Disappointing turbo performance

[Banzaibob]

These are pictures of the Red Devil project that I began last spring. https://www.dieselbikeforum.com/view ... f=7&t=2323 After consulting with some of the people on this board I decided to go all in and turbocharge my Yanmar L100/CB350 project called the Red Devil. Before the turbocharging the bike ran pretty solid with a top speed of 55mph. In order to have a more street-able power-band, I retarded the injection timing by about .005" and even though the top speed performance was slightly compromised, it still performed well.

Today I just finished up the turbo installation (RHB31) and took it out for a test ride. Performance was rather anemic with about 50mph being the top speed. It seems to run dramatically smoother but appears to "hit the wall" and not want to push past. Low speed acceleration is rather poor also. I have a fuel stop that limits the amount of fuel you can dump into it past a certain throttle position. However, looking behind me as it struggles to get past 50mph, I assume that it is getting enough fuel by virtue of the fact the it is pumping quite a bit of black smoke at full throttle. Hooking it up to a pressure gauge at the wastegate port indicates that at full throttle (with no load) it is generating about 6-8psi of boost.

I have installed an intake plenum of about 1300cc and the exhaust pipe to the turbo is slightly oversize for the same reason of perhaps smoothing out the pulses. I've included some pictures. I was hoping for at least enough power to make 70mph but instead it appears that I have lost 5mph. I'm hesitant to advance the timing because low rpm knock is un-nerving. Any ideas?

[Stuart]

Maybe reducing the diameter of the exhaust pipe going to the turbo slightly might increase the air speed of the exhaust gases acting on the impeller & thus speed it up?
This might make up for the lack of air hitting it, this being a single cylinder engine?
I'd imagine that getting these impellers up to a higher speed & keeping them there through the 4 stroke cycle of a single won't be easy. Perhaps experiment with internal rings of some sort until you strike a balance between air speed & a hole size that doesn't compromise the importance of the exhaust action over all.
That's all I can think of.

[Banzaibob]

I've been going through everything to give me a "seat of the pants comparison." First, I took off the muffler (HD dyna, no restriction), no change. Then I disconnected the wastegate dashpot and checked my boost, up to 7-9psi when maxed out. Next, I disconnected the turbo at the intake manifold, basically running a straight intake. No change.

Honestly my first impression was that it felt like a restricted exhaust. The engine is now significantly quieter because of all this new plumbing. It feels as if the exhaust pressure is simply not overcoming the inertia required to spool up the turbine AND flow the exhaust gases efficiently.

How does one increase the exhaust flow without negating turbo function?

[BertTrack]

You've produced a nice example there of the effects of retarding the injection and the results from it.

Retarding:
In your new situation
At low rpm the knock is less because the peak pressure happens after tdc, You're only injecting a little fuel here so it evaporates and ignites swiftly.

At high rpm's and high power you're dumping in a lot of fuel that needs time to evaporate and ignite. While giving it even less time than normal because you retarded the injection. Naturally this results in lower power (effectively used power) and more wasted fuel out the exhaust (smoke)

You only need to retard the injection when the inlet temperature goes high. I can't put a temperature on it. But it's a lot. The turbo could add that much heat but only if it's really pumping a lot. And with that one cilinder in that setup it's not going to use the turbo much anyway.

The knock at lower RPM's is normal. It should be less when the engine heats up and the fuel start to burn earlier because of it. (and more evenly)

The manufacturer designed the engine to be capable of running hot and still not break down from idling or running full revs.

When it starts knocking when it's hot and @ rpm's think about retarding.
==================================================================

Turbo piping:

Imagine if the piping to and from the turbo was normal. The pulse from the exhaust (pressure wave) would hit the turbo after a calculable time, it would accelerate a fraction and as the inlet valve opens up the energy it has just received would be spend useful on the inlet stroke filling the engine.

Adding volume to that on the exhaust or inlet side smooths out the pulses but also negates the potential of kinetic energy in the exhaust gases being put to good use in the inlet side.

Depending on the rpm, volume and temperature of the gases your performance boost won't be flat over all the rpm range. But that's normal.

If you want to add a plenum make it adjustable (screw in type pipe in a pipe). Then you can find your optimum. Or even hmmm make the volume depend on the rpm? OH that could be an idea.

[Banzaibob]

Before I installed the turbo I retarded the timing to make the bike more "streetable." It pulled stronger off idle and ran smoother and quieter on surface streets (25-45mph). This being my first diesel motorcycle build I am quite frankly put off by what I would consider severe knocking, maybe I just need to quit being a wuss and accept that it's going to make a racket? I should mention that I am using the governor to make it idle. Without it, you can barely keep it running.

[BertTrack]

I guess the knock depends on the brand and the type of injection.

If it's a direct injected engine it's supposed to knock. Especially when they installed a single pulse injector. (opens only once)

Is there a distinct difference between the engine @ idle cold versus hot (20 minutes on the road)? This should be a distinguishable effect on the burn inside the engine and the sound it makes.

I have a single cilinder Yanmar stationairy engine which is laid out for 1500rpm to 3000rpm. It'll idle lower but is very hard to regulate there since it's not meant to be idling there.
The fuel pump has rudimentary controls for fuel capacity but it will do in that rpm range. Just not below. This could also be the case for yours.
(needle valve is opened when rpm is too high)

Any movies up from this engine? Idling etc?

[Banzaibob]

http://www.youtube.com/watch?v=Itb4BKgv ... e=youtu.be

[XLerate]

The total tuned length of the exhaust tract is going to have an effect on how strong it runs too. The engine depends on the proper exhuast length to cause a low pressure reversion wave in pipe to help pull exhaust to exit. Too short a pipe can make the exhaust fight to escape.

I've got the correct lengths for naturally aspirated gasonline engines, don't know if they're the same for turbo'd diesels? What you might try is adding a foot or more to exhaust pipe total length and see if there's any change in running characteristics, there should be. I can post the appropriate legth for an NA gasser at any particular peak rpm if desired, might give something to go by. If you post your top rpm I can look it up.

[BertTrack]

Banzaibob,

I think that was with a hot engine? Didn't sound knocky to me.

[Banzaibob]

That video was with a relatively cool engine (running less than 2 minutes). That is with an additional .005" shim added to retard fuel timing.

[BertTrack]

Ah! Shame you can't advance it on the go.

[Banzaibob]

Last summer I asked that same question when I was deciding on turbocharging. https://www.dieselbikeforum.com/view ... =33&t=2341

Actually 30 minutes ago I removed the .005 shim that I installed to reduce the knock. I took it for a test ride. It knocks (duh) but it appeared to rev out a little better. I would say it's performance improved by about 10% (still 10% lower than non-turbocharged and 25% less than my minimum target).

[toyotaracer9]

Is their any way to get a boost pressure reading at the plenum mounted to the engine? I dont see a need for an additional plenum with that length of charge. pipe. A turbo is a big restriction in the exhaust flow if the compressor side isnt getting the charge into the engine, it all has to work together. you can run a straight pipe with the turbo too, they like to have zero restriction after the turbine but like someone else mentioned the exhaust pipe going into the turbine should be smaller to keep the heat energy moving until hitting the turbine wheel.

[Banzaibob]

I didn't measure at the plenum but at the wastegate port (right before the plenum) at medium throttle it would generate about 2-3psi of boost and at upper rpm/full throttle it would generate 7-9psi(at speed, with a load). Right now I am running a 1 3/4" O.D. pipe (a little more than 1 1/2" I.D.) from the exhaust port on the engine to the the intake on the turbine, about 15". That would equal approximately 30 cu.in. The diameter of the exhaust port on the Yanmar is a little bigger than 1", same for the intake on the turbine. If the whole thing is suffering from a restricted exhaust, how will using smaller diameter pipe help? Using 1" pipe 15" long would give me an exhaust volume between the engine and turbo of approximately 11 cu. in. Also I should mention that The flange that I cut out for the exhaust side is too close to the waste gate impeding it from opening all the way, this gets fix right away.

In asking some of the local guys about this I have even heard that I should restrict the low pressure return on the injector in order to force more fuel. Right now I think it is overfueling (lots of black smoke, no acceleration).

I should probably explain what I'm after; before turbocharging it would do an honest 50-55mph, 150mpg. Pulling a hill with a headwind, maybe 40-45mph. I don't want to go 100mph, I just want to hold my own in interstate traffic, 70-75mph if need be. Right now (pre-turbo) it was an excellent around town, errand bike. I'm looking for the turbo to give me just incremental increased performance without sacrificing stability or reliability. Ideas?

[Banzaibob]

In order to give proper context, this is what the bike looks like. It is not a rat bike.

[toyotaracer9]

You want the exhaust manifold to be as short as possible and dia. small enough to make the turbo spool, it uses heat energy. I wouldnt worry about making the gate open all the way, if your small engine ever gets to the 10lb gate open pressure all it takes is a tiny opening to keep it there. I was saying you want zero restriction after the turbo. I think you should try to get rid of the homemade intake plenum, may be too much psi pushing back on the compressor wheel.

[XLerate]

I'm impressed! Very nice workmanship and attention to detail, fine looking ride! Rats are cool but I like a class act to cruise around on if at all possible. Just shows more respect for the art of mechanical engineering, beyond the simple nuts & bolts of it! In a way our projects are a testimony to all those that went before us that it wasn't all a silly waste of time but rather there's a much larger thing going on, can't explain it. Well done there.

My knowledge of diesel theory is limited to say the least. However on a carbureted or injected gasser I can make a real pig out of one by over-fueling. Is it possible that too much fuel, evidenced by black smoke, is in effect quenching the fire in the combustion chamber?

I do recall from my Cummins and many posts seen on the 4BTSwaps forum that if timing is advanced it helps top end but partially kills bottom end. If bottom end is enhanced with retarded timing then it's going to take away from top end performance.

[Banzaibob]

The engine was donated by my uncle last year. He was a O/O trucker, his handle was "Red Devil." We lost him to cancer last fall.

[Banzaibob]

As an overview it appears that a lot of people on this board and others talk about how they are going to turbocharge. They give excellent details and summaries of plans and then at the moment of completion things go dark and you never get to hear the complete end of the story. Forgive me if I ask a taboo question but I often wonder just how often the results of major customization end in disappointment? Obviously I have to go back to the drawing board but I wonder how many don't? Is there anyone out there that actually has quantifiable success with this? By success, I mean consistent, reliable, improved everyday performance.

Part of the reason that the turbo plumbing is why it is on the bike is because I wanted the oil input to be oriented at 12:00 and the output to be at 6:00. The "clam shells" on the turbine and the compressor appear to be adjustable so where one can orient the intakes to accommodate the oil straight up and down. I could move the turbine side but not the compressor side. It almost appeared to be sealed. Can the compressor housing on the IHI RHB31 be removed (easily) as to re-position the compressor output?

I am going to probably use a smaller diameter pipe between engine and turbo and try to move it closer. I am a little skeptical that this would be the magic solution however. Any other incremental improvements that you would suggest? I'm looking for about 25-30% more performance still. BTW, another shot of the bike. I've written some articles for some of the mid-western/local Harley mags and I'm going to DARE them to do an article on this bike!

[toyotaracer9]

I think its the compressor housing that is clockable on this turbo, their are four bolts with small tabs loosen tap the cover away from the CHRA and clock it, If I remember corectly you have to go atleast far enough to hit the next bolt hole if you are using the wastegate actuator but to be honest I dont see that engine ever spooling the turbo past 10psi which is the gate cracking pressure.

[toyotaracer9]

Just looked at a pic of the turbo both sides are clockable but you would need to make it back to a bolt hole to keep the actuator rod straight.

[Banzaibob]

I have "clocked" it to a position that the turbine input is perpendicular to the oil inlet flow. With these positions I appear to have a lot more mounting options. In fact, I have enough room to basically make a short manifold and almost bolt it to the exhaust port. If I was to do this it would protrude out no further than the open primary. Am I going overboard with this short, smaller exhaust pipe? As it stands now I can also put the turbo directly in the cooling fan stream.

Does anybody, anywhere have formulas and/or volumetric examples that I can work with? It would be good to use a build that someone else did as a template right now, this turbo business is frying my brain.

[toyotaracer9]

try searching rbh3 rbh31 or rhf3 compressor map, should find some VE info . How many RPM is the engine turning when you were running 55mph?

[Banzaibob]

I have no way of knowing exactly what the rpm is at 55mph. My best guess would be around 3000rpm. A stock geared CB350 is turning about 5500rpm at 55mph and since my primary ratio is roughly half of the cb350, 3000rpm+/- would be my guess.

What precisely would a compressor map tell me? A formulation that could give me exhaust volume (VE?) for maximum power pre-turbo would be extremely useful.

[toyotaracer9]

http://www.ajdesigner.com/phpengine/eng ... ciency.php

How does it feel when its down one gear lower? Does the smoke clear up? Does it rev better?

[Banzaibob]

Before I added this turbo, I had the timing retarded slightly to give it better low rpm manners. When I would rev it to the governor in say 3rd or 4th gear it would misfire and pop a little as it topped out. 5th gear would hit 55mph but trying to go beyond that would just produce black smoke and no extra speed. With the turbo installed 3rd or 4th gear revs smoothly (but anemically) with no misfires but shift to 5th and it dogs down, billowing black smoke. When it is putting out 6-8psi of boost it sounds great, like it could rev forever. I think the internal of the engine have no problem dealing with turbocharging. However, it doesn't want to pull in 5th gear nearly as strong as it once did.

[toyotaracer9]

Sounds like turbo lag to me, and since its a manual trans. that small engine may never be able to overcome the lag. I would try to reconfigure the turbo with a straight pipe into the intake and straight pipe out the turbine see what happens.

Think of the "turbo manifold" you built as being a paper towel roll then have a 1/2" tube, blow through the 1/2" at a pin wheel it will spin pretty fast, blow through the paper towel roll it will hardly spin because you do not have the ability to produce the cfm it takes. same as your undersized engine isnt producing the cfm it takes to spool the trubo causing lag.

[toyotaracer9]

Another thing you may notice is most others with this single cyl. engine and turbo are running a CVT and can keep the rpms close to redline at all times.

[Banzaibob]

That could very well be however; I had it hooked up to a pressure gauge yesterday while riding and testing. At normal light to moderate throttle it was producing at the wastegate port, 2-3psi. Full throttle (in 3rd gear, 40mph) it would produce 7-9psi of boost. Overall however, it's performance was weaker than without the turbo. It won't hardly get out of it's own way in 5th gear.

With my obviously limited knowledge I conclude that 1) everything is hooked up correctly. 2) The compressor side is functioning in the way it should. Am I wrong in assuming that I simply have too much volume in my pre-turbo exhaust pipe therefore (perhaps) creating crazy pressure waves that hinder performance? Should I be looking for more precision in the exhaust volume? Intake (plenum) volume? AND....the big question, where and how would I come up with those numbers?

[Banzaibob]

I have also noticed that the guys with cvt's can simply pin the throttle in the church parking lot and wait for turbo magic. I think that a manual transmission is overall a lot more versatile for real street applications. However there is the challenge. Is there a way to tune these turbo's so I give up some on the top of the rpm range to have more useful power a little lower?