timing tuning problem

[filh]

Hi Guys , Having some trouble with the timing tuning on my lightly modified 4age ( in/ex camshaft 256°
.As some known I use my ae86 on rallye here in Belgium .

Here's my problem : I know the process to tune the timing on a 4AGE .

Shorting the diagnose connector , T and E1 , setting on 10° at 800 rpm etc etc ......
But does anybody know the timing advance at 5500/6000 rpm.
Doing the process as described above , I 'm having 44° at 5800rpm!!
That sound much to me (too much?)

My machinist say it's far too much , and set the timing at 29°( always at 5800rpm)
Result of this : at idle(1000rpm) without diagnostic connector shorted timing advance is 7° !!
On road , that's not very expressiv........
Any experience welcome .
I'm still having the stock injection , with stock AFR . And the air /fuel ratio is ok .
I'm in a hurry as my nex competition is on Sunday....
Thanks
Phil Filh

[jondee86]

Retarding the base timing by 15 degrees won't do much for your
performance !!! If it ran at 44 deg total advance at 5800 rpm
without any problems, I would say that the ECU knows how much
advance to provide

Cheers... jondee86

[gon]

you must bare in mind that at 5800RPM at WOT the timing is diferent than at 5800RPM just cruising ....
if you wanna see how much advance you have at WOT without being at WOT just remove the vaccum pipe that goes to the vaccum sensor ( MAP ).

don't forget to put it back after you measured it

[filh]

I broke the engine two times this year , and the first time , timing advance was the reason .
My machinist prepares many races engines and he told me that on Opel AStra, Citroen Saxo, C2 , Peugoet 106 , at 6000rpm ,he never put more than 30° .
But , of course, he tunes the car on Dyno . But infortunately, I got no time to make the Dyno test , as my next race is on Sunday .
AS he set the timing on 3° at idle (T&E1 jumped) , we had 29° Timing advance at 5500 rpm .
But when I drove the car on road ,I found it much too slow , with a leak of power .
I've now set the timing at 7° at idle (T&E1 jumped) and it's now much more drivable . But the engine has only 200km and must have some more km to have a realistic try .But I will not have much time to do them!!
I'll try to remove the vacuum hose , but I'm not sure of it :
Is it the hose that goes from a black box(vacuum sensor) near the chassis number, to the intake manifold ?
I'll try if there is a change in timing advance by disconnecting it .
I forgot to mention about my mods , that I have a 0.8mm head gasket .
So the volumetrical ratio is higher than stock and may requires less timing advance ???
Thanks for helping
Phil

[jondee86]

Interesting thread this

I have been doing some reading, and as far as I can see, there is
only one way the ECU could give you 44 deg advance. You would
have to be operating the engine at high rpm's without any load.
Or alternatively, be operating the engine at high rpm's with load on,
but give the ECU a MAP signal for low load.

Looking at the ignition mapping for a standard OEM 4AGE ECU, there
is a big increase in ignition advance if you take load off the engine
at high rpm. So it might be worth checking to see if your MAP sensor is
sending the correct signal to the ECU under varying manifold vacuum.

Cheers... jondee86

[robokill]

filh

I assume you are using CatCams camshafts? If you do you have a similiar setup to my 4age. I am running 17 degree ignition on idle (1000rpm) with no te wires connected.

I had a dip in my peak power around 6600 rpm which was gone when we changed the timing. If the valve clearance is correct there should be no reason for the engine to break down. (apart from oil and water offcourse)

The 4age ecu is a good one. But I have to say with those cams I am running lean on fuel with teh standard (grey) injectors (182CC) So I will replace them with 210CC which is far more than enough.

[filh]

hello
[u:83afd0cede]To Jondee[/u:83afd0cede] : you're right the timing measure was done without any load .
But My machinist has a Dyno Bench and He may be refering to measure he did with cars on Dyno . I think my oem ECU works normally .
I'll try to do some measurements , without vacuum sensor hose disconnected .

[u:83afd0cede]To Robokill[/u:83afd0cede] Correct , I'm using Catcams and stock grey injectors .
The machinist gave me an Air Fuel Ratio Meter(Lumenition) to test the ratio , and it looks like it's correct or a little rich at +/- 6000rpm.

I've set the timing round 7° at idle with Diagnose connector jumped . Don't know how much without jumper .

And I finished my rally race without any trouble at all . T°always ok , oil pressure ok and no oil consumption .And as I had no time to , the engine had only 200km before starting the rally .

there were 4 AE86 at the start of rally , and we all reached the chequered flag

I think an incorrect timing is more sensible on races engine , as it's so often a WOT use

Anyway , thanks for your advice
Phil(Filh)

[jondee86]

www.ae86.hu/2008/04/06/jeremy-ross-lifting-the-lid-on-the-mk1-mr2-ecu/

If you follow this link from another thread, and download the PDF
file, on Page 12 you will see an Ignition Timing Table. This table
graphs load against ignition timing advance in non-defined units.

If you consider the 5600 rpm line and compare the maximum and
minimum values, you will see that at WOT (full load) the number of
units is 144. At minimum load (in neutral gear) the number of units
is 207. The ECU adds timing as the load comes off the engine, to
compensate for the changing burn characteristics of the weaker
mixture.

From this information, it is easy to see that if the timing was 30 deg
at 5600 rpm and WOT; without load the timing could increase to
40 deg or more. An example of when this would happen, is lifting
off the throttle between corners, to avoid making an up change and
a down change very close together.

Cheers... jondee86

[F0Bman]

Please be careful on advancing the timing too much as this can really be bad for detonation.

[filh]

Hello,
[u:1288e23746]To Jondee[/u:1288e23746] , you are taking some fear from me!!!!
As you said and proof with the PDF table , it 's possible to have 44° at 5500rpm, and WOT , but with a static test .
That would explain why I had a good timing advance at idle .
And if the car is run on a Dyno Bench , is it considered as on load at Wot?

To FOBman : I'm not planning to run with much advance , it's just that when my machinist and I , had a look at timing value , engine running at 5500rpm, it was 44° , but whitout any load .
Now , with Jondee explanations, that looks more clear to me .
Thanks again for your help
Phil