so you should have no worries.

Being internally gated was the issue as boost crept and was not managable so we never added anymore boost.

Hopefully the external wastegate mod will sort this now!

AustenW

Thanks Chip

I know of guys running a Gt35's that have gone slower due to lack of traction and lag

Engine going in a mid engined car so traction shouldn't be a major concern

AustenW

Good input

A friend of mine runs a GT3071 on a Audi 1.8t in a mid engined car

Has little lag and very responsive and drivable with 400bhp

Chip

iTrader: (3)

Seems weird to describe it as having "no lag" I assume you mean at high rpm (ie well after the boost threshold?)
Even then, I dont see how it can not have a short delay between you opening the throttle and it spinning up, I can certainly feel the lag on any 3071 car I have driven.
Sure its not much, but its certainly not zero.


Agreed on the wastegate, its ok if you want mega boost anyway, but can be hard to control the boost with when you want it to come in reasonably hard but not get carried away.
I actually have a similar problem on my 35 on an external gate, but its cause im only on a 38mm one which exagerates the issues.

Chip

iTrader: (3)

When mine comes on boost, it comes on hard, I would imagine that on normal tyres in a FWD car it would be horrific, but with the mid engined layout it just grips and goes

I still think a 3076 would be better though for my own personal application.

What is the bore and stroke of the engine in question, mine is 86*86.75, and its defiantely better than the same turbo felt to me on the couple of YB's I drove with one.

Porkie

iTrader: (1)

used to to run a GT35... hated it.

went down to a GT3076 and LOVED it.


watch capacity is the engine? whats it gonna rev to.... whats it gonna be used for....

and what gearbox you using....


those are the key questions as you know.

AustenW

Bore 86mm Stroke 80mm

1858cc running throttle bodies and low comp

AustenW

Can you explain what you liked and disliked mate?

Chip

iTrader: (3)

Mine is bad enough on a 86mm stroke, I would hate to reduce it to 80mm and still run the same turbo, it would be getting like on a YB then.

I would (for example) definately sooner have 550bhp from the 3076 on your engine than 600 from the 35

It will gain you 1000rpm.

That said, how high are you revving it? If its a 9Krpm drysumped motor, then the 35 will be spooled in your "midrange" even if its not till 5K!

AustenW

Its a 9k dry sumped motor

Chip

iTrader: (3)

I drove lee's on both turbos, and my view was:
35: midrange wasnt really there, then it came on boost hard and surged a bit for a while which was bad too, top end went well

3076: midrange was awesome, pull like a train, and still pulled well right up to the limiter, ok it probably missed 50bhp for the last 500-1000rpm but it more than made up for it everywhere else, it was also just SO much more responsible when coming on and off the throttle

Chip

iTrader: (3)

With it being low comp too, you may then find that the 3076 cant really cope at the top end of that rev range if you are running big boost.

Despite what Ive just been saying in this thread, for that application I actually probably would then go for a 35!

On a track you will never be under 6K anyway, and from there up the 35 will be fantastic

Porkie

iTrader: (1)

YEP!

AustenW

One of my best mates works for a well known Turbo company

He also suggested the 3076

Sacrifice the top end grunt for spool and driveability = faster out the bends

But when your spending the best part of Ł1500 you need to try and get it right first time

Luca

iTrader: (2)

When my plimsole is southbound and applying some force to the gasoline pedal I experience an instant feeling of propulsion.
It certainly does not feel like im pulling away in 5th gear with a 2 second delay before anything happens.

Chip

iTrader: (3)

would be interesting to see some datalogs showing TPS and Boost, just to quantify how much you get and how soon, mine pulls quite well even off boost, but thats still lag IMHO

AustenW

I know a few guys are running the Turbonetics units with good results

Although they are a good sturdy unit that give good HP I want to try and keep to the Garrett GT if possible

Noticed that Forced Performance in the USA do a GT3076 HTA which flows more air and spools faster than the GT3076

I believe it uses a billet Comp wheel

Porkie

iTrader: (1)

as chip said... if you still gonna be using the seq gearbox and its a trackcar 90% of the time. go for the 35

if you like using it on the road. 3076

AustenW

This is the one

Alot of the EVO guys in the States rate the HTA turbo's over the conventional GT's

http://store.forcedperformance.net/m..._Code=Turbo-FP

Chip

iTrader: (3)

I havent tried the HTA stuff personally, so can only offer experience of the GT series blowers.

Christian and Beccy

iTrader: (14)

We've done GT3076HTA's on Evo's.

lead_foot

iTrader: (1)

So.... are they any good?

AustenW

Any noticable difference over a normal GT30?

zetaboostboy522bhp

hi austen how it going mate , the t61 blower is old school really but still produces good power as we are right in the middle of the compressor map with the boost we are running so ian says theres still some more to come from it , it also starts at 3500 rpm so not bad for the size lol ,but if i was buying a new turbo then i would look at the gt-k range of turbos from turbonetics as these are meant to flow alot better than the t61 i have. i aint no engine builder so iam sure there is people on here who could help you out better than me

around $1700 mark so not that expensive

cheers paul

paulc18rst

iTrader: (1)

GT3071 all day long !! in my opinion the best option

Chip

iTrader: (3)

and.......

TWoods

From experience (16v 2.0) I found the GT3071 ran very close to surge and often did on trackdays later went with BW 258 on basis the surge line is further left and price. With the BW it has no more surge from 2900-8700rpm, the thresholds bit lower compared to the GT3071 (3200-8700rpm) with better response everywhere. During mapping worth noting the turbo seemed more forgiving and allowed further options to explore compared to GT3071 it was limited by the surge problem around the mid range.

Trev

Red16

they perform very nicely from what people say but what you have to bare in mind is the majority of Evo's with gt3076 and gt35's are around 2.1-2.3 litres and anywhere between 94mm and 102mm stroke so would be a bit more responsive when compared to Austins engine running the same turbo.

AustenW

Its starting to look like the Gt3076 HTA with .8 exh housing, I can always try a size up on exh housing if needed

I'm running multi throttle bodies in an attempt to regain some responsiveness back from reducing my stroke

I intentionally built the engine to be more revvy and move the power up the rpm band for track work

AustenW

Hi Paul

I thought about going this route but was advised to go the Garrett route by 2 of my friends who work for a well known Turbo company who spec and rebuild turbos.

They supply alot of tuners and both run Garrett T04Z's on there own cars with good results

Garrett do a motorsport bearing cartridge with a better race that is more robust than the standard item so may look into that as a option

Owen Developments also do a torpedo Compressor nut which as well as looking nice adds a bit of functionality to slightly improve inlet flow

sas

Done a DC2 integra 1.8 with a Turbonetics GTK 450, 80mm bore, 86 stroke.

The car is quite laggey does not start to build hardly any pressure untill 4k goes at 5k. Makes it power at 29psi of boost, but nothing realy before that point.

Big Will_

That my old one Si?

What numbers did it make?

sas

Yes Will, it is.
It made 441bhp (2.1bar) at 5800 then it split its block!! We have a Dart block now, just rebuilding.

I just felt that the GTK was not that responsive compared to other GT Garretts?

Big Will_

Was it a linered standard block it split?

I bought that turbo literally a week or so after it was released, i've actually had a couple of phone calls from the supplier asking for feedback

Be good to see how it behaves once the block holds together!

I've seen plenty of turbonetics turbos before that feel very flat until they hit their 'sweet spot' of the efficiency map at which point they come alive. Maybe the GTK range didn't fix that!

Mike Rainbird

iTrader: (3)

I'd be interested in seeing the compressor map to support that claimed airflow, as in my experience, a GT3076 0.82 a/r is all done in at 530bhp at 32-34psi (and the back-pressure is quite high at that point as well, so you wouldn't want to push anymore boost through it if it was being used on track).

Rs1

iTrader: (1)

Aye the normal gt is a 52lb/min and wont go anywhere near 580. The HTA is 57lb'er and would still be struggling to hit 580.

AustenW

I'm only repeating what they have both told me

These guys do it for a living and spec alot of turbos for tuners as well as running a dyno themselves


http://store.forcedperformance.net/m..._Code=Turbo-FP

Quote:
"The 76mm size HTA wheel has 54.8mm inducer and flows over 57lb/min without dropping efficiency, and works well at pressure ratios as high as 4.5:1 "