Where is the best place! To place turbo boost gauge pipes ,there are no place on carb (38 dgas) and wil brake boost pipe have a cause on the gauge if connected there? and can you connect the fuel pressure regulator on the same pipe??

Connect the gauge and rising-regulator hoses to the Intake Manifold. After the carburetor.

conect your boost gauge to the inlet manifold. conect the feed for the rising rate fuel pressure regulator to the pipe betwen the turbo and carb, it shouldn't see vacum, what type you using?

Don't connect the fuel pressure regulator boost reference line to the inlet manifold if it's a blowthrough! If you do, the vacuum at part throttle will drop fuel pressure possibly to the point you don't fill the fuel bowl at part throttle!

The other reason is that as air passes through the carb, through the venturi, it drops 1-2psi under boost conditions (and about 1.5in Hg under atmo non turbo apps, more for some older oem carb setups, and less like around 0.75in Hg for properly optimised competition engines). You _want_ it from befor the carb mouth, that way under boost you have 1-2psi more fuel pressure, which acts as extra insurance under boost. As soon as you go 'off' boost the pressure in the plumbing from turbo/supercharger outlet to carb mouth will not go above atmo, so it stiill runs the same off boost, and won't flood (as long as the supercharger has a bypass for part throttle, which I mentioned in the other thread about fuel pressure)..

For the boost pressure _guage_ I'd actually make a _very_ strong case for plumbing two fittings - 1 to somewhere between turbo/supercharger outlet and carb mouth, and the other to the inlet manifold. Then you can (once it's all setup) look at the boost pressure before and after the carb mouth. The boost pressure in the inlet is the 'true' boost pressure in all fairness, and representative of what you might expect as far as output. Recording that boost level across the rpm range, then switch the guage to the fitting before the carb mouth. This will (due to the venturi causing a pressure drop, which it needs to to meter fuel at all) show a higher pressure.

You should expect 2psi or so higher reading before the carb vs inlet manifold - pretty much no big deal. BUT if the pressure difference is 3-5psi (let alone if it's more than 5psi) then it's clear cut evidence that the carb is too small and acting as a restriction. This is bad on multiple fronts - 1, it's restricting how much air/fuel can get in there for any given pressure before the carb so overall less cylinder filling, and less power. 2. if the blower or turbo has to work harder to get the air/fuel in there it will cost more power (either at the crank to drive the blower, or through pumping losses of the pistons pushing against the turbine and it requiring more work to achieve the boost) 3. Since it's working harder, apart from pumping/mechanical losses, it's also going to heat the charge up more which means it's closer to detonation, and at higher temp less dense, so less power yet again.

Having the two boost guage takeoff points where you alternate plugging one off and running the other to the guage(heck even going as far as to run two gauges) can tell you a lot about the suitability of the carb, and whether you could have the cake and eat it too - and end up with better cylinder filling with less chance of detonation via carb size optimisation.

Thanks! jmac I do appreciate, now i no why my ute is always filling the cylinder ports ?