When to measure max boost?

[reb78]

As above really. Am i right in thinking that max boost should be measured with the engine under load at highish revs - say hi revs 3rd/4th running up a slope?

My engine is a defender 200tdi (110csw). I have upped the boost to around 1bar (from the factory 0.8bar). In 3rd, the max boost under load (on a reasonable slope in the motorway) is just under 1 bar, in 4th, 4th+OD and 5th it is dead on 1 bar on the same slope under load. If i leave it in 4th+OD or 5th after flattening out at the top of the slope, the boost will occasionally rise to just under 1.1bar (that is ragging it a bit though, so not desirable revs at all). Does this sound setup ok to you all or should i knock it back a bit?

[Lars L]

Sounds OK to me, but that's me. Mine goes to 1,2 bar uphill with the pedal firmly planted at 100 km/h.

[Aragorn]

as lars says, if it was mine i'd be looking at ~1.2bar.

1Bar is perfectly safe.

[reb78]

Whats the risk with overdoing it? Blown headgasket, overstressing the engine and shortening engine life?

I also have very little smoke - virtually none at all under full throttle now the boost is up. Fuelling via the diaphragm is at max. I'm wondering whether to turn the pump up a little now. Probably wont as i'm fairly happy with it and dont really want to drive it much faster as the fuel will just dissappear - although having said that i seem to get 25mpg however i drive it at the moment.

[Aragorn]

If your not uping the fuelling to match the boost theres very little risk at all, unless you went particularly silly.

Head gasket will be under slightly more stress.

More fuel is what creates the cylinder pressures, so thats more risky, but more fuel and more boost can acutally be safer than just fuel alone, as the extra air helps the fuel to burn more completely and drops the EGT's.

Ideally you want a bit of smoke when off boost, which helps get the turbo moving, normal accelleration should be relatively smoke-free. Full throttle again you want a slight haze of smoke, like you see from most modern TurboDervs as thats roughly the point your making good power without risking silly EGT's

There are different adjustments on the pump for each of these, i'd be tempted to up the off boost fuelling a little if you havent already and give the max fuel screw a tiny tweak to get a little smoke on full throttle.

You'll only use more fuel if you use the power, but the power is always nice to have on tap even if you dont use it all the time.