Sneezing

[NikUK]

Hi

Me again! Have had the new car for a couple of weeks and I'm over the moon with it! My little mod of moving the pedal box forward a little and had to remove a little from the bottom right of the dash so my knee can fit have worked wonders. Still need to probably find somebody to sort the roof out as it seems about two inches too short!

My main question is as my car is cold and at low revs it seems to pop and sneeze from the carbs a bit. Do yo think this is normal or is my timing out. It was put on a rolling road by previous owner a couple of months ago but I just thought i'd get your opions. when I'm moving and have the load pedal pressed it runs very well and doesn't seem to miss a beat!

The engine is a 2.1L pinto with twin 45's.

Thanks in advance

[Hammy]

When its cold it needs mixtrue enrichment and as you've none it will tend to hesitate.  If its fine when hot all is well. Popping is an idication of lean mixtrue so it sounds right.

Bear in mind that 45's  are big carbs and at low throttle there is not much pressure drop in the venturi to work them, comibined with cold running it's pushing their abilities.

As a possible upgrade mapped ignition may yield some improvements in giving extra part throttle advance,

but it all sounds normal to me !  Enjoy.

[NikUK]

Thanks Hammy

Is the ignition mapping a good option to have done?

Is it an expensive mod? I realise I would get a smoother running and maybe a more reliable system, does it give more power against standard setups?

Thanks once again

Nik

[markcoopers]

The theory is that the same size hole in either a Throttle dody or carb will flow the same air, and the engine can burn the same fuel.....hence the same power regardles of choice.

Carbs though will be a set up with a series of compromises to allow the best from a wide range of oporating conditions. ie a jet that delivers enought fuel at full chat might deliver too much at part throttle openings. Well mapped ignition or full management essentially allows a greater control over the engine and minimises/removes these compramises with no poor consequences. Hence why a well mapped set up is always recomended.

This in no way implys that carbs can not be set up well, and that the compramises can not be ironed out/made really small, but the effort and expenditure to achieve this could be far more than the gains achieved. In theory each progression hole should be drilled to each specific engine as they are all slightly different, let alone all the jets/restrictions/emulsion tube/correctors and pumps combinations that cold be used....hence why commonly used set ups tweeked to specific needs often get used and the "they all do that" part is acepted.

In the end, a badly running car will show it'self in many ways, flat spots/hesitations, will not idle, will not rev, fire on only 3/miss fire. If it goes well regardles of a few counghts and farts.....it goes well, so no issue.

[Hammy]

Mark is dead right.  The big thing with a mapped igntion system apart from a more "accurate" spark and improved hi revs performance is that presently you will have no vacum advance with a Dizzy.

This means that at anything other than wide open throttle you wont have enough ignition advance for the engine so it wont run at its most efficient and  wont pick up as well when you progressivley open the throttle. It can therefore generally smooth things up a fair bit and over come drivablity issues that are not down to the carbs ( but they get the blame). It may give the odd BHP or so flat out.

It may give you a couple of MPG too and gain a gear change light or two.

There are various systems about, if you are electrically capable and have some computer knowledge then you could fit Megajolt for about £160.  There is lots about it on this forum or  google Megajolt.

[davehall]

Agree that a mapped ignition will make a huge difference. I've got an XFlow and when I did my Megajolt, which was a doddle to do, there was an immediate improvement in running and idle, and that was before I played around with the map. But, I was still getting popping and spitting back through the carbs. I decided to service the carbs and found that the float levels were way out. Once that was sorted the popping and spitting vanished and now I've tweaked the map it runs like a dream.

Definitely worth doing.