How to pick a Turbo

[Hobo Ash]

Just wanted a bit of guidance with what to look for when getting a new turbo. I know theres loads of threads on here listing the different ones and what cars they come from but i wondered if it was as simple as just buying a turbo and then adapting the manifold so it fits? Im assuming if theres space in the engine bay and its from a diesel car, then it will work? Im also assuming that if it was a turbo off too small of a car it would be a step backwards, and off too big of a car would take forever to get going.
In my head i can just search for a diesel turbo off a 1.8 to 3L car, make an adaptor and fit it. Is it that simple? I know most things that will work well have been tried, but i thought it might be interesting to try using something random

[bashbarnard]

Yeah youve basically got the genral idea. HOWEVER the bigger the turbo doesnt always mean better. Genrally look at modern diesels that produce your desierd power. Find out what turbo they are running then either learn to read compressor maps OR put a find up on here and we can collectivly help identify and advise if we know about them


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[Dum-Dum]

Yeah best thing is get a turbo off a more modern diesel that makes the power you want or a little bit less (as obviously whatever it is fitted too would take a ~30% power hike before needing a new turbo itself)

You need to decide if you want a VNT or a normal wastegate one and if you do want a VNT electronic or mechanical control. Also look out for some turbos having funny attachments for boost popes or being one piece with a manifold.

[Hobo Ash]

Thanks for the advice Ive seen a few compression map threads on here so I will look into that so I can understand it a bit- il probably still put my turbo suggestion up here to make sure.
I might just stick to normal wastegate, definitely don't want an electronic VNT as I wanted this to be a simple-ish car. Il look into the benefits and see what the more readily available turbos have. Time to get searching!

[Hobo Ash]

Just to hijack my own thread- got a map which says its for a GT2056 so I could practice looking at it.
With a target of 160hp, the turbo needs to be able to cope with 16lb/min which this turbo can.
Boost target would be 25psi, which has a pressure ratio of 2.7. Ive marked the 2.7 with the horizontal line and this intersects the map at 17lbs/min. Am I correct in reading that that top line goes round to 70/71% efficiency for the turbo?
Using a compressor map calculator, my 1.9 engine with an efficiency of 88% can hit 17lb/min around the 3200RPM mark which im thinking isn’t too bad? Or would you say that’s a bit late?
Last thing, the turbo peaks at 24lb/min which using the calculator, the engine hits at around 4400rpm. Which to me sounds good because I wouldn’t need to take the car past 4400rpm for peak power output, is that right? Or will this just result in too many gear changes because itl be too inefficient after 4400rpm?
Not planning on using this turbo, just wanted to check I can understand a map
   

[Ruan]

What's your basis for 160HP = 16lb/min? I assume this is a petrol engine calculator which is spitting that number out - your AFR is going to be significantly leaner than they would suggest, something like 17.5:1 AFR will be about your limit for stopping excessive EGTs. I'd not say that an XUD9TE is hitting 88%VE @ 4000rpm - closer to probably 85%, maybe lower frankly! With those numbers and an optimistic 0.42BSFC - the numbers are 25.2psi boost and 19.6lb/min airflow for 160HP @ 4000rpm. That makes the compressor much better suited for the numbers you're suggesting.

You're still running pretty close to the surge line in honesty, but I suspect the turbine won't drive it hard enough to actually produce that pressure, you might just cross into surge on transients but I suspect your BSFC is actually higher, so you'll need more airflow again, which isn't so bad as it'll keep you away from the surge line.

Your comments about the compressor not being suitable past ~4400rpm are quite right, however, the VE% is dropping significantly at that RPM, so you just end up going down the map for the same boost pressure, which keeps you away from the danger area of overspeeds. Also you're not attempting to burn fuel up there - this is normally where the ECU would start tapering boost pressure down to avoid compressor overspeeding.

HTH.

[Hobo Ash]

Thanks very much for the reply!

What's your basis for 160HP = 16lb/min? I assume this is a petrol engine calculator which is spitting that number out - your AFR is going to be significantly leaner than they would suggest, something like 17.5:1 AFR will be about your limit for stopping excessive EGTs.

The basis was sadly just a page saying it was roughly 1lb/min for 10hp, didn't need to use any figures for AFR or BSFC in the whole calculation so il keep that in mind when calculating it in the future.
Il keep reading up on more bits to better understand it. Very interesting when you start looking into it all

[Ruan]

https://www.rbracing-rsr.com/calcboost.html

Use this - it allows you to put in BSFC, AFR and takes into account the density post intercooler.

[Hobo Ash]

Thanks for that link! Got to try and do some work this afternoon and not just sit typing different figures into the calculator

[Hobo Ash]

Ok so im struggling to find compressor maps, is there a website im missing that has some? Or is it a case of going through other car forums searching for them? Wanted to see if i could find the map for a GTB15V (i know its VNT but il cross that bridge at a later date ) and i was also interested in IHI RHV4 VJ38 as that seemed like something different. Both are from cars that had around 160bhp so thought there were good starting points.
Came across a TF035 but thats apparently a slightly smaller TD04 so discounted that for now. Also assuming theres not some great map creator that i can just put the turbo specifications in?

[rocker8742]

Ok so im struggling to find compressor maps, is there a website im missing that has some? Or is it a case of going through other car forums searching for them? Wanted to see if i could find the map for a GTB15V (i know its VNT but il cross that bridge at a later date ) and i was also interested in IHI RHV4 VJ38 as that seemed like something different. Both are from cars that had around 160bhp so thought there were good starting points.
Came across a TF035 but thats apparently a slightly smaller TD04 so discounted that for now. Also assuming theres not some great map creator that i can just put the turbo specifications in?

From memory Garrett have them listed on the website I believe, maybe worth a look


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