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Questions about Modifications

Discussion in 'Modifications and Projects' at netrider.net.au started by TheInineFour, May 17, 2013.

  1. Hey, new to this forum, hoping this is the right section.

    Anyway. I'm doing a Research Project for school and needed some help in regards to modifications to increase horsepower output. Don't really know much about it all, I've got a basic understanding of most from doing a bit of internet research.

    Would be good if I could get a few answers on advantages and disadvantages, along with maybe dyno charts to show the performance increase or decrease.

    If you've done these modifications to your bike was it worth the price you've paid to get that extra output?

    Links to pages would also be handy too :) I need as much information as I possibly can get.

    Cheers, Mike.

  2. What year school project is this and for what subject?
    What is the actual topic and what detail do you need to go into?
    Am asking this because my thoughts would probably go deeper than the level you'd need.
    What is your understanding of methods to increase horsepower and the downside of doing so?
    You can probably find dyno charts online for before and after modifications just from The google search.

    To give one very simple "modification" you might have seen mixture knobs on some race cars. Run rich and they get more power out of it but economy is reduced. Run too lean to get better economy and the risk is that the engine may overheat. Depending on your level of education you might be able to explain why. Turbochargers an superchargers are otherwise examples you might be able to explain.
  3. This is for a Year 12 Research Project, we've been given 6 months to collect research and then comprise it into a Folio. Wasn't sure whether to focus on purely motorbikes or widen it up to also cars.

    Topic is modifications to increase engine output. Within that I also look at how much performance has been effected, whether these methods are efficient. I also need to get some personal opinions from riders with these modifications.

    I know a little about Jetting/Jet Kits and changing the air:fuel ratio. Fuel Injection Remapping, to also change the ratio around, but not sure how much it differs from Jetting, apart from maybe remapping being more precise than Jetting.

    Compression Ratio I understand how it works, but I'm not sure on whether that is changeable.

    Installing aftermarket exhaust system gives more horsepower, but what is actually different about aftermarket and stock exhaust apart from weight, and what make aftermarket ones more effective than stock.

    Not sure of what disadvantages come from doing modifications. Apart from a lot more heat meaning better cooling.
  4. #4 NSSherlock, May 17, 2013
    Last edited: May 17, 2013
    Compression ratio can be altered by shaving down cylinder heads. The effect is to increase the peak pressure. Problem can be that the altered pressure wave and the combustion can get in synch and cause detonation instead of combustion. That can require a higher Octane fuel that has less tendency to detonate.

    A map is going to more tailor the mixture and ignition advance according to conditions whereas a rejet is more of a constant and only comes into effect when that jet is active. The map is (hopefully) going to respond to input from sensors. A rejet basically can't. it's just bigger. Why does bigger = more hp?

    Heat can be an issue but also when you consider efficiency consider the trade-off with fuel economy. For engines there are a number of different economies defined which you might look up.

    Ok, asking about exhausts - that can be complicated. It can be an art to design exhaust systems and most modified systems you'll see on bikes are more for noise and visual appearance.

    Basically and broadly, when you "modify" for horsepower what are you trying to achieve? You've got fuel with energy in it. You want to get as much of the energy out of it as you can. If you can cram more of it in then it ends up with more energy available to you. You want to get it in quickly and out quickly. You want to minimise the amount of "end gas" or leftover in the combustion chamber so it doesn't dilute the charge that is coming in. You want the engine to "breathe".

    Between getting the fuel in and out quickly there are also considerations of the way it flows into the chamber and how it might "swirl" or flow in the chamber and how the fuel/air ratio might vary within the chamber (too involved for your project possibly). That's all aimed at getting the most "complete" combustion you can. In your case "complete" refers to getting the most hp out of it.

    I'd think of exhausts as being a means to get the best flow out. they can go beyond that.

    Have you done any chemistry? Can you handle chemical equations? If you can then when you think of mixture and efficiency I'd be looking into the different equations involved for maximising the efficiency that will give you the most power and the efficiency that will give the best economy.

    I wouldn't limit myself to just motorcycles but possibly use a motorcycle as an example. Maybe you could start with an intro on 'how an engine works". Then go into modifications to make it work "better" which in your case is to get more hp. I don't know if you might be required to fill in that background for the reader or not. You need to target the project to the audience and if the intended audience are reader who may not know "how an engine works" you might need to briefly fill that in. Same applies with what I've said bout chemical equations. You can't give your audience a lesson in chemistry so you might need to present it so they can follow it.

    Important, I think, is that when you think of efficiency you need to consider all of the different types of efficiency that are defined for an engine.
  5. You'll probably find a free-er flowing exhaust & remap/rejet to suit the most common mods, plus remapping or rejetting to tune out the 'flat spot' common to a lot of bikes, often due to needing to meet certain emission & noise regs.

    Other than that, it's a pretty broad question really...
  6.  Top
  7. Although in principle the engines work the same way, in practice they are entirely different machines. I'd recommend just stick with motorcycles as many more riders are interested in their machines performance, than are drivers with their cars.

    The list of modifications can be short or long depending on how much detail you need & how thick your folio needs to be? Topic is very broad, so I'm guessing you will not be able to go into too much detail in any particular area.

    Ok this is just a little more detailed but still a huge topic in itself. Mapping is for fuel Injected (FI) bikes which are computer controlled. This is where the stock fuel delivery program or 'map' is reprogrammed /modified to inject more or less fuel at various engine RPM and throttle position. This is usually done by buying a plug in accessory computor such as 'power commander, EJK (electronic Jet Kit, juice box' etc which modifies the signal from the bikes computor to the injectors. These are usually only fitted in conjunction with a new exhaust and/or air filter, in order to fine tune the fuel system to suit the new parts.

    Jetting is for motorcycles which have carburettors. The jets controll the fuel flow, bigger jets = more fuel. There are usually three jets in a bike carb, but some have more. They usually have a slow speed pilot jet, a mid range needle jet, and a high speed main jet. Same as with an FI bike, they are usually only altered to compensate for modifications such as new exhaust or air filter.

    FI systems do not necessarily produce more power than a carbie, but they are more acurate & cleaner, meaning there is less wasted fuel and less emissions. This is why they are being utilized more by manufacturers to pass increasingly stricter emissions standards.

    It can be changed and there are a number of different ways to do this. A common way is to fit a piston which is either taller from pin to crown, or has a modified shape on its top. This allows you to easily convert it back to std if there are issues, by refitting std piston. Another method is to fit a thinner head gasket, which is also a non permanent modification. A permanant way to raise compression would be to machine metal from the face of the head or cylinder.

    There are many differences. The pipe internal diameter can be larger. They do not usually fit a catalytic converter. They remove any noise controlling butterfly valves. They can alter the primary pipe length, mid pipe length, muffler length, eliminate cross over pipe or change its position. The muffler is usually a less restrictive straight through pipe with no baffles. etc. etc.

    Disadvantages are dependant on modification. Noisy pipe can give you a headache on long trip, attract attention from police, annoy your neibours, increase fuel consumption. Expensive pipe may not be covered by insurance when crashed.
  8. The main disadvantages of doing engine mods are that it is addictive and that it then drives other, sometimes more expensive, modifications.

    A motorbike is designed as a "package" so, if you double the horsepower produced by the engine, you'll typically end up having to seriously upgrade the brakes and suspension to cope with the extra power.
  9. Then of course there is the frames capacity to handle the up spec engine.

    What about transfer of horsepower to the wheel and the big difference that sprocket size makes in final delivery? I don't know if it affects the horsepower at the wheel but pretty sure it affects performance in relation to take off and top speed.
  10. Aye, maduncle, the number of teeth on the front and rear sprocket can take a bit of time to work out, too.

    That was the point that I was getting at......
    mod the engine then you go round in a wee loop, modding the brakes, suspension, tyres, gearing, stiffening the frame, etc. etc.

    Then, when you get it all sorted out, you find some other way of extracting even more power from the engine, and off you go again.

    It can be fun if you can afford it and have at least one other useable bike. :)
  11. Important point you make there - if you are going to do it, make it a track bike, and keep your other bike(s) for the road.

    As in my next build - a vintage CB450 track bike with a custom modified and stiffened frame, monoshock swingarm, Earle fork front end, 180 degree reversed head, as many CB450 race engine parts as I can afford, and the removal of anything only required to ride it on the road (lights, blinkers, charging system, electric start, etc, etc).
  12. Maduncle said:
    "Important point you make there - if you are going to do it, make it a track bike, and keep your other bike(s) for the road."

    Actually, to be exact, I didn't make that point at all.

    We all have different ways of getting our jollies, and what appealed to me with my most modified bike was keeping it as a road going concern.

    There is/was more than a hint of sarcasm in that I could ride up to Pie in the Sky, listen to folk rabbiting on about how they managed to get three extra horsepower with titanium exhaust system and remapping on their 150+ horsepower sports bikes, and then say right, but I have 4 times the original horsepower on this bike.

    Come back and tell me when you can manage doubling the original power. ;)
  13. I accept that challenge.
    • Like Like x 1
  14. Afternoon Ladies and Gents.

    Been reading up on a lot of vintage bike build forums. I have come across a couple a fair few with completely different / modified areas of the bike ie super sports front end / swingarm on a vintage bike build. I was wondering how far structural modifications can go without a certification? Also what is involved in this certification? Must be a costly process.

    appreciate the reply's.