Want to go Turbo. Have some???

fiveohwblow · Apr 3, 2012

Parasitic or drag loss from spinning the blower robs you of rwhp/output while the turbo uses recycled exhaust.

So, just for chits n giggles I'll throw out fake numbers with the 75hp Nate was mentioning

Blower setup:
Stock: 240 rwhp 260 fwhp
Blower: 400 rwhp 450 fwhp
Parasitic loss: 75 Hp
Total power the engine sees: 525 BHP

TURBO setup:
Stock: 240 rwhp 260 fwhp
Turbo: 475 rwhp 475 fwhp
Parasitic loss: 0
Total power the engine sees: 475 BHP

I know I didn't account for drivetrain loss and used false numbers but that's the idea. To spin an impeller off your crank robs quite a bit and the engine doesn't really care where the power goes as its just a giant air pump.

There's always an allure to turbos, but I can't say there is one guy out of my local stang group that is turboed that hasn't spent time on jackstands. Whether it was turbo spike from wastegate failure, block destruction, piston/rings fried etc etc you name it. But it's still 100% (7 guys, 4 foxes, 2 NE, 1 2007 s197)

I say v1 with a blow through maf so you can run your blowoff valve. Best of both worlds.

Deleted member 38176 · Apr 3, 2012

fiveohwblow said:
Parasitic or drag loss from spinning the blower robs you of rwhp/output while the turbo uses recycled exhaust.

So, just for chits n giggles I'll throw out fake numbers with the 75hp Nate was mentioning

Blower setup:
Stock: 240 rwhp 260 fwhp
Blower: 400 rwhp 450 fwhp
Parasitic loss: 75 Hp
Total power the engine sees: 525 BHP

TURBO setup:
Stock: 240 rwhp 260 fwhp
Turbo: 475 rwhp 475 fwhp
Parasitic loss: 0
Total power the engine sees: 475 BHP

I know I didn't account for drivetrain loss and used false numbers but that's the idea. To spin an impeller off your crank robs quite a bit and the engine doesn't really care where the power goes as its just a giant air pump.

There's always an allure to turbos, but I can't say there is one guy out of my local stang group that is turboed that hasn't spent time on jackstands. Whether it was turbo spike from wastegate failure, block destruction, piston/rings fried etc etc you name it. But it's still 100% (7 guys, 4 foxes, 2 NE, 1 2007 s197)

I say v1 with a blow through maf so you can run your blowoff valve. Best of both worlds.

I'm well aware of the technical differences between the two setups. What I don't understand is how, according to N8, you can safely run 500+rwhp through a turbo as opposed to only 400rwhp+/- through a blower. Rear wheel horsepower is real wheel horsepower no matter how it's made. How does this apply to nitrous users? Does this mean that a stock 2v can safely run a 300-shot (obviously not)? I don't get it.

N8Dogg98 · Apr 3, 2012

Nightfire said:
I'm well aware of the technical differences between the two setups. What I don't understand is how, according to N8, you can safely run 500+rwhp through a turbo as opposed to only 400rwhp+/- through a blower. Rear wheel horsepower is real wheel horsepower no matter how it's made. How does this apply to nitrous users? Does this mean that a stock 2v can safely run a 300-shot (obviously not)? I don't get it.

There was a member on this board named Hotstang or something who had a twin turbo 2V that made 550 rwhp on the stock block. The RWHP number is really meaningless and what you need to consider is the amount of work an engine needs to do to get to a certain power level. Supercharged cars require more engine effort due to the energy needed to spin the SC impeller.

If you have 2 identical engines, where one is turbocharged and the other is supercharged, at the same RWHP output the turbo car requires less work than the SC does to get there.

That said most turbo cars spend more time on jackstands than they do on the street. Unless you're paying someone to install it, you buy a very reputable kit, or are good at custom fabrication I'd stick with the SC.

fiveohwblow · Apr 3, 2012

N8Dogg98 said:
There was a member on this board named Hotstang or something who had a twin turbo 2V that made 550 rwhp on the stock block. The RWHP number is really meaningless and what you need to consider is the amount of work an engine needs to do to get to a certain power level. Supercharged cars require more engine effort due to the energy needed to spin the SC impeller.

If you have 2 identical engines, where one is turbocharged and the other is supercharged, at the same RWHP output the turbo car requires less work than the SC does to get there.

That said most turbo cars spend more time on jackstands than they do on the street. Unless you're paying someone to install it, you buy a very reputable kit, or are good at custom fabrication I'd stick with the SC.

Precisely what I spent my time explaining and he didn't want to understand. Whatevs.

Rwhp is only a function of efficiency and turbos are more efficient. Therefore if you stress your block to 100% without something robbing power, more rwhp. It's simple to me......

N8Dogg98 · Apr 3, 2012

^ why didn't you like my post then...

N8Dogg98 · Apr 3, 2012

Nightfire = View attachment 152142

Deleted member 38176 · Apr 4, 2012

Like I already said, I understand about how turbo's and blowers make their power in relation to the motor. I don't need it to be repeated 10 times, using different words....

What you're essentially saying is that the stock 4.6 2V can safely handle 500+rwhp, except that a supercharger setup eats 100rwhp or so (hence why you only see 400-450rwhp max from an SC and apparently 500+ from a turbo). I just don't think it works like that. Just quickly searching through multiple Mustang websites, the verdict is the same (including from the turbo manufacturers themselves), do no exceed 425+/-rwhp on a stock motor. Like I previously mentioned, how does nitrous factor into this argument? It obviously costs the motor zero power to make power through nitrous. Does that mean that 200 or 300-shot can be run on the stock motor?

Thundermouse · Apr 5, 2012

Nightfire - What N8Dogg98 and fiveohw are trying to explain is that because superchargers and turbochargers work through different means to compress air, it is inevitable that they require different amounts of energy to create an equivalent boost pressure. They have correctly extended their explanation to state that, for example, a turbocharger @ 7psi will create Z more net RWHP than a supercharger at 7psi because it is more efficient to use the heat of the exhaust as the energy source for the compression rather than the torque of the crankshaft. I think you understand this.

The next logical step I think you are missing is what causes problems for the stock rotating assembly. You seem to be focused on the train of thought RWHP is the ultimate measure of stress on the rotating assembly. While RWHP measurements in apples to apples powertrains can be a useful relative indicator, turbochargers and superchargers change the scenario to apples & oranges and the RWHP measure loses some of its comparability.

Maybe it will help to think back to the basics. Remember that both of these forced induction power adders increase the mass of air entering the cylinder so the computer can add more fuel to create a more potent combustion. As the boost pressure increases, so does the amount fuel injected, and therefore the greater the explosion. When the boost pressure high enough (and therefore the explosion), some part of the stock rotating assembly fails. (the concept is this paragraph is no different for either power adder).

Each individual engine and tune is subject to thousands of variables, but for the average case we can reasonably say that the rotating assembly failure threshold (in terms of combustive power) will be the same from either source of force induction. Working logically backwards, the same level of psi boost by either a turbocharger or supercharge will cause the rotating assembly to fail.

It goes without saying, all Mustang owners who have forced induction on stock bottom ends will likely try to run the highest boost they can without going past the failure threshold.

Now go back to what N8Dogg98 and fiveohw tried to explain. If a supercharged 4.6 and a turbocharged 4.6 are both running the highest safe boost level, the turbocharged Mustang will deliver a higher RWHP, solely because of the higher compressing efficiency from the turbocharger.

Regarding what the manufacturer's recommendations are for their products - I see no incentive for them to make claims that the stock rotating assembly can handle high boost (or power levels).

1) If they sell direct to self installers and the self installers suffer destroyed rotating assemblies because they tried to run it close to the manufacturer's (high) ceiling, the self installers are likely to not give their products good reviews by word of mouth or otherwise.

2) If they sell through speed shops, they are unlikely to see continued orders from the shops if their kits keep destroying the speed shops' customers' rotating assemblies. Instead, by keeping the recommended boost (power) levels low, the manufacturer is helping out the speedshop by inducing the customer to buy an upgraded rotating assembly from the speedshop. The manufactures rely on the speedshops to stay in business, so it only makes sense to help them especially when that help comes at no cost.

Rather than looking at manufacturer websites for insight to the theoretical limits that each form of forced induction, stock rotating assembly, a 4.6 can handle, instead look to what owners with experience say about the limits they reached. It is generally consistent across many message boards that the turbo 4.6 Mustangs consider their RWHP threshold in the 500s on a stock rotating assembly while the supercharged 4.6 Mustangs consider it in the 400s.

When you throw Nitrous into the equation - forget what I said about apples and oranges and start thinking apples and coconuts. Too many dynamic variables (delivery method, duration, heat, tuning variables, etc.) with Nitrous to keep anyone from making accurate generalizations linking a RWHP level to a level of safety. Maybe there are some nitrous experts that can chime in. But as for me, I know enough about Nitrous to know that it’s very complicated, and I can't help any further.

*edit - fix the autocorrect Stangnet made to fiveoh's name

fiveohwblow · Apr 6, 2012

^spot on for the first 5 paragraphs.

I quit reading after

N8Dogg98 · Apr 6, 2012

Yep, like he said nitrous oxide is completely different because you're essentially changing what happens within the combustion chamber, while what goes on in the combustion chamber between SC's, turbo's, and even N/A is relatively comparable.

Want to go Turbo. Have some???

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