Turbo / Inlet manifold pressure

[superheat6k]

So in 2016 I fitted some lovely turbo boost pressure gauges when I refurbished the dash panel. So today I finally installed the senders. Both gauges seem to work and the pressure initially drops then as I increase the revs the manifold pressure does increase a tad, bit this is at no load.

So assuming I am underway and under decent power, what manifold pressures should I expect to see ?

Cummins 6BT5.9M.

Thanks.

 

[burgundyben]

Manual says inlet manifold pressure 49 inches of mercury, which I believe to be 24 psi.

I assume that is at full load.

 

[Portofino]

You lot are wearing me out
Here’s live data 1.9 bar is 27.5 psi so inline with ^^^

View attachment 75673

 

[vas]

1.9-2.0bar here at planning speed, nothing or .2bar at 7kn, 6.7lt straight six ivecos

V.

 

[superheat6k]

Manual says inlet manifold pressure 49 inches of mercury, which I believe to be 24 psi.

I assume that is at full load.

Thanks Ben. I suppose I could have read the manual too !

I am sure I read somewhere the engines can be balanced on the manifold pressure. Is that correct ?

 

[Venatrix]

I used to run my 6.354 Perkins so that the boost pressure was identical. The revs were about 100rpm apart.
Can't remember who told me it was a good idea.

 

[Higgo]

Superheat, you said you have the Cummins 6BT5.9M. Are these the 330/370 HP versions with raw water aftercoolers? If so, your boost pressure is heavily dependent on the cleanliness of the aftercooler core fins/plates. If one core is more clogged than the other, that will affect engine performance and boost pressure. So trying to balance engines on boost pressure can be problematic.

I have the 370hp versions and at WOT at 3000 rpm, and clean aftercoolers, boost vacuum pressure is around 23-24 psi. But they have to be under load, not at the dock, otherwise any readings will be spurious. If you do have the 330/370 versions, are the a/c cores clean?? When we're they last removed and cleaned? The lower HP 6bta versions have different cooling systems but the concepts are the same.

You said you have senders connected to your gauges. My setup is pretty simple with a vacuum tube connections on the inlet manifolds and the tube running to the flybridge dual boost gauge.



Hope it helps. Cheers

 

[superheat6k]

Superheat, you said you have the Cummins 6BT5.9M. Are these the 330/370 HP versions with raw water aftercoolers? If so, your boost pressure is heavily dependent on the cleanliness of the aftercooler core fins/plates. If one core is more clogged than the other, that will affect engine performance and boost pressure. So trying to balance engines on boost pressure can be problematic.

I have the 370hp versions and at WOT at 3000 rpm, and clean aftercoolers, boost vacuum pressure is around 23-24 psi. But they have to be under load, not at the dock, otherwise any readings will be spurious. If you do have the 330/370 versions, are the a/c cores clean?? When we're they last removed and cleaned? The lower HP 6bta versions have different cooling systems but the concepts are the same.

You said you have senders connected to your gauges. My setup is pretty simple with a vacuum tube connections on the inlet manifolds and the tube running to the flybridge dual boost gauge.

View attachment 75675

Hope it helps. Cheers

Mine are 210 HP 6BT not 6BTA so no after coolers.

I bought the gauges from Ebay in 2016 when I was refurbishing the dash panel. They came with separate senders to which the tube connects to the manifold. I wasn't sure where to fit them until I found recently reference to some 1/8" NPT plugs in the inlet manifold, so I bought a couple of hose fittings and after the recent shenanigans with my rewire, and then heater install, I finally fitted the adaptors and wired in the senders yesterday. At the berth in idle they show a slight vacuum which is to be expected, then as I rev up with no load they start to move to positive pressure ~ 1800 RPM. I will need to take the boat out to see how the turbos really behave under a decent load.

Next week I am concluding another long started yet to be finished task of installing vacuum gauges on the outlet from the primary fuel filters. I re-plumbed the entire fuel system in 2017, and provided take off points to affix the capillary tubes to the vacuum gauges to on the fuel filter outlets. These don't have senders, so the vacuum tubes will be routed up to the dash panel. Main thing here is to get the panel drilling as accurate as I can so the new gauges line up with those already there - square and evenly spaced, and I know less than 1mm out will be noticeable. I expect the measuring and marking of the hole centres will likely be the longest task.

 

[Higgo]

Got it, thanks! You're certainly going all in with vacuum gauges for the fuel filters up to the dash. These gauges are a good idea, and I installed them on my primary Parker filter head (without a gauge tube) but think about whether they are worth the dash install effort. I can lift a stair hatch and see mine as needed, particularly at the end of the day or cruise. Typically the pressures build gradually.

I guess you also have EGT gauges and I monitor mine through a cruise with a high temp alarm module as well. If real estate was an issue, for me they would be a higher priority on the dash than fuel filters gauges.

I know what you mean about getting the holes right. I've borrowed from my neighbor a hand ram type large punch which makes things easier.

Have fun with it. Cheers

 

[superheat6k]

Got it, thanks! You're certainly going all in with vacuum gauges for the fuel filters up to the dash. These gauges are a good idea, and I installed them on my primary Parker filter head (without a gauge tube) but think about whether they are worth the dash install effort. I can lift a stair hatch and see mine as needed, particularly at the end of the day or cruise. Typically the pressures build gradually.

I guess you also have EGT gauges and I monitor mine through a cruise with a high temp alarm module as well. If real estate was an issue, for me they would be a higher priority on the dash than fuel filters gauges.

I know what you mean about getting the holes right. I've borrowed from my neighbor a hand ram type large punch which makes things easier.

Have fun with it. Cheers

It's a teak faced ply panel so a conventional hole saw is simpler.

I am averse to paying too much attention to exhaust gas temperatures. When I was in the Mob the older steam engineers on the newer Gas Turbine Type 42 Destroyers got carried away with the importance of EGT from each cylinder on the 1 MW diesel generators, to the point they started tweaking the individual fuel pump elements to each cylinder to try to get them balanced within something like 20oC. They ended up completely wrecking four Paxman Ventura engines as a result of their shenanigans. The same engines would run a million miles on the High Speed Trains, they just couldn't leave them alone I reckon through boredom, but as I was only a baby stoker at the time my view didn't count for much, mind you doesn't count for much more now, I just know that when "engineer's" start concentrating on exhaust temperatures its time to find another dial to watch.