DRB #5

[Bill Musarra]

I am still plagued with two issues that I can't get a handle on. The first is a long standing one of the alternator overheating. It now is doing it intermittently. Last week I was working on the second problem of the clutch not releasing. The engine was running fine for about 15 minutes. I shut it down to readjust the linkage to the shifter and the clutch. When I started it back up the belt began smoking almost instantly. I have redone all the major ground connections at the battery, the block, and frame, as I suspected the block ground when it first started many moons ago. That ground is coming off the trans adapter which is aluminum. I scuffed up the ground strap connections as well as where they go to the frame, which is the cross member across the back of the engine. Now that bar is ceramic coated, and I don't know the merits of ceramic coating for a ground location, so I roughed it up with sand paper as well. It needs to be redone since several mods following the coating process. All the battery leads from the electronics posts were snugged up. I managed to get the engine to run for about 3-4 minutes before the belt began smoking. The belt feels snug, but I can see it flexing some when the motor is running, so I will tighten it up just for good measure and see.

Concerning the clutch, I think now it has come down to the wrong size of master cylinder. With a full pedal throw the slave is moving a mere 5mm. It needs to travel approximately 13. So I will go beck to my collection of MCs and try it again. My problem is that I can't get any figures on the size of the slave. So Its the old try it and see. The feel of the pedal is hard, so it is taking too much pressure to get the little movement out of the slave. The Master that is in there now is a 5/8" unit. Any suggestions would be greatly appreciated.
On other fronts, I have mounted the canards and they look great. They are scuffed up aluminum for now. I will either leave them this way or polish them.

Bill

 

[Seymour Snerd]

I don't know the merits of ceramic coating for a ground location, so I roughed it up with sand paper as well. It needs to be redone since several mods following the coating process. ... I managed to get the engine to run for about 3-4 minutes before the belt began smoking. The belt feels snug, but I can see it flexing some when the motor is running, so I will tighten it up just for good measure and see.

...I can't get any figures on the size of the slave. So Its the old try it and see. The feel of the pedal is hard, so it is taking too much pressure to get the little movement out of the slave. The Master that is in there now is a 5/8" unit. Any suggestions would be greatly appreciated.

Bill -- I'm nearly certain the ceramic coating is a very very good insulator (that's what they make power line insulators out of!) , so you either need to go completely around that piece with a ground cable, or remove entirely the coating from wherever you want to make an electrical connection. You need bare metal between any two joined places through which current passes.

I'm really struck by your alternator problem. For a healthy alternator to overheat there has to be some huge load on the electrical system. IOW this symptom is sort of the opposite of having a bad ground (which would prevent things from loading the alternator). First thing I would do is measure alternator voltage when it's running (and overheating or about to overheat). The thought is maybe its regulator isn't working and it's running unregulated, putting out way too high a voltage which would in effect overload it as it trys to fry the poor battery. If it measures anything over 15 volts that's probably the problem. This overloading of the alternator would also explain the belt problems. If you find that to be the case check out your battery because the battery will have been very unhappy at being subjected to high voltages. It may have "boiled away" some of its electrolyte or otherwise be in bad shape.

If you do measure a high voltage coming from the alternator, measure it again running but disconnected from anything. You'll probably get a really high voltage (like 20-60) in which case you found your problem and should have the alternator repaired or replaced.

The belt shouldn't really be "snug"; you should easily be able to tug it at least 1/8 inch in either direction radially. If it has to be tight to work there is something wrong and an overload would be an example.

Re the clutch, it's hard to make sense of the system without knowing the slave diameter. Can you pull back the boot on the slave cylinder so you can see the inside of the cylinder? If so you can measure it.

Also the symptoms you're reporting don't really go together (in a "single fault" situation): hard pedal in a healthy system should mean the slave is moving too far for any given pedal movement. Lack of motion at the slave would correspond to a soft pedal. So something funny is going on; I suspect two different problems are in play.

 

[EGLITOM]

Hi Bill

may be attached clutch calculation sheet will help. I would dissasemble the slave to be able to do a proper calculation before the trial and error process.
the chart helped me a lot and is realy close to the real forces you feel.

I finaly decided for the MLP slave and it works quite well.

Thanks
TOM

 

[Bill Musarra]

Well, setback number 909. It seems that the folks at Hi Torque sent me the wrong starter(see Hi Torque starter mis match). This destroyed the ring gear and will have to be repaired/replaced. This sets me back(again) for the first drive. So it will be a while before that happens. Very disapointing as I thought all the flaws were behind me and I could get the car on the road. This will result in a fight,as I am sure they won't want to stand behind the product several years old, even if it was only used 20-30 times this last year as documented here.

Bill

 

[Terry Oxandale]

Bill,

Looking at the photo, specifically the throwout bearing assembly; what holds the assembly onto the diaphram. The reason I ask is my hardware from KEP has no snap-ring or any othe pieces that could be used to hold the bearing in place. I know the 915 clutches use a snap-ring to hold the bearing in place, but references I've seen say the 930 large clutch (deeper bell housing) does not. Can you clarify or enlighten me on this?

 

[Bill Musarra]

Terry,
To answer your question, there is no snap ring.If you look at the first pic you will see that the diaphram in the unattached view is concave in nature.

With the throw out bearing you will notice there is a grove at the back of it. That grove is where the fingers sit while relaxed(it will fall out if not held in).

Notice the gap in the pic above at the top of the bearing.
As the pressure plate is torqued down the fingers move to the convex position and the fingers expand into the grove holding the throw out bearing in place.

That this is why you don't push the clutch pedal too far. It will push the bearing out of the diaphragm causing damage to the diaphragm as it then goes into a more shallow grove or even to the fork arms. I could even see it causing the clutch to be engaged rather violently with no way of releasing!!:shocked:

Bill

 

[Dave P]

Bill: Maybe you have checked already. If the internal seal in the master cylinder is forward of the fluid entry port it could give you a heap of trouble. It would seem like it is functioning but only giving you partial stroke. I Have seen this in several brake systems causing drag and residual pressure.

 

[Bill Musarra]

Thanks for all the input. I will now have plenty of time to research each of the issues. The alternator has been checked out by an electrical shop early on. They converted it to a one wire setup and checks later on showed no problems. Good output(within normal limits on the machine) later on when checked again. I have cleaned up the connection and was trying to crank the engine when the starter problems arose. When the alternator would over heat, it would do it within less than 30 seconds, and only the pulley would be scorching hot. This was also intermittent as some times it would crank an run for long periods of time. When they did the last tune, they had it running for an hour as they set the vacuum and butterfly settings. When the clutch wouldn't release they had the car on the dyno. So we unhooked it and I brought it home. Then the alternator started its thing again.
After cleaning up the connection point I was attempting to crank the engine. It would usually take a time or two for it to fire up and run. With these few revolutions the pulley would remain cool. So I may have solved the problem???? Any way, won't know for a while. Will be getting in touch with KEP to see what the repair or replacement will run. Any bets on what HI Torque will say???
Tom, thanks for the spreadsheet. Am I supposed to be able to input numbers and it do calculations?? If so it isn't doing it for me. I have disassembled the slave and it is 23.6mm. Your numbers for the .75 master should be O K. So a question. My pedal ratio is 5.5 to 1. Will that lower the pressure at the pedal? Will disassemble the master and check it out for any problems.

Bill

 

[Seymour Snerd]

...When the alternator would over heat, it would do it within less than 30 seconds, and only the pulley would be scorching hot.

The alternator works the hardest right after you start the engine, since that's when it's restoring the energy the start motor has been using. Given what your starter motor was up to (i.e. chewing up your ring gear) it was probably drawing way more current that is normal, so when the engine finally fired the alternator had an unusually large job to do so the two issues may have been working together to an extent.

This reminds me of another electrical mystery thread recently where the alternator belt adjustment was mechanically intermittent. In your case, perhaps if the belt got loose, but not completely loose, it could act like it was working but still create a lot of heat from the belt slipping against the pulley.

Or... the heat (for whatever reason) was being generated in the armature so the most direct path for the heat was through the armature shaft to the pulley...???

 

[Seymour Snerd]

...Am I supposed to be able to input numbers and it do calculations?? If so it isn't doing it for me. I have disassembled the slave and it is 23.6mm. Your numbers for the .75 master should be O K. So a question. My pedal ratio is 5.5 to 1. Will that lower the pressure at the pedal? Will disassemble the master and check it out for any problems.

You need just one more piece of data to use the spreadsheet: the slave cylinder's leverage over the TO bearing, IOW the ratio of the length of the arm the slave cylinder pushes on to the length of the clutch fork (axis to TO bearing centerline).

 

[Bill Musarra]

It is the standard for Porsche of 2:1. All my numbers are the same as Tom's spreadsheet at the top for a standard set up. The only difference is the pedal ratio. So I don't know how much pressure or travel it will take given the difference.
I have an assortment of master cylinders to play with. They are all standard Tilton units about 6 inches in length. The depth of the slave is aproximately 80 mm and the lenght of travel apears to be about 25mm. The stamping on the slave is 6567 if that helps.

I am wondering if the way I am setting it up on the car is the problem.
If the slave should be at full copmpression, does that put too much pressure on the TOB sort of like riding the clutch??? Best I can measure the pressure at compression is about 20-30 lbs. measured with a weigh scale. Is this making sense?

Bill

 

[Seymour Snerd]

It is the standard for Porsche of 2:1. All my numbers are the same as Tom's spreadsheet at the top for a standard set up. The only difference is the pedal ratio. So I don't know how much pressure or travel it will take given the difference.

Ah so. OK if everything is the same except his pedal ratio is 5:1 and your's is 5.5:1, then you will experience 10% less pedal pressure to achieve any given TOB pressure. On the flip side, the TOB will move 10% less for any given pedal motion. So the answer to your question "will that lower the pedal pressure" is "yes," by 10%

When I went throught this whole exercise (finding out what pedal pressure is "too much", verifying my lever lengths, etc. see http://www.gt40s.com/forum/gt40-tec...131-clutch-pedal-pressure-what-do-i-want.html) the conclusion was that I want at most 50 lb pedal pressure and that with my McLeod clutch that takes an overall ratio of about 12:1 (what McLeod suggested).

This is pretty much in line with what you are doing. You have an overall ratio of 17:1 and a pedal pressure of 44.6 lb, which is right where it ought to be in order to operate a clutch with release pressure of 761 lb (3387 Newtons in the spreadsheet). The main difference between you and me is McLeod says my clutch needs only 500 lb to release so you need more leverage to get the same pedal pressure. I would expect you to measure higher than 20-30 lb. Are you measuring the pedal pressure to completely release the clutch (IOW just before the end of its travel)?

IAE, I am still stumped by "it is taking too much pressure to get the little movement out of the slave" You should be getting .28" of TOB travel for ~5" of pedal travel (make sure you've taken up all the slack before you measure TOB motion). You said you're getting 5 mm (.2") TOB travel. If so we have 0.08" or 28% of TOB travel unaccounted for.

Is it time to redo the measurements and verify the dimensions?

 

[Bill Musarra]

Allen,
You got me to thinking about the problem. It is solved quite easily(I think??). Take a look at the four pictures. Here is the slave in the neutral position. No pressure on the cylinder.

Here is the cylinder under compression and it takes about 50# of pressure to get it there.The spring is under the boot.

Now look at the shift forks. Here it is in the engaged position(clutch pedal out).

Here it is in the neutral/unengaged position(clutch pedal depressed).

What is wrong with the pictures????

The slave cylinder is spring loaded in the wrong direction. It wants the slave to be open. That is why it took so much pressure to move the cylinder 4 mm. It was already extended. The spring should be holding the cylinder closed, not open. I will have to have a discussion with my Porsche mechanic!!

Terry's question got me to thinking and my response to him was incorrect. As you tighten the pressure plate down, the fingers go from concave to convex. In order to release the clutch, it has to go more convex, pulling the pressure plate away from the clutch. The TOB is pulling the fingers outward/more convex, not pushing them in. So I stand corrected.
The spring would exert 50# of pressure on the TOB just to compress the spring and close the cylinder and remain clamped to the clutch disc. This would reduce the clamping force of the pressure plate. Not good.
The only time there should be pressure on the TOB is when the clutch is depressed. Constant pressure on the TOB will destroy it in a very short time. Like riding the clutch pedal
So it means I have the wrong type of master cylinder.

If someone knows this is not correct, please let me know!!

Tom,
What type or part number do you have for the standard slave cylinder. I can only find MLB for Ducate bikes. Where are the ones you are using found?? Size and part numbers??Are they for external setups or are they for inside the bell housing?

Bill

 

[Seymour Snerd]

Maybe this is some weird Porsche thing in which case I should stay out of it, but usually (here in America) when you press on the clutch pedal it sends fluid to the slave cylinder which causes its shaft to extend, which pushes on the clutch arm, which causes the TOB to go forward, which pressses forward on the diaphragm springleaves and in so doing, because they pivot in the middle, allows the pressure plate to move rearward and releases the clutch. What I see in your pictures is backwards from that, but would be explained if it was intended for a "pull type" slave cylinder (one that retracts when you supply fluid). So I'm totally confused.

 

[Terry Oxandale]

Great information and photos Bill. This may save me a ton of confusion!

The "pull" type would work identically if attached to the other side of the fulcrum where it would have been mounted originally, so it appears the spring is causing an issued, but perhaps not "the" issue. In regards to the SC. Could you not remove the spring (under the boot), and instead connect a spring from the arm (that the SC pushes against) to the bracket holding the SC? This would relieve the preloading (that's one heck of a spring) on the diaphram, plus keep the arm in the fully unloaded position until the clutch is depressed (preload the SC).

 

[Bill Musarra]

Alan,
If you look at the fork and the TOB you will see that the fork has to be in front of the TOB. So the only direction it can go is back away from the motor.

Terry,
If you look at the exploded picture of the slave you will see a lip on the brass looking piece that supports the spring. It sits at the mouth of the cylinder. I am on my way out to talk to the Porsche mechanic to see what we can do to make it work or replace it with something else that will. Will post the results this afternoon.

Bill

 

[Seymour Snerd]

... So the only direction it can go is back away from the motor.

Sorry, I now understand that you have a "pull type" clutch. Please disregard any comments about things being backwards.

 

[Bill Musarra]

O K Here we go.
1. The guys at Hi Torque identified the starter as the 101NL which is the high performance 930 unit on a long shaft. My measurements of the distance from the bellhousing mount to the back of the ring gear is 1 3/4". The long shaft puts the front edge of the gear to the back of the ring gear. These were the measurements I gave Hi Torque when I ordered the starter and that is what they said I needed. Wear marks which didn't show up very well in the pics show the full engagement of the starter with the ring gear.
2. Remember when I said the engine was backfiring when the distributor gear got eaten up and slipped a tooth. That will weaken the ring gear as it tries to spin the motor in the opposite direction while the starter is turning. Big stress there, as it was backfiring on the same cylinder every time I was trying to start the engine.
3. Now for some better news. The ring gear comes off the pressure plate after removing the pressure plate and clutch with a few taps of a screw driver. The ring gear is held on with the mounting bolts. So the whole assembly does not have to be shipped to California for repair. They will send me a new ring gear for $145. Bolt it back on and I am back in business.

I took the slave cylinder out to the Porsche mechanic and he gave me the full story on the slave cylinder. The slave cylinder is the correct one. Once installed it is compressed. The long armed lever, which rotates on the central shaft freely is installedon the compressed slave. The short arm shaft is then placed on the central shaft with its face as close to the adjustment screw as it can. A circlip holds it in place. The adjustment screw is then adjusted to about 0.5 to 1 mm from the short arm shaft. A spring is placed on short end of the long armed lever to BALANCE the spring on the slave cylinder. This keeps the slave cylinder compressed and that then allows the pedal to move the pressure plate/clutch assembly. The dealership was out of the springs, so one was ordered.

Bill

 

[Bill Musarra]

I reinstalled the trans. The spring finally arrived and was installed on the trans. The slave was bled. I then put the spring on tension to the adapter plate(a bracket will have to be made to hold it) and it slowly compressed the slave cylinder. Interestingly enough, the slave compresses the slave about half way back or exactly 15mm where the two springs are balanced. That is the exact distance of travel in Tom's spreadsheet. So now I have to measure the pedal travel that will give me that distance and set the stop based on that. I will try to get some god pics. I am pretty tied up the next few days with a house project(will they ever end??) so I will post when done.

Bill

 

[Bill Musarra]

Well have had a little time to work on the car. On installing the ring gear the only wire connections undone were the starter as the trans had to be pulled to get to the ring gear and the O2 sensor disconnected as the exhaust had to be removed. All new gaskets were made with the copper goo stuff. Alittle messy but done. I discovered that the mufflers don't line up perfectly and had a slight gap on the underside, so a generous amount of the goo was added there before the claps were reinstalled. The new spring for the clutch was set and its proximity to the exhaust will necessitate a guard to keep the excessive heat from affecting it.

The side mirrors and their mounting hardware are in place. I am waiting for the actual mirrors to be made and then I will alter them for the cameras.

The mounts are Lexan and are made to be used with or without the windows in place.
I have had one draw back that can't be explained as of yet. When I got every thing buttoned up and went to start the engine, I was greeted with no response from the FI or spark. Plugs were dry and with a screw driver in the plug boot no arcing. After thinking about it I hooked the laptop up and when trying to connect with the computers, I got a "No ECU found". I thought of what I had done while waiting for the ring gear. All I had done was to spot weld some of the shift cable brackets to keep them from flexing. So in talking to the FAST people, we decided to send the computers in and see if I had fried one of the boards. All fuses were fine and not blown???? So I didn't think the welding would have fried them. Test at FAST revealed them to be in perfect condition. I got to thinking more and looked around the wiring and I found the sensor wire to the crank trigger had been pinched in raising the back of the engine to free up the trans mounts. That was spliced back together and would explain the no run situation. After the boxes arrived I hooked them up and tried again and still no run. The engine turns over well and when the throttle is depressed the engine turns over a little faster, which tells me there is some communication going on(electronicly). The computer still show no ECU, which got me to thinking that my computer had crashed some time ago and I now don't have the drivers for the new software(or old for that matter). The computer when hooked up to the FAST boxes told me that new hardware had been found. So that is some good news. They updated my software while it was at FAST and I don't have the disc for that version. So that is why my computer won't connect, but not the no run situation. At FAST they did a software analysis and ran one of their engines with the boxes, so it should run with mine???? So I am still looking for the culprit.

Bill