RV8 Pinking like a B*$**$&
Discussion
Sounds like a similar problem to mine (now cured). I spent all of the winter rebuilding the 3.5 EFI RV8 lump in my Land Rover toy (normal daily runner is a 03 Cooper S). After runing in I found bad pinking above 4K (yes, it was worse under load). Various settings of the timing made some difference but it still pinked.
To cut a long story short I traced the problem to the ignition amp module bolted to the Lucas 35DLM8 distributor.
1. Putting a scope on the input showed that the amp was not being triggered very well at 4K and above, even though the air gap was correct on the Hall effect switch.
2. Putting a scope on the amp output and giving the motor a good dose of the loud pedal showed up the fault.The ouput was ringing (an electronic term) above 4K. Ringing means that instead sending one good pulse to the coil, it was sending a series of pulses at a slowly dimishing level (like an echo). This meant that the cylinders were getting loads of sparks at the WRONG time and at various HT levels. If you think about it, its a classic senario for pinking !.....
Change the amp and hey presto - goes like s**t off a shovel and pulls cleanly right up to 6K.
The only down side is that even a motorway is narrow when you get into 3 digits with a LR90 trck cab !...
To cut a long story short I traced the problem to the ignition amp module bolted to the Lucas 35DLM8 distributor.
1. Putting a scope on the input showed that the amp was not being triggered very well at 4K and above, even though the air gap was correct on the Hall effect switch.
2. Putting a scope on the amp output and giving the motor a good dose of the loud pedal showed up the fault.The ouput was ringing (an electronic term) above 4K. Ringing means that instead sending one good pulse to the coil, it was sending a series of pulses at a slowly dimishing level (like an echo). This meant that the cylinders were getting loads of sparks at the WRONG time and at various HT levels. If you think about it, its a classic senario for pinking !.....
Change the amp and hey presto - goes like s**t off a shovel and pulls cleanly right up to 6K.
The only down side is that even a motorway is narrow when you get into 3 digits with a LR90 trck cab !...
Sounds like you've got a cure for my chevy V8 problem too.
See here www.pistonheads.com/gassing/topic.asp?t=41924&f=20&h=0
It was also pinking like a barsteward, but that was a minor problem compared to the hesitation I was getting. Not being able to get over 20mph at one stage was a little embarrasing
Cheers, new amp & coil (high performance offerings) are on order.
Paul
See here www.pistonheads.com/gassing/topic.asp?t=41924&f=20&h=0
It was also pinking like a barsteward, but that was a minor problem compared to the hesitation I was getting. Not being able to get over 20mph at one stage was a little embarrasing
Cheers, new amp & coil (high performance offerings) are on order.
Paul
I've got the same problem with my 1991 3.9EFi Range Rover, it pinks really badly above 2500rpm when under load. I started checking all the things listed in the fault finding section of the Haynes manual and everything was OK until I tested between battery +ve and coil -ve. The manual says I should get 0volts with ignition off , but I'm getting full battery voltage. What does this mean?
Any help appreciated
Andy
Any help appreciated
Andy
My 420 SEAC has the timing set correctly and all seems good with the engine but even with Super plus ULG on full load and above 4k rpm it pinks like a B.....
Any idea.
GB
Some of the SEACs were built with insane CR. It may need decoking or a different head gasket to lower the compression. Could be the timing isn't correct or that the incoming air temp is too high and not cold enough to prevent pinking.
Steve
www.tvrbooks.co.uk
the "ringing" thing sounds interesting .. but I'm struggling to work out how it would cause pinking since every successive echo is after the initial spark, hence after the initiation of the flame front, pinking is normally as a result of the cylinder pressure building too early rather than too late..
The frequency (quite fast and needed a good quality scope to see it - one beam on the output, the other on the input and triggered from the hall effect switch) of the ringing was hard to determine as it varied with engine speed AND load (scope trigger was also upset by the hall not triggering the module every time at high ish rpm), however, the ringing only occurred above 3900 rpm and heavy pinking always coincided with the ringing of the module. The more load that was applied, the worse it got. Changing the module (for the newer 3 pin type) has fixed the problem and I have returned the timing back to normal.
Jools - If you want the old module to play with, I could post it on to you.
Ian
Jools - If you want the old module to play with, I could post it on to you.
Ian
TaSmania said:
Steve, (SHPUB)
Do you know what the ignition timing should be for a 420 SEAC - it'd be a great halp to be absolutely sure it's okay. What if I run it on 100+ octane!!
GB
It's set dynamically. In my experience there is no static value that you can rely on as there is so much varience with these engines. If it pinks, you retard the ignition till it stops. If you change the fuel it can take a couple of tanks to ripple through. Also ambient temp plays a big big part as well.
TaSmania said:
Timing set to 28 Degrees at 4k and with Optimax it's just on the Detonation Boarder line. It was at 31deg before. I guess the performance will drop off a bit. I'll order some booster and advance the ignition again.
GB
Thats as i would expect, 28 is normally max for these high comp engines, i always found that the optimum for max power was around 28 so you shouldn't loose any bhp.
Tim
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