Actually davenow, there's no way in hell a stock turbo will push 320 hp reliably.

Though Turbo XS claims the stage 2 puts out 303 hp, they're getting that number from a VERY liberal guesstimate method. FWIW, TXS uses a Dynapack dyno, which consistently reads less parasitic drag and therefore more hp than a Mustang dyno since the Dynapack hooks directly to the axels (shedding the rotational weight of the wheels gives you more hp on the dyno). Then on top of that, TXS uses a percentage formula to calculate driveline losses. This unfortunately isn't totally accurate, but is loved by aftermarket manufacturers because it leads itself to bigger hp @ the crank guesses. On a stock WRX about 60hp is lost in between the crank and the wheels. The most you can reliably push out of the stock turbo (and I'm talking WAY past stage two in both mods and price here: Larger TMIC, uppipe, lightened pulley, and headers) is 245whp, which I believe has only been done sans NO2 a few times in the entire country since the WRX has been out. Now, take 245whp and add the 60hp lost in the drivetrain and you get about 305hp at the crank, possibly 5 more due to some excess losses. IOW, no stock turbo can even flow enough air with a load of expensive (and somewhat unneccessary at this power level) supporting mods to hit 315hp, let alone 320.

Sorry, but you will need a larger (if only slightly larger like a VF24,28,29 or OEM upgrade) turbocharger to reach 320hp in a WRX reliably and consistantly without NO2. This will put you at about 250-255whp on a dyno. This group of turbos is capable of flowing a little more, but to go past 255whp you need fuel upgrades (injectors and pump). These turbos with some fuel upgrades will max out between 330 and 355 or so at the crank. So actually there are plenty of turbos out there that even with fuel mods won't get you 370 hp at the crank as that number is WAY above the "MINIMUM".

To answer you Hyper, a catless uppipe, good bellmouth or split gate style turboback exhuast with one hi-flow cat or no cat all tuned on a unichip with some form of boost control will practiacally max out the stock turbo. You'll end up with about 290hp at the crank with this. Call it 300 if it makes you feel better, but that's probably not correct. Hell, I'm at the power level I just described above and I tell everyone my WRX has "300 horsepower". It just sounds so much better than 290, right? LOL, good luck to your friend. Also, think about a lightened crank pulley, it will put more of the engine's power to the wheels by reducing drivetrain parasitic loss and feels great when the engine's off boost. Pretty cheap too, good bang for the buck mod.

 

are we talking 300whp cause that ain't happening reliably with a stock turbo! I know it's well possable to do crank hp with stock turbo but not whp.

huked on fonics wurks wunders....

=)~B

 

It's all in how you guess it...

I think we can agree that wheel hp matters since it's measureable, so lets start there when assessing whether or not a stock turbo can push 300 hp at the crank.

To ensure consistency, we'll use the dyno Shiv at Vishnu uses for the comparo since it tends to read the lowest of any dyno I've seen. Mustang dynos (I prefer these) tend to show slightly more hp than Shiv's and Dynapack dynos tend to show even more hp than the Mustangs.

Base maps for a brand new stock WRX (between 1 and 3k miles on it) are between 163 and 169 whp, with an average of about 167 whp. The engine alone, pulled from the car and running a flywheel dyno, sees between 224 and 231 hp with an average of 227 (hence the 227hp factory rating). Therefore, on average 60 hp is lost between the crank and the wheels. Here's the problem: convert that into a percentage and you get a 36% loss in the drivetrain from the factory. both TXS and Vishnu use this method to calculate crank hp SOLELY SO THEY CAN PLAY THE HORSEPOWER GAME - IOW, customer sees the same parts from vendor x make a CLAIMED 5 more hp than vendor y so the customer buys from vendor x.

Using percentage methods to calculate crank hp results in an inflated hp estimation, since the drivetrain does not magically need an equal amount of more hp to turn it than the extra hp the engine is now making. This method gets carried away and becomes obviously flawed at the bigger hp numbers, but it's easy to hide when the power gains are lower (IOW, using that formula would mean a WRX putting down 500whp on a dyno would actually be making 680 hp at the crank - there's no way the same drivetrain that required 60 hp to turn it stock know requires 180!) But this is how both TXS and Vishnu do their math, try it at their websites. TXS stage 2 whp=227, times 36%=309 crank hp, EXACTLY what they claim. Comparable parts from Vishnu is the stage 1, which (in prototype at least) makes between 221-226 whp, times 36%= 300-308 crank hp= their claim of 300-310 crank hp for stage 2.

That's how those manufacturers get their numbers, and as shown above it is off sometimes by quite a bit.

The other way is to apply the original drivetrain loss of 60 hp to the new whp number. This is a much more accurate and conservative number, not perfect but a lot closer. The guys at SPD Tuning and Cobb Tuning have some of the only experience in the country with actually pulling modified engines from Subarus and then flywheel dynoing them. They have found on every occasion that the loss observed between the flywheel measured when the engine was built and the wheel hp measured when it was dropped in the car was within 15hp of the original 60 hp loss figure. Yup, even a monster engine that was built up by Cobb flywheel dynoed at 537 hp and chassis dynoed at 463 whp. This is the most extreme case of variation that I am aware of, and it was still only 74 hp, only 14 from the stock 60 hp. This would say that the loss (especially in lower output motors, like say HALF that amount of whp) is closer to the original 60 hp figure, meaning the TXS and Vishnu stages acutally make closer to 287 and 281-286 hp at the crank, respectively.

 

TXS Stage 2, Vishnu Stage 1, and the Cobb Club-Spec Kit all dyno within 3 hp of the nice average of 225whp. This is about the max that can be wrung out of the stock turbo - you could certainly find a few more ponies in headers, larger intercoolers, and head porting, but for all practical (bolt on) purposes this is about the max of the stock turbo. In reality it is quiet a bit (15-25hp) short of the claims by TXS and Vishnu, but it is interesting to note that both Cobb and SPD call a kit that dynos at 220-225 whp a "280 hp motor". Also interesting to note is that 1/4 mile trap speed (this is actually a pretty good indicator of whp) is almost alway identical with similar drivers between cars equipped with the TXS stage 2 and the Cobb Club-Spec Kit. If the TXS is making 309 hp and the Cobb is making 280, there should be a considerable difference in trap speeds due to the 30 hp difference - but there isn't. The answer: the cars are putting out about the same hp at the crank, and it's somewhere between 280 and 290, not 310.

As for the limit of the stock turbo, as I said earlier the highest numbers ever reached on a properly calibrated chassis dyno are still only 240-245 whp, and the only stock turbo WRX's EVER to get into the 240's witout NO2 did so on the notoriously high reading Dynapack dynos. Even at the highest ever (well past TXS stage 2, Vishnu stage 1, or Cobb Club-Spec in both mods and price) stock turbo runs according to the 60 hp loss figure are acutally putting out only 305 hp. Give that figure even more benefit of the doubt - a 5 hp gain still puts it at 310 TOPS. Keep in mind these are rare cases, in actuallity 235 whp out of the stock turbo is excellent and at the upper end of it's airflow capabilities. This puts you at about 295 hp at the crank, still not even 300, let alone 320.

In short, the claims by Vishnu and TXS are just that: claims. They are elevated not out of malice but out of marketing neccessity, as you can obviously see. Cobb and SPD have similar products but much less market share than TXS and Vishnu, and I believe this shows the effect of higher claim marketing.

I stand by my statement: The stock turbo is dead after 300 hp. Due to the physical design of it and the laws of physics and thermodynamics there is no way it can support 320 hp without another power adder such as NO2. If you want a TRUE 320 hp and not a vendor's marketing claim, you will need a larger turbo.

Sorry for the double post rant, I'm just tired of hearing so many people claim they have some rediculous number like 330 hp on a stock turbo - it can't be done, not by a long shot. I don't want those who are new to the hobby to be misinformed.

Sorry Hyper, I'll give you back your thread now

 

personally, I'd skip the Cobb CAI. Because of their tendency to lean out the fuel mix too much, you would have to have a Unichip dyno tuned to run the CAI safetly. Also, I believe it's like $275 - NOT a good bang for the buck. You'll get a better gain out of a TB pulley, and they're on sale for only like 110 bucks now (can you tell what I'm doing when I get paid next...).

Best turbo - that's a difficult question. Again, I would make sure what turbo he has from the factory, it might be different (bigger) than the USDM's TD04.

After that, the VF29 is the best of the IHI bunch, and they can be had for about $800. BTW the VF24,28,29 are all almost the same turbo - they flow the same amount of peak hp and have the same lag. Their different designations are due to the order in which they were designed and refer to little things like improved cooling lines, not terribly important, but considering they all cost the same get the newest, the VF29. The Ion OEM upgrade is really nice, about the same lag as a VF24,28,29 (the least of the IHI series) but has the potential for 275 whp with fuel, intercooling, and tuning if you want to expand. But, it's $800 and you need to send them your turbo - a real pain in the neck.

If your friend has good access to finances, then the turbo to get is the SR30. This thing spools quicker than the VF24,28,29 and Cobb has had quite a few SR30 equiped WRXs put out over 290 whp with stuff like a FMIC and fuel upgrades. The SR30 has the spool of the smallest VF turbos with 95% of the power potential of the largest (and far laggier), the VF22. There are two choices of exhaust housing when you order one, a 15 and a 17. The 15 spools faster than a VF29 and will top out at 295 whp, the 17 spools slower than a 29 (about as fast as a VF30) but will peak at 310 whp. These are Garrett turbos with converted exhaust housings so as to be a bolt on for the WRX. Garrett turbos are the most efficient, reliable, and long lasting turbos for automobiles today, and they also produce a flatter and smoother torque curve than a Mitsu, IHI, or PE that flows the same amount of hp. All in all, this is the most awesome bolt on turbo you can buy for the WRX right now. It's priced accordingly: $1500 (yikes!)

So, for around $800 you can get a VF24,28,29 or have your stock turbo worked by Ion for about the same spool and more power potential. I think I'd skip the FP OEM upgrade, I've heard that the workmanship isn't exactly top-notch and it puts out more power than the VF24,28,29 it lags pretty noticably more and makes less power than the faster spooling Ion upgrade. The FP is only $600 though, and I've heard some good things (it's put plenty of WRXs in the 12s).

At almost double that $800 VF29 or Ion, you can get the SR30, the best of the best. It all depends on money, but if you can practically afford (justify?) the SR30, it's the best way to go.

Again, to get the most power out of any of these turbos you'll need the supporting mods discussed earlier.

Just my .02c, hope it helps.

 

this is also pointless

 

I agree with you BOP, the parasitic loss in the drivetrain is a ratio, but only up to a point. You reach a point where the drivetrain has absorbed all the hp it will need to turn at full speed at WOT. In this example, the drivetrain will suck up a percentage of power, the amount it needs to keep moving. But once the drivetrain has absorbed all the hp it needs to spin the wheels at full power, it will not magically need more. Therefore, at a certain point (about 60 hp on a WRX) it will take the same amount of power to spin the drivetrain almost regardless of how much crank hp you throw at it. This is demonstrated in Cobb and SPD's experiences as well as those of thousands of hot rodders over the past 6 or 7 decades (sorry I had to get that in, I came from the musclecar crowd). After a certain point, the drive train has absorbed all that it will need, any other losses are due to heat and other factors. Even Shiv agrees with this - see his article on his website under the Tech Articles section if you need further clarification. The problem I have with Shiv is that he goes on this whole explanation about how percentage based guessing isn't accurate and then he uses it anyway! Oh well, he's running a great business - more power to him.

Hyper, if all your friend wants is 300 crank hp than keep the stock turbo and just work everything else. He'll get close to that number, and it will be substantially cheaper. If he wants more than that, he'll need a bigger/reworked turbo.

 

this is also pointless