Ok, this thing drives me nuts. "The thing" is power gain (substantial, up to 20Kwt and 140Nm to the wheels) once the fuel temp gets to 40-50 range and/or car was sitting idling or being shut off for 10-15 minutes. I've been stuck in my tuning to 70mg/stroke and 1.4 bar boost for three month now because of this strange issue. Here are examples of when it happens.
I use GtechPro to measure hp and torque at the wheels in my tuning. What I do is making 20-30 pulls in second gear at the same location. The OEM map typically puts down 55-60 KWt and 200Nm which is pretty close to the Superflow dyno results. 70mg/1.4bar boost map puts down 110-115Kwt and 300Nm. As I go along with my pulls the fuel temp is rising and then I hit the "magic" band 40-50C in fuel temp the map puts down 130-135Kwt and 420-440Nm. Once the temps approach 60C the power starts dropping slightly. The OEM map does the same, but to the lesser degree - 70KWt and 240-260Nm. The difference is real and very well pronounced. Another typical situation - you park the rig for 10-15 minutes and go run some errands. Come back, drive it and it's a beast for 5 minutes and then it goes to "tamed beast" mode - 3rd gear feels like the 2nd and 2nd like the 1st. The same was the case then the car was completely stock. I asked around and most people had no idea, but when notified reported back that this is indeed the case with their Disco's Td5 as well.
I have no viscous fan, idiotic LR fuel filter has been replaced with reworked Cummins head/filter. No clutch slippage either since I am running 10.5" clutch worth of 800Nm. Pump is new VDO and flow capabilities have been checked in real time under full load. The only thing that I can think of is an air entrainment in diesel.
Injector seals are new. All live pressure fuel tests under load done and I monitor fuel pressure in real time. Any ideas or leads would be greatly appreciated. Ready to go with 90mg and kick 300hp arse but what's the point of tuning motor that can not behave evenly?
On a separate note. LR states that the first stage pump flows 30l/h at 0.5 bar (some literature states at 0.75 bar). BS. First stage (lift pump) VDO flows at least 50l/h at 1 bar. That is the experimental result.
Stepan
YarnMaster
Hi, that new cummins filter is connected like the original one wilt all the ports retained? i mean does it have the air bleed valve in it like the other? ... and what about the wastegate? , the pipework to/from the modulator and the valve are OK?Originally Posted by td5howard
Discovery Td5 (2000), manual, tuned
Filter base has to be reworked - drilled and threaded. I used this one to begin with 4944718. 5 micron filter/separator is Donaldson P550899. You need to make threaded adapter to fit LR water sensor. Otherwise fuel lines and water sensor fit like a glove. I also installed 0.2bar check valve and 1.5mm diameter orifice in return line. The original assembly is a work of british art. Filter is small and clean flows only 200l/h, while second stage pump flows 180l/h. There is no air bleeding - this little plastic POS lets air through only when wet and the reverse filter flow assures that the input to the second stage pump gets air first. Hence all this nightmarish problems with air in the fuel system. If you want to keep old filter/head then through away this useless "bleeding valve" and instead put check valve and 1.5mm orifice in return line. No more bleeding issues forever. I never bleed the system after doing work on fuel lines. :-) But then you'll never know then injector seals go south ....
Boost cut set to 2.27 bar and boost spikes to 1.6bar only when spinning vnt up. It's not an issue.
The problem has been solved. It turned out to be a weird play between boost actuator spring rating and WGM map settings on my VNT. Since MAF is a completely useless device on Td5 one has to rely on EMP vs. boost reading when tuning VNT to maximize the air flow - to tight and you get high boost-high EMP and no air flow, to loose and you get low boost-low EMP and now air flow. It's especially challenging to tune under load, but I managed and past 1750 rpm the thing runs 1.5 bar of boost in reverse condition, meaning EMP is less then boost. :-) Power delivery is very consistent now with run to run variations of no more then 5%. Now comes the 90mg shot and final kiss good by to 300bhp mark. :-) It should not be "bespoke" 300bhp with 200rwhp. Hoping for the real world 300bhp with 260rwhp. I am pretty certain that there are unknown to human race limiters in the Lucas product so I'll begging Paul for mercy. ;-)
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