I have noticed more high horsepower, large blower engine builds going on recently and have a few questions (for positive displacement blowers);

Is there a practical limit to blower size if belt slip is not an issue? Is there any noticable 'lag' with larger blowers compared to smaller ones? Do you run into bypass valve problems with larger displacement units? Is an 8 or 10 rib belt necessary, and how comparable is a 10 rib belt compared to a cogged belt?

I have my sights set on a 370 and a Whipple 3.3, KB 2.8, or Eaton TVS down the road. I wanted to get an idea of what it really takes to get one of these bolted down and spinning! Thanks

 

All blowers and turbos have a compressor map (but the manufacturer may not make the data public), which is a fancy little chart showing how efficient the device is at processing a given amount of air at certain rpms and pressures. What you'd need to do is calculate how much air you need for that 370 motor, how much boost you want to run, how many rpms you want to spin, then.... pick out a blower that will support your maximum needs, but isn't overkill to the point of inefficiency.

Personally, I'd think the whipple 3.3 is too large. The KB 2.8 is probably just about right for a max effort 370. The TVS stuff looks like its going to hold its own too.

For and example, here is a map of the TVS 1900 compressor:

 

Looks like a deep sea fishing depth finder screen to me.

 

That is some funny ****!

 

Or a topographical map of the Olympia mountains....

 

Depending on what you are looking for, yes it is possible to have too big a blower. Using myself as an example. I have a 4.8 with a Radix MP112. Stock, the radix had a rather large 3.7" pulley in order to produce a safe 7ish PSI boost. With that size pulley the engine had to rev to about 2000-2500 rpm to even go into boost. (Side note: It's not mentioned much but the rotors on roots and twin screw blowers are notoriously leaky at low rpm's. Hence there is a minimum rpm before boost starts to build. Centrifugals are of course MUCH worse.) Switching to a 3.25" pulley now spins the blower faster, which causes boost to come in earlier. However, now max boost is a somewhat precarious 10 PSI. So the choice is between weak low end performance or risking damage at the high end. A smaller blower or a larger engine would allow the smaller pulley to bring in boost earlier but would not over-pressurize at higher speeds. Hope this helps.

 

Judging by the title I thought this thread was going to be about fat women and oral sex

 

Jeeezzzz....
I got tears runnin down my face !!!!!!!!

 

Hey Now, My wife is Fat....... and so is my girlfreind....... Just Kidding, My girfreind isn't fat......

 

Very interesting info, makes sense with the leaking and difficulty with low rpm boost. I never knew this before. I can see how that all ties in with the previouse post of the efficiency map above and getting things sized right. I also never knew that the 112 made so much boost on the 4.8. Thanks for the post
How come there isn't a "blow off" valve like a turbo has for a SC? That way you could pully down get all the boost you need down low and when you hit your peak it releases the rest. Is it that hard to build it into the rotor housing?

Oh and all of the jokes are hilarious!!! Funniest thread I've read so far.