That ‘DIY spirit’ is ingrained in us as automotive enthusiasts – it’s what makes tweaking, tinkering and modifying fun. Sometimes it’s for the cost savings, but equally it can be all about challenging yourself to develop new skills. As more and more cars are pieced together in backyard sheds, some of the basics of engine tuning are starting to become more important to the home enthusiast; for example, ignition timing.
Sure, if you’re taking your car to a pro tuner then this should be dealt with by them, but what if you’re planning to tune it yourself? Or perhaps you want to save some hard-earned dollars by getting your pride and joy running yourself before heading to the dyno? If this is the case, then there’s a couple of basics you need to know, and in this Knowledge Boost story we’re going to discuss setting the base ignition timing.
Timing is everything
Correct ignition timing is one of the most critical elements in tuning any engine, yet setting the base timing is often misunderstood and overlooked. So what is base ignition timing? Well, first we need to take a step back and understand what ignition timing is. The ignition timing or ignition advance, is the point in the engine cycle when the ECU generates the spark at the spark plug. This spark begins combustion and it has a direct effect on how an engine runs, how much power and torque it makes, and how reliable it is.
The actual ignition advance value is defined in degrees of crankshaft rotation before (normally) the piston reaches the very top of cylinder on the compression stroke. This point is known as top dead centre (or TDC for short). When you hear tuners talking about ignition timing they are talking about the number of crankshaft degrees before TDC (BTDC) when the spark event has occurred.
Now you understand what we mean when we talk about ignition timing, we can see how this relates to our aftermarket ECU and why it’s so important. Inside our ECU we’re going to have an ignition timing map which defines the amount of ignition advance we want at each point in the load and RPM, and this should be pretty straightforward. The problem is that the ECU has no idea whereabouts in the engine cycle the engine is, and hence it can’t decide when to create the spark. What this means is that we may have entered an ignition advance angle of 15 degrees, but if the base timing is over-advanced by 10 degrees, the engine will actually be receiving 25 degrees advance, and this can cause serious engine damage. In order to create the spark at the point we want, we need to let the ECU know exactly where it is in the engine cycle and which cylinder is about to fire.
The ECU gets engine speed and engine position information from toothed trigger wheels fitted to the crankshaft and/or camshaft. Setting the base ignition timing means that we are telling the ECU where these trigger inputs are occurring in relation to TDC – essentially whereabouts in the engine cycle the ECU can expect to see the trigger inputs occur. The way this is done is to put the ECU into a special timing mode where the ignition advance is locked at a fixed value regardless of what the numbers in the ignition table are. Every ECU will have a ‘base timing mode’ that’s included just for this purpose and usually we can select an ignition angle that the timing will be locked to.
The next step is to use a timing light connected to the coil or ignition lead on #1 cylinder and view the actual ignition timing the engine is seeing. The timing light flashes every time a spark occurs, and by pointing the timing light at the crank pulley we can view the timing marks while the engine is running. The timing marks will consist of a mark on the crank pulley and a mark – or multiple marks – on the engine cover, and by watching where the marks align when the spark occurs we know what the ignition timing is. We can then adjust the timing calibration in the ECU until the timing we are seeing with the timing light is the same as what the ECU is commanding.
It’s important that we select an ignition angle that we can easily see on the crank pulley with the timing light, and this can be tricky on some engines with a lot of ancillaries blocking the view. It’s also useful where possible to select a sensible ignition angle during this procedure that the engine will happily run at, such as 10-15 degrees. If you set the timing to 0 degrees for example, the engine will struggle to run smoothly and this makes the job harder.
Completing this process accurately is essential to ensure the timing in our ignition map is actually what the engine will receive. In the best case scenario, failing to do this can result in an engine that is down on power and torque and is just a general slug. In the worst case though, if we have too much ignition timing the engine may suffer from detonation and this can cause expensive engine damage.
Is it time to hit the dyno yet?
So now the base ignition timing is dialled in, but you’re still not quite done. In our next story we’re going to look at setting base fuel pressure and how this can affect your tune. Setting the base fuel and ignition timing make up one of the very first steps of HPA’s 10-step tuning process and these need to be covered before you even try to start the engine for the first time, let alone hit the dyno. While there’s a lot more to tuning than these two elements, if you don’t have the basics correct then you’re just wasting your time or asking for an expensive disaster. Even if you have no intention of tuning your car from scratch in the near future, this is the sort of knowledge that all enthusiasts should have at least a rudimentary understanding of. You never know when it’s going to come in handy!
As always, if you have more questions, ask them in the comments section below and I’ll do my best to answer them there. And if you’re interested in learning more about EFI tuning you can sign up here for a free 6-part series that will be delivered directly to your email inbox.
Andre Simon
Instagram: hpa101
Website: www.learntotune.com
Photos by Ben Silcock
OFFICIAL SPEEDHUNTERS SUPPLIERS
cool! keep talking...
While I appreciate this series and your work, I just feel this is too simple an overview for SH fans to go by to tune their own ignition timing. I just refer to this (in very basic understanding) at the points in which air and fuel is mixed and ignited and in which order the cylinders fire. Thank you though for explaining to the engineering illiterate such as myself in layman terms.
John Key NZ just to be clear, this story is not about tuning ignition timing but rather just setting the base timing. Once this is done the actual ignition timing table would need to be correctly optimised to suit the engine.
This story isn't meant to be a step by step 'how to' guide on setting base ignition timing. The aim is to educate people about what base ignition timing is, and the importance of getting it right. There's a bit of a limit on what level of detail we can really get into here unfortunately while still staying interesting and relevant to the greater SH community.
abezzegh87 this isn't for everyone and you're right, getting it wrong can become expensive really fast. While plenty of people will just leave this to a professional tuner, there are also a lot out there in SH land who are interested in learning how to do it themselves, or alternatively just those who are fitting an ECU and then driving their car to a tuner to have it tuned - In this case setting the base timing is a critical step.
I'm one of those guys looking to make the jump from suspension and alignments in my driveway to engine-related stuff, so the baby steps you feed us are appreciated. There's enough material out there to take what you give us and fill in the details, but I like the way the Knowledge Boosts are just general overviews, which give me the questions I need to ask more detail about on more technical sites.
xAsymmetric I'm happy to hear you're enjoying the series
Thanks for that Andre, Good read and helpful.!
A question. When running a dizzy this still all applies! But what does it mean when you move the dizzy and the base timing on the timing mark changes in relation to the ecu...
Andre, I'm kind of jumping the gun to the next article, but, in respect to fuel pressure, is it necessary to route a vacuum source to an aftermarket FPR on a naturally aspirated engine?
As someone who is looking into the more mechanical side of things after originally wanting to go into design, I'm glad that these Knowledge Boosts look to be here to stay. Its enough info to give you the basics and start coming up with your own questions. Every time one of these pops up on SH its a must-read for me. Definitely keep it up!
Dimitri A If the car has a factory FPR and it references the Manifold then yes you should. But you can set it up as constant pressure as well but you must configure that in the ecu. Vacuum reference is usually the better way to go but its not required.
Andre Simon fair enough and thank you for responding to my comment. I appreciate your guys contributions to SH and I'm sure many other readers do.
tunerguy21 I'm happy to hear you're finding them useful
Dimitri A In a typical, relatively standard engine then yes it is normal to have the FPR referenced to manifold pressure. It's not essential however and leaving the regulator referenced to atmospheric pressure will have the fuel system replicating a return-less system. This is also what I'd recommend for an N/A engine with itb's or wild cams.
TcFxGt4AGE glad you enjoyed the article. There are two important aspects to a distributor ignition system. In most ECUs you will still have the option to advance/retard the timing offset as I discussed in the story, but you can also achieve the same result by mechanically moving the distributor.
When you are setting up a distributor ignition system you need to make sure that the base timing is correct, but you also need to make sure the rotor arm is correctly aligned with the output post for whichever cylinder is firing. If the rotor alignment is incorrect you can end up with cross firing inside the distributor cap.
John Key NZ no problem mate
It's not that hard, or complicated, just time consuming.
Advance timing in given load/rpm areas untill knock(pre-detonation) occurs, then in the areas where you have knock, retard timing 1-2 degrees. Or you have the car on a dyno and have set the timing to where you have the most horsepower at a given timing, without having knock. And hat is timeconsuming.
ive played around with settings like these in Riccardo WAVE...impressive to see how much the performance is effect by ignition timing!
RickardAngeria Firstly I'll assume what you are referring to is tuning the ignition tables which is very different to what the article is discussing - The article is talking about setting the base ignition timing. As I mentioned in the article, this MUST be done PRIOR to tuning the ignition tables.
Secondly your advice on how to optimise ignition is a little off the mark. In many instances it's not possible to make an engine knock regardless how much ignition timing you use, so recommending to advance the timing until knock occurs isn't useful advice. A proper load bearing dyno is the only way to accurately optimise the ignition timing (unless you're fortunate enough to have an in-cylinder pressure transducer).
Lastly I need to clear up a couple of terms you've used - Knock and detonation are different names for the same abnormal combustion event. Pre-ignition however (i'll assume that's what you meant since pre-detonation isn't a thing) is very different and caused by a different set of circumstances. Detonation or knock occurs after the spark event, where as pre-ignition as its name suggests, occurs before the spark event.
I'd suggest signing up for our free 6 part series of lessons as I'm sure you'll find the information very valuable. The link is at the end of the article.
You guys have severley misrepresented concentric wire twisting. It is purely cosmetic and does not provide any perceived performance advantages. Quoting F1 engineers is just plain wrong and unprofessional.
Yours sincerely,
Prossional aerospace wiring expert of 25yrs.
SimonNimmo did you get the wrong article by chance? The article you've commented on has nothing to do with wiring so I'll assume you're referring to this - http://www.speedhunters.com/2015/09/knowledge-boost-tackling-your-wiring-nightmare-part-1/
I haven't misrepresented anything, and I didn't quote any F1 engineers in that article. The reasons for concentric twisting are pretty straightforward and well explained in the article so I'm not going to delve into them again. I didn't invent concentric twisting and I'm not making up reasons for its use - You can choose not to believe them but that doesn't make them any less true.
While I appreciate there are many similarities between the aerospace and professional motorsport industries when it comes to wiring, there are also significant differences and as always it's horses for courses.
Hi Andre,
I agree the reasons are straight forward, & those are purely cosmetic.
Im sure most in the trade would agree that tightly bundling wires lowers electrical performance with drawbacks such as increased heat, increased voltage drop and the like. Concentric twisting is a method borrowed from structural wire cable manufacture. When used with electrical cable it results in less flexibility of the loom and increased risk of inner cable (of the concentric arrangement) damage, cracking insulation etc, when the loom us flexed in high movement areas.
The theory behind using the concentric twisting method doesn't stem from any of the benefits cited in your article. It's primary reasons are loom rigidity, thus less securing points and therefore component weight are required, and cosmetic.
In practice the increased cost and decreased performance and reliability far outweigh any of the perceived advantages of this method. Even the weight advantages are easliy outweighed because the loom often includes fillers to enable the shape retention and vastly increased wire lengths. Nobody likes paying for unused inclusions and baseless benefit claims.
Lastly the claim of smaller cross sectional area of the loom is just rediculous! Even a novice engineer would tell you that.
As an apprentice Andre, do yourself a favour and ask these questions of your mentors.
Regards,
Simon
SimonNimmo I assume you're aware that concentric twisting is the technique used to construct the looms in just about every form of professional motorsport? While cosmetics probably rate somewhere on the scale of importance, do you actually believe that every harness technician in the industry is using this technique purely because it looks pretty?
As far as flexibility goes hopefully the attached picture is a useful illustration. Try doing that with a DR25-covered loom that isn't concentrically twisted - It doesn't work. Not only does it not work but bending a conventional loom actually places more stress on the wires when compared to a concentrically twisted harness which is counterproductive for reliability.
I'd suggest re-reading my article - Nowhere did I claim concentric twisting results in a smaller cross sectional area. I said concentric twisting provides a loom 'a very small cross sectional area'. A bundle of 22 AWG wires will have a minimum cross sectional area and concentric twisting can't reduce this. It does however consistently achieve this which is seldom the case with haphazardly arranged wires jammed through some DR25 in my experience.
You're entitled to your opinion and of course you're free to construct your own wiring harnesses in whatever manner you prefer. Likewise I'm sure professional motorsport teams will continue to concentrically twist their harnesses as they have for decades.
Hi Andre,
Thanks for your reply.
I've been wiring in the aerospace industry for over 25 years and could probably amaze you what can be achieved when using the proper techniques.
Take for example your pics of "soldered", or for those of us in the know "tinned" wires. All of those are a massive fail done with poor techniques (excessive solder, wicking, flux inclusions to name a few). Work like that will fail of course, as will poor crimping methods. Crimping is mostly an economic decision verses the skills needed to acheive high reliabilty solder techniques.
However i will take on board what your saying and will look forward to seeing if any of those industry professionals you speak of debunk my statements.
Please keep in mind that it is interesting to note that the guys that are posting with the same views aren't novices tho?
What i would like to also add is the question, how many times at the race track do you see everyone follow what the winner is doing because they think it will make them win too?
Nothing beats well founded engineering in the long run hey? Fads come and go as they say. Haphazardly arranged wires stuffed into heatshrink is hardly a professiinal method. The reason for your smooth bend is the 2.5:1 ratio shrink. Try doing that with 4:1. The concentric twist will prove to be a hinderance in that instance
I would love to see a technical paper on the advantages of concentric twisting. Have you ever seen one Andre?
SimonNimmo clearly we aren't going to agree on this subject, so rather than create the longest thread in SH history on an article that has nothing to do with wiring and hence isn't going to be useful to anyone else, here's my suggestion:
If you ever get tired of your 25 year aerospace career and decide to apply what you know to rewrite the current status quo in motorsport wiring construction, get in touch. I'd love to see what you produce and would be very happy to document the advantages here for the world to see.
You can contact me at andre@hpacademy.com
Hi Andre,
I am happy to produce high end harnesses for any motorsport genre from our workshop conveniently located just north of Brisbane QLD, close to lakeside raceway.
We have experience in drag racing, truck racing, off-road rally, street machine, GT40 replica and many more.
All harnesses come with cad schematic drawing support, warranty and can be installed for you also.
Send any enquiries to:
motorsportelectrics@gmail.com
Regards,
Simon.
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