[Dysan911]

So I noticed with the summer heat that my P1 will typically generate less than 6lbs of boost. Assuming when cooler weather gets here will that go up a little?

So would it require a belt change and re-tuning to just drop one pulley size? I have the 4.00 now. I think the next one down is a 3.90. Would the tune im running now just self-adjust to an extra pSI or two that I may get from a drop in size that small?

[Dysan911]

Guess I stumped everyone with that one.

[Sol4rfl4re]

Generally such a small step down will not require a belt change. You will also not see one psi. I'd say the blower is turning about 1000rpm higher at the top of your band, 1/2psi maybe.

[Dysan911]

Originally Posted by Sol4rfl4re

Generally such a small step down will not require a belt change. You will also not see one psi. I'd say the blower is turning about 1000rpm higher at the top of your band, 1/2psi maybe.

Ahh ok. So typically if someone wants a few more PSI they will drop a couple sizes down from the current pulley.

THanks for explaining!

B.

[Sol4rfl4re]

Originally Posted by Dysan911

Ahh ok. So typically if someone wants a few more PSI they will drop a couple sizes down from the current pulley.

THanks for explaining!

B.

It really depends on the setup. How restrictive the exhaust and system is. I tend to follow Maf lbs more than PSI. I've had people say "I gained 3psi with this pulley", I get it and see 1psi. My opinion is you will get maybe 1/2 psi and one size smaller will give you the full psi. Do you have a dedicated drive for the P1? If so is it 8"?

If you have the 7.65 crank adapter then going from the 4.0 to a 3.9 you will get an extra ~1300rpm out of the blower at 6500. True benefit in my opinion getting into boost quicker by stepping down 1 or 2 sizes.

[Dysan911]

Originally Posted by Sol4rfl4re

It really depends on the setup. How restrictive the exhaust and system is. I tend to follow Maf lbs more than PSI. I've had people say "I gained 3psi with this pulley", I get it and see 1psi. My opinion is you will get maybe 1/2 psi and one size smaller will give you the full psi. Do you have a dedicated drive for the P1? If so is it 8"?

If you have the 7.65 crank adapter then going from the 4.0 to a 3.9 you will get an extra ~1300rpm out of the blower at 6500. True benefit in my opinion getting into boost quicker by stepping down 1 or 2 sizes.

I like that Maf Lbs. I may have to check that out. Does it align with the same PSI as I would see with a boost gauge? 6lbs of Boost = 6lbs reading on the Maf Lbs?


I'm not sure what you mean about the dedicated drive for the P1.

So to get into boost quicker I may need to drop to the 3.85 pulley.

Also curious how the tuning handles this? Does it require some tweaks or will it adjust the same way it might see a few extra in colder weather? I'm sure seeing 5 or 6lbs in the 90 degree heat might be 7 or 8lbs in the winter time. As far as I know, one doesn't need to run back to the dyno every time the season changes right?

B.

[Sol4rfl4re]

Originally Posted by Dysan911

I like that Maf Lbs. I may have to check that out. Does it align with the same PSI as I would see with a boost gauge? 6lbs of Boost = 6lbs reading on the Maf Lbs?


I'm not sure what you mean about the dedicated drive for the P1.

So to get into boost quicker I may need to drop to the 3.85 pulley.

Also curious how the tuning handles this? Does it require some tweaks or will it adjust the same way it might see a few extra in colder weather? I'm sure seeing 5 or 6lbs in the 90 degree heat might be 7 or 8lbs in the winter time. As far as I know, one doesn't need to run back to the dyno every time the season changes right?

B.

Dedicated drive means the pulley that drives the belt goes from the blower to the crank, accessories are driven by a separate belt.

No, no correlation to boost. For your power level you will likely see somewhere in the high 60s/low 70s for maf lbs at your shift rpm. Stepping down .15 in pulley might give you an extra 1-2lbs of air.

A .15 is a relatively small step down, your tuner might just ask you to make a pull and send him the datalog so he can check it.

[Dysan911]

Originally Posted by Sol4rfl4re

Dedicated drive means the pulley that drives the belt goes from the blower to the crank, accessories are driven by a separate belt.

No, no correlation to boost. For your power level you will likely see somewhere in the high 60s/low 70s for maf lbs at your shift rpm. Stepping down .15 in pulley might give you an extra 1-2lbs of air.

A .15 is a relatively small step down, your tuner might just ask you to make a pull and send him the datalog so he can check it.

Ahh ok that makes sense and yeah my setup is dedicated drive. So would 1-2lbs need re-tuning to be safe? Or do most tunes have enough flexibility built in to deal with extra PSI?

[Sol4rfl4re]

Originally Posted by Dysan911

Ahh ok that makes sense and yeah my setup is dedicated drive. So would 1-2lbs need re-tuning to be safe? Or do most tunes have enough flexibility built in to deal with extra PSI?

Dedicated drive is good. Unsure if DI engines have that flexibility, coyotes can deal with a small step change in pulley. Your fuel trims might be off since your car is trying to correct it but your tuner would say that for sure.

[ProCharger]

Originally Posted by Dysan911

So I noticed with the summer heat that my P1 will typically generate less than 6lbs of boost. Assuming when cooler weather gets here will that go up a little?

So would it require a belt change and re-tuning to just drop one pulley size? I have the 4.00 now. I think the next one down is a 3.90. Would the tune im running now just self-adjust to an extra pSI or two that I may get from a drop in size that small?

Your boost gauge varies with temp. (and daily pressure)
Assuming you are running an run of the mill aftermarket boost gauge.

So say one day its like 14.7 psi out.. and then its 14.3 psi another day.

Well, you just lost half a PSI of boost. (even though you didn't)

Unless you have a really really good gauge that is doing a barometer correction each time you start the key, and can log boost to the .1th of a PSI, I wouldn't worry to much about how it varies day to day.


But, if you drop pulley size, you will want to get a nice custom tune for your fuel quality, and to make sure you got enough factory fuel pump to support it. NOBODY on this forum will be able to tell you that, other then your tuner when he logs the car.

Rock and ROLL!

[Dysan911]

Awesome info guys!. Thank you very much!

[exxit]

Did someone say MOAR BOOST??? It is never a bad time to add moar boosts

Like Erik said; check with your tuner to make sure you have head room at your octane level. A quick fix for an octane wall and cooling would be to look in to adding a proper meth kit. I went with Alky running pure meth because of 91 gas out here in nastyfornia... But I believe you guys are blessed with 93 out there.