Andrew Smith Posted May 5, 2014 Report Share Posted May 5, 2014 (edited) Hi Folks, Been out in the 'Saffron survivor' this afternoon for the first time since driving it the 8 miles home when I bought it two weeks ago. This is my fourth TR6 in the last 30 years, the last three having OD. VUX was a CP car, the other two were CRs and whilst I'm not looking to open the debate on CP vs CR on the performance stakes (BTW, the CP wins hands down!) I did notice today that 'Saffy' which is non-OD CP feels a bit quicker through the gears? I believe the gear ratios on OD and non-OD CP cars is the same, or are they? - both my CPs had/have 3:45:1 diffs, although VUX wore 185/70 and 'Saffy' wears 165/86; not sure if that would make a difference............ Also, I have to say that this car with its standard suspension and ride height (VUX was lowered by 20mm, with stiffer springs with poly bushes all rounds) has a more comfortable and compliant ride, or maybe it's just my age?! That said, VUX was far better through the twisty bits! Cheers Andrew Edited May 5, 2014 by Andrew Smith Quote Link to post Share on other sites
stuart Posted May 5, 2014 Report Share Posted May 5, 2014 Non overdrive is quicker due to not having the extra bits of overdrive to turn. I noticed the difference on my 4a after fitting overdrive having been used to it without for 16 years. Polybushed/lowered/big tyres arent for everyone. Stuart. Quote Link to post Share on other sites
Guest ntc Posted May 5, 2014 Report Share Posted May 5, 2014 Non overdrive is quicker due to not having the extra bits of overdrive to turn. I noticed the difference on my 4a after fitting overdrive having been used to it without for 16 years. Polybushed/lowered/big tyres arent for everyone. Stuart. Yep But would you go back to none overdrive now? me no chance Quote Link to post Share on other sites
Alec Pringle Posted May 5, 2014 Report Share Posted May 5, 2014 Hi Andrew, you can have the cake or the halfpenny . . . . but not both. Given the limitations of TR suspension design, improved handling is a tradeoff against reduced ride comfort. Handling is fine for low flying to Sunday lunch, ride comfort tends to come into its own hauling from Surrey to Dordogneshire. Of course the non-o/d box is quicker. Setting aside Uncle Stan's mythical 150bhp, in modern DIN measurement 135 would have been tops and 130 more like run of the line. Subtract 5 horses for distributor and metering unit wear etc, then another 5 for modern fuel against 1960s 101 octane, then take into account the losses through a less than wonderfully efficient drive train . . . . and you'll be under a hundred at the back wheels for sure. Now stick an overdrive unit into the drive train, even a nice new one on fresh oil wil be soaking up 1bhp/1000rpm, and a well used unit on oil past its sell-by date can be increase that by a third or even half. At full chat a difference of at least 5 horses at the wheels is likely to be noticeable, even to those with cast iron seats to their pants. The only real benefit to o/d is long haul touring, keeps the motorway revs down. Cheers Alec Quote Link to post Share on other sites
Andrew Smith Posted May 6, 2014 Author Report Share Posted May 6, 2014 Thanks chaps, Glad to hear it wasn't the 'early' onset of some ageing process! Alec, Yes, driving from Surrey to the South of France via Dordogneshire whilst a little tiring, particularly on the Dordogneshire roads (just like Surrey's), VUX took the motorways in its stride retuning a healthy 32 mpg (70-80 mph OD top) on the 8 hour/500 mile drive from Minzac to Bagnols-en-forêt (via Carcassonne) in the Var. As for actual bhp, VUX was rolling road tested by the previous owner and it seems the power at the rear wheels was quite healthy at 122 bhp; although one never knows how accurate these things are: Cheers Andrew Quote Link to post Share on other sites
Andy Moltu Posted May 6, 2014 Report Share Posted May 6, 2014 The power documented as measured at the rear wheels often isn't the real power measured - frequently it is a calculation of estimated "flywheel power measured at the wheels" using an algorithm to add the power at the wheels to the calculated drive train losses measured on overrun. It's a far from exact science - compounded by the inherent calibration issues of rolling roads. Quote Link to post Share on other sites
Bill944T Posted May 6, 2014 Report Share Posted May 6, 2014 "'Saffy' which is non-OD CP feels a bit quicker through the gears?" The Motor road test of 1969 states "that overdrive 2nd knocked a second off the 60-70 mph time" (ie no gearchange). It also states "that it was a full four seconds faster to 100 mph than the non-overdrive TR5 --- an interesting study in the effects of gear ratios." Regards Bill Quote Link to post Share on other sites
Tom Fremont Posted May 6, 2014 Report Share Posted May 6, 2014 "'Saffy' which is non-OD CP feels a bit quicker through the gears?" The Motor road test of 1969 states "that overdrive 2nd knocked a second off the 60-70 mph time" (ie no gearchange). It also states "that it was a full four seconds faster to 100 mph than the non-overdrive TR5 --- an interesting study in the effects of gear ratios." Regards Bill That's consistent with what I saw in contemporary road tests. 2nd gear in O/D extends the launch to 70+ mph and likely accounts for most of the advantage above, rating a close 2nd to cruising in 4th O/D for me. Losses due to the O/D are of the lubrication variety; factory specification oils such as SAE 90 EP will spend more ponies than SAE 30W as recommended by specialists over here. Likewise the diff which can stand synthetics ( in my experience at least ) which pour like water instead of molasses; I gained 1 mpg switching to it in my driver. Quote Link to post Share on other sites
AlanT Posted May 6, 2014 Report Share Posted May 6, 2014 (edited) During testing my 250W Chinese electric-motor turned the gearbox flange at 1500 rpm all day long without overheating. https://www.flickr.com/gp/90670218@N04/29G787 In case your units are weak this is 1/3HP. But it will only do this when the oil has warmed up. I have to start in "low range" which is 600 rpm until the oil warms. This takes about 15mins. Its running the OD and the gbox and it matters not if OD is in or out. Edited May 6, 2014 by AlanT Quote Link to post Share on other sites
Andrew Smith Posted May 6, 2014 Author Report Share Posted May 6, 2014 (edited) All I know is that I'll probably fit an OD unit next year (well, Pete Cox will!!) for touring and it'll be a J Type based on availability, conversion cost, future maintenance and the fact that I rarely used 2nd OD on VUX. Cheers Andrew Edited May 6, 2014 by Andrew Smith Quote Link to post Share on other sites
RobinTR6 Posted May 6, 2014 Report Share Posted May 6, 2014 Pete did my J type on a CP car , what a difference from the S type, so much smoother in and out , more like a modern auto box. And the wiring is much simpler so that's a bonus too. Quote Link to post Share on other sites
Tom Fremont Posted May 6, 2014 Report Share Posted May 6, 2014 Hi Andrew, I was going to say that retro-fitment of an O/D wouldn't detract too much from the value-based-on-originality, but a J-type ? Now that would be a sacrilege Quote Link to post Share on other sites
Andrew Smith Posted May 6, 2014 Author Report Share Posted May 6, 2014 Hi Andrew, ................but a J-type ? Now that would be a sacrilege That word again....... I was thinking I could conceal a switch and not tell anybody....... Cheers Andrew Quote Link to post Share on other sites
Guest ntc Posted May 6, 2014 Report Share Posted May 6, 2014 Hi Andrew, I was going to say that retro-fitment of an O/D wouldn't detract too much from the value-based-on-originality, but a J-type ? Now that would be a sacrilege +1 and a stupid bracket to make it fit the chassis Quote Link to post Share on other sites
graeme Posted May 7, 2014 Report Share Posted May 7, 2014 All I know is that I'll probably fit an OD unit next year (well, Pete Cox will!!) for touring and it'll be a J Type based on availability, conversion cost, future maintenance and the fact that I rarely used 2nd OD on VUX. Cheers Andrew Good choice Andrew, you won't regret it. I have a saloon J type(modified to TR6 spec) in my 4A. Try and get the 28% reduction for long legged and economical cruising. Cheers Graeme Quote Link to post Share on other sites
Peter Cobbold Posted May 7, 2014 Report Share Posted May 7, 2014 There goes the patina..... Seriously the present gearbox is all OE and low mileage. A recon OD gearbox may have all sorts of poor quality non-OE parts eg synchro cones. So reliability could be lost too. Peter Quote Link to post Share on other sites
Bill944T Posted May 8, 2014 Report Share Posted May 8, 2014 "During testing my 250W Chinese electric-motor turned the gearbox flange at 1500 rpm all day long without overheating." But I doubt if when there is say 75 kW load at the output, that the input power would be just 75.25 kW due to the losses when transmitting this significant power between input and output. You may well have to apply 80 kW to obtain 75 kW at the output. Regards Bill Quote Link to post Share on other sites
AlanT Posted May 8, 2014 Report Share Posted May 8, 2014 Well I would reckon that the viscous drag will rise considerably at 4500 rpm. Lets say it goes as the square of speed. This would be 9 times the loss at 4500 compared to 1500rpm. So its it's about 3HP. Quote Link to post Share on other sites
Tom Fremont Posted May 8, 2014 Report Share Posted May 8, 2014 It's probably a cube function. Still, in the lower gears the losses would be considerably less than in top. Quote Link to post Share on other sites
AlanT Posted May 8, 2014 Report Share Posted May 8, 2014 I thought about this, but the gbox gets quite warm with 200W dissipation. A continuous 2kW would make it very hot even allowing the extra cooling when actually in motion. 20kW is too much loss in just the gbox. Quote Link to post Share on other sites
Andrew Smith Posted May 8, 2014 Author Report Share Posted May 8, 2014 There goes the patina..... Seriously the present gearbox is all OE and low mileage. A recon OD gearbox may have all sorts of poor quality non-OE parts eg synchro cones. So reliability could be lost too. Peter I never said anything about replacing the gearbox Peter, just floated the idea about fitting an OD - all this excitement......... Cheers Andrew Quote Link to post Share on other sites
Willie Felger Posted May 8, 2014 Report Share Posted May 8, 2014 Hi Andrew, Congratulations on your new car. For what it's worth I put a J-type gearbox with overdrive in the Pea and my TR6 using a Healey 3000 gear knob switch. The gear knob obviously didn't need any holes or mods and the overdrive - same as in the Pea - is way smoother on changes than the A-type and the new design Moss conversion bracket was OK as well.(The old type was awful and broke so I made my own for the Pea) The Pea's box was £100 from a fellow Camb Follower and the TR6 one £150 from Mick Dolphin and both worked a treat. Maybe I was lucky but for that price I was willing to take a chance. I guess you'll know that the J overdrive doesn't have a solenoid - it's a switch which has not given me a problem - and the overdrive works at a much lower oil pressure. Interesting too, to see VUXs power curve - that's the same figure as the Pea before it had the dizzy rebuilt! Keep TRucking buddy, see you at Harrogate! Willie Quote Link to post Share on other sites
Andrew Smith Posted May 9, 2014 Author Report Share Posted May 9, 2014 Hi Willie, Thanks for the info and yes, it's a cracking TR6. Not sure I'll be at Harrogate, but if I am I'll see you there! Cheers Andrew Quote Link to post Share on other sites
jean Posted May 9, 2014 Report Share Posted May 9, 2014 Andrew here's my o/d experience. As yours my 6 is an early 70 built without o/d. After a trip around Wales I found out the disadvantages of the non o/d , fuel consumption and gearchanges on the short climbs and descends along the coast. So I when back home I contacted my local garage about fitting an o/d. Fortunately my friend from Red Baron just had a complete J type box lying around and so he was able to fit it straight to my 6. I drove with this box for about 3 years, but as my car still has it's matching parts I decided that an A type together with the original box would be a better choice. So back to my friend Jo to see about the possibility to fit an A type my box. No problem for him and seen the huge amount of TR's he is servicing he was able to flogg the J type with gearbox to a client waiting for a conversion. so Andrew I guess with an early 6 the choice will be made quickly, I do not regret my choice. yes the A type swallows a little more HP and is a little rough in switching, but it belongs to the model year. I just dont understand Willie when he mentioned NO SOLENOID... the J type also has a solenoid, a different single action one, not necessitating a relay... as far as I know Quote Link to post Share on other sites
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