Murena high fifth gear

[macaroni]

  With the high fifth and the inaccurate tachometer, you will see something like 120 kph at 3000 rpm and 160 kph at 4000 rpm.

Roy

So last night, on my private road, very near the M25, I hit 160kph, which was actually very close to 100mph, according to my satnav, and the tacho was bang on 4000rpm, so I guess I have the high 5th gear? Do you recall supplying one to Phil Siddall, Roy?

Michel, congratulations on the imminent baby. I can highly recommend a Multipla for families and the interior chaos becomes quite charming after a while.

[JV]

So last night, on my private road, very near the M25, I hit 160kph, which was actually very close to 100mph, according to my satnav, and the tacho was bang on 4000rpm, so I guess I have the high 5th gear?

I hope for you that you have, but I'm afraid that there is a fair chance it is just a larger inaccuracy of your rev counter.

Jan

[michaltalbot]

So, I'm back from the "CX guy" and situation is as follows - when he said that he has 5th gears, he though only one wheel (the right one on my picture) because it includes synchrons, the rest he allways puts into the trash   BUT, he has some complete 2,5 Turbo gearboxes and price for one is cca 250,-Eur. So we've made a deal and next saturday, I will change all parts   I will make videos before and after and put them on youtube, just give me 10 days  
Anyone intersted? 

[Oetker]

Ok Michael, I am looking forward for the tutorial.
What I am interested in is if the gearbox of a 2500 diesel (not turbo) has the same gearing.
I can buy one for €35.-

[michaltalbot]

You can easy check it here:
http://www.globalcar.com/datasheet/Citroen/1974_Citroen_CX25_Diesel.htm

And it seems that 2,5 D isn't good one, because its top gear ratio is 0,8 what is more than at Murena (0,73) but we need less and than only one version of CX has it lower - 2,5 TurboInjection which has 0,67 and that's what Roy was speaking about - Vmax will be 225km/h.

[Oetker]

Thanks for the info michael.
I start looking for the right one.
I take my time on this one, because several other jobs comes first.
Maybe I take off the complete gearbox, because the 2nd gear synchro is beatable.
It works wel, but if I do a trafficlight race the synchro is not fast enough.

[roy4matra]

So last night, on my private road, very near the M25, I hit 160kph, which was actually very close to 100mph, according to my satnav, and the tacho was bang on 4000rpm, so I guess I have the high 5th gear? Do you recall supplying one to Phil Siddall, Roy?

No, he did not get a kit from me.  However, the details have been up on my website for many years, so it is possible that some owners may have read it, and then gone ahead with obtaining the parts and doing the modification without my knowledge.  Those figures certainly look correct.  You would have thought though, that if he did put the high fifth gear in, it would be such an attractive selling feature... so why was it not mentioned when you bought it from him?

Since we know the rev counters are inaccurate, and often I have found two cars will even read differently, so they are not even the same inaccuracy, which could also account for the figures.

There is another cross-check anyone can do - a 2.2 on standard wheels and tyres should be doing 26.38 kph per 1000 rpm in 4th gear.  So at 3000 rpm it should be doing 79.14 kph.  And at 33.89 kph per 1000 rpm in fifth it should be doing 101.67 kph at 3000 rpm.  If it actually reads approx. 110 kph in fifth at 3000 rpm then it is likely to be showing around 86 kph in fourth at 3000 rpm.

Even better, you can check the gap difference.  At 3000 rpm in 5th if you drop to 4th it should show about 3850 rpm.  If you have the high fifth gear the gap is going to be larger.  So at 3000 rpm in fifth, if you now change to fourth it will read something like 4170 rpm.  Any rev counter inaccuracy will be there all the time so the gap difference should really show whether the mod. has been done.

Roy

[Matra_Hans]

According to globalcar.com datasheet
The CX GTi prtrol has topgear reatio of  0.73 and final drive of 4.77
The Murena 1.6 has  topgear reatio of  0.73 and final drive of 4.77
The Murena 2.2 has  topgear reatio of  0.73 and final drive of 4.35

It seams that globalcar.com's datasheets are not accuarate. Or at least there are some confusion.

Hans

[JV]

Thanks Roy,
Good tips.
Jan

[michaltalbot]

Matra-Hans - but we don't need the final ratio! Important is only the 5th gear   and when we know (thanks to Roy) the number of teeths, we can easily control it.

[macaroni]

 so why was it not mentioned when you bought it from him?

He was too busy trying to convince me it was a genuine "S"...

Even better, you can check the gap difference.  At 3000 rpm in 5th if you drop to 4th it should show about 3850 rpm.  If you have the high fifth gear the gap is going to be larger.  So at 3000 rpm in fifth, if you now change to fourth it will read something like 4170 rpm.  Any rev counter inaccuracy will be there all the time so the gap difference should really show whether the mod. has been done.

Roy

I tried this and changing into 4th at 3000rpm in fifth puts the revs at about 3750rpm, so it looks like the standard 5th.

[michaltalbot]

After very very long rainy period, I've spent this day on my motorbike (2008 ZX6R Ninja) and not with my gearbox, but at the evening I took my Murena for test drive with standard 5th gear to make a video "Before". There was some trafic on the highway, so I've made only one short video in speed arround 180 - 190km/h. I will put it on youtube and put the link here later this evening. After some kilometers I reached the top speed 212km/h on my GPS and held it for long 5 seconds. My tachometer showed only 205km/h and rewmeter was close to 6000 rpm ( 212 km/h = 6280 rpm real) - so I was afraid of damaging the engine, because short overloading is O.K. but longer time overloading could be very dangerous and at 212km/h the rews are on the limit.
On video, I'm going to load in next minutes, can be seen that my tacho shows less than reality, at 184 km/h GPS it shows 180 km/h and rewmeter shows 5000 rpm, but reality is cca 5300 rpm.
So tomorrow morning I will change the 5th gear wheels (they are allready demounted from CX gearbox and prepared in my garage) and will make the test drive. Hope there will be less traffic so I'll try to make short video "After" 

[Jon Weywadt]

After very very long rainy period, I've spent this day on my motorbike (2008 ZX6R Ninja) and not with my gearbox, but at the evening I took my Murena for test drive with standard 5th gear to make a video "Before". There was some trafic on the highway, so I've made only one short video in speed arround 180 - 190km/h. I will put it on youtube and put the link here later this evening. After some kilometers I reached the top speed 212km/h on my GPS and held it for long 5 seconds. My tachometer showed only 205km/h and rewmeter was close to 6000 rpm ( 212 km/h = 6280 rpm real) - so I was afraid of damaging the engine, because short overloading is O.K. but longer time overloading could be very dangerous and at 212km/h the rews are on the limit.
On video, I'm going to load in next minutes, can be seen that my tacho shows less than reality, at 184 km/h GPS it shows 180 km/h and rewmeter shows 5000 rpm, but reality is cca 5300 rpm.
So tomorrow morning I will change the 5th gear wheels (they are allready demounted from CX gearbox and prepared in my garage) and will make the test drive. Hope there will be less traffic so I'll try to make short video "After" 

Better watch out. the police are watching U-tube too and your video is considered evidence and an admisiion of guilt.  They nailed one dude, who posted a video of himself doing close to 300 (as far as I remember) on his motor bike. Took his license and fined him heavy. So be careful what you post there. 

[michaltalbot]

Thanks, but this video is not a prove that who was driving that fast and also where it was taken  if that guy agreed with what police said, and if there wasn't filmed his face, than he is stupid. It's normal situation here, that you receive letter from police with your photo at for example 120km/h on 80km/h speed limit. So you go to police office and say that you don't agree that it's you on the picture, and that's all, police can't do nothing with it. Owner of the car mustn't be automaticaly responsible for violation made by his car and if owner say, that car was driven by someone from his family he don't  have to say his/her name. Or you can say that car was driven by Abraham Bush, living in New Zealand, who visited you and is looking same as you, and they know that only one thing they can do is - discard it. Police is only for fun, only stupid men with no education are doing this work...

[michaltalbot]

And finally, here is the video:

http://www.youtube.com/watch?v=21kVxZMiMTo