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Hesitation When Accelerating 1275 (Megajolt)

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#16 oliver122

oliver122

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Posted 25 March 2022 - 12:22 PM

the odd degree in that 40kpa load site is probably not going to make any difference, you might find the engine never actually runs in some of those load sites except on over run.

If it does then typically it is a fairly lean low throttle situuation where the burn rate will be slow so the engine will probably want a fair amount of advance, I would have no qualms about putting a few more degrees in that area to see how it runs, its the 80-100kpa area's you really need to be careful with as thats where you can get detonation that may damage stuff.
 

 

Thanks for the info , i will probably leave as is as it was fine before the hesitation issue but thanks again for the help 

 

 

So it was mechanically 4 degrees out with 4 degrees offset in the software? Does that mean you've bolted it back together better than it was before  :huh:

 

 

Could you have flipped the trigger wheel over???  4 degs of mech retard with 4 degs of software advance would put you at tdc, but 4 adv + 4 adv would have you 8 degrees out.

 

It really doesn't matter if you're working from the actual tdc, it's just a datum, but it's handy if you can refind it easily - as Mini 13 explains. Also helps for comparing notes & pinching other people's ignition maps.

 

 

As far as timing bins & interpolation: Yes, you'd expect a smooth progression, but the beauty of being able to program each bin independently is  not having to - say you found a particular point where it pinked, you could retard the timing just there to take it away from detonation. Some bins will be used more than others, say it's a road car that you want economic cruising out of at 55mph.

 

when i had it tuned it had 4 degrees advance in the offset on the software i assume done by the tuner when the base map was installed . (to be honest id like it tuned again as i wasnt 100% happy , would not let me stay and watch and was reluctant to say what he had done it always has seemed to run rich ) 

 

I went to the effort this time of pegging the trigger wheel and crank pulley together while ive had the engine out. Previously when i was having issues with the timing case seal when i bolted it all back up the trigger wheel would turn as i was tightening the crank bolt . I presume that's what had happened originally when i sent it to be tuned .







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