Over Spinning ProCharger

[80FoxCoupe]

Question: Is spinning the engine faster (to 8100 rpm) but substituting in a larger pulley thus creating less boost at the same rpm as the current pulley actually beneficial? It seems the smaller pulley making slightly more boost but only spinning the engine to 7800-7900 rpm would make about the same amount of power as the larger pulley at 8100 rpm, but safer due to the lower rpm. Just something to consider.

You are splitting hairs. Smaller pulley and more engine rpm is what I would do.

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[Jcole_14]

Question: Is spinning the engine faster (to 8100 rpm) but substituting in a larger pulley thus creating less boost at the same rpm as the current pulley actually beneficial? It seems the smaller pulley making slightly more boost but only spinning the engine to 7800-7900 rpm would make about the same amount of power as the larger pulley at 8100 rpm, but safer due to the lower rpm. Just something to consider.

On my current 3.125 pulley it made peak power at 7,800rpm and spun the unit 69,383rpm but if it were taken to 8,100 it would spin the head unit to 72,052rpm causing the head unit to overspin over the recommended rpm range by 4-7,000rpm. My concern was over spinning the unit and causing damage with the current pulley.

So I was wanting to see about a 3.375 pulley so I could rev the car all the way to 8,100rpm with only over spinning the unit by 1,700rpm. So the main concern was over spinning the unit rather than the power.

with the 3.125 pulley I’m over spinning the head unit from ~7,400-8,100rpm. But with the 3.375 pulley I’m over spinning the head unit from 7,900-8,100rpm. Smaller window and less over spinning basically. And I’m not sure how power would be delivered w new pulley.

 

[80FoxCoupe]

On my current 3.125 pulley it made peak power at 7,800rpm and spun the unit 69,383rpm but if it were taken to 8,100 it would spin the head unit to 72,052rpm causing the head unit to overspin over the recommended rpm range by 4-7,000rpm. My concern was over spinning the unit and causing damage with the current pulley.

So I was wanting to see about a 3.375 pulley so I could rev the car all the way to 8,100rpm with only over spinning the unit by 1,700rpm. So the main concern was over spinning the unit rather than the power.

The time you are in the upper Rev range is so minimal. Not like a boat where you hold it wide open for 10min...

You seem very concerned about this, maybe staying with what you have is the better route.

 

[Idaho2018GTPremium]

On my current 3.125 pulley it made peak power at 7,800rpm and spun the unit 69,383rpm but if it were taken to 8,100 it would spin the head unit to 72,052rpm causing the head unit to overspin over the recommended rpm range by 4-7,000rpm. My concern was over spinning the unit and causing damage with the current pulley.

So I was wanting to see about a 3.375 pulley so I could rev the car all the way to 8,100rpm with only over spinning the unit by 1,700rpm. So the main concern was over spinning the unit rather than the power.

Yes, I understood all that. My point was - why use more engine rpm to create the same amount of boost as you currently make at a lower rpm? If you replace the pulley with a larger one and make the same power at 8100 rpm as you currently make at 7800 rpm, then you've gained nothing, except spinning your engine 300 rpm higher for no gain. Therefore, just keep shifting at 7800 with your current pulley. On the flip side, if you use a larger pulley+rev to 8100 rpm and make more power than before, then that's an obvious gain and go that route.

I agree regarding not over spinning the unit to 72k rpm - that is probably beyond the safety factor of the head unit design.

 

[Jcole_14]

The time you are in the upper Rev range is so minimal. Not like a boat where you hold it wide open for 10min...

You seem very concerned about this, maybe staying with what you have is the better route.

It was mainly my concern for how much I was over spinning the head unit and for the rpm range it was occurring for.

with the pulley I have on it’s over spinning higher and for longer. Versus the 3.375 which over spins less for a shorter amount of time.

but that is a very good point you have.

 

[Slow306stang]

On my current 3.125 pulley it made peak power at 7,800rpm and spun the unit 69,383rpm but if it were taken to 8,100 it would spin the head unit to 72,052rpm causing the head unit to overspin over the recommended rpm range by 4-7,000rpm. My concern was over spinning the unit and causing damage with the current pulley.

So I was wanting to see about a 3.375 pulley so I could rev the car all the way to 8,100rpm with only over spinning the unit by 1,700rpm. So the main concern was over spinning the unit rather than the power.

The setup with the 3.125" pulley and 7800rpm will be significantly faster than the setup with the 3.375" and 8100rpm. Why rev to 8100rpm and slow the car down?

 

[Jcole_14]

Yes, I understood all that. My point was - why use more engine rpm to create the same amount of boost as you currently make at a lower rpm? If you replace the pulley with a larger one and make the same power at 8100 rpm as you currently make at 7800 rpm, then you've gained nothing, except spinning your engine 300 rpm higher for no gain. Therefore, just keep shifting at 7800 with your current pulley. On the flip side, if you use a larger pulley+rev to 8100 rpm and make more power than before, then that's an obvious gain and go that route.

I agree regarding not over spinning the unit to 72k rpm - that is probably beyond the safety factor of the head unit design.

Basically just for the reason of over spinning the head unit less and for less time. But after reading other comments on that option it doesn’t seem very worth it.

 

[Jcole_14]

The setup with the 3.125" pulley and 7800rpm will be significantly faster than the setup with the 3.375" and 8100rpm. Why rev to 8100rpm and slow the car down?

Just to over spin the procharger less and for less time. Basically my only concern.

 

[Idaho2018GTPremium]

Basically just for the reason of over spinning the head unit less and for less time. But after reading other comments on that option it doesn’t seem very worth it.

I see; even at 7800 rpm you're over spinning the head unit. You're essentially over spinning it at any engine rpm beyond ~7,300 +/-. But I agree with Fox, you're not above 7300 rpm very long, time-wise, so it's probably not that big of an issue, but then again, I didn't design the unit so I can't say what kind of safety factor that 65k limit has built into it. What if that is the limit w/ the SF? Then it's just a matter of when, not if, it goes.

I'm pretty conservative with this stuff, so if it was me I'd probably change the pulley to be safe, and keep it closer to the max recommended head unit speed.

Until then, I'd limit the time above 7500 rpm just to be safe. But that's just me...Good luck.

 

[SolarFlare]

Also crazy to see that you made that number because they say they’re only good for ~700whp and making 850whp is much larger than advertised lmao.

blanket number meant to cover all cars. Coyote engines are pretty efficient. I made over 800whp and still was about 1500rpm from max rpm of 65k on E85 with the p1sc.

 

[Jcole_14]

I see; even at 7800 rpm you're over spinning the head unit. You're essentially over spinning it at any engine rpm beyond ~7,300 +/-. But I agree with Fox, you're not above 7300 rpm very long, time-wise, so it's probably not that big of an issue, but then again, I didn't design the unit so I can't say what kind of safety factor that 65k limit has built into it. What if that is the limit w/ the SF? Then it's just a matter of when, not if, it goes.

I'm pretty conservative with this stuff, so if it was me I'd probably change the pulley to be safe, and keep it closer to the max recommended head unit speed.

Until then, I'd limit the time above 7500 rpm just to be safe. But that's just me...Good luck.

My thoughts exactly, couldn’t have said it better. I’m on the fence about it because it seems like everyone over spins more than recommend, but I run the risk…

Worth to mention my old setup was with the 3.125 pulley hitting 7,500rpm and with the 3.375 pulley hitting 8,100rpm they hit the same rpm for the head unit being ~66,700rpm which I’m okay with. Power delivery might be different but I should keep roughly the same whp I had before.

I’m going to keep the 3.125 pulley until around March and make the decision then though. Thank you for the help.

 

[Jcole_14]

blanket number meant to cover all cars. Coyote engines are pretty efficient. I made over 800whp and still was about 1500rpm from max rpm of 65k on E85 with the p1sc.

How’d you manage that? I’m also on E85, I have a good fuel system, a stage 2 intercooler, ported boss manifold and I’m maxing mine out and not even making over 750 lol.

 

[SolarFlare]

How’d you manage that? I’m also on E85, I have a good fuel system, a stage 2 intercooler, ported boss manifold and I’m maxing mine out and not even making over 750 lol.

exhaust? inlet on or off? At elevation? what pulley?

 

[SolarFlare]

might be slipping. logs? What boost is it seeing in your particular setup?

 

[Jcole_14]

exhaust? inlet on or off? At elevation? what pulley?

1 7/8” stainless works headers and ffe. Inlet on. North Texas. On a 3.125 pulley.

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