Quattroporte III catch-all thread

Wow, you must have one of the very first cars made in that case. I didn't realize they were available on the market until 1980.

Cool.

Any idea what your impulse generator outputs (voltage, ac/dc, sine/square wave)?

Thanks!

 

Hi Tony,

I understand. I'm trying to track down what the same speedo is on a Porsche and see what I can find there.

 

Amazing...

Thank you so much! DC or AC? Stable voltage, or varying with speed? I would expect the voltage to remain constant, and the frequency to change with speed.

I'm told that the speedometer is the same as used in Porsche 930/911 from late 1977 to around 1989/90.

 

LOL, love the 'test bed'.

thanks, Larry. I guess next step is to remove mine and see what it's outputting. I almost hate to ask, but you didn't happen to take note of the output voltage, did you? 5v? 6v? 12v? 18v?

I plan to hook mine up to a scope in the morning. If it's ok, that means that the only remaining place the problem can be is the speedo itself. Luckily there appear to be speedometer repair shops all over the internets.

 

Hi Larry,

lightbulb moment here - maybe in fact the impulse generator doesn't generate anything on it's own, as you state here. I found a site detailing how to check a Porsche VDO speedo/sending unit combo, and the first thing they said was to disconnect the impulse generator, run a set of leads from the generator harness plug into the car, turn the ignition on, and short the leads together rapidly (i.e. "generating" pulses, or shorts, that will cause the speedometer needle to move if it's working correctly).

I'm going to try that first, since it's late here and I really don't want to crawl underneath the car tonight. Kitchen table preferred to hard and cold asphalt.

No problem on the voltage bit, I agree, just seeing things work is often reward enough ;-)

 

On my way on my first grand tourer trip through Europe, and feel the need to broach the issue of mileage.

I had budgeted what I thought was a reasonable guesstimation of fuel consumption. Still without an odometer, I used the gps and google map distances as a guide, leaving with a full tank.

Well, I'm totally and completely flabbergasted at what I've figured my average consumption has been, driving on gently rolling open roads at between 90-120k/ph.

Before I share my findings, and on the continued hope that something is simply wrong with my car (and that can be fixed), may I ask other QP3 owners to share their mileage stats?

Thanks!

 

Still on the road, with spotty internet coverage.

I'm averaging 13mpg. You can literally watch the needle fall as you drive :-/

This is mixed highway driving, 200km were mountainous with various speed limits (60-90kph), the other 200 was flat motorway driving at 110-130kph.

The other thing I've noticed, having had a Jag Sovereign on loan the last few days while my wheel bearings are replaced, is that the QP3 doesn't "roll" very easily. On the jag I can let up on the gas and the car will coast along at the same speed. If I lift my foot completely, after a second it will start slowing down as the transmission (also automatic) pulls the speed down. I know that the QP3 isn't aerodynamic in any sense of the word, as someone here aptly put it, it's like pushing a brick down the highway

With the QP3, if you don't have the accelerator pressed down all the time, the car won't move. Lift just a little and it slows down immediately. I know that there's 10-15 years difference between them, it's just an observation.

The QP3 certainly gets a lot of attention and admiration from fellow motorists, though!

If this is the milage I can expect, I'm going to have to reevaluate my original plan to drive to Wales to get the car repainted. I thought it would be a fun road trip. Now I see it will be an expensive road trip. It's probably (a lot) cheaper to put it on a truck or boat instead.

It looks like my findings are pretty typical though. 13mpg or 5,6km/l. Ouch!

 

Finally back from my trip, had a lot of fun and met a true gentleman and specialist mechanic in every sense of the word. Not only did we get to borrow one of his Jaguars (1997 Sovereign 4.0l) he took us for a ride in his Rolls Royce (1990 Silver Spirit), what an impeccable car! He's a Jaguar specialist that comes highly recommended, and I figured since the rear end is a Jag IRS, who better to deal with it than a Jag specialist? He found that pretty much all of it is identical, with the exception of the axle nuts (Jaguar uses crown nuts, Maserati a proprietary ring nut that is set to a specific torque to give a certain amount of end float, then locked in place with a grub screw that collapses it in place, as far as I can tell).

I calculated that we got 12.8mpg on the rest of the trip while on rolling open highways, and will fill it up again today to see what we got on the more mountainous twisty roads last night. Probably a lot less.

I've come to realize that just because it was restored and taken good care of by a previous owner does not mean that even basic maintenance has been done by the owner(s) after him, and will be re-evaluating some of my basic assumptions (e.g. 'well this was rebuilt only a few years ago by a PO, therefor the problem must be somewhere else'). The mechanic who did the wheel bearings showed me how the right and left hubs had been put on backwards the last time they were done, and the axle (ring) nuts had been chiseled off and back on previously, instead of with the proper tool! He also mentioned (having only taken a very short drive) that something was "off" with the engine and it wasn't running as it should. He suggested checking the valve spacing first, then ignition timing, before re-adjusting the carburetors.

Again, and I know I sound like a broken record, but the glaring and obvious lack of performance has me wondering what might be the matter with my car. With every other car I've driven, you press the accelerator and the car goes forward. From dinky little 4 cylinder cars to big US finned monstrosities from the 50's. And whatever in between.

With the QP3, you press the accelerator, hear the engine start revving up after a few seconds, and then wait for the car to catch up. It won't go up a hill unless I floor it! It's almost like there's absolutely no torque at all. In Drive, on a level road, when I release the brakes the car stands still, instead of moving forwards. I can't imagine how this car couldn't get panned by the automobile press if this is typical of the performance.

Regardless of how you spin it, there's still 280HP pushing 2 tons of metal, the hp/weight ratio should be more than adequate to get the car moving when you press on the gas, regardless of poor mileage, differential gearing, or automatic transmission. I wish I knew someone with a dyno, it would be interesting to see how much power is actually making it to the wheels.

So the only thing left for me to conclude is that there must be something wrong with the car, I just need to find out what, and how to address it. Should keep me busy for a while ;-). Which leads back to the advice always given with classic cars, is that you really need to expect to redo the whole car unless you know it was properly restored and cared for by the previous owners - all of them!

 

Hi William and thanks,

I think you're right, I need to have someone who knows their stuff look it over. There is a very highly regarded mechanic here who was trained in the UK and works on a lot of classics, but he was booked until the end of July. I will definitely ask him if he could have a look later this summer.

Interestingly (and bafflingly) enough, I just went to fill the tank again - after the last leg of my journey from last night when we got off the ferry and filled the tank completely. I was expecting even worse mileage than before due to the mountainous nature of the road, frequent stops/roundabouts and small villages with reduced speed limits.

Well, after driving 235km, I was able to add 37.56 litres of fuel before it ran over (I literally kept adding gas until the 3rd time the pump stopped right before it overflowed).

Drum roll....

That equates to 14.7mpg. Mind blowing. And much better than my average earlier. The only explanations I can come up with are that either 1. fast Euro motorway driving at speed helped loosen up the engine and burn off deposits to improve performance or 2. keeping a slower average speed (90kmh vs 120) shows how truly non-aerodynamic the car really is ;-)

The plot thickens...