Translator

Other than reduced noise levels, are there any advantages (efficiency, cooling, IAT's, etc...) of going with helical over straight cut gears on a centrifugal unit? I do seem to enjoy that more procounced "whistle" with straight cut gears a little more. However, I wonder if it would get "old" and bothersome after a while?

robertf97

http://bakerdrivetrain.com/wp-conten...vsstraight.pdf

The whistle noise comes from air moving, you an hear it on a turbo as well which doesn't have any gears. Gear noise is like "whine".

Translator

^^^ Thank you Robert. Although the attached article is related to transmissions, can the same principles be applied to the gears of centrifugal superchargers? If so, the article states that straight cut gears are more efficient than helical...

0ProChargerTech

Its just a sound preference. Some people love that strait cut gear sound, others want that subtle whistle of the helical gears.

However, once a blower is made one way or the other, there is no changing it out. The entire inside of the blower is made specific to which gear set it has. (different bearings as well)


The whistle is from the gears actually, not the air moving.
Our blowers are not moving enough air at low RPM, to create that effect that you are talking about.

That write up you posted is about transmissions in cars that have to endure moving a 3,000+lb object.
Our gear boxes are very different as they are moving a small light impeller, however at a very hight rate of speed.

Supercharger gear boxes are kinda in a world all of their own.

Translator

^^^Thank you ProCharger, so I was correct in assuming that blower gears differ from transmission gears.

Given that, is it then safe to assume that there is NO different in durability, reliability, or efficiency between two identical head units, with the only difference being one with the straight cut gears and the other with helical gears?

robertf97

The laws of physics apply no matter what the procharged tech says, if you put a helix on a gear it will be less efficient. And turbos still whistle without any gears.

Theta

I have an incredibly loud amount of air moving at idle and off-idle causing the loud suction sound, but gear whine is certainly a bit different.

It depends on what you're looking for. I would have gone straight-cut if I had the option, but I think (from seeing thousands of FI posts over the last 16 months) straight vs. helical sales would show the clear trend winner to be helical now for the reduced noise.

My air whoosh was cool for the first few days. Now that I'm pushing a stupid-high amount of air, I need another BOV at the minimum to quiet it down. It's not that fun to drive it, because I go deaf at high frequencies after 15 minutes or so.

Just keep in mind what your application is - if you want a street sweeper, straight-cut and a Tial Q are the ticket. Just prepare for the noise - it's not subtle. Of course, it does scare the crap out of people, which makes it a little more fun.

But in all seriousness, when I pass an oncoming car, all I hear is the air sucking - not even the exhaust (and it's loud as hell).

0ProChargerTech

Correct.


There is a "slight" difference in drive power. However not something a customer is going to notice even in the slightest. And that is not going to change the effeciency of the impeller/volute.

The "whistle" from a turbo, is much different then the gear whistle from a ProCharger. Turbos impellers also operate at a much higher RPM then ours do.

Not saying they don't whistle, just stating that most people talking about "ProCharger Sound" are talking about the gear box.

SUNRISE1

I went with the quieter blow-off valve and am pretty happy with the sound. no annoying sounds as Theta describes.. yes you hear the SC when you get on it and then the blow-off but its all good. fyi ECS system with straights cut

Theta

Not to derail, but could I ask you which one you're using? The QR is the quieter Tial with the 50mm flange, but I'm worried that it wouldn't blow off quickly enough for my pressure level.

They've suggested using two, but I hadn't talked to anyone yet that's used the QR with a filter instead of using it as a DV.

I think a lot of us can agree that the Tial Q is very loud even at 7/8psi. At 13 it's ear-shattering (in a bad, ears-ringing kind of way).

SUNRISE1

Yes I have the QR. I'm not experienced enough to answer or comment on your other concerns or questions though about 2 vs 1 etc... did you ever get a chance to test your LMR breather reroute to get the foul air away from the cabin air intake? Pm me or post on that LMR thread when you can. Thanks.

Theta

No worries - I appreciate knowing it's the QR. I will keep you posted on that project - I've not had any time to work on the C7 in the last month.