Autosport Labs

Just about to start out with default map but how do i know how much advance i can get away with? as the deault map should be a good starting point but how do i know if i dont have enough advance or i'm running too much advance ? the problem is the car i'm doing this to is not mine as i cant aford to mine yet but have advised a friend to do his but he has no patience for technology or computers so this is where i come in as i'm slighty better at computers then him and have slighty more patience aswell.

i know this is probably a very simple question to answer and i can appreciate the fact that every engine is an individual and no 2 maps will be identical even with the same engine spec. but as a newbie please be gentle.

also not that it should make any difference but the mjlj v4 we have is a map based unit and the car is being used as a track day / drag strip car.

What engine/specs etc. Also, do you have access to the stock distributor curve? I would copy that as a starting map. I took reading s every 500 rpm on my distributor before I removed it permanently. This gave me a good base map. My original dizzy had no vacuum advance unit, so it was easy to duplicte the curve.

Hi there thanks for the reply the engine i'm going to be mapping is a 2.0 silver top zetec which is running a pair of 40's so as std they never had dizzy so i cant copy any thing not to mention how would you go about copying the advance a dizzy puts out anyway??? as this is all a bit new to me so hence what might appear to seem like stupid obvious questions to some is all new info to myself.

But hopefully i'll get there.

Put a timing light on the crank pulley, then log the advance as you go through the rev range. If there isn't a mark/degree scale, put one on. It doesn't matter if your engine has a distributor, the original engine computer will still alter the advance, so you should be able to read it.

i'm with you on that but how would you emulate the load as am assuming you can't run at 60mph with a strobe gun in your hand to get the loaded up strobe reading while on the move as not everyone has access to a rolling road to get every 10x10 window filled.

Well, now I hear you. My dizzy was centrifugal only, so I added load sensing with Megajolt. I guess you need to see the range of vac advance. If you can't do that, then put in about 10 degrees at light load/mid rpm, and fade to zero as you get to full load. Some cars can take 20 degrees, some only 5 or so. Drive it and see, and keep tweaking. Like I have said before, I am on the 20th version of my map, and added load sense around the fifth version.

Also another nice way to compare maps is to use the switchable mapping option. This way keep your original map on one switch position and the new map to compare against it on the other switch position.

Cheers for the replies

I'm starting to get there now but again what would be the sign of too much advance?? would i get pinking? like you did with older mfi turbed motors (rs turbo) as these had a knock sensor to retard the advance if this was detected due to to much boost or dizzy advance.

just if we are going to be driving about in the car with a lap-top i need to know what the hell i'm doing and listening out for all i got off him was "I want it fast as f**k and totally flat out to the boards power i dont care if it will blow up!!!!!"

which is fair enough but at the same time i cant advance the nuts off it other wise it will pink its head off and have no power, i will be starting with the base map but as his is running 10deg btdc all the time anything must be an improvement not to mention we have 1/4mile times already to compare it to so we will tell if the advance is making any difference to putting the power down.

If you have too much advance then yes you will get pinking, basically it sounds like a diesel. Obviously if you can hear it whilst driving you have way too much advance.

What you want to be able to do is detect pinking before the human ear can pick it up from the sound of an engine whilst driving. So you will need to have a device/amplifier to help you hear pinking sooner.

To do this i have seen a couple of ways which are very affordable as in less than £10. When you have obtained one then you need to listen to the engine when it isn't pinking and be able to differentiate from all the differnt engine noises ie valve slap, rocker gear noise, etc,etc, compared to when it is pinking or just starting too. This takes a small amount of time of ear training but doing it this way i believe is alot more accurate then using a knock sensor as the ear is alot more sensitive and can differentiaite sounds better than any knock sensor.

So far all this is theory to me and have not yet put it into practice myself yet but to me seems the best way of tuning and detecting pinking.

The Zetec is a nice modern head design so has a wide power platteau between MBT (Minimum Best Timing) and the knock threshold. What that means is that there is a broard band of advance between those two extremes where the power doesn't change and you won't do any damage to the engine. In an ideal world there are advantages to being as close to the MBT threshold as possible but in reality as long as you're not on the knock threshold things will be just fine.

On older engines that have been pushed to the limits of tuning can have a very narrow threshold of just a couple of degrees between MBT and knock, so getting the map spot on is important but on modern engines like yours probably has a platteau of 8-10 degrees. With such a broad range of "optimal" timing you drop one of the example zetec maps on there and be reasonably confident that you are within a gnats whisker of perfection.

cng1 wrote:The Zetec is a nice modern head design so has a wide power platteau between MBT (Minimum Best Timing) and the knock threshold. What that means is that there is a broard band of advance between those two extremes where the power doesn't change and you won't do any damage to the engine. In an ideal world there are advantages to being as close to the MBT threshold as possible but in reality as long as you're not on the knock threshold things will be just fine.

On older engines that have been pushed to the limits of tuning can have a very narrow threshold of just a couple of degrees between MBT and knock, so getting the map spot on is important but on modern engines like yours probably has a platteau of 8-10 degrees. With such a broad range of "optimal" timing you drop one of the example zetec maps on there and be reasonably confident that you are within a gnats whisker of perfection.

Thanks for that, this will be a great help when it comes down to tinkering with it and by the sounds of it the zetec can be a good practice engine due to the massive window of scope while doing no damage due to the 16v head, but here is a good question on another thread i am building a zvh (8v/16v hybrid) due to the older style head being fitted this will give me a smaller saftly window and a greater chance of hitting the pinking limit by having a smaller safty window.