How accurate -->stock R32 boost guage?

[krzysiu]

your stock boost gauge may have a leak in the hose... mine had this problem and didnt read properly (not that i used it) but yeah, fsck the stock gauges, get an aftermarket one that reads over 7psi =)

The stock Meter does not measure the boost in Psi, its in Mhg(?) dont know what the conversion is

[brett33]

How does a larger exhaust explain the turbo running more boost than the actuator is rated at?

 

I don't think any one 'really' knows what the stock RB20DET actuator is rated at do we.

 

Its all speculation.

 

Even if we were to test it how would we determine it unless we were to get out hands on a bran spankin new actuator.

The fact is it does't matter what the actuator opening pressure is, its the actuator (assuming no controller) that sets maximum boost pressure not exhaust back pressure. But back pressure does affect total engine air/ gas flow. ie.more power.

[PTR33]

Boost pressure is just a result of the "restriction" that the engine causes to the compressor discharge flow volume/mass. more restriction for a given flow rate = higher boost pressure.

Extreme example take your 2530 and bolt it onto a 1.3 litre engine. It would probably be happy pumping 2 bar or more into a tiddler of an engine like that.

Now take the same 2530 and strap it on top of a 7 litre V8. At high revs it is quite possible that the V8 would be trying to suck air through the turbo because it was trying to swallow more air than the poor "little" turbo could pump.

P.S. I would hate to see the shaft speed in the second scenario!!

2530 is probably a little small for an RB25 if you want high power at the top end. 2835 would be better but the 2530 would have a hell of a mid-range.

[brett33]

Boost pressure is just a result of the "restriction" that the engine causes to the compressor discharge flow volume/mass.  more restriction for a given flow rate = higher boost pressure.  

 

Extreme example take your 2530 and bolt it onto a 1.3 litre engine. It would probably be happy pumping 2 bar or more into a tiddler of an engine like that.

 

Now take the same 2530 and strap it on top of a 7 litre V8. At high revs it is quite possible that the V8 would be trying to suck air through the turbo because it was trying to swallow more air than the poor "little" turbo could pump.  

 

P.S. I would hate to see the shaft speed in the second scenario!!

 

2530 is probably a little small for an RB25 if you want high power at the top end. 2835 would be better but the 2530 would have a hell of a mid-range.

Yeah mate you,re dead right, there seems to be the odd the sphincter of the universe spouting crap when, in there position they should know better. Nice too here from some knowelgable people.

[Cubes]

The fact is it does't matter what the actuator opening pressure is, its the actuator (assuming no controller) that sets maximum boost pressure not exhaust back pressure. But back pressure does affect total engine air/ gas flow. ie.more power.

Sorry Buddy...

Wasn't really a question.

I was trying to understand where PTR33 was coming from.

The stock dump may be a restrictive POS it aint gonna restrict it from getting to wastgate actuator opening pressure.

I wasn't thinking so much VE but more so turbine efficiency and how it directly relates to shaft speed which then relates to the turbo's airflow that relates to the pressure required for that airflow to enter the motor.

This is where the increase in boost comes from, better turbo efficiency.

What happens when you drop the exhaust from a car? Turbine efficiency is improved dramatically.

Dropping the exhaust from my RB30DET with the stock turbo & wastegate jammed all the way open saw boost hit ~10psi with possibly another .5-1psi more if it was rev'd harder.

Fit the exhaust back up, jam the wastegate open and it only saw 6.5psi by ~5000rpm.