Discussion
I've done an improvised leak down test. Using compressor charged to around 80psi, and a modified Tyre inflator thingy with adapter down into spark plug. All other plugs out and engine cold (I know it's supposed to be done hot but this evening is too warm)
Tested by rotating engine, holding on tight to torque wrench on crank and carefully finding the sealed point by pulsing air, rotating a bit etc. Once found cyl 1 5 and 6 (have checked those so far) all behave the same...at around 60psi into cylinder then release pressure I can get to point with no obvious audible leaks and can just about hang on to wrench! Leaks down to zero in around 5 secs. Seems to mainly pressurize the sump because after that small rotations cause audible leaks from any of the other cylinders.
I reckon that's an OK test...unless someone knows better...please.
Tested by rotating engine, holding on tight to torque wrench on crank and carefully finding the sealed point by pulsing air, rotating a bit etc. Once found cyl 1 5 and 6 (have checked those so far) all behave the same...at around 60psi into cylinder then release pressure I can get to point with no obvious audible leaks and can just about hang on to wrench! Leaks down to zero in around 5 secs. Seems to mainly pressurize the sump because after that small rotations cause audible leaks from any of the other cylinders.
I reckon that's an OK test...unless someone knows better...please.
Don't know the answer to your problem but some ideas might help:
When you floor the pedal, you should get a momentarily lean condition and the ECU tries to correct with additional fuel but only to a certain limit. I think that lean condition and the fuel limiter allows you to accelerate without interruptions. Personally I think it is over fueling causing the power loss.
I don't know about the MBE ECU, but some ECUs do not rely on Lambda if throttle is over 50% or rpm are over 4000 and only the fuel map is used.
I would reset the fuel map from the Software and see if the behavior stays
Peter
When you floor the pedal, you should get a momentarily lean condition and the ECU tries to correct with additional fuel but only to a certain limit. I think that lean condition and the fuel limiter allows you to accelerate without interruptions. Personally I think it is over fueling causing the power loss.
I don't know about the MBE ECU, but some ECUs do not rely on Lambda if throttle is over 50% or rpm are over 4000 and only the fuel map is used.
I would reset the fuel map from the Software and see if the behavior stays
Peter
Appreciate all the feedback guys. I have reset the adaptives etc, also tried running with no lambdas. All to no avail.
I have have also disassembled the ecu and all looks A OK. Have buzzed out direct from power transistors on ecu pcb to the coil pack connections and to injectors ...all nice low R.
Think I'll check the valve clearances one more time when properly hot.
I have a fuel pressure tester on the way and I'm also going to try and use one of the colortune thingys to see if there is evidence of mixture issues.
After that it's oscilloscope on each ht lead.
I have have also disassembled the ecu and all looks A OK. Have buzzed out direct from power transistors on ecu pcb to the coil pack connections and to injectors ...all nice low R.
Think I'll check the valve clearances one more time when properly hot.
I have a fuel pressure tester on the way and I'm also going to try and use one of the colortune thingys to see if there is evidence of mixture issues.
After that it's oscilloscope on each ht lead.
No change. I believe that pipe basically does nothing because the vacuum in the air box is never going to be enough to activate it. You'd need the suck from the engine side of the butterfly in the throttle body imo. Anyway good suggestion.
I also confirmed that map sensor is OK (which of course also doesn't see much change in the air box for the same reason)
I also confirmed that map sensor is OK (which of course also doesn't see much change in the air box for the same reason)
The S6 in my Cerb does not have a vacuum pipe and I'm surprised it ends in the airbox, that seems pretty useless ?
The goal is actually to compensate for the pressure difference, so the injectors have always a difference of 3 bar between rail and output. A while ago I made a measurement of AFR change depending on fuel pressure. A drop of 3.5 bar to 2.5 gave only a surprisingly low AFR change from 14.0 to 14.7 but that was on 4 cylinder engine with 330ccm injectors. What I'm trying to say is, that a "bad" vacuum tube should probably not have such an impact as your are experiencing.
So whats left to check or to be replaced ? Fuel pump, Filter, Electrical Ground and Power connection of ECU ? (Engine ground is certainly ok, otherwise you would not be able to start)
The goal is actually to compensate for the pressure difference, so the injectors have always a difference of 3 bar between rail and output. A while ago I made a measurement of AFR change depending on fuel pressure. A drop of 3.5 bar to 2.5 gave only a surprisingly low AFR change from 14.0 to 14.7 but that was on 4 cylinder engine with 330ccm injectors. What I'm trying to say is, that a "bad" vacuum tube should probably not have such an impact as your are experiencing.
So whats left to check or to be replaced ? Fuel pump, Filter, Electrical Ground and Power connection of ECU ? (Engine ground is certainly ok, otherwise you would not be able to start)
In theory the vacuum pipe that goes from the fuel pressure regulator to the airbox should cut off fuel pressure when there is an airblock.
One thing to check is the grounding point of the ECU that goes to the bell housing. Should be near the starter fixed to one of the allen screws of bell housing.
One thing to check is the grounding point of the ECU that goes to the bell housing. Should be near the starter fixed to one of the allen screws of bell housing.
Pete,
If you run this and leave it 24 hours and try to read the adaptive or any other recorded data what do you find? Is it storing information or losing it? When I bought mine the Novram thing was up the wall and it wouldn’t run or do any thing sensible, unless you got rough with it. The transformation was incredible, then I took the engine out and rebuilt it..... blah blah but the symptoms made no sense to me. I know you have a new one but there is old stock out there being sold.
How’s the hunt for a donor ECU? I have one but it’s a bit of a slap down to you, although I might be near you Saturday. PM me or text you still have my number and we will see if we can sort something
J
If you run this and leave it 24 hours and try to read the adaptive or any other recorded data what do you find? Is it storing information or losing it? When I bought mine the Novram thing was up the wall and it wouldn’t run or do any thing sensible, unless you got rough with it. The transformation was incredible, then I took the engine out and rebuilt it..... blah blah but the symptoms made no sense to me. I know you have a new one but there is old stock out there being sold.
How’s the hunt for a donor ECU? I have one but it’s a bit of a slap down to you, although I might be near you Saturday. PM me or text you still have my number and we will see if we can sort something
J
Just to pick this thread up again vs. the ECU one...
"I wonder if the fuel pressure regulator is playing up. Think about the full throttle and vacuum while the engine is running. I have experienced a blocked, partially, filter ( not in a TVR) and you will get a spot of normal running then run out of puff while the fuel passes the filter and builds pressure in the line. If this isn’t closing when it should it would be surely be dumping fuel? Still don’t get its function and purpose though. Hook the hose off then it is “blind” to the throttle position
Worth a shot
J "
@John: Agree...I'm wondering the same
Just for ref here are 2 waveforms captured on the coil primaries...all 3 coil drives doing the same kind of s***. Everything ive found implies that it's a lean misfire on all cylinders at random
"OK" fire
"Horrible" misfire (assumed)
"I wonder if the fuel pressure regulator is playing up. Think about the full throttle and vacuum while the engine is running. I have experienced a blocked, partially, filter ( not in a TVR) and you will get a spot of normal running then run out of puff while the fuel passes the filter and builds pressure in the line. If this isn’t closing when it should it would be surely be dumping fuel? Still don’t get its function and purpose though. Hook the hose off then it is “blind” to the throttle position
Worth a shot
J "
@John: Agree...I'm wondering the same
Just for ref here are 2 waveforms captured on the coil primaries...all 3 coil drives doing the same kind of s***. Everything ive found implies that it's a lean misfire on all cylinders at random
"OK" fire
"Horrible" misfire (assumed)
Interesting. I might scope my Canems ECU and see how that looks. I'm getting really fed up with mine not running correctly. Its unreliable - some days are better than others. I'm not convinced some after market ECUs are designed correctly. Lets face it, the Canems ECU is housed in a plastic box so its open to all sorts of interference.
Finally found it after lots of experiments and some luck.
I have throttle body spindles linked by shaft couplers rather balance arms. Long story short...the coupler between 4 and 5 would slip slightly but only when hot! And yes, I had poked and wiggled all the butterflies very early on in the process to make sure they weren't loose...of course that showed nothing in the garage but out on the road butterflies 5 and 6 must have ended up slightly too closed under some random conditions making those cylinders run horribly but of course nothing much to hear up the engine end to give the game away (apart from the horrible flat shaky misfire). If it had gone lean it would have been popping and chuffing in an obvious way. I only found it because it finally got sooo bad that it was barely drivable and only then did I notice the problem once back in the garage with the airbox off.
So after a long journey and quite a few bits replaced it's back to normal. Thanks for all the suggestions.
I have throttle body spindles linked by shaft couplers rather balance arms. Long story short...the coupler between 4 and 5 would slip slightly but only when hot! And yes, I had poked and wiggled all the butterflies very early on in the process to make sure they weren't loose...of course that showed nothing in the garage but out on the road butterflies 5 and 6 must have ended up slightly too closed under some random conditions making those cylinders run horribly but of course nothing much to hear up the engine end to give the game away (apart from the horrible flat shaky misfire). If it had gone lean it would have been popping and chuffing in an obvious way. I only found it because it finally got sooo bad that it was barely drivable and only then did I notice the problem once back in the garage with the airbox off.
So after a long journey and quite a few bits replaced it's back to normal. Thanks for all the suggestions.
PetrolHeadPete said:
Finally found it after lots of experiments and some luck.
I have throttle body spindles linked by shaft couplers rather balance arms. Long story short...the coupler between 4 and 5 would slip slightly but only when hot! And yes, I had poked and wiggled all the butterflies very early on in the process to make sure they weren't loose...of course that showed nothing in the garage but out on the road butterflies 5 and 6 must have ended up slightly too closed under some random conditions making those cylinders run horribly but of course nothing much to hear up the engine end to give the game away (apart from the horrible flat shaky misfire). If it had gone lean it would have been popping and chuffing in an obvious way. I only found it because it finally got sooo bad that it was barely drivable and only then did I notice the problem once back in the garage with the airbox off.
So after a long journey and quite a few bits replaced it's back to normal. Thanks for all the suggestions.
I’m glad you got it sorted, there’s nothing more frustrating than trying to pin down a problem like this. I also had a misfire recently on my newly rebuilt engine with all new coil pack HT leads etc... I took it to a TVR specialist who spent a whole day trying to track down the problem. Coil pack, plugs and ECU were all changed, throttle bodies balanced, air-box adjusted, it made no difference. Finally the HT leads were changed even though the garage said they couldn’t think that they could be the problem as the leads were virtually brand new. Obviously it was the leads! I was just relieved that this fixed the problem as the garage was about to give up after relieving me of many readies!I have throttle body spindles linked by shaft couplers rather balance arms. Long story short...the coupler between 4 and 5 would slip slightly but only when hot! And yes, I had poked and wiggled all the butterflies very early on in the process to make sure they weren't loose...of course that showed nothing in the garage but out on the road butterflies 5 and 6 must have ended up slightly too closed under some random conditions making those cylinders run horribly but of course nothing much to hear up the engine end to give the game away (apart from the horrible flat shaky misfire). If it had gone lean it would have been popping and chuffing in an obvious way. I only found it because it finally got sooo bad that it was barely drivable and only then did I notice the problem once back in the garage with the airbox off.
So after a long journey and quite a few bits replaced it's back to normal. Thanks for all the suggestions.
As part of my swapathon I changed the fuel pump and filter. The old filter was an eye opener...very much harder to blow through than the new one even though it was well within its service period. Didn't make any difference to the fault of course but might effect running at full throttle I guess.
The other thing that becomes apparent when logging adaptives is that the feedback loop makes diagnosis very confusing! A mixture fault in one or more cylinders on a bank makes the remaining ones on that bank also start to misbehave
The other thing that becomes apparent when logging adaptives is that the feedback loop makes diagnosis very confusing! A mixture fault in one or more cylinders on a bank makes the remaining ones on that bank also start to misbehave
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