I would say that's a fair and reasonable statement.

=======================

Because debate IS a learning tool?


If two people are arguing about different viewpoints, and they do not forget to listen to each other during the process, wouldn't that tend to refine the knowledge of both people?


Or am I asking too much of human nature...?

 

I agree that debate IS a learning tool when there is constructive input (ie EngineerMike). However, I don't believe emoticons or "I agree" statements are constructive. There are all kinds of people on this site... some contribute and others try to show off what they know or think they know.

 

eh... I don't worry about small stuff like that.

 

Group hug Overall this is my favorite website with the best input from real Camaro enthusiasts.

I think it is great that companies still think about the LT1 family. STS may not be for all but they may find a foothold.

I noticed that I didn't see a cat on the system. The negative would be that it is a restriction, the positive is that it would add heat. Perhaps the pictures that I'm looking at are too small on my tiny monitor.

 

Where can I see some pics, I didn't see any on the website and the ones on the previous posts expired-I guess! I can't see them either. Does this kit come with new exhaust piping from the manifold? In their picture only a small amount of piping is shown, making me think they intend for you to use the stock system

 

LOL I know, i know. it just gets really old seeing the EXACT same posts with the EXACT same WRONG argument. if you dont know, DONT POST.

as engineermike stated, massflow through a closed system(turbo/turbine) remains the same, however enthalpy goes down. Assuming you can take exhaust gas as an ideal gas(reasonable assumption) enthapy changes with (mainly) temperature. Less of a temp change across the turbine, the less power you gonna make.

 

Are you saying that the pressure between the head's exhaust ports and the turbo has NOTHING to do with how much boost you make on the other side?

 

if pressure goes up, given the same specific volume, temperature goes up, dude


Pv=RT


(any real engineers feel free to correct anything I inaccuratly state )

 

Boost is regulated by the wastegate. Essentially, the wastegate regulates the pressure upstream of the turbo in order to regulate turbine speed which determines boost pressure.

In a typical street turbo set up, exhaust backpressure (pressure between the exhaust port and the turbo) is around 2 X boost pressure. In an efficient race turbo set-up with a race exhaust and well-matched turbine, exhaust pressure can get as low as .8 X boost pressure. I did some thermo calc's one time as an experiment and found that the absolute minimum everything-perfect limit of exhaust backpressure is around .5 X boost pressure.

That being said, cooler exhaust gas will require a higher exhaust pressure to spin the turbine. The energy has to come from somewhere so if the exhaust is cool, it has to be at higher pressure. Therefore, the STS turbo's will likely have more than 2 X boost pressure as exhaust backpressure.

Mike

 

Uhhh.... yeah.


I think we're all going to have to cancel this argument...

I can't see anything that any of us actually disagree about.

 

Maybe I should simplify what I posted earlier.

The STS Turbo will create more exhaust backpressure per pound of boost than a conventional turbo set-up.

Mike

 

I try to respond to these threads because I have seen the cars run. I am sick of arguing. The cars run (both LT and LS versions). The numbers speak for themselves. They are on par with and in many cases eclipse the numbers put out by conventional systems, at usually about half the price.

LT1 @ 14psi 510hp /625ft-lbs

LS1: 416 rwhp and 452 rwtq at 5 psi boost

509 rwhp and 551 rwtq at 8 psi boost with methanol


Those are on stock, uncammed, unported, basically un prepped cars (LT1 has forged 8.7-1 pistons).

Cry about how sad all that is.

BBB

 

BBB... I read your thread here and on one in Florida. I think what they are saying is that the more backpressure in the exhaust, the more pressure is needed in the compressor... which makes it tougher on the engine.

But EngineerMike made an interesting point. With the pressure at nearly 2X, perhaps we are looking at this unconventional turbo with the traditionaly eyes. If more exhaust pressure is needed, then change the cam with a different profile than normal turbo cams. What if the exhaust duration was held longer to "help" build pressure in the exhaust versus the typical even split-type turbo cams.

If the exhaust pressure can build with more overlap, perhaps that would help with the backpressure concern... which wouldn't affect the load on the engine at 2X. Perhaps a 224/230 may be more suited for this set up...

Just a brainfart.

 

No. What I am saying is that an STS-style turbo will have more exhaust backpressure than conventional for the SAME amount of boost.

Building pressure in the exhaust is not hard to do. No cam changes required for that. Just force all the exhuast through a small hole (or turbine housing in this case). What is hard is pushing it out of the cylinder. So, with more backpressure, the crank is having to push the piston up against 30+ psi exhaust on the exhaust stroke, costing power. No change in cam timing will help this situation.

More overlap with higher backpressure? One problem here: If intake port pressure (boost) is 10 psi and exhaust port pressure (backpressure) is 30 psi, which direction will flow be if both valves are open? The 30 psi exhaust pressure will overcome the 10 psi boost pressure during overlap. This will dilute and heat the inlet charge causing lost power and increase chance of detonation.

You CAN modify the cam timing to HELP overcome the compromises in the turbo system, but it will only get back some of the power you could have had with the turbo near the engine.

For instance, I would delay intake valve opening (IVO) until 20 or so degrees ATDC (stock is around 13 degrees BTDC). This would allow the 30 psi remaining exhaust in the chamber to expand down to 10 psi before trying to push 10 psi air/fuel in.

Mike

 

Ok,
So what are we really talking here?

I've seen you (engineer mike) in the past put up some pretty long calculations. All Good stuff.

Now, If a race system has .8x and an "average" street setup has 2x but still makes X amount of hp, Then what is this guy doing? 2.2x, 2.5x, 3x????

I've seen some arguments from supercharger guys about backpressure in standard turbo setups......You put them to rest/pointing out with mathematical calculations that it was not more detrimental than the belt yankin on the crank.

How's about putting this to rest and calculating what can be done. NOT what can't.

So what if the system has a little more back pressure.

Oh, and the 224/230 cam doesn't need to have more overlap if you spread the lobe centers. Does it???

This is much to complex for my intelligence/education level but if those dyno #'s above are correct...............Some people are scared of loosing business/$$$$$$.

Just think of all the jokers that could hook up JY systems in their back yards. ME