lvd1102

Ok i have been searching for comptech pulley sizes vs psi and the information varies from post to post. I currently have a 3.875 pulley which i think yeilds 9psi. I have a UR FMIC and I'm netting 6 psi, so i have a 3psi boost loss. Now i want to get a smaller pulley to net at least 10psi. I have been searching and am getting really confused.

how much psi does the 3.2" pulley produce (before boost loss) and how much does the 3" produce.

SOS says that the 3.2 will produce 11psi and the 3" will produce 12 psi

i have been seeing posts and they vary from like 10psi to 12 psi from the 3.2 and 12 to 14 from the 3" and some posts says that the 3.6" produces 12 psi. its so confusing. If i get the right info i want to make a FAQ post for Comptech(novi 1000)


btw i have an AP1 f20c. any info for the novi 1000 or even the 1220 and if its AP1 or AP2 just so i can compile the data and put it into a post and for my own knowledge because i want to get a pulley asap.

SeanSerino

First, there is a variance of ~1psi between AP1 and AP2, due to the difference in redline.

Second, are you running some type of EMS/tune? If not, high boost beyond ~8psi will blow up your engine.

Pulley size does not always equal boost, directly. What I mean is, a 4" pulley will not yield the same boost on every car (difference in ap1/ap2, aftercooler/fmic/none, other mods/ etc etc), so this is why you find a lot of variance in your search results.

Do you have a boost gauge? Or are you just guessing that you are getting ~6psi? From what I've read, a FMIC should only drop boost ~2psi.

I've seen people reach ~14psi on a 3.0" pulley (if I remember correctly).


With that said, there are too many factors to say pulley X" will yield Ypsi. If I were you, I'd go for the 3.2/3.4" at first, and get it retuned. Get a boost gauge if you don't already have one. Pulleys/belts are cheap enough that it would probably be best to take smaller steps, rather than just going right for the 3.0"

lvd1102

yea pulley's and belts are cheap but tunes are not. yes i know factors do depend on boost. I do have a boost gauge and so did the dyno when i was getting it tuned. I netted 6.1 psi with an UR FMIC and a 3.875" pulley. So if the 3.875 is a 9psi pulley then i lost 3psi thats why i want to know what pulley produces what psi on lets say an aftercooled setup then i can gauge what pulley to buy.

s2000Junky

SOS website is a good general gauge to go from. For some reason they dropped 1psi rating on their pulleys recently though. I found they were more accurate with my findings before. I have made 8psi with 4"... 9psi with 3.8... 10psi 3.6 and so on. Depending on what fmic you run, you can lose as much as 4psi. So if you have determined that you lose 3 and are making 6psi with the 3.8, then really your best bet is to just go with the smallest 3" pulley. That will insure you hit 10psi and could be as high as 11 to maybe even 12 if your efficiency gets better as you boost more which has been known to happen sometimes. 3psi is a big boost loss, 45-60whp compared to running an A/C with the same pulley, so you might as well spin the blower to its max to make your set up more worth your wile. FMIC's on SC's have proven to not be as efficient or effective in making as much power as an A/C set up.

S2SEXY

listen get the 3.0 and some 750cc injectors.tune it and be done with it.i bought 3 different pullies and had to buy 2 diffent set of injectors and new belts for all the pullies as well.save yourself the money and just max it out

lvd1102

yea thats my train of thought. dont want to waste money on different pullies. What is the max psi that rc550's can handle?

s2000Junky

^^^ with an SC 10psi is about it, but its not about psi, its about how efficient is your motor with your modifications. You need to be able to supply enough fuel for how much air your consuming/flowing. 650's will suffice most applications to 12psi.