Centrifugal supercharger question

[plovett]

I don't know if I agree with that.  The supercharger speed is determined by the pulley ratios and the drive ratios in the supercharger itself.   So a supercharger could be turning any number of speeds when the engine is at 5000 rpm.   And many engines turning 7000+ rpm use centrifugal blowers.   The max impellor rpm can be very high.

http://www.procharger.com/models.shtml

JMO,

paulie

[jayb]

Centrifugal superchargers run at speeds much higher than 5000 RPM, more like 30,000 - 40,000 RPM.  Roots superchargers run much slower, if I recall correctly...

[plovett]

Here's a more doable idea IMO, Ross.  Convert your 489 to run on E85.  That ought to work with your compression ratio and a blower.  I don't know exactly how much boost you could run.  I think it might work with moderate levels like 7-9 psi. 

paulie

[My427stang]

I could Paulie, but with me moving around the country pretty regularly, I am not sure of availability everywhere

Here in the midwest there are pumps everywhere, but I dont remember it being that accessible in MD or VA and my next move is likely DC

I think when the truck is done I'll just build what needs to be built, maybe sell off the 489 to minimize shit build up in the garage, or like I said earlier, put it in the truck and sell the 445.

We'll see how it evolves, definitely doing something though, itching to take it to the next level

[plovett]

Just throwing out my opinion here.  I don't think your 489 is good combo for a truck.  Mostly because of the compression and cam.   The cam is fairly small for a motor that big and the compression is fairly high for a truck.   I say the cam is fairly small, but in a truck I think I'd want something even smaller.   But then that would exacerbate the high compression.  So you're kind of stuck in my opinion.   It'd be nice truck combo if you could put some good big chamber heads on your short block.   I'm not sure what heads those would be though.   That or keep the current heads and "partial-rebuild" the bottom end with different pistons and a smaller cam.

All that said, I'm sure your current 489 would still work in the truck mostly just because it's a big motor.  It'd still go like stink and I know you're smart enough not to floor it in top gear at 20 mph, going uphill, with a load in the back, in July, with 87 octane in it.

JMO,

paulie

[My427stang]

The truck is only 4100 lbs, it'd be absolutely fine, it's a tight quench motor, 8.33 DCR and too many hours of head and piston surface work that will run on any swill out there and is perfectly happy at 1600 rpm chugging along.

Basically, consider it a Galaxie with a 4 speed and a 286 adv duration cam and 10.7:1 in a truck's clothing

Keep in mind, I drive a Superduty and it does any of the work, the truck is a hot rod and has been used that way since the 90s, to include a stretch with dual nitrous bottles bolted to the roll bar and a Predator under the hood...  Driving hard is not a new concept for this old beast

I actually consider the current 445 very undercammed, which I have been teased about a bit by my local buddies

[plovett]

I guess I was thinking it was truck like a "truck".  If it's a hotrod then put the small cammed 489 in there.  What's  the deal with putting small cam's in everything you build???

paulie

[My427stang]

Thats funny, but I do have an explanation followed by a silly reason on the truck

1 - I spend far more on heads, intake and headers than on anything else.  I think power is made in those areas and the right cam complements those.  A big cam with crappy heads is just a noise maker

2 - After I plan that, I cam to the intended use based on those parts and some gut feeling, and in my case, the Mustang needed to be able to handle a 2.36 final drive happily, ended up I geared it lower and went with a 2.63 final.  So yes its a bit small, but with all the head work it'll pull hard to 6500 shift point, but likes 5th gear at 40 mph

Small is of course relative too, the cam card reads 242/248 @ .050, .595 lift and it's designed to run at .026 lash, I run it at .014, so its a little more than the cam card would indicate

Its not really in that order, it all happens at once, but I really like a deep breathing head over a lumpy cam if given the choice.  Admittedly, the EFI dropped idle by 200 rpm and increased torque significantly, so I probably could handle a little more cam now.

Now for the truck...all that "proper planning"  is blown out the window

1 - I didnt want to have to break in a new cam
2 - I didn't want to spend money on adjustable valvetrain, all I did was add end stands
3 - The 270H was in it already and had very low miles
4 - Rocking it back to 110 ICL got DCR around to 8.2 and theoretically kicked the rpm range a bit higher
5 - Ported the hell out of the heads and intake to hopefully keep the baby cam's hp peak near 5200

So we'll see how this backwards experiment goes, to be honest, I think the truck would love a 282S on a 105 ICL, but it's together and sounds real nice. We'll see if it hits a wall at 4500 LOL

[plovett]

Fair enough.  I especially agree on your point regarding heads, intake, and exhaust first.  You can still have a lumpy cam after that if it makes sense.   It's not like you have to choose one or the other, but not both.  Still,  those things you mentioned should come first.   What a hotrod is to me is not exactly what it is to you and I shouldn't project my proclivities onto you.  There.   

So,  what is the general plan for the 'Stang then?   A 500+ inch FE with BT heads, twin throttle bodies,  FI, cammed for a wide rpm range with killer low rpm power?

paulie

[My427stang]

I think we probably have a little different ideas, but don't underestimate a 489 inch FE with heads that flow in the 320s, 3 inch exhaust, 10.7:1, a ported Victor, a 1200 cfm throttle body and 4.11s.  It's no Lexus

Remember, I drove this car up and down the west coast with 4.10s, all insulation removed with a 433, 250@.050 Isky, a Portosonic, Flowmasters, no a/c and a 4 speed, those days are long over for me!

Next one will probably be a 505 with a wide LSA hyd roller and a blower, max rpm 6500-ish??.  Still working it out, I have a bit of turbo time, but never built a blower motor so need to do a lot more research.  Regardless of the build, it needs to be able to happily do a 5 or 10 hour drive and idle in any traffic, regardless of the build.

To be honest, my driving style might like a turbo better, but I am not sure the car has the room for the piping I'd need for that big of a motor and I hate to add heat under the hood

Jay, to get back on the topic though, do you shoot for a different DCR number or consider a max overlap number when you run a blower?  I would think that overlap is less important at midrange and could waste boost on top.  I also assume normal DCR numbers sort of go out the window

[plovett]

Well, that ought to do the trick.   I really want to use a centrifugal blower myself someday.   I'm keeping one of my 391 cranks with the big snout (and have a 391 timing cover)  in case that proves helpful if I ever run big boost.

Any ideas on the heads?   For years people used to say if you put a blower on it the heads don't matter to much, 'cause the blower will force the air through there regardless.   I've always had the opposite belief.   I think if you're flowing more air the head is becoming a bigger restriction, not a lesser one.    The crappier head may produce bigger boost numbers and less power.   

Intercooled?   I like the idea of air/air intercoolers though you have to find a place for them.   In front of the radiator, or possibly in one of the wheel wells?   

Victor intake?

Cogged drive belts are nice for a blower, IMO. 

paulie

[My427stang]

Paulie, I'll probably run the heads I have now.  I agree that eventually they become a restriction, even with a blower, but I won't get any serious gains from what I have without ridiculous money.  With the boost and RPM I plan to run, I don't think I need a whole lot more

As far as an intercooler, I do plan to run one

[jayb]

When I was doing my blower engine I had the good fortune to stumble across a Ford engineer with a lot of experience in that area.  His official title was "Senior R&D Engineer, Boosted Engine Projects" or something like that.  At the time he was working on a race program with one of the 10.5 Mustang classes, and had some contacts at Vortech that helped me out quite a bit.  Anyway, what I learned from him were a few general rules, such as:

- Anything you do to the heads, intake, exhaust or cam that will help a naturally aspirated engine will also help a boosted engine.  The old saw about not needing to do headwork because of the blower is not correct.  Headwork and other induction system work, including a big cam, will help a blower motor just like it helps a naturally aspirated engine.

- Shoot for the widest lobe separation angle that you can, within the limits of the cam specs that you want to use.  I used 116 for my supercharged engine, and the cams for my SOHC turbo motor are also 116.

- You may actually want less exhaust duration on the cam with a turbo motor, rather than more.  This is counterintuitive, but has something to do with the way the exhaust pulse helps spool the turbo.  My turbo SOHC cams are the same cams as the ones in my 585" SOHC, but with about 6 degrees less exhaust duration.  This doesn't necessarily apply to a supercharged motor, though.

Also, I ignored DCR on my blower motors, because it was so low due to the static compression ratio and big cams.  I'm not sure that the same rationale applies to a blower motor anyway; you are packing more air molecules into the cylinder with a blower, so from a fairly simplistic perspective DCR would go up with boost.  I don't know how to calculate that; my Ford engineer friend told me that the formulas for calculating actual compression ratio from static compression ratio and boost pressure are not really accurate.  (At 15 psi of boost, you are packing twice as many air molecules into the cylinder.  This is not the same as doubling the static compression ratio.)

On other thing that I found very interesting on my supercharged engine was that it made more power with the Performer RPM intake than it did with the Victor.  My motor was carbed, and this may have had something to do with it, but I'm not really sure.  You could really see this in the exhaust temps on the dyno; the Performer RPM had exhaust temps that all wanted to converge at higher engine speeds, while the Victor's exhaust temps diverged.  I assume that this was due to better fuel distribution in the Performer RPM intake than the Victor.  If you went with EFI, I also assume that this would no longer be an issue, and in fact I have a Victor that I got from Barry R that is heavily worked over, and was planning on going to an EFI setup on the supercharged engine at some point...

[plovett]

I agree that eventually they become a restriction, even with a blower,

I'm going to reiterate this.  I'm not trying to hassle you or anything.   It's just I don't think I'm getting my point across well.  You said the heads may become a restriction even with a blower.   I think a blown motor needs more cylinder head to work well.   That's what I meant when I mentioned the old school thinking about blowers and cylinder heads in my previous post.  Is a head that is right for a naturally aspirated 489 also right for a blown 505?   Sure it'll make a whole lot of power with the blower, but you're still trying to stuff a lot more air through the same space in the same time.  You're actually working the port harder.   The harder you work the port the less power you'll make (compared to a bigger better flowing head) and the more you'll heat the charge (you'll have a higher boost number, too).   Sure the intercooler will remove some of that heat again, but then you're really working at it the wrong way, IMO. 

I agree with Jay's point that anything that helps the naturally aspirated motor make power will also help the blown motor.  I would go a step further.   I think the gains are proportional, maybe not exactly directly proportional, but proportional nonetheless.  Say if you gain 50hp with a head swap on a naturally aspirated motor, you might 75 hp or more if you did the same head swap on a blown motor.

For sure don't take my word for it.  Ask the experts.  I'd look at the heads before I bought that big cube short block and the blower to put on it.

JMO,

paulie

[My427stang]

I got it Paulie, but I am not sure I agree completely, but I certainly do in spirit

To oversimplify, you need enough head flow to not back up the port with the volume of air going through, no more.

What a head flows under vacuum does not mean it will flow too little with pressure, and it doesn't mean that it still wont be very effective at different levels of boost even if it falls off at high levels

I agree there will be more gains with a larger port at higher boost levels, but the principals still apply.  A big lazy port at 1500 rpm where there is no boost, is still a big lazy port at 1500 rpm

But I do understand your point and I agree, my words would be that "the more air you push through a port by any means makes port design even more critical to get the most you can out of the engine"