Z32MadMan

LHT for the install to get it all sorted

outeiroj

I would agree with Kyle on this. KW even says on their site its a 12.5psi pulley for that kit.

s2000Junky

There typically isn't going to be a 4.5psi spread between sea level and 7-9000' where ever your measuring from. I could see 1 maybe even 2-3psi loss maybe. Thinking more likely other variables like belt slip if pre cogged system, or boost leaks, or stock cat back with cat or hfc increasing pressure above average.

outeiroj

if i remember correctly kw never offered the 38 in anything other than the cog, but I could be mistaken. The only 38's that I have seen on this forum or on the facebook group push that much psi were on e40+ or meth injection. It would require running a 75mm or smaller pulley and would overspin the blower on pump.

s2000Junky

I don't know either on the 38 cogged or non option. But I do know that regardless of what fuel you run, these blowers whether the C30 or 38 don't take kindly to over spinning max recommended limit, they grenade. Anyone running past is tempting fate. If you want to run 15+ psi reliably you get a Novi.

Car Analogy

...or you get a smaller rotrex pulley but use a lower rev limit on the car. More power sooner, more power overall. But this changes the basic nature of the car.

outeiroj

Not starting an argument, but he blatantly said he's running 17psi out of the box. That is not happening on straight pump gas. Im not saying you can't run 17psi on this blower, not out of the box, not on pump gas

s2000Junky

I've found this to generally not work that well with Centrifugal chargers, here is why. Sure you will fatten up the mid range a bit more then before but now at a sacrifice to top end power if you are maximizing the blower speed in both scenarios. Also by lowering the rev limit you are cutting off your mph per gear shortening the spread more then it already is. An increase in blower speed at idle and lower rpms also increases IAT heat overall, further lowers efficiency. Its better for sake of extracting the most power possible to rev the engine up to its natural peak rpm efficiency and size the pully on the blower to that, to reach its efficiency window at the same rpm range. This will be different slightly between an F20 or f22. An F22 would likely suit you better.

outeiroj

Its not uncommon for ap2 guys that stay on stock fuel to lower the rpm by a few hundred because above 7800 rpm the blower is less efficience so there not point in waiting until 8200 to shift... That being said the ap2 kit also comes with a 90mm pulley vs the ap1 kit coming with 100mm pulley because the higher displacement of the engine lowers the boost of the kit. One inline pro built my engine to a 2.4 i saw my boost decrease vs stock due to extra displacement

s2000Junky

That's not how it works. The smaller 90mm pulley is to increase boost per rpm so that it yields the same peak blower speed at the lower f22 rev limit vs the higher rev f20/100mm combo.

As for your F24 I don't have all the info regarding your build, but assuming the natural safe tendency to lower the rev limit due to the added stroke, that has decreased your peak boost yielded, not the displacement itself, also if it has lower compression pistons that will net less boost as well.

Regardless of what fuel you run, the Rotrex blowers don't like to be over spun, they blow up rather then just blow hot air like a Novi. Therefore if your running a pulley that maxes the blower too soon in the rpm, then you have to reduce engine rpm as its much more crucial to saving the blower as the primary motive then it is for fuel or engine limitations.

Again match the max blower speed to crest as the particular engine you are running makes its peak rpm efficiency/power. Out of the box for the F22 its 7800rpm. For the F20 its 8300rpm. If you want to not blow the blower up that should be your limit, if you want to use the entire rpm limit for practicality and overall wider usage, size the pully to reach max blower speed at max redline engine speed. You will get the most overall out of the package this way.