SC vs Turbo for max safe HP limits on stock internals

[Andy13186]

Since SC are belt driven and take some HP to run, does that reduce the max hp the engine can handle in comparison to turbos? Or does just the actual HP being made matter?

For example : if the max safe hp of a car was 750rwhp with a SC, would it be the same on turbos or could the engine handle making more HP on turbos?

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[Zelek]

Turbos are more efficient and can make the same power on less boost. That's not to say huge blower can't do 1000+ but turbos make it easier. Just a more complicated setup. Anything probably 800+ regardless of FI choice is playing with fire on stock internals.

More people have switched to turbo setups after running high HP SC builds from what I have seen a lot. Controlling the boost is a nice feature you can do with turbo.

 

[Jay-rod427]

Yes you can make a little more with turbos as like you said the blower takes some power. But IMO it's worth it for consistency. No building boost and shit at the track.

 

[MadCow]

Max power limit and max power potential are always going to be higher with a turbo than a belt driven charger. The belt driven charger always uses some power to turn it. Also, belt driven chargers sometimes have issues with breaking crank snouts, not just in coyotes, but in general. Maybe user error, make crank flaws, whatever, but its definitely more rare than in engines with exhaust driven chargers. All the engine knows is 1000whp worth of cylinder pressure, It doesn't know what you are doing with it.

 

[bluebeastsrt]

Any current boosted application is enough to break a stock motor. Turbo, roots,centri. Dont matter. Get what you want. And what your budget allows.

 

[gimmie11s]

Turbos are generally easier on the motor.

And don’t play with overdrive pullies on blower set ups if you end up going supercharged.

 

[Ryan_s550]

If you are pushing the limits turbos will be easier on the engine. Think about this....to make 700 ft. lbs of torque you need a given cylinder pressure to produce that torque plus the additional cylinder pressure to drive the supercharger. With turbos you only need the given pressure to make the same amount of torque. The power produced by the turbos isn't "free" but being that it is driven off the exhaust, you are driving it off the exhaust stroke of the engine vs the power stroke. I don't know if I explained that very well, but hopefully that explains it a bit. The last LSX engine I built had rods rated to 1200hp. In turbo applications they gave them a rating of 1400hp. That alone without getting technical will tell you that turbos are easier on the engine.

 

[Andy13186]

Thanks guys

So I am now thinking that the max safe HP for supercharged cars is lowered by the amount of HP it takes to run the SC in comparison to the turbo setups. Basically running 750rwhp with a SC setup is just as hard on the engine as running like 850rwhp on a turbo setup if the SC takes 100 hp to run.

Since there is no parasitic HP loss from turbos I suppose the fueling requirements on a turbo setup would be less if the HP levels are the same too.

If this is incorrect let me know. I was pretty set on a whipple but these benefits make the choice harder.

 

[engineermike]

There may not be parasitic crank losses with the turbos but there is much increased pumping losses. Many are shocked to find out that exhaust pressure at the port can easily be 2x boost pressure. At 10 psi boost, you could be seeing 20 or even 30 psi in the header. This compares to optimally less than 5 psi there. This is still much more efficient than taking 100-150 hp off the front of the crank but it’s still not “free”.

 

[Ryan_s550]

I don't know that you can calculate it exactly like that. The turbos still cause pumping losses due to backpressure which still uses up power. Its not free horsepower like many say. I am sure with a lot of math and knowing the exact setup it could be calculated. The kit design, boost/backpressure ratios and other variables will play into it. The short of it is turbos are a little friendlier when you are pushing things. I personally have a Gen 3 Whipple and l wouldn't trade it for a turbo setup for how I use the car. I enjoy the response and huge torque curve of the Whipple. If you are trying to go as fast as possible in a straight line on a stock motor, turbos are the way to go. I am making 760 with no engine related issues. I recently went to a track day. I ran the car hard and it did great through 4 20 min sessions. I did have the power backed down to about 690.

 

[Ryan_s550]

There may not be parasitic crank losses with the turbos but there is much increased pumping losses. Many are shocked to find out that exhaust pressure at the port can easily be 2x boost pressure. At 10 psi boost, you could be seeing 20 or even 30 psi in the header. This compares to optimally less than 5 psi there. This is still much more efficient than taking 100-150 hp off the front of the crank but it’s still not “free”.

If drive pressure is 2x boost pressure you have a severe restriction with the exhaust or the turbine housing itself. You won't run into this issue on any of the popular mainstream turbo kits in the 700-800 range. Most all of them support 1000+ hp with the base turbos.

 

[engineermike]

If drive pressure is 2x boost pressure you have a severe restriction with the exhaust or the turbine housing itself. You won't run into this issue on any of the popular mainstream turbo kits in the 700-800 range. Most all of them support 1000+ hp with the base turbos.

I'd love to see some data on the available S550 kits. I've done these measurements myself on a single setup with full exhaust. I started out at 2.3/1 and made some improvements to get down to 2/1. The car ran high 9's at 146 mph at 4000 lb on street tires and pump gas (an SBC/LT1, at that). I've seen published numbers approaching unity, some even below 1/1 but they were full race setups that were slow-spooling and had no exhaust after the downpipe. It also depends on the rpm where you measure it. Boost curves should be pretty flat, but the drive pressure rises with rpm. The ratio is much worse at redline than it is at low and mid rpm. My numbers were recorded at redline.

 

[Jay-rod427]

These baby blowers we talk about here don't take 100-150 horse to turn them....

OK continue the exhaust driven Procharger debating now.

 

[Ryan_s550]

I'd love to see some data on the available S550 kits. I've done these measurements myself on a single setup with full exhaust. I started out at 2.3/1 and made some improvements to get down to 2/1. The car ran high 9's at 146 mph at 4000 lb on street tires and pump gas (an SBC/LT1, at that). I've seen published numbers approaching unity, some even below 1/1 but they were full race setups that were slow-spooling and had no exhaust after the downpipe. It also depends on the rpm where you measure it. Boost curves should be pretty flat, but the drive pressure rises with rpm. The ratio is much worse at redline than it is at low and mid rpm. My numbers were recorded at redline.

What size turbocharger was that using? Single kits seem to have backpressure issues more often than twins. However that is not always the case.

 

[engineermike]

Mine was a PT76GTS.

By the way, exhaust pressure, as we know, can be calculated but it’s relatively complex. The ecoboost ecm actually calculates it on the fly and uses it as a correction to volumetric efficiency to make the SD calc more accurate. That’s one of the reasons turbo upgrades on the ecoboost haven’t taken off.....because it throws off the exhaust pressure calc and, thus, the ve calc.

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