RyanPerrella

I am going to try and find a machine shop tomorrow to pull the 100 tooth timing ring off my DD flywheel to be replaced by the timing ring from the Automatic S4 and i have a few concerns about this.

Ive been told that the S4 timing ring needs to be properly relocated onto the flywheel. This makes obvious sense as there is a gap of about an inch to an inch and a half or about 3 teeth in the timing ring. I know this is for the ECU and is a necessary part of the engine electronics and i want to make sure that when the new ring is pressed on i have no clocking issues with this.

Its my understanding that the crank position sensor doesnt exactly measure crank degrees (Does the HAL sensor do this?) but that the crank sensor is there to count revolutions so that the EZK knows when to fire spark as the engine is a 4 stroke and 2 crank revolutions are required. So basically its my understanding that the crank sensor just counts full revolutions and NOT crank position. Is this correct?

If the above is correct then i would imagine that if the ring is not aligned EXACTLY correct then this could be an issue. I imagine getting within 1-2 degrees is somewhat easy but i want to make sure that thats going to be ok first before doing so.

I am lining up the early flywheel with the S4 flywheel to mark the early flywheel where the gap in the timing ring should be. I am lining up the dowel holes of the flywheels as a starting point and this job seems to be fairly simple when doing this. However i was looking at Carl's website of his aluminum flywheel and see that his positioning of the timing ring is NOT correct as i see it on mine. I have pics of mine from the backside, but when i flip them over my timing ring gap is in a different location relative to the dowel hole in the flywheel.

Can someone please confirm that my measurements are correct? Can someone else also please clarify for me how precise this new timing ring needs to be aligned to work properly on a 1990 model car.

Thanks

Below are pics of the early flywheel on top of the S4 flywheel to mark ring gap location. Also Carl's flywheel is shown but it can be compared with mine (once you flip them over in your head) and you can see they are not the same. Would love some clarification on this as well.

If you use the smaller dowel hole as a reference and call it 12 o'clock. Based on the measurements from my S4 flywheel the gap should be around 4 o'clock, yet by the looks of Carl's flywheel, his appears to be around 8 o'clock. This is a massive difference.

John Speake

It is the engine flywheel sensor that gives the accurate timing control for the engine electronics. That's why it has all those teeth :-)

The Hall sensor only gives a signal every other engine rpm to aid the knock control system.

So it is essential that you get that timing ring onto the new flywheel to a degree or less.

jcorenman

Ryan,

Here's a picture of the 5-speed flywheel from our '88 S4, just replaced with a 85/86 flywheel and twin-disc clutch. Mark Anderson set up the flywheel for us, matched this perfectly.



I centered this picture as best I could with the dowel hole at 12:00, looking forward from the clutch side, and the gap is indeed at 4:00. All I can think is that Carl's ring was just set in place for the photo, or maybe his picture is swapped left-right.

I hope this helps.

Cheers, Jim

RyanPerrella

John, thanks for clarifying, i guess i had the HAL and Crank position's jobs reversed somewhat.

Thanks Jim, the picture confirms what I have. How do you like the dual disc setup on the S4? My main goal was to reduce rotating mass, did you notice a difference immediately when you made the switch? What did you think when all was said and done?

Lizard928

What I would recommend doing is to have your machine shop fab up a jig based on the 87+ flywheel and that will allow them to get the ting onto the DD flywheel to the EXACT same location.

jcorenman

We like it, better in every respect. The pedal is lighter (which Sue likes in particular) and the heavy clutch just never seemed consistent with the brakes and steering. The lighter weight/lower inertia is also nice and more responsive to the trottle-- nothing dramatic but feels just right instead of feeling a bit slow to rev. And the engagement is very smooth- it starts engaging closer to the floor than the single-plate clutch, then starts seriously engaging about halfway up. So far no sign of any adjustment issues, I just pushed the IP all the way back as suggested here and it seems to be happy.

The S4 PP is massive, a heavy iron casting. The earlier PP is aluminum, add in the intermediate plate and the total is still some 12# lighter as I recall, and a smaller diameter- I am guessing that the rotating inertia is half.

Bottom line, I think it is a great "upgrade" and we're happy that we did it. Mark A. helped us with the parts and was terrific.

Cheers, Jim

dprantl

After daily driving the S with the DD for 8 years and now switching to the single on the GT, I can say that I miss the DD very much (so much so that I'm seriously considering a retrofit). The GT's pedal is much heavier, the engagement point is much higher and I can notice the slower revving.

Dan
'91 928GT S/C

RyanPerrella

I am curious how you guys that have done this get the rings swapped?

Do you use a torch and heat them up or do they just press off? I found a guy in Round Rock that can do this but i am curious wether i should suggest using heat or just using a press for this job.

Suggestions from those that have done this?

jcorenman

I used a phone

Seriously, Mark A. supplied the '85-86 FW (used, but barely) and S4 AT timing ring, and mounted it for us. It looks to be pressed on and then tack-welded, you definitely do not want it going anywhere.

Cheers, Jim

RyanPerrella

I went to the local guy here in Round Rock and the thing he was most concerned with was getting the timing ring OFF the S4 flywheel. He had no pullers that large so i thought why not just use the 6 tapped bolt holes that you use to attach the flexplate with some longer bolts and use that as a means to press off the timing ring. I am trying to find bolts now to fit this.

For the DD timing wheel he suggested simply using a drift and tapping it out a bit at a time till its off.

I will report back with the news on how well the bolt method worked for the S4 timing ring removal.

RyanPerrella

my bolt idea is working, but because of the far bolt spacing for the flex plate its warping slightly in areas where there isnt a bolt. So i was also using a prybar to move the space in between the bolts to help remove the ring.

Its taking a WD-40 break for now, the last thing i want to do is crack the ring somehow.

RyanPerrella

i believe you, but i don't have a torch

Mrmerlin

Ryan cruise out to home Depot get yourself a self firing torch handle and 2 cans of yellow Mapp gas.
Put your flywheel in the freezer before you leave, heat the ring, the mapp gas is hotter so it heats faster.
The ring will drop off of the flywheel put the ring on the new frozen flywheel its pretty easy then let the ring cool to room temp

RyanPerrella

it popped off in one piece with my bolt method. I will look for a torch tomorrow and try and remove the 100 tooth ring and put hte S4 ring on the flywheel or just have the machine shop guy deal with it.

Either way its off!

Louie928

Ryan,
I was faced with the same dilema. I had a single disk flywheel like you have and made a fixture using it as a guide. I made a hub that would fit inside the center hole. Next, I made a block that would fit inside the tooth gap. Next align the flywheel so the gap is placed where you want it on your fixture. For me,that was about center on the frame of the fixture. Bolt the gap block the fixture base. Next drill and tap a hole for a flywheel bolt. Lastly, very carefully find the center of the small reference hole in the flywheel and mark that on the fixture frame. Use a transfer center punch for this. The location of this reference hole is vital. You can bolt the flywheel in place and use the reference hole as a drill guide, but don't enlarge it.

Once the locating fixture is made, you don't need the S4 flywheel anymore. Remove the 100 tooth ring from the '85 flywheel. you'll probably have to cut it off. Heating it won't be enough because you'll heat the flywheel too and you don't want to warp it. Use a air driven cut off tool to slice through between the teeth in a couple spots. Secure the flywheel and strike the segment between the cuts to try and pound it off by stretching or cracking the segment off. Now, you have to get the 60 tooth ring off the S4 auto flywheel. I had a tough time with that. It's shrunk on. Don't try to heat it to get it off. IIRC, I cut the flywheel part out from inside the ring. I used an acetylene torch, but it had to be done in short segments so as to not heat the ring too much. After the flywheel inside of the ring is weakened enough you may be able to carefully press the ring off. The important thing is to not distort the ring, or stretch it.

Now you have the S4 ring and the '85 flywheel with no ring. Put the flywheel on the locating fixture. Keep the bolt loose, and put in the pin. The flywheel shouldn't move. Tighten the bolt to secure the flywheel. Put it all in the freezer. Pick a time when your wife isn't home and put the ring in the oven at about 350F. The plan will be to slip the hot ring over the cold flywheel and let it shrink on. Have some spring clamps (like big clothes pins) ready to use to hold the ring in place while it cools. You have to have something to hold the ring. It should just go over the flywheel with quite a lot of clearance and unless you have something to hold it, it can go on crooked and cool that way. As the ring cools, and flywheel warms, the fit will get tight enough to remove the clamps. At this time you can tap with a hammer to be sure the ring is on straight and even all around.

It's a good idea to spot weld the ring to the flywheel in a few spots. See where the pressure plate fits and there are places where a weld spot won't interfere. Mark those places for a weld spot. I don't think there are interference spots on the front side so mark some spots there too. 3 or 4 around the circumference is ok. Now take a Dremel tool, or similar, and cut a small pocket at the joint of the flywheel and ring where you've marked where the spot welds will be. A shallow pocket like 1/2 of a bean is fine. The purpose of the pockets is so the weld won't end up like a pile on the surface of the flywheel. Next, lay some weld in those pockets. A wire feed welder works fine for this because it doesn't need to put a lot of heat into the flywheel in one place. Let the flywheel cool between welds to reduce warping. Have the hybrid flywheel surfaced, and balanced.

That's how I did it. There are probably easier ways, but the vital thing is to get the S4 ring on the '85 core in exactly the same place as it is on a S4 flywheel. Here is a couple pictures. One is of the "fixture" and the other is of an S4 flywheel that's quite rusted. So rusted, I couldn't get the tight fitting locating pin all the way in for this pic. It's what was laying handy for the pic.

Louie

http://members.rennlist.com/louie928...%20fixture.jpg
http://members.rennlist.com/louie928...%20fixture.jpg