GT Motorsports: 370Z Supercharger system development

roplusbee

With those thoughts in mind, the Centrifugal SC setup should cost less than the Roots SC and TT setups. Especially if the "spool time" is relatively similar on the Centrifugal SC and the TT setups. I would say Roots SCs have a different application (like as close to direct response as possible) as compaired to the other 2 options. I could be off in left field, but that is not how the ball bounces though. I have seen a few Mustang guys get Roots SC systems with everything necessary to make a beast for a few grand. Although their suspension setup sux big time (barring the latest models).

I have stayed away from SCs because I have always run higher revving 4-bangers and I do my best to stay in the sweet spot (in boost) so that I maintain that instant throw-you-back-in-the-seat response. I guess having a 6 cylinder is lilke having a jack of all trades kind of deal.

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Solus

Kevtex... I have read your posts and for the most part agree with all of them except this one. The power requirement is not the same to get it from a belt as it is from the exhaust. When you take it from the belt you will suffer a larger power requirement due to the parasitic loss etc and you are taking power to make power. Gaining it off of exhaust gasses doesn't cost anything. The engine is shooting out the exhaust gasses whether the turbos are there or not so you are not taking any power from your engine to make the extra power (boost).

RCZ

^ There is more back pressure with a turbo than without one therefore you are taking some power away. The parasitic losses from a turbo are negligible when compared to the losses from a supercharger though. The SC takes a much much bigger toll on power than the tc.

KEVTEX

With a turbo, the engine has to work harder to get the exhaust out because of the increased back pressure the turbo provides. The same amount of extra work is required if you take the power from a crank pulley.

dlmartin81

Haha...sorry...I wasn't really asking you were did you find the pic, but rather, where does someone find such a huge safety pin.

Solus

I have to disagree with you on that one kev... just my personal stance doing more research right now to provide valid documented points.

Silo

Here you go: Why bigger turbos make more HP at the same PSI.... - Page 3 - RX7Club.com

RCZ

Not at all because the sc has to move gearing and a belt while the tc only has to spin. We aren't arguing for the sake of argument, we know this is and has always been the case. In modern days, parasitic losses from the sc have been greatly reduced through new designs, but its still takes a bigger toll on the engine to make the power.


Also, guys, the whole bigger turbo makes more power thing.... From what I understand its not because it flows more, we know that 5psi is 5psi. What matters is the charge density of that 5psi. According to what Silo posted, a turbo that is in its peak efficiency zone (or island if you've ever seen a turbo flow chart) will create a more dense 5psi than one that is not. Think of it this way... colder air is denser, air particles are more compact therefore there is more oxygen to burn therefore you make more power. The same apparently goes for a turbo operating at peak efficiency vs one that isnt. The one operating at peak eff. somehow produces a more dense charge (at the same temperature) as the one that is out of its efficiency zone.

The post by silo didnt explain why, but I have a feeling it has something to do with how the air is compressed in a more efficiently sized tc than a less efficiently sized one. Efficiency relating to the size of the engine and the amount of psi you are targeting.

I'll do some more research and let you guys know.

Silo

And the parasitic loses of a s/c are always way higher then the losses due to backpressure increase by a turbo. Don't forget that otherwise wasted engery (in form of heat) is used to drive the turbo. The overall efficiency of a turbo is higher than that of a s/c which doesnt mean that I would roule out a s/c - I even prefer it since you can reach a certain amount of gain with less cost and less labour and with less parts (less parts = less possible source of trouble).,

Having said that, a birdy told me there will be a press release later today...

Solus

O.o

StillenZ

Hope that birdy wasn't kiddin....

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RCZ

Alright so after reading a bit from reputable sources. AKA Garrett from the stuff that Silo showed us.

Bigger turbos make more power per the same psi for two main reasons:

1) Bigger turbo will put less heat into the air and therefore the air is denser. More air = more power

2) The actual CFM of the turbo is meaningless. What matters is how much of that air is actually going into the engine and being used. There are restrictions that keep all the air from getting to the combustion chamber, the main one being backpressure from the exhaust housing of the turbo. The smaller it is the more backpressure, the less air that can flow through the engine, the less air that can flow INTO it in the first place and therefore less power. So bigger exhaust housing means less backpressure, meaning more air in, meaning more power.

The logic seems to be that it doesnt matter if the turbo can flow an infinite cfm, if the engine can't make use of it. The less backpressure, the more the engine can use, the more power it can make.

So how does this all apply to the SC vs TC dilemma?

I would say its the same thing, more flow through the engine means more power. So why do manufacturers recommend sticking with 2.5" piping rather than 3" piping on an SC? Because the sc doesnt flow enough in the first place to cause a 2.5" exhaust to become an obstruction??

Silo

That was my point. A larger turbo, and i have to state more specific, at a given psi might be more efficient, which means will it heat the charge less, hence more oxygen in that charge.

One simple factor is that it has to "shovel" less. You have a larger shovel you will dig that whole more efficiently than with a spoon. The other factor might be that the exhaust side is larger and therefore pumping loss is reduced. The larger turbo might still be less efficient at a lower psi but usually we compare the peak operating psi range.

KEVTEX

Yes, we know sc's have higher internal parasitic losses than turbo's. The majority of the power drawn from the engine is used to to compress the air, not toovercome parasitic losses.
None of this discussion should have any impact on one's decision to buy a GTM supercharger. I've had a turbo before and would prefer the torque curve provided by a a supercharger for a daily driver.

Buddy Revell

But if the turbo is sized just right, the midrange torque is really good. I had a turbo kit on my old Toyota Celica, and the response was very quick. That also looks like the case for the TT kits available for the 370, judging from the dynos of those TT systems.