Garrett GTX Series or precision Turbo

[Mike B]

I understand with your notations but don't see how they relate to the numbers on the axis :s

 

me too..

I'd like to learn!

:-)

 

The VATN I looked at (VW) was pretty basic engineering, but then, I'm no expert..

we need to find a wrecked porsche 911 ;-)

Sure Ryan will have a spare few sockets on the back of a syvecs :-)

[CanisLupus]

AFAIR Ryan did run 2 VTG/VNT Turbos on his V8 Build which he broke? He also posted a Dyno sheet in his For Sale thread, low down Torque and Spool where insane

 

Still VNT Turbos are an expensive piece of kit the Porsche turbos cost around 6000€ each then again this could be just the Porsche tag

I'd Love one on a Supra or maybe two of them... ^^

[Ian C]

Hi Ian. We almost have the same turbo and cams. I have a bigger ar tho. Nice to know I love how it drives.

 

I like it too but I don't push it too hard at 1.2 or 1.4bar so I would like to try a faster spooling turbo that delivers the same oomph. I'm a fan of drivability over headline power figures, but I would like to stick to 550-600 bhp

 

 

Could you do a sticky on how to read/work out those compressor maps? Iv always been confused.

I understand with your notations but don't see how they relate to the numbers on the axis :s

 

There's a lot of sites out there that will help you with reading compressor maps but they are a nightmare to get your head around. It's also important to remember that a fair bit of it is estimated unless you've got empirical test data already. The first hurdle is the lbs/min axis along the bottom - that's how much air your engine is ingesting. You don't really know this figure for real but it's based on the capacity of the engine, the revs it's going at, and the volumetric efficiency (VE). I took 90% for these (I think I annotated one of the graphs to say this) which means for a 3 litre engine, at WOT you get 90% of the total capacity actually into the engine, i.e. 2700cc of air. With forced induction this might be higher, but it might be counteracted by the turbo heating the air up. Like I said, it's all a bit of an estimation.

 

The funny thing is though, you have to pick a boost pressure level in order to work this out. So your first decision has to be "what boost shall I run?" and THEN you go "what turbo will enable that?" So I've gone for 1.4bar, or 21psi, as that's a nice balance for power, fuelling, detonation avoidance, and longevity.

 

Based on this boost level, I've worked out the lbs/min for a 90% VE 2JZ engine at a few useful rpm points. The first is 7200rpm, the VVTi rev limit and therefore a pretty good idea of the safe rev limit for the 2JZ in general (Mine runs up to this courtesy of the E-Manage Ultimate). That's 58lbs/Min. If you go for 100% VE as it's turbocharged that's 64lbs/min at those revs.

 

I then worked out a nice low-but-realistic spool point of about 3100rpm, and the lbs/min for that (at 90% VE) was 25. If that fits on the compressor chart without going into the left hand surge area, you're sorted as it's not going to spin up faster than that. I've actually got some empirical test data for boost thresholds from when I was comparing the journal and DBB versions of the T67, so I know that for a lightly bigger and slightly older design turbo, you won't get boost until 3500rpm even in 6th gear at WOT. So I don't think the GTX3076R would be over 400rpm faster to spin up, especially at those low revs.

 

So I plotted these two points on the compressor map and got this:

 

So it fits, just, although if the VE was 100% then maybe the top end would be off the right of the map.

[Ian C]

The curvy bits on the graph show the efficiency of the turbo (i.e. how much it compresses the air to how much it heats it up, higher numbers are better) at certain flow rates and how fast the blades have to spin to achieve that flow rate. So on the graph above, what it's saying is that at 7200rpm:

1) the turbine will be spinning between 115000 and 130000 rpm. It's about 1/3rd past 115000rpm so call it 120000rpm.

2) The turbo is in the 65% efficiency island.

 

And at 3100rpm:

1) The turbine is spinning at 100000rpm

2) the turbo is still in the 65% efficiency island

 

The speed it has to spin at can give an indication of how laggy it would be - the higher the rpms the longer it'll take to get there.

 

Now, those two data points might seems to be 'orribly inefficient, but you can see that as the engine RPMs increase, the nice pink line goes almost straight throughthe most efficient part of the map. It just misses the maximum 78% but stays in the 75 to 77% for the midrange of the engine's RPM band, so midrange torque would be top banana hereas the turbo is working at its best.

 

That's about all I know with regards to this and as I'm self-taught it might be wrong

 

-Ian

[Guigsy]

Great info. Thanks

[Nic]

I like it too but I don't push it too hard at 1.2 or 1.4bar so I would like to try a faster spooling turbo that delivers the same oomph. I'm a fan of drivability over headline power figures, but I would like to stick to 550-600 bhp

 

Didn't realise you were running a GT35R now Ian...... still with the EMU?

[Ian C]

I have found out over the years that the T67 DBB is a just a rebranded GT3582R It's exactly the same CHRA and housings. I'm still with the EMU, yes, it's running things just fine

 

When Grid Racing 2 comes out you'll be able to hear just how fine it's running

[caseys]

When Grid Racing 2 comes out you'll be able to hear just how fine it's running

 

Congratulations I was ruled out due to being auto (discrimination I say!)