4AG dissy ignition question

[terryo]

i have a M4 on a Toyota 4AG race engine. it is constantly hard to start and i'm trying to progressively work thru it

the dissy has a 28 tooth chopper + 1 tooth reference

When i'm cranking, the ignition table lists 'no errors' . The diagnostic table however says "not Ok-Sync status'

i thought it might have just been a cranking issue, but even if i get it to fire and run for a bit, i still have this 'not ok-sync status" message

there is no obvious fault with the dissy, all the internal coils are ok and gaps set correctly. when it eventually fires, its seems to run OK at 3000rpm or more, but lower down its horrible

The next clue is the crank index position (CIP) in main set up table is 202 (I assume degrees) and highlighted yellow with an asterix beside it. is this somehow related to the fault message???

When i remove the dissy cap, the single reference 'tooth" is about 100 degrees from its pick-up when #1 is firing. This cannot be changed and nor can its relationship with the muti-tooth chopper below it on the dissy shaft

I would appreciate any insights anyone might have

[SprinterTRD]

Are you sure yo have 28 + 1?

Toyota 4AG's have a 24 tooth NE signal

[terryo]

thanks for pointing out my typo Steve. its 24 x 1

this engine has a modified early big port dissy with 3 teeth filed off. i'm trying to track down the later small port dissy which has a 24 x 1 ex factory, rather than destroy another perfectly good early dissy.

i'm really tearing my hair out with this hard starting and apparently they were pretty much always like this once the compression goes up a lot. when it was relatively low compo, everything worked just fine but the latest 'upograde" has really made it annoyingly difficult. i've had a mate who is an electronics engineer look over the scope traces and he says he cant see anything fundamentally wrong but he suggests the "smart" Bosch module with variable dwell is unnecessary. Also , of course , it takes several rotations to get the dissy and motec synced so that does not help

have you still got the old TRD stuff in yours, and if not, how did you overcome this. one suggestion is to move to a Nissan punched plate in the dissy so it get a cylinder ID much easier

[SprinterTRD]

Simple answer is the the voltage from the sensor varies so much at cranking RPM with high compression the ECU can't lock onto the signal. So close up the gaps between the sensor and tooth. I used a sheet of 80GSM copy paper to set the gap.

What serial number is your M4? Is it a REV E one?

The "E" ECU's have extra choices for magnetic sensors with low output signals.

You could try a user defined levels for REF & SYNC.

Make sure the starter & battery are in good condition to get the cranking RPM more constant. I assume you are using a geared starter.

Going through the above usually works.

The module won't be a problem.

[terryo]

thanks steve,

i'll remove the dissy and check the gaps tomorrow

Motec is #2140, with v6.1 software

i am using an original starter but with some re-wiring and a brand new 325cca battery, ive got the cranking (with no plugs) up to 300rpm , so that is easing matters. i have had no luck with later gear reduction ones as the plastic gears shear easily, but if you have a particular starter model in mind, i'd be happy for a suggestion

[terryo]

steve, ive found the gaps are 0.25mm and 0.35mm which is Ok according to Toyota. I have reset them both down to 0.08mm, more in line with your paper thickness.

it now starts a bit better but i still have a misfire on 2 cylinders i need to trace. everything is brand new so it will be a hunt

i attach a couple of pics of the setup. The dissy is set to align with motec at 9 BTDC when cranking at 300rpm

it appears the rotor arm is past the #1 terminal post at 9 BTDC and well past it by TDC . when installed, its very hard to get an accurate reading on that

the only reference trigger is about 100 degrees past #1 firing point. The CRIP is set at 220. Would that suggest someone filed off the wrong triggers???

[Wolf_Tm250]

Hi Terry,
no cam sync on that setup?
Wouòd it be possible to turn that 24 +1 wheel to a 24 -1?

[SprinterTRD]

The CRIP for that setup should be around 6 degree for a standard cam.

Are you using the correct rise & fall settings?
Have you checked them with a scope?
If not have you wired them per the MoTeC trigger drawing and used the suggested values ?
I would guess its a modified cam has it been indexed correctly?
If its a welded up cam have they kept the lobe centers relative to the distributor gear the same as the standard cam?

Set the crank to 10 deg BTDC
Set the distributor so the end of rotor button sits facing the no1 distributor post. Make sure you choose the correct end so when you advance the timing it would travel across the rotor button.
Fit the cap
Take the spark plugs out
Set the test advance in to software to 10 deg BTDC
Crank engine
Adjust crip to the 10 deg mark lines up with the crank

Its that simple!

[terryo]

thanks Steve

i will methodically go thru your suggestions and scope it

yes, Motec basic settings as per Motec "diagram" except for CRIP

That dissy was with the car when i bought it, and I raced with it for ages. I was however never happy with ignition system as it was always 'weak". It has/has a Bosch igniter and matching oil filled cylindrical coil. When it last raced GpA it had an Inject computer but that is long gone. Someone converted it to M4 in about 1995... no-one remembers exactly but i guess the Serial # is relevant

TRD billet cams. 1 is genuine, 1 local copy, i'll check which is which

I spoke with Iain at Motec Brissy thru the week to book some dyno time and he suggested 20kv was needed for relaible high comp 4AG. I purchased the Bosch 'transformer" coil he suggested , and instantly the peak voltage has dropped !!. I 've checked and Craig Taylors TTA car is still running the factory coil and igniter!. Why did Motec specify Bosch stuff if it can work with that Nippondenso igniter & coil???

[SprinterTRD]

It will make no difference which coil module you use as long as the coil is matched to the module. Which Bosch coil did you get?

Different ones require different dwell times which may be the cause of poor spark