Bespoke mapping - what are the pit falls?

Hi Guys, When i had my NAT Conversion three years back by "Rocket Dog Racing" in Cardiff i was well impressed with the performance, the Engine Tuner / Mapper charged £250. At the time i did not pay much attention to this side of the conversion, i assumed the guy just plugged in his laptop software and drove up and down.

Recently i had to change the stock NA head gasket, it had failed on the front cylinder, car has covered 42,000 miles from new and 3,000miles with the conversion. I worked with my friend a good mechanic changing the gasket, it is a big job and risky to the uninitiated, i shelled out £1,000. To avoid a repeat of the failure i fitted the thicker more robust gasket, (£150), unfortunately the reduction of the compression ratio from 10 to 1, down to probably 8.5 to 1, has reduced the performance, the estimate being a loss of 50 BHP.

The car is still fast but the loss of power is quite noticeable to me, the torque at the bottom end and the loss of the spooling screaming noise has gone.

So now i am fitting a larger exhaust system, 550cc injectors and a larger fuel pump, this is a breeze after doing a head gasket job, my problem now is the re-map and finding a reputable company / guy who can carry this out.

There is a lot of scaremongering surrounding bespoke mapping, not the plug and play piggy backs, its a bit like your timing belts level of importance, where you can wreck your engine, what i do not understand is how big a mistake with software does the Tuner/ Mapper have to make to destroy your engine? The valve timing and ignition timing are mechanically set, etc. I understand that there are many examples of the car not starting, or the AFR being out, or miss firing etc, but what causes the engine's destruction with a flawed MAP? Herbie.

Engine destruction is normally due to one or more of the following (in no particular order):

- Excessive temperatures & inadequate cooling (coolant, oil, combustion)

- Component lubrication failure

- Lack of safety protections implemented (overboost, detonation, low oil pressure, rpm limits etc)

- Hardware failure

- Improper component installation & maintenance

- Wrong or improper components (eBay parts that have a habit of failing once stressed)

- Exceeding the mechanical strength of brand new or 20 year old components.

- Getting greedy with power and finding the weakest link quickly. (Excessive timing, boost, lean fuel etc)

- Improper fuels used (95 octane is good for 2 bar boost right?)

- Aggressive map that makes good numbers but contributes to one of the above in the real world and dosen't last long.

- Driver abuse (I heard a weird noise so I kept driving another 30 miles)

I'm sure there is more, but these are some of the things that mappers must face. Some they have control over, others not.

In terms of how big a mistake a mapper needs to make. It can be big and happen quickly, or a small mistake that takes time to do damage. Either way its fucked. This could range from overboosting with no protection once and melting a piston, or it could be slightly too much timing on boost that detonates the combustion mixture slightly and after 6 months of abuse the piston or valve finally gives in.

There are many possibilities on how a mapper could make a mistake. Pair that with the possibility that an engine might not be in the most healthy shape for more power, and it's no surprise why you hear people exceeding their limitations on every engine setup out there.

Anyway this has been all worst case scenario stuff. In the real world a decent mappers takes into account the above and will have specific ECU's & parts they like to work with as it gives them confidence to supply a tune that does the job on the dyno and can continue to perform out in the real world safely. So usually a good idea to follow their advise, especially if they have a portfolio of work that can prove their skills.

Hi Mike, A great post, you have refreshed my confidence. I can see that the failure modes are not as dramatic and definative as a mechanical timing belt failure, in that the mapping parameters seem to be much more qualatative. The detonation aspect would be a major concern, where the AFR and boost can be monitered by the driver.

David P gave me a good contact in Northampton but it is a balls ache having to travel so far, i have a tuner/mapper near me in Blackburn, but they are asking £600 for their own bespoke maps, and tend to carry out plug and play maps. Do you know if i already have a good map, this makes a re-map much easier and much cheaper?

Anyway you have given me more confidence and i have a good friend ex Mercedes wiz who chipped my Merc who knows a retired mapper and he may look at my car. Herbie.

Herbie you need a lower compression for higher boost. You've created lag due to the compression ratio.

You sadly will struggle to map out what you loose in compression ratio.

If you want more power its ideal. I have a lower ratio also.

Dont forget the NA ratio will always be more responsive.

You may also be running too big a turbo for your hp level.

I'm looking at pre spoon nitrous at some point. A 25 shot would solve your issue pre spool.

Hi Mike, A great post, you have refreshed my confidence. I can see that the failure modes are not as dramatic and definative as a mechanical timing belt failure, in that the mapping parameters seem to be much more qualatative. The detonation aspect would be a major concern, where the AFR and boost can be monitered by the driver.

David P gave me a good contact in Northampton but it is a balls ache having to travel so far, i have a tuner/mapper near me in Blackburn, but they are asking £600 for their own bespoke maps, and tend to carry out plug and play maps. Do you know if i already have a good map, this makes a re-map much easier and much cheaper?

Anyway you have given me more confidence and i have a good friend ex Mercedes wiz who chipped my Merc who knows a retired mapper and he may look at my car. Herbie.

I'd disagree with that statement a little. Given data to work with a Mappers job is both qualitative and quantitative. IE Any change they make ideally has both a numerical output via a sensor that they can monitor, as well as say listening for knock before proceeding with the next change.

Ideally things like AFR, Boost, Detonation should be monitored by the ECU and setup to intervene should a situation occur that is deemed harmful. Most drivers under full throttle are paying attention to staying on the road, not monitoring engine vitals. I've seen it with my own eyes, no driver can react as quick as an ECU. For example, your AFR's and boost could be spot on but on a loud exhaust turbocharged engine you might not hearing it detonating its tits off. Ideally that would be the job of the knock sensor to react.

eManage ecu mapping is different to a normal standalone as its a piggyback. At no time does the mapper have full control over what the engine is doing. The emanage is feeding off the inputs/outputs that the stock ECU is programmed to do, then fudges some signals to either add or decrease certain variables to achieve an outcome. So the map you have on there already will probably be in the right direction, but if you are planning a new exhaust, injector change more boost etc, then the mapper essentially has to start from scratch as your old map was setup for a different setup.

On the flip side, one positive of the piggyback setup is that you only really have the option to tune fuel & ignition tables and a few engine limits. Most of the other elements of the engine's running like Cold Start, Idle Control, Gearbox control etc are all handled by the factory ECU so its not difficult to have a car that drives well as stock ECU is still doing most of the work. This will also cut down on mapping time compared to a standalone.

It's been a few years since I stopped doing emanages, but it definitely didn't take £600 worth of labour to map one. If you get one of your mates to help you, make sure you have an old laptop with windows XP & a serial cable. Emanage software does not like playing nice with newer windows or USB/Serial adaptors, hard to make work.

Hi Mike, I did not think you could top your last post but you have done with this one, be great if you could map my car.

With reference to the "Emange" piggy back, yes this for me was great, i had good tick over, good starting, good torque and good performance, the spooling noise was great. All this went away with the fitting of the thicker gasket for logevity, i had to do this as the OEM gaskets were not FFP, (Fit For Purpose), and to avoid another failure i took the hit on performance.

So i am going forward now with 550cc injectors bigger fuel pump and more boost, try for 500 BHP, i feel more confident now with your information, my top rated Merc man's friend hopefully will sort out the map. Thanks again. Herbie.