Lets look at some compressor maps

[somthin240]

hmm. I must of mapped it wrong. the one I'm talking about is the one that comes stock on the WRX right?

[Redline240]

Does anyone have the compressor maps for these turbos at 14psi? at 18-20psi too if possible? Just to see which is more efficent at higher boost levels...

Still looking for these maps...this is way over my head to make a map, i'm espically interested in how efficent the 50trim/.63ar is at high boost...can anyone help me out?

Redline

[side waz]

Hey everyone whats up.

Wow this is good stuff and I am doing my best to understand it before I turbo my KA in the new year. It's a project with my sponsor. Still having some trouble and I don't claim to fully understand this at all. So I just have a few questions,

1) On the maps there is no RPM points so how did you figure out where the turbo spools in the band?

2) I will be using an S15 T28 turbo, running at 10psi, so where on the maps shown here does it fall?

I appreciate the help guys, thanks very much.

Take care.

Easy

[C-Kwik]

1) You have to calculate it or actually measure the airflow at the varying RPM's. Measuring would be more accurate, but calculating should be close enough. Figuring out where it spools is much more complicated. The maps shown here are only for the compressor. Spool up os dependent on a lot of factors, including compressor and turbine size, efficiency, A/R, mass, bearing type, engine's airflow at different RPM's, and even what your boost threshold is. It's easier to ask around looking at the same or similar turbos and making educated guesses about it.

2) Nowhere. None of the maps shows are for the T28. Youo'll have to locate the proper map before you can start plotting points on it.

[silencer.1]

TD04 13G is the stock turbo on the auto transmission DSM. I know cause I have one sitting here in front of me and that's the block I got it from. It might have come on the WRX's too though.

[gobstopper]

Having been a lurker here for quite a while, I thought I'd share something.

I looked at this thread, and didn't really understand what I was supposed to be seeing on a compressor map. Then I read the turbosaturn.net article, and now it makes some sense. Read that first, if you haven't already.

I read Sport Compact Car most every month, and they rave about Garrett's GT28RS turbo, the 'Disco Potato'. They put it on their project Silvia with the SR20. I wondered how appropriate the 'Disco Potato' would be for a KA24DE, so I did some research the other night. I found a compressor map in Garrett's PDF catalog, so I snagged that, and used the turbosaturn.net article to do some math. Some crappy Photoshop-ing later here are the results.

Some assumptions:

Flow is calculated by the equation

(CID*RPM)/3456 = CFM where CID is cubic inch displacement, RPM is various points in the rev range, and CFM is cubic feet per minute of air flowed.

VE is assumed to be 85%, so the raw numbers are reduced. That number is converted to lbs/min by multiplying it by .069.

Disclaimer: I am no expert. I'm not even an amateur. Consider me a mildly interested geek, and take my conclusions with a grain of salt. I also didn't try to model spool/increasing boost across the rev range, as I would have been inventing a way to do it that I don't know to be accurate or even possible.

Here's the chart:

On this chart, points horizontally are at the same boost level, beginning on the left at 2000 RPM and moving to the right +500 RPM each point until the last point on the right at 7000 RPM. From the bottom up, the boost levels are 5#, 7#, 10#, 12#, 15#, and 18#.

Conclusions: Minimal usefulness for low boost applications. Best for the 12-18 psi boost range, and mighty nice there.

Thanks.