Timing wont follow ignition map

[Ken Dunkley]

Hi- I have an Atom G4+ on a V8 running a locked distributor . The trouble im having is the timing advances without following the ignition table . With the engine at about 70deg temp - 1000 rpm and the whole ignition table set to 20 degrees BTDC and no other timing compensations ( that I can tell ) happening - if I rev the engine the timing rises to over 50 + degrees with the engine missing/ cross firing badly . On the runtime values it shows 20 degrees and nothing else and on the ignition angle dial gauge on the tuning page it also shows 20 degress . But rev the engine and the timing climbs at a steady rate when checked with a timing light all the while the ecu s telling me its at 20 degrees BTDC. And yes the distributor is definitely fixed and no centrifugal advance . Whats wrong ?

[Adamw]

If your trigger systems uses a vr sensor I would say most likey your vr sensor is wired back-to-front. 

[Ken Dunkley]

Hi - Was just going to add distributor uses VR and im using a MSD streetfire  ignition . Ill reverse the wiring and try that - Thanks .

[Ken Dunkley]

Ive reversed the wiring from the distributor pickup - Same thing still happens . Apart from having to retard the dizzy position to get it to run the timing still wont hold . Even when the trigger timing calibration  window is active the timing rises . Any ideas ?

[Scott]

Can you post your base-map and a PCLog of the problem occurring please.

[Simon]

The MSD unit is likely to require a rising spark edge as apposed to the more conventional falling spark edge. 

[Dave Kriedeman]

Hi,

Simon is correct, MSD units use a rising edge trigger not falling like most other manufacturers, also did you set the IGNITION DELAY correctly.

Regards

Dave.

[Ken Dunkley]

Hi - I did set the trigger to falling edge and with the ignition delay any number I set in the window had no affect . Ill reset to rising edge and retry . Would you expect this problem with the timing if the trigger edge was reversed as I had it ? Thanks for all replies .

[Ken Dunkley]

Ok - Success ! Changed the trigger to rising edge and problem fixed ( also swapped the pickup polarity back as I had that right first time ) . Thanks all for your help . But - One last little issue - I cant get the accel enrichment to work . The engine starts and runs fine but if I crack the throttle it goes lean momentarily and bogs . Tried accel sensitivity increase and wakeup enrichment - looked at accel load clamps etc but cant get any enrichment happening - Have checked runtime tables when blipping the throttle and set up a digital gauge to watch percent of enrichment as blip the throttle but nothing happening . Where do I start . ? And just a couple more questions  - Using modelled fuel with a fuel pressure sensor setup through a AN input - Does the ECU respond to fast pressure changes ( as its manifold pressure referenced ) and make fuel corrections ? If ive set an AN channel to fuel pressure and calibrated it - Is that all I need to do for the ecu to read it and make adjustments as it should ? Thanks Ken .

[Scott]

Hi Ken,

If you post your base-map and a log of you attempting to get accel enrichment working we can take a look.

When using the modelled fuel equation the ECU will start adjusting the fueling as soon as it sees a change in fuel pressure. To get the fuel pressure compensation working you will need to set up the FP sensor (as you have) and also set the 'Fuel System Type' to FP Sensor. This setting is under ECU Settings > Fuel Setup > Fuel Main.

The modelled fuel equation relies on having precise and accurate data entered and the settings being configured correctly. If these numbers are not exact the fuel pressure compensation will still work, but not be as accurate.

 

[Simon]

Before worrying too much about accel fuel the tune will need to be relatively close to start with as you could end up compensating for a particularly lean spot in the main map.

 

[Ken Dunkley]

Simon - Yip im getting it sorted - Now the timing is sorted I got the fuel map much better and after reading different posts on the subject and watching an HP Academy webinar on accel enrichment I realised I had the accel enrichment WAY to rich . After bringing down accel sensitivity and clamp numbers things improved out of sight . The engine responds to the crack of the throttle like no carbed engine ive ever owned ( Lots - And they run well ) - It positively barks !  Im almost there ive just got to sort a small off idle stumble so any tips are appreciated - Thanks Ken .