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Performance Modifications for the NG900 / Old 9-3 This forum contains PERFORMANCE related Q&A's for the NG900 and 9-3. This may also include suspension.

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Old 11-11-2007, 05:02 PM   #1
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comparing gt3071 vs gt3076

For a 2.0L trying to make 400HP, you'd need about 26 psi, and 44 lbs/min of air. The compressor map for the GT3071R

http://www.turbobygarrett.com/turbob...R_700382_3.htm

The 2.5 pressure ratio and 44 lbs/min is getting close to the choke line.

The GT3076R on the other hand lands much closer to the inside efficiency island and leaves more room for power latter on.

http://www.turbobygarrett.com/turbob..._700382_12.htm

Anyone think the GT3076 w/ .63 A/R would be to large for the 2.0L? Most people I've seen with the b204/205 with the GT series go with the 3071, but I would like some opinions from people who have actually done these turbo upgrades.
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Old 11-11-2007, 05:22 PM   #2
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I dont know if this will help but I have run both a GT3582R and a GT3571R and the difference was so minimal I couldnt notice a difference in spool up times.
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Old 11-11-2007, 05:23 PM   #3
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yes that does kinda help since spool time is my concern. You also have more displacement than me though
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Old 11-11-2007, 05:26 PM   #4
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Quote:
Originally Posted by Makeyousaab View Post
yes that does kinda help since spool time is my concern. You also have more displacement than me though
Yeah but a GT30 turbo is already a much smaller turbo than a GT35.

I think either GT30 turbo will do you just fine. If your concerned then go with the smaller trim turbo. Both should be fine for your HP goal.
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Old 11-11-2007, 05:39 PM   #5
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I would think a 3076r would be to large for a 2.0L engine. I use a 3071r on a 2.0L & get 22 PSI at about 3700 RPM's. I would think you would have to wait untill close to 5K to get that kind of boost out of the larger 3076r.

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Old 11-11-2007, 05:42 PM   #6
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Quote:
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I would think a 3076r would be to large for a 2.0L engine. I use a 3071r on a 2.0L & get 22 PSI at about 3700 RPM's. I would think you would have to wait untill close to 5K to get that kind of boost out of the larger 3076r.
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Old 11-12-2007, 01:24 AM   #7
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Originally Posted by Makeyousaab View Post
For a 2.0L trying to make 400HP, you'd need about 26 psi, and 44 lbs/min of air. The compressor map for the GT3071R

http://www.turbobygarrett.com/turbob...R_700382_3.htm

The 2.5 pressure ratio and 44 lbs/min is getting close to the choke line.

The GT3076R on the other hand lands much closer to the inside efficiency island and leaves more room for power latter on.

http://www.turbobygarrett.com/turbob..._700382_12.htm

Anyone think the GT3076 w/ .63 A/R would be to large for the 2.0L? Most people I've seen with the b204/205 with the GT series go with the 3071, but I would like some opinions from people who have actually done these turbo upgrades.
Is the quest for 400bhp or whp?
Regarding your figures, 44lb/min is a little overkill for 400bhp, around 40lb/min will do.

Also the pressure ratio with 26psi is ~2.85-2.9 but IMHO that is way above what is needed to get the 400 out from the engine. Of course the other HW should be on the table besides the turbo and it one should see out that they're up for the task in order to achieve the wanted bhp with far less boost.
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Old 11-12-2007, 07:13 PM   #8
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I was thinking base horsepower not whp
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Old 11-13-2007, 11:34 AM   #9
 
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The 3071/.63 will get you to that level pretty easily, and lag definitely isn't an issue.

Vigge has done some latency/response testing with several different wheel and housing combos. I used to have a link to one of the graphs, but it's just as easy if he reposts it. (But I think the engine was 2.3L..)
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Old 11-13-2007, 12:10 PM   #10
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Quote:
Originally Posted by gm View Post
I would think a 3076r would be to large for a 2.0L engine. I use a 3076r on a 2.0L & get 22 PSI at about 3700 RPM's. I would think you would have to wait untill close to 5K to get that kind of boost out of the larger 3076r.

I have the gt3076wg with .86ar turbine housing. Its the same turbine wheel as the larger gt3071wg that supports 400 awhp and the 76mm compressor wheel. I don't have it on the car yet, but will test it soon.

Which gt3076 are you talking about? The same one as me or the middle one or the larger t3 gt3076 with a 60mm turbine wheel and 76.2mm compressor wheel?

What gear are you talking about making 22psi by 3700rpm? That makes a big difference. I make 27psi by 3200rpm in 4th gear with the smaller gt3071 with .64ar turbine housing. I made full boost of 27psi by 3500rpm in third gear.

I am trying the .86ar housing now and its about 3800rpm in third gear for full boost of 27spi. About 300rpm more lag at 6000' in Boulder Co.

John
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Old 11-13-2007, 02:23 PM   #11
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The 3071/.63 will get you to that level pretty easily, and lag definitely isn't an issue.

Vigge has done some latency/response testing with several different wheel and housing combos. I used to have a link to one of the graphs, but it's just as easy if he reposts it. (But I think the engine was 2.3L..)
Have plenty of datalogs from my car and also from other saabs including the 2.0 with GT3071. The problem with this turbo or similar ones is not lag as long as you verify/measure it in the rpm range where the trubo is capable of providing boost and it depends on the rest of the HW and the housing etc. However to some it may feel/ get the impression of it being "laggy" since full boost is not availbale <3000rpm...Lauch for instance from 100km/h in 3rd is faster than a normal stage III can manage.

But in the end one should first make clear for himself what really is the goal, rather than just a single "bhp" figure and to what sort of driving style the car is ment for and what is the rpm range where the bhp/Nm is wanted. Then, once this is done the turbo among with other HW shall be choosen and "oversizing" it will seldom "improve" things.

For intance in my case I mainly build the car for flat out driving, street racing etc. and the wanted rpm operation range 4000+ (5000+ rpms are in use when you run up the gears.) the 4000rpm requirement comes normal start speed on the highway, ie. 90-100km/h in 3rd and you surely dont want to have "lag" there if you wish to succeed. Besides the plain "BHP" value i do look for the power in the whole "rpm" registry, especially 5000+ since if curve drops/fades there the car wont be fast
For daily driving purposes plenty of grunt is available and I do make the std viggen torque around 3300-3500 and 200Nm just after 2000rpms and with the 4.05 final drive you often have more revs than this.


http://ww.stcf.net/viggen/dyno500.jpg
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Old 11-13-2007, 03:24 PM   #12
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JZW I was talking about the GT3076 with 76.2mm compressor wheel, but they don't offer it in .86 A/R , only .63, .82, 1.06 I think. Did you take the turbine side from a 3071 series to get the .86? Because the 76 series has a larger wheel diameter on the turbine side.

Vigge as for hardware, it would be a b204 without balance shafts, and all other supporting harware as far as fuel and breathability is concerned. I may use a different header, perphaps the one genuinesaab offers....

Mike did touch on my main concerns, lag and pushing the turbo too far. I was curious how much more "lag" you would recieve with the 3076 in the event I ever swapped to a b234. It seems JZW became very bored with his 3071 on his b234 very quick

thanks for all the input guys. the best thing is the experience you all offer.
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Old 11-13-2007, 03:37 PM   #13
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Quote:
Originally Posted by JZW View Post
I have the gt3076wg with .86ar turbine housing. Its the same turbine wheel as the larger gt3071wg that supports 400 awhp and the 76mm compressor wheel. I don't have it on the car yet, but will test it soon.

Which gt3076 are you talking about? The same one as me or the middle one or the larger t3 gt3076 with a 60mm turbine wheel and 76.2mm compressor wheel?

What gear are you talking about making 22psi by 3700rpm? That makes a big difference. I make 27psi by 3200rpm in 4th gear with the smaller gt3071 with .64ar turbine housing. I made full boost of 27psi by 3500rpm in third gear.

I am trying the .86ar housing now and its about 3800rpm in third gear for full boost of 27spi. About 300rpm more lag at 6000' in Boulder Co.

John
getting rid of the GT30 hmmMMmmm do want!!!
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Old 11-13-2007, 05:05 PM   #14
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Have you called the guys ate ATP or whatever turbo shop you plan on purchasing the turbo from? They probably do not have saab experience however I am sure they are familiar with these turbo's on a 2.0L engine, they should be able to let you know when each turbo should develop boost.

3rd gear is what I am referring to & it's on a C900. For my car a larger turbo would be horrible, not only due to my trans not being able to take it but the lag I think would be horrible for what I use my car for.
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Old 11-13-2007, 05:33 PM   #15
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Quote:
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Have you called the guys ate ATP or whatever turbo shop you plan on purchasing the turbo from? They probably do not have saab experience however I am sure they are familiar with these turbo's on a 2.0L engine, they should be able to let you know when each turbo should develop boost.

3rd gear is what I am referring to & it's on a C900. For my car a larger turbo would be horrible, not only due to my trans not being able to take it but the lag I think would be horrible for what I use my car for.
i believe it was ATP that i called over the summer they are very helpful, and didn't have a biased opinion cause it was for a saab.
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Old 11-13-2007, 05:37 PM   #16
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Old 11-14-2007, 02:47 AM   #17
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Vigge as for hardware, it would be a b204 without balance shafts, and all other supporting harware as far as fuel and breathability is concerned. I may use a different header, perphaps the one genuinesaab offers....

Mike did touch on my main concerns, lag and pushing the turbo too far. I was curious how much more "lag" you would recieve with the 3076 in the event I ever swapped to a b234. It seems JZW became very bored with his 3071 on his b234 very quick

Here are a few datalogs from on B204 pushing around 400whp with ar. 0.86 GT3071. Design consept is the same as mine, ie "all for GO". Car is with 4.05 final drive gear box, i.e. 9-3.

Start from 3000rpm in 3rd (~70km/h)

As we can se not much happens before 3500rpm, 1.5bar boost by 4000 and max 1.8bar by 4150rpms.

Start from 4000rpms (95km/h, 60mph)

now we getting into the operation rpm range and boost is built relative fast,
10km/h speed increase starting from cruise in around 1.4s is relative quick

Start from 4850 rpms (115km/h)
Now we are talking and is rapid, max boost reached in 1.15 second and the 10km/h speed increase in ~1s


For a stage III car the 10km/h increase in speed from stand still is in most cases 1.2s or more.

By looking the the curves above we can state that the rpm range where the turbo is capable of delivering full and rapid boost is 4000rpm and up and when combined with the 4.05 final drive gear box it translates to 100km/h and up in 3rd. However if the box would be the NG900 model with 3.82 final drive the speed would need to be 110km/h (70mph) above.

Dont get me wrong, the car is of course not "dead" below 4000rpms, but it will feel both slow and laggy compared to performance and responce achieved in higher rpm range. For instance in the first datalog the time for 80-90km/h is around 1s, i.e. faster than what for instance a std viggen can manage. Bhp/torque curve for the car is something like this
http://www.stcf.net/viggen/B204_bhp.jpg

This is the reality one will need to be aware of when tuning a relative small displacement motor with a turbo. The effective rpm range where a turbo operates is 2500-3000rpms and if one is looking for "high" power it must be
choosen so the the rpm range is high, which naturally mens that the low end is lost. If we compare this situation with std turbo applications, it just the opposite, rpm effective rpm range at low/mid rpms, but at higher rpm its dead.

Choosing a turbo/HW to work in the mid rpm range will nice for a daily driver since the car will work deacent both in low rpm range and high, but the "ultimate" go is then lost

Last edited by Vigge; 11-14-2007 at 02:52 AM.
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Old 11-14-2007, 06:25 AM   #18
 
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Nice summation, Vigge.....these are the kinds of graphs I was referring to.

Excellent job....
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Old 11-14-2007, 08:10 AM   #19
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JZW I was talking about the GT3076 with 76.2mm compressor wheel, but they don't offer it in .86 A/R , only .63, .82, 1.06 I think. Did you take the turbine side from a 3071 series to get the .86? Because the 76 series has a larger wheel diameter on the turbine side.

Vigge as for hardware, it would be a b204 without balance shafts, and all other supporting harware as far as fuel and breathability is concerned. I may use a different header, perphaps the one genuinesaab offers....

Mike did touch on my main concerns, lag and pushing the turbo too far. I was curious how much more "lag" you would recieve with the 3076 in the event I ever swapped to a b234. It seems JZW became very bored with his 3071 on his b234 very quick

thanks for all the input guys. the best thing is the experience you all offer.
No, I have the smaller gt3076wg, internal waste-gate its a t25 flange with .64, .86, 1.06 ar turbine housings. It does have the larger framed gt3071 turbine wheel and a 76mm compressor wheel with a different smaller trim.

You are talking about the T3 flanged gt3076 with external waste-gate, they have the .63, .82, .106

I am not bored, my compressor wheel got damaged and I thought it was done, so I ordered a little larger turbo, then found out forced performance would rebuild the gt3071 with a used compressor wheel. The power is awesome for street/strip application, but I wanted something just a little more to get me into the 12's in Denver... The gt3076wg should do that nicely!

This one here... http://www.atpturbo.com/Merchant2/me...egory_Code=GRT

John
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Last edited by JZW; 11-14-2007 at 08:17 AM.
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Old 11-14-2007, 03:21 PM   #20
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Wow, Vigge you have outdone yourself. Those graphs are extremely helpfull.

JZW, thats the turbo I was originally looking at but was worried it would be too large for 2 liters. Which A/R is it? the .86? I was thinking of that turbo but with .64 A/R
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