Jugador1

no...there's this thing called a wastegate. there is no problem with that plan.</P>

stang574

Wastegate? The wastegate has absolutely nothing to do with what i'm talking about. It's simple physics. The exhaust leaving the cylinder bank with the larger turbo is going to have to spin a larger turbine than the other. More thermal expasion force is going to be required to turn it. Therefore exhaust will not be exiting as fast as the other bank. And since the engine is a glorified air pump and the amount of spent gases leaving has a direct effect on the amount of power it creates, the cylinders feeding the larger turbo won't produce the same power as the other cylinders. Once again do to the differences in the exhaust leaving. It would be the same as running duals, but having on side completley free flowing and the other has a dual cats and a muffler. Different exhaust pressures as measured at the exhaust valve.

Jugador1

but after its spooled it shouldnt be as bad on backpressure, am i right? jeep...can u help me on this one?

jeep45238

You fail to realize that when the air is pumped into the motor, it does so through the intake manifold. Each engine bank will get an equal amount of boost and volume.

Not if you route the intake piping into the intake manifold, where each bank will get an equal amount of air and boost. Using a sequencial turbo set up like you're attempting to describe will actually divert the exhaust away from the smaller turbo and into the large one as RPM's and load allow, to make maximum power and least amount of lag.

You're also failing to see that a built Eclipse can't go very fast on a stock turbo, I'm betting money it's a larger than stock turbo.

With a turbo small enough to almost eliminate lag (2500 RPM full boost, ok?) you can make well over 500 horses and equal amounts of boost on a 302. T-3's are what I saw for this, but it was also an ongoing project that lasted around 5 years of engineering and fabrication.


Turbos can have plenty of low end torque/power and a lotta high end too. All in design.

The turbo sizing thing is like this: you can't have turbo lag with too small a turbo. But you can limit the power producing capabilities so much that it's not worth it.
Twin turbo's can easily make all the power you're talking about (large turbos and they would have turbo lag. It's not mandatory to cool the intake charge, but you can tune it and get so much more power out of it if you do.


The only blown and turbo'd car I've seen was an 80's T bird, Pro Street, dual blower, dual turbos. It didn't run very smooth and it took months to tune right, but it ran mid 8's. Definately something most people can't afford or design correctly.

That's called sequencial turbo set up. The ultimate, but extremely difficult to get right.

Jugador1

thanks for the backup! but surely it'd be easier than putting twins and a supercharger on and THEN getting it in an engine bay.

Tony Montana87

K Well i got lost at page 3 lol</P>


Summary:</P>


Turbo: pros- More HP (at low RPM or High RPM?) Easier to install? Cheaper? Come on guys back me up but cutt out the big words lol</P>


Turbo: Cons- Turbo Lag? But can be fixed. Dont know much about S/C or Turbo.</P>


SuperCharger : Pros- Ummmmm Not quite sure. No Lag?</P>


Supercharger : Cons- Ummmmmmmmm Like i said i dont know about this stuff.</P>

jeep45238

Turbo pros: more horsepower and more torque. all over the RPM range

Turbo cons: longer to install, more initial cost

Supercharger pros: cheaper and easier to install

Supercharger cons: Most are centrifugals, which require the motor to spool up to create boost......while a turbo could have been producing full boost for over 1000RPM.

stang574

The ONLY, ONLY way the two cylinder banks would make the same amount of power on this particular setup would be if the engine was running enough exhaust duration to completly remove all residual exhaust gases. This would allow the cylinders to equally take advatage of the forced induction. Also this motor would have to run no overlap to avoid the exhaust backpressure (which is normally greater than the induction pressure coming in from the intake valve) from staying in the cylinder. Most turbos run as little of overlap as possible but, regreatably have to run a slight amount due to limited crankshaft degrees available. AND after the turbine "spools up" the backpressure will get worse. As the exhaust leaves the port and begins building up pressure (which is initally needed to overcome the potential interia energy of the turbine) the turbine begins to spin. This percentage of exhaust leaving versus the turbine spinning will only get worse. As more exhuast leaves the port more pressure begins to build up at the turbine wheel. This allows the turbine to build up it's large speeds. It is this "trying to exit pressure" that drives the speed increase in the turbo. That is also why with two different turbine wheels and A/R ratios will create different exhaust pressures at the turbine (not refering the pressure after the turbine) You half to remember the pressure in the exhaust port from the exhaust valve tip to the turbine wheel (due to the laws of fluid dynamics) is going to stay as close to the same pressure as it possible can(because nature trys to equalize itself). And since each cylinder head is emptying its exhaust into different pressure enviroments it is HIGHLY unlikely that they will have the same cylinder exhaust leaving pressures and therfore their intake filling characteristics HAS to also be different. This will create the differences in power betweent the banks. I'm sure if we looked at the rpm increase after each cylinder fires we would see how one side is making more than the other. I know that the difference is probably not a great amount but it is inherently there. This may seem like a very **** thing to discuss and I agree it is. As I began looking at the sequencial turbo set up (about a year or so ago) I couldn't help but think of how these little details might of been overlooked or ruled out because the benefits overruled the negatives.
I have alot of respect for anyone who runs turbos or twin turbos. I just hope this will help show how what is on the market isn't always 100% correct. I also know how this can be very confusing if it is not thought about without being overly ****. Pleas excuse the long post and feel free to pick out anything you see incorrect.

jeep45238

NOOOOOT really......

You can never remove all residual exhaust gases without introducing overlap to blow intake air and knock out the exhaust, but you'll also loose the potential power gains doing it.

The reason being the only way to get a VE of 100% is to introduce metal-metal contact and make no room for any air.....which we all know is gonna f**k up the motor very quickly doing that.

Agreed most boosted motors, be it turbo or super run as little overlap as possible because they want to kep the boost inside the motor and not **** it out. But disagreed on the part of theexhaust backpressure being greater than the induction and keeping it inside of the cylinder. STRONGLY disagree.

The backpressure really isn't caused by a spooling turbo (they run off of the heat in the exhaust much more than the pressure of it). The bearings spin pretty freely.



Believe me, I don't care if it's very **** to discuss, it's in my nature. Looking forward to some debating and learning, hopeuflly for both of us.

Tony Montana87

So let me get thsi straight supercharger is more for like race tracks or is that turbo?</P>


Ok this is my case, say i get a mustang or a decide to upgrade my f150 i drive normal around city and i drive 80-90 on freeway. Sometimes i do go fast and i gun it just for the fun of it. In my case what is better? A supercharger for my truck is 4100 its a 97 F-150 ext. cab. And for my mustang i dont know because it will either b a 03+ possible a 05. What would be great for a old 69 Boss 429? or a 302? I know they use high HP i would love to drag with it, but i dont think the pssst pssst pssst sound would b great for a domestic engine liek that. Suggestions?</P>