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Wed Feb 11, 2009 5:38 am

anybody know how much boost a judson push?
or MAG, pepco...

kris

Wed Feb 11, 2009 7:15 am

All are low pressure blowers...that is, less than 8psi.

The Judson according to manufacturers figures boosts up to 6psi but you'll find in practice you will be going some...in stock configuration...to make 5psi.

As most people make modifications to improve the breathing characteristics of the 36 & 40hp engines they will make even less as you're easing that "bottleneck" that backs up the intake and boost.

Wed Feb 11, 2009 10:10 am

thaks,..and is there anything about how much volume (ccm) they do per revolution?

Thu Feb 12, 2009 9:42 am

Perhaps John Moxon can ellaborate a little more on this subject ,but when using a Judson Boost gauge, whether Nos or aftermarket, and using a stock exhaust, you should get 5-7 reading on the boost gauge itself Using a bone stock exhaust set up. there was some concern awhile back that with the Abarth exhaust coming from steph in europe that when installed and used with the Judson supercharger that the Boost gauge would barely if at all move, when excellerating or decelerating. this is do to the volume of less back pressure I believe on the motor which creates less much less of a read if any on the Judson Boost Gauge 8)

Thu Feb 12, 2009 10:19 am

Eric Outland wrote: Perhaps John Moxon can ellaborate a little more on this subject ,but when using a Judson Boost gauge, whether Nos or aftermarket, and using a stock exhaust, you should get 5-7 reading on the boost gauge itself Using a bone stock exhaust set up. there was some concern awhile back that with the Abarth exhaust coming from steph in europe that when installed and used with the Judson supercharger that the Boost gauge would barely if at all move, when excellerating or decelerating. this is do to the volume of less back pressure I believe on the motor which creates less much less of a read if any on the Judson Boost Gauge 8)

I ran my stock 36hp engine with a Judson and one of Stephs 4 tip exhausts and our repro Judson Gauge...just the very configuration you mention Eric.

My findings were that it ran at just a tad over 4psi with my foot hard to the floor. Maybe a little blow-by from the fact it blew a little oil from the crank pulley but otherwise the engine was in good shape.

There are a number of variations from stock that will affect boost, like cam spec, rockers, exhaust, timing, anything that will reduce that characteristic 36hp breathing bottleneck.

Of course the Judson has to be in good shape too...any wear to rotor, vanes and chamber will all potentially reduce the amount of boost you can expect.

So does the reduction in boost reduce the effectiveness of the Judson? Not for me it didn't...the end result I suspect is very much the same but it does begger the question; Are extensive reworkings of the stock 36hp engine worth the expenditure when coupled with a supercharger?

Judsons, MAGs, Pepcos, Shorrocks were all designed to be added to an engine in stock configuration, that's how I used mine apart from the exhaust but I didn't chase that missing 1 to 2psi...there lies madness. :lol:

Thu Feb 12, 2009 11:12 am

i ask because i have build a supercharger kit. amr300 supercharger and stock intake and first heads with stock valves, but i work on heads with bigger valves and bigger channels and also a bigger intake (1500 or selfmade) and will use pci 34 carb.
i wont know how much a stock engine can hold and how much volume the judson and co push to check what is possible with this system and this supercharger...theoretically the supercharger can push any engine up to 80 din PS so my goal is 60-70PS at the end.
this little monster ;) haha spins 3:1 so it produce 900ccm per crank rotation. what do you think that will in boost an a 1192ccm 36HP engine?

Thu Feb 12, 2009 12:00 pm

I have worked with superchargers on large V8s with free flowing open exhaust, large heads and cams and weather or not the gauge shows movement from being backed up the supercharger still moves a volume of air through the engine as it spins. This increased volume of air/fuel flow is still making power.

Thu Feb 12, 2009 2:01 pm

splitvws wrote: I have worked with superchargers on large V8s with free flowing open exhaust, large heads and cams and weather or not the gauge shows movement from being backed up the supercharger still moves a volume of air through the engine as it spins. This increased volume of air/fuel flow is still making power.

...but big power comes from big pressure.

Thu Feb 12, 2009 3:38 pm

Yes the more perssure the better. I have a smaller top pulley and just spin the blower faster to make up the differnce for free flowing heads and exhaust.

Thu Feb 12, 2009 4:05 pm

what kind of blower?

Thu Feb 12, 2009 4:24 pm

injected 540 with 14-71 in a drag boat. But Im in the middle of a 36hp biuld with ported okrasa heads larger valves recut cam and a nice balanced lower end. I will be running a Pepco blower thats alittle over driven so we will see what kind of pressure Ill get. The Blower and ratio you show in your pic looks like a cool project can't wait to see more on that biuld

Fri Feb 13, 2009 12:58 am

wow pepco...beautiful vintage blower...i trimmed my amr300 to looks older.after testing i will sandblast the hole system to looks bedder.
that will become my daily driver maybe with water injektion.15000 rpm is the max for the blower so 5000 rpm of my engine will be the max. maybe i have to lower the blower pulley 1-2 teeth depends on what my cam say to the blower(performance cam from mr. okrasa for judson).

i also have a arm500 that can go up to 130 DIN PS also very rare but don't looks so good an a 36HP engine ;)
so i build it on my second drive.also a 1192ccm but a 40HP engine

Mon Mar 23, 2009 2:12 am

not a big update but a little

supercharger for the 36hp engine is clean and ready to take a carb to blow my 36hp engine. at the moment i wait for the crankshaft :(
the intake has a pipe for boostgauge but no watherinjektion jet because first i will see how much boost it have.

the superchargerkit for the bastard engine is ready too.
damn i have to wait only for engine parts...for this engine i wait since 5.01.09 ...grrrr

for shure this is no vintage speed...this bastard has 1300 35,5/32 heads,
forged pistons 77mm, crank+flyweel+clutch+pulley is ballanced, tsc-10 cam, intercooler,free programmable injektion and ignition...
but i think the blower is a interesting part for vintage speed

Thu Mar 26, 2009 11:42 pm

Hi Kris, just repeating for the others my reply to your PM the AMR300 wasnt fitted to my bug it was on a beetle i looked at that was for sale

it was a 68 semiautomatic 1500 with a 2" SU carburettor and a subaru AMR300 running unknown boost
when i saw it again a few months ago the blower had been removed though

the blower on my beetle is a much larger one from a toyota
it displaces 1200cc compared to the AMR300s 300cc

it handles 12psi factory and the toyota guys have run them upto 16psi
but i have had mine no higher than 10psi

Fri Mar 27, 2009 3:48 pm

thanks alot buggin_74 that will help me and i hope i can see the blower run during the next month.

Fri Apr 10, 2009 2:43 pm

just a test mounting in my rusty car just to see how high the carburetor will be. i just have to change the throttle lever ant the carb will fit and have space for a filter with issued bonnet.
i hope to get more than 60 hp with this little screamer that can run 15000 RPM (pepco can run 8000RPM)

most of the engine is new p/c, heads, cam (mr.okrasa preA)
hope that it spins up to 5000 rpm at max. hp because the supercharger ratio is 3:1 at the moment.

cooling, pulleys and manifold needs a bit of love and color;)

tomorrow i will fit exhaust and start with mounting waterinjektion into the car.
i hope the noise of the blower isn't to strange.

Tue Apr 28, 2009 4:19 pm

me again
next step engine runs but without supercharger....first the engine have to run in.
facts:
heads
-inlet valves polischt an modified 49g now
-outlet 2metall valves from a audi rs2 28mm 50 g polisched and modified
-chamber polished outlet port polished too. inlet just deburred.
-rocker modified from 86g to 75g

preA grinded cam
21mm oil pump
rods 400g
compression ratio 6,8:1

watherinjection installed.
stock distributor but with saab9000 turbo pressure tin (early+late adjustment)...ready for boost ;) ;) ;)
supercharger comes during the next days.

http://www.youtube.com/watch?v=LDHBtPSN1Ec

Thu Apr 30, 2009 4:09 pm

its done....
i have a video of the 2. start but youtube will not load it. maybe later.
wow totally different engine.
and it push up to 13 psi!!!...at the moment he is way much to lean....
i run it once but not to high because engine is totally new and just 100 km now.feels like somewhere is a second engine in this car.

Fri May 01, 2009 9:40 am

here is the video from yesterday.
engine needs more job on the carb its a 34pci from an old bmw700 single carb engine.

i had some bad problems with the sealant..because the fuel washed it away.
wrong sealant...now its fixed and it pushes like hell.
but its still to lean ...specially at idle...at idle i have 7-8psi negative boost
and biggest is now between 12-13 at hte road.

http://www.youtube.com/watch?v=qWw8AIh__Sg&feature=channel_page

Fri May 01, 2009 9:50 am

grueni That is a sweet vintage Pusher!! Would like to see the Boost pressure on the Road! Also Did you rebuild the Supercharger or just put it on and fired it Up?? Cheers Eric 8)