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I want to understand engine tuning better.

Is there an idiots guide kinda book out there that i could read and understand it all better?

Thanks.
 

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I don't know of an "idiot's guide" - this stuff is generally beyond the capability of idiots to accomplish. I don't know what level of experience you are coming from, so I'll just throw some stuff out there.

There are textbooks on internal combustion engines - Gordon Blair's book comes to mind but I don't know the title of it and I don't have it myself. These seem to fall into two camps: those dealing with general principles and theory, and those dealing with extremely advanced theory - combustion science, etc. I don't have any of these other than my university thermodynamics text (Reynolds and Perkins) - and that one is absolutely useless for purposes of "tuning".

An understanding of modern fuel injection systems is essential. You can fish stuff out of the internet, or you can read the Bosch fuel injection handbook. That book explains how fuel injection systems work. It does not go into the details of ECU coding, etc.

I have a good friend who is a perpetual student, and he's been studying theory of internal combustion engines for years. He has fed me a good stream of technical papers - many of which have mathematics in them that are far over my head, but I get the general principles.

An engine is an air pump. One key to tuning is to get air through the engine as efficiently as possible, and the other is to make the best use of it possible. These days, there is no substitute for engine simulation software. I've played with the Lotus Engineering freeware demo software. User interface SUCKS and there is next to zero help available in how to use it. But, for tuning a little single cylinder engine that I have ... it has still been invaluable. http://www.lesoft.co.uk/ Good luck figuring out how to use it!

Other websites that are some of my faves:
http://speedtalk.com/forum/ (mostly drag racers hot-rodding V8's but there are others)
http://www.gofastnews.com/board/performance-racing-forum/ (not very active, but the write-ups are still worth reading)
 

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Suck, Bang, Blow
 

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I want to understand engine tuning better.

Is there an idiots guide kinda book out there that i could read and understand it all better?

Thanks.
If your asking a question like that your probably gonna save alot of money by letting professionals work on your vehicles. Tunning takes many years of exp. and finding the right person to teach you. Many people claim they can tune an engine but very few actually know what they are doing, it's not easy and it's along road ahead if it' something you are really interested in.
 

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Yeah, sounds simple, but it ain't.

One thing you'll quickly find out, is why the original engine manufacturer builds things the way they do. Another thing you'll quickly find out, is that there is far more to this than buying parts that make certain claims and bolting them together. A fairly large percentage of aftermarket parts don't work as advertised - period. Another fairly large percentage can only work when matched very carefully as a complete package with other parts.

My 125cc single is restricted by the stock camshaft (and the rev limit). According to the engine simulation software, nothing works better on the intake side than the stock intake runner, throttle body, and airbox, the only modification being to remove the noise-reducing snorkel. Nothing works better on the exhaust side than the stock, incredibly skinny header pipe and catalytic converter housing but with a different tailpipe, and it was extremely difficult to find a configuration that worked better than the stock one. Aftermarket exhausts that all have bigger diameter header pipes and no catalytic converter housing ... make less top end power and less midrange.
 

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For me, I would like to know more about tuning so that when i bring it to the tuner i have a better idea of what they are doing.
 

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The usual power-commander tinkering I would describe more as "calibration" rather than "tuning" but even with that, it can range from simple to complex, and there are right and wrong things to do.

What usually happens is that someone finds/downloads/whatever a map for your bike that most closely matches your configuration, plonks that into the power commander, maybe does a dyno test before and after, and as often as not, calls it good. Pluses: cheep, fast to do, no waiting, people can afford it. Minuses: you are subject to the whims of whoever originally made up that map and whether they did it right or wrong. If the map was done PROPERLY and the configuration is somewhere near what you have, this is the best bang for the buck for most people.

The next most common thing is that you go to a dyno tuning place that has what is called "tuning-link" and exhaust gas analysis. In one full throttle dyno pull it measures the exhaust gas and makes a corrected map and that gets downloaded. The good: cheep, fast to do. The bad: doesn't do a THING about part-throttle operation (or if they do it, it often happens wrongly - more later), and often the results are sub-optimal because this is being done on an inertial dyno. There is a time lag between certain operating conditions existing, and the reaction of the exhaust gas analysis equipment. I know this is what Dynojet has, but it's not really the right thing to be doing.

The problem is that "real" EFI calibration is something that most people are not willing to pay for. You do it on a load-control (water-brake) dyno. You establish certain conditions (e.g. a certain throttle position and a certain RPM) and then you vary fuel delivery to get it in the ballpark, then you vary ignition timing to get the highest torque reading, then you vary fuel delivery again to confirm it, etc. You do this over the full map - e.g. every combination of throttle position and RPM. Needless to say, this can take quite a while!

Then there is another complicating factor that most "tuners" don't consider.

At wide-open throttle, it's obvious that the rider wants maximum power (i.e. maximum torque output at that RPM). The optimum ignition timing coincides with this objective. The output torque is easy to measure. This is not a problem.

The big problem, and which most "tuners" don't get right, is the part-throttle operation. At part throttle, the rider is not asking and does not want maximum possible torque output. What's actually wanted in those conditions, is smooth throttle response and minimum fuel consumption (at an OEM level, emission considerations overrule this but aren't completely inconsistent with those objectives). Brake specific fuel consumption is harder to measure, because at a given RPM and throttle setting you have to measure both the output torque and the fuel consumption. On a fuel injected engine, you can infer fuel consumption from injector pulse duration.

Anyone who tells you that they are looking for a set air/fuel ratio over the full RPM and load map, is doing it wrong. It will frequently be found that full throttle wants to be set to the maximum-power ratio (with gasoline, frequently air/fuel 13:1 give or take) but at part throttle, best BSFC and driveability will frequently be on the lean side (15.5:1 - 17:1). And no, you will NOT burn a valve or piston by doing this as long as you stay clear of detonation - which doesn't happen as much at part load anyway. The heat load on the pistons and valves is lower at less than full load, so there's nothing wrong with going lean in that range (and it will be easier on your wallet, and won't foul spark plugs, and won't carbon up rings, and won't wash oil off cylinder walls the way a too-rich setting will.)

I've only done full recalibration jobs on a carbureted engine with the assistance of a wide-band air/fuel ratio gauge - in my case, I did my track bike Yamaha FZR400, and it worked out so well that I did my spare bike, same model but street registered. Full throttle is 13:1 give or take, and on the street bike I managed to achieve slightly lean of stoichiometric (15:1 to 17.5:1) over the full range of cruising conditions from 40 to 120 km/h. Throttle response is better than it has ever been, and fuel consumption was cut from 6 L/100 km to 4.4 L/100 km. It's got a little lean stumble at moderate load while the engine is warming up, but after it has been running for a couple of minutes, it's perfect.

The combination of settings required to achieve this was something I would have never hit without the gauge in hand. Pilot jets are actually richer than stock, idle screws a little leaner to compensate, but this allowed the needles to be one groove leaner than was possible with the stock pilot jets. Main jets are one size leaner than stock on the track bike and stock on the street bike (the setups are not identical - the track bike has different camshafts). Richer is not always better, that's for sure.
 

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Discussion Starter #9
If your asking a question like that your probably gonna save alot of money by letting professionals work on your vehicles.
Nope that isnt my aim. Im looking to get some basic theoretical knowledge.

Really good info there GoFaster, thanks. Rep sent.

Im still looking for a book as i prefer to read from a book than trawl thorough the net for this info plus there are a lot of people on the net who arent the most reliable sources.
 

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Really good info there GoFaster, thanks. Rep sent.

Im still looking for a book as i prefer to read from a book than trawl thorough the net for this info plus there are a lot of people on the net who arent the most reliable sources.
:iamwithst:+1::+2: i couldn't agree more with everything above:thumbsup:
 

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I'd very strongly recommend the Kevin Cameron 'Sportbike Performance Handbook' ; an excellent source of knowledge, technical enough without being too indepth, and laced with interesting anecdotes. All-round, a great read.

And I agree completely, most informative and interesting responses from Go-Faster - thanks !

Cheers,
Brian
 

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If you want books, here are a selection of books and technical papers.

First, the aforementioned Professor Gordon Blair. Take your pick.

http://books.sae.org/author/1073416002

and if you can only pick one, make it this one ...

http://books.sae.org/book-r-186

The other one is the Bosch fuel injection handbook. Even if your vehicle doesn't have a Bosch fuel injection system ... Bosch is the grand-daddy of modern fuel injection systems. All modern fuel injection systems - gas or diesel - have been developed (copied?) from systems that were first produced by Bosch. They all work in the same manner.

http://www.bentleypublishers.com/isbn/9780837603001/index.html
 

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Uhhhh, ok.
 
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