turbo vs supercharger for 2B diesel, lots of mud and crossing creeks

[gbentink]

I see you have been busy editing!
Quote"Crank power turbocharged = 80.7 -10.7 = 70kw
Crank power supercharged = 80.7 -13.5 = 67.2kw" Unquote

Thankyou, thats all I was after. Now where does the extra power come from after parasitic losses are taken into account? As far as I can work out it has to be more airflow across the head, which allowed me to turn the fuel up, I can't think of any other reason for the extra power, may7be you can help here Dougal?

I'm floored.... it has been said many times.... the extra efficiency of the turbo comes from the temp drop accross the turbine (80%) AND what you are calling parasitic losses (20%).

ALL the drive for teh blower coems from what you are calling parasiotic losses, its just its from the end of the crank rather than top of the piston.

If I wasnt so busy at work I'd write more, but I have to commend Dougal on his persistence in trying to help you understand. I think it is good for all readers.

If you are happy with the economy you get with a 2.4L Diesel in a light vehicle and its worse than I (and everyone else) gets with a much larger engine in a heavier vehicle, then no probs, glad your happy.

The examples of laggy vehicles you have chosen are about the worst example ever.... you need to drive a Diesel that performs in all respects. If your in Perth, drop by some time and I'll show you first hand.

A well setup turbo diesel hammers mate, really hammers. It can develop great torque at low rpms and also can rev. I took out my v8 injected petrol to fit my 4.2 diesel. The diesel kills in in every way (except engine noise). If you cant say that about your setup then maybe you should try and find out what all the fuss is about with us turbocharging.

AND.... if a blower was really that great, I would have one!

 

[mudgudgeon]

It should tell you that lots of us enjoy reading Dougal's explanations of turbo theory, plus your defense of using superchargers just adds a comical twist to the whole thing.

Agreed.

Dougal has slapped every comment with detailed articulate answers, and the only "positive" blownoiler presents is he can run filtered engine oil as a fuel!

 

[blownoiler]

If by "extra power" you mean the turbo doing better, it's because it takes 2.8kw less to drive than the supercharger

NO.....the extra power came from fitting the supercharger
REPEAT: the extra power came from fitting the supercharger, you have to twist my words to mean something else because you have no answer.
With the charger fitted I could screw the fuel adjusting screw in to runaway , and then add more fuel as revs rose up with the boost activated compensator. The charger has some leakage at idle speeds so 4-5 pounds of boost was the usual pressure at idle speed depending on what idle speed I could live with. When I eventually put the turbo back on I had to screw the fuel screw back out around 2 turns, and back the fueling off on the compensator as well. I couldn't burn as much fuel with the turbo because there wasn't enough air being inducted into the engine to burn it. Pure and simple! The extra power produced by the charger was more than enough to cover the supercharger drive loss. I've done it , you guys haven't so wouldn't know!



As much as I'd like to improve the airflow through your head, all the methods that come to mind are illegal in most countries. Even Australia.

subtly threatening to shoot someone is pretty piss weak Dougal, maybe you should "go do it the first time with your clay blow up doll" har har

 

[Dougal]

Dunno what you're on about.

A blow-up-doll made out of clay! How is that supposed to work?

 

[blownoiler]

I'm floored.... it has been said many times.... the extra efficiency of the turbo comes from the temp drop accross the turbine (80%) AND what you are calling parasitic losses (20%).

ALL the drive for teh blower coems from what you are calling parasiotic losses, its just its from the end of the crank rather than top of the piston.

If I wasnt so busy at work I'd write more, but I have to commend Dougal on his persistence in trying to help you understand. I think it is good for all readers.

If you are happy with the economy you get with a 2.4L Diesel in a light vehicle and its worse than I (and everyone else) gets with a much larger engine in a heavier vehicle, then no probs, glad your happy.

The examples of laggy vehicles you have chosen are about the worst example ever.... you need to drive a Diesel that performs in all respects. If your in Perth, drop by some time and I'll show you first hand.

A well setup turbo diesel hammers mate, really hammers. It can develop great torque at low rpms and also can rev. I took out my v8 injected petrol to fit my 4.2 diesel. The diesel kills in in every way (except engine noise). If you cant say that about your setup then maybe you should try and find out what all the fuss is about with us turbocharging.

AND.... if a blower was really that great, I would have one!

I have previously stated that I think turboed diesels are a great idea, a turbo is about 1/20th the size of the engine and can move 3-4 times as much air as what the engine can. The internal combustion engine is quite good at converting energy into a usable form, but is not very good as an air pump, moving air in a more efficient manner is best left to forced induction in my opinion! Factory fitted turbo's in the cars that most of us drive are a compromise, log manifolds designed on cost without concern for exhaust flow, emission regs, packaging constraints etc. have resulted in less than perfect set ups, hence aftermarket kits that can improve on the factory fit. While a crank driven positive displacement charger is not as efficient as a turbine driven charger, they do have the advantage of better airflow on the exhaust side of the head, my experiment on the little 2lt made this gain in airflow more than obvious.
I'm not trying to take sales away from you turbo fitters, just trying to offer an unbiased alternative to the O.P. having compared both turbo and crank driven chargers on the same engine.
I have relatives in Perth, next time I'm over I will take you up on that offer to check out your cruiser if that was a serious offer!

 

[Dougal]

I have previously stated that I think turboed diesels are a great idea, a turbo is about 1/20th the size of the engine and can move 3-4 times as much air as what the engine can. The internal combustion engine is quite good at converting energy into a usable form, but is not very good as an air pump, moving air in a more efficient manner is best left to forced induction in my opinion!

Sorry but no.
Turbos can't move air by themselves, they are driven by the engine they are fitted to.
The best production internal combustion engine is in the mid 40%'s for efficiency. Your 2LT is only about 26% efficient at full power when turbocharged, it is worse when supercharged.

Piston engines are great as air-pumps. But they can only pump their own volume every two revolutions. To get more air through them, we need to compress it.

Factory fitted turbo's in the cars that most of us drive are a compromise, log manifolds designed on cost without concern for exhaust flow, emission regs, packaging constraints etc. have resulted in less than perfect set ups, hence aftermarket kits that can improve on the factory fit.

I'll take a factory log manifold over anything you or the aftermarket can produce every time. OEM's use manifolds of minimal volume to minimise response time. Manifolds that are designed by very clever people using the most advanced flow modelling tools they can get. As a result, using those minimal volume manifolds they are producing the best figures we have ever seen for power, torque and fuel economy.

While a crank driven positive displacement charger is not as efficient as a turbine driven charger, they do have the advantage of better airflow on the exhaust side of the head, my experiment on the little 2lt made this gain in airflow more than obvious.

So more than obvious, but not producing any data or performance figures that can be used in any way to benchmark it's peformance?

I'm not trying to take sales away from you turbo fitters, just trying to offer an unbiased alternative to the O.P. having compared both turbo and crank driven chargers on the same engine.

I don't think you've scared any potential customers away from any turbochargers. But I don't think you can lay claim to being unbiased.

 

[cicak]

im subscribed to this soap.

Im also looking at a compound turbo for the red monster.

Which is the truer statement

 

[blownoiler]

Sorry but no.
Turbos can't move air by themselves, they are driven by the engine they are fitted to.


DER

 

[Dougal]

DER

Finally, we agree.

 

[gbentink]

Factory fitted turbo's in the cars that most of us drive are a compromise, log manifolds designed on cost without concern for exhaust flow, emission regs, packaging constraints etc. have resulted in less than perfect set ups, hence aftermarket kits that can improve on the factory fit.

Actually, the log manifolds might seem to the uninformed as packaging related constraints (and they do solve some), but, the main reason is lower volume, maximising the high pressure pulses to more efficiently drive the turbine. I was speaking with a diesel tuner who's customer went to huge expense making an equal length mandrel ext manifold and it dynode less [peak horsepower and added some extra lag. Diesel have essentially no valve overlap (not just for turbo application issues, but cold cranking pressure for starting) I'll not change my manifold, thats a certainty.

While a crank driven positive displacement charger is not as efficient as a turbine driven charger, they do have the advantage of better airflow on the exhaust side of the head, my experiment on the little 2lt made this gain in airflow more than obvious. /QUOTE]

What was so profound about the exhaust pressure difference and how did you measure this difference. How did you quarantine other variables during testing that may have influenced the outcome had they not been. If you have changed your cam timing, then yes there could be an issue there. If I were to run a blower, I would run it miller cycle.

I'm not trying to take sales away from you turbo fitters, just trying to offer an unbiased alternative to the O.P. having compared both turbo and crank driven chargers on the same engine.

I don't think your trying to take sales away, I guess you could claim I may be biased, but I try not to be. Facts are facts, plain and simple. I do turbo upgrades to make a difference and it was primarily driven by my own needs and those of friends. If A blower would work better I would probably be doing blowers... I posted many times on a 12HT build I was doing. At one stage I think I had a blower/turbo combination... I can't recall. In the end, twin charging with vnt and twin water to air inter cooling was replaced with a single waste gated turbo and air to air.... Ah for design reviews.....

I have relatives in Perth, next time I'm over I will take you up on that offer to check out your cruiser if that was a serious offer!

You bet I am serious - and that offer is valid for anyone in Perth.

 

[Dougal]

You bet I am serious - and that offer is valid for anyone in Perth.

I'll come visit one day. I've got some extended family working out that way.

 

[blownoiler]

Actually, the log manifolds might seem to the uninformed as packaging related constraints (and they do solve some), but, the main reason is lower volume, maximising the high pressure pulses to more efficiently drive the turbine. I was speaking with a diesel tuner who's customer went to huge expense making an equal length mandrel ext manifold and it dynode less [peak horsepower and added some extra lag. Diesel have essentially no valve overlap (not just for turbo application issues, but cold cranking pressure for starting) I'll not change my manifold, thats a certaint

The exhaust manifold on your engine is probably a better design than the 80s/early 90s manifolds. I put a devider in my 2lt (1985 design)manifold to direct the pulse of exhaust gas toward the turbine, the standard manifold layout is a bit average, the flow leads from cylinder 1 straight along the manifold to cylinder 4 then bounces around until finding the outlet, disipitating some of the kinetic energy of the pulse, the divider also effectively halves the manifold volume seen by the pusle. Toyota fixed this in later model engines with a built in devider, so I copied their design, unfortunately the firing order doesn't help here, exhaust pulses from each side of the devider in succession would have been better than the 1-3-4-2 firing order but there is still a gain to be had. I'm presently making a devider for my Isuzu 3.1 (1993), which has no devider from the factory either, the hard part is getting a long life from a bolt -in piece, 2 or 3 years (around 100,000k) has been the average lifespan before heat and vibration starts to loosen the plate, but this time I have the benefit of hindsight to help (and 2 spare manifolds to play with) so am hoping to design a longer lasting piece.
It would be interesting to try a mandrel bent system that was sized correctly, obviously that customer went too big in diameter and/or length as you said earlier, the exhaust manifolds on later engines (post early 90s) must be miles ahead of the earlier log style that some manufacturers (Toyota/Isuzu) used on their turbo diesels.

 

[Dougal]

I'm very happy with my mid 80's Isuzu manifold. The later manifolds (88 onwards) however are more compact and have a more common T3 flange.

I can guarantee that the manifold is not what is holding up the peformance of your 2LT.
Have a read of this: https://forum.ih8mud.com/diesel-tech-24-volts-systems/506138-2l-tt-egts.html

 

[blownoiler]

While a crank driven positive displacement charger is not as efficient as a turbine driven charger, they do have the advantage of better airflow on the exhaust side of the head, my experiment on the little 2lt made this gain in airflow more than obvious. /QUOTE]

What was so profound about the exhaust pressure difference and how did you measure this difference. How did you quarantine other variables during testing that may have influenced the outcome had they not been. If you have changed your cam timing, then yes there could be an issue there. If I were to run a blower, I would run it miller cycle.




I don't think your trying to take sales away, I guess you could claim I may be biased, but I try not to be. Facts are facts, plain and simple. I do turbo upgrades to make a difference and it was primarily driven by my own needs and those of friends. If A blower would work better I would probably be doing blowers... I posted many times on a 12HT build I was doing. At one stage I think I had a blower/turbo combination... I can't recall. In the end, twin charging with vnt and twin water to air inter cooling was replaced with a single waste gated turbo and air to air.... Ah for design reviews.....




You bet I am serious - and that offer is valid for anyone in Perth.

When you only have around 60/70 rear wheel horsepower an extra 5 h.p. is easy to notice, the best power gain in turbo form came from relieving backpressure on the factory turbo engine, porting around the wastegate exit (and shaping the inside of the turbine entrance leading to the wastegate) gave a good increase in power, the standard exit hole on the c.t.20 is around the size of a 5 cent piece, I took it out as much metal as the sealing penny would allow, resulting in a hole of almost double the diameter. The exhaust divider helped to keep gas velocity up so I could vent off excess pressure in midrange/high revs and still retain the same spool-up/boost. Further porting on the wastegate approach didn't return much (if any) more power. I then decided that further gains in breathing were needed to release more power, so decided to try the supercharger route to see what effect it would have on airflow through the engine. That turned out to be a good choice, I couldn't believe the difference in power, I didn't have to row the gear lever to keep up with fast moving traffic anymore, suddenly I couldn't wait to finish work so that I could drive it! I would have liked to put the car on a dyno, but had more pressing financial priorities.

I would have tried an upgraded turbo if I had the spare cash, I got the blower at the right price, plus I wanted to try one out for myself rather than rely on secondhand accounts.
Thanks for the offer to have a look at your build, could be a while before I'm over that way though!

 

[blownoiler]

I'm very happy with my mid 80's Isuzu manifold. The later manifolds (88 onwards) however are more compact and have a more common T3 flange.

I can guarantee that the manifold is not what is holding up the peformance of your 2LT.
Have a read of this: https://forum.ih8mud.com/diesel-tech-24-volts-systems/506138-2l-tt-egts.html

I don't drive the 2lt much anymore, just keep it as a spare set of wheels. I'm presently modifying an exhaust manifold for the 4jg2, I might even try the rhb5 in place of the rhf5 as I have one sitting in the shed. The rhf5 is too slow to spool in factory form, no boost until 1700 revs.

 

[Dougal]

Porting wastegates does nothing useful on diesels and you won't do anything measurable with your exhaust divider.

RHB5/RHF5 is the same thing, just the F series generally aren't rebuildable. Look on the exhaust housing for an A/R number. IHI use CM and you'll be looking for a number between 10 and 20.
Smaller A/R gives sooner boost and higher max boost. But does lower top end power.

Subaru housings interchange on some Isuzu RH-5 turbos.

But first check you are getting the fuel you should. Fuel restrictions delay boost arrival. Is your one EFI or mechanical? How rotten is the boost compensator diaphragm?

 

[Hulsty]

How would porting the wastegate effect power? Isnt the purpose of the wastegate to control pressure?

 

[blownoiler]

Porting wastegates does nothing useful on diesels and you won't do anything measurable with your exhaust divider.

RHB5/RHF5 is the same thing, just the F series generally aren't rebuildable. Look on the exhaust housing for an A/R number. IHI use CM and you'll be looking for a number between 10 and 20.
Smaller A/R gives sooner boost and higher max boost. But does lower top end power.

Subaru housings interchange on some Isuzu RH-5 turbos.

But first check you are getting the fuel you should. Fuel restrictions delay boost arrival. Is your one EFI or mechanical? How rotten is the boost compensator diaphragm?

I've got 2 spare rhb5s, one is 37 A.R., the other .38, the factory turbo is covered in heat shields so I don't know what A.R. it is until I get a chance to take them off.

 

[Dougal]

How would porting the wastegate effect power? Isnt the purpose of the wastegate to control pressure?

It doesn't.
However there is a 5 or so page thread (before it was locked, thankfully) where Fourex (Blownoiler) and Drifter are making wild claims about wastegating. Including porting, gaining faster spool with a wastegate, dropping boost to increase airflow, wastegating to drop drive pressure without losing boost and more.

If you are interested, I seriously recommend you do not read it. Your will come out dumber.

 

[Dougal]

I've got 2 spare rhb5s, one is 37 A.R., the other .38, the factory turbo is covered in heat shields so I don't know what A.R. it is until I get a chance to take them off.

You have quoted A/R in inches. IHI don't measure A/R in inches. Have you converted these numbers or have you got the wrong numbers?