since there'll be no room for a crank wheel on the b21f+s+t thinger i'm working on, nor a distributor in the normal spot, i'm looking for a flywheel with the lh tone ring for the t5 swap. Anyone know where i could get one/have one?

You don't really want one, IMHO. They are just holes drilled into the perimeter of the really nasty heavy 9" flywheels. You can have an 8.5" flywheel drilled to suit the purpose - just take it to a machine shop and tell them what you want. Make sure you get it balanced afterwards.

You're sure you can't get a tone ring mounted on a crank pulley? I'm sure Dale and I can come up with something for you, incorporating all the pulleys you'll need in one shot.

hmm, i may have to hold off on this thing here for a little bit then and wait until i get the blower in it's final position....

the pulley i'll need will be very similar to the stock b21/23 ac part of the crank pulley with the 6 bolts on it. except in a 6-rib belt and somewhere between 5.5 and 5.75"... I'll probably be talking to you guys when i do get the thing mounted then i guess (was looking at using a stock ford 6-rib pulley and having it re-drilled, there are a few options for that too)

Well if you're creative and are willing to do without certain things (like the timing belt cover) we can mount the trigger wheel on the inside of the pulley, giving you plenty of room on the outside for the 6 rib job. How did you come up with that diameter?

Seems you'd need something like this...



that's mounted on Ian's V8 but you get an idea of what we could do...

depending on the boost i'll be looking to run/adjust... i'm trying to size the wheel properly so that i'll be able to have the largest range of boost available... since this is an overbore by .6 b21 i'm looking sizing everything to 128in^3 and knowing it'll end up being less. The blower and all to run 100kpa of boost (1atm) will be spinning at around 9400rpm and that'll leave the drive ratio around 1.3:1 (which i know is low, and may have belt slippage issues to deal with, but with the power tranmitted should still leave this in the okay-range after some calculations and a coefficient of friction of 0.3.)


so with the stock pulley on te blower being 3.75-3.8" a crank pulley size of 4 7/8" is probably optimal, but i'm working it all out on paper right now....

living without a timing cover is nothing new, lol.


on the new post, that's about exactly what i'd need! (or just a bolt-in adapter for where the a/c pump was)

On Ian's you can see the step on the inside where an Escort 36-1 trigger wheel fits. This whole contraption shouldn't be terribly difficult to build and design, but it WOULD be a custom piece and could take a while to get through the design/machining/anodizing phase.

Or we could build them in 2 pieces so you can have a bolt-on blower pulley and if you need to adjust it, it won't cost you as much to replace.

What blower are you running? I'll check your math if you like, not that I'm an expert and this is pretty much a WAG right now. Keep in mind your exhaust valve closing point, because that really affects the boost measurement.

What IS your setup, anyway? Are you doing a supercharged/turbocharged combination in series or in parallel? If you're running parallel, what are you doing to switch from one to the other, and how are you planning on unloading the supercharger? If you're running in series, how much boost from each device are you looking for?

i haven't actually taken into account the exhaust valve-blow-thru calculation, to be honest i've got no clue on it.

I'll be running an eaton m90 blower, genIII, with a 3.8" pulley, i'm thinking the 2-piece system will be the best, but i've gotta see how everything is going to mount up before i start making drawings.

as far as the setup goes, it's in series, but with a bypass around the blower once the turbo is up to boost (not true parallel because it has only 1 intake)

basically

Intake>>Turbo>>Super>>intercooler>>engine
V bypass^

bypass will likely be a 2" TB with either an electronic actuator controlled through MS, or a WG style actuator... another option i'm exploring is using 2-3 saab CBV's and some grainger valve action.

basically, i'm mounting a blower right now and dealing with the rest later.

Also, i KNOW the blower is greatly oversized, but since i'll be spinning it fairly slowly, it'll still be moderately efficient for a roots blower, even at decently high boost. The air will be hot, and the blower probably won't last long, but it's a fairly cheap project overall, and hell, if it works, it works, if not, then i modify for a nice expensive (lysholm-twin-screw?) blower later on down the road.

I don't know if there's any hard or fast rule to figuring out how much boost leakage goes on due to valve overlap, but if you can reverse engineer an existing engine it will help you determine this. It will all depend on the low-lift flow from each valve, plus how much boost is happening at the time. A good guideline would be to start with the existing Buick engine the supercharger came from, and downsize the pulley to suit.

Were it me building one, and I have considered it, I would run them in hard series without any bypass around the SC. The supercharger runs at a lower speed and with less heat, the turbo runs at a lower pressure ratio and again with less heat (you can even intercool between the compressors if you like, or water inject pre-supercharger), you get better scavenging and better volumetric efficiency due to the more favourable intake/exhaust pressure ratios, and you can run a bigger turbine than you normally would because not only does the engine seem lots bigger, but you're also not relying on the turbo coming on line as quickly as if it's your only power adder. It's also lots simpler than your electro-pneumatic plumbing bypass system.

I'd turn the supercharger fast enough to produce about 5-6 psi, tops. This will get the exhaust volume up instantly (like nitrous does) and will spool the turbo quicker. Feeding another 8-10 psi of boost into the supercharger will produce close to 20 psi in the manifold. It's the magic of combined pressure ratios at work, plus the reduced valve overlap boost loss because the turbo will bring up the exhaust backpressure, better trapping the supercharger air in the engine.

That's how I'd do it, anyway.

yeah, but the amount of blower i've got with this setup would make 5-6lbs quite a waste of power/weight of the blower, although the bypass adds a lot of complexity, i reckon ultimately i could run a massive sized turbo (t3/t4 or holset) and have it come onto boost quite late (4000-4500+rpm) and take over from the blower for more area under the torque curve (especially when the roots blower is freewheeling)

anyone know if a saab CBV is open on idle vacuum? how about the volvo one? if so, then it's really simple, use that to idle the engine past the blower, then as it revs up it closes, and use a wastegate for the big diverter from the turbo outlet pressure, soon as it hits the crossover point, use it to bypass the blower (with some hysteresis/overlap of course)

Blower is from a 3.8 gm Series II engine.

Okay, that's fine. I'm just telling you how I would do it. You don't actually have TOO MUCH blower for the engine - it's not a waste. You'd have to flow an awful lot of air through it at low boost to get the kind of power you'd be making, so I don't think it's a really goofy size for my application. You wouldn't be turning it that fast either, so it's not a large parasitic drag, and what parasitic drag there is would be offset by the much higher VE you'd get compared to running turbo alone. It's been done both ways, and it's generally accepted that either way is dead wrong: you should run turbo alone.

What else you'll have to watch out for is making sure the turbo can breathe when the engine is running on the SC - if you've got it shut right off, it'll run completely stalled and do nothing but build heat and damage the compressor, not to mention create a ton of backpressure. When the engine switches over to the SC, you'll have to be able to flow all the SC discharge back to the compressor without creating much drag either, otherwise you'll be sapping power turning the thing while on turbo.

Raz, can you turn that stupid word filter off please?

ahh, the nice thing is that the turbo is always having air through it, the air filter plumbs directly into the turbo, it's just post turbo where the bypass and blower is, and when the bypass is full open, the blower is still turning, although it's inlet and outlet are both connected to an open pipe more or less.

the other issue is where to put the throttle body, i'm thinking it SHOULD go before the super for safety reasons, but then that's a bit strange having essentially a massive plenum including the entire volume of the intercooler and blower piping. It'll probably go on the end of a b21f intake manifold.... we'll see, i pick up my chop saw today so i'll be able to get a move on it now!

Okay, well I'll be interested to hear how it all works. It sounds overly complicated to me and that you're ignoring certain benefits of the SC, and I can see a few other holes in the plan that would be deal breakers if it were my car, but it's not my car so have at 'er.

Specifically, if you're interested:

- The turbo discharge being plumbed to open atmosphere could present an overspeed problem. You'll be pounding a ton of air in using the SC, creating a ton of exhaust gas, and if you don't switch to the turbo in time, it could explode.

- The valves dumping the turbo and connecting it to the plumbing. There will be a time when the plenum is able to dump to atomsphere, during the time that the valve is closing off the turbo dump and connecting it to the intake. At this point your manifold pressure will drop to zero, and since your turbo and intercooler are at atmospheric pressure too, it will take a half step for the boost pressure to recover. There will also be the synchronization between the valve that dumps the turbo compressor to the one that dumps the SC...

- Putting the TB in front of the SC will cause two problems: First off, the SC will be under vacuum part of the time, which isn't really much of a problem unless it starts sucking lube out of the bearings. AFAIK, the Buicks run this way, so it shouldn't be a problem at all unless your seals start to go. The real problem is that if you plumb things the way you're proposing, what's going to control the engine when the turbo is bypassing the SC, and no consumable air is passing through the TB?

- You're giving up many of the benefits of the SC by not using it all the time. Turbo engines built for the street have awful volumetric efficiency because of the crazy exhaust backpressure the turbo puts on the engine. Typically on a 15 psi boost motor, the backpressure will be 30-45 psi. After blowdown (the initial rush of high pressure exhaust when your valve opens) there is always a struggle to get ALL the exhaust out of the cylinder. What's worse is that when the intake valve is opened, there is that 30-45 psi of pressure still trapped in the cylinder, and it's all exhaust gas. This overcomes the 15 psi in the intake manifold and blows out the intake valve, and displaces good, burnable air/fuel. Worse yet is when a camshaft with lots of overlap is used, and that exhaust pressure actually blows right through the cylinder and into the intake, contaminating the charge even further.

With the SC, you'll be contributing to the intake pressure without creating any more exhaust pressure, and you'll either reduce or negate the reversion coming from high exhaust backpressure. This will allow you to use a wilder camshaft and make yet more power, and since you won't be relying too much on a snappy responsive turbo, you can use a bigger turbine than you normally would, which also reduces the exhaust backpressure. These two things alone should more than overcome the power lost to driving the SC.

- There is still the question of how are you going to control the switchover between turbo and super chargers. Are you going to use an RPM sensor on the turbo compressor to know when it's spinning fast enough to take over? Are you just going to rely on engine RPM or boost pressure, hoping that everything behaves linearly and instantly no matter what gear you're in and what load you've got on things? If you're going to do it mechanically and on the cheap (as it sounds, by your questions about CBV valves) what's going to control the pressure signal to the valves?

But those are my thoughts. The simplest and probably best thing would be for you to get a really well designed header, a properly sized turbo, and forget about the rest. It sounds like you're doing this as an engineering exercise, so simplicity isn't really in the cards for you. I would still go with turbo -> intercooler -> throttle body -> super charger -> maybe water injection -> intake, without any funkyness in between. It'll be hard enough getting all that working harmoniously without adding any other complication.

i think we're miscommunicating slightly on how this system works in a few spots.

it'll go intake > turbo > TB > super > intercooler > engine

or

it'll go intake > turbo > super > intercooler > TB > engine

the only difference is that there will be a circuit bypassing the supercharger at idle (Probably using a CBV and a check valve) that will help to bring on boost a bit softly, and a bypass of the supercharger (Inlet of super to outlet of super) for when the blower would be a massive parasitic drag. This would be controlled by a wastegate actuator referenced to boost on the pre-super/post-turbo side, basically when the turbo gets over the boost of the super, it switches everything over and around the super so that it essentially freewheeling. There will also have to be some kind of bypass/dump valve for getting on/off throttle, probably just a normal BOV on the cold side of the intercooler.

You are right in the fact that i do lose the benefit for forcing air through the motor in overlap, but that's only when the super is bypassed, and that's at moderately high boost with the turbo spooled up.


It is very true that i've go no effing clue how this system will actually behave once it's in the car, which is half the reason for setting it up like this for now, piping can always be rerouted and small things changed. or if it really sucks i can always mount the blower on the 960....

fwiw there's an LH2.4 manual 240 in the pyp right now