cam belt to drive supercharger

[roadrunner]

Generally cam gears from the same engine are 1:2 ratio , you can use 2:1 depending on your charger, but you can aways try different teeth number pulleys from another engine.

I have 3 pulleys so far, 42, 28 and 21 teeth, and am leaning toward the 42 driving the 28 tooth cog, which will give around a 1.5 driven ratio. I did a rough calculation using an M112 charger and aiming for 14 pounds of boost, I need a 1.44 ratio. I factored in a local elevation of 400 metres, as ambient air pressure is only around 14.1 psi here, also I'm reasoning that at the relatively low drive ratio there will be some blower leakage at normal cruise revs. The engines camshaft has 50* of overlap (workshop manual figures), so I was thinking of oversizing the headers to allow plenty of blow through for exhaust valve cooling and residual exhaust gas flushing, obviously I'm still in the planning stages at the moment.

You can fab a tensioner, to adjust the belt tension and improve the contact pattern on the smallest pulley. This will improve its durability also.

Noted !

[roadrunner]

I just found a mistake in my previous calculation, I wrongly used the engine displacement of 3069 cc, when it is actually 3059 cc, so I redid the calc using some new figures- 11 (required psi boost + .2 (camshaft overlap adjustment figure)+14.1 (air pressure at this elevation)x3059 (engine displacement)=77392.7 divided by (1835 (charger displacement in cc's) x2 (four stroke engine I presume) x 14.1 (ambient air pressure) =51747 77392.7 / 51747= 1.49 ratio, which fits the present 1.5 ratio pulleys, what other factors can I take into account in the calculation?

[Kevin Johnson]

Max Rockatansky -- you need his setup.
Har Har, you crack me up Kevin, ... it's too bad that Max's blower was a fake!...

https://www.google.com/patents/US2709507 Easy enough to set up. Anybody remember the Ferlec clutch in old Renaults? Air conditioner compressor clutch is too obvious.

[roadrunner]

Max Rockatansky -- you need his setup.
Har Har, you crack me up Kevin, ... it's too bad that Max's blower was a fake!...

https://www.google.com/patents/US2709507 Easy enough to set up. Anybody remember the Ferlec clutch in old Renaults? Air conditioner compressor clutch is too obvious.

Mounting two ex-mercedes Eaton m62's would save fabricating an on/off drive, (using just one wouldn't pump enough air unless I threw a fairly large drive sprocket onto the crank snout), I wouldn't have much confidence in a clutched drive whipped up in my shed, especially when my tool box (along with my engineering skills) are both lacking. I have toyed with the idea of twincharging, possibly running an eaton blower for low end grunt along with a turbo for the top end duties, but that would require a decent turbo manifold (they don't exist) and a turbo sized accordingly, I would rather pull the turbo off and just run a crank driven charger if I can work out how to manipulate the power curve to keep good top end power . The few supercharged idi's that I have seen have great low end grunt, but don't make anymore power up top (3000 to 4000 revs) over the standard turbocharged setup. Possibly this is in part due to people choosing relatively small displacement blowers, as the power required to drive them doesn't go up in a linear fashion, but by the square of the increase in blower speed. I believe that a larger blower in relation to the engine spun slower would have less parasitic loss, so that's one tick in the search for better top end power, now if I can only work out the other 10 ticks

[Warpspeed]

Supercharging a diesel is very different to supercharging a petrol engine.

With a petrol engine the air is throttled and the supecharger airflow is is also throttled, so that at small throttle openings there will be no boost, and the blower will be esentially running unloaded.

With a diesel if set up for 14psi boost (as you are suggesting) the engine is always going to be under boost as the revs rise because the airflow is not throttled.

That does not happen with a turbodiesel, because at small throttle openings there is very little fuel flow, very little exhaust heat, and the exhaust turbine has nothing to work with.
It's the exhaust heat and resulting exhaust gas expansion that drives the turbine and compressor into boost when at full throttle/full load on a turbodiesel.

With a constantly driven positive displacement supercharger fitted to a diesel, there will be full boost available all the time, even when going down very steep hills with your foot on the brake.
Not really a problem, but the blower is going to be working pretty hard all the time, blower heat and blower noise may be higher than you are expecting.
The parasitic power to constantly compress all that extra unwanted air is not going to improve fuel economy either.

You will recover some of it, because boost pressure will drive the pistons down the bore during the induction stroke, but driving a roots blower to 14psi still requires quite a lot of drive horsepower to do.

An M90 is too small for non intercooled constant 14psi on a three litre engine, it will probably need to turn about 2.5 times crank speed to achieve that.
The M112 is a much better idea.

For side mounting on an inline engine, the best roots blower version to get would be the M112 fitted to the V8 Jaguar engine.
This mounts "upside down" with the intake at the back, and the discharge on top.
It has three sturdy mounting feet that readily bolt to the usual bosses found on the sides of most engine blocks.

All the other Eaton roots blower versions use the discharge flange to mount the blower which is very inconvenient for side mounting on an inline engine, and much more suited for mounting on top of a vee engine.

Here are some pictures of the "upside down" Jaguar M112:
https://www.google.com/search?site=imgh ... jo3qJLi4bY

[roadrunner]

Supercharging a diesel is very different to supercharging a petrol engine.

Yes, I know, maybe that's part of the attraction, doing something different to the mainstream diesel guys!

With a petrol engine the air is throttled and the supecharger airflow is is also throttled, so that at small throttle openings there will be no boost, and the blower will be esentially running unloaded.

With a diesel if set up for 14psi boost (as you are suggesting) the engine is always going to be under boost as the revs rise because the airflow is not throttled.

That does not happen with a turbodiesel, because at small throttle openings there is very little fuel flow, very little exhaust heat, and the exhaust turbine has nothing to work with.
It's the exhaust heat and resulting exhaust gas expansion that drives the turbine and compressor into boost when at full throttle/full load on a turbodiesel.

With a constantly driven positive displacement supercharger fitted to a diesel, there will be full boost available all the time, even when going down very steep hills with your foot on the brake.
Not really a problem, but the blower is going to be working pretty hard all the time, blower heat and blower noise may be higher than you are expecting.
The parasitic power to constantly compress all that extra unwanted air is not going to improve fuel economy either.

You will recover some of it, because boost pressure will drive the pistons down the bore during the induction stroke, but driving a roots blower to 14psi still requires quite a lot of drive horsepower to do.

I intend to run a bypass valve for cruise conditions, Eaton quotes 1/2 kilowatt for pumping losses under bypass conditions, (around 2000 engine revs) which is reasonable in my opinion. I have p/d charged 2 older Toyota diesel engines previously,(both N.A. and turbo) using an s.c.14, somewhat reluctantly after being told by most of the internet diesel engine mod brigade that it wouldn't work, well, it did work, with heaps more low to mid range grunt, along with similar top end power to the previous turbo setup. The extra grunt via supercharging has me hooked, but there were some minor problems with engine vibration and it ran a bit hot with the n/a engine (21-1 compression ratio+10 pounds boost +lightened flywheel) The turbo engine didn't have this problem due to having a 19-1 c/r, standard flywheel and an injection pump calibration more suited to forced induction, but it did suffer from blower belt slippage, along with excess blower whine noise levels. Fuel usage went from 12l/100k to 14 litres/100k (if driven sensibly ha!) so I'm expecting similar mileage figures to the turbo numbers, especially with the cruise bypass valve built into the Eaton chargers.
If my budget allowed I would buy a TVS 1320, which would give 70-75% efficiency for my intended use, but until I win lotto I can only afford an old tech charger.

An M90 is too small for non intercooled constant 14psi on a three litre engine, it will probably need to turn about 2.5 times crank speed to achieve that.
The M112 is a much better idea.

For side mounting on an inline engine, the best roots blower version to get would be the M112 fitted to the V8 Jaguar engine.
This mounts "upside down" with the intake at the back, and the discharge on top.
It has three sturdy mounting feet that readily bolt to the usual bosses found on the sides of most engine blocks.

All the other Eaton roots blower versions use the discharge flange to mount the blower which is very inconvenient for side mounting on an inline engine, and much more suited for mounting on top of a vee engine.

Here are some pictures of the "upside down" Jaguar M112:
https://www.google.com/search?site=imgh ... jo3qJLi4bY

The M112 does look like a good choice, Thanks for the tips!

[Warpspeed]

I was thinking about a bypass system after I had made my last post.

After being involved with several twincharging projects, I know a bypass system can be made to work extremely well around a roots blower.

You will not find a Jaguar M112 in Australia in good condition for a sensible price.
They are much more common in Pommy Land and the USA, much cheaper as well.

The difficulty is that many sellers in both countries are often not willing to ship to Australia, but if you keep looking you will find something.

I bought one of these Jaguar M112s from USA about two years ago on e-bay.
It was $929 shipped to Melbourne which was a good price at the time.
Its in fantastic condition, very pleased.
It also inlcuded the outlet cover/manifold which might make installation neater and easier.
This turns around and can either face forward or backwards.
The blower outlet of this has two round splayed 50mm pipes which can be sawn off, and extensions tig welded on to point in any required direction.

Sounds like a very interesting and unique project.

[roadrunner]

I was thinking about a bypass system after I had made my last post..

The engine's present IHI ball bearing turbo is actually quite good as far as 1990's turbo's go, although the turbine is on the small side, I get 3-4 pounds of boost while going downhill at hyway speeds with no throttle at all (2600 revs), and 5-6 pounds of boost at 100 k/h if there is no headwind on a level road. I think that I could cruise at the legal limit with 1-2 pounds of supercharger boost due to the much better pressure differential across the intake/exhaust when running a correctly sized/designed exhaust system. In theory I could easily change the rear diff centre to get lower cruise revs with a crank driven charger, which would result in a gain in mileage, and lower noise/wear, but theory doesn't always work in practice (although in this case I think that it will when pumping/friction losses are considered) . One of my major concerns is lack of egr when running a blower, with little or no exhaust backpressure there will be no residual exhaust gas left behind in the chamber on the cam overlap, which will most likely result in much higher peak temps and pressures on the power stroke- the enemy of the IDI diesel, I'm not sure about how to tackle this potential problem. Water injection comes to mind, as does retarded injection timing, but as you probably know a mechanically injected diesel engine (bosch rotary pump) doesn't allow much in the way of tuning fuel injection quantity in relation to crank degrees, and being a turbo engine the compression ratio is already on the lower side. This car is my daily driver so reliability is no 1 on the list. To add another complication, I run this engine on used cooking oil, so reducing the compression ratio isn't going to help to get a clean burn of this shit (but cheap) fuel. Forget about in cylinder pressure sensing equipment, dollars I don't have...any thoughts?

[Warpspeed]

I have never owned a diesel, and really know nothing about them.
At least a supercharger bypass system could be arranged to control the amount of boost, and when and how that boost is applied.

[roadrunner]

I have never owned a diesel, and really know nothing about them.

Neither had I until my boss asked me to get rid of 40 litres of used cooking oil every week, so I bought a N/A diesel vehicle. They are noisy, vibrate, lack power and like to smoke. (sounds like my ex wife) I should add that I stopped losing points off my license when I started to drive diesel powered vehicles, but then advanced to turbocharged diesels, a huge leap for mankind!, and have now started to lose license points again

At least a supercharger bypass system could be arranged to control the amount of boost, and when and how that boost is applied.

Exactly! Superchargers are underrated, from the 80s until now the turbocharger reigned supreme, now it is the superchargers time to evolve- http://www.engine-expo.com/forum_2009/p ... alling.pdf
http://papers.sae.org/2012-01-1941/

[In-Tech]

I have a used whipple 1.6l screw in perfect condition that I was going to use for my flow bench if that would suffice for your application. Personally, as to your original question, I'd serpentine drive it. Nothing wrong with the cog but in my mind excessive idling will probably cause gear problems in whatever charger you choose. PM if interested in the screw charger.

[stealth]

They do make some very wide serpentine belts. Large diesel trucks use a very wide drive belt.

[In-Tech]

Yes on the belts, alot of available lengths, I just made a whipple kit(2.9L) for a 2011 LS9 ZR1 vette and I used a 12 rib belt to get the right length and just cut one rib off to make it the same as the stock 11 rib.

[jlmccuan]

I have a friend who runs the MB blower, complete with electric clutch, on a Studebaker 6 displacing 190 cu. in. Works great and really makes a big difference when you punch the button.