TurboBerserker

iTrader: (1)

There have been good track times and good '60 times. See Allen's post (FarmTruc).

I think P Mack is just trying to explain the actual science here. I, for one, appreciate that as I'd love to know the actual facts rather than the myth that gets bandied around so much.

I personally don't care if the STS works the best for race cars or not. It works the best for my street truck in Florida heat. I'm just interested in the real science here and could really care less about the people who don't really understand the science anyway.

Arkangel77

iTrader: (2)

I just wanted to ask this - DOES it matter? If I meet my goal with MY sts System why would I care if it could do more up front? I personally don't care. I am not going to argue the temperature formulas one way or the other. If you can chose a turbo that will give you what you want and mount it in the rear than what's the diff? AS it was previously said. Its just different ways to get to the same outcome. NOT wrong just different. IMHO - Lata, Ark

Wildman

P-Mack: No, I think you originally posted this for info, and I am all for that.
But this subject has been beat to death and the pot shots are just getting old.
Once a thread like this gets started, it goes down hill fast.
Most of what you say, I believe the STS owners agree with. But in the end, it is pressure that spins the turbo, granted that the hotter the gases would be more efficient.

JZ 97 SS 1500

iTrader: (2)

Like I have said before, I have both front mount customers and rear mount turbo customers. Give me a setup and enough info, I'll get it to go fast no matter if we have to mount the turbo in a trailer and haul it behind the car.

TurboBerserker

iTrader: (1)

Hey P Mack, If hotter exhaust means the change in temp is greater, does it follow that a cooler turbo might produce more power as well?

Also, what do you think about these statements (from STS' site) from a technical point of view:

"The velocity of exhaust gas and the fact that the STS design features a good deal of straight pipe, coupled with what exhaust gas does when it enters a turbo, should help negate any "lag" in the system."

"Denser exhaust gasses drive the turbo turbine wheel more efficiently."

[Being closer to the tail pipe] "Provides a better pressure differential across the turbine wheel which promotes better flow across turbine."

I also found something that says the remote mounted turbos are ~500 degrees cooler than front mounts.

Please don't think I'm trying to argue with you -- I really want to hear your opinions on this stuff. You're one of the few people who've actually tried to explain these things based on logic rather than religion

Hey Jose -- we'll need at 50 gallon drum of N20 on the trailor won't we?

MIGHTYMOUSE

iTrader: (59)

i was just kidding.. and i dropped a big bomb of a band-aid for you guys to use anyways.. try it.

TurboBerserker

iTrader: (1)

My GT67 has a .96 A/R. The reason I am confused by this is that I've spoken with two guys I trust very much (for very good reason) at STS and both told me the turbo was put together to their specs by a custom engineering house. I've seen a lot of other guys say their GT67 is a .86 (81??) A/R, and my kit was a prototype, so maybe my GT67 is a bit different, but I honestly believe there is some voodoo to do with the turbine and impeller wheels. Of course, the only turbos I have handy to look at are from STS.

I've had turbos before, but it was a many moons ago, and my memory for impeller wheels just isn't that specific

nitrorocket

iTrader: (12)

I think it's a good idea. In my book power alternatives are always welcome! Ultimatly, The rear turbo is a good idea for the average street strip car. Not gonna break any records, but it gives some extra horsepower. BUT....The pump for that kit must be pricey because that kit is a little steep for something that does not use stainless headers or have an intercooler. As prices come down and the bugs get worked out I am sure they will start selling like hotcakes! I do my own turbo setups and would have to say it should at least include an intercooler for that price. Just my .02

JZ 97 SS 1500

iTrader: (2)

I have had a pair of their GT67's here and it was nothing more then a garrett front side with p-trim exhaust...lol. Unless the customers were sending me other units. Heck to me the Master Power T70 will flat outpower the GT67 and spool the same. With the larger front side, p-trim exhaust and lightweight shaft you can't go wrong. If their is a "special" unit out there I have not seen it. Also if they are reducing the turbine exhaust size down, then they are getting into the old O-trim wheels and T350's. Lots of backpressure will rear its ugly head if you start running high boost.

Jose

TurboBerserker

iTrader: (1)

I could be mistaken, too, or confused about what I heard. Any thing I can look for on the GT67 I have sitting in my lap?

JZ 97 SS 1500

iTrader: (2)

Measure the impeller inducer and exducer. Then do the same on the exhaust side. Its easy to pull the covers off. Should be about 8 bolts or 6 bolts on the back of the compressor cover (dending on the compressor cover that is used). Just take them off...picture below

back of compressor cover



Then once you pull the compressor cover off it will look like this....

compressor wheels

Measure then the inducer and exducer

inducer and exducer

Inducer=DP
Exducer=DG

Do the same for both and call me or post the info up or email them to me. See if they match what I have documented. I have MUCHO turbo specs around that I don't post so always feel free to call or e-mail if you have any questions. You would be suprised how old some of these "new" turbos from some of the manufactures are when we cross-reference the #'s...lol...diesel turbo parts anyone??...lol.

Jose

MNC5

P Mack, If a windmill is a turbine (crude perhaps) and the wind is blowing at 20mph and the inlet side temp is 500 Rankine and the outlet side is 500 Ranking are you saying the windmill would turn faster if the outlet side was 450 Rankine leaving the inlet at 500 and the wind at 20mph? Or just produce more power

Are you saying it is the pressure differential created by the temp drop that is responsible?

Or are you saying its the temp drop caused by the pressure differential?

Because mass flow in equals the mass flow out, the exhaust takes up more volume due to increased moles of combustion products compared to reactants(Minor), and the exhaust is much hotter than the intake air(Major), and the exhaust process starts at higher pressure than the ambient pressure of the intake air.

P Mack

iTrader: (6)

No, I don't think you'd want to lose any heat from the hot section of the turbo if that's what your saying. I don't know if you're familiar with conservation of energy but it basically states that all the energy that goes into a system (in this case exhaust temp & velocity) has to equal the energy coming out (exhaust temp & velocity & work from the turbine). If you are losing energy due to heat transfer out of the casing, that is basically just energy that didn't go towards making the impeller spin. It would be possible to show that the heat lost from the gas in the turbine decreases its velocity, causing less of a pressure difference on the "pressure" and "vacuum" sides of each blade, but that's harder to visualize. Short answer: you want your temperature ratio to come from pressure ratio & high efficiency, not heat loss.

If you're talking about the cold side of the turbo, then yes, you want that to be as cool as possible.

P Mack

iTrader: (6)

Yes, that's exactly what I'm saying. Also keep in mind i'm talking about total temperature, which takes into account velocity. More on that later.

Exactly.

P Mack

iTrader: (6)

I keep using total pressure and total temperature in this post because they make stuff so much easier to understand, and that's what i'm used to also. "total" doesn't mean the same thing as "absolute".

The definition of a total property is the property a fluid would have when brought to a stop without losses. For example, when you hold your hand out of your window, the air is coming to a stop and you feel total pressure on your palm. Total temperature is a little harder to visualize but it's the same concept. Why does the SR-71 get so hot? It's not cause temperature of the atmosphere is hot, it's cause the total temperature is hot (from the plane's point of view).

This is makes this discussion easier because we don't have to keep track of pressure and velocity or temperature and velocity, just total pressure and total temperature. You lose total pressure from friction and heat addition (believe it or not). You lose total temperature from heat loss. You lose both when you take work out of the system, with a turbine for example. I guess i should call it an exducer here, but hey i'm a jet engine guy so i won't.

lilone

I am enjoying this post. Other than the random STS vs STS basher BS this is pretty good information.

vortec_7

iTrader: (2)

the laws of thermodynamics tell no lies. turbines can generate more energy from hotter gases up to a point. this is why in steam power plants they heat the steam several hundred degrees past the boiling point of water.

while getting the water to boil is all that is needed to provide the increase in volume associated with a phase change from liquid to gas, the higher energy gas (hotter) imparts some of that energy into the turbine wheel because the molecules of gas are moving faster and the pressure on the wheel will be higher as a result.

also interesting, the gas once on the other side of the turbine will be cooler, having turned some of its heat into mechanical energy spinning the turbine.

so in short, yes it is better to mount the turbos closer to the exhaust ports, as you will get a more efficient setup. i.e. make more boost at lower rpms.

on the other hand, if your goals are met by a rear mount turbo, more power to you. its especially nice if you dont have much room under the hood, or dont want to mess with hot parts for turbos. im not sure about the sts kit, but it might be less complicated to make a custom rear mount turbo setup than it would be to fab up turbo headers and all the other things you need for a turbo system under the hood.

billybob77036

I have not heard of one un-happy STS customer, and I am glad the system is working for them. I hope this system makes everybody happy that buys it, and makes big power.

...but...

Anybody who thinks heat plays no part in a turbo spooling up has not played with enough turbos to learn it yet. Coming from a high performance diesel background, making 80+psi with compound turbos, I can tell you for a fact that heat does help to spool a turbo.

This is a fact. Mount a pyro both pre and post and you will see AT LEAST a 300* drop post turbo many most cases I have seen. Sometimes up to 600* difference in less then 6 inches down the exhaust.

In defence of the rear-mount systems, if sized right, I think they CAN have simular results.

Zombie

iTrader: (2)

Don't you ever mention the O-trim wheel again! Evil POS. A t3 stage 5 out flows it. Your thoughts on the t70 are definately interesting, I wonder why they picked the 67 over the 70 if it's pretty much the same but makes more power. 70 is a pretty old wheel, seems like a lot of people buy newer designs not because they are better, but because they are not "old".

BTW, i've heard the GTS turbine wheel is just an old diesel wheel thats now being used on gas motors. Any truth to this or is it a new design?

tannji

How much of the temperature drop do you think is due to "conversion to mechanical energy" as opposed to the pressure drop on the open side of the turbo? The reason I ask, is that that is an awful big difference in temps, and if the STS system is putting out any appreciable percentage of the HP a conventional turbo system is, that would seem to indicate that while the conventional turbo is indeed slightly more efficient due to scavenging heat energy, the drop in temp doesnt have that big of an affect, assuming the appropriate hardware is used. I would think that BOTH systems see a huge drop in temps in the same 6 inches, as long as the turbo is in the middle of that 6 inches. Just curious.... (and I echo the sentiment that this thread has less flameage than is the norm....) Also, any comparisons of exhaust temps been done between the two sytems, after the turbo?