Flat Spot

[locost_bryan]

I used an online calculator to work out that the TC speed of 75kmh at 2500rpm looks correct for a 3.63 ratio.

75kmh at 3000rpm works out to a 4.3 ratio. When the 1800 was fitted, what gearbox did it use - 1800 or 1500? What were the original gearbox and diff ratios for the diesels? I suspect it has the speedo drive pinion for a 4.11 or 4.55 diff.

[LORENZO73]

Hi Bryan,
Yes it could be the speedo pinion different because i use a diesel gearbox. yesterday my mechanic try to take it out, but it is with stoneguard, and he is afraid to take it out. Chris told me the same like you. The gearbox diesel have the same ratio like the 1.8 gearbox,

So for sure that the TC green gave me more power, then the red one, we know that have different camshafts, but if i put them in the same speed in kmh, have to show me the same reefs?

Thanks
Renzo

[david painter]

hi everyone,
thanks all for your help. Just want to ask you, the sat nav or an app on the mobile they will give me bought accurate speed. But to know how much reafs the engines are doing, shall I use their own reafs counters?ù
Renzo

You can check the accuracy of the rev counter by using a RPM function on the timing light or multi meter. On the diesel car what drove the original rev counter? On petrol models it uses negative impulses from the primary ignition. On a diesel does not these pulses don't exist as such the rev counter usually uses alternator ripple to drive it. ( this is the un rectified output of alternator)
Dave

[LORENZO73]

hi everyone,
thanks all for your help. Just want to ask you, the sat nav or an app on the mobile they will give me bought accurate speed. But to know how much reafs the engines are doing, shall I use their own reafs counters?ù
Renzo

You can check the accuracy of the rev counter by using a RPM function on the timing light or multi meter. On the diesel car what drove the original rev counter? On petrol models it uses negative impulses from the primary ignition. On a diesel does not these pulses don't exist as such the rev counter usually uses alternator ripple to drive it. ( this is the un rectified output of alternator)
Dave

Hi Dave,
on the red one we fitted the refcounter of hillman imp which reads very accured, and we fixe it in the coil.
Thanks
Renzo

[david painter]

That only leaves you with the speedo reading incorrectly then. First I would check the GPS speed on both cars establish if you have a accurate reading in either car. If one is correct replicate speedo set up in the other car The most likely cause would be incorrect speedo drive gear in gearbox. Looking in my BL parts catalogue it suggest to me your car was originally fitted with a 25 tooth gear and car left factory with 4.55:1 axle ratio. The 1800 had 3.63:1 axle ratio and 20 tooth speedo drive gear (orange)
Dave

[MarinaCoupe]

Thanks guys.

For everyone’s info the 1500 diesel uses the 1.8 gearbox ratios and a 4.11:1 differential. Renzo’s car has a 3.63:1 differential now.

[LORENZO73]

That only leaves you with the speedo reading incorrectly then. First I would check the GPS speed on both cars establish if you have a accurate reading in either car. If one is correct replicate speedo set up in the other car The most likely cause would be incorrect speedo drive gear in gearbox. Looking in my BL parts catalogue it suggest to me your car was originally fitted with a 25 tooth gear and car left factory with 4.55:1 axle ratio. The 1800 had 3.63:1 axle ratio and 20 tooth speedo drive gear (orange)
Dave
marina speedo drive gear 001.JPG

Hi, Dave
Yes, i think that is the problem because i use a 1500 diesel gearbox, and i didn't notice that she have 25 tooth gear instead, 20 tooth gear, so you are correct with chris, because yesterday when i find the diff 3.63.1 , i contact him and he told me the same thing.
I phone my mechanic to take it out. He told me yes, but tomorrow because he, today fixe the diff.
I send photo of the speedo drive gear, tomorrow.
Thanks
Renzo

[david painter]

The 25 tooth one I took out of my pick up was White it has a 4.55 diff put in my car as temporary fix last year made speedo 5mph slow may car is currently running a 4.11 diff and gear should be black which I fitted the other day
Dave

[LORENZO73]

The 25 tooth one I took out of my pick up was White it has a 4.55 diff put in my car as temporary fix last year made speedo 5mph slow may car is currently running a 4.11 diff and gear should be black which I fitted the other day
Dave

This is the first time for me, that marina's have changes in gear speedo.

Renzo

[MarinaCoupe]

The 3.63:1 diff ratio requires the 20 tooth orange or brown speedo drive to give an accurate reading.

[LORENZO73]

The 3.63:1 diff ratio requires the 20 tooth orange or brown speedo drive to give an accurate reading.

Hi Chris,
I want to tell you many thanks for the time that you loose for me.
Renzo

[SLOW ITAL]

That only leaves you with the speedo reading incorrectly then. First I would check the GPS speed on both cars establish if you have a accurate reading in either car. If one is correct replicate speedo set up in the other car The most likely cause would be incorrect speedo drive gear in gearbox. Looking in my BL parts catalogue it suggest to me your car was originally fitted with a 25 tooth gear and car left factory with 4.55:1 axle ratio. The 1800 had 3.63:1 axle ratio and 20 tooth speedo drive gear (orange)
Dave
marina speedo drive gear 001.JPG

,

Unusual i know, i had a simlar problem years ago with the yellow ital. it apeared to be reading low at higher speeds, so we checked speeds against another marina driving behind.. It was acurate up to 40 mph, then got slower obove that. the marina doing a reg 70 mph, the Ital was reading 55 mph..
i tried another speedo drive, [ordered new] even changed the speedo to no avail.
It eventulally was traced to the plastic gear drive in the gearbox [ which the speedo drivegear was driven by] being cracked & moving on
the shaft. gear box out showed a split on one side. new one fitted & all ok...as i said unusual but a possability...
Gil...

[MarinaCoupe]

Good call Gil, but thankfully not in this case. Renzo has called me this morning and said that his mechanic has pulled the speedo drive wheel, it a black one with 23 teeth - so mystery solved.

[LORENZO73]

Good call Gil, but thankfully not in this case. Renzo has called me this morning and said that his mechanic has pulled the speedo drive wheel, it a black one with 23 teeth - so mystery solved.

. Now confirmed the problem of speedo. Many Thanks to everyone. Renzo

[LORENZO73]