legend89chopped

This is the timing chart I came up with, and programmed into the SDS engine management system. I took the liberty of photoshopping in the MAP readings in inches of mercury and PSI for my fellow Americans.

This is not a 'perfect' timing chart, because I haven't tuned it on a dyno. But the engine runs well with this curve, and revs quicker than stock. I'm thinking it's pretty close.

IMPORTANT: The gray line across the middle is the BASE TIMING curve. It strictly relates to engine RPM only. With the SDS system, you program the BASE TIMING curve, then a LOAD TIMING curve that advances/retards according to manifold pressure/vacuum. I did NOT program any of the LOAD TIMING values below 19.19 inHg. (It uses the BASE TIMING setting only at these pressures) The reason being, you only see these pressures at idle, and since idle is already programmed at 15 deg. BTDC, no further advance is desired at these pressures. Note that the chart doesn't show any correction at these conditions (low RPM, high vacuum). So basically, if I took my values out of my computer and made a chart according to them, the bottom three rows would show the same as the gray row, the BASE TIMING curve.



Hopefully, this helps someone out there. I'm not messing with my timing anymore until I get to a dyno with some high test gas. Feel free to chime in if you see something seriously wrong with my chart, but like I said, it runs great on this curve.

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stock legend

haha i have no idea what that is or what it does.. what do the numbers stand for?

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--CAI with AEM dry flow filter--
------AEM bypass valve-------

Muffo

When your engine is running it advances the timing as the revs go up. the numbers represent how many degrees before tdc it fires at. down the bottom is the revs and up the left hand side is the manifold pressure. The higher the load on the motor and the higher the manifold pressure the less timing advance can be used. If that makes sence

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legend89chopped

Correct.

This chart is only useful to those who have stand-alone timing management or piggyback tuners.

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jago

not bad that at all.

i've got this sofar.

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1990 Rover 827Si (honda c27a1) -timming advanced (DIY), Decat(diy), 2.5" exhaust(diy), direct cold air feed(diy), EBC yellow stuff front pads, Lowered 1" on Pi springs, 16" speedline alloys, Recaro 1/2 leather seats front and rear, carbonfibre covered dashboard,
nitrous (223hp @ 5673 and 215lbs @ 4829 - 22oct 2007)

legend89chopped

Nice. Your spark table values are actually pretty close to stock. I figured mine with 98+ octane. Did you do the same, or were you going for stock values?

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jago

yeah i've kept them fairly close for now so i can make sure she runs fine, once i'm happy with how she's running at idle etc then i'll pop down to the rolling road and get her fully mapped then i should se the real gains in the system.

oh and i'm only running 99+ octain

i take you advanced to det and then backed off 2-4 degrees. if you did what have you used to listen for det? i'm thinking of where i can add the pair of knock sensors.

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1990 Rover 827Si (honda c27a1) -timming advanced (DIY), Decat(diy), 2.5" exhaust(diy), direct cold air feed(diy), EBC yellow stuff front pads, Lowered 1" on Pi springs, 16" speedline alloys, Recaro 1/2 leather seats front and rear, carbonfibre covered dashboard,
nitrous (223hp @ 5673 and 215lbs @ 4829 - 22oct 2007)

legend89chopped

I used my ears.

No, really, I didn't have any device for knock detection. I really just listened for it.

There are some protrusions that stick out of the top of the engine block, right next to the cylinder walls. I looks like a perfect place to drill and tap holes for knock sensors, if you still have clearance for the intake mani, that is. I THINK they are actually put there for knock sensors, but they scrapped them before production because of engine noise, and the sensors couldn't distinguish the engine noise from an actual 'knock'. The 2.7 does produce a good bit of low-frequency vibrations, that could be mistaken for knock. But this is only my theory. I didn't get the knock sensors for the SDS system, but they were available.

You may find that the 2.7 in the old '96 Accord V6 has the sensors, but I can't be sure. Also, I remember someone talking about the brass crank pulley producing less noise from the crank assy., but I can't remember if the Legend had the brass or the Accord. Either way, I found a brass one, and used it. It was actually harder to get my timing magnets into it, because of a smaller inner lip, but I trusted myself for once, and went for it. I recommend the brass pulley if your installing knock detection.

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jago

ok cool i'll be doing the same once i have her running on the ecu.

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1990 Rover 827Si (honda c27a1) -timming advanced (DIY), Decat(diy), 2.5" exhaust(diy), direct cold air feed(diy), EBC yellow stuff front pads, Lowered 1" on Pi springs, 16" speedline alloys, Recaro 1/2 leather seats front and rear, carbonfibre covered dashboard,
nitrous (223hp @ 5673 and 215lbs @ 4829 - 22oct 2007)

stock legend

dam thats way too advanced for me lol.. i know basically how the engine works.. the four strokes and all that but how do you advance the timing? thats what the stand alone ecu is for right? and also when the pressure is 0.00 is that tdc?

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--CAI with AEM dry flow filter--
------AEM bypass valve-------

Muffo

Yeh the stand alone ecu does this you have to plot it all yourself. and change it for the rev range and for other factors. when the pressure is 0 this is at idle. TDC is when your motor is not running and your number 1 cylindar is at its highest point

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legend89chopped

Sorry to call you out, but manifold pressure it at a high vacuum at idle (about 21-22 inHG). When pressure is 0, the throttle plate is wide open, allowing atmospheric pressure into the manifold.

Of course, this is all relative. It's not actually "0" psi at W.O.T., because atmospheric pressure is not actually 0. (A.P. is around 14.5 psi at sea level, and less psi the higher your altitude.) It's "0" psi GAUGE PRESSURE, which you shouldn't ever get confused with atmospheric pressure. When you fill your tires and check them with your gauge, that gauge reads "0" when it's not on the tire valve, but the actual "pressure" all around you is whatever atmospheric is at your altitude, around 13-14 psi. High accuracy digital gauges have to be calibrated every time you use them, due to slight changes in atmospheric pressure all the time.

Another thing that might help to understand this, is when you hear someone talk about what type of MAP sensor they have. There are 1 BAR, 2 BAR, 3 BAR.... MAP sensors. BAR is short for barometric pressure, just yet another unit of measuring pressure.
0 BAR = 0 psi gauge pressure = around 14.5 psi atmospheric
1 BAR = 14.5 psi gauge pressure = around 29 psi atmospheric
2 BAR = Nearly 29 psi gauge pressure = nearly 45 psi atmospheric

They use BAR for vacuum measurements also
-1 BAR = 29.54 inHG = -14.5 psi (which is about as close to a perfect vacuum as you can get here on Earth) Of course, there's no such thing as atmospheric vacuum.

So when you hear someone say they have a 3 BAR MAP sensor, they don't mean it reads nearly 45 psi, but it reads FROM -30inHG up to 30psi, so it SPANS 3 BAR levels.

So when you see a vacuum measurement on my chart, it is only relative to 0 as being gauge pressure, as a reference.

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stock legend

haha where did you learn all of this?

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--CAI with AEM dry flow filter--
------AEM bypass valve-------

Muffo

Sorry my bad i had my self confused for a minute i should have known that seen as idle is a point on your rpm so is referanced down the bottom

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legend89chopped

THIS is the simple stuff. I took some engineering courses at UT Knoxville, but never graduated.

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