In need of Diesel supercharger/blower assistance

[Diecycle]

Good day,
I started a some talk of this on Locomotivebreath's great Honda/ruggerini thread but I do not want to hjack and so started this thread.

My goal is to take a RD211 (23 hp at 3600 rpm) and create a 28-30 hp at 3500 rpm. (with slightly better efficiency) The blower I am considering has a max speed of 3500rpm and given that I will be attempting to get a bigger bang out of the cylinders, lowering the max rpm of the RD211 from 3600 to 3500 as well seemed prudent.

I was hopeful that 5 psi could be enough to raise the overall efficiency and get a small hp increase, but not enough to damage the engine.

Here are the specs for my proposed blower. Admittedly some of this goes over my head.

RPM 1750

2 PSIG
CFM 8.5
BHP .2

4 PSIG
CFM 6.5
BHP .3

RPM 3500

2 PSIG
CFM 21.5
BHP .4

4 PSIG
CFM 19.5
BHP .6

Maximum pressure rise 5 PSI

The blower weights approx. 20lbs.

Thank you

[oilburner]

The first problem you will run into is the time lag between strokes of the single cylinder engine. According to Hugh MacInnes, author of the book Turbocharging, the solution to this is a plenum chamber on or incorporated into the intake manifold. He states the pipes from the compressor to the cylinder head(s) should have twice the volume of a single cylinder. A plenum three times as large as a single cylinder is even better.

Once you calculate the CFM of the engine, you can use the supercharger specs to determine how fast to run the supercharger to get the required PSI/CFM. A blow off valve should enable you to gear the supercharger to obtain boost quicker (lower RPM) and prevent overboost.

And don't forget a pyrometer to monitor cyl head temps! It will allow you to determine just how much boost the engine and its cooling system can safely handle.

Good Luck!

Avery

[Diecycle]

Thanks for the reply Avery,
Still confused over the whole thing a bit. I have not purchased the blower in question, but can obtain it relatively cheap. That is why I have much interest in this particular blower.

The RD211 is a two cylinder diesel engine if that changes anything.

If I understand your post, it sounds like this blower produces enough push to increase my engine power but I will need to obtain this book or a professioal to help me configure it for maximum effectiveness while not damageing the motor.
Right?

[Byrdman]

Do the two pistons rise and fall together?

[Diecycle]

They fire one at a time. There was a company called Centarus who used a ruggerini engine on their bikes and they had a audio clip on their website.

[oilburner]

Duh! I don't know why I had a single cylinder engine on the brain. Actually, Hugh McInnes specifically states that a plenum is required for a two cylinder engine.

I will re-read the info on the plenum, sizing, and other matching requirements and post some relative info to get you going.

On a related note I believe Byrdman was asking if the Ruggerini has a 180 or a 360 degree crankshaft. On a 180 degree crank, one piston is going up while the other is going down. The 180 degree crank has a power pulse every revolution (360 degrees) whereas the 360 degree crank has tow two power pulses 180 degrees apart and then a 540 degree lag. I suspect in the diesel application both designs have their not insignificant downsides.

I highly recommend getting a copy of Hugh MacInnes' book. This wikll answer *all* of your questions. Right now it's available from Amazon books for only $12.01US. Amazon also lists several other books on foirced induction as well as used copies:

Turbocharging by HP Books ISBN 0-89586-135-6
Library of Congress catalog number 76-6002

Below is a diagram showing the time lag between the power pulses on a two cylinder engine. It is easy to see why a plenum is required.



Avery

[Diecycle]

Thank you for the information.
I do not know whether I have the 180 or the 360 on the ruggerini. Sadly, I did not know there were two kinds. It has the "normal" one if that makes any sense. A running ruggerini RD211 sounds similar to a harley. This is the first diesel engine I have owned.

[oilburner]

Using the formulas from the Hugh MacIness book, I started to calculate the performance of the supercharger using the numbers supplied, but something doesn't make sense.

According to calculations, the engine requires 48 cfm at 3500 rpm, assuming an 80 percent volumetric efficiency. According to the numbers shown for the supercharger, it puts out only 19.5 cfm at 3500 rpm. That's doesn't seem like enough for a model airplane engine.

According to calculations, to achieve 4 psi boost at 3500 rpm the supercharger needs to put out 54.8 cfm, assuming 60 percent efficiency of the supercharger.

Sooo - unless there are some other relevant technical data for the supercharger with more realistic cfm figures I don't think the supercharger is a good choice (for anything).

BTW anyone who has Hugh's book, the formulas for calculations for motorcycles don't make sense. The Harley Davidson 74 example in the motorcycle section shows a flow requirement that is comparable to a 250 cu in engine! I used the generic formulas for auto engines.

I purposely have not shown any formulas or calculation methods to respect the book copyright.

My $.02 CDN.

Avery

[Diesel Dave]

Just done a bit of quick maths......

Your blower is way too small for an 800cc motor.

It's just about right for a 400cc which makes me think it's about the right size for a 125 petrol motor.

Nabbed it from a certain Peugeot Scooter did we?

Dave

[sbrumby]

correct me if I am wrong but the Ruggerini rd211 is 950cc. I have just done a quick bit of maths. 28317ccm in a cubic foot,at 3600 rpm the Ruggerini only pulls 475cc per rev. So thats 475 X 3600=1710000.
Now divide this by 28317 that gives 60.387752 cubic feet per min.
This figure is what the engine requires without any boost at all.
Hope this helps.

[Diecycle]

Thank you for the replies. The blower is an industrial roots lobe blower. It is hard to believe it is too small to do the job. It weighs 24lbs. The RD211 is 954cc so the given caluclations are prettty on.

I thought the small fan blowers/turbochargers are not as good because they are just fan, smf don't you need pressure to force the air?

[oilburner]

Hey sbrumby - you said to correct you if you were wrong...

Actually you were not wrong but just not 100 percent right

The figure of 60.387752 cfm for the RD211 quoted by sbrumby doesn't take volumetric efficiency into consideration. Diesel engines generally operate at 85 percent efficiency compared to 80 percent for petrol engines. Multiply 60.387752 by 85 percent and you get 51.329589 cfm.

The figure I quoted - 48 cfm was at 3500 rpm ( the max rpm given by Diecycle). I inadvertently assumed 80 percent volume efficiency. Had I used 85 percent my figure would have been 50 cfm at 3500 rpm which compares to sbrumby's 51.3 at 3600 rpm (which would be 49.9 cfm at 3500 rpm).

On a related note, when calculating the supercharger flow, remember you must take the rise in intake manifold temperature into consideration as this affects the output cfm.

Finally, don't forget that plenum (air box) to dampen the pulses in the inlet manifold. Otherwise Hugh says when the intake valve opens the flow will drop even if the supercharger capacity is larger the engine requirements. You can get conditions where supercharger will go into surge i.e. flow stops, sharp banging sound, etc. Not good.

FYI

Avery.

[oilburner]

Oh, one more thing. Remember that supercharging won't improve performance one iota unless you increase the fuel flow. Remember that old adage, you can't have power and fuel economy at the same time.

If fuel economy isn't a concern, you can supercharge or turbocharge a diesel engine to ridiculously high manifold pressures and get huge power increases up to a point where it goes bang.

FYI

Avery

[Diecycle]

I have the performance charts for this blower but I do not know how to post pictures. The sheets are jpg's

I understand what you are saying about power/efficiency but I thought if an engine works more efficiently then it is possilbe to get both better mpg and a bit more power. I was hoping for a 20% increase in power and to hold either the same or slightly better mpg by increasing the efficiency of the motor.

It was those VW's fellows that got me thinking this way. They have used turbos to both increase performance and mpg.

I still want to supercharge/turbo this motor but am open to scraping this industrial blower and finding another path. It's all a learning experience.


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[sbrumby]

Avery Frail is correct. More power more fuel. So if you go down the supercharger root you will probably need a new injector pump which could be tricky to find that fits the motor & new injectors. If this works you would need to alter the gearing on the bike as the engine would give more BHP at a given rev. So if you altered nothing you would be useing more fuel for the same speed. But far the bigest problem is the lasting & reliability of the engine. Dragsters get about 2500HP out of an engine that was designed to push out about 250HP, after about 3 miles they are scrap if they are lucky.

[sbrumby]

Just checked spare engine, the RD211 is a 180deg configureation.

[oilburner]

180 degree crank, eh? If you look back at the picture I posted showing the strokes / rotation, you'll notice there is a 360 degree period when there is no intake cycle. Therefore it's very important to compensate for the stagnant flow by incorporating a plenum.

Regarding power vs fuel economy, like the VW you will likely realize an improvement in fuel economy if you pump in more air without more fuel. You can have your cake and eat it too if you set up the fuel enrichment to start when the compressor reaches a predetermined pressure. I think this might be a considerable challenge with a positive displacement supercharger but it's easier with a turbo and injection pumps that have enrichment devices.. This also means you would want fuel enrichment to engage only while accelerating, not while cruising. This means if you use a supercharger or turbo to make up a power deficiency in an underpowered engine for the application, it will likely be in continuous boost mode and fuel economy will suffer.

Avery

[Diesel Dave]

Correct me if I'm wrong here.

The Ruggerinin is based on the Lombardini design and therefore likely to have the spring loaded 'overtorque' plunger which the regulator arm pushes against. In high demand circumstances you can see the plunger indicator nipple pop out of the end of the screw adjuster.

If this is the case it might be easy to set up an extra stop on this plunger that can be operated at high boost/requirement situations. For example add an additional heavier spring loaded stop manually pulled against at full throttle.

As regards plenum chambers, I've been planning on using a motorcycle radiator - good for 15psi (regulated by the pressure cap) and should provide some air to air intercooling. Lots of different sizes available, and easy to fit rubber elbow connections.

Just my 2p worth.

Dave

[sbrumby]

I am not sure of the relationship between ruggerini & lombardini, they were separate companys but are now one. On my engines there is nothing external that pops out unless I am missing something, just two levers one for speed that afects the govenor and the other stop this just lets the racks go to a possition below tickover.

[Diecycle]

Thanks again for the replies.

Avery is correct I was hoping to run the blower continuous, not because I think the RD211 is greatly underpowered (I am not a throttle jockey) but because that is the easiest way to set one up.

I have a friend who works on VW diesels and had a thought try and adapt the control computer to work with the Ruggerini. Getting the wires right was not a big problem because it would not be hard to fool the computer for a 4 cylinder to run on a 2 cylinder but I did get discouraged when looking at the installation of all the sensors that feed the control computer.

I have never attempted anything with a automotive control computer (still refuse to buy a car made after the 70's) so I have been trying to avoid this idea.

Has anyone had experience working with sensors and computers with turbos and diesels? Is it as complex as I have feared or can a fellow with a wrench figure it out?

Also are those computers set for the exact engine displacement of the engines which they are attached or could they be set up to focus on the fuel/air/ mix independant of the actual displacement?

This may be another instance where I need to buy a book instead of starting from ground zero with the board, but thank you for any assistance.

[Diecycle]

Good day,
I went down the computer controlled turbo for a while and found it to be a more advanced then I care to tackle at this moment.
So I am back to a supercharger.
Looking at the smallest common eaton supercharger (M45) and taking into account it could rob up to 20% of the HP from the RD211 at crusing speed. It would appear that to reach my goal of an increase of 20-25 percent I should increase the air intake (and fuel intake) 40-50 percnet.

Looking at the specs of the eaton M45, any thoughts on whether or not this is a good candiate?

Thank you

[Diecycle]

http://www.capa.com.au/eaton_m45data.htm

[Diecycle]

Posting and trying to work makes for some choppy entires. Sorry about that.

More on the Eaton M45 from the eaton site. The "inlet" cfm is 100cfm at 4000 rpm (the minimum listed) and 300cfm at 14000 rpm(the maximum listed)both at 5 psi.
There are figures listed to run the charger at 10psi but that seems like too much for reliable, long term operation,or am I missing something?

As I understand it, if a supercharger is used, then the injectors and or pumps will have to modified to increase fuel flow.

[oilburner]

Unless you have your heart set on using a mechanically driven supercharger, a Warner-Ishi RHB3 turbocharger would probably work very well on your Ruggerini. It's designed for engines 500cc - 1.3 litres and you could set it up from mild to wild or anything in between. Furthermore, it takes no power to drive the turbo. The turbo is tiny - not much bigger than a film canister. The RHB3 was used on the Suzuki Swift and the Chev Turbo Sprint and Pontiac Turbo Firefly in North America with the 3 cylinder 1.0 litre engines. Screw down the waste gate and hold on!

FYI

Avery

[Diecycle]

Thank you for the reply.

I am still not convinced that a turbo charger would work better than a supercharger, but since Avery has demostrated superior knowledge on this subject I am going to revisit turbos.

When looking at turbo's, is it possible to use a turbo taken off a gasoline engine to use on a diesel engine?

Also, I notice some turbo's have diaphrams mounted to them. Am I right in assuming this is for carberated engines and works off the carb vacuum?

Thanks in advance for any help.

[andrewaust]

Hi Guy's


A small petrol engine Turbo like the ones on the CX500/650 or other M/C's of higher capacity should work, it just depends on when you want the boost to come on and how much pressure your aiming at. Small Turbos boost early but my not be able to keep boost at high RPM.

Now this is the good bit - if you use a turbo from a small petrol engine, they run at higher RPM's, so in theory one of these Turbos can be put onto a slightly larger Diesel Engine - it's just a matter of working out how much air the engine will consume.

Some make the fatal mistake of putting a whopping big Turbo on there engine and ask "why is this thing such a dog" The larger you go the higher in the RPM's it will take to spool up the turbine and make boost, in some cases will never achieve full boost at all.

The diaphragm you are talking about may be the waste-gate actuator, this stops the Turbo from over boosting the engine by bypassing exhaust gas straight to the exhaust port of the Turbo.

Reading through the post their are both Blowers and Turbos mentioned. Both have their pro's and con's! Blowers take H.P away from the engine where a turbo is drawing its power from waste exhaust gases.

Blowers can be set up to boost with no lag, where Turbo's need to spool up to make boost, commonly called "Turbo Lag".

Some blowers use there own oil supply, some don't. Turbo's always need an oil supply and it can increase the oil temperature of an engine quite substantially, so putting an oil cooler on would be a good idea, as would increasing the oil volume if you have an engine with only 2-3 liters of oil sitting in the sump.

Small Vehicle engine Turbo's many also do the job if you are using a 3cyl engine. The tricky part is getting the figures right, as a lot of R&D goes into finding the right Turbo for a particular engine.

"Just remember to keep boost at a low pressure with a diesel = 4-6 pound of boost" Some of these engines are running up to 22:1 compression, while others as low as 16:1, get it wrong and piston skirts and cranks may fail leading to an expensive repair bill.

As you can see it can be a rather complex subject. I'd like to build a blower/supercharger similar to the Rynhart one.

If all of the above concerns you - there's one other thing to question = will my injection system work properly with extra compression/boost ????






Cheers


Andrew

[oilburner]

BTW my preference as to superchargers vs turbochargers is solely based on the bottom line - the turbo has a smaller footprint, is physically simpler to install (more on this later), and automatically responds to demand for more power (via the throttle). There are no belts, pulleys, centrifugal clutches, etc. On the other hand, a sanitary supercharger installation in polished alloy with its pulleys and belts is the hands down winner in a beauty contest. If I was building an engine for show, not go, it would be my choice.

The IHI RHB3 turbocharger I suggested was used on the Daihatsu Charade 1.0 litre diesel car as well as the Suzuki 1.0 litre 3 cylinder car and its Sprint / Firefly derative engines. Although I have never driven any of these cars, I feel quite certain that turbo lag was not be a problem with any of them, otherwise the manufacturer would have had a bigger problem As a note of interest the Honda CX500 and CX650 turbo bikes used IHI turbochargers.

Regarding Andrew's comment:

A small petrol engine Turbo like the ones on the CX500/650 or other M/C's of higher capacity should work, it just depends on when you want the boost to come on and how much pressure your aiming at. Small Turbos boost early but my not be able to keep boost at high RPM.

Remember, a turbocharger has two parts - the compressor and the turbine. The compressor supplies the boost, The turbine converts exhaust gas into rotary power to drive the compressor. The choice of turbine housing determines how quickly the turbo spins up i.e. lower engine rpm. A turbo has a choice of turbine housings. The turbine is fitted with a waste gate that controls the amount of exhaust spinning the turbine wheel, the excess exhaust bypasses the turbine. The setting of the waste gate controls the amount of exhaust spinning the turbo thus controlling the turbine speed thus controlling boost. In the case of the slow diesel industrial engines we use, we want the boost to come on early (1800 - 2200 rpm) and control it with a wastegate.

One very important issue: The life of a turbo depends on a constant ample supply of clean oil and a hose providing an unrestricted flow of oil from the turbo back to the oil sump. The turbo bearing runs on a film of oil. At 200,000 rpm, a lack of oil is disasterous. Never rev up a turboed engine after starting until you are sure there is full oil pressure to the turbo and never shut it down quickly after a high speed run. Let the turbo slow down and cool down a minute before shutting down the engine.

As Andrew stated, a significant increase in oil temperature is a factor. An oil cooler should be included as part of the installation. Change the oil often.

In a diesel engine, the amount of boost is not as big a deal as with a gasoline engine. If you just add more air and no extra fuel (i.e. no injection pump modifications) , the result will be less or no smoke, a bit more power due to burning the fuel otherwise exiting the exhaust as smoke, and a bit better fuel economy. The problem arises when you inject more fuel than the engine was designed to use at a given RPM. You can generally boost a diesel 20 to 30 percent in horsepower without internal modifications. The rule of thumb is to keep the exhaust temperature below 1300 degrees. Remember though, more hp means more fuel which means reduced fuel economy.

Geez, I've written enough here in the past couple weeks or so that I'm starting to convince myself to add a turbo to my Daihatsu D950 The reason I didn't buy a D954 turbo in the first place is because it would only make it easier to get a speeding ticket.

Avery

[Diesel Dave]

There are some modifications you will need to make to the injectors.

You will need to up the break pressure either by adding spacer washers or re-springing.

It will be a good opportunity to check the tips are not weeping too.

The little jump pumps fitted to stationary diesels are not capable of massive pressures needed to push against high boost.

It may be possible to boost the output pressure by increasing the pressure of the fuel prior to the jump pump. Adding an electric fuel pump (or pumps in series) will raise the starting pressure by 8-10 (or 16+) psi.

I've never done any testing on this so it's all theory at the moment!

I too have a tiny turbo to fit to my next project motor.

You can make the wastegate adjustable for pressure release by cutting through the link rod and adding a threaded section to make the length adjustable.

Best of Luck
Dave

[oldbmw]

-IF- your engine has sufficient resrves of mechanical strength, a slight boost with aturbochrger is likely to give a slight increase in power for these reasons.

1 the extra air makes it easier for all the fuel to find oxygen and therefore burn, this helps at all throttle openings*
2 the extra air increases the effective compression ratio so improving efficiency also because there is more compression the fuel will burn better due to teh air being hotter again at all throttle openings*
3 most injectors can be set to overfuel, the extra air will compensate for this.

*note* only when the turbo is working, low openings it is not.

[Diecycle]

Thank to everyone who has replied. I am pressing forward with this project (chirstmas is slowing it down just a bit) but will keep the board updated.
Thanks again.