I'll dig some out...if you have an engineering common sense, you come to the solution which is right on the money...there isn't much to improve on the basic layout...just a minor variations...the pulleys are the biggest open field....I've started to modify original pulleys, for carby model skipping el.magnetic clutch and reversing the pulley, which gives me about 22.0 mm closer to the blower.I'm using heavy harmonic ballancer, where is easy to attach additional pulley...no welding and no need for balancing...
guys i used the original pulley and press fit and doweled on a bit of aluminium from which I then machined in a v belt groove pattern.
That way youy can have the original clutch and bring the belt closer to the SC: [img]https://www.postimage.org/Pq1iGWBA.jpg[/img]
PS Joel any picks on teh accelerator cable? Did you just splice it to the existing cable?
cb john love to see the pics . And a big question out to all ! Will anybody here "when things are all sorted out, reliability wise" be willing to share a plan to build this kit so all us aircooled lovers can do this ?
P.S another idea reading about the stress on the crank with "two pulleys" could u make a bracket on the lower part of the motor with a tentioned wheel that counter stresses the crank from inside of nicks alluminium fabd pulley? or is that getting out of control and too much?
Brendon, unless you got a blower real cheap i'd go turbo as they're everywhere, cheap and give the same results
SC12s are getting harder to find cos the toyota boys are running massive 175mm nevo pulleys and overboosting them
only difference between the setups is u have to make a header instead of belt drive
altho mine is off and retired now to make way for the new project it ran fine, it wasnt reliability issues as such more me being fussy and changing things all the time
yea i know what u mean i tried to find other ways to mount itthat looked neater but theres just no way to get it fit around everything else especially in a bug
i wanted to try one on the subi but its even more cramped for space
Ok guys an update is long over due.
I had the engine tuned and dynoed naturally aspirated. It was producing 70hp atw. Quite surprising I expected a bit more!
Pulled the engine out and decompressed it using copper shims between barrel and head. Got it down from 8.5:1 to 7.9:1.
Re assembled it and on Saturday took it down to the Vw performance centre for tuning. Hope to get it back before dotv ...
a little gem fo those blowing the t3 front pulley has 3v belt sections wish i HAD OF KNOWN THAT WHEN DOING MINE should just replace the pulley on the type 1
The engine produced 70h/p naturally aspirated at 8.6:1 compression and with twin webers.
I dropped the compression to 7.9:1 and installed the sc.
The boys at vw performance told me that the set up only produced 3psi of boost resulting in wait for it...90hp🙁
I was hoping for at least 6psi....have I made the crank pulley too small which means the sc is not turning quick enough?
To double the boost does that mean i have to spin it twice as fast? Are these things linear? If that's the case I have to nearly double the pulley size on the crank?? That doesn't make seem right....
Would reducing my combustion chamber size (upping my compression ratio) increase my boost?
The original 4agze motor which is a 1600cc (mine donks av1916cc) produces nearly 8psi driving a 145mm sized crank pulle ( mines 130mm same size as joels), so what has gone wrong?
Am I getting too much blow past having a mild cam? I was told it's a engle 120 but with only 70hp NA I'm thinking it was more likely a 110.
Else perhaps the clutch on the supercharger is slipping.... Any guys who have tried this set up if you could give me your boost numbers pulley sizes an engine size that would help....
That cam is a worry, I found the stock one in my 1600 performed perfectly with the blower but the Tighe 416C which is equivelent to a W110 in my 1776 really didnt play nice.
dont you just pull the vacuum hose off the valve to get more boost????😊
Joel wrote:That cam is a worry, I found the stock one in my 1600 performed perfectly with the blower but the Tighe 416C which is equivelent to a W110 in my 1776 really didnt play nice.
😂🤪😂🤪😂
car forums. where a lot of peoples good intentions end up taking a good old car off the road forever never ever to see the road again. 🥲
aintgotitmusthaveit wrote:( mines 130mm same size as joels), so what has gone wrong?....
if you drive the same supercharger like joel at the same ratio like joel...😉
you will get nearly the same hp like joel at the same rpm..thats it.
stock cams are good supercharger camshafts because of small overlap.
you have better heads and more displacement than joel so you will have less boost. boost is a messurement of restriction..you don't want boost, you want hp and torque.
all you need is more blower speed. if you have dynoed it with the 3psi...than you could nearly exactly give the blower the speed you want for the hp you want. in a very close range...lets say 1-3hp. thats because it is "just" a pump.
you could also limiting your engine to 50hp if you want just via slowing down the supercharger...
an easy first way to calc is. over the thumb for "dummies" but works in an easy way.
displacement of the supercharger in cubic feet x 0,85(ca. pump efficency inclued hp lost via pulley) x blowerspeed ratio x peak hp rpm (you have to feel where it is) / 1.5 = peak HP
Which 044's mate, cnc'd or un ported and valve sizes etc.
As said above, your engine is larger capacity than the blower was designed for so you will need to overdrive it more, maybe another 10% or so???
70 rwhp from a 1915 with 'basic' heads is about right.......main thing is the cam choice to get the blower working....there's a big difference from 110 to a 120.
Matt Berry Motorsports...air cooled advice, repairs and mods Ph 0408 704 662
OFF-ROAD,CIRCUIT,DRAG,STREET,ENDURANCE
After a night up reading everything i could find looks like if it's not a boost leak, that I simply aren't pumping hard enough; I'm not spinning the thing fast enough!
The sc is made by ogura. http://www.oguraclutch.co.jp/english/e_products/sc/sc_siyou.htm
They recommend a 11000rpm continuous for the sc12. I'm turning it at just over 1/2 that.
So yep I simply need to pump harder... So a new pulley(s) larger on the crank and or smaller on the sc.
I'm also upping my compression ratio back to 8.9:1 since I now dont expect more than 6psi boost. That will increase the effective compressionand hp. My buddies with sc12s on their mini is running they fine with 10psi boost and no intercooling.
I would avoid bumping up the comp if you can help it.
And leave the cam as it is.
My maths says you will need about a 1.5 drive ratio to acheive about 14psi.
This is very dependant on the temp rise through the blower and things like cam and head ports.
Without factoring in temp rise and the associated pressure increase,
a simple maths sum will tell you that your 1915 will consume 957.7cc per revolution at 100%,
so you can assume that 14.7 psi boost will want the blower to pump about 1.915 lt per rev.
With a 1.2 blower this will mean about 1.596 drive ratio.
I always use this basic maths as a start point, and usually the boost guage will show higher than this,
due to temp rise and restrictions that occur as the blower outsrips the engine's ability to consume air.
Remember thst "boost" is just the air that has not gone into the engine.
The power gain you have acheived is a pretty good gain.
1.2 drive ratio shoul have at least 8psi.
Do some porting if you are removing the heads again.
dangerous wrote:I would avoid bumping up the comp if you can help it.
And leave the cam as it is.
My maths says you will need about a 1.5 drive ratio to acheive about 14psi.
This is very dependant on the temp rise through the blower and things like cam and head ports.
Without factoring in temp rise and the associated pressure increase,
a simple maths sum will tell you that your 1915 will consume 957.7cc per revolution at 100%,
so you can assume that 14.7 psi boost will want the blower to pump about 1.915 lt per rev.
With a 1.2 blower this will mean about 1.596 drive ratio.
I always use this basic maths as a start point, and usually the boost guage will show higher than this,
due to temp rise and restrictions that occur as the blower outsrips the engine's ability to consume air....
half right, it also shows more on the gauge because you calc with 100%
1915/2 x 0,85 will be the start of boost at such an engine with good heads. now with his dynoed engine he can calculate everything he want in an exactly way. but over the thumb will also be close to that what he want.
as i startet calc my engines at the end i allways has the pressure i calculated. supercharging is really easy to calc in compare to turbo.
go for it. 1915cc with supercharger will be a supertorquer.
my 1192cc 30ps engine has close to 150nm from 1700-3000rpm.
Picked up the engine and decided to pull apart the manifolds and inspect for boost leaks... Guess what... A massive crack along one of my manifolds.... Looks like I sanded thru the weld.... Nob! So potentially more boost on the agenda😁
Welding up tomorrow. Engine is otherwise in as tuned.
Fitted a cheap Chinese alt, so have to ditch the regulator plus wire up the guel pumpr.
Fingers crossed ready for the dotv!
So after welding up the inlet manifold leaks, I decided we needed a but more boost too!
I checked with the OEM of the sc12 and it's rated to 11000rpm continuous, so I decided I could easily get away with a 7" crank pulley (with a 5" @ the sc) and a redline of 6000rpm.
The pulley looked wrong! It was huge! It's so big that it hit the new side winder exhaust so out with the torch and peening hammer. Lost interest and decided it was time for a drive, so fitted the old exhaust and started her up.
After a few hicups I took her for a drive yesterday for the first time.
Drove the car, Change into 2nd at 2500rpm, bury the foot and the rear lights up!! Awesome power but pinging under load so need to retard the timing or recurve. Makes the n/a 1916 feel like a slug!
aintgotitmusthaveit wrote:Drove the car, Change into 2nd at 2500rpm, bury the foot and the rear lights up!! Awesome power but pinging under load so need to retard the timing or recurve. Makes the n/a 1916 feel like a slug!
Ah that takes me back
I remember when I first put the blower on my 1776 doing the same thing.
Poor thing pinged it's tits off too at 8.8cr had to drop it back to 7.6
How much advance did you end up running?
I found 22* was a good happy medium
Thanks Joel.
It's been a bit messy. I had locked out a dizzy to 16 degrees for the old pulley
- something went wrong on that dizzy-don't know if the compufire gave up the ghost but tried an old dizzy and I found I could run it at 32 fine under the pissy boost it was producing
Obviously now with more boost that's not the case
I'm now going to lock this one out.
I gave dropped the compression to about 7.9:1.
Craig Torrens6 times Australian, 7 times State Hillclimb Class Champion
