How much horsepower and torque can be wrung out of the stock turbo? - Subaru Forester Owners Forum
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post #1 of 37 (permalink) Old 05-07-2006, 06:25 AM Thread Starter
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Question How much horsepower and torque can be wrung out of the stock turbo?

How much horsepower and torque can be wrung out of the stock turbo (TD04)?
I figure TBE, up pipe, Intercooler, Cold Air intake, custom tune. Anyone do I dyno with such mods? Silke? Peaty?

COBB Stage 2 etc.
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post #2 of 37 (permalink) Old 05-07-2006, 09:21 AM
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In Subed's case: stock TD04, stock TMIC, short ram intake, 3"TBE, Vishnu dyno tune; came out to 198 whp on his heartbreaker Dyno Dynamics dyno (for comparison, stock STi's usually dyno at ~215 whp on this one). Shiv also left quite a bit of power on the table to provide a reasonably wide margin of safety.

On i-speed/Crawford's Dynapack dyno: 220 whp, 300 torque :think:

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04 FXT PP PSM ~ "Subed"
98 Forester S ~ "Slynki"
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post #3 of 37 (permalink) Old 05-07-2006, 02:22 PM Thread Starter
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Quote:
Originally Posted by pleiad7
In Subed's case: stock TD04, stock TMIC, short ram intake, 3"TBE, Vishnu dyno tune; came out to 198 whp on his heartbreaker Dyno Dynamics dyno (for comparison, stock STi's usually dyno at ~215 whp on this one). Shiv also left quite a bit of power on the table to provide a reasonably wide margin of safety.

On i-speed/Crawford's Dynapack dyno: 220 whp, 300 torque :think:
Hmmm, 300 (STi) minus 215 is 85. 85 plus 198 equals 283. So it may be doing 283 at the crank.

COBB Stage 2 etc.
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post #4 of 37 (permalink) Old 05-08-2006, 10:03 AM Thread Starter
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Wait a minute; I forgot. Don't you have an automatic?

COBB Stage 2 etc.
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post #5 of 37 (permalink) Old 05-08-2006, 10:05 AM
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Quote:
Originally Posted by Pastor Spomer
Wait a minute; I forgot. Don't you have an automatic?
Yep.

-Silke
04 FXT PP PSM ~ "Subed"
98 Forester S ~ "Slynki"
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post #6 of 37 (permalink) Old 05-08-2006, 12:22 PM
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Silke, how much boost are you running?

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post #7 of 37 (permalink) Old 05-08-2006, 12:32 PM
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16.5 psi max. boost.

-Silke
04 FXT PP PSM ~ "Subed"
98 Forester S ~ "Slynki"
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post #8 of 37 (permalink) Old 05-08-2006, 12:44 PM
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OK, thanks, I am right there too.

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post #9 of 37 (permalink) Old 05-08-2006, 12:57 PM
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http://www.subaruforester.org/vbulle...67&postcount=7

@ the wheels: 210 hp/230ft-lbs. @ ~12.5psi on vishnu dyno dynamics.

TD04, DP/UP, pulley, ecutek by Shiv, stock everything else engine-wise. Same here, still a very mild tune for safety as u can see boost is kept pretty low.

MY04FXT5MT.jbp.w/stuff
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post #10 of 37 (permalink) Old 05-08-2006, 01:04 PM
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Quote:
Originally Posted by ant927
http://www.subaruforester.org/vbulle...67&postcount=7

@ the wheels: 210 hp/230ft-lbs. @ ~12.5psi on vishnu dyno dynamics.

TD04, DP/UP, pulley, ecutek by Shiv, stock everything else engine-wise. Same here, still a very mild tune for safety as u can see boost is kept pretty low.
If you add headers, full 3" TBE, walboro fuel pump, larger injectors you will probably see roughly ~230 max WHP w/ a max tune which I wouldn't recommend. If you want high horsepower, go w/ a bigger turbo that can do it more efficiently and cooler.
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post #11 of 37 (permalink) Old 05-08-2006, 01:11 PM
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Quote:
Originally Posted by sirwilliam
If you add headers, full 3" TBE, walboro fuel pump, larger injectors you will probably see roughly ~230 max WHP w/ a max tune which I wouldn't recommend. If you want high horsepower, go w/ a bigger turbo that can do it more efficiently and cooler.
Yea, not sure what route I want to take yet.

I now have a USMD STI tmic and walboro FP (was expecting a bigger turbo this year) and Gruppe-s v.2 headers WITHIOUT extra tuning YET!

Going to swap out my headers and go with some STI p&p&c headers and looking for a quiet 3in CB to complete the TBE, maybe back for a safe tune OR might wait until I get (if I ever get) a bigger snail. (VF preferably so I can use stock injectors).

Not really looking for high numbers since I'm onyl street driving, I'm pretty happy right now, maybe smooth out the curve and shift it to the left a little...

MY04FXT5MT.jbp.w/stuff
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post #12 of 37 (permalink) Old 05-08-2006, 03:26 PM
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Quote:
Originally Posted by Pastor Spomer
Hmmm, 300 (STi) minus 215 is 85. 85 plus 198 equals 283. So it may be doing 283 at the crank.
Ok, I've seen you do this a few times in different posts.

As I understand it, to rouphly correlate power on the same dyno between two cars, you need to calculate the difference as a percentage. To find that percentages, you divide the the whp measured by the dyno by the advertised crank hp. Using the numbers from the STi mentioned as an example gives you:

measure whp/advertised chp (STi)= %

215 whp (STi)/300 chp=71.66666%

manipulate that same equation using the numbers for the XT.

XT whp/% = XT chp
198 whp/71.66666% =276.28 chp.

04 XT
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post #13 of 37 (permalink) Old 05-08-2006, 04:25 PM Thread Starter
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But wouldn’t the amount of power used by a drive train remain constant?
Let’s say an hypothetical car has 300 crank hp and 200 at the wheels. This would be a 33% loss. Then the owner hops up the car to 600 hp, with the same percent of loss he would get 400 at the wheels. This would mean that a drive train that would take up 100 hp before is now taking up 200 hp. Why would the drive train be anymore difficult to move?
I’m just guessing, of course, because I don’t know anything about engineering. A while ago I came across this article by Shiv Pathak, and although I’ve become a COBB user, I thought that it was interesting.

“Originally Posted by Vishnutuning
Horsepower Claims: The Good, The Bad and the Confusing
By Shiv S. Pathak

You hear it everywhere. Horsepower claims. Along with their sheer ubiquity comes a whole lot of confusion. You see, horsepower claims, by judged by themselves, are nearly impossible to quantify. Let alone compare amongst themselves. Here's why…

Virtually all dyno testing done by aftermarket tuning houses are done on something known as a "chassis dynamometer." As the name implies, the entire car is parked on the dyno apparatus where its wheels sit upon big rollers. When the wheels spin, so do these big rollers. The dyno computer monitors the force at which these rollers spin to determine horsepower. Sounds simple, doesn't it?

Problem is that these numbers represent wheel horsepower, not engine horsepower which is what most people assume when playing the horsepower game. After all, we all know how much engine horsepower our stock car makes by just looking at the manufacturer's claims. But wheel horsepower is something all together very different. It does not take into account frictional losses caused by the drivetrain. That's right. The transmission, differentials, axle joints, etc., suck up their fair share of horsepower. As you can imagine, a car's wheel horsepower is always lower than its engine horsepower.

So how do aftermarket tuners make engine horsepower claims if they only have wheel horsepower dyno results to go off of? Simple. They take an educated guess. Now here's where things get tricky. Not everyone guesses the same way. Don't ask us why. If it were up to us, there would be standard guessing procedures. But until that happens (don't hold your breathe), customers need to know what they are getting.

But first, let's look at a totally hypothetical example. In our make-believe world, a stock Pontiac Firechicken makes 100 horsepower on the Supa Fresh Chassis Dyno. According to Pontiac, the engine is rated at 135 horsepower. Assuming this to be true, we can safely say that 35 horsepower is used to spin the drivetrain. But now let's say we put on our tuning hats and bolt on a big fat turbocharger. While we're at it, let's stick on an intercooler, bigger injectors, a stand-alone engine management system, a full exhaust and a pair of fuzzy dice. All of a sudden, the car is spinning the dyno rollers with 200 wheel horsepower. That's one fast Firechicken! But the question remains: How much power is the Firechicken's engine making? Now comes the time when we place our bets and make our guesses.

One of the more popular guesses is to assume that the Firechicken, which doubled its wheel horsepower, has also doubled its engine horsepower. Sounds reasonable, doesn't it? Ladies and Gentlemen, we now have a 270 horsepower Firechicken.

Not so fast buck-o,

Take a look at the new driveline loss figure. Yep, it went from just 35 horsepower to a whopping 70 horsepower. Does this sound reasonable to you? It may to some people. Others, however, may balk at this is say that doubling the wheel output shouldn't double the driveline loss figure. After all, why should the driveline suddenly need twice as much power to spin it? Sure, the extra power will generate more heat. But an extra 35 horsepower of heat is enough to warm a small Eskimo Village. Where did all that heat go? Good question. No one knows. This brings us to the other, more conservative, guessing technique which assumes that the driveline loss figure of 35 wheel horsepower is going to remain constant regardless of horsepower output. Assuming this is the case, we simply add the 100 wheel hp gains on top of the 135 engine horsepower and come up with 235 engine horsepower.

In summary, the optimistic guess yields 270 engine horsepower.
While the more conservative guess yields 235 engine horsepower.

Which is right? Neither, of course! If either guessing technique were 100% correct, the other wouldn't be used by anyone, right? The truth of the matter probably lies somewhere between the two methods, only quantifiable with big equations with multiple variables. We'll leave that for the mathematicians and physicists who want to figure out who has the fastest Firechicken.

For consumers, it's far easier to ignore the whole engine horsepower thing and look only at wheel horsepower results. After all, isn't that what we're actually measuring?”

COBB Stage 2 etc.
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post #14 of 37 (permalink) Old 05-08-2006, 05:11 PM
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Pastor Spomer>> "But wouldn’t the amount of power used by a drive train remain constant? "



I always had a hard time with a "Constant" for drive train loss. I believe there will most definitley be a loss increase. The crank, drive shafts, and wheels are restrained by bearings so they only move in a desired direction. As you apply more rotational force (Torque), you are pushing harder on the restraints. The more you push against the restraints, the more power will be lost holding those pieces in place. That is the main reason why original parts tend to wear out quicker when you increase engine power.

Is it linear? I think not. Double horsepower will not make a car twice as fast. It’s the same with Audio power. It takes right around 7 times the power (amperage) to double the volume of music in home and car audio systems.

I know it helps sells parts and tuning services to say you will go from 240 hp to 300 if you buy this part or tune.

No biggie though, if you can feel the difference, then its money well spent.

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Last edited by keyser soze; 05-08-2006 at 06:45 PM.
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post #15 of 37 (permalink) Old 05-08-2006, 05:39 PM
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There are some interesting threads lately about pairing an EWG and other supporting mods with the td04 to get the most out of it.


Start here:
http://forums.nasioc.com/forums/show...1&postcount=58
and
http://forums.nasioc.com/forums/show...light=td04+ewg
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