boost controller

[madwoody]

Have a couple of things on my mind.

Alot of people put restrictor rings in a j spec supra why is this? the reason i ask is if you have the said ring in the spool up time on the turbos goes down (well it does on mine).

so if you have a boost controller installed does it

1 control the boost by operating valves to control the boost at a set presure

2 limit the high boost by operating a valves so as to not have to much presure in the system

3 limit the low boost some how

i've asked these questions because i can't understand why we put a restrictor ring in, my car has not had one in for about three years now i've been messing around with the apexi valve which because of the size it makes it a restrictor ring of about 1.25 bar

Just wondered if there was anyone out there who knows (not thinks they know or was told by someone else) that you need a restrictor ring in

[Gambit]

By default the cats restrict the flow of exhaust gasses through the exhaust.
The turbos run of the exhaust gasses before the gasses pass through the exhaust, so if the gasses are allowed to pass through the exhaust as they are when de catted and after market exhaust fitted ie. unrestricted, they are effectively passing through the turbos at a greater than stock speed, thus spinning the turbos faster than stock and increasing boost.

The restrictor ring is fitted to the exhaust to slow the flow of the gasses, thus slowing the gasses passing through the turbos and stopping the turbos from spinning dangerously out of control.

I can't comment on the boost controller as I've never used one, I'm just laying out the job of the RR.

[madwoody]

hi gambit
just questioning how you know it spins (dangerously out of control.) not saying your wrong but i'm trying to get to the bottom of why have a r ring in, for that point why fit an after market exhaust on if your going to restrict it, might as well just knock the insides out of standard second cat and be in the same postion

its just my car has not got a r ring in it over boosts (i no this is bad fuel cut and everything) every now and then but only when the air temperature is very cold but the spool up time is so much quicker without it(i think the ceramic blades on jap spec help)

[Martin F]

The turbo will spool quicker and faster because of the pressure differential across the turbine blades being greater than when the cats are fitted.

I'm not sure if this is the best (simplified) way to explain it but i'll give it a go. If the exhaust gases coming out of the exhaust port exert say 30psi of pressure on the turbine blades and there is nothing beyond the turbine blades then the pressure differential across the blades is 30psi, and hence they will spin at a rate relative to that differential.

If you now put a restriction on the other side of the turbine blades (cat, restrictor ring, small bore exhaust, etc) then a certain amount of back pressure will be present as the gasses can't exit as quickly as they did previously. Lets say this restriction creates 3psi of back pressure, now the differential across the blades will only be 27psi so therefore the blades will not spool up as quick or have as fast final speed.

The wastegate works in a fashion where it diverts gasses away from the input side of the turbine blade, thus reducing the pressure.

Fitting a restrictor ring to a Jap spec car is indeed a kludge, as you are compensating for the fact that Jap spec wastegates can not divert enough gas away at high rpm, so by putting a restriction in the exhaust you are reducing the pressure differential and limiting the max pressure differential possible.

But (aligned with what you are saying) this reduced pressure differential will be there at all points of spool up, so a car without a restrictor ring\restriction will always spool quicker than one with. However I suspect in most cases the difference is quite marginal.

HTH