First Post

[bluedexter]

Hello! This is my first post here since signing up last September. Firstly I want to thank you all for the wealth of useful information and advice you provide, it has certainly helped me enormously both before and since buying my first 944. So, now I have my 944 and I am really chuffed although I have only done about 600 miles in it.

I have a number issues which need resolving, nothing too serious, the first being the speedo which reads 14% fast relative to my satnav. Some of this is down to worn rear tyres but was wondering if this something anyone else has experienced.

Chris.

 

[robwright]

Hi mate and welcome. What year is your car because 14% error seems rather large to me to be just worn tyres. The rolling circumfrence doesn't change that much from new to worn. Are they the correct size i.e. the correct combination of rim size and tyre wall height? The reason I ask about age is because it could be a dodgy speedo pick up. Later cars are driven from the gearbox electronicly and earlier cars are of the wind up variety I believe.

 

[bluedexter]

Thanks for your quick response Rob. The car is a '91 S2 with 16" D90 wheels and 225/50's on the rear. I have actually calculated what the speed should be according to the final drive/5th gear ratios and tyre sizes and allowing for the amount of wear on the tyres the speedo reading is still very high.

 

[MarkK]

Welcome,enjoy your car![]

 

[robwright]

Exactly the same as mine mate 16" D90's with 225 50's. Mine are definately ready to be changed and in fact probably a little past it [] and my speedo is still reading spot on. I have no doubt Porsche figured this into their equations when designing. I would seriously have a look at your speedo pick up on your gearbox. Swap it for a substitute one if you can and see if it makes any difference.

 

[pauljmcnulty]

The car is a '91 S2 with 16" D90 wheels and 225/50's on the rear. I have actually calculated what the speed should be according to the final drive/5th gear ratios and tyre sizes and allowing for the amount of wear on the tyres the speedo reading is still very high.

Welcome! [] That's the right tyre, on the right wheels, for the car. So, even with no tread left (as mine have until Friday []) there's no reason for a significant error there. I know nothing technical, so someone please correct this, but as I understand it the sender on the later cars is a pulse sender; an electronic sender that, I'd have thought, would fail intermittently, as mine did, with a flickering or failed speedo. Not an overall change in reading over the whole range. Is it possible that this has failed in the past, a common fault, and been changed for the wrong part? Maybe off a different model with different wheel diameter, 968, 928 or similar period 911?

 

[bluedexter]

Thanks for the welcome Paul. The starting point would seem to be a replacement sender. I will try to identify the correct part and see if I can get a replacement. Sorting out the correct parts for the various evolutions/models does seem to be a bit of a minefield, judging from from what I have been reading. By the way, how do I put a signature on my posts? Duh!

 

[pauljmcnulty]

By the way, how do I put a signature on my posts? Duh!

My profile, and it's about 14 lines down. Signature's easy, avatar is a right pain for most of us. [] You're right that parts can be tricky by model, but your S2 should be fine. The only problems are with changeover models, or the runout 2.7 luxes. The suppliers in the faqs should sort you out.

 

[Diver944]

Hi Chris and congratulations on your first post and the recent purchase. Feel free to post some pics whenever you take some as we love people to show off their new toys [] Is your speedo 14% off through the whole range or just when cruising on the motorway? I have heard of one person who had to reindex his needle because it over read ie it read 20mph even when standing still and then 100mph when at 80mph. That was a simple case of dismantling the instrument cluster then pulling off the needle and repositioning it. Yours does sound like a sender problem though. Where in the country are you and we can perhaps recommend a good Independant Specialist local to you To update your signature click on 'My Profile' at the top of the screen and it will bring up a new page with many boxes to fill in with your details.

 

[andrew_churcher]

Congrats on the purchase Chris! I am 6 months into S2 ownership and its been great fun so far.

 

[zcacogp]

A pulse-type electronic sender would surely either fail by not picking up reliably, leading to less pulses being fed to the speedo and a lower speed being displayed, or randomly picking up an errant signal, causing occasional over-reading? Is the gearbox original/is the final drive original? Mind you, I'm not sure that this would explain the over-reading error either. Glad you are enjoying the car otherwise tho'. Good to have you on here. Oli.

 

[zcacogp]

ORIGINAL: pauljmcnulty So, even with no tread left (as mine have until Friday [])

Few too many doughnuts again Paul? [] Oli.

 

[bluedexter]

Thanks for the advice guys. The speedo reading starts from zero and the reading seems to be 14% optimistic across the range e.g. at 2000 rpm the speedo reads 51 mph and satnav reads 45mph. I have taken readings form 30 mph to 70 mph and the % error is almost identical. I did have a quick look at the final drive ratios of other models and IIRC the turbo has a lower final drive ratio but nothing like 14%. Before replacing the sender I am thinking of giving it a good clean and just check to make sure that there are no other obvious problems in that area but not knowing how this thing works I might be wasting my time. I also notice that the part number for the sensor is the same for all 'oval dash' models and the 968? If the final drive ratios are different, how can this be? Or maybe I am mistaken. Don't spent too much time on this guys because I can live with it for the time being, I just wondered if there was a simple solution.

 

[MarkK]

Your car looks really nice[]

 

[evoboy69]

I have exactly the same problem with my ’89 S2. I have just had a replacement Sender fitted in the rear diff and it’s made no difference.[] I worst part of this problem is that it's counting on the miles quicker!

 

[Mike_Pollock]

Hi and welcome - late as usual today(!) - I'd have thought that it is as likley to be the head unit as the sender. Which is easier to change first? I have a early car with mechanical speedo (which reads 10% LOW) so I'm not sure. Mike

 

[DivineE]

Let me know if someone finds the solution to this because my new car does it. Sounds like exactly the same percentage over read and my other two turbos of the same age were bang on exactly 100 at 100 (one even on the same wheels). There must be a common part failing or more likely as it's so consistent incorrectly fitted.

 

[Skooby6]

Hi , I have a bit of a problem with mine too it's an 86 Lux, the thing is it's not overreading (that i know of) but it does occassionally have a "fit" and just die, or it will flicker like mad. Thankfully when it does die on that rare occassion i judge the speed by the volume of the wheel bearings....Genius, no? []

 

[david924s]

ORIGINAL: bluedexter Thanks for the advice guys. The speedo reading starts from zero and the reading seems to be 14% optimistic across the range e.g. at 2000 rpm the speedo reads 51 mph and satnav reads 45mph. I have taken readings form 30 mph to 70 mph and the % error is almost identical. I did have a quick look at the final drive ratios of other models and IIRC the turbo has a lower final drive ratio but nothing like 14%. Before replacing the sender I am thinking of giving it a good clean and just check to make sure that there are no other obvious problems in that area but not knowing how this thing works I might be wasting my time. I also notice that the part number for the sensor is the same for all 'oval dash' models and the 968? If the final drive ratios are different, how can this be? Or maybe I am mistaken. Don't spent too much time on this guys because I can live with it for the time being, I just wondered if there was a simple solution.

My S2 is out by 5mph, at every speed it over reads by 5mph when measured against my Sat Nav, I have 17" wheels on mine but with lower profile tyres so the rolling circumference is not that different. My friend with a 968 says his car does the same so I just live with it and adjust accordingly. I think if the sensor was faulty it would either read or not read I suppose it could be a problem with the pick up not sensing properly or maybe you have had a different gearbox fitted with slightly different ratios.

 

[pauljmcnulty]

I have a bit of a problem with mine too it's an 86 Lux, the thing is it's not overreading (that i know of) but it does occassionally have a "fit" and just die, or it will flicker like mad. Thankfully when it does die on that rare occassion i judge the speed by the volume of the wheel bearings....Genius, no?

Genius! [] That's exactly the symptoms my '86 Lux had, it's the sender at the back. You can take it off and clean the contacts, but mine needed a new one. Not a horrendous cost.