Base timing

[dapinky]

All replies are in t'other thread

[BFG in the BRG]

Many thanks,

I seem to be sorted now - ish - one question leads to another and all that

Incase anyone is looking for the other thread - its under Engine - base timing.

[rip]

A chat with Geoff at Castle Combe got me wondering...

Since my 2¼" Piper was fitted, my Elan was running fine when the timing was done by ear (stubborn git wouldn't let me set it by strobe). It has been corrected since but now suffers from increased overrrun pops/splutters, sooty exhaust, overboosts more easily, feels like it has less power & does less mpg??? When I mentioned overrun to Geoff, his first reaction was "Base timing".
When set by ear, it was apparently 46 degrees BTDC & Elanscan detected no knock.

My question is this... Since changing the characteristics of the engine (Piper 'zaust, K & N filter & LGM intake pipes), should I need to compensate by adjusting base timing? (I remember reading somewhere that LGM found this necessary but can't remember what she changed it to).

I will get Elanscan out & have a play in the near future....but are all of us with bigger exhausts missing out?

[dapinky]

Rip,

I'm waiting for the answer to this one as well - suffice to say, with all the fidling I've been doing to get the emissions as low as possible for the MOT (today), i ended up with a base timing of 12 degrees - but I put it back to the 'book' figure this afternoon

Assuming my oil cooler is sorted for saturday, I'll do a variety of elanscan runs with switcher in different positions, and base timing in different locations, and see how it goes on track.

[rip]

I get the feeling that when mine was set 'correctly', it wasn't.

I went out last night armed with a stopwatch, 6mm allen key, duck tape & a pen.
First I marked the position of my CAS.
I then went out & did several runs, timing 30-70mph in 4th gear each time, making timing adjustments in between each run.
First time, this took 13.2 seconds. After 2 adjustments, this was down to 7.2 seconds. Any quicker & I would not have enough grip to cope with 2nd gear (& I have newish sticky Toyo Proxes too!).
I think I advanced the CAS about 4-5 degrees in all, which would be 8-10 degrees at the crank.
I'll get the stobe out later in the week to see what timing I've ended up with. I'll make a note of it because I like it regardless of whether it is 16degrees BTDC or not.

I wonder how much our engines differ (plugs, coil packs, ignition leads, skimmed heads, boost pressures, chargecooler efficiency etc) & how severely this affects optimum timing?

[max and andy]

I can't wait to find out what the final figure is. I would love to be able to stand at your shoulder and watch what you are doing and how you do it. Andy

[rip]

I can't wait to find out what the final figure is. I would love to be able to stand at your shoulder and watch what you are doing and how you do it. Andy

Not really a lot to see.
Anyway, I'm sure we'll meet before long. All I need is some tape & an Allen key. Stopwatch (wristwatch) & a pen are everyday items. Then it's just a bit of trial & error.

[rip]

I haven't got the timing light out yet. I'll probably do this at the weekend. I'm as curious as anyone to see where it ended up but I couldn't be bothered to whip off the wheel & plug cover & drag out my spare battery the other night.

I think the ECU uses the base timing as a starting point & works out dynamic timing from its pre-programmed map.

I was led to believe it advanced timing until knock is detected, then backs off slightly. Elanscan does not support this though. If it did, you should briefly see knock quite often no matter what the base timing is set to....but I don't. The only times I have seen it is when the timing was way advanced, then knock was detected every time boost was applied and corrected fairly quickly on each occasion.

[max and andy]

Whats a knock? Andy

[al]

Whats a knock? Andy

When the fuel-air mixture in the cylinder doesn't detonate properly, also called "pinking" because of the sound it makes.

[rip]

That sums it up very nicely, Al.
This wikipedia article goes into more detail about the mechanics of it.

[RayD]

I asked this question on a different thread, Iain suggested moving it to here ...

The alternative method I chose this time was to tweak it until it feels good, using a standard test (I chose 30-70 in 4th on a flat road). Now I know what it can do, I can perform this test from time to time. Now I know how long it should take, I can judge whether or not I need to fiddle or not.

Rip,

What did you find is the ideal timing?

Do you imagine the ECU only moves the timing a certain amount from where it's set, as opposed to setting it to suit the conditions?

In other words ... if you start at 16º and under certain conditions the ECU would adjust it to 40º ... do you think that by starting at 20º it would adjust it to 44º instead?

Ray

[rip]

......which I answered 5 posts above on this thread.

But after re-reading my post, I think I can answer it in a different way..

Yes I think the ECU does just use the base timing as a reference to adjust dynamic timing based on a preset value.

I had read that an ECU advances timing until it detects knock, then backs off slightly. If this were the case, setting the base timing would be overridden automatically, which Elanscan suggests is not the case. It is also not consistent with the findings of many on here who find that accurate base timing is essential for optimal performance.
So yes, it appears that if base timing is set to 16dbtc & is dynamically advanced to 40dbtc, then advancing the base timing by 4d will advance dynamic timing to 44dbtc under the same conditions, except that the ECU will back this off if knock is detected.

A question for you though Ray... How did you display a degree sign in your text

[RayD]

......which I answered 5 posts above on this thread.

A question for you though Ray... How did you display a degree sign in your text

Sorry about that Iain, It was the other thread I'd been reading.

The degree sign is from Microsoft Word 2007 > Insert > Symbols

[GeoffSmith]

Yes I think the ECU does just use the base timing as a reference to adjust dynamic timing based on a preset value.

Me too.

A question for you though Ray... How did you display a degree sign in your text

The easy way is hold down the left ALT key and hit 0176 on the keypad then release the ALT key ° ° ° ° ° ° ° ° ° ° ° ° ° ° ° ° ° ° ° ° ° ° ° °
If you open CharacterMap program (Start|Run|Charmap) you can see loads more like ¼ ½ ¾ † ‡ … µ ± ² ³ § © ®. There's a load more similar shortcuts which can be used in Word like <ALT>8486 for the ohm sign and <ALT>8734 for an infinity sign. If you're a really sad git, you can remember a lot of them without looking them up

[nicowalker1]

im hopefully doing my timing tomorrow, im slightly worried about doing it though!!!

[rip]

im hopefully doing my timing tomorrow, im slightly worried about doing it though!!!

As long as you mark the CAS's adjustment before you start, you can always move it back to where it started if it all goes belly up.

[GeoffSmith]

I then went out & did several runs, timing 30-70mph in 4th gear each time, making timing adjustments in between each run.
First time, this took 13.2 seconds. After 2 adjustments, this was down to 7.2 seconds. Any quicker & I would not have enough grip to cope with 2nd gear (& I have newish sticky Toyo Proxes too!).

Just a thought but was the car fully warmed up for the first run? The difference may have been due to the ECM limiting boost if the coolant wasn't fully up to temperature on your first run. Regardless, ElanScan logs would be good to see.

[dapinky]

I was lucky enough to be driving home at 0330 this morning on a nice flat bit of dual carriageway....

....so i gave it a go.....

....I couldn't get a huge variation on times with full movement of the CAS - it was always between 9 and 9.6 seconds (except for one run when i got over 15 - then realised i was in 5th )

I ended up with a CAS position where it seemed to give the best throttle response (immediate pick-up), and will see what the numbers come up at when i get the strobe out this week.

I can still get the wheels to spin in 2nd (and 3rd on a wet road with cold tyres)

Out of interest, what chip are you running (Iain) - i was on 'standard' settings (switch position 1) open loop.

I'll have another go when i get my new chip this week and go closed loop (does the chip make much difference to timing - or is that the whole point of this excercise to find out??????)

No elanscan - lead was in red car

[GeoffSmith]

All cars go open loop (i.e. rich as an MP's expenses account) when the boost kicks in, so there shouldn't be any significant difference.