Quote:
Originally Posted by incisor
Garret VNT-15 or 17 depending on the engine. I think the goal here is come up with lower cost option to a VNT.
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Quote:
Originally Posted by incisor
Garret VNT-15 or 17 depending on the engine. I think the goal here is come up with lower cost option to a VNT.
I hope I'm not hi-jacking this thread but, can anyone explain the differences between these 2 images? They've got me bamboozled:
(They are from the www.turbobygarrett.com website and you need to click on them for a good look)
If I've got it right, one should be the 'standard' GT2052 from a LR TD5 and the other is from a GT2056, which was used in a Mercedes Sprinter van, among other applications. Interestingly, Garrett consider them both to be for engines between 1,400cc and 2 litres but that may just be a petrol/diesel thing, since we don't rev out to 8000rpm ;).
They are very different from each other, but how would you feel that difference in a TD5?
Theoretically, would the 2056 have inherently more lag, or would it give you the kick in the pants we are all looking for, given the right amount of fuel?
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Those images are compressor maps for 2 completely different turbo compressors. The one on the right has a larger compressor wheel, 56mm od with 55 trim, vs 52mm od with 50 trim.
The larger wheel flows more air at the same PR (pressure ratio) and has a higher possible PR, as one would expect.
When you have determined, for your engine displacement and rpm, how much air you want to flow for the required performance, then the PR required to stuff that quantity into your engine cylinders, then you plot the point on both of the maps and see what the efficiency is, and how much room is about that point. Then repeat the process with the given efficiency, etc.
That is just a basic explanation, with much detail left out.
First of all, there are several different GT2052 compressor maps with different trims and slightly different shape maps. The differences aren't huge but they are there. I've used the 52 trim version as the closest to stock for the TD5.Quote:
Originally Posted by Fast Freddie
Clearly when the vehicle manufacturers come knocking they get given a lot more turbo options than the aftermarket does.
There is only one available GT2056 map and that's the one you've used above. I had a turbo built a few years back with a Garrett 56mm compressor and had the choice of about 4 different wheel trims.
But if you want to buy an off-the-shelf GT2056 then the map you've got on the right is the right one. If you snag a GT2056 from a production vehicle it could be quite different.
So now what's the significance.
First boost capacity.
The GT2052 compressor at 160,000rpm can only deliver a pressure ratio of around 2.4. If you are at sea-level with a large enough air cleaner then that's about 20.5psi boost.
The GT2056 compressor map runs to much higher rpm, but if we look at the same 160,000rpm then we're showing a pressure ratio around 2.8. This is ~26.5psi.
What we see here is the bigger compressor wheel has a higher tip speed, so if the turbine spins it at the same rpm then you get more boost.
But in practise the turbine will be turning a little slower due to the extra shaft torque and this will negate some, but not all of the above gain.
This means with the same turbine on each compressor the 56mm will deliver a little more boost across the range.
Now if you want to increase the boost the 56mm is of course the one to have. It has efficiency good enough to be usable up to a PR of 3.5. This is ~37psi.
Maximum flow wise the 56mm is hitting the wall around 30 lb/min of airflow. On a fictitious high compression petrol engine this is enough airflow for about 300hp. Compared to ~22lb/min (220hp) on the 52mm compressor.
I say fictitious because you need an engine which uses exactly that amount of air at that pressure ratio at the rpm for best power. It's a rule of thumb but kind of useful for comparison.
Diesel engines of course run much leaner so consume more air for the power they deliver. At factory tune a diesel runs about 50% more air, in a sensible tune about 30% excess air.
A stock 100kw TD5 consumes about 19.5lb/min at 4,500rpm.
At this point the turbine is producing ~15kw of power to spin the compressor.
If you safely tune up an unaltered TD5 with just more boost and fuel you can get to around 135kw and 400Nm without risk of melting pistons or over-speeding the turbo.
The GT2056 compressor fitted can increase your safe boost to about 31psi which you won't hit until ~4000rpm. You won't be able to get any more low end torque than the GT2052 because the engine needs the higher rpm to feed the turbine and create the higher boost. You'll still be around 400Nm with a clean and safe tune.
But the increasing boost and well matched fuel can keep the torque curve up and still deliver than 400Nm at 4000rpm.
Expect ~160kw at the crank. Exhaust manifold pressure will be about 10psi higher than boost and you absolutely require a functioning wastegate.
The GT2056 isn't the ultimate turbo for a TD5 in any way. But it's a simple bolt on proposition with excellent potential. It's also been well tested by other diesels around the 2.5 litre mark.
Thanks lr110qld and Dougal, it's starting to come a bit clearer for me now.
I'm really grateful for your insights.
If the OP doesn't have any objections, I'd like to pursue this further with some more (hopefully) useful links, questions and a couple of thoughts of my own.
For instance, I now understand what 'Trim' means and I've also had a close look at the diagrams I posted and the differences are clearer - from a simple, visual point of view, we are not comparing apples with apples.
I'm conscious of the fact that I'm a bit of a newbie here and I don't know everyone so, if this is getting up anyone's nose, I'll start a fresh thread :)
Starting another thread is best, unless you post relates to what this thread topic (New td5INSIDE turbo ...........) is about.
First real life experience... that does not seam laggy :)
[ame]https://www.youtube.com/watch?v=X2ESFntEdL8&feature=youtu.be[/ame]
**** me... I thought I was bad...
Just have a Snickers and call time out... Agree to disagree.
Two methodologies, both happy with your results.
José backs his work with warranty.
That's good enough in this case because he stands by his product.
Dougal stands by his Engjneering knowledge and that's fine too.
Just call the cat fighting quits...
"Nothing nice to say? Don't say anything"
Just sit at your keyboard, shake your head if you disagree and move on to the next thread.
And in a Vendor thread - don't hijack.
The best way to test lag is to put the vehicle in gear at idle, then accelerate hard.
Preferably on a non-dusty road so you can see smoke.