JHM Over sized Crank Pulley

B8 S4
#1

The JHM over sized crank pulley was delivered today. Nice piece and looking forward to putting it on. Came with the 8 bolts and a new belt. Stock crank size is 6.385 inches or for the Canadians it’s 16.2179 CM… The oversized JHM is 7.00 inches or 17.78 CM… So it’s 9.63% bigger than the OEM but will verify. Weight wise it comes in at 5.2lbs and the stock one according to JHM as I haven’t weighed it yet is 8.6lbs. I got 8.2 when I weighed the stock one so a total of 3 lbs difference… I attached a few pics below.

Unfortunately, it has rained all day so I haven’t been able to do any logs to gather data on specified boost. I did go though all the logs I had and reviewed the ones where I had logged specified, absolute and bypass. The average delta from a percentage wise in 2nd and 3rd was 8% and in 4th 9%. Little to no bypass in the logs.

Wish I had more data on stage I and II requested boost, actual, iat’s, and timing. Tons of logs but unfortunately, I haven’t been consistent and mostly have stage II data and only a few stage I files. I still think the car will be able to take the additional boost with maybe a little bypass but IAT control will be critical. I really am not worried about the blower itself and if anything should go I’d prefer it that over the motor.

Now I need to decide if I install this first or wait until I get the other part back and installed to test them separately and that one first. I’ll make a decision early next week…

Oh and thanks Jake and JHM!

Edit: to add size of pulley… Edit: to add weight of stock pulley…


http://i1012.photobucket.com/albums/af247/concordslim/IMG_2356_zpsz5zoeeqf.jpg


http://i1012.photobucket.com/albums/af247/concordslim/IMG_2355_zpsgqrkvd3i.jpg


http://i1012.photobucket.com/albums/af247/concordslim/IMG_2357_zps6lcb1roy.jpg

#2

Can’t wait to see your results with this. I’d test this first if you have time.

#3

Subscribed.

#4

Look fwd to the results!

#5

Nice you got it in!

I measured with small calipers so have the error of multiple measurements - every which way from Sunday shows around 9.5% overdrive - basically like all the stage II pulleys measured.

The belt is a Gates 7-rib 1305mm belt, instead of the OEM 1275mm (stage I/stage II). There may be a little more slack in the tensioner with the Stage II pulley, like 5-10 mm extra belt, but the tensioner should make it up.

I think you should figure out the other mod first - everything will look different in the logs, and you need to have a baseline…then go for the new pulley. FWIW you may find the tune for the other mod needs some work.

#6

lol I read this wrong

http://www.automotofoto.net/wp-content/uploads/2012/08/CSCS-2012-Round-4-THUMBNAIL-8.jpg

#7

Wow its exciting to see this next chapter in the B8 S4 game. I dont know what your other mod is but considering the time of year and the closing window I would probably not take too much time to test things indpenentently depending on what the other part or parts are. If the end result is going to be both the parts working together for most people. I would skip all the time trying to seperate everything and get to the package results.

#8

Woot!

#9

Kudos for doing what I was too scared to experiment with… Very excited to hear how this works out and to learn more about this other mod haha

#10

Speaking strictly from the perspective of raising the boost level, why not just run an even smaller supercharger pulley, as opposed to a smaller SC pulley and larger crank pulley?

(I understand there are certain perceived benefits of a lighter crank pulley, and am also aware of the stock crank pulley units occasionally failing)

#11

Not sure it’s actually possible to run a smaller sc pulley than a stage 2. It would just probably start slipping.

#12

Yeah, JHM touched on this, but a smaller pulley means less surface area for the belt on the pulley and more chance of slipping. You are also running out of room to shrink the pulley, keep the same amount of material on the outer portion, and still have clearance between the pulley and supercharger snout it mounts on. It’s a really tight fit on the back/inside of the pulley at the current stage 2 size.

#13

So figured I’d do a quick update… Pulley is going on Thur. Thompson is open Sat./Sun but it may be an event Sat. so I’ll need to call, since the schedule is not clear… 58 Sat. but almost 70 on Sunday so I’m hoping to go Sat. We’ll see though, I have a bunch of other things to do on Sat. so I can’t be there all day just to make a pass or two… If I don’t go Sat. I’ll do a bunch of logs to see how boost, iats, timing, bypass, etc look…

Just paid for the other mod and it will be here late this week or early next and I’ll get that on ASAP, and should test next weekend…

Jake, Hopefully, I’ll post some nice times and get some logs you can share with the fine folks on vendorzine… That way you guys can sell a shit ton of these… Love all the naysayers over there…

#14

regarding the secret mod, a few questions

  1. will it be accretive to your current setup (stage 2, lw parts, race gas)? Or will it be an easier way to get to your current performance levels?
  2. is it a fuel source in any way?

Just guessing for fun.

#15

[quote=“sakimano,post:14,topic:7932”]
I guess you could say a little of all of the above actually… lol

Pretty sure I’ve already given it away but until it’s done and on the car I’d rather not announce it so to say… No worries though I’ll disclose everything once it’s squared away…

#16

Right on! I am excited to see what you are able to achieve with this!

#17

alky…

#18

Nope…

#19

Can I play?

#20

Nope