rb20 wastegate actuator on rb25 turbo

[santorty]

i had an old rb20 turbo laying around and decided to throw the actuator on my rb25 turbo. since i think the stock psi on an rb20 is a bit higher than the 25. (something like 9-10psi?) it bolts right up, i just had to extend the vacuum line since the nipples are in different places. i only have a stock boost gauge so it's hard to tell the difference in boost levels, but it seems to be hitting about 550-600mmhg. which would be closer to 11-12 psi. is the extra boost from intake/exhaust mods, gauge inaccuracy, or some other factor i'm not considering? also wondering if the extra boost will be detrimental in any way as the car is basically bone stock in terms of drivetrain, electronics, etc etc.

all-in-all it seems like a pretty cheap/easy way to grab an extra 4psi.

oh, btw, the car is a 94 gts25t.

[Skym]

On two RB20DET wastegates we tested on bench (using boost gauge that's T'd into vacuum hoses that go to internal wastegate actuator bulb, carefully applying compressed air to vacuum hose until wastegate arm moved), both around 12psi. But they can be lower or higher than that. The range is 11.36psi-12.78psi for both manual and auto.

Podfilter is usually around +0.1 bar.
Dumppipe back exhaust around +0.2bar.

0.1 bar x 14.5psi = 1.45psi
0.2 bar x 14.5psi = 2.9psi

With R33 the stock ECU controls boost level (main, knock boost duty maps, look similar to ignition, fuel maps) via boost control solenoid in engine bay. As long as the engine doesn't go lean (use a wideband in exhaust to check), should be ok.