Help me choose the right turbo!!!

[Big P]

Ok, I am at the phase where I am trying to gather up as much information as I can. I had another post in this forum about my goals with this engine. I originally was going to turbo the T22SED to 25 PSI in an attempt to make about 400-420FWHP. After making the post, I have downgraded the power output to a more respectalbe 300FWHP hoping to use 15-17 PSI. Now with that being said, I have to do my math all over again, and start looking at compressor maps again. Now, I have sifted through a good bit of them on google(i just did an image search) and am not really having any luck on finding what would be good for this application. Here are some of the specs...

2.2L T22SED CID=134.32
(CIDxRPM)/3456= CFM
in this case at....

2000 RPM-77.73
3000 RPM-116.60
4000 RPM-155.46
5000 RPM-194.33
6000 RPM-233.20

Now, that is assuming 100% VE, which we don't have. Most engines usually get between 80-90% so I will use 85% as my reference VE. SO to get the corrected CFM numbers, you simply multiply by .85 so that puts it at....

2000 RPM-66.10
3000 RPM-99.11
4000 RPM-132.14
5000 RPM-165.20
6000 RPM-198.22

Now, to convert the corrected CFM into lbs/min, you simply multiply by .069 and now the new figures are....

2000 RPM-4.60
3000 RPM-6.84
4000 RPM-9.12
5000 RPM-11.40
6000 RPM-13.68

So you would just use those numbers at the x axis..

Pressure ratio...

(P1+P2)/P2=Pressure ratio

P1 is desired boost in PSI, in my case 15 PSI, and P2 is atmospheric pressure ie. 14.7 PSI

AT 15 PSI of boost, my pressure ratio is 2.02. Use this number on the Y axis and now we can plot on the compressor map graph. Needless to say, I have looked at alot of turbos from T25 and T28's to Super 60 T3's, T4's, To4E and To4B's with no luck, they just don't seem to fit. The closest one that I have come across has been this one..

This one is a T3-40 turbo. Let's see if it will load...



If you plot the points at 2000, 3000, 4000, 5000, and 6000 RPMS you will see that at a pressure ratio of 2.02 and 4.60 lbs/min, the piont is to the left of the surge limit. Same thing with 3000 RPM. Once 4000 comes along, however, it is in the 70% efficiency range. At 5000 RPM it just enters the peak 72% efficiency zone, and stays there until 6 grand. I am ok with the upper RPM power that this turbo will give the T22SED, but there will be very little, if nothing down low, and running the turbo at the surge limit can be very bad from what I have heard and read. What do you guys think? Is this one possible? Got any compressor maps for me to try? I will do all the math, just trying to find what is best for this engine. Thanks for your time. Paul M

[Nubira2.2]

i have a TD05HR-16G6 turbocharger from a EVO VIII in my T22SED
yes it has lag
but the HP and TQ curves are great for a street car daily driven
that goes to the track for 1/4 mile runs
flat torque curve from 4.5 k to redline over 200 of torque
hp is always going up until redline like a N/A car

for me was a good option

[Big P]

Well, I did some more digging on this subject. I took a trip over to bimmerforums. They are a BMW website that had some info on turbos over there. They had a post about some things, one of them being how to see what the turbo will look like as it spools up on the compressor map. Let's see if I get this right. What you do is take your corrected Lbs/min at 2000 RPM(in my case 4.60) and then find the pressure ratio of 1.0 and make a dot. Then, you find the LBs/min for 3000 RPM, and the pressure ratio that the engine will see at max boost(in my case 15 PSI or a pressure ratio of 2.02) and make a mark there. Now, you connect those two dots and you can see how the turbo progression is while it is building boost. Let's see if my modified compressor map will load. Sorry if it looks a little crappy...



I also plotted the points for 4k, 5k, and 6k and I was quite amazed. Aside for the point at 3000 RPM where the mark is to the left of the surge limit, this engine stays pretty darn efficient. Once 4k comes around, it starts pulling. At 5k, the turbo is in it's peak efficiency range, and stays there until redline at 6k. Not too shabby. I am curious though, how bad is it going to be for the turbo to be slightly off the surge line while the engine is revving up? I am not looking to damage anything. So far my searches have not revealed anything that would tell me for certain if turbo damage would result due to that one fact. So what do you guys think, is this a good turbo to chosse for this application? I am hoping it is. Th only thing that bothers me is the 2k to 3k spool progression. You can see as the RPMs go up from 2k, the turbo is at least in some sort of efficiency island. As the engine approaches 2700 RPM(maybe??) is when it goes off the surge lne. It isn't unitl about 3200 RPM(maybe??) that it gets to the right of the surge line and all is well. So for that 500 RPM, can this thing grenade? Or is it possible that the 500 RPM will rev past so quickly that it won't matter? I am just trying to get all these things in some sort of order. Any help or info is greatly appreciated. Thanks again, Paul M