Supercharged om617 powered scout build

[Blownoiler]

That's an interesting project experience you went through. How is it you were getting 4psi at idle and not much more at higher rpm? It seems like that much boost at idle is unnecessary and inefficient. I'll have to do some reading. I don't know a whole lot about the supercharger you used.

Leakage between the rotors and case is normal at low speed in these rootes chargers, I don't know if the magnussen charger is different or not in this regard. I was fine with 4 pounds of boost at idle, it made for good cylinder filling which leads to a good clean burn (remember I was using veg oil for fuel most of the time- and I retarded the camshaft timing to shift the torque curve higher up the rev range-the later closinjg intake valve allowed a small amount of reversion at the end of the intake stroke so dynamic compression at idle was a bit lower than standard). 10 psi boost was available if I kept the v belt tensioned enough to avoid slippage, the boost jumped from 4 psi at idle to 8 or 9 pounds at about 1400 revs from memory, (EDIT....I bypassed some of the charge air to run the engine at lower boost levels to see how it would affect engine temps/big end bearing wear) taking off in 1st gear nearly gave me whiplash, so often I would take off in second gear at the risk of burning the clutch plate out. Honestly it felt like there was a much bigger engine under the hood. Acceleration from 2500ish to 4000 was about the same as the turboed performance until I retarded the camshaft, but I didn't find enough spare time to try many other mods so didn't perfect the setup. The Toyota S.C.14 is a crap charger, the shaft bearings are held in the case by some type of epoxy/plastic surround, so overheating the charger by using 14 plus pounds of boost is a no-no, these chargers came out on Japanese delivery luxury car petrol engines, and had a clutched serpentine belt drive as the petrol engined setup only engaged the charger at full throttle, the rest of the time they were bypassed. I knew that they were a poorer quality charger than many others before I purchased it, but at less than $500. delivered to my door (secondhand imported) I couldn't resist the temptation to try one out. The charger puts out 1400 cc s of air with each revolution, so was sized about right for the 2.4 litre diesel engine which has a redline of 4000 revs. Have you done the mathematics to work out how fast you have to spin your charger to get the lb.s of air required for your expected performance level?

 

[rembrant88]

I didn't for the mercedes. Bigger isn't always better. After you brought it up I went to the compressor maps and drawing board. From what I can tell the m90 will be out of it's efficiency range with the amount of boost I want to run. I would have to run a lot of boost up high to get in an efficient spot at cruising rpms and by doing so will have much higher boost levels there. I didn't think the m90 would flow too much but in this low boost application I think it will. The m45 might be right on for it, or at least as close as I'm going to get. I want to keep the boost decent at mid rpm and try to stay within the superchargers most efficient range on the high and low end. The m90 just doesn't seem to fit in with my plans, so I think over the weekend I'll do the math and see what I'm going to get throughout the rpm range with all three Eaton options.

 

[Blownoiler]

I would assume that there are various diameter pulleys available for the m90, giving some adjust-ability to the final lbs/min. airflow, I don't know how a different pulley would affect the flowmap when matched to a particular engines airflow characteristics, the sc14 raised inlet temps to over 100C when running 10 pounds of boost which I thought was on the high side, however I recently saw some figures for the turboed engine and it was giving much the same inlet temps at that boost level, so the charger wasn't as inefficient as what others had led me to believe. The stock turbo engine used 7-8 pounds of boost to hold the hyway speed limit (100 km/h) (3000 revs), after some mods to improve v.e. boost required for 100 km/h dropped to 3-4 pounds, with the charger in place with no bypass it was making 10 pounds of boost at the same speed when all that was required was 3-4 pounds so thats why i suggested running an active bypass when cruising at part throttle- less heat=longer engine life, plus less pumping losses = better fuel efficiency. A lot of people condemn supercharged diesels, yet I bet they have never built or driven one, usually they come up with silly comments like "the supercharger will consume more power than what it will make" or the equally silly "your mileage will plummet", I can only assume that these people are turbocharger vendors trying to maintain their market sales, it's good to see someone trying something different

 

[rembrant88]

I would assume that there are various diameter pulleys available for the m90, giving some adjust-ability to the final lbs/min. airflow, I don't know how a different pulley would affect the flowmap when matched to a particular engines airflow characteristics, the sc14 raised inlet temps to over 100C when running 10 pounds of boost which I thought was on the high side, however I recently saw some figures for the turboed engine and it was giving much the same inlet temps at that boost level, so the charger wasn't as inefficient as what others had led me to believe. The stock turbo engine used 7-8 pounds of boost to hold the hyway speed limit (100 km/h) (3000 revs), after some mods to improve v.e. boost required for 100 km/h dropped to 3-4 pounds, with the charger in place with no bypass it was making 10 pounds of boost at the same speed when all that was required was 3-4 pounds so thats why i suggested running an active bypass when cruising at part throttle- less heat=longer engine life, plus less pumping losses = better fuel efficiency. A lot of people condemn supercharged diesels, yet I bet they have never built or driven one, usually they come up with silly comments like "the supercharger will consume more power than what it will make" or the equally silly "your mileage will plummet", I can only assume that these people are turbocharger vendors trying to maintain their market sales, it's good to see someone trying something different

I want to run around 7 psi at 2000 rpm, with my gearing and tires the engine will be running just over 2K at 65mph. With the m90 no matter how I look at the flow map it will be running out of the efficiency island on this motor. I know that in most applications it is better to go with a bigger supercharger for future power increases but I believe that idea often leads people to forget to look at the data. I'll post sometime showing where I want the boost to fall on the map. It looks at a glance like the m45 will be the most efficient supercharger for the engine. Seems small to me but I'll just believe the numbers . I will definitely look into bypassing some of the boost when cruising. And after it is all together I'll look at intercooler options and do a test to see how much is gained by adding one. I'm sure it will be substantial even if I don't necessarily need one at low boost.

Yeah, I've had people tell me things like that, mileage will plummet, or I'll blow up the motor. I have to tell them its not like I'm going to run a 671 at 40psi or something. People do exaggerate the differences between turbos and superchargers. Both power adders do fine on gas applications and the advantages and disadvantages of both are well known and spoken of often in the gas engine world. But for some reason many think this doesn't translate over to diesel engines, which is ridiculous. Both have their advantages and to get the most out of either option takes a logical look at what best suits the motor and then tuning from there.

 

[Blownoiler]

I use the Garrett boost advisor ( http://www.turbobygarrett.com/turbobygarrett/webadviser ) to give me pounds of air required for a particular horsepower level, mostly because the garrett program has a diesel input so that you can adjust the air/fuel ratio to your desired number. I use 20-1 air/fuel ratio because I want to keep smoke levels down to near zero on my daily driver, but for offroad performance you can go richer than this to get more power if you can put up with an increase in visible tailpipe emission. One of the more difficult problems to solve when experimenting with diesels is the rate of airflow through the engine at any particular rpm point, because the fuel injection amount is the same for all 4 cylinders (mechanical injection pump/injectors) and is also much the same as revs rise, we really need a near linear airflow increase as revs rise, so pulse tuned manifolds can make tuning a bit tricky if they increase v.e. too much at a particular rev level at the expense of the other parts of the rev range, You can get a beneficial Helmholtz effect from the aircleaner case as any sudden large opening in the inlet tract creates the Helmholtz effect, I tuned mine to give the inducted air a kick in the pants at cruising speed (3000 revs) by trying different lengths of pipe attached to the air cleaner case, around 36 inches worked well, and the pipe was routed out of the engine bay to a cool air pickup point and also had a bellmouth added onto the end, nothing tastes better than a free lunch! Helmholtz tuning isn't mentioned much , but should be because the diesel is always at full throttle as far as the air intake is concerned so the pulse is always there and are always strong. Thats enough rambling for one night, keep the posts coming!

 

[rembrant88]

Not many people have considered the Helmholtz effect on a diesel but you are spot on. To tune an engine for it complicates the already tedious task of building a forced induction system for an engine, so maybe that's a reason. And the benefits are a little harder to grasp because they are not obvious. Every little bit helps. How did you test the motor to see when you were making an improvement? Did you test it on a hill or just while cruising?

 

[Blownoiler]

Not many people have considered the Helmholtz effect on a diesel but you are spot on. To tune an engine for it complicates the already tedious task of building a forced induction system for an engine, so maybe that's a reason. And the benefits are a little harder to grasp because they are not obvious. Every little bit helps. How did you test the motor to see when you were making an improvement? Did you test it on a hill or just while cruising?

I decided to change the factory air filter inlet pipe to a cold air source outside of the engine bay, the original pipe sucked air from behind the headlight so was picking up warm/hot air while driving around town. My first attempt netted a power loss, yet in theory should have given a denser charge so I was expecting more power,not less, it felt like the handbrake was on a notch. After trying 2 or 3 different pipe lengths I got back the power and found some more, most noticeable at cruising revs (3000), slightly less boost needed to cruise was a bonus! The 36 inches I quoted earlier is what I added onto the O.E.M.s length of about 13 inches (starting from the filter case), so 45 to 50 inches total length from the filter case would be closer to the mark. The stock Toyota 2lt is not an overly powerful engine, I think that about 60 rear wheel horses is about it so small gains are easy to feel and measure with rolling road tests timed with a stopwatch and the speedo (and of course the "killer hill" test and the "boost required to hold cruising speed test). I have been reading up on intake manifold design for turbo-diesel engines recently, it's a bit hard to find info on, mostly because of the diesels engines need for a relatively consistent flow of air from idle to red line, if I used the petrol (gas) engine design rules then it probably mean excess smoke (and high EGT's) when the manifold isn't in it's best V.E. range ( because the injected fuel amount is close to linear as revs rise when using mechanical injection), so I am basically using the Banks power big hoss manifold as a guide. I'm modifying the stock manifold to flow better while retaining the basic runner length and plenum volume. The inlet runner cross sectional area is what largely determines the V.E. so going bigger takes the torque peak higher up the rev range (which some older diesels generally need...especially older design supercharged diesels I.M.O.) at the expense of less inertia ramming effect at lower revs, yet frictional losses go down with the larger cross sectional area, I'm coming to the conclusion that a larger cross sectional runner will improve fuel economy at part throttle but the trade off may be less overall power, but some tedious cut and try hours are going to show the end result..this may take months to do so don't hold your breathe waiting for the end result! I had to drive into town yesterday, and noticed that I was being followed by a police car , the highway patrol type for a good 5 minutes through a few sets of traffic lights, obviously the lack of smoke emmited from my exhaust got me off the hook and I didn't get pulled over, that alone makes a smoke free diesel worth striving for. One mod that is on the "to do" list is to hook the boost compensator up to the inlet manifold after the top mount intercooler rather than off the turbo as this will more closely reflect the amount of air entering the cylinders, so should allow some fine tuning of fuel addition. The boost compensator works well with a supercharger, at idle (4p.s.i.boost) I used the main fuel screw to richen up the mixture to just below the point of smoke, then as revs rose and boost went up I tuned the boost compensator to add additional fuel, although you can use a non turbo pump if thats all that is available, it's just easier to get no smoke for the same power output with the compensated pump.

 

[Blownoiler]

Here's a graph showing just how much V.E. varies throughout the rev range with different inlet manifold runner lengths:

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[rembrant88]

I got the engine pulled and as you can see, some parts taken off. Air conditioning, don't need that. Manifolds aren't needed. Power steering pump I'll keep around just in case. Turbo is going by by. The flywheel is going to be close but I don't care if I have to re drill it, no biggie. Now it's time to build the adapter and see if I can get the transmission to mate up. Unfortunately one of the flywheel bolts stripped. I hate ten point sockets and these are to shallow to be torqued that tight.

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[rembrant88]

I'll have to build an adapter for the bell housing and line up the starter.

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[rembrant88]

I decided not to risk dealing with the cast flywheel so I'm having one made out of aluminum. Doesn't sound like the stronger option but after some convincing I realized it's the best way to go. I thought a machinist was going to take a punch at me for even mentioning drilling out the cast flywheel. Didn't sound like a good idea to me either because it may cause cracking, I just figured that because the adapter kits being sold require flywheels to be welded and re drilled that it wasn't a problem. I'm having it CNC machined keeping the original form of the scout flywheel except that it will have the bolt pattern of the mercedes flywheel. It will also accept a Forenza friction plate so as not to wear out the flywheel itself. I hammered off the cast gear ring so it can be pressed onto the aluminum flywheel when it's finished.

 

[rembrant88]

Here's a graph showing just how much V.E. varies throughout the rev range with different inlet manifold runner lengths:

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That attachment doesn't work. If you get a chance to post a link I'd still like to look at it.

 

[rembrant88]

Turns out the m90 as well as the m62 will be way out of their efficiency range on this motor. I'm going to go with the Eaton m45 off a mercedes kompresssor. Here is an idea of what I'm working towards. As long as I get the psi I'm looking for in the efficiency island at 2000rpm I'm fine with everything else. This motor isn't going to be run above 3,000rpm anyway and if it is there will still be a bypass.

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[NapaBavarian]

Funny, 've been thinking about doing that exact same thing...

 

[rembrant88]

I wish someone would do it and see how it works, I would like to be the first . Seems I keep getting stalled though. My brother broke two ribs the other day, and that came after having his cheek bone crushed by a hammer drill. I hope he gets better because I know how much he wants to finish this project up.