V Groove pulley and M90

CobraSix

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Any reason not to use a V-groove pulley with an M90? Was just looking at my current set up and I have a spare groove available on my balancer so it got me thinking if it would just be easier to use a V-groove pulley for an M90 vice changing to a serpentine belt arrangement.
 
I've seen photos of v-groove driven SC's. An M90 draws about 45hp at 14000rpm (not engine rpm) and 7lbs of boost. However, at street rpm's at this boost range, it may not draw much more than about 25hp. A v-drive may hold it. If you have the option, try to route both belts over the SC.

For the same boost level, an M62 should only draw about 18hp. Both cases are assuming a 200 L6. If you get to this before I do, please post your findings.
 
I would definitely do a dedicated belt, and then the Alternator belt as well. Probably go with a double groove fan pulley as well. I'm still working some stuff out. I'm building a MPFI system first, but don't want to do anything I'll have to undo later for a SC. Particularly for the ford EDIS trigger wheel I plan to put on the balancer.

I haven't looked at the M62 yet since the M90 is widely available on the used market. Does the M62 have enough breath for a 200? Going to have to dig now.

edit:
When I looked at the performance map for the M62, to make 10 psi, the thing has to spin at nearly 12000rpm, which is at the top of the map. While usable, not much room for growth. However, the lower parasitic draw is nice. 6psi for the m62 isn't too bad.
 
I've been crunching these numbers and maps for a little while now...

There is a trade off between the M62 and the M90 for the 200. If ultimate power is the goal, the M90 is the way to go. However, the M62 provides more than ample daily driver boost with a little less heat and less power consumption. The M62 will support a 200 at streetable rpms up to about 10psi of boost before the M90 surpasses it. This should deliver up to about 300hp and 350ftlb (these estimates are based on dyno reports of published V8 builds from which yield average hp at about 70% of cfm and torque at 85%).

The M90 could push this a lot further, but then you start getting out of the peak adiabic zone, then hp consumption and heat increase drastically. When compared head to head, the M90 averages a few more degrees of added heat and consumes about 2-3 more hp. We're talking small differences until you look at the adiabic efficiencies; the M62 averages about 5% greater efficiency than the M90 at every point of reference until you approach 10psi of boost when the M62 starts to run out breath. By this point, you're running toe to toe with a mild 351w in the same car, keeping in mind your pushing less engine weight. :nod:

I really can't argue for a M90 on a 200 unless you want to boost more than 10psi or your building an all out race engine where you're going to see 5000+ rpm's. Streetwise, the M62 seems like the way to go. Most of my driving is between 2000 and 3000rpms : at 9psi, the M62 is averaging 65% efficiency, 155deg, pulling 13hp; whereas the M90 is at 60% eff, 158deg, and 15hp.
 
i thought we had a member here do a V-drive pulley with a roots type blower
as far as i can remember, they used two belts on it though
 
I think you could get by with a two groove pulley easily and have one made easily, the hard part is if you come right off the crank you will need a 8.75 crank pulley and a 3.8 pulley on the blower to get about 6-7 psi and a 3.4 pulley to pull about 9-10 psi, which will make all other components spin way faster than stock, water pump, power steering, alternator, etc, if you start getting into the really small pulleys on the blower is where the v belts won't flex as well around the pully as a serpentine, on the m90 if I remember correctly once you get down around a 2.9 pulley you have to machine the snout down on the m90 to get the pulley on. All figures based on m90. If you accomplish this, you will not regret having done it, the v8's can't touch you through the first two gears, but they catch me at the end.
 
One more thing is if you run much past 8.9-1, on pump gas you will not be able to run more than 7 psi on premium gas with about 4 degrees static and 25 degrees total timing, I'm at 7000 ft elevation, so your #'s could be lower and have a very good radiator, because boost raises compression and makes alot more heat, the trick with boost is keeping it cool, I try to run 160 dgrees all the time and it makes a huge difference especially with MPFI, because you don't have the cooling affect of fuel being drawn through a carb, big difference, I can always tell when I get a little warmer on engine temp.
 
I used 6psi and 10psi as my comparisons between the M62 and M90. Now I'm no expert on Superchargers, so see if my math is wrong:

To size the supercharger & pulley combination and to use the maps, I took a peak RPM of your engine and the peak VE, using the old standbys of 6000 RPM and 85% respectively. In reality, peak VE is going to be quite a bit higher than that, as the supercharger aids scavenging and can increase your VE to over 100%.

3.3 litre engine, spinning at 6000 RPM and with a VE of 85%, will draw in 8415 litres/minute [(3.3*6000*.85)/(2 revs per cycle)]. One cubic meter is 1000 litres, so the engine is drawing around 8.415 m^3/minute, or 505 m^3/hr. At 10 psi, the pressure ratio is 24.7/14.7, at sea level (which I'm close to), which equals 1.68:1. Looking at that map, means I'm in the 55-60% efficiency range, and without an intercooler my density ratio is about 1.33:1 using those efficiencies [(1.68-1)*55%]. That means the supercharger will be drawing in and compressing 505 x 1.33 = 672 m^3/hr of air.

To move 672 m^3/hr of air at 1.68:1 pressure ratio, I looked at the compressor maps.
M90 @10psi:
RPM: 8500
Eff: 60%

M90 @6psi:
RPM: 7500
Eff: 61%

M62@10psi:
RPM: 12000
Eff:59%

M62@6psi:
RPM: 10500
Eff: 60.5%

Now, I couldn't find good heat and drag numbers, but to me it seems better to spin as M90 at 8500RPM than a M62@12000. Shouldn't the M90 make less heat at 8500 and have less parasitic drag since it's spinning at 66% of the M62 for the same boost level?

Oh, does it count if I hijack my own threat?

I'm a ways off from deciding on superchargers. This winter is dedicated to making a MPFI manifold and getting that up and running. Then next winter will be a Aluminum head and SC winter.
 
CobraSix":av0o2a0c said:
Now, I couldn't find good heat and drag numbers, but to me it seems better to spin as M90 at 8500RPM than a M62@12000. Shouldn't the M90 make less heat at 8500 and have less parasitic drag since it's spinning at 66% of the M62 for the same boost level?

You're logic is sound, I followed the same path for a while. Something about the design of the 2 SC's allows the M62 to achieve a greater efficiency over the M90 up to around 9psi. And yes, you will be spinning the fool out of it. However, the M62 favors the higher rpm's over the M90. I found Temp and Drag charts at Magnuson Superchargers. They're the only aftermarket company for the Eaton roots SC's.

Something may be askew in your math, I suspect the volumetric efficiency assumption. Looking at your SC rpm's and outputs, your engine rpm's may be closer to 4000 to 4500 and the rpm spread doesn't quite compare head to head. One point to note, and this is where some theory and guestimation comes in : volumetric efficiency (85%, a sound assumption) really applies to how well an engine draws fuel and air naturally. Once you pressurize the intake tract, vacuum falls out of the equation as it is no longer drawing from atmospheric pressure, but some multiple of it. Certainly, the greater the natural VE, the better it'll breathe under pressure, but VE has a lessened effect against pressurized flow than when the intake tract is naturally fed. Sources I have read indicate that with mild and higher boost rates, you're safe assuming 100% VE. However, greater natural VE's translates to lesser boost measures given the drive ratio, meaning a 70% VE engine may yield 10psi, when a 90% engine may yield 9psi at the same drive ratio and flow rate. A SC is a high volume, low pressure air pump where pressure is a result of flow resistance. I know this is splitting hairs, but ultimately, which ever one moves the greater volume with the greater density for the application is the winner. Your goals are skirting right on the edge between the 2 SC's, where as mine favors the M62.

Broncitis":av0o2a0c said:
One more thing is if you run much past 8.9-1, on pump gas you will not be able to run more than 7 psi on premium gas with about 4 degrees static and 25 degrees total timing

This is a great point! And, can never be stressed enough. The greater your static compression ratio, the less you'll need to, or can, boost the engine before you'll need to take serious steps towards pre-detonation prevention. You can SC any engine, but how far depends on where you're starting from and what you're willing to do to help the situation. A higher static CR means less boost required to reach a goal, where as a lesser CR requires more. Neither is really "safer", because both lead to the same end result : higher combustion chamber pressure and temperature due to an increased volume of intake charge at the start of the compression stroke.
 
All I know from hands on for sure is when I was running 10 psi and race gas with the m90 is it had so much power I could not believe it and decided to go to around 6 psi since I just could not see how 200 cubes with that much power would last very long and also always having to run race gas was a drag and besides it was a bronco, it was pretty funny when the v8's couldn't figure it out, especially stop light to stop light, I would always tell them they don't want to know. Have fun, you can always have different programs for different boost with just the change of a pulley and downloading a different program you already have stored on a laptap, there's a big difference from 6 to 10 psi, I wish I didn't have to drive a long ways to dyno mine, I sure would like to know, conservatively I think it is 275 at 6 and 325 at 10.
 
my 2.3L volvo engine has a 15psi turbo on it for 250 HP. 210k miles and still purring like a kitten.

Socal, I read some places saying to use 100%VE. My method is basically a spin off of sizing the pulley ratio required to get a certain boost. but we seem to come to the same conclusion. 9-10psi of boost on a 200 is the gray area for the M62 vs M90. I'll likely go M90 just because of relatively cheap market availability.
 
I'm not trying to talk you out of the M90. Given where you're steering with you plans, The M90 would edge a slight advantage, and if you decide to push further, the M62 won't keep up. I picked up my M62 for $100 on eBay.

Broncitis":3r15vb9r said:
there's a big difference from 6 to 10 psi, I wish I didn't have to drive a long ways to dyno mine, I sure would like to know, conservatively I think it is 275 at 6 and 325 at 10.

Thanks for the info here. This reinforces my estimates. I bet 10 psi was fun! :mrgreen: :mrgreen: :mrgreen:
 
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