I’ve got a gems that I’ve done the heads on, it ticks over for hours ok, but directly it's out under load it will overheat, I’ve changed rad, stat, repaired leaking Orings and pipes, checked water pump, flushed the system twice, driving me nuts. I’m thinking there’s a problem with the block.
I’m wondering if I can put a Thor short engine with flywheel and cps , I can’t see why not, maybe a few wire swaps to cps. Anyone done this before.
Also will a 4.0 ecu run a 4.6 ? Again I can’t see why not as only stroked, same size bores ect.
If you can mod the CPS mount on the Thor block to take a GEMS sensor, then it should just be a case of bolting all the GEMS peripherals on (front cover, knock detectors etc, ). It's only the CPS type and position that differs between the two. As the two ECUs handle the CPS signals slightly differently (different induced voltages etc), probably best to stick with the GEMS sensor.
You've no doubt extracted the CPS stuff from RAVE, but if you haven't:
GEMS
The output signal from the CKP sensor is obtained from the magnetic path being made and broken as the reluctor ring teeth pass the sensor tip. The reluctor ring has 35 teeth and one missing tooth spaced at 10°intervals. The missing tooth is positioned at 20°after TDC.
Thor
The tip of the CKP sensor protrudes through an aperture in the engine block rear flange, adjacent to
the outer circumference of the flywheel. A 60-tooth reluctor ring is included on the flywheel which
provides the reference signal to the crankshaft position sensor.
The reluctor ring teeth are spaced at 6 degree intervals and are 3 degreeswide. Two of the reluctor ring teeth are
removed, to provide a reference mark which indicates when the crankshaft is at 60°BTDC for number 1 cylinder. The remaining 58 teeth cause an AC voltage to be induced in the sensor pick-up, with the
amplitude of the signal increasing with rising engine speed. The voltage generated is an analogue signal capable of peak amplitude voltages of up to 300V.
The distance of the tip from the top of the reluctor ring teeth is important as the amplitude of the detected signal will be reduced in proportion to an increase in the gap between the sensor tip and the top of the reluctor ring teeth. If the air gap becomes too wide, the CKP signal could become too weak and possible misfires could occur. Spacers are included in the CKP sensor kit which are used to ensure the correct gap between the sensor tip and reluctor ring teeth.
The ECM uses the falling edge of the signal waveform as its reference for each reluctor ring tooth.
Consequently, if the input signal wire and reference ground wire are inadvertently reversed, the ECM will react by providing a 3 degree advance in ignition timing.
GEMS information for the Nano says that:
Engine: Used to select between usages of the GEMS ECU with either a 4.0 or 4.6 litre engine. Unhelpfully it doesn't say whether that value can be written in with the Nano or is coded. I'd like to think it can be selected but have never tried. If you get that far, I'll plug my Nano into the GEMS and have a look.
Isn't the cam sprocket different too?
Gilbertd wrote:
Isn't the cam sprocket different too?
Tis- will need the GEMS sprocket to go with the GEMS cam sensor.
You can change the engine size selected in the GEMS ECU - I changed from a 4.6 to a 4.0 in my first P38. It may take saving twice though to stick.
Jeez, think I’ll keep an eye out for a gems
Maybe I'm getting this all wrong but for me Chris wants another shortblock to replace his GEMS.
No problem what block you find, if it's a THOR you keep the (GEMS) flywheel + spacer, crank sensor + mountingplate (a little spotwelding), knocksensors, cam sprocket + sensor, maybe oilpan and frontcover.
I've done it the other way around, found a GEMS block to suit my THOR.
And yes it still hurts that I had to sell.
Tony.
I have numerous Thor block, but the car I’m working on is a gems, I don’t want to be messing about welding brackets ect, though it might of worked, I was wrong though, typical LR.
no10chris wrote:
I’ve got a gems that I’ve done the heads on, it ticks over for hours ok, but directly it's out under load it will overheat, I’ve changed rad, stat, repaired leaking Orings and pipes, checked water pump, flushed the system twice, driving me nuts. I’m thinking there’s a problem with the block.
I’m wondering if I can put a Thor short engine with flywheel and cps , I can’t see why not, maybe a few wire swaps to cps. Anyone done this before.
Also will a 4.0 ecu run a 4.6 ? Again I can’t see why not as only stroked, same size bores ect.
Not done this, but have had the overheating under load problem here. Started off swapping the radiator - this didn't fix it, swapped the thermostat (this actually made the problem worse as when we removed my thermostat there wasn't a themostat inside the housing, just a loose bit of the metalwork floating about inside) Was in the process of swapping the viscous fan as the next step when we discovered with the new themostat that the radiator wasn't actually getting hot (or even particularly warm) until the engine was switched off - at which point you could literally feel the temp rising inside it.
We eventually found that in the process of swapping bits that the one thing we hadn't realised was the original thermostat (and therefore the new one) had been connected with the top two hoses swapped over. If you look in Rave there is a cooling system diagram that shows the actual flow round the system, this was what we noticed when tracing it around appeared to be wrong. Swapped the two top hoses over and its been fine since.
This was a Disco 2 in this case with a Thor, but AFAIK the thermostat is the same on both or at least similar enough to allow it to happen. Was down to the previous owner (the same one who couldn't fit spark plugs or the oil pressure sensor switch either!) as when i first got it, the heater was stone cold when driving it (would be ok sat idling, but any speed meant no heat at all). I suspect he had got them messed about at some point previously and ended up gutting the stat to try and stop the overheating.
Just checked the parts list, doesn't look like you can do that on yours as far as i can tell, as the thermostat hoses are a different size to each other.
Thanks Brian, I’ll have a look, some of the hoses are the same size on top
Biggest clue was the rad not getting hot, even though the gauge showed it clearly should have been in my case. (it was cool enough you could touch it until the engine was stopped)