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noddaz
noddaz Dork
2/6/15 3:01 p.m.

Other cars of that time period had 60k belts or 90k belts... Why do 944 belts not last long time? Just curious...

Tyler H
Tyler H SuperDork
2/6/15 3:20 p.m.

It's not so much how long they can last as what happens when they fail...and the cost to fix. Also, Porsche owners of the day didn't think they were buying 'just' a 944 and were more tolerant of the service interval. Just my WAG.

kanaric
kanaric Dork
2/6/15 3:41 p.m.

Alfa GTV6 were the same.

SEADave
SEADave Reader
2/6/15 3:42 p.m.

Just be glad it's not a Ducati - earlier ones had the interval at 10k kilometers, which is about 6,200 miles. Plus there are two belts and you are supposed to adjust the valves at the same time.

Kenny_McCormic
Kenny_McCormic PowerDork
2/6/15 3:42 p.m.

Testing indicated that stresses on the belt necessitated a 30k interval to prevent catastrophic failures.

turboswede
turboswede MegaDork
2/6/15 3:48 p.m.

No idea other than Porsche just didn't have a lot of experience with timing belts at the time and the resulting design, which was also leveraged in the 928's motor, is highly stressed for the application and fails more quickly than other designs. Remember this was designed back in the mid-seventies and Porsche wasn't exactly at its peak health

I mean look at this thing:

and then you've got the 928's timing belt:

http://ateupwithmotor.com/model-histories/porsche-928/

http://ateupwithmotor.com/model-histories/porsche-924-944-968-part-1/

http://ateupwithmotor.com/model-histories/porsche-924-944-968-part-2/

kanaric
kanaric Dork
2/6/15 3:52 p.m.

928 had a timing belt? I don't think i've ever seen a v8 with one

Tyler H
Tyler H SuperDork
2/6/15 3:57 p.m.

^^For the 944 uninitiated, the front belt is the balance shaft belt. The timing belt routing looks pretty routine to me.

turboswede
turboswede MegaDork
2/6/15 4:07 p.m.
Tyler H wrote: ^^For the 944 uninitiated, the front belt is the balance shaft belt. The timing belt routing looks pretty routine to me.

Yep. Just did one on my 951. Much more difficult than my 924's and nearly any other timing belt on a 4-cylinder I've ever done. Just way over complicated stuff from ze Germans.

The actual routing isn't too bad, once you get all of the junk out of the way to actually get to it. That balance shaft though. That's one odd duck.

Of course Chrysler added balance shafts to their 2.5L SOHC 4-cylinder using a chain, but what do they know (other than probably a decade more experience with designing inline 4-cylinders as well the info gleaned from Talbot and Mitsubishi)?

turboswede
turboswede MegaDork
2/6/15 4:07 p.m.
kanaric wrote: 928 had a timing belt? I don't think i've ever seen a v8 with one

At the time, it was the world's longest. 14 feet if I remember correctly.

oldeskewltoy
oldeskewltoy SuperDork
2/6/15 4:12 p.m.

One reason I'm a 4AG fan.... so simple... so easy... just belt, and tensioner, even the water pump is independent

mad_machine
mad_machine MegaDork
2/6/15 4:18 p.m.

the fiat 124 had a 20,000 mile interval. The belts didn't break (unless the cam driven airpump seized) but as they had "square" teeth instead of rounded, wore out faster until they finally slipped.

Granted, Fiat as the first to put rubber timing belts on it's bread and butter production cars (not just the high end ones) so you can excuse their way of doing things.

Question is.. did Porsche follow in their footsteps with tooth design?

carbon
carbon Dork
2/6/15 5:20 p.m.
SEADave wrote: Just be glad it's not a Ducati - earlier ones had the interval at 10k kilometers, which is about 6,200 miles. Plus there are two belts and you are supposed to adjust the valves at the same time.

EXACTLY….

I was about to comment that the SWMBO's berking monster needs one at that interval, I think it's bull e36m3 and those itallian berkers are just trying to ream you on another service, it doesn't even have valve springs and there are only 4 valves 4! and there are two belts!!!!!!!! The thing doesn't even rev that high. Are you really telling me that belt is worked harder than the one in my 2jz (24v/ one belt)? WTF?

turboswede
turboswede MegaDork
2/6/15 5:20 p.m.

In reply to mad_machine:

Both the balance shaft and the timing belt used round teeth. Something Chrysler didn't change on their 4-cylinders until the mid-80's and then it was only for noise purposes.

In reply to oldeskewltoy:

The original VW/Audi engine in the 924 was that way as well:

Porsche just has to show off their engineering apparently, especially after all the hoopla about their flat 6's and 12's.

Personally they should have stuck with a VW engine (think about what would have happened had it used the GTi's engine?) or gone with the replacement for the 4-cylinder that Audi was using, the inline 5. What a screaming banshee the 924 and 944's would have been.

racerdave600
racerdave600 SuperDork
2/6/15 5:45 p.m.

The timing belt on my 951 broke at like 30,018 miles. These numbers are not suggestions.

Streetwiseguy
Streetwiseguy PowerDork
2/6/15 5:48 p.m.

Germans are not very good at rubber. Simple as that.

Ranger50
Ranger50 PowerDork
2/6/15 5:53 p.m.

Because Porsche?

oldeskewltoy
oldeskewltoy SuperDork
2/6/15 6:25 p.m.
turboswede wrote: In reply to oldeskewltoy: The original VW/Audi engine in the 924 was that way as well: Porsche just has to show off their engineering apparently, especially after all the hoopla about their flat 6's and 12's. Personally they should have stuck with a VW engine (think about what would have happened had it used the GTi's engine?) or gone with the replacement for the 4-cylinder that Audi was using, the inline 5. What a screaming banshee the 924 and 944's would have been.

Same as the original Dasher/Rabbit/Scirroco engine? I worked for VW back in 1976-77.... nope I can see that now... original Dasher engine had the distributor mounted in the block

Streetwiseguy
Streetwiseguy PowerDork
2/6/15 6:30 p.m.
turboswede wrote: In reply to mad_machine: or gone with the replacement for the 4-cylinder that Audi was using, the inline 5. What a screaming banshee the 924 and 944's would have been.

You have a very different memory of 80's Audis from me, I'm afraid.

turboswede
turboswede MegaDork
2/6/15 9:22 p.m.

In reply to Streetwiseguy:

Can't be any worse than the CIS-infested gutless blender they originally used. Seriously, you had to manually adjust the followers and make sure you didn't break the damned oiling tube while you were in there.

And don't get me started on that nonsense that was CIS. At least with EFI and an engine that didn't wheeze its way to 95hp and could be repaired by your local VW/Audi shop it might have been a decent enthusiasts car like the GTi was.

turboswede
turboswede MegaDork
2/6/15 9:25 p.m.

In reply to oldeskewltoy:

It was the precursor to the Audi I5 and was used in the Audi 100LS which morphed to the 4000, etc. shares the same bellhousing pattern and there are a few other similarities with VW and Audi engines of the time period.

The bizarre part of that? That engine design was originally from Mercedes.

RexSeven
RexSeven UberDork
2/6/15 9:39 p.m.
kanaric wrote: Alfa GTV6 were the same.

The same goes for any Alfa V6-powered car. The timing belt must be changed every 30,000 miles or you risk bending 12 to 24 expensive Italian valves. This is what a 164 24V routing looks like:

On the 164 engines only, the rearmost sprocket can potentially spin a little on the camshaft because the belt doesn't wrap as much around it as the other sprockets. The hydraulic tensioner is shared with the Ferrari 360 Modena! Alfa changed the oil pump design (small sprocket under rearmost camshaft), revised the routing, and went from a hydraulic tensioner to a mechanical tensioner on the GTV/Spider/166 and later 24V motors.

gamby
gamby UltimaDork
2/6/15 9:50 p.m.
racerdave600 wrote: The timing belt on my 951 broke at like 30,018 miles. These numbers are not suggestions.

"Meh, I can probably take it another 500-1000 miles after 30k"

"NEIN!!!!!"

Streetwiseguy
Streetwiseguy PowerDork
2/6/15 9:51 p.m.

Audi 5000 with CIS...Trust me, the 1/2 928 motor is a better choice.

Knurled
Knurled UltimaDork
2/7/15 6:45 a.m.
kanaric wrote: 928 had a timing belt? I don't think i've ever seen a v8 with one

Not only did they have a timing belt, they had a sensor/switch in the tensioner to light up a warning light in the instrument cluster to tell you that your timing belt tension was dangerously loose.

The spec that I heard for 944 belts was 30k or two years, period. Drove it five miles in two years? Too bad, put on a new belt.

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