Honda D Series Forum banner

1 - 4 of 4 Posts

·
Banned
My car...
Joined
·
1,875 Posts
Discussion Starter #1
I know when you run the throttle body between a Eaton and the engine, you need a pretty good 'blow off valve' (don't remember the proper name) to prevent the supercharger from blowing the throttle open when you close the throttle (to prevent a run-away engine), which is why JRSC's have the TB before the SC.

So why don't you need that on a engine with a centrifugal supercharger (like a Vortech or Rotrex)? Most Vortech setups I've seen have the TB between the blower and the engine.
 

·
Registered
68 Camaro
Joined
·
4,583 Posts
tb springs are strong.

you wont over power it with anything less than a shit ton of psi and cfm to affect the blade


plus it rotates outwards, not inwards so its impossible except for such a massive, jet engine amount of air that it would give the thing lift like an aircraft wing and the put prressure on the tb that would overcome the spring tension.
 

·
Registered
1988 Honda CRX
Joined
·
6,676 Posts
An Eaton is a roots type blower which is positive displacement. If you block the outlet and keep turning the pump, it builds pressure until something breaks as air cannot escape back to atmosphere except for the very small amount that leaks past the rotor clearance.

On a centrifugal, they throw air in a certain direction but do not trap it, so when you reach a certain pressure, the airflow stalls.

If you use a throttle downstream of a positive displacement blower like a roots, screw or piston type, in my opinion you need at least two safety devices to avoid engine runaway. These can be a blow of/pop off valve, a bypass valve (which is pretty much the same thing as a blow off), an emergency choke valve on the blower inlet or for the RAG engineering award, weak charge pipe joints so the pipe blows off.
 

·
Registered
1988 Honda CRX
Joined
·
6,676 Posts
A roots blower can pump enough pressure against a closed throttle to bend throttle plates and shafts. It's nothing to do with springs as the shaft should always be slightly off centre anyway so they blow closed, not blow open.

Also hopefully the belt would slip before the throttle plates fail, but who wants to bet their life on a charge pipe blowing off or a belt slipping.
 
1 - 4 of 4 Posts
Top