Technical So here is a question for you induction gurus or even

Amateurs for that matter.

Suppose you have an old Potvin blower setup. Like this for example:


And you wanted to run it blow though say using a pair of Enderle Barn doors:



Or maybe a 4 port hilborn:



Could it be done? Would you have to do anything to the injectors for blow through?

 

The fuel injectors should not be bothered by the boost. Carbs have to have a rising rate fuel regulator to up the fuel pressure because the carb bowl vents are in the pressure stream. Tuning mechanical injectors for blow thru I have no clue. Blow thru carbs are not too hard with a wide band.

 

Check out these threads, there are some good photos:
http://www.jalopyjournal.com/forum/threads/potvin-blower-setups-and-manifolds.463034/
http://www.jalopyjournal.com/forum/...r-setups-and-the-engines-that-love-em.623231/

 

Hilborn sells nozzles that do not have the screened holes for aeration that the regular nozzles have. For blow thru use. They also have a pressure regulated pill for the bypass that will richen up the mixture as the boost increases.. Other then needing some fuel through the blower to lubricate and cool the rotors and I guess your good to go.

 

I don't get the question. The beautiful example already has a barn door style injector on the suction side. Why would you take the intake charge (thru an injector) on the blower inlet and exhaust it thru another injector? Is this a blonde joke?

 

Nope! Can't be done! Send me all that junk!

 

Have you considered electronic fuel injection? Could be adapted to the original manifold and blower.

 

I could imagine throttle response being better with the fuel nozzles on top instead of 3 feet away. Starting should be lots better also. On most of the injected motors I have had, I put primer nozzles on top of the intake to spray fuel into the port and run on until the injector pump catches. Some of them worked and some not so much.

 

I don't know what problems you would run into, but I don't think they would be insurmountable. EFI would certainly be easier/ faster/ infinitely tuneable, but if you can get it to run in a wide enough band mechanically, that would be incredibly cool. I think you need to run some fuel through the blower as lubricant/ cooling of the rotors, but the length of the runners to the top of your engine would likely screw up the atomization anyway.
What do you envision running it on/ in?
I love the idea of a track nose A roadster baby hemi Potvin....


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Fuel running through the blower to lubricate is only an issue if your rotors are stripped. If they are not, nothing in the blower is touching. The GMC blowers off the diesels were run dry. Cooling the charge and aiding in sealing the rotors for more boost is a good reason to run fuel through the blower. Top fuelers run injectors under the hat, in the manifold and in the head to feed the engine enough nitro. Being constant flow and high pressure it does not matter where the injectors are placed.

 

The first photo of the front mounted blower and pipes looks so sharp......During WW2 the Allison V-12 aircraft engine used a set up like that with mechanical and or turbo superchargers. Under high load the air fuel ratio became uneven and the leaner cylinder detonated causing engine damage.. Obviously an aircraft engine running at high load with 15 psi boost for an hour is more severe than drag racing or LSR.....but something to think about

 

Is this on gas, alky, nitro? It could be done but on gas I bet getting the idle even would be a PITA. Port nozzles a must. You ok Beaner? And wait till you slam those butterflys shut on that gas and air mix at about 8 grand against that boost. LOL.

 

x2 . . . the problem with blow-thru setups and no blow-off valve between the butterfly and the blower is what happens when you let off the throttle.

 

bingo! I think you gotta lube rotors surfaces with something more than air, leave it a draw through set up with primers up top or something like that. awesome set up, what ya gonna do with it?

 

LOL I ain't got the junk yet.

What got me thinkin' about it was the fact that a sedan that I am working on, as the build is currently set, would have room for a Potvin setup or close enough that a little fudging of the pieces would be possible to make it work.. Then I got to wondering if blowing through the injectors would work.

If you are using a GMC blower you are already using a dry blower so while lubing the rotors is a good idea it should not be entirely necessary, and it would be a simple work around if it became necessary.

A blowdown valve would not be a problem either I would think that you could run something along the lines of a waste gate. Again it would take a little engineering to make it work. You would need to use throttle position to activate it or something along those lines.

Anyway my brain started making these questions and my wallet started saying that experimenting was probably not within the budget so the next best thing to experimenting is brain storming with the people I now who could either come up with good questions or good solutions.

Another thought I had was to throw nozzels in the runners close to the port and just use your injector body out on the blower end as throttle bodies. I have never run a Potvin setup but I have played a bit with turbo setups and I know that at least with a turbo a draw though suffers from turbo lag. Part of that is waiting for the turbo to spool but the blow through setups don't have the problem nearly as much. I have also discovered that the closer to the manifold you get the turbo on a draw though the less lag you have. For example when we out the old 'vair turbos on our old Harleys in the '70s we suffered almost no turbo lag at all. The turbo was bolted directly to the intake.

Anyway I guess my brain started wondering that if your fuel delivery system was as far from the valve as it is on a potvin setup would you also suffer lag and if you did would then a blow through setup would help that.

 

I don't know why nozzles in the runners directed into the ports wouldn't work with the throttle at the blower. If you were pumping dry air, a simple blow off valve should work but i am not sure you would need one with a crank driven blower. Maybe just back off on the springs already on the pop off. I went around and around with Buddy Walker (Flatcad) on here about dry GMC blowers. I know a guy who tried it. Killed the blower in the first quarter. I finally got Buddy to call the blower manufacturer. So I would say to you, do the same. I know they pump dry air in buses and such. They don't like it at all running as hot rod parts. Maybe it's an RPM thing. Here i am tapping the throttle for my Dodge Bros. injector. As told to by Don Enqurie I am putting the nozzles as far from the valve as I can with still a downhill shot. Don Ferguson has done extensive dyno time with his own castings. I understand him to say bigger butterflys farther from the valve worked best.

 

Just leave it the "traditional" pull threw and make the injector hats/tubes go out the hood sides. It'll look like a shorty header with the hood shut

 

Maybe the RPM is the killer, pumping volume creates heat. a simple water/alcohol spray would cure it I would think. And destroying rotors was something that my thought process completely missed. I wonder how much it would take to survive.

Rich one of the reasons to get the butterfly way from the valve is that you get your butterflys farther from the heat of the engine. Remember the old Pete Jackson stack injectors? Part of the reason he made his stacks long with the butteflys way up the stack was to get them away from the heat and avoid all the initial adjustment as the motor warmed. That may be just a by product of moving them away from the valve but it is certainly the cream on the top of the milk jug.

Now I have new things to think about while I am not sleeping.

Or plumb it and get your air intake down low behind the axle. Probably wouldn't work well on the salt.

 

Beaner; You may have to go back and read my amended post. Moving the butterflys does seem to be the idea. Again, look at these late Hilborns I pictured. There must be a point of diminishing returns though. But down nozzles point right at the head of the valve. On my Nissan injector (the yellow one)I found the down nozzles worked good with Alcohol but were junk on gas. The long tube injector had the nozzles and throttles just behind the grill on my flathead '32 Plymouth. Worked great.

 

There is a reason the Potvin setups are not used anymore and one of them is HEAT in the intake runner tubes. Down nozzles are to equalize cyl temps and add volume to the system. Now if you had an intercooler....., And a Procharger with a butterfly at the opening of it....... But alas we are getting off base here. LOL

 

Well with carbs on alcohol you use down legs (squirters) but they don't work well with gas so that makes sense. Some of the engines that we use the way that the head is designed we could actually out the nozzle right in the port if we wanted to. I think that too close to the valve would end up being a problem although I cant think of why. Maybe it becomes a runner length issue as all you are pulling ( pushing) though the runner is air and not air fuel mix?

One thing about a potvin setup is that an intercooler actually becomes optional. Not so much on a standard roots blower setup. Although if you wished to become high tech that can be done also. I have worked with a hat injection setup that had a refrigerated cooler between the hat and the blower. I am not sure that you could call it an intercooler as you are cooling the incoming charge and not the boosted air.

I think another reason that potvin setups lost out was that they were one to one pretty much always. You didn't have the versatility in drive options as in under or overdriven blower.

 

I know they (BDS)? makes an intercooler that goes under the blower.

 

Buddy Walker has an intercooler under his 6:71. New EFI cars have the nozzle in the combustion chamber. Timed.

 

So your mainly talking gasoline here? Lippy

 

Rich you snuck in on me. LOL

 

Yea direct injection is the new deal, no one has figured out how to soup it yet but someone will. I doubt that it will be me.

@lippy I know that BDS markets a cooler, I don't know if it is refrigerated or water cooled. I wasn't aware that it went under the blower but I don't know why it couldn't.

Well when my mind was wandering I was actually thinking if something that could change from gas to fuel when the mood arose. But nozzle placement was not something I had considered. of course originally I hadn't thought past just using an existing injector and blowing through it like a carb.

I guess if you really wanted to cheap out you could use a couple of these. I still see these used reasonable.


If you went blow through you could use one foe each bank otherwise you could use it for a throttle body and put your nozzles in the runners.

 

The blower shop makes an intercooler, under the blower for a marine application, uses lake water or salt water to cool, now lets put that setup of yours in a bass boat. lol.

 

Screw bass boat if we are going to fudge lets make good fudge, 12 foot aluminum john boat or nuthin.

With the potvin setup you could go air to air in the intercooler.

I think that we don't see the potvin setup because there are a lot of setups that are just more efficient but you would think that we would see it more often being traditionalists. I don't even see parts to build one for sale ever.

The picture that popped into my head is a simple sedan no major slicing and dicing with the engine stuffed back into the cowl enough to get the blower behind the cross member. On gas which is a little harder to tune but not that bad, if you built your engine right you could actually build it as a running driving car.

Anyway once the picture was there all the questions started me thinking. And as luck would have it I happen to know a couple of fellas that can answer questions.

 

Since we are getting nuts here lets make an air boat with a propellor!!!! Gator Getter!!!

 

Gotta go weedeat, later gator. Lippy