help reading compressor map for garrett gt1544v
Turbo Mini Forums

i have read the explanation of how to read a map on the honda-tech forum but it made me feel all dumb. i get what all the number on the maps mean now but i dont got how to relate that to a mini engine?

from the map should i be able to tell max boost that the turbo will output, and whether it will surge or not.(i dont think it will as i have been reading up on the gt17's and read that the gt20 will be likely to surge???correct??)

but i still would like to know if this would be suited to my engine or not? arghhhhh sooo confused!!

can anybody help?

if it makes any difference the engine will be 1330 with a CR of 8.5:1 looking to run around 15psi.

Cheers in advance, James.

You need to calculate the air flow for your engine at the boost you propose. Then check it out on the compressor map.

Have a look at the Garrett tech pages:



If you are struggling, I can do it for you.

Saul Bellow - "A great deal of intelligence can be invested in ignorance when the need for illusion is deep."
Stephen Hawking - "The greatest enemy of knowledge is not ignorance, it is the illusion of knowledge."

cheers Paul, i'll give it a go and then post back up if i get stuck (probably wont be to long!!)

argggghhhhh!!!! why do i just get confused by this!! i read abit and get confused so i break it down and i think i have got it then i read abit further and it contradicts what i thought it all ment!!!! argghh i feel dumb as hell right now!!!

would some one be able to break it down for me so as that i will be able to grasp what the hell is going on?!

possibly work it out but show how you do it? so as that i can try and do it on another map?

arghhhhhhhhhh, James!

try this sheet,

use a VE of 85%

you can read off the flow from the selectable map at the bottom and plot it on your map.

http://www.motorgeek.com/index.php?page=6

right im bored at home so ive been doing some turbo selection sorting.

using the motor geek thingy i can see which turbo will suit my peak rpm at 20psi and be bang in the sweet spot. (if that makes sense to everyone)

thats using a ve of 87% (would that be about right with a fully worked BENROSS head? or am i being foolish?)

using inlet temps of 21 degrees and intercooler out temps being around 40 degrees (what ive read on here as being about the norm) (by inlet temps it loks like they mean ambient as if you up that the IC out temp rises.) these temps are at an IC efficiency of 75%.

i am going to be using a phase 3 so its obviously going to be abit revvy to make the most of the cam. so with the rpm at 7500 it gives me a CFM of 323 and the Pressure ration at 20psi is 2.39. now this is all fine and it puts me right in the sweet spot.

The probelm im having is knowing when it will start to spool up? how do i go about figuring this out? when ever i drop the revs down and the boost down it shoots off the left hand side of the graph which i thought was the surge line and that is not where i want to be? does this mean that the turbo is too big and i need to be looking smaller?


oh yeah and this is done on the gt20 map.

all valid questions by James here, anyone want to answer? I would like to know aswell.

Ditto ^^^^

Anything below 4500 rpm at 20 psi and you are the wrong side of the surge line on the GT2056.

It's the same for most applications. Don't worry about it.

Saul Bellow - "A great deal of intelligence can be invested in ignorance when the need for illusion is deep."
Stephen Hawking - "The greatest enemy of knowledge is not ignorance, it is the illusion of knowledge."

i have seen (a video off) a highly boosted engine surging under load the guy ran a nitrous antilag system but ran out of gas.. it didnt go down too well,

i found this link interesting and helped me understand, abit off topic as its for toyota V engines but the maths is good, a nice collection of maps too..

Yes i moved to the darkside

Instagram @jdm_brett

Saul Bellow - "A great deal of intelligence can be invested in ignorance when the need for illusion is deep."
Stephen Hawking - "The greatest enemy of knowledge is not ignorance, it is the illusion of knowledge."