Today I was cleaning my engine bay on the new motor and I saw my belt was ripped in half from the custom tensioner pulley.
It doesn't matter because I'm upping the boost from ~13 pound to approximately ~20-25 so I don't care.

At current, my kit comprises of the Novi 1500 with a SoS 3.2" pulley making 13.4 psi @ 9000rpm.
Now I'm going from the Comptech supplied crank pulley + OEM crank to a custom 7" (54cm outer circumference) replacement crank pulley, whilst downsizing the 3.2" SoS pulley to the 3.0" SoS pulley I also already have.
At current I have a (tightly fitting) 6pk950 (thus 950mm in length) belt attached to the Comptech + OEM Crank with the 3.2" SoS pulley.

My series of questions are....

Its been so long since I've done the install and swapping of crank pulleys, can anyone remember or know what size the Comptech supplied Crank Pulley is?
Which then leads to my 2nd question, can anyone tell me approximately what size belt I will now need?

Illustration drawn below to better simulate whats happening.

 

I can't even find one 2nd hand here on s2ki to ask someone to measure up the bolt on crank pulley piece. Does anyone have an SoS or CT kit not yet installed and could measure this up for me? Least from there we can figure it mathematically.
Worst comes to worst, I guess we just bolt it all on and get a piece and string and rope it around the 2 pulleys, see how long it is and buy the 2 nearest belts to match.

 

https://www.s2ki.com/s2000/topic/588.../page__st__100

have a look, crank pulley is about 5.25 on the original comptech kit, check with the 7" pulley you made that you are not exceeding impeller speed.

If you have a pic of the custom pulley you fabricated I would love to have a look. Is the offset the same as with the original comptech kit with the novi 1000?!

 

This particular N1500 is from Ry's old race car setup and he and Shad are responsible for the making of this particular crank pulley. I bought this setup from the US about this time last year. I now have a built engine and wish to max out the impeller speed to its best efficiency as the motor will take it with ease.

My build thread so to speak, can be found here:
https://www.s2ki.com/s2000/topic/771..._fromsearch__1

Here are 2 graphs from one of Ry's threads re: N1220 / 1500 with the 7" crank pulley in place.






As you can see it only netted approximately 17ish pound.
Joey aka Ilovemyhonda1984 is running his N1500 around 24psi with E85 which is right in the efficiency zone for this blower. I'm not wishing to push it that far just yet

As for pics of the 7" pulley I will supply some tomorrow if you wish? (its 9pm here in Australia).

 

Just posting for future reference for anyone who wants to follow and go this route..

We devised using the centre bearings (~310mm apart) of each pulley that with a 3.2" pulley and a 950mm length belt, the Comptech crank attachment is ~5"
Using this information we figured out the new belt length will need to be that of a 1020mm length at the shortest, up to a 1028mm at the longest given a few additional variables such as how much contact point the belt has on the 2 pulleys.

So using this theory, I'm going to buy a 6pk1025 and use the tensioner to adjust stuff whatever way necessary. Think I'll buy a 1030 or 1035 too just to be certain.

Funny thing is, after taking a break last night because my head was full of f@#k, (last night I kept thinking linear mass (belt length dictating the boost amount) rather than rotational mass of the input and output pulleys giving the boost increments), so came back to it earlier today and everything is sweet. Just needed a break!

If anyone wants to verify those numbers are correct for me though, please still chime in.

I'll post up a picture of the 7" pulley shortly.

 

About the SOS question...My SOS supplied pulley is 5.45" in belt tooth diameter. I got this info from SOS when Paxton asked for the crank pulley size when my blower was sent in for repairs.

 

Few days late, my bad.

 

For those curious, I ordered a 6pk 1035 and it fit snug as / perfect.

 

Comptech crank pulley