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I'm clueless...How do you read a compressor map?

I've had 3 different people try to explain this to me and they all had a different explanation. I want to get a big turbo for my car and want to do some research.

Glenn 88TC
current mods (13.809 at 98.48mph): ported & polished big valve head(1.89/1.59), ranger roller, gutted upper and ported lower intakes, t3/t4 turbo, MSD 6al, MSD Launch Control, K&N filter, Walboro 255 pump, Kirban adj. fuel reg., ATR header, full 3" exhaust with Dynomax Ultraflow muffler, Star stage III ceramic clutch, Tiny Avenger bleed valve, Weld Draglites with M/T ET Street 26x11.5/15

Winter 2001-2002 upgrades - powerstroke intercooler(mounted full size or it won't be going in), 65mm throttle body, 42lb. injectors, custom grind roller cam, big turbo(60-1 with stage 5 turbine), rear suspension upgrades

Bump, I'm sorta curious myself.

Quote:Originally posted by Dave R:
Bump, I'm sorta curious myself.

With great difficulty! [Image: redface.gif])

Dave, Jababa says merrily new year, and keep on shovelin'. [Image: redface.gif])
If it ain't old, it ain't s***!!!!

not knowing enough to keep my mouth shut,i'll give it a try.
the only way i have ever had it explained to me so that i could grasp the concept was to think in 3 dimensions as if it were a topographical map showing elevation where the % efficiency lines run.
the area under the curve,& where is is,will indicate both how well the turbine is working plus how much air it is moving.
think about where you would like the best power/throttle responce characteristics to be & then look for a 'map' that offers the closest fit.
sizing is a separate issue but if you stick with a turbo of similar size to the t3 or t4 you should be in the ballpark.
i hope that this helps,but if it doesn't keep asking as i'm sure that someone here will be able to help!!
the other given is that if i'm wrong someone will let both of us know.
ken s

[This message has been edited by rotus7 (edited 12-31-2001).]

Quote:Originally posted by joebltzfk:
With great difficulty! [Image: redface.gif])

Dave, Jababa says merrily new year, and keep on shovelin'. [Image: redface.gif])

Oh, yeah well you can tell Jababa that he can bite my hairy A...

Oops, um, no tell him thanks and the same to him and you. I miss his 'wisdom' on the old Ranger board, which nobody seems to go to any more (me included).

Sorry off topic folks but, shoveling makes me cranky.

[This message has been edited by Dave R (edited 12-31-2001).]

This is not easy to explain. A coherrent answer could be longer than anyone wants to read here.

Let's say you know you want 250 hp. A rule of thumb is that 10 hp equals 1 lb mass / minute of engine airflow. So 250 hp = 25 lb/min.

NOw lets say that you plan to get that hp at 20 psi boost. You also live at sea level. The pressure ratio is (14.7 + 20)/14.7 = 2.36

At that pressure ratio and mass flow you can read the compressor efficiency and you can see where that point is in relation to the surge line and the open space to the right.

Ideally you want this point to be pretty close to the "island" of highest efficiency. If you plan on developing the engine further you need to make sure there are still iso efficiency lines to the right and up at about a 30 degree angle. The trick is that if it's too far to the left the compressor will go into surge during the engine rpm runup. That can make the car rev very poorly and harshly and in a worst case scenario could tear a blade off the compressor. If it's too far to the right then efficiency is poor and you can really pour a LOT of heat into the air.

Ideally you want to have a method of calculating the hp and boost pressure all across the engine rev range. You really want to plot the entire curve on the compressor map.

Ideally the curve would start (low rpm, low boost, low mass flow) just to the right of the surge line and would come up as load and rpm increase parallel to the surge line but just to the right of it. Then when boost stabilizes as the waste gate opens the operating point will walk to the right in a horizontal line until max hp is reached. After hp starts to drop at high rpm the operating point will walk back to the left. It's important that the operating point NOT walk across the surge line before you reach your shift point. BAD things could happen.

The problem with all this is that VERY FEW people know or have the means to determine operating point across the rev range.

The ONLY tool that I know of that will do that is (shamelss plug) ICDesigner version 2.0.

I programmed all of that into it just prior to the PRI show. Unfortunately, I don't plan to release ICDesigner Version 2.0 soon. I demoed the software at PRI and am currently in negotiation with a major supplier of turbo systems. I don't know the results of that yet.

Don Haulsee

[This message has been edited by DRHaulsee (edited 12-31-2001).]

[This message has been edited by DRHaulsee (edited 12-31-2001).]

Don - It may be asking for too much generalization, but, given all the latest "buzz" on this forum about the HOLSET series of turbos - is there any way your program could predict how they might stack up against the current "darling" of the 2.3T set, the T3/TO4E/50 trim with the stage III turbine? [Image: smile.gif]

C'ya - RAY

Former 2.3T Courier (carbed/blow-thru) & soon turbo Ranger

[This message has been edited by TurboRay (edited 12-31-2001).]
Placerville, California
(former)  '78 2.3T Courier w/blow-thru Autolite 2bbl carb ~ (current)  '87 2.3T Ranger w/PiMP’d EFI

The link you posted for Holset gives me a blank page.

I need a compressor map for the Holset.

I saw the message where people posted that the Holset has such a and such a mass flow. The problem is what is that without knowing the pressure ratio you can't know the efficiency. Without looking at the rpm runup conditions you could easily have a turbo that supports 500 hp or whatever but crosses the surge line either on the way up or crosses it at very high rpm.

How much boost it takes to get a certain hp level is dependant on the engine/intercooler configuration.

While it's very difficult to do, you need to look at the engine/intercooler/turbo as a complete package.

I kinda laugh when I see comments that the T3 is only good to 22 psi or that an IHI is only good to 18 psi. Under certain mass flow conditions the T3 will easily support 25 psi and stay in the 70% efficiency range.

Garrett publishes a compressor map for the T3 that has isolines up into the 2.8 pressure ratio range. That's 26.5 psi boost at sea level.

A really good Intercooler will extend the operating range of a turbo greatly. The IC increases mass flow even at the expense of pressure ratio.

My experience, instrumentation, and thermal analysis indicates that a stock T3 can be used to produce 300 hp at 24 psi boost but that a really good intercooler is required.

Intercoolers affect the point at which a turbo operates. They will drive the point slightly higher on the pressure ratio side and a LOT farther to the right. IC's will typically pull a compressor away from the surge line.

Don Haulsee

DRHaulsee, thanks for the map reading lesson.

Not that I'm in a position to argue, but haven't I seen posts of close to 300 rwhp using a T3 with less than 24 psi? Is that completely impossible? Does a compressor map give real-world info or is it just a way of comparing apples to apples?
88TC 5sp

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