The fancy billet compressor wheel for my new turbo (next to a standard cast alloy wheel)



The new wheel has two advantages:-

1) Its 20%-25% lighter, so it responds better and spools faster

2) Because it's stronger, the central spindle can be narrower, which means more of the wheel is actually blade, rather than spindle - therefore it will shift more air

I hope Wifey doesn't find out that it cost £100 more than the stock cast wheel....

Thats cheap ! Which turbo ?

I got one myself see -

GT3071 - 0.64AR turbine housing. 56 trim compressor wheel in my old .60AR compressor housing (as opposed to the standard .50AR compressor housing that comes as stock on the GT3071)

Just as I did when I went for the GT2871, I've gone for the smaller turbine housing in an attempt to keep the spoolup point reasonable. I'm expecting positive boost by 2,500, 1 bar by around 3,000 and full boost by about 3,500-3,750

This will give me a 3,500+ rpm usable power band, which means I won't have to redline it to stop it dropping off boost on each gearchange. My estimate is that anything over about 4,500rpm (in 3rd gear upwards) will be enough to stop it dropping into the dead zone

I'm not actively seeking a huge power increase, although it's almost certain that I'll get some increase. The turbine housing was a definite restriction on the GT2871 (illustrated by the fact I only gained 7bhp when I went from 1.5 bar to 1.7 bar). Turbo Dynamics were confident that the bigger turbine wheel on the new turbo would flow a noticeable amount more, which should nudge the peak bhp up a notch or two.

Of more interest to me is the jump in mid-range punch - a result of the better compressor wheel - this is one of the areas where big-power 2-litre Coupes can lack a bit - any Coupe that's over 400bhp will be using a pretty big turbo which will usually give a modest midrange.

It'll be interesting to see how it does on the dyno - my 064AR 2871 was more powerful than quite a few similarly-turbo'd Coupes with the 0.86 housing and it was even pretty close to several 3071s with the 0.64. My guess is that the combination of headwork and cams is working well on my car.

It would be nice to break into the FC Performance 500 club, but I don't see it, personally. If I get 20bhp more, I'll be happy

It would be interesting to see a back to back test on the dyno.

Is this turbo an internly gated gt30 ?

Yes - seeing as I'm not chasing huge power (and seeing as I'm broke) I couldn't warrant going for an externally gated turbo and the associated cost of a manifold

What turbo have you got there tricky? Looks like a GTX something...

And is that a Tial turbine housing I see there?

It's a wastegate....

Have another look at the turbo Nigel... there is indeed a Tial external wastegate, but what turbine housing has he got on the there?

A better way to consider it, is that it will shift the same mass per same P/R at a higher efficiancy point. ie; less heating.

The gated housing on the GT30 turbos I belive is modeled on the gt28 series as the 30's were never originaly designed to go into an internaly gated hot side. Not that it matters since you not chasing the 'pub figures' What does it knock out now 400ish ?

It is a GTX something-71 44mm gate .6 tial housing

Something around that... Leighton Dyno'd it at 457, but if you look at a GT2871 0.64AR compressor map, it's obvious that it simply can't shift enough air to give 450bhp. 410 - 420 would be my best guess

As a wild guess, I reckon the new unit will show 475 on Leighton's dyno, equating to 440 - 450 in the real world

I have my suspitions that garrett maps are a touch on the 'conservative' side too

From what I've seen, the GTX series turbo's do exactly what they say and the compressor maps have been spot on.

Do you mean that when pushed, they will flow more than they claim?

If so, maybe I'm closer to the 450 than I think I am

Either way, I'm pretty sure it won't make 500, so I'm not actually all that bothered. I'm far more interested in how well the midrange is increased - area under the curve

From what I have read, it is the angle on the blade tips that brings the increase in flow and efficiency; if you look closely the diameter at the tips of the blades is somewhat greater than the diameter at the base of the blades.

So, is your turbo now a GTX2871R - one that Garrett don't make but should? If so, that should be a 57lb/min compressor by my rekoning.

I am afraid, that a GTX2871R won't give you any advantage over a GT2871R.
Problem is the hot side - it's too restrictive.
You have a 53.85mm small turbine which is absolutely maxed out at <500HP.
The bigger GT3071R and GT3076R have a 60mm turbine, which will have an absolulte limit at about 640HP. Therefore some people say that the 60mm turbine even is too small for the new GTX3076R - therefore they favor the new GTX3576R.
I think this is the reason why Garrett itself does not offer a GTX2871R variant.
Juergen

That makes sense. The GTX3076R would give a useful 70+ BHP over the GT3076R though, even if it won't top 600 BHP.

I definitely have a 3071, not a GTX'd 2871. The turbine wheel is different and will flow a significant amount more than the 2871 ever did.

TD offered a billet-wheel 2871, but the loss of spool from going up to a 3071 was so minimal I couldn't resist. Price was the same for the 3071 or the 2871

The GT3071R uses a 56.5mm turbine wheel, so not quite a true GT30 60mm wheel, it is bigger than the 53.9mm GT28 turbine.

Yes - The 56,5mm turbine is definitely a better solution than the smaller GT28-unit. Only problem – you will have to use the T25-flange, won’t you?!
I can see two options for this unit:
Turbine 56.5mm 84 for 0.64 AR – this turbine flows 19lb/min -> not really much, 450HP cannot be attained in my opinion - it's less than a GT2871 0,86 AR (21lb/min)
Turbine 56.5mm 90 for 0.86 AR – this turbine flows 24lb/min -> a lot of stuff, this unit is capable to flow >550HP in my eyes…
Something is strange – this means that the different AR’s will include different turbine wheels as well?! You cannot change AR’s by changing the turbine housing, only (as you can do for the GT28RS for example).
Biggest problem will be your T25-flange – it won’t support more than 500HP. It is not possible to change to better flowing T3 or even T4 (which is too big - T3 would be right choice).
Therefore I am afraid that you won’t get more than 500HP out of your unit with 0,86AR because of very restrictive T25.
Update: you have the smaller 0,64AR, I have seen - therefore you will have problems to get more than 450HP out of your turbo...
I really wish you much luck in getting more, but as I stated…
Juergen

Ooooooo, turbo's ..... they're just SO complicated!

Juergen - TD have told me that the turbine wheel is different and will flow significantly more than the 0.64AR on my 2871 - I'll ask Matt Waterman for a proper explanation

I've asked Matt Waterman for a reply to Juergen's detailed post - here it is

Matt's replies in red text



I'm trying to persuade Matt to register on the forum so that he can give us the benefit of some of his experience...

Anything that we can learn from someone right at the sharp end can only be useful for ALL Coopsters

I so don't understand the meaning of the the Turbo numbers and differences.

While I have a sound understanding of how a turbo works, how the figures relate to different bits and pieces is one step beyond me.

So I am going to say. Yes.

I'm with you there, nor do i have any desire to understand them - if mine goes the AA I'll buy another

Update

Turbo is built, paid for and shipped

It'll be at Motormech by tomorrow and back in my hands by early next week or even Saturday if Paul's not too busy...

I then have a further week of trundling around in the 16v, as the 20vt will need mapping before it's subjected to boost

Nigel, to Matt's reply:
The turbine wheel size bears no relevance to the a/r of a housing as shown below:
http://www.turbobygarrett.com/turbobygarrett/turbine_housing_AR_and_housing_sizing
The flow rates given on Garretts website (obviously where the data from the text has been compiled from) will be influenced by the wheel and housing combination but even then they should not be treated as gospel.

Yes - this is normally right. But especially this small GT30 is delivered with two different turbine wheels depending on the ordered AR.
Therefore in my eyes it does not make any sense to switch to a bigger AR (by changing the turbine housing), if you realize that you need more turbine flow and more kinetic energy. Garrett will know why they use another Trim for the wheel, if selling a bigger AR.
Please keep in mind - the turbine makes the kinetic energy of rotation which is needed for reving the compressor wheel.
Any bigger AR will provide you with more energy.
If the energy is too low you won't get the maximum number of revolutions of the compressor wheel which is needed for maximum performance...
Any bigger turbine wheel will provide you with more kinetic energy, if the exhaust gas flow is sufficient.
I know that there always is some difference between numbers on a data sheet and reality.
But it is a good indication for the application.
My opinion (which is based on theory in this case, only) will remain the same: In my eyes you won't get a big advantage from this new wheel, because the hot side with 0,64AR is too small.
Later on we will see, if you have your „real results“… it will be interesting.
Note: Matt for sure is a well experienced specialist. Therefore - Please forgive my “resistiveness” against his experiences :-)

Better solution in my eyes would be the new GTX28R turbochargers... They promise wonderful spoolup at max power output.
Thus the GTX2863R should do similar spool to GT28RS at power output of a GT2871R.
Juergen

I completely agree, especially the last paragraph above.

wibble...

Turbo is being fitted this week - hopefully collect the car on Saturday

The only problem then is that the mapping will be all wrong, so I know I shouldn't drive it

Looks like I might have another week in the sloooow 16v - mapping (& dyno runs) are booked for Saturday 4th Feb