Diesel rednecks and compressor maps. He351VE related.

[me2]

I think some of you will find content in this thread interesting.

I also think you'll recognize a whole bunch of really, really bad turbo science. Feel free to step into that foray and enlighten people if you will.

This is the same crew that things you need a 150 GPM fuel pump to feed a 400 HP engine. I kid you not.

Big singles and towing - Page 15 - Dodge Cummins Diesel Forum

FWIW, I'd post this in turbo tech, but I'm a newbie here and blocked from doing so.

 

[knochgoon24]

As interested as I am in the HE351ve, reading that thread is painful. It look 10 posts before the "20psi != 20psi" argument to come up.

They are a bit lost on some of the finer details on reading info from compressor maps.

Notes:
-The VGT has no effect on the compressor map. The HE351ve/cw uses a 7-blade HX40 wheel. You can use those compressor maps.
-The turbo won't make 45psi if there's not enough energy in the exhaust to drive the compressor. Just because it's plotted on the map doesn't mean it's possible.
-The straight surge line on the one "HE351ve" compressor map is from the map being plotted with only a few data points. It only gives the general shape of the map. It has nothing to do with the VGT.
-Turbo's don't suck in air. Their job is to push the air out of the way so more air can be blown in to replace it. Nothing sucks, everything blows. That's why they call it a blowjob. Remember that kids.
-Going with a bigger A/R on the turbine side does a lot more to improve peak VE than they think. Garrett makes some turbine maps publicly available. Do a Google search.

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Yep. That's a 40% increase in flow by switching from a 0.63A/R to a 1.06A/R on the GT35R.

 

[me2]

-The VGT has no effect on the compressor map. The HE351ve/cw uses a 7-blade HX40 wheel. You can use those compressor maps.

There are several wheels used in various He351VEs, including at least one with a 56mm.

-The straight surge line on the one "HE351ve" compressor map is from the map being plotted with only a few data points. It only gives the general shape of the map. It has nothing to do with the VGT.

The Cummins ECM actually runs it like that. They don't show the higher boost levels on the map because it would be misrepresentative of what happens when its in the truck. A birdie told me.

Otherwise I agree with everything you've said.

 

[LandSpeed-DSM]

Wow. There is so much fail in that thread.

This SuperDuty guy doesn't seem to fully understand how to read a compressor map, or how turbochargers work in general.

Never mind talking about the turbine side of the equation which is what will be the main factor in determining the boost threshold he has his panties in a knot over.

And OP they do need a ton of fuel, because 400whp on a 6.7L diesel that only turns 3k rpm is not the same as 400whp on a 2.0L gasser that spins to 7.5k.

 

[me2]

And OP they do need a ton of fuel, because 400whp on a 6.7L diesel that only turns 3k rpm is not the same as 400whp on a 2.0L gasser that spins to 7.5k.

You realize that diesels are more fuel efficient than gassers ? Therefore the fuel pump volume required will be less ?

How big is the fuel pump on your 400 HP gasser ?

 

[LandSpeed-DSM]

Yes I am quite well aware that diesels are more thermally efficient than their gas counterparts, I had a 5.9CR.

You could get away with a simple walbro 255lph on a gasser, obviously. But diesels are a different beast.

More fuel is more power.

 

[me2]

I'm afraid to do it, but I'll do it anyway.

What does the flow rate of the lift pump have to do with the power of a diesel engine ?

 

[LandSpeed-DSM]

On a diesel you can turn the boost up to cram a greater airmass through the head till the headgasket fails, the head lifts or you window the block.. You need the lift pump to be able to feed the pump that pressurizes the rail so you don't drain the rail and cause damage.

Which is why 100-150gph pumps are so common.

It is not unusual to see 50+psi on those diesels because of the way they operate. They are not limited by a detonation prone fuel. Combustion doesn't occur till the fuel is injected.

So it would stand to reason that you would always want an excess of fuel, hence the big lift pumps.

This is why compound setups (or twins as they call them) are so common on diesels. Atleast on my 12v... in order to get the massflow I need to make the power I wanted, I had to run ridiculous PRs and make the air denser because volume flow was restricted by the head/cams/redline.

In your example, If I am making 400rwhp @ 3000rpm, I am also making ~700rwtq but still needed say a 62mm or 66mm compressor turbo with a large hotside humming along at for instance 35psi to do so.

Because in this case just because I am moving say ~70lb/min air flow, doesn't mean I am going to be making 675+ whp but still need a ton of fuel.

 

[knochgoon24]

There are several wheels used in various He351VEs, including at least one with a 56mm.

That's the first time I've heard that. Any details? Like what years/motors have what?

The Cummins ECM actually runs it like that. They don't show the higher boost levels on the map because it would be misrepresentative of what happens when its in the truck. A birdie told me.

Otherwise I agree with everything you've said.

I'm not surprised that the ECM runs it like that. That's the great thing about the VGT; it helps keep the turbo in a more efficient range. Open the A/R on the turbine once you start to spool and suddenly, you start shifting right on the compressor maps. It would be interesting to put that graph over a HX40 (or other appropriate non VGT comp wheel) to see where that line would run through.

I need to speak with my birdie and see if he'll leak any details. Cummins is sponsoring the PSU FSAE team, so I'll get to meet up with a few other Cummins/Holset guys in the spring when they bring their test rig to put the FASE car through it's paces.

 

[blackrosenova40]

Lift pumps dont create high pressure, lift pumps and or transfer pumps, create low pressure to transfer to the high pressure pump, which then pressurizes the high pressure rail, if we are talking about a common rail system. Normally id say the low pressure side can be between 35-120 psi, depending on engine and fuel system. The high pressure side on a common rail can exceed 30,000psi, and injectors can fire I believe up to six times per compression stroke, but I think cummins only uses five.

On a diesel you can turn the boost up to cram a greater airmass through the head till the headgasket fails, the head lifts or you window the block.. You need the lift pump to be able to feed the pump that pressurizes the rail so you don't drain the rail and cause damage.

Which is why 100-150gph pumps are so common.

It is not unusual to see 50+psi on those diesels because of the way they operate. They are not limited by a detonation prone fuel. Combustion doesn't occur till the fuel is injected.

So it would stand to reason that you would always want an excess of fuel, hence the big lift pumps.

This is why compound setups (or twins as they call them) are so common on diesels. Atleast on my 12v... in order to get the massflow I need to make the power I wanted, I had to run ridiculous PRs and make the air denser because volume flow was restricted by the head/cams/redline.

In your example, If I am making 400rwhp @ 3000rpm, I am also making ~700rwtq but still needed say a 62mm or 66mm compressor turbo with a large hotside humming along at for instance 35psi to do so.

Because in this case just because I am moving say ~70lb/min air flow, doesn't mean I am going to be making 675+ whp but still need a ton of fuel.

 

[me2]

That's the first time I've heard that. Any details? Like what years/motors have what?

I don't know what comes from what. I just know that 56s have been found as cores.

 

[knochgoon24]

Hmmmm....

I'll have to look into that then. Do you know if they're still a 7-blade design or does it use an 8? Or both? At that point, if it uses a 56mm wheel, then it's more than likely the HX35 wheel.

I'd almost want to find one of those over the 60mm ones. I don't plan on using the full potential of a compressor that large for a while.

 

[LandSpeed-DSM]

Lift pumps dont create high pressure, lift pumps and or transfer pumps, create low pressure to transfer to the high pressure pump, which then pressurizes the high pressure rail, if we are talking about a common rail system. Normally id say the low pressure side can be between 35-120 psi, depending on engine and fuel system. The high pressure side on a common rail can exceed 30,000psi, and injectors can fire I believe up to six times per compression stroke, but I think cummins only uses five.

Uh.. try reading the second line of my post which you quoted..

In case you missed it again I state in no uncertain terms:

You need the lift pump to be able to feed the pump that pressurizes the rail

 

[JusMX141]

Every 351VGT I've ever disassembled had the 4035380 7-blade HX40 compressor. These were all confirmed to have been removed from Dodge trucks....perhaps the other cores that were found were used on a completely different platform.

 

[bastarddsm]

Every 351VGT I've ever disassembled had the 4035380 7-blade HX40 compressor. These were all confirmed to have been removed from Dodge trucks....perhaps the other cores that were found were used on a completely different platform.

Wouldn't doubt that a bit. Probably something ag related. I know 2012my John Deere Combines have a BW vgt turbo on them...So I'm sure the red side is headed that way too.

 

[blackrosenova40]

My bad, misread.

Uh.. try reading the second line of my post which you quoted..

In case you missed it again I state in no uncertain terms:

 

[bastarddsm]

Uh.. try reading the second line of my post which you quoted..

In case you missed it again I state in no uncertain terms:

Not that it matters to the context of this thread, but on the CP3 pumps used on common rail cummins and duramax's increaseing the feed pressure to around 100psi up from the ~10 on a cummins and 0 on a duramax will increase the output volume by about 20%. It causes fuel to flow in a relief port and actually increases the effective piston stroke.

We use a hilborn pump to supply 100psi to our 3 CP3's. We run about 34000psi rail pressure, any more and the injectors become inefficient. fyi stock commonrail shit is 18-20000psi. The high pressure pop off valve is at 25k, and the rail pressure sensor is only for 1800bar (2600psi)

 

[knochgoon24]

As far as the 56mm wheel goes, from what I've found so far, it seems that the confusion comes from there being a 56mm 6-blade HX40 from a Volvo application and the 56mm 7-blade HX35 wheel on the HE341cw, which otherwise closely resembles the HE351cw; same turbine housing, turbine wheel, and a similar compressor cover. The HE351ve all seem to use the Hx40 60mm 7-blade.

 

[me2]

Every 351VGT I've ever disassembled had the 4035380 7-blade HX40 compressor. These were all confirmed to have been removed from Dodge trucks....perhaps the other cores that were found were used on a completely different platform.

The industrial 6.7s come in a wide variety of power and torque ratings and use the HE351VE as well. The Industrial 6.7s aren't nearly as common in numbers as the Dodge 6.7 is.

Not that it matters to the context of this thread, but on the CP3 pumps used on common rail cummins and duramax's increaseing the feed pressure to around 100psi up from the ~10 on a cummins and 0 on a duramax will increase the output volume by about 20%. It causes fuel to flow in a relief port and actually increases the effective piston stroke.

We use a hilborn pump to supply 100psi to our 3 CP3's. We run about 34000psi rail pressure, any more and the injectors become inefficient. fyi stock commonrail shit is 18-20000psi. The high pressure pop off valve is at 25k, and the rail pressure sensor is only for 1800bar (2600psi)

I understand using a 100 PSI pump to feed CP3s to increase their output.

I don't understand using a 10 PSI 150 GPM pump to feed a CP3 on an engine that burns less than 20 GPH.

 

[LandSpeed-DSM]

Well lets look at this for a minute, at a mere 3000rpm and only 375HP SAE Net at the flywheel they are consuming about 20.x gallons per hour. Which is I am guessing where you got that number for the QSBs.

Most of the folks stepping up to the 95 and 150GPH pumps are going to be using a 4000rpm or greater governor and shooting for north of 500rwhp.

The stock pumps clearly are not designed for that, and as with all fuel systems you never want to get the bare minimum to do the job.

Also those 95gph pumps are only flowing 95gph @ 0psi. At 10psi they are closer to 72gph. Same goes for the 150's.

A good number of people on these newer CP3 are running the lift pump to as much 30-40psi or more, where flow has dropped off considerably. Obviously they still want some overhead on the pump, so it is not running at full capacity constantly.

The excess fuel is bypassed anyways and used to cool the injection pump as well as remove air from the fuel.