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Overrun Remap! Bit more than i expected!!



  Black Gold 182
Sure.

It holds open the throttle body (or ICV on a ph1) to allow more airflow into the engine.
Then to stop it making power from the extra airflow (cause you dont want to make power at zero throttle) it retards the timing massively
The air and fuel in the engine fails to burn properly as a result, so ends up in the exhuast only partially combusted, where it then finishes burning and makes popping and banging noises, especially any that makes it to fresh air still not burned as then it gets more oxygen supply than is present in the exhaust.

Having a burn still going on during the exhaust stroke, and while the gasses are flowing past the exhaust valve can cause the 2 piece standard valves to fail, and I would expect also for it to make the head go soft if used a lot although Ive not seen it specifically in the context of a pops and bangs f4r map but have seen similar on other engines running antilag.

The amounts of fuel and air involved are relatively low, so if its only used occasionally you are likely to get away with it, but if you use it a lot then in my opinion its when it will fail not if.
If i drive below 4.5k it doesnt do it, only minor burbles. So its only really happening when i drive the car hard/hardish, which is pretty rare. I'd say i'll be rarely hitting over 4.5k once or twice a day....is this enough to cause damage? I really cant make my mind up. Going through bridges/tunnels etc is absolutly hilarious no matter how much of a C*** i look but i dont really NEED the map and if its going to do damage with how much i will use it i'll probably switch to the 98 RON map.

After driving the car today i must say im even more impressed with the actual map. The revs drop considerably slower when changing gear, and as i like to change pretty slow and gentle its made the gearbox seem like it changes a hell of alot smoother. Before when changing gently somtimes the revs would drop a little too much and it would cause jerky changes or the actual gear slotting into position would feel a little notchy as it wasnt properly rev matched. Now its made the car an absolute pleasure to drive.
 
  Iceberg 172
Just to drag this back up.

Did a datalog on one earlier.

It showed an AFR of around 22:1 and ign advance -18 through to -13 degrees.

Awesome Dan, thanks for remembering. Very interesting numbers and still a bad idea haha
 
  Lionel Richie
Just to drag this back up.

Did a datalog on one earlier.

It showed an AFR of around 22:1 and ign advance -18 through to -13 degrees.

and for the people who don't understand that and carry on "cos its wicked", those figures are..................infact, just carry on being wicked
 

BoatNonce

ClioSport Club Member
Please explain them for people who doesn't know what it means!

AFR, or air fuel ratio, should be 14-15ish to one in an ideal world (think it's something like 14.7). Higher number means lean, lower means rich. Lean causes detonation (basically an explosion instead of a burn) and raises exhaust gas temperature.

Ignition advance is when the spark plug fires relative to the piston. 0 is top dead centre, when the piston is at the very top of the cylinder, positive numbers mean the spark occurs whilst the piston is coming up, and negative is when the piston is coming down (or retardation, which is a pretty good word for this really). That amount of retardation will generate a lot of extra heat which again leads to increased exhaust gas temperature.

Basically it adds up to burnt out exhaust valves and a generally f**ked engine.
 

Mr R.

ClioSport Club Member
  A special one.
AFR, or air fuel ratio, should be 14-15ish to one in an ideal world (think it's something like 14.7). Higher number means lean, lower means rich. Lean causes detonation (basically an explosion instead of a burn) and raises exhaust gas temperature.

Ignition advance is when the spark plug fires relative to the piston. 0 is top dead centre, when the piston is at the very top of the cylinder, positive numbers mean the spark occurs whilst the piston is coming up, and negative is when the piston is coming down (or retardation, which is a pretty good word for this really). That amount of retardation will generate a lot of extra heat which again leads to increased exhaust gas temperature.

Basically it adds up to burnt out exhaust valves and a generally f**ked engine.


Chip, is that you?
 

Ol’ Tarby

ClioSport Moderator
  Clio 220 Trophy
AFR, or air fuel ratio, should be 14-15ish to one in an ideal world (think it's something like 14.7). Higher number means lean, lower means rich. Lean causes detonation (basically an explosion instead of a burn) and raises exhaust gas temperature.

Ignition advance is when the spark plug fires relative to the piston. 0 is top dead centre, when the piston is at the very top of the cylinder, positive numbers mean the spark occurs whilst the piston is coming up, and negative is when the piston is coming down (or retardation, which is a pretty good word for this really). That amount of retardation will generate a lot of extra heat which again leads to increased exhaust gas temperature.

Basically it adds up to burnt out exhaust valves and a generally f**ked engine.

Have you copied and pasted that from one of Chip's old posts? Lol
 
Basically what mcg said.

14.7:1 (14.7 parts air to 1 part fuel) is what's known as the stoichometric mix (stoich), or perfect chemical burn. On cruise, (I.e 70mph in 5th) you want it to be as economic as possible, so lean it out slightly. Around 15-15.3 is acceptable. Any more than this and it's too slow of a burn and means less power, and there fore more throttle etc.

On full throttle you want it to be rich, this is because the burn of the fuel is hotter than the melting point of the piston and you add fuel to this to partially cool it down, but it also produces a more controlled burn being rich. You want really between 12.4 and 13 really, but the odd spike above 13 won't do any harm, aslong as it's still below 13.5, on an NA engine anyway, with boosted applications you want to be below 12:1 really, my supercharged one was a proper angry engine at 12:1, but for safety it was mapped to 11.5:1.

With ign advance, it's adding the spark advance (advance is timing it to get the peak amount of burn/cylinder. What you really want for peak power is an ignition value that puts peak cylinder pressure at around 15 degrees after TDC generally. But it's not always possible. That's why sometimes more boost can mean no more power as you have to r****d the timing to avoid det and then end up with peak pressure too late. But is to get it so that the burn is not fighting the piston on its compression stroke, this is what's known as det, and common indicators of this are broken spark plug tips, and burnt out pistons (or is very common on the F4, broken ring lands) mapping these takes time and knowledge, rushing them creates issues as does lack of knowledge/ignorance. When mapping ignition, taking an engine into det is not great for them, but absolutely unnecessary on a dyno, as you can monitor the tractive effort on a certain point and keep adding ignition until it stops making more power. After this there is zero point in adding more ignition, as it will not make any more power, but start getting towards the danger zone
 


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