924Board.org

-nick · Joined: 16 Nov 2002 Posts: 2699 Location: Cambridge, MA

Any ideas? As far as I can tell, this is going to have to be welded to the end of the crank pulley- but it also needs to be balanced for x,xxx rpm. Sort of a tricky request for a welder. How have you folks mounted them up?

nick

Alex Roy · Posted: Tue Jan 25, 2005 9:03 am Post subject:

I just finished mounting mine up this past weekend.

I turned a new crank pully on my lathe out of aluminum and made a hub on the center of the pully for the center of the trigger wheel, then just put bolt holes on the trigger wheel on the same diameter as the pully bolts and got long bolts that bolt it all to the crank. I can take some pictures at some point and post them.

-nick · Joined: 16 Nov 2002 Posts: 2699 Location: Cambridge, MA

pics would be great! This sounds like something a machinist is going to love me for $$$.

nick

numbbers · Posted: Tue Jan 25, 2005 11:14 am Post subject:

I need a crank pulley with one extra v-belt slot, to run a small supercharger that I want to use with the turbo, to eliminate turbo lag. Any ideas on how to go about it.
_________________
1980 924 Turbo

Peter_in_AU · Joined: 29 Jul 2001 Posts: 2743 Location: Sydney, Australia

What type of trigger wheel are you using Nick, one of those 36 tooth Ford ones? What diameter is it?
_________________
1979 924 (Gone to a better place)
1974 Lotus 7 S4 "Big Valve" Twin-cam (waiting)
1982 924 (As featured on Wikipedia)

Learn to love your multimeter and may the search be with you

macBdog · Posted: Tue Jan 25, 2005 12:08 pm Post subject:

Total n00b question, is the crank trigger wheel the same as a crank position sensor for EFI? Is that what you guys are doing?
_________________
1979 931 with a 350 chev
1973 911E with EFI

Peter_in_AU · Joined: 29 Jul 2001 Posts: 2743 Location: Sydney, Australia

Sort of. The trigger wheel is what the crank position sensor is aimed at. The wheel is bolted to the crankshaft or something turning at crankshaft speed and the sensor detects the teeth on a toothy wheel or the magnets on a hall-effect wheel or the holes in a light-triggered wheel and sends the pulses back to the EFI or ignition controller.
_________________
1979 924 (Gone to a better place)
1974 Lotus 7 S4 "Big Valve" Twin-cam (waiting)
1982 924 (As featured on Wikipedia)

Learn to love your multimeter and may the search be with you

-nick · Joined: 16 Nov 2002 Posts: 2699 Location: Cambridge, MA

yep, they are used only with ignition system timing not EFI (as far as I know?).

Here are the specs on the wheel I'm using (size in mm)-
http://home.earthlink.net/imagelib/sitebuilder/misc/show_image.html?linkedwidth=560&linkpath=http://home.earthlink.net/~beanbooger/sitebuildercontent/sitebuilderpictures/36-1ring.jpg&target=tlx_new&title=Click%20here%20for%20a%20drawing%20of%20the%20toothed%20ring

nick

Alex Roy · Posted: Wed Jan 26, 2005 5:49 am Post subject:

I would say I could make one for you for a minimal cost....but I've only had my lathe since Christmas, and I didn't have a heck of a lot of experience before that. You might want a pro to do it for you.

The other thing is that I can only turn up to 4" diameter material, so it will also be an underdrive pully. Mine required a slightly smaller water pump pully so it wouldn't be under driven too much. It ran hot until I turned a smaller water pump pully. It also requires a smaller belt (40").

-nick · Joined: 16 Nov 2002 Posts: 2699 Location: Cambridge, MA

Not much of an update, but here are some pics of what I'm dealing with. I'm going to try to stop over to a machine shop sometime this week to see what can done.

-nick

Some shots of the whole (almost) project- anyone want to help wire all this up?

simsport · Joined: 06 Nov 2002 Posts: 573 Location: UK Warrington

Nick
I have tried both a solid machined billet (which works well) and a weld-on trigger wheel from a UK GM model (Astra) .
The welded wheel needs some care as the tin pulley wheel 'flexes' a bit in use. I know it might not look like it might but it does.

We found that a brazed timing wheel would crack the welds after a small number of miles due we feel to this 'flex'.

I do have a wheel somewhere I used on a N/A before I hade the machined wheel made.

I'll send you photos

Cheers
Simon
_________________
Blown is always best!

Joes924Racer · Posted: Tue Feb 08, 2005 4:41 am Post subject:

AND THERE YOU HAVE IT FOLKS THE WELDED WHEEL WONT HOLD UP..
wish I still had access to a lathe back in the day thated be a nice project for me.. how about having it machined so you could bolt it to the wheel
like an adjustable cam sprocket except for the crank.
_________________
1979 porsche 924 Na
1980 porsche Turbo 931GT Replica
Have u ever driven a turbo.

Peter_in_AU · Joined: 29 Jul 2001 Posts: 2743 Location: Sydney, Australia

Simon, would you please send me copies of those photos too.

I need to find or build a trigger wheel and sensor that's compatable with a GM/Delco computer.
_________________
1979 924 (Gone to a better place)
1974 Lotus 7 S4 "Big Valve" Twin-cam (waiting)
1982 924 (As featured on Wikipedia)

Learn to love your multimeter and may the search be with you

Alex Roy · Posted: Wed Feb 09, 2005 3:45 am Post subject:

I would think the best thing to do would be to cut a new pully that has a hub within a couple thou. of the inside of that ring, then make a round plate that will clamp down on the ring when the bolts are tightened.

simsport · Joined: 06 Nov 2002 Posts: 573 Location: UK Warrington

Correction!!!

My pulley is welded after all (it was a long time ago we did this honest!) in that I have solid machined item which is the main pulley and has the supercharger and alternator drives on it. However the Ig/Fuel pickup wheel is welded to the front.
I am fairly sure it is Tig wleded and that it worked well before.
Certainly it shows no signs of coming off after several years now.

I also have found my original wheel from the car when it was N/A but also had full ig/fuel management. This pulley has a tig welded wheel on it. It still shows the Braze that failed but then has proper Tig welds to replace them and has evidence of being balanced. Again I cant remember having done it, perhaps the machine shop did it with the crank etc.

Anyway, I have a few pics of the old pulley but cant get my IE5 to allow me to post from the web page. Peter, could you email me off list and I could then copy them to you to post?

Another thought. We have something called a Lumenition optical Eye system over here. It uses the original distributor (minus bob weights) with a light sensor that is broken by a small blade which fits on the cam.

My Emerald system will run its fuel and ignition map off that sensor and a throttle position sensor, works fine.
I have a full setup with a distributorless system now, however I used the lumenition system for a long time and it was very nearly just as good.

Cheers
Simon
_________________
Blown is always best!