Drive Pressure Extrapolation

[XXXLR8R]

I need some SOTP engineering on this one.

How much less would the drive pressure be on a turbocharger mounted 36" away from the exhaust ports as opposed to the same one mounted within 12" of the exhaust ports?

We observe 35psig drive pressure (TIP) on a Cummins 5.9L inline 6 cylinder diesel engine - using a relatively quick-spooling Holset (HY35) turbo - to produce 30psig compressor boost. RPMs can be 2-3K with pre-turbo EGT in the 1-1.5K*F range.
Holset is mounted directly to cast iron exhaust manifold.

For simplicity, IF an identical amount of expansion energy was available at the exhaust ports' exit of an 8.0L V-10 spark-ignition with 36" long primary tubed 304SS headers, what would be the expected TIP if the same Holsets (one on each bank, obviously!) were mounted on the end of the collectors?

Certainly, there would be less expansion energy available, and I'm presuming enough will still be present to generate the 10psig of boost we're looking for... but would like to get a ballpark idea of what may or not be required in the wastegate department.

TIA

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[dcasto]

The factors are: pressure drop in the line and temperature lose in the line. If you put a 1" exhaust, noway. I'd guess a 5" insulated line would get there, but do the pressure drop and estimated temperature drop. The same with the air, the longer the air intake the less pressure at the cylinder.

 

[XXXLR8R]

Assume no post-turbo exhaust (not necessary anyway).

Don't figure any passive or active thermal management - just what's inherent in the denoted material; the difference in K-value between the cast iron manifold and SS tube headers is negligible, however the effective heat sink and therefore thermal hysteris between the two may well be significant. Manifold is ~ 1/2" thick, headers are .065"

Please ignore compressor-side boost effects - they are known for a given drive pressure. BTW - in forced induction applications, the reduction of intake flow in terms of velocity & volume - and thus pressure - is far less (essentially insignificant) than in normally aspirated engines.

Also, no point in dwelling on differences between Otto or Diesel cycle engines - just think of this as a gas turbine efficiency query.

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[XXXLR8R]

... hysteresis, that is....

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[tha89sx]

pre turbo egt 1500 F

your running too much fuel for the hy35

efficiency zone ends aroun 28psi. but can comfortably be run to 32 with deminished returns.

 

[XXXLR8R]

Sorry, I mis-posted above... turbo is HE351, not HY35!

Correct about the boost limitations of the older turbo - the new Holsets have a pretty good map up to the high 30s, and still make plenty (if inefficient) power through the high 40s. Also, the better piston metallurgy and oil jet crown cooling of the HPCRs allow much higher EGTs - 1400*F indefinitely, short excursions to 1600*F and spikes over 1800*F.

... SHHH! In our world, there's no such thing as too much #2

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