Producing full boost early and keeping steady until redline...

[DamnedButDetermined]

I am just brainstorming here and i would like some people to think about this with me. I am not looking for a monster HP engine setup but I would like to produce 12 PSI at 3500 RPM and remain at 12 PSI until redline. Based on the displacement of the KA24 that would mean the compressor would have to be efficient at producing a pressure ratio of 1.88 from 17.63 lb/min to 36 lb/min of air flow. That is a pretty big gap and usually it would mean you would be anywhere from 65% to 80%, depending of the compressor used, throughout the rpm curve. This is a very useful calculator that will give you the CFM or LB/min based on engine and RPM...
Compressor Flow Map Calculator (http://lovehorsepower.com/joomla/index.php?option=com_content&view=article&id=35:compressor-flow-map-calculator&catid=8:mr2-helpful-stuff&Itemid=49)

I have been looking around at compressor maps from this page...
COMPRESSOR MAPS (http://turbocharged.com/catalog/compmaps/fig16.html)
And I think the TO4E "60" would be the best compressor for the job. It would keep me inside the 72% range and it stays inside the 80% range for a long time before dropping back down.

The next thing that has to be worried about it the turbine wheel would have to get up to speed quickly and then a good wastegate would have to keep the exhaust gasses in check for a very long time to keep the turbo from over spinning. I think this would be the Achilles Heal in this idea. Are wastegates reliable enough to do something like this without having to worry too much?

How do I size the turbine side of the compressor so that I can achieve the shaft RPM speeds necessary to keep the compressor at the right air flow? I am in the process of reading Maximum Boost right now but I need to reread the turbine section a couple more times before I know what I am talking about ;) Reading comprehension was never my strong point!

Thanks for sitting through this brainstorm of mine and hopefully you guys can either steer me in the right direction without flaming me too hard :wackit:

Zac

[Walperstyle]

After I purchased my GT3582R I did a lot of math (see video)
update-Turbo Math, and what helped me - YouTube (http://www.youtube.com/watch?v=AasEZE3IK_w&feature=plcp)

Then, after I did a lot of paper math, I found Garrett's boost advisor. It is very good at helping you number crunch.

Personally a GTX series turbocharger, preferably a twin scroll will get you where you want to go. GT28-GT30 with an exhaust housing smaller then the .82 (what I have).

Again, you will get a lot of mixed opinions, but remember, the turbo is just the mechanical aspect of this. A good stand alone and degreeing your cams will allow you to move the power range more. Also the type of fuel you run plays a huge factor on how all of this gets put together, but I'm sure you know a lot of this already.

compressor with more fins should help it spool faster, but you don't want the 'static' fins. I believe the ones with the GTX come in a 8 fin now?

Don't get a GT3582R for a 4 cylinder unless you are building a group b monster. It spools late and might surge on pump gas. This is what I found out via math.


Sorry I can't go into detail, I'm still building my engine. It also took me several days doing some math and re-writing things down before I got use to it, I am a horrible teacher, and your numbers will be way different anyway.

http://www.mcleodsbooks.co.nz/document/photos/001/208/377/large_9780760328057.jpg

[budderigs]

More knowledge of your setup is needed before an answer can be given. How much power do you want. What is your engine base 24e 24de? What cams? What redline?

I am going to assume your running a mostly stock 24de with a turbo. You will want a 6cm2 or .47ar 55ish mm turbine. With a 400ish cfm compressor.

[rb25_s13*CHUKI]

Get a .50 trim turbo

[Kingtal0n]

I think a TO4E 50 trim would be perfect because of the following reasons:
A: cheap
B: Standard and proven 380 WHP turbocharger
C: cheap
D: Use a 48 turbine and it will spool the way you want

[fliprayzin240sx]

Yah, I'll be the first one to tell you not to go GT3582R, shit didnt spool up till 5k on my SR. My vote would be a .86 trim GT2871R if you decide to go with the typical T2 flange, should be fully spooled by 3500.

[Kingtal0n]

Here is a 50 vs 60 trim from one of my previous SR20

on a 2.4 it will spool even faster