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zildjian4life218 10-17-2009 12:56 PM

Saab Turbos on SBC
I went to my local u-pull today and there are two saabs there with turbos on them. They are 2.0 liter engines and my friend said he thought that the flanges were T25. Do u guys think these would work on a twin turbo low rpm sbc. I want to build a low rpm engine that will prolly have a 5000rpm redline on it built primarily for torque.

curtis73 10-17-2009 01:33 PM

Without compressor maps there is no way to guess. Using junkyard turbos isn't a guess kinda thing. Its like building a complete engine then putting in a cam with unknown specs. The chances of it being a good match are very slim. They can be modified within a certain narrow range, but that might be just as expensive as buying the right turbo to start with.

matt167 10-17-2009 02:23 PM

if there cheap enough just pull them. it's not likely they'll be big enough, but in any case, you'll make money putting them on Ebay.. an HX-35 from a dodge Cummings diesel would be good

joe_padavano 10-17-2009 03:59 PM

If the turbo is sized for a 2.0 liter engine, then two of them will still be too small for an SBC.

zildjian4life218 10-17-2009 11:40 PM

i had a feeling that they would be too small. so what turbos would work, the one off the cummins? i want to build a low rpm turboed motor for torque.

zildjian4life218 10-18-2009 08:05 AM

LOL. 4 turbos that would be neat but kinda expensive. The one book i have on turbo charging has a truck with 12 of them on it!

NXS 10-18-2009 10:05 AM

You can calculate if those turbos are going to work rather easily, if not too precisely.

Two simple ways to do this.
Donor engine rated Hp
divided by the number of turbos on it.
multiplied by the number of turbos you will run
equals the estimated Hp you will support.

donor motor rated at 280 Hp
divided by 1 turbo equals 280 Hp
times the number of turbos you will run (2)
equals 560 Hp

this is assuming that the fuel types in both engines are the same (gasoline to gasoline or diesel to diesel).. not that you can't use a diesel turbo on a gas engine, just that this method leave a little to be desired.

a slightly more accurate way if you are mixing and matching is:

Donor motor one size, 2.0 liter times Redline RPM (6000 rpm?) = 12,000
divided by the number of turbos (1) = 12,000

Receiver motor size, 5.0 liter times redline rpm (5000 rpm) = 25,000
divided by the number of turbos (2) = 12,500

12,000/12,500 = .96 or 96% chance of being correctly sized.

keep in mind that this is assuming your target boost pressure is approx the same for the receiver as what the donor motor was expected to handle.

and is a very rough way of determining if the turbo will work. If both of these calculation say the turbos will work, they will work. they may not be the best fit but they will fit and make the horsepower that step one says +/- your engines efficiency vs the donor motors efficiency.

zildjian4life218 10-18-2009 10:08 AM

thanks for the post nxs. I will find out how much power those motors are putting out from the factory. I knew it would be close weather they would work or be too small but i figured if i built it for a low rpm engine maybe they would work.

zildjian4life218 10-18-2009 10:15 AM

from what i got online they were putting out about 185hp.

matt167 10-18-2009 10:33 AM

That way of checking is not in any way accurate... no way will 2- 2.0L Turbo's support 560 HP on most any V8, exceptions would be the late 70's - early 80's Emissions V8's that Ford and Chevy put out. 255,267,265 ect.... there sized to 2.0L 4cyls so 2 would be sized correctly for like a 4.0L V6, then the support for 560 HP would stand... but the real accurate way of checking involves a boost map because they factor everything

zildjian4life218 10-18-2009 11:06 AM

someone mentioned an hx-35. would two of these be a better setup for my build?

NXS 10-18-2009 11:19 AM

Those are just examples...
and for the record i have a turbo that fits 2.0 liter motors that makes 600 hp...

But that's beside the point. In the examples i gave i just used some fictitious numbers....

Let's look at what he has and has found.

saab 2.3L rated at 185 Hp @ 5500 rpm.
I assume (b/c OP didn't correct em) he has a 5000 rpm 305 215 hp?

donor motor rated at 185 Hp
divided by 1 turbo equals 185 Hp
times the number of turbos you will run (2)
equals 370 Hp

Donor motor one size, 2.3 liter times Redline RPM 5500 rpm = 12,650
divided by the number of turbos (1) = 12,650

Receiver motor size, 5.0 liter times redline rpm (5000 rpm) = 25,000
divided by the number of turbos (2) = 12,500

12,650/12,500 = 101.2%
a 1% chance of being incorrectly sized (too large)

going further with this:

The Saab 9-5 Sedan's 2.3L light pressure turbocharged engine uses relatively low boost pressure (maximum boost of about 8.0 psi or 0.55 bar) to deliver boost quickly,
so the turbo's are meant to last 100K miles with 8.0 psi.

so we know those turbo's (2) push 380 hp worth of air at 8 psi
8/14.7 = 0.544 + 1 = 1.544
1.544 * 215 = 332 Hp @ 8psi

332/ 370 = 89.7%
by horse power/boost an 89.7% chance of being the correct size (10% chance of being too big).
if i take 1% and 10% / 2 equals a 5% chance of being too large,
now I'm ready for you to pull out the maps and show me what they say. i'll be waiting.

NXS 10-18-2009 11:59 AM

1 Attachment(s)
here is the map and associated points for twins on a 215 Hp 305

zildjian4life218 10-18-2009 01:02 PM

Question on the compressor maps. So the closer i am to the middle circle the better matched the turbo would be for my build correct? As of now i am thinking about putting it on a 305, cause i have 3 or 4 sitting around and need to build or get rid of them.

NXS 10-18-2009 01:35 PM

yes, there is the middle "island" which is where the turbo is most efficient at.
The way I plotted it out it looks like those turbo's will be almost perfect for a stock 302 or 305 turning approx 5000 rpm.

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