Gtx3071/3076

[steveboyslim]

Recently tested an engine fitted with a GTX3071, .82 exhaust, capped the boost mid range because of surge, but from about 5000 rpm with the duty cycle of the boost controller at 100% (waste gate shut, no leaks) the maximum boost we could get was 26 psi, from 6000rpm to 7000 pressure dropped to 24 psi, so I concluded that the turbo was not pumping enough air as with the original non-GTX turbo we had 32-33 psi from 4000-8000rpm.
Have I read the compressor map wrong as I thought the turbo will do 550 lbs/min at a pressure ratio of 3.
Am I missing something ?
Next test with GTX3076.

Steve

[mark shead]

I have seen 531hp on a gtx3071. It is not a great turbo and the 3076 is the same it's a poor effort from Garret.
I would recommend either going back to Gt version or look towards bw they are much better turbos.

Mark

[steveboyslim]

I have seen 531hp on a gtx3071. It is not a great turbo and the 3076 is the same it's a poor effort from Garret.
I would recommend either going back to Gt version or look towards bw they are much better turbos.

Mark

The turbo is on a classic car so will be Garret will be staying, but I understand what you are saying, it was a vast improvement over the original Garret .
What I am a bit confused about, is that after confirming that we had no leaks from the induction, the turbo would not pump enough air/boost for the required 30 psi and then dropping pressure, yet that turbo should have able to provide that pressure and more.

Steve

[mark shead]

The turbo is on a classic car so will be Garret will be staying, but I understand what you are saying, it was a vast improvement over the original Garret .
What I am a bit confused about, is that after confirming that we had no leaks from the induction, the turbo would not pump enough air/boost for the required 30 psi and then dropping pressure, yet that turbo should have able to provide that pressure and more.

Steve

A bit more detail would be good. Int gate ot ext what Spring pressure what boost control system. Was it a brand new original manufactor garret turbo and not a rebuild turbo to a claimed gtx spec. Also what power.

Mark

[steveboyslim]

A bit more detail would be good. Int gate ot ext what Spring pressure what boost control system. Was it a brand new original manufactor garret turbo and not a rebuild turbo to a claimed gtx spec. Also what power.

Mark

Genuine GTX with genuine three inch intake keeping the look original, engines have done more than I want with a three inch inlet.
Waste gate vented from the top.
Adjustable spring pressure I do not know same setting as before.
From the duty cycle external gate is fully closed (even tested mechanically forced shut)from about 5000 rpm engine only took about 24 psi before surge at about 3500 rpm rising to 26 psi (I wanted a bit more)until 6500 rpm were the pressure dropped to 24 psi, 23psi at just over 7000 rpm, did not try further.
Boost control with a GM Calibra/Cavalier turbo three port amal (soon to be replaced with MAC valve) which worked ok with the other turbo which made 32+ psi from 4200 rpm to 8500 rpm.
I don't think the engine will do much more that 510 bhp,
Only thing changed was the turbo, same engine dyno same intercooler both turbos tested on the same day.
I was expecting the turbo to make 30+ psi and hold that until max rpm controlled with the amal valve.
To me it looks like the turbo is too small, where as it should be more that caper able.

Steve

[mark shead]

Where you feeding the top of the wastegate with air to hold it shut.
As far as I am aware all gtx Come with ported cover so when you say gen garret can you check if it's just a machined cover made by garret or a garret sold part.
I have seen many turbo companies bull shit when it comes to parts and you end up with shit.
Gen garret to me comes direct from garret in a garret box with no options.
How far out was it from 510hp as boost held is not that important on small turbos and I do call a gtx 3071 small

Mark

[mark shead]

Black line gtx3071 single scroll .82 and ported shroud.


Mark

[steveboyslim]

Where you feeding the top of the wastegate with air to hold it shut.
As far as I am aware all gtx Come with ported cover so when you say gen garret can you check if it's just a machined cover made by garret or a garret sold part.
I have seen many turbo companies bull shit when it comes to parts and you end up with shit.
Gen garret to me comes direct from garret in a garret box with no options.
How far out was it from 510hp as boost held is not that important on small turbos and I do call a gtx 3071 small

Mark

Under the diaphragm, top to atmosphere, as tested with the original T3/4 turbo.
Tried with the gate wedged shut with the GTX no better.
Three inch inlet is a genuine option (as ATP list) not a machined GTX28 cover.
RS500 had three inch intake and made 580 bhp.
The original obsolete Ford/Garret turbo is effectively a T4 RS500 compressor with a T3 .82 exhaust.
GTX 490ish bhp, dropping as the boost pressure dropped, original T03/4, 505ish at 32 psi, tried up to 35 psi limited by Weber MAP sensor, from a previous test we found a 3 psi drop from dyno intercooler to car intercooler installation a slight increase in spring pressure in the car sorted that, that is the waste gate setting we had when dyno tested.
I think it was one of your graphs, combined with the turbo spec that I based my decision to use that turbo

Steve

[mark shead]

Under the diaphragm, top to atmosphere, as tested with the original T3/4 turbo.
Tried with the gate wedged shut with the GTX no better.
Three inch inlet is a genuine option (as ATP list) not a machined GTX28 cover.
RS500 had three inch intake and made 580 bhp.
The original obsolete Ford/Garret turbo is effectively a T4 RS500 compressor with a T3 .82 exhaust.
GTX 490ish bhp, dropping as the boost pressure dropped, original T03/4, 505ish at 32 psi, tried up to 35 psi limited by Weber MAP sensor, from a previous test we found a 3 psi drop from dyno intercooler to car intercooler installation a slight increase in spring pressure in the car sorted that, that is the waste gate setting we had when dyno tested.
I think it was one of your graphs, combined with the turbo spec that I based my decision to use that turbo

Steve

Ok so not a straight Gt to gtx swap. I think the diff in back pressure would have been the problem. A Mac valve bleeding to the top of the gate will sort the problem you have.
That graph is that very set up for boost control.

Mark

[mark shead]

What make and size gate did it have.

Mark

[steveboyslim]

Original Ford waste gate which I believe was made by Schrick, 38mm.
Four port MAC valve on order.
I am thinking my original Garret three inch cover may not be as original as I have been told, if the compressor housing profile is not as accurate as Garret that might explain the pumping losses.
I have a four inch ported shroud inlet housing on order.
If you are talking exhaust gas back pressure, I am using .82 T31 4 bolt, same size supplied with the GTX3076 which has the same size turbine.
Bit of extra machining to remove some of the casting flashings past where Garret machine and then at the 2 1/2 inch flange the exhaust opens out to three inch pipe.
I am stuck with what Garret sell.

Steve

[mark shead]

Is it internal gated as I am not sure if you answered this and do you have a pict of it installed.

Mark

[mark shead]

The normal gt3071 is a good turbo a bit down on power to a gtx version but a much better turbo. The same goes for the 76 version also.

Mark

[steveboyslim]

The normal gt3071 is a good turbo a bit down on power to a gtx version but a much better turbo. The same goes for the 76 version also.

Mark

External gate.
Waste gate is mounted on the collector, with the screamer pipe fed back into the down pipe.

http://silodrome.com/ford-rs200/

Shows the basic install we are using the same exhaust manifold, primary pipes are a bit small and are of unequal length, but got to be original.
Engine capacity is 1952cc.

Steve

[mark shead]

External gate.
Waste gate is mounted on the collector, with the screamer pipe fed back into the down pipe.

http://silodrome.com/ford-rs200/

Shows the basic install we are using the same exhaust manifold, primary pipes are a bit small and are of unequal length, but got to be original.
Engine capacity is 1952cc.

Steve

Why did I think it was a Vaux engine,
You would need around a 1.5bar+ spring in wastegate and run the top port also this is the only way it will work correctly.

Mark