Nissan Titan XD Forum banner

1 - 5 of 5 Posts

·
Registered User
2019 Titan XD Pro4x Cummins
Joined
·
665 Posts
Avoid the comments after the article. They will make your brain hurt.
You're right. The "I don't see any clever engineering part" Gave me a good laugh though. The ISV is going to be one of, if not the most advanced and simple(a hard combination to achieve!) diesel engines on the market.
 

·
Registered User
Joined
·
340 Posts
As always stupid is the lowest common denominator.

Loved this then and still love it now...

The two-stage bit means there are two turbochargers plumbed in sequence, so that they both feed pressurized intake air to all eight cylinders. Don’t call it a twin-turbo setup, though, because as with all sequential arrangements, these turbochargers are significantly different in size. (Twin turbos are the same size, with each one feeding half the engine’s cylinders.) The smaller of the two turbos provides boost at low engines speeds, where the lighter compressor and turbine spin up to speed quicker to reduce lag. However, at higher revs and engine load, when the engine is pumping more air, the smaller turbine and compressor begin to reach their limits. Instead of increasing power, they become restrictions in both the intake and exhaust streams, choking the intake supply and increasing back pressure in the exhaust. This is when the larger turbocharger takes over, raising the overall boost pressure and peak power output.
 

·
Registered User
2019 Titan XD Pro4x Cummins
Joined
·
665 Posts
Turbochargers can be thought of in mathematical terms as multiplication devices. Input pressure multiplied by ratio of desired output pressure, or pressure ratio.

Air is compressible and because of that the compressor doesn't care what the input pressure is and happily multiplies it. In a properly setup compound system, the high pressure turbo can be made to do work right to the end of the rpm range. The only reason Cummins lets the low pressure turbo take over, is the total desired pressure ratio is within the efficiency range of the low pressure turbo.

Another factor is that the high pressure turbo increases mass air flow enough at lower RPMs to actually be able to spool the low pressure turbo.
 
1 - 5 of 5 Posts
Top