ShaunC Posted July 15, 2014 Report Share Posted July 15, 2014 Anyone suffer with lack of torque at low RPM? Doesn't matter what gear I'm in and is particularly an issue when the revs dip when pulling off when you need a bit of a quick get away. It is worse if you use wide open throttle at low RPM. The rest of the rev range is good, in particular when the engine is singing above 4000RPM. Running at CP series PI with luminition. Tick-over timing is a bit advanced, 8deg at 850 RPM. I've been back and forth with this but has little effect on the low rev range. Cheers, Shaun. Quote Link to post Share on other sites
peejay4A Posted July 15, 2014 Report Share Posted July 15, 2014 Shouldn't it be 11deg BTDC at idle. So, retarded if anything. Quote Link to post Share on other sites
Ade_TR6 Posted July 15, 2014 Report Share Posted July 15, 2014 Shaun, I can only speak from personal experience when I had a similar problem after replacing injector hoses and mis-timing the metering unit when I replaced it. I know there are those on theforum who will suggest it doesn't really make much difference, but it really was noticeable and exhibited the symptoms you describe. But, I guess, that would assume you have had the metering off recently - if not over to the experts... Quote Link to post Share on other sites
RobinTR6 Posted July 16, 2014 Report Share Posted July 16, 2014 Timing should be 12 degrees and I'd double check the butterflys as they are especially sensitive at low revs, ie very small openings. Quote Link to post Share on other sites
john.r.davies Posted July 16, 2014 Report Share Posted July 16, 2014 "Wide open throttle at low revs" = v.low inlet manifold pressure = rich fuelling from Lucas M/u But the same would be caused by a leak in the vacuum hose from manifold to M/u. Also, check the choke cable. I had a persistent low torque probelm and wide open throttle, due to the choke cable being slightly kinked and the chike lever not closing properly -> over rich at low revs. John Quote Link to post Share on other sites
Peter Cobbold Posted July 16, 2014 Report Share Posted July 16, 2014 (edited) Trick camshaft ? ie too much overlap for pleasant road use, designed for high rpm induction not low rpm torque. Peter Edited July 16, 2014 by Peter Cobbold Quote Link to post Share on other sites
ShaunC Posted July 16, 2014 Author Report Share Posted July 16, 2014 Thanks guys! MU timing found at 'AA', as per 19.35.01 brown bible. I have reset the Static timing to 11deg as per 86.35.00, sheet 1. I've no idea why I was thinking 8 was too advanced! The only vacuum leak I have is at the brake servo where the master cylinder attaches to the servo (there is an impression in the servo which I'm assuming is to allow air to be expelled from the servo when the brake pedal is depressed?). I'm not sure if this leak is normal? It doesn't seem right to me and it's been on the list to investigate for a while now. Temporarily sealing this leak effectively drops the idle by approximately 100RPM. Despite originally saying the timing didn't make much difference, an A-B comparison has proved me wrong????, and it doesn't feel like it's being over fuelled below 1500RPM at WOT as before, and a bit more willing to pull through the low rev range. Having said that, it's not amazing but I have nothing to compare to and this may be a feature of the CP set up, and my recent touring in a 4.2 Rover V8 has spoilt me! Quote Link to post Share on other sites
Peter Cobbold Posted July 16, 2014 Report Share Posted July 16, 2014 Keep going - try 13 or 15 BTDC. The timing marks on the pulley are unlikely to be true, the rubber damper in the pulley distorts with age. Quote Link to post Share on other sites
peejay4A Posted July 16, 2014 Report Share Posted July 16, 2014 You need to address that vacuum leak. You've proved that it's having an effect on fuelling. Quote Link to post Share on other sites
ShaunC Posted July 17, 2014 Author Report Share Posted July 17, 2014 Hi. Vacuum leak is coming from seal 66 in the attached, most likely the ID - contact point around the rod that passes through. It's all a little corroded in this area too which needs addressing. There is a substantial gap between the master cylinder boss and the OD of this seal, in the order of 4mm, is this normal? Quote Link to post Share on other sites
john.r.davies Posted July 17, 2014 Report Share Posted July 17, 2014 If there is a continual suck at this point you have identified the reasons why: A/ your brake assist doesn't work B/ the your have continual richness and C/ your low torque at low revs. The poor M/u thinks the throttle is wide open all the time! John Quote Link to post Share on other sites
ShaunC Posted July 17, 2014 Author Report Share Posted July 17, 2014 Locating quality spares is the next task! Quote Link to post Share on other sites
Peter Cobbold Posted July 17, 2014 Report Share Posted July 17, 2014 (edited) I disagree with John. That leak is only responsible for 100rpm at tick-over - that is b***er all air flow. It is about one eigth of tickover flow, so its an even tinier fraction of the flow when the buttlerlies are opened.So the leak wont mess up the MU or make for a rich mixture, or affect pick-up. As far as the MU goes its no different form the leak at the tickover adjuster valve Unbalanced butterflies as Robin says are a possible cause. Different air flows in cylinders but the same squirts of petrol don't make for optimum performance. And a known problem area. Give it more spark advance. Its no good using the book method of timing against the pulley mark - its may well not be at TDC. So find the optimum by loosening the disy clamp just enough to be able to slowly turn the disy to and fro a few mm. Re-clamp when the tick-over rpm are maximum. If it pinks upon wot retards by turning the disy anticlockwise a mm or so ( measured at cap circumference). If it really flies above 4000rpm rather than starting to run out of puff I would suspect you have a non-standard camshaft. Too much overlap will kill low speed pick-up whatever you do to mixture or spark. But that 4000rpm 'flying' could also be due to retarded spark. Normally max advance is at around 3000rpm, above that no more is needed. if the static spark is retarded it pushes the rpm at which no more advance is needed to higher rpm. Peter Edited July 17, 2014 by Peter Cobbold Quote Link to post Share on other sites
ShaunC Posted July 18, 2014 Author Report Share Posted July 18, 2014 As far as I can tell, the leak at the servo is only causing high tick over, currently at 900RPM with idle the adjuster fully in. It's a leak I need to resolve either by changing the rubber seal, although it does not look a very good design...you have a moving rod passing through a static seal so I would engaging this is a common issue? Brakes seem fine despite the vacuum leak. Butterflies I've attempted to set up previously but there is a little too much wear in the linkages, I've averaged them out as much as I can, I'm intending to improve this at some point by replacing and bushing the worn parts, however this would only cause issues when feathering the throttle, my issues was with a fair amount of throttle at low revs, it would feel as though you'd pulled the fuel enrichment knob out. Advancing timing to 12deg has resulted in a noticeable improvement. I've check the timing mark by stuffing a rod down cylinder one and the TDC mark seems reasonably accurate. If there is someone in the area with a PI who I could compare with, give me a shout you can have a go in mine and see what you think... Quote Link to post Share on other sites
Mike Collins Posted July 18, 2014 Report Share Posted July 18, 2014 How about clamping the pipe to the servo and trying it? Have to push the brake pedal hard though. Mike. Quote Link to post Share on other sites
Peter Cobbold Posted July 18, 2014 Report Share Posted July 18, 2014 (edited) TDC- reasonably accurate? Towards TDC the piston is barely moving upwards at all for large crank degrees of rotation: http://www.pattakon.com/opre1_files/OPREdwell.gif For a stroke of 95mm that graph shows that 20 degrees of crank rotation from either side of true TDC moves the piston by about 0.95mm Correct way is to screw a piston stop into the plug hole eg old plug with rod welded on. or bolt to screw in. mark the stop position going clockwise on crank then anticlockwise. True TDC is halfway between. Much quicker to turn the disy to best t/o rpm.!! If the spark is wrong no amount of fiddling with the PI will cure stumbling. Peter Edited July 18, 2014 by Peter Cobbold Quote Link to post Share on other sites
Allan Jezzard Posted July 18, 2014 Report Share Posted July 18, 2014 Shaun, reference your posting #7, I have been troubled by that illustration for some time. It states "black shading represents rotor", then says "diagram AA shows the sleeve port almost covered by rotor". Not if black area is rotor; therefore I believe black area denotes hole! How thinks anyone else? Cheers Allan Quote Link to post Share on other sites
Kevo_6 Posted July 18, 2014 Report Share Posted July 18, 2014 Shaun, reference your posting #7, I have been troubled by that illustration for some time. It states "black shading represents rotor", then says "diagram AA shows the sleeve port almost covered by rotor". Not if black area is rotor; therefore I believe black area denotes hole! How thinks anyone else? Cheers Allan Hi Allan I think your right as thats how I understand it. In the Lucas PI injection cards tips it states the hole in the rotor should be visible as an eclipse at the top. I think the brown bible has missed out the word "hole". Quote Link to post Share on other sites
ShaunC Posted July 18, 2014 Author Report Share Posted July 18, 2014 Hi peter. I've previously measured, but not as accurately the piston TDC, similar to how you've described but I admit I need to get hold of an old plug and drill the centre out to fit a rod and measure the two points with a DTI or verdict gauge to be as close as possible. Hi Allan. I've read this as the black section is the open port as you have described. Quote Link to post Share on other sites
ijonsson Posted July 19, 2014 Report Share Posted July 19, 2014 Hi, How "off" can the timing mark be? When my car runs OK and I check with timing light it's 22-24 deg. Can this be caused by worn rubber damper and can the damper break and cause real trouble? Could another possible reason be distributor drive fitted wrong, how many degrees does one cog wrong mean (my guess is that one cog means more than 10-12 deg.)? /Inge Quote Link to post Share on other sites
peejay4A Posted July 19, 2014 Report Share Posted July 19, 2014 Inge if you cannot trust your TDC mark you should check it using a piston stop in number 1 cylinder. Quote Link to post Share on other sites
ijonsson Posted July 19, 2014 Report Share Posted July 19, 2014 Inge if you cannot trust your TDC mark you should check it using a piston stop in number 1 cylinder. Well, I've better start fabricating one, seen lot of DIY advice here one the forum. . Quote Link to post Share on other sites
Peter Cobbold Posted July 19, 2014 Report Share Posted July 19, 2014 (edited) Hi, How "off" can the timing mark be? When my car runs OK and I check with timing light it's 22-24 deg. Can this be caused by worn rubber damper and can the damper break and cause real trouble? Could another possible reason be distributor drive fitted wrong, how many degrees does one cog wrong mean (my guess is that one cog means more than 10-12 deg.)? /Inge Inge, Do you have a late-USA low compression cylinder head? I have an 8.5 head and find that around 18BTDC gives the best tickover. Its more than 12 BTDC for the 9.5 heads but that is to be expected. So your 22-24 may not be too bad. If its too advanced you'll hear 'pinking' upon hard accleration at low rpm. If its running OK then its close to the right setting. It could be a few degrees out maybe but certainly not a big cog-sized difference. The damper-pulley is something to be careful about. I would not presonally stand over it holding a timing light at say 5500rpm..I stop at 3500rpm - and am not really happy doing that. If one does fly apart it has a lot of energy.. But no-one has reported a failure on a TR as far as I know. Yet. " Uploaded on 22 Dec 2011 The crankshaft vibration damper failed at the end of the straight.and destroyed the water pump and radiator. Then I couldnt brake because of the cooling fluid on the tires.."" Peter Edited July 19, 2014 by Peter Cobbold Quote Link to post Share on other sites
Denis Posted July 19, 2014 Report Share Posted July 19, 2014 (edited) I rotate the crank by hand, several times and just eyeball that point when the piston dwells, then just turn the dizzy till the points open for No1, works for me everytime, not very scientific but it runs fine. Edited July 19, 2014 by Denis Quote Link to post Share on other sites
ijonsson Posted July 19, 2014 Report Share Posted July 19, 2014 Inge, Do you have a late-USA low compression cylinder head? I have an 8.5 head and find that around 18BTDC gives the best tickover. Its more than 12 BTDC for the 9.5 heads but that is to be expected. So your 22-24 may not be too bad. If its too advanced you'll hear 'pinking' upon hard accleration at low rpm. If its running OK then its close to the right setting. It could be a few degrees out maybe but certainly not a big cog-sized difference. The damper-pulley is something to be careful about. I would not presonally stand over it holding a timing light at say 5500rpm..I stop at 3500rpm - and am not really happy doing that. If one does fly apart it has a lot of energy.. But no-one has reported a failure on a TR as far as I know. Yet. " Uploaded on 22 Dec 2011 The crankshaft vibration damper failed at the end of the straight.and destroyed the water pump and radiator. Then I couldnt brake because of the cooling fluid on the tires.."" Peter As far as I know, and compression test verify it, I have an 9.5 head. I did advance until I got slight pinking under heavy load and then retarded the dissy a bit, so .... lot of degrees on timing mark and no pinking. I've serviced the dissy (cleaned and greased) but have no idea of condition of springs etc., I'm thinking sending it for restoration after driving season is over here in Sweden, just to eliminate this as a cause and get a dissy I can trust. But as it is, the car runs fine, I was just curios how the timing mark could be so "off the scale". Quote Link to post Share on other sites
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