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Discussion Starter · #1 ·
I have a Viggen, and would love to get a flat 300 ft/lb torque curve (measured at the crank) from 2000 to 6000 rpm, with enough margin of error that I can run it on the occasional track day without fear of high temps and breaking things. I don't want a 325 pound torque spike at 3500, and i don't want it totally dying at 5400.

Put another way, what is the most torque that can be sustained equally and flat all the way from 2 to 6K on a b235, and what do you use to get it?

Is my goal possible with the usual bolt-ons and a td04/5cm turbo with the cobra pipe modification? If not, what is a reasonable flat and wide torque goal for that turbo? If I go to a td04/6cm Aero turbo, still with a 15t compressor wheel, how soon could that turbo spool to give 300 lbs torque?

If anyone has a tune or dyno graphs that might show similar numbers, I'd be most appreciative. Thanks very much for any advice/suggestions.
 

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Hello stevbd,

A 19T would work well. A friend/fellow forum member managed around 300whp/300lb.ft. using a TD04-19T and 6cm^2 housing, with a clipped turbine. The same turbo and built motor is now making in the neighborhood of 350whp, on E85.
 

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Keeping the exhaust wheel smaller is very important as it allows boost to occur earlier. Clipping vanes is a bad idea as it pushes the starting boost further up the rev range, as does larger exhaust turbines, which means boost will happen later which you said you don't want.

So, bigger compressor side with smaller exhaust side. Then consider new T5 cams or custom cams that target the lower to mid range power band. (High mileage cams will be worn and not the same spec anymore and you'll loose some performance) With a T25 .48? (think it's around that size) A/R exhaust housing and no cat I was seeing boost at 1800, (1500 if I lugged it in 5th) and it was taking 16 PSI to 6200 redline. With a factory cat it'd start dropping PSI around 5500. This was with a factory 2.25" down pipe and 2.25" exhaust, with a Summit Racing Turbo Muffler. I'd suggest a strait thru design muffler for more unrestricted flow though, and the best flowing cat you can find. This will help you with your goals. It's actually the same way I'm building mine (pretty clear if you read some other recent posts where I've been rambling on). Whatever exhaust wheel you have now, don't go any larger or you'll be spooling later like 3300. People will argue this one, but keep the exhaust at 2.5" for the largest size. It'll promote more low end. Your turbo will be already spooling early anyways (as opposed to guys who start spooling @3000 and need as much help as possible to fight lag with bigger DP and exhaust). If you start getting over 340hp, maybe consider a larger pipe. Remember, anytime the car is off boost, it's acting like a naturally aspirated car. If it only makes 110 hp in NA form, than a full 3" exhaust will kill the NA's side performance as there will be no back pressure (run your car with NO boost for a day and you'll see what I'm talking about :cheesy:). If you keep a cat on the car, Get the best flowing one you can find as it'll hinder performance the most.
 

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Discussion Starter · #4 ·
I should've mentioned, I've got a mild nordic stage 3 tune, GS dp and sport cat, and 2.5" BSR exhaust on it already.

Again, I'm willing to compromise big torque numbers in exchange for a wide and flat torque curve. I don't think a 19t clipped or the stock downpipe are the right hardware for what I'm trying to achieve.
 

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re

IM by no means an expert but I think that by nature the turbocharged engine just doesnt have a flat torque curve,particulrly the bigger ones.Supercharged engines are better for achieving that.I might be wrong though.
 

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IM by no means an expert but I think that by nature the turbocharged engine just doesnt have a flat torque curve,particulrly the bigger ones.Supercharged engines are better for achieving that.I might be wrong though.
I see a lot cars advertising like 80% of the TQ available throughout the rev's
 

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Keeping the exhaust wheel smaller is very important as it allows boost to occur earlier. Clipping vanes is a bad idea as it pushes the starting boost further up the rev range, as does larger exhaust turbines, which means boost will happen later which you said you don't want.

So, bigger compressor side with smaller exhaust side. Then consider new T5 cams or custom cams that target the lower to mid range power band. (High mileage cams will be worn and not the same spec anymore and you'll loose some performance) With a T25 .48? (think it's around that size) A/R exhaust housing and no cat I was seeing boost at 1800, (1500 if I lugged it in 5th) and it was taking 16 PSI to 6200 redline. With a factory cat it'd start dropping PSI around 5500. This was with a factory 2.25" down pipe and 2.25" exhaust, with a Summit Racing Turbo Muffler. I'd suggest a strait thru design muffler for more unrestricted flow though, and the best flowing cat you can find. This will help you with your goals. It's actually the same way I'm building mine (pretty clear if you read some other recent posts where I've been rambling on). Whatever exhaust wheel you have now, don't go any larger or you'll be spooling later like 3300. People will argue this one, but keep the exhaust at 2.5" for the largest size. It'll promote more low end. Your turbo will be already spooling early anyways (as opposed to guys who start spooling @3000 and need as much help as possible to fight lag with bigger DP and exhaust). If you start getting over 340hp, maybe consider a larger pipe. Remember, anytime the car is off boost, it's acting like a naturally aspirated car. If it only makes 110 hp in NA form, than a full 3" exhaust will kill the NA's side performance as there will be no back pressure (run your car with NO boost for a day and you'll see what I'm talking about :cheesy:). If you keep a cat on the car, Get the best flowing one you can find as it'll hinder performance the most.
I'm not sure why your goal is to spool much sooner than 2000rpm. Have you never attempted to floor your car with the stock turbo? Doesn't result in very much acceleration.

Clipping the exhaust of a turbo the size of a 15T, 19T, is such a small tradeoff for the benefits it brings that it's negligible. I've got a pretty decent sized exhaust wheel you could say and I start seeing boost around 2500rpm, full spooled to 35psi if needed by 4000rpm. Whatever exhaust upgrade you throw at the TD04 will not bring it anywhere near those numbers.


Also OP, I just noticed that you said you'd like 300lb.ft. of torque between 2000rpm and 6000rpm. That's a really tall order. You can get a turbo that spools early and spike it to make a decent amount of torque but it'll fall on it's face right after. If you're really wanting that amount of torque that fills your midrange, a 19T or a T28 is really what you want.

Here's a dyno of a T28 on a 9-5. The T28 is definitely a step up from the T25 but is still pretty small. Yes, the exhaust size is bigger but of course it is. You can't just keep upping the compressor without touching the turbine - it just doesn't work that way.



For what you're trying to achieve, you're not going to get away with sticking to the stock turbo. I don't know how else you're expecting to achieve a flat torque curve without upgrading to at least the bigger wheel that can maintain the boost. Yes, you can probably spike the boost on a 15T to reach 300lb.ft.++. But I bet it doesn't even last 1000rpm.
 

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its hard to get a high even tq curve on a small motor. its a 4 cyl. unless you built a stroker 4 cyl with cyl bored out and a cam grind to for mid range power, its gonna be hard to get an even tq curve, its the nature of the beast. now i can see why you want a nice even tq curve. great acceleration at any speed. but there are so many tradeoffs with a 4 cyl and power. you just have to pick a place you want the power and stick with it.
and dont get me wrong. i love my little 4 cyl turbo. im not knocking 4 cyl. both of my vehicles have them.

find a quick spooling turbo that gets to peak psi quick and doesnt drop on its face at high revs and thats your winner. but isnt that the goal of every turbo? rx7s had a bi turbo setup, one for low revs and a second for high. like i said, find your medium and live with it.
 

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Discussion Starter · #11 ·
I get what you're saying, I do. But just to be clear, my goal was 300 lb/ft measured at the crank, not at the wheels. So maybe something like 250-270 at the wheels. Am I dreaming even with those numbers??

Does anyone have a chart of an ecu tune on a 9000 Aero with its stock 6cm/15t turbo? I'd be curious to see how that turbo - without the 18/19t conversion - spools and holds torque towards 6K rpm on a 2.3 liter.

BTW, tap804, I like the look of that graph a lot. ;ol; A 3.5L diesel would be cool in a viggen, for sure....

Thanks for the advice and help.

EDIT - Also, for the tuning guys, is it hard to do a tune that dials back the natural midrange torque spike?
 

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reaching 300tq at the crank isnt a hard goal or impossible. its just gonna be harder to keep that tq through the whole rpm range. the lower your peak tq, the more achievable and even tq/power curve. im not an expert on turbos or saabs so i cant tell you how to achieve your goal but a 250 even tq curve to the wheels is easier to do and more realistic than 300 even even tq curve to the wheels. get what im trying to say? im not always the best at explaining my thoughts.

i would suggest finding a small turbo that will reach your peak power goals and do every mod you can to make that turbo spool earlier. also, e85 seems to produce decent tq over pump gas. even with my stock 2.2l s10 flex fuel, i notice a small increase of power when i use e85.
not to get off topic(i think its kinda on topic) but sense e85 used more fuel, wouldnt a turbo spool quicker because there is more exhaust gases coming out? i know it would be a small increase but 200-300 rpms worth maybe? just a thought.

i know when your designing an N/A header and exhaust for power, you need to take in the account of fuel used.(e85 or gas)
 

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Does anyone have a chart of an ecu tune on a 9000 Aero with its stock 6cm/15t turbo? I'd be curious to see how that turbo - without the 18/19t conversion - spools and holds torque towards 6K rpm on a 2.3 liter.
off the shelf, aggressive stage 4. nothing more than a turbo back exhaust. if you run a stock turbo (read small) you will have to spike it to make power end of story. if you want flat torque on a small inline 4 you need to run a large turbo at low very efficient boost levels than can be held from peak load to redline. but you wont be hapy with the spool time on that turbo.



 

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Discussion Starter · #14 ·
if you run a stock turbo (read small) you will have to spike it to make power end of story.
Thanks, saabkid, that is very helpful. So looking at that chart, for example, do you mean it's hard to set up a tune to just bring the torque up to 250-ish at 2700 rpm and hold it there over to 5300 rpm or so? (I know, you could ask why I want to leave power on the table, but my goal is more linear power.) Is there something about the small turbo itself that requires the midrange torque spike?

I found this dyno graph from Hirsch advertising what looks to be a very flat torque curve for a b235 w/ td04, but then again, it doesn't seem to be a real dyno chart.

http://www.hirsch-performance.ch/Content.aspx?path=/Products/Leistung/E280008281

And I don't know how you would get such a tune here in the US anyhow. I appreciate the help.
 

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I'm not sure why your goal is to spool much sooner than 2000rpm. Have you never attempted to floor your car with the stock turbo? Doesn't result in very much acceleration.
My goal with my set up was to get the most out of the car before going with another turbo, flash, etc. With porting of the factory charge piping and TB elbow, MBC @16 PSI, 2.5" FMIC, freer flowing exhaust, reworked air box, gutted cat, passenger and rear seat delete (for the time being) my T25 was boosting at 16 PSI from 1800 RPM's to 6200 (before the cat was gutted, it suffered after 5500). Acceleration was far ahead of stock and besting mid 13 sec cars, all with a high mileage T25. The OP wants a car to boost at 2k or presumably earlier, and wants torque through out the rev range. It's doable without sticking a big turbo on the car that see's full boost in the later RPM's.


Clipping the exhaust of a turbo the size of a 15T, 19T, is such a small tradeoff for the benefits it brings that it's negligible. I've got a pretty decent sized exhaust wheel you could say and I start seeing boost around 2500rpm, full spooled to 35psi if needed by 4000rpm. Whatever exhaust upgrade you throw at the TD04 will not bring it anywhere near those numbers.
Don't take this the wrong way, but numbers are just that. They don't mean much in real world driving. About a week before my T25 gave up and died, I bested an EVO X. Those cars have "bigger numbers" than me by far, as well as more weight obviously, but in a real world drive he lost on 2 attempts to best me. Here's a simpler question to drive the message home about "big numbers", are you running in the low 11's yet? Technically those numbers (4??HP) should equate to low 11's.


@OP, don't focus on the numbers so much. Trim the fat and get the turbo pushing air efficiently, and as cool as possible. Like Comtrang mentioned as a suggestion, I'm going the T28 route onto a T25 center section. They're popular upgrades with Hondas, Mazdas, as well as Saabs and should propel the car better. But sticking with a smaller exhaust wheel to get power happening earlier in the rev range. It might not make as big of numbers on the top end (which means you get to brag about the cars you beat, not the high dyno numbers). People miss the fact that torque early on wins races. Without it, you better hope you have a mile long track to let the [email protected] 4500rpm hopefully catch up to the guy who had the low end grunt.
 

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The turbo can only flow so much air at "x" rpm, while at the same time as rpm goes up the amount of air the engine takes in increases exponentially. A small turbo can not continue to meet the air wants of the engine and thus power/boost taper off.

As you push a smaller turbo harder and harder you effectively just wind up super heating the air and shooting yourself in the foot. A larger turbo at low boost can flow more air while generating less heat, but it will notspool fast with a higher MOI etc.
 

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i alway say its not about peak power, its about your average net power through your useable rpm range. you can slap a big turbo on a car and get 500 hp but if that hp comes at 5500 rpms and you have to shift at 6000 rpms, whats the piont? your back down to 3000 rpms, trying to build up the boost again. unless your gearing is set up for top end performance, your gonna have a lot of lag.

this might sound funny and little kiddish but on need for speed underground 2, i always beat my friends cause of how i tuned the engine for average power and not peak power like they did.
 

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Don't take this the wrong way, but numbers are just that. They don't mean much in real world driving. About a week before my T25 gave up and died, I bested an EVO X. Those cars have "bigger numbers" than me by far, as well as more weight obviously, but in a real world drive he lost on 2 attempts to best me. Here's a simpler question to drive the message home about "big numbers", are you running in the low 11's yet? Technically those numbers (4??HP) should equate to low 11's.


@OP, don't focus on the numbers so much. Trim the fat and get the turbo pushing air efficiently, and as cool as possible. Like Comtrang mentioned as a suggestion, I'm going the T28 route onto a T25 center section. They're popular upgrades with Hondas, Mazdas, as well as Saabs and should propel the car better. But sticking with a smaller exhaust wheel to get power happening earlier in the rev range. It might not make as big of numbers on the top end (which means you get to brag about the cars you beat, not the high dyno numbers). People miss the fact that torque early on wins races. Without it, you better hope you have a mile long track to let the [email protected] 4500rpm hopefully catch up to the guy who had the low end grunt.

:roll: :lol: I'm not getting into this one!!!

But here's my old vids, watch them then tell me a t25 car will stay with it...not on your nelly :lol:

Turn the volume down as the sounds crap. On vids 4 & 6 (gt30) you can see where the lag effects it in 3rd, foots buried here from 40ish but doesn't get going till 65/70. Keep it in 2nd though between 40-60 and it's just ballistic ;ol; Complete opposite with the gt28rs, floor it in 3rd at 40 and it's off like a rocket...car was very fast & incredibly responsive with that turbo.

Gt28rs

Gt3076r

I've been having fun with my 9-3 and its stage 1 tune t25...it's a nice quick car, not saying any different but up against a 340-360bhp t28/gt28rs/tdo4 18/19t car....no chance.
 

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this might sound funny and little kiddish but on need for speed underground 2, i always beat my friends cause of how i tuned the engine for average power and not peak power like they did.
I noticed that in other Race Sim games where they'd have accurate power bands. But yeah, you need the gearing and you need to stay at a higher speed to enjoy the bigger turbo.

At 16 PSI with the smaller turbo, it's not like trying to get 27 PSI out of it. I think 18 is OK but you start getting more heat in the 20's.
 

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:roll: :lol: I'm not getting into this one!!!

But here's my old vids, watch them then tell me a t25 car will stay with it...not on your nelly :lol:

Turn the volume down as the sounds crap. On vids 4 & 6 (gt30) you can see where the lag effects it in 3rd, foots buried here from 40ish but doesn't get going till 65/70. Keep it in 2nd though between 40-60 and it's just ballistic ;ol; Complete opposite with the gt28rs, floor it in 3rd at 40 and it's off like a rocket...car was very fast & incredibly responsive with that turbo.



I've been having fun with my 9-3 and its stage 1 tune t25...it's a nice quick car, not saying any different but up against a 340-360bhp t28/gt28rs/tdo4 18/19t car....no chance.
With the exception of the run where you started from a stop, those are all after the car was moving. The run where it was from a dead stop, it didn't do anything until around 50 MPH. Not knocking the car, but you'd loose in stop light fight. And to be honest since your comment was directed at me, I was running a stock tune, stock injectors, stock fuel pump, stock suspension, stock turbo. It was very balanced. And was just to prove that the car can be something with a near stock set up provided you pay attention to the little things. Once the T28 wheel is in, it'll get the proper upgrades.
 
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