Engine hunts when hot
Discussion
blitzracing said:
I cant see it in your loom, its not on all looms, as in the USA looms they dont want people changing maps, so the resistor is missing. It looks like this if you can find it, but as long as you are showing map 5 thats fine.
Im surprised the difference between 4 and 4.5 would kill the engine that badly, but I guess the 4.5 has much improved higher RPM breathing over the 4 ltr when it needs more fuel.
Maps here if you want to blow another chip or drop me a mail if you want me to do one for you.
http://www.remap-14cux.uk/bins/
Ok It says Tune:- R2967 as I have but I notice some thing else about altering the voltage on the AFM by turning a screw. When cleaning the AFM I turned that screw so have I screwed up the AFM literary?Im surprised the difference between 4 and 4.5 would kill the engine that badly, but I guess the 4.5 has much improved higher RPM breathing over the 4 ltr when it needs more fuel.
Maps here if you want to blow another chip or drop me a mail if you want me to do one for you.
http://www.remap-14cux.uk/bins/
The picture should be of the AFM with an 7/32 allen key sticking out the side.
TVR Griffith 400 & 400HC Precat (R2422)
TVR Griffith 430 & 430BV Precat (R2422)
TVR Chimaera 400 CAT (R2967)
TVR Chimaera 430BV CAT (R2967)
TVR Chimaera 450 CAT (R2967)
TVR Griffith 500 (1995on) (R2967)
RoverGauge shows the CO trim voltage for non cat vehicles in real time but you first have to start and stall the engine before RoverGauge displays any adjustment of the CO trim screw. Please make a note of your CO trim voltage before making any adjustments so you can revert back if required.
The CO trim voltage & AFR table on the left was created by turning the CO Trim screw in half turn increments clockwise which increases the CO trim voltage and fuel. For all Precats 13.5 AFR is best for smoothness and reduces shunting.
CO Trim for Precat vehicles
Precat owners wishing to change firmware revision may have to adjust the CO trim screw on the AFM with a 7/32 Allen Key. The Co Trim voltage should 2.3 volts for a 4.3 running it’s original factory ECU and 1.4 volts when running TVR’s later code R2967 or Land Rovers final code R3652.
R2967 & R3652 idle AFR (4.3L)
Clockwise increases volts & fuel
Co Trim Volts AFR
0.04 Lowest 16.5
0.55 15.7
0.8 14.8
1.05 14.3
1.25 14.1
1.42 13.5
1.6 13.3
1.75 13.1
1.92 13.0
2.05 12.8
2.20 12.7
2.35 12.5
2.50 (8 turns) 12.4
From your screen captures it appears your car's ECU thinks it should be fuelling for a 4 litre TVR Chimaera rather than a 4.5 litre, and this is the root cause of your problem!
Your current 4.0 litre EPROM, where a number of parameters for making fuelling calculations are defined, includes:
- A Fuel Map Multiplier value of Hex $56CC, whereas a TVR 4.5 litre tune uses $6978 (a higher value).
- A Row Scaler AFM value of $B9 instead of $91. This also impacts on fuelling values.
- An upper RPM Limit of 5800 rpm instead of 6188 rpm, and probably a whole set of different fuel map values entirely.
So I'd try putting in a TVR Chimaera 4.5 EPROM as a possible solution. Steve's Remap site has a number of good options for a TVR 4.5.
Your current 4.0 litre EPROM, where a number of parameters for making fuelling calculations are defined, includes:
- A Fuel Map Multiplier value of Hex $56CC, whereas a TVR 4.5 litre tune uses $6978 (a higher value).
- A Row Scaler AFM value of $B9 instead of $91. This also impacts on fuelling values.
- An upper RPM Limit of 5800 rpm instead of 6188 rpm, and probably a whole set of different fuel map values entirely.
So I'd try putting in a TVR Chimaera 4.5 EPROM as a possible solution. Steve's Remap site has a number of good options for a TVR 4.5.
davep said:
spitfire4v8 said:
I did suggest this just over a month ago .. you can give the advice Dave but it's pot luck whether anyone actually acts on it 
Frustrating isn't it! Horse to water and all that ...Hopefully there will be another TVR running to its full potential at the end of it.
LenChim said:
.....You do not normally go around at 5400+ rpm on your Sunday run out.
Len, to help highlight the many differences between the 400 and 450 fuelling setups here are code listings of fuel maps captured from the respective disassembled BIN files:TVR Chimaera 400:
TVR Chimaera 450:
It is the area to the left that is displayed in the fuel map matrix within RoverGauge.
The 450 map rev range values (column headers) also differ markedly for each column since the end point is extended out to 6188 rpm; it is not a simple case of increasing the 16th column from 5800 to 6188 rpm.
Bear in mind it is these cell values that form the raw injector value inputs for the many fuelling calculations that follow, wherein the fm5_factor (Multiplier) is only applied once compensation for time, temperature, throttle and Lambda has been introduced.
HTH
Edited by davep on Monday 20th January 10:45
I've grabbed one of Steve Sprints 450 maps with later base code, extended fuelling and a few other tweaks. I've heard nothing but good for Steve work, and its in the post box now. Remove the ECU and open it and just swap the chip over, by gently prising the old chip out with a small screw driver and pushing the new one in its place. There is an alignment slot in the chip at one end, so make sure its around the right way. Ideally you should have anti-static mat, as this is old technology that can fail if it gets a static charge. Having said that, these cold damp days of winter there is not much change of static build up, but if you have access to a grounded metal surface (like a sink drainer) its a good place to do the work. General precautions are keep your finders off the chip legs, hold it end to end, and carefully check no pins are bent under the chip body when you press it into the socket. When you plug the ECU back in, turn on the ignition, (dont start) and listen for the fuel pump. It should do the normal couple of second run, then stop. This will prove the ECU microcode is fine and all is well. You can then start the car and get it warm. If the pump does not cycle, check the chip pins, don't try and run the engine. Don't forget it will need to re-learn the long term fuel trim, so take the car for a run if the pump cycle is ok, then let it idle for 2.5 mins to reset the trim. If you miss this out, you may have bad shunting, although it should run clear above 3400 rpm even if the trim is not set.
Edited by blitzracing on Sunday 19th January 17:44
LenChim said:
Many thanks.
OK I have put in the new chip, got it warm and let it tick over above 90C so all reset. Took it out for a run goes very well up to 5400 ish rev's then hit a wall, looking at the out put from the lambada's the voltage drops to zero after about 3300. So whats new? Found I had a vacuum in the petrol tank so left the cap of, no difference. I am going to swap out the coil and see if I can blag an AFM from some one after that I am devoid of ideas. Does any one know of some one with a rolling road in west Sussex that is not going to cost me an arm and a leg? I will try and get some screen shots of the car under power if it ever stop raining.The Rev limit should be about 6200. I've yet to hit it on a TVR map, it makes my eyes water thinking of those pushrods and valves trying to keep up. The landrover limit was around 5400, but it's a serious brick wall when you hit it, quite terrifying if you are trying to overtake something in third, and it simply cuts the injectors. None of this accounts for the drop in lambda voltage so early on.
blitzracing said:
None of this accounts for the drop in lambda voltage so early on.
true .. there is a weakening of the mapping as the revs rise, not so much on full throttle but the part throttle mapping goes very weak as revs rise. It's one of the key areas to address when remapping to make the car feel more urgent on part throttle acceleration.
blitzracing said:
The Rev limit should be about 6200. I've yet to hit it on a TVR map, it makes my eyes water thinking of those pushrods and valves trying to keep up. The landrover limit was around 5400, but it's a serious brick wall when you hit it, quite terrifying if you are trying to overtake something in third, and it simply cuts the injectors. None of this accounts for the drop in lambda voltage so early on.
I have hit it a few times on track days, generally in second or third when overtaking, but also when I had more than enough to think about keeping up with Phazed at Snetterton while approaching the first corner a bit fast and dealing with traffic coming out of the pits straight across in front of me without looking as I was doing 125 in 4th..........enough to think about without having to consider changing gear as well. You get a sudden cough, a lurch and a total cut in power.
Quick upshift, change of undercrackers, and you're away again.
They reckon women can multi-task.
I have yet to meet one who can do three things at once, especially when two of them are map-reading and parking.
Nuff said.
blitzracing said:
The Rev limit should be about 6200. I've yet to hit it on a TVR map, it makes my eyes water thinking of those pushrods and valves trying to keep up. The landrover limit was around 5400, but it's a serious brick wall when you hit it, quite terrifying if you are trying to overtake something in third, and it simply cuts the injectors. None of this accounts for the drop in lambda voltage so early on.
Ok, I changed the HT coil gave it a run and it will rev over 6000 rpm as you said it sounds very excited so it would seem that the coil was breaking down despite passing all the resistance tests. The lambada voltage still drops to zero but what the hell. I could only glance at the matrix but the black square was over to the right on the screen so it would seem to be ok, I honestly cannot say if it was near the top or the bottom I think?? it was about mid way. If I get a mad passenger at some time in the future I will get a better reading from them.Many thanks for your knowledge and help over the past few months. Len
The problem you have with resistance checks on the coil is all they do is tell you if the copper wire is OK. Under hard load, the spark becomes much harder to ignite, so the coil has to keep the secondary voltages rising until the arc starts. Lets say under light load you need 10KV to start the spark, that might rise to 15kv under full throttle and this could be enough to start an internal short between the windings you dont see at DC. Add to this the coils dwell period will drop as the RPM rises, and effectively you have less magnetic field available to generate a decent secondary voltage, so you cant afford to loose any available power held in the coil at all, especially with 8 hungry plugs to feed every 2 rotations from just one coil.
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