You did it didn't you, fits up under there nicely. How much boost are you running? I'd be keeping mine below the point of needing an intercooler, around 8-9psi.

 

Unfortunatly this doesd hold water with the reality of these systems, plus it doent take into account the benefits of the drop in temp of the charge due to the piping being under the car, which makes up for any losses for thre same reason, as far as tubo lag, the two cars i have been with this set up had no noticable turbo lag though I will confess this was a set of the pants experience

Just another opinion


cheers


Tim

 

drop in temp charge....an intercooler does the same thing and probably more efficient than a length of tubing, intercooling does not make up for heat loss in front of the turbocharger, if it did you jsut invented a way to build a perpetuüm mobilé, instant nobel prize for you.

 

TT, I think you have an incurable bias, without a doubt a rear mount is a compromise.

 

I'm not talking about the rea mount, his statement is that cooling the charge air overcomes heat loss before the turbo, that means that he has a way to recoup energy by loosing energy, that's way over 100% efficiency.....THE ticket to a perpetuüm mobilé.

I have an incurable intolerance for marketing BS turning a disadvantage into an "advantage"

 

Would a supercharger get similar results without the heat?
Bernie

 

I didnt say it overcomes it, I just said it is a factor not mentioned and I also meant after the turbo. doent replace an intercooler either, but again just a factor to consider

 

I took it that one advantage offset another disadvantage, like getting a state tax refund that pays for the federal tax bill owed, a "wash" in accounting speak.

 

Sure, they don't require heat to operate, just a mechanical input.

 

The rear twin turbo set up can be debated ad nausium ofcourse, but the results are real speak for themselves... My buds at East Coast supercharger are a vendor of this set up and have been in the magazines,One set up I have personally seen produced 710RWHP in conjuction with a cam and intake swap . I think they even did a show on this on hot rod tv if you can call that a credible source.

Just keep in mind my only point was its an alterntive solution that does produce real results, and ill leave it at that


cheers



Tim

 

One of you guys take the plunge and we will see how it works. Wrap the hot side pipes with header wrap to contain some of the heat. Then we can meet at the 1,320 to flog 'em!

 

have you ever seen an intercooler BEFORE the turbo? When the turbine compresses the charge it heats up, only then can it be cooled with ambient air (since ambient air is now colder)

710 Hp with a turbo, when does it spool up and how much power would it have made w/ a front mount turbo? I mentioned the fidanza car on hotrod TV, it's on youtube..watch the vid and see them "rig" the dyno test right there.

"Would a supercharger get similar results without the heat?" in reference to what? rear mount or intercooling/using a long tube to cool the intake charge? Any sypercharger heats up the air, some more than others (non adiabatic ehat pump, known as roots is notorious for heating up the intake charge), it's simple thermodynamics

 

Bernie,
Superchargers use up power from the engine to provide more power, for a net increase. Turbochargers use waste heat that would otherwise be blown out of the exhaust and only take away power in that they cause some positive pressure on the exhaust side of the head, mostly it is just "free power." So turbos are usually more desireable, but in the case where packaging is a major concern, it'd probably be smarter to go to a supercharger, like you said, versus hiding a turbo under your gas tank. Centrifugal superchargers only have a fraction of the ducting that a turbo does. Nitrous is an option but isn't an always-on power adder (which is good/bad).

Without quantitative measures of what is lost from the extra piping it's hard to say if what you are losing is worth it but Monty said it all, those STS things go against every piece of common sense collected in the many decades of turbocharger use. Especially when there are more sensible (albeit less-lazy) options. Those who are saying, well there are results, you have to realize how utterly ugly the STS system is to someone with an engineering education. If you can be happy telling your friends "it's horribly designed but it does add some power", then by all means, spend away.

Oh and if having a red hot turbo (although less hot than it would be if it were in the proper place!) under your gas tank sounds like a good idea to you, check out the thread about the guy who's gas tank recently blew up in his face and consider the merits of becoming a cartwheeling-fireball.

-Chris

 

It does hold water. Given the same turbos, wastegates, BOV's, intercoolers, and I'll bet anyone that a near-engine turbo system will outperform the STS system in everyway other than ease of installation and underhood density.

Marketing != Physics

I've got nothing against the STS system, as I said in my original post it is relatively affordable, easy to install, and does produce good performance increases. I realize that not everyone has the patience, budget, or fabrications skills to design and construct a turbo system for themselves, nor do they want to undertake the challenge of packaging a system within the relatively tight confines of a Corvette engine compartment. It's not easy or cheap and that's why these kits exist.

I'm the first to acknowledge, from first hand design, construction, and application experience, that any reasonable turbo on a large displacement V8 will not have any noticeable turbo lag. The inherent torque generated by the displacement of the engine itself overcomes the turbine lag and the volume of exhaust energy is sufficient to spool the turbine up practically instantaneously on a modern, appropriately applied turbo. But the fact is that compared to a near-engine mounted turbo system, the long hot side tract from the exhaust valve to the turbine does result in heat energy losses,a nd the long cold side from teh compressor to the intake manifold represents a larger volume that must be compressed before positive manifold pressure (boost) is achieved. That's an indisputable fact and why the STS system uses undersized and lower A/R turbines. They are masking the heat energy loses by using a smaller turbine so that is will spoll the compressor up quicker, resulting in immediate increases in low end torque at the expense of rpm range and higher end power. This is certainly a desirable performance tradeoff for a street driven application, but a well-designed system can provide the same low end torque with an extended rpm range and increased power across the engine operating range.

I think the big difference between the advocates of the STS system and the people with applied turbo system design and construction such as Marck, myself, and others is due to expectations. My first twin turbo made 1200hp and 1000 tq on pumpgas at ~22-25 psi of boost, street driven. My current street car project will approach 1500 hp on pumpgas at ~25-30 psi of boost. It seems that most STS advocates are satisfied with power production at less than half that. In that application, the cost/value/performance is valid, but when you really start turning the wick up, you have to follow the proven rules of design and construction.

I cannot think of any other turbocharger application where the design is based upon the turbocharger being such a long distance from the exhaust port. Every other proven design, whether it be for automotive, aviation, diesel, marine, etc utilizes a near-engine turbo configuration in order to capture as much exhaust heat energy as possible in order to maximize efficiency. You can debate turbocharger system design and theory all you want, but look at how every other OEM or aftermarket turbo system except the STS is configured, you'll notice more simlarities than not, and there's a reason for that.

 

Monty, do you know how to size a turbine housing to account for a rear mount setup, or where I could get this info? I doubt I'll get much help from TT since I give him so much flak.

1500hp on the street, whew, that should probably be outlawed, but until then...

 

You doubted wrong.....

If you know or have an estimate of the heat loss you can calculate what size turbine would be best for your setup. It's a calculation that almost anyone can do, just buy a good book on turbocharging and there'll be a detailed write up of turbine and compressor sizing.

 

If I could get some headers for under 200 dollars I'd do a TT in heartbeat

I would have to use GN turbos untill I get better ones. I would be limited around 5500-6000 redline

Edit: I actually only need one more gm log manifold That will fit correctly

 

The turbo systems I've built, designed, and helped design/build have all been conventional near-engine configurations, so I don't have any first hand experience with designing and building a rear mount setup. If I were going to, I'd look at what STS is using since they have the most experience with this configuration and adjust from there based upon engine displacement and desired boost rpm range. Otherwise a starting point might be to figure out what the appropriate turbine housing would be for a conventional turbo system and go one size smaller for the rear mount system, i.e. if a conventional application dictated a .81 A/R housing, you might want to go with a .68 A/R.

Conversely, if STS is using a .68 A/R turbine housing to ensure quick spooling on a 350 ci engine, you'd want to consider using a larger turbine on a 427ci engine otherwise you'd run out of engine rpm rnage due to the turbine/compressor overspeeding at too low of an rpm.

That's probably a pretty weak answer, but I'd rather be honest with you than lead you in the wrong direction. I don't like to give advice about something that I haven't already done myself.

 

Well thanks anyway guys, I'm still in the toying stage of it, I haven't made up my mind to actually do it. I think my current configuration is good for around 550hp at the crank, I could add a shot of nitrous and get pretty close to the 750 mark with a fraction of the effort. I do miss the dentist drill whine of a turbo spooling up though, and the cool factor.

 

So how much better is a conventional (in engine bay) TT setup over, something like a Vortech blow through kit? It would also be nice to see some comparative hp/tq curve information between the conventional TT setup and the STS setup. Probably no one has done this yet I am guessing?

I'm already thinking about upgrading my not as yet, but ordered, 427 sbc (550-600 hp) to a centrifugal blower setup, but I will have the wrong compression at 10.5:1. How much boost could I run with an EFI controlled 10.5:1 compression 427 sbc and how much power could that possibly add?