Hi, I am tuning an XK engine which I have converted to EFI and I am looking for some help with timing curves. I built this engine with 10:1 compression pistons and a high lift cam. I am up and running pretty well and have used the closed loop Lambda features to better dial in my fuel table. With that said my timing tables are spitball at best. I assume that timing curves from performance tuned E-types would translate. I am using MAP vs. engine speed but I assume other parameters would translate. Looking for a performance timing curve that someone would be willing to share.
Cheers,
Kurt
If I were you, I would call Bill Terry and offer to pay him to consult on your request. Otherwise, I think you are just going to collect more spitballs. If not that, I would get it on a rolling road with an electronic knock sensor and do your due dilagence. It will be highly dependent on what you are using for fuel.
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Head over to the UK e type forum and look at the EDIS / Megajolt thread. It has stock S1 4.2 / 3.8 timing curves on 3D maps with MAP sensor load. Then there are a few curves from guys with modified motors who dyne tuned their EDIS setups. That should be a good basis to start from.
Oh boy, 10 to 1 with hot cam will surely need a custom curve based on dyno testing or a similar engine combo someone has already sorted out, as referenced by Theo. High lift also means more duration, I assume? Generally, a more efficient combustion process would require somewhat less advance than a stock engine at any given RPM and calculating the dynamic C/R at various RPM may be helpful. The idle dynamic C/R will be less than a stock engine and may require more initial advance to maintain a stable idle, which in and of itself would call for a flatter curve to avoid too much advance higher up the RPM scale. For reference, many warmed-up, high performance American V8s will use 16 or 18 initial advance, reaching about 36 or 38 total in the upper range.
Lee140FHC, That is the neatest thing about EFI you can tune everything and dial it all in. You don’t have to accept compromises. Access to a dyno would be great but I have been able to get things up and running by driving on the road and reviewing log files. Making adjustments is super easy once you learn the software and there is lots of support out there.
So you have oxy sensors?
Sensor, I mounted one Bosch LSU 4.9 Wideband sensor in the y-pipe. Sorry I don’t have a picture to share of the placement. But it tucks away discretely. I am using a modified SIII FI manifold, and running everything with a LINK ECU.
Kurt, some pictures are welcome. ECM curve 683, 2000rpm 11 degrees, 850rpm 8 degrees, 450rpm 1.25 degrees, 325rpm no advance is standaard 3.8L and 4.2L .
But this engine is to powerfull.
Frank.
Terry Sturgeon has built some modified (cams& ported), as has Dick Maury at Coventry West. Both post on JL frequently. PM them, they may have some advise.
Dick built the jcna slalom record holder.
Kurt what ignition system are you running. Is it an EDIS?
Terry,
I am using a LINK ECU to run everything. The G4+ software allows all the tuning. I imagine the table values would be comparable. Do you run an EDIS set up? Do you have knock sensors? That is one part of the equation I haven’t figured out yet.
Hi Kurt. I have a 4.7 litre engine in my car, big intake valves, ported, with Terry’s WAD cams which may be a bit too aggressive for a street car. The engine has 9:1 pistons and I run on SU’s and occasionally Webers. Ignition is an EDIS unit. Neither likes the cams at idle much, particularly the SU"s. I raced an E type for 15 years with a much more modified engine that produced 375 hp on the dyno but it ran on 12.25:1 pistons and 110 plus octane fuel, so I straddle your engine. I have run a 10.5:1 engine in the race car but again it was on a 50/50 mixture or premium and race fuel, so I’m not sure I can be of significant help. I don’t use an knock sensor on the 4.7l motor but I had one on the race car.
As you undoubtedly know hemi engines have a big combustion chamber which requires a lot of ignition advance to get the fuel burned at the right time, but unfortunately are very prone to detonation - because of the big combustion chamber. IME detonation occurs primarily at mid range - 2000 - 3000 rpm, under heavy load - say going up a hill, so your timing in the range needs to be a bit subdued.
The picture below is what I have set the EDIS system for the 4.7l engine. Going toward the bottom of the graph is decreasing vacuum. I set timing at zero degrees at cranking speed (500 rpm) for starting, it then rises to 21 degrees btdc at 700 then drops to 15 degrees at 1100. The purpose of this is to control idle speed - the cams cause the engine to hunt when at idle, the timing tries to correct that and hold the idle speed at 700 rpm. The engine likes a lot of advance when idling - it’s much smoother. The timing is cautious at mid range - maybe too cautious, then t go up to 41 degrees. There is a lot of power to be made with ignition advance - I’ve run one modified engine (9:1 pistons) up to 45 degrees total)
Hopefully this is helpful to you
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Terry,
Thank you for sharing your ignition table. After comparing what I have worked out (cloned from a BMW E36 engine) and tweaking from there It is very comparable. Until I get the fuel map sorted my timing is a bit more conservative at the high end, but I am encouraged to see I get get a bit more greedy!
Terry, I sent you a PM with some follow up questions, have you by chance had a moment to view it? In particular I am curious about fitting knock sensors on the XK engine. What did you use, where did you place it/them etc. Has anyone else out there fitted knock sensors to their XK engine?
Kurt I used a MSD 8964 knock sensor. This was a stand alone unit. I don’t believe they are available anymore - I think Holly has bought MSD out. You can find pictures on the web for this and as well mounting instructions: the latter at https://www.jegs.com/installationinstructions/100/121/121-8964.pdf
I don’t know anybody else that used then. I damaged an engine with detonation once and am a bit touchy about the subject because of that. The sensor was mounted by drilling and tapping the screw-off plug for a block heater found on the side of the block.
There are instructions for making a knock sensor on line. This one intrigues me: https://www.nicoclub.com/archives/diy-knock-detection.html
Just need to find a Whisper 2000
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I would think all you would need to do to make a DIY knock sensor is to buy a musical instrument pick up, Mount it on the cylinder head and connect it to your smart phone. Then run an FFT audio spectrum app. Then look at the spectral response and I would think knocking would show up as a big peak at a high frequency. Sorry if this is electrical engineering speak…
I am always amazed at the expertise that shows up on this forum.
Cheers,
LLynn
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Megatriple dittos!!!