Inliners International Forums General Discussion Blown and Injected Bonneville Blowers to inline 6

Arguements on line is like an arguement with a spouse.
There are two rules:

Rule #1: You never win the arguement.

Rule #2: The next word you say is the beginning of the next arguement.

Mike

cheers to that , mike. well put. now let's quit ruining this thread. tom

Gentlemen, I've been away from the BB for a while, and seem to have dropped back in into a pile of chicken litter.

Back to business: James, Armond, Samwise, there is a cheap and simple way to center the supercharger on the head. But it would not be pretty, and thats the reason I didn't use it on my roadster. You could build a jackshaft, mounted on brackets attached directly to the manifold. (that means a total of 4 pulleys, 2 belts). The supercharger can be mounted with the discharge facing the head ports, and I considered doing just that, but it fit better around my headers like I did it. This winter, I modified the carb to "calibrate" it to supercharger duty. What I did is not easy to explain and the photos did not turn out well, but if you're interested, I will explain it later. Samwise, I have trouble remembering numbers, but I think the 3800's would boost up to 11-12 psi. I limited mine to 7 psi for longevity. I put 6000 miles on it last summer with no hitches. I just now finished putting a little heater (engine coolant) on the bottom of the carb plenum to keep it warm. The main manifold stays warm from exhaust header heat, but the carb plenum always ran COLD with condensate forming on the outside. So I figured the same thing was happening with fuel on the inside, even though I couldn't tell it performance-wise. It's rained here almost every day for 2 weeks now, so I can't tell yet if it has helped. (fuel mileage hopefully)

If I can help you in any way, let me know.

pappy

Hey Pappy, nice to see you back and in the middle of it. I did think of using a jackshaft and have an air conditioner compressor for the shaft and the clutch. I thought what the heck might as well stop the whole thing from turning if it's not boosting. Mercedes did this. In the end, I'll lengthen the snout. The Studebaker is taking all my energy right now. We want to fire it up this week.

Armond, good luck to you & Leo with the Stude this year.
Give Leo a hug for me. just kiddin.
pap

might as well stop the whole thing from turning if it's not boosting. Mercedes did this

That's a useful mod.
If the blower stops, obviously almost all the power lost in the drive comes back (except for belt friction to the clutch, and the clutch hub bearing).
The bypass, of course, now sees only vacuum (since nothing is satisfying engine demand under the rotors), and remains open, diverting air or mixture from the carb right to the manifold no matter what the throttle position.
IIRC Magnuson sells a stand-alone bypass valve.
The Mercedes M62 application (2.3 liter L4?) shows that the bypass area is enough to cruise the car with the blower stopped.
I'll bet the Mercedes clutch is keyed to vacuum so that the blower engages on full throttle, and the boost closes the bypass.
If you're going to use an A/C clutch (which is solenoid operated by a switch) I'd use a relay and a kick-down switch on the carb secondary linkage etc. rather than a vacuum switch, which will operate differently depending on which gear, hills, etc., and may induce knocking.

Easiest (?) would be a jackshaft as Pappy suggested but the idea of incorporating it into the snout extension has some merit as well. It would be clean there. Another way would be to simply have a switch, AK "Road Warrior" style. Switching the blower on and off at the correct times to make a smooth transfer would be the ticket in my eyes. I'm using a carb base as my bypass valve, it's larger than the Mustang's and should support just about all normal driving conditions (HA!, like my foot's going to let that happen). The compressor's pulley is too large and it will be a trick to get it down to size. Just details.

A nice jackshaft feature is that the 2 pulleys need not be the same size or shape.
Depending on what you have for the crank and blower, you may need more or less than the ratio of the 2 diameters: make the input side (crank driven) larger or smaller than the output (drives blower) side, and multiply that ratio by the existing.
E.g., crank is 9", blower is 6" (1.5:1), but you want 2.5:1.
Use a 5" on the drive from the crank and a 3" on the drive to the blower (1.67:1).
1.5 (existing ratio) × 1.67 (jackshaft ratio) = 2.5:1.
Sometimes you have too much ratio: the blower pulley is 3", giving 3:1. Slow this down to 2:1 by using a 4" on the driven side and 6" on the driver side: 4:6 = .67:1.
3.0 (existing ratio) × .67 (jackshaft ratio) = 2:1

In addition, it may permit you to save work in 2 ways:
1. use an existing multi V-belt pulley on the crank
2. use an existing serpentine (multi-rib flat belt) pulley on the blower
How? The jackshaft has a dual V pulley on the input side (common automotive or industrial part), and a serpentine on the driven side.

Yes, quite doable. At heart, I try to boil things down to the very simplest form a system can be at and still be fully functional. I put myself through college building custom choppers. Ended up a licensed aircraft mechanic (helped build the formula racer "El Bandito"), worked as an engineering liaison at an optical firm building prototype production equipment. A bunch of other stuff as well, Bonneville to drag cars. For me it isn't just a machine but an extension of myself and if I'm going to remember how to work on it tomorrow, it had better be simple!

Now the practical questions:
Do you have an extra row on your existing (or spare) crank V-belt pulley?
If not, are there other pulleys available (JY) with extra rows for A/C, etc?
If such exist, what's the OD?
This is going to limit your ratio.
Typically, the M90 doesn't turn very fast, about 2:1 on the V6, but could be faster on your 250 since I don't think you're going for max power at 6,000 RPM?

Ok, I have a 7 inch crank pulley, six rib, no V belt, no a/c. There isn't room for any more on my '41 Chevy truck. Stock 3.8 inch Bonneville supercharger pulley but aftermarket pulleys can go down to 2.8 inches. It is a 230 (3.8L) 5,000 RPM is all I'm going to ask out of it (RV cam). The alternator has a 6 rib pulley and will be the tensioner. M90's have a 1.5 L capacity.

How much boost you want, Armond?

I'd be included to just try it out using what you have.
The worst would be too much boost, and I'm sure there are larger blower pulleys available to slow it down but they need a puller to R&R.
If it's going to be a draw-through you can (temporary) restrict the air inlet at the TB flange which will reduce boost, but I suggest this only for testing since it also increase load and raises air temp.

A friend of mine had an SSEi B'ville for a few months (he worked for a dealership, it was a trade in), IIRC he was saying they were running just over 8 psi on the stock 3800.

I have no idea what size the crank pulley was though.

8 pounds is about what I'm hoping for. It would be good to know what a stock early Bonneville pulley is. Does anyone have a formula for calculating boost? This is the one I have but it seems to underestimate reality.

(Super Charger Disp/1/2 Engine Displacement) * Ratio * 14.7) - 14.7 = Boost Pressure

it seems to underestimate reality???

That's the one i use.
It should get you to within 10-15%.
Your cam overlap and exhaust backpressure have a big influence, though.

FWIW there is a performance blog about one of the T-Bird Super Coupes that a fellah was 'tweaking' that he included the testing he did before and after each mod (along with dyno time IIRC).

Can't seem to find it now, but it goes along with what jlgrooms said, he actually lost a small amount of 'boost' when he got a free-er flowing exhaust on his car, but picked up some HP and Torque as well as lowering the EGT (in the beginning he measured the exhaust pressure to be higher than the boost pressure ).

That was before he put the smaller blower pulley on IIRC (wish I could find it, it was very informative).

Pertinent because it had the M-92 on it as well (somewhat different 'plumbing' though ).

Your cam overlap and exhaust backpressure have a big influence, though

Definitely.
Correct backpressure for blower: zero. If his BP exceeded his boost level he was using iron single exhaust with a bad muffler.

Any improvement to the head or exhaust will reduce boost and increase power. Boost means there's an obstruction.

There's a correction for overlap that can be plugged in to the formula.
1. Take nominal overlap (not @ .050").
2. Deduct 30° (Vizard's correction for ramps in a hot cam).
3. Multiply result by .01
4. Subtract from boost pressure (it's leakage).
Example: overlap is 70°, deduct 30 = 40°, × .01 = .4.

I prefer to move it around:
B = ((ratio × blower capacity × 2 × atmospheric pressure) ÷ engine displacement) - (atmospheric + O/L adjustment)

Example, using 230" + M90 @ 2 × engine speed, overlap is conservative at 50°.:
(2 × 90 × 2 × 14.7) ÷ 14.7 = 5,292.
Divide by 230 = 23.01.
Subtract (14.7 + .2) = 8.1 psi.

That's why I found it valuable and informative, he started with empirical measurements on one that was bone stock (IIRC) then re measured after each incremental change.

Yes, all math predictions are guesses only - not because the math is flawed, but because there's no way to tell internal blower leakage, belt slip, restrictions in the ports, charge temperature increase etc.