B-series turbocharger differences

[Cato Jensen]

Greetings! I’m new to this forum, but have already had lots of help from the information available on this site. Thanks for providing sbmar.com, Tony!

My 29ft boat is powered with a cpl 1570 220hp/2500rpm engine coupled to a Stern Powr 1000 outdrive. I’m having issues getting on plane and am currently working through the setup, eliminating any potential problems. The engine has been modified a little and is currently using a SWAC instead of the tombstone cooler. The after cooler may possibly be a little on the small end. I’ve got a EGT-gauge, but the readings are fluctuating and I don’t trust it fully. Generally, EGT seem to be on the high side and manifold pressure on the low side. Exhaust is wet, 3,5 to 5 inches, temporarily without a muffler. The ND pump has been spill port timed to 22 degrees.

I realize there were several turbocharger variants used on the B-series. My turbo is a 3538777 with a 52mm inducer compressor. Other engines use 60mm inducer compressors and also different compressor covers. The QSB’s seem to use a 13cm2 exhaust housing, while the B-series use a 16cm2.

I’ve also seen some comments about the early turbos providing less boost in the midrange, thereby being susceptible to overload? Hopefully someone could explain what to look for? I’ll appreciate any input.

Thanks,
Cato Jensen
Stavanger, Norway.

Topic

[Tony Athens]

Obviously, Test C was the best for overall performance and engine loading.. If the engine is in good shape and “well gauged” and alarm protected, the cooling system is up to spec, then running with the Test C prop at 2300 to maybe 2400 RPM should be fine as long as the test weight of the boat does not change.

Tony

[Cato Jensen]

It’s been a while, but i finally got around to doing some trials. As for the environoment, Tony. It’s rain – we get lots of rain here on the Norwegian coast.

I didn’t pull the exhaust riser, but i did check the bearings of the turbo. Thrust play is more than I prefer.

From what I can tell from the tests, my old propeller was probably cavitating going on plane. Also, the aftercooler is probably a little on the small side, I get a high pitched whining noise with RPMs over 2400. That whine disappeared when I bypassed the aftercooler.

I did 4 trials. The results are in the attachments. Please note that the fuel meter has limited accuracy (and capacity). But it’ll give you an idea.
Test A – My old propeller 19×16.5. With aftercooler.
Test B – My old propeller 19×16.5. Bypassed aftercooler.
Test C – New/used propeller 19×17. With aftercooler.
Test D – Steel propeller 22×19. With aftercooler.

The steel propeller was to heavy to get on plane with and i got lots of black smoke.

[Tony Athens]

With all the of the non-factory modifications to the engine, plus you are furnishing zero “gauge” numbers on your IMT in & out of the aftercooler, pressure readings in and out, exhaust pressure numbers, or EGT numbers, I really have no clue what to say or what to suggest.. Trying to hot rod an engine has never been my forte.

As to you your exhaust side outlet on the turbo–Just remove the riser and take a pic of what is inside.

AS to the “environment” your engine seems to be operating in–I hope that is not saltwater..

Tony

[Cato Jensen]

Pictures from June. Dry exhaust section is 3.5″, wet section is 5″. Hosing on intake is 2.5″.

[Tony Athens]

PICTURES!

[Cato Jensen]

Thanks! I am away for the weekend, but i’ll record better numbers for EGT after I return. I’m thinking of bypassing the swac for comparison.
I cannot guarantee that the turbo has newer been exposed to water. It’s a repower by PO and i never saw the previous installation of this engine. It was used, and from an commercial boat with gear.
Exhaust elbow is new, previous was no good design.
Maybe I’ll pull the turbo and inspect the exhaust housing.

[Tony Athens]

Like Rob said———-We need to “see” what you have going on………..Anytime I hear “outdrive”, I think water into the turbo..That just about always says low boost, high EGT…

What are those numbers?

Any dark smoke?

Post really good pics of all..

Tony

[Rob Schepis]

Is the aftercooler a Cummins SWAC ?

How about some pictures of your engines and setup ?

Are you hitting rated WOT + 3 to 5% ?

[Author]

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