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Look, I was simply showing an example of how wastegating can reduce drive pressure and increase efficiency of a turbo setup. My original comment was a simple alternate solution to an issue brought up by the OP concerning the secondary turbo he was considering using in his twin setup. For some reason you took offense to my ALTERNATE SOLUTION.
I wasn't arguing that you were wrong. I wasn't talking about completely bypassing the secondary turbo. Just using a wastegate to divert some of the exhaust energy around the turbine to prevent an excessive amount of restriction. Routing the "wasted" exhaust energy into the intermediate pipe helps to recover that energy rather than dumping it to the atmosphere. The primary still operates at around 2.5-2.8:1 pressure ratio, and the secondary around 2:1, generally resulting in measured total boost of about 65 PSI. I use the wastegate to help fine tune the drive pressure and get the boost/drive pressure ratio as close to 1:1 as possible without significant performance loss.
In a perfect world spending thousands of dollars on different turbos to presicely match the application would be ideal, I agree. I don't usually have the luxury of custom designing a turbo setup to perfectly match the engine. By the time I see them the turbos are already there, but for multiple reasons the system is not performing as it should or is expected to. So I diagnose the problems and come up with solutions to not have to completely re-invent the wheel to come up with compromise that is acceptable to the customer. On some occasions I can make recommendations and help my customers decide on what compromises they are willing to make with a kit design. There is too many variables beyond the turbos themselves to list out examples. What I do know is I have a very good track record and reputation of improving the overall drivability and usability of theses setups.
Clearly you have what I assume is an engineering back ground based on your methodology. Good for you. I am not going to have a continuing pissing match with you over this.
The setup I proposed already uses wastegates on both turbines. 65psi is not enough to deliver the required air-flow that 90psi does.

 

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Discussion Starter · #22 ·
Thanks dustinf and Dougal for your input.

Anyway, I got a HE400WG with assembly number 5603225 in hand. I'm told its identical to assembly number 3783070. It's details are:

Compressor
Wheel - 7+7 blade
Inducer - 58mm
Exducer - 85mm

Turbine
Wheel - 10 blade
Exducer - 60mm
Inducer - 76mm
Housing size - 13cm2

Initial look shows I do have enough space to fit it in but will be a good 12 months before I get to it. Will post results when done.
 

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The setup I proposed already uses wastegates on both turbines. 65psi is not enough to deliver the required air-flow that 90psi does.

According to this calculator 90 PSI is pretty excessive for 500 HP. But I'm sure they're wrong too.
Result
Compressor Properties
Intercooler Properties
Engine Properties
Location Properties
Intake Air Tempature82Deg F
27.8Celsius
Altitude (feet above sea level)500Feet
(PSI barometric pressure)14.43PSI
Engine Displacement4.5Litres
274.61(Cubic Inch)
Engine Volumetric Efficiency95%
Air Filter Pressure Loss0.5PSI
Engine Speed3000RPM
Boost Pressure (Gauge)65PSI
Intercooler Effectiveness85%
Intercooler Pressure Loss4PSI
Compressor Efficiency65%
Flow Rate Required1076CFM
Air Flow Rate Required77.85lb/min
Engine HP Estimated419 - 559HP
Compressor Wheel Size Estimated62.8 - 69.1mm

 

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According to this calculator 90 PSI is pretty excessive for 500 HP. But I'm sure they're wrong too.
Location Properties
Engine Properties
Intercooler Properties
Compressor Properties
Result
Intake Air Tempature82Deg F
27.8Celsius
Altitude (feet above sea level)500Feet
(PSI barometric pressure)14.43PSI
Engine Displacement4.5Litres
274.61(Cubic Inch)
Engine Volumetric Efficiency95%
Air Filter Pressure Loss0.5PSI
Engine Speed3000RPM
Boost Pressure (Gauge)65PSI
Intercooler Effectiveness85%
Intercooler Pressure Loss4PSI
Compressor Efficiency65%
Flow Rate Required1076CFM
Air Flow Rate Required77.85lb/min
Engine HP Estimated419 - 559HP
Compressor Wheel Size Estimated62.8 - 69.1mm

Yes it's wrong. Intake temps too low, capacity too high (my example is for a 3.9L, I haven't spent the required 8 hours to recalculate for 4.5L), VE too high, intercooler effectiveness too high and they've completely ignored turbine side drive power.

My numbers:
3.9 litres
HX30 6cm turbine
HX40 16cm turbine
390kw (527hp) net power.
1358Nm (1001 Ft-lb).
2800rpm (naturally occuring peak).
230g/kwh BSFC
80% VE.
PR 2.6 on small turbo
PR 2.8 on big turbo.
Total boost 92.3psi (gauge)
Comp efficiency small 75%
Comp efficiency large 77%
10% heat loss between compressors.
60% heat loss in main intercooler.
Large turbo discharge temp 154C.
Small turbo intake temp 140C.
Small turbo outlet temp 309C
Intercooler outlet temp 135C
Density ratio 5.22
Corrected flow on small compressor 24 lb/min.
Total flow 0.38m^3/s, 805 CFM, 60.57lb/min
Fuelling 320 cc/1000 shots.
Small turbo shaft power 77.5kw.
Big turbo shaft power 61.5kw.
Intercooler heat loss 79.7kw.
Small turbine efficiency 70%
Small turbine wastegate flow 5%.
Large turbine efficiency 70%
Large turbine wastegate flow 17%
Exhaust outlet pressure 115kPa (absolute)
Drive pressure 92.6psi.
Intermediate drive pressure 29.3psi.
Delta P -0.2psi (exhaust is 0.2psi higher than intake).
Gross power - same as net power.
 

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FWIW in the last 8 or 10 years I have personally built 2 4BT's relying on Dougals calculations one a single using the He221 when it was more or less unproven on a 4BT the second a hx30/Wh1c compound build both preformed as predicted, this was in a heavy pickup that was required to work for a living in the Southwest US where temps range from 10* to over 110* and from sea level to north of 8,000'. Many others have reported the same results that I have had with Dougals calcs. were I to do another build especially an unproven combination I would not even consider acquiring parts without bouncing the concept of of Dougal first, been there and done that before the 221 and it was not the least cost effective to just experiment with hard parts......$.02
 
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FWIW in the last 8 or 10 years I have personally built 2 4BT's relying on Dougals calculations one a single using the He221 when it was more or less unproven on a 4BT the second a hx30/Wh1c compound build both preformed as predicted, this was in a heavy pickup that was required to work for a living in the Southwest US where temps range from 10* to over 110* and from sea level to north of 8,000'. Many others have reported the same results that I have had with Dougals calcs. were I to do another build especially an unproven combination I would not even consider acquiring parts without bouncing the concept of of Dougal first, been there and done that before the 221 and it was not the least cost effective to just experiment with hard parts......$.02
I don't doubt that his calculations work. I'm quite sure they do, as I have stated before. My issue is he keeps nitpicking me and my methods, even though in my real world experience they have given me good results. No matter what I say, it's more "you are wrong, my way is the only way, my big brain trumps your experience" B.S. If you read the whole thread you will see that I did not direct anything at him, just responded to his responses attacking my position. And he just won't let it go. I'm glad your setup works, there is lots out there that don't. I have yet to see a dyno chart from him for these engines that prove his methods. I know for a fact there is quite a few 4BT out there making 500 RWHP and pushing less than 95 PSI of boost. Will his produce the power? Sure. Is it the only way to do it? Absolutley not. Anybody that does a little research will find many examples of these engines making that level of power with far less boost. Again, not saying he's wrong, just saying there's more than one way to skin this cat.
 
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