Grant B

The gas temp. is lower, which lowers the velocity. When temperature changes inside a pipe, the velocity changes in proportion to it. Kinetic energy is proportional to velocity squared, so you are loosing a significant amount of energy. If temp goes down, static pressure goes up, and dynamic pressure (kinetic energy) goes down.

I'd imagine the pistons are doing more of the work themselves, pushing against the higher static pressure in the exhaust manifold. So it would be more like a supercharger in that sense. Certainly less of the energy pulse generated at blowdown reaches the turbine, so its more of a constant-pressure system as opposed to a pulse system. From what I understand, constant pressure systems usually include smaller turbines. Supposedly they are more effecient, but this is offset by the lower amount of energy available to the turbine.

Don't some STS kits come with a T04B 60-1 compressor? IMO this is waaaaay too small. Hell 60-1s were a bit too small for 3.0L Supra motors.

IMO, YMMV.

TurboBerserker

iTrader: (1)

More efficient turbine offsetting a lower amount of kinetic energy (and vice versa). Hmm... Sounds like if you designed your system with that in mind, that maybe your close-to-constant pressure system could actually net little or no loss of efficiency over a 'conventional' kit.

Maybe we should have read on to chapter three or switched text books and thought a little outside the 'conventional' box.

Isn't it just as funny as the only people bashing the kit are people who don't own one, have never ridden in one, and haven't actually thought it out, or are direct competitors?

Just do a search on STS and see who complains about it.

hellbents10

iTrader: (10)

I don't see how you could actually debate this. A convetional system will yeild a better result. Its like debating weather or not a heavy vehicle can beat a light vehicle in a race if they have the same powertrain. Then stating, if we were racing down a big enough hill.........

TurboBerserker

iTrader: (1)

One thing I learned teaching college: You can show someone fact after fact, theory after theory, but if they don't want to see, they will continue to spout whatever they want to believe. (and yes, this cuts both ways)

Actually TJ, the your analogy would be better if it were debating whether a heavy vehicle can beat a light vehicle with the same powertrain -- oh and we forgot to mention that by same powertrain we mean the light vehicle will have a 6.7L while the heavy vehicle is a 5.3L.

Let's see this comparo of a front mount with the same size turbo as an STS. Show me the front mount GT67 GTOs running 10s. Or the front mount z71s with intercooled GT35s running 12.3s. Oh wait.. we can't do that, can we? We have to go back to arguing about thermodynamics dont we LOL

I guess I have to beat Parish despite his bigger turbo, eh? Everyone start holding your breath!!

Grant B

According to "Automotive Supercharing and Turbocharging Systems" by John Humphries, the pulse system provides more energy to the turbine even with a lower effeciency. This is why it is used more widely. He says a pulse system is less effecient because the exhaust pressure varies so wildly between pulses.

Tons of aftermarket parts have compromises due to packaging. I don't see why this is any different?? Its just a trade-off, that doesn't mean it won't make good power.

People use a single T04R 67/84mm compressor on 6L engines? Man, thats a mid-sized turbo on a stock 3.0L Supra engine, which probably flows half as much air as a LS2, even with DOHCs.

To the guy who said "PRESSURE PRESSURE...",
http://www.grc.nasa.gov/WWW/K-12/airplane/dynpress.html
Notice the formula for dynamic pressure is density * velocity^2 / 2. So you need a big increase in pressure to make up for a loss of velocity.

tannji,
Your forgetting that heat=velocity in a pipe. As heat energy decreases, the dynamic pressure lowers. Heat is desired, it wasn't just "unavaoidable".

Face it guys, 2-valve pushrod motors are less effecient, therefore they won't run fast. Rear-mount turbos are even worse. Put them both together and you'll be lucky to run a 14

TurboBerserker

iTrader: (1)

True. "efficient" is a grossly overloaded term in this discussion. I think we've talked about 3 kinds of effciency so far.

Humphries argument boils down to front mounts make more energy despite being less efficient. So the argument is the amount of peak power in pulse based design is higher that the peak power in a constant pressure design. True. But the power from a constant pressure system does not drop between pulses, so how does the average power compare? Bet the same argument doesn't apply there...

Exactly. And it doesn't mean that the difference is more than neglible either.

I had a GT67 on my 6.0L. It made tons of power. But then again, I started with twice the ci as a Supra and didn't have to run 230mph in the 1/4 at 13.5 ETs

hellbents10

iTrader: (10)

I am not holding my breath for record shattering 1/4 times. Just don't see a rear mount going 9's, 8's, or 7's for a reason.

Boostaholic

iTrader: (4)

My question is why would anyone in their right mind spend money on a STS kit when a traditional mount setup can be had for less with no relocation issues.

F8L Z71

Again, this has been answed a 100 times also.

Phamspeed JUST came out with their ultra cheap kit. Prior to them everyone was MUCH more expensive than STS. Also for those worried about SMOG, STS is close to getting certified and even if they don't it is VERY easy to remove the turbo and go back to stock to smog.

We wont gho into how many front mount companies go out of business and you are stuck with cracked manifolds and such. That's why I'd be looking into people like PTK for front mounts.

Boostaholic

iTrader: (4)

Not like you can't pay some more and get tublar headers from PS, and its also not like there aren't machine shops all over that could fix a problem with tublar headers for a reasonable price. You do have a point though, lots of turbo companies go under, long as PS doesn't screw people over they should do good.

ktmrider

Yup. Us Dodge folks had exactly ONE choice. We still don't have any other turbo options but now do have a supercharger ( Paxton, GSM ). The GM truck folks are still waiting to see the setup Parish8 has in production.

hellbents10
TECH Enthusiast Join Date: Mar 2004
Posts: 578

I am not holding my breath for record shattering 1/4 times. Just don't see a rear mount going 9's, 8's, or 7's for a reason.

Very good point, and I fully agree with ya. Unlike some of the 2Fast 2Furious folks who think a fart can and graphics will make them 1/4 mile gods I never expect to have my 5300# ECSB pickup running those kind of times. A second or two improvement and keeping up with the F-bodies and Mustangs is plenty for me....

Boostaholic

iTrader: (4)

Dodge people DO have other options, getting a crosspipe and other hot parts fabricated for most vehicles will not cost that much, then its just standard turbo stuff.

ktmrider

Ya, we told ourselves this at first until the f***king computer keeps shutting us down. Plus the fact we have suspect pistons that are rumored to chip/crack ring lands and crowns at boost levels over 10psi.
Way to go DC, it really makes me miss my Silverado.....

TurboBerserker

iTrader: (1)

That's because it isn't an all out race kit. Neither is the cheap Phamspeed kit or the LM kit or the base PTK. It takes a lot more than a street front mount kit to go 9s, 8s, and 7s It takes a lot more the internet thermodynamics too

TurboBerserker

iTrader: (1)

And BTW -- you have STS to thank for the cheaper turbo kits. They proved the market is very viable, they proved you **CAN** get great performance from a $3500 kit, and they created HUGE competition for the conventional crowd.

Without STS, you'd all still be looking for $7500 turbo kits.

427

iTrader: (3)

Erik,
If we could get our two trucks together it would be a good compare. Mine has stock ex manifolds also, but the turbo is up front. Right now it has a 67mm Garrett on it. My best ET is still 12.23 @ 113 mph. At about 5500#.
Would be interesting to try drag racing from dead idle with both and maybe 40 to 80 mph punch to see how the different systems react. Currently when I drag race I brake torque to 2000rpm at about 5 psi and launch. I tried 10+ PSI launches but my trans said no to those! Currently the truck is apart with broken trans again (front pump). Looks like it may end up with the 80e in it this time.

Kurt

1999 SS

iTrader: (3)

i like the STS kit because i can get it installed with the upgraded turbo and methenol injection for just over $4600 and because no tubing runs under the front k-member and i dont have to relocate any accesories.. i have other reasons but those three really make up my mind on it. plus isnt the ptk kit sold without the actual turbo?

TurboBerserker

iTrader: (1)

That would have been very cool if we were a bit closer -- but now I have a 408 and a GT70 I also have no tranny in the truck so right now looks like we'd be dead even Man -- keep me up to date on your 80e progress. Of course, I might have to steal that little NVG part from you Depending on what broke this time, I might be headed for an FLP 80e.

I'm trying to get up in your neck of the woods in July. If I can make I will definitely side trip to meet up and break more tranny parts

JZ 97 SS 1500

iTrader: (2)

No PTK's system is offered complete with a T70 and the non-ic kit is $4499. And you don't lose anything with our kit and we route it between the K-member and the engine, so the downpipe doesn't drag the ground. Also with the current $400 off discount the kits are $4199 complete.

Jose

FLeXNuTZ

I don't see why people are getting all geeked up over efficiency here. 600+rwhp is a helluva lot any way you slice it. If you can get that much out of a cheaper kit, whether front or rear mount, why not do it? Honestly, I could care less about efficiency as long as my STS system could be set up with enough power to make a Viper look slow. Just a simple man's perspective, I guess. I've ridden in a stock C5 that had, what, 310 rwhp give or take a few so I can only imagine how double that would feel. I bet I'd feel like a God of the streets with that much power, lol.