davebo Posted January 31, 2008 Posted January 31, 2008 OK here's a really basic question. On standard throttle bodies with the engine at idle speed, should the throttle be open a little, or is air supplied to the cylinders by a bypass arrangement which is normally integral to the t/bs ? Do motorbike and car t/bs work in the same way ? Thank you. Quote
stu999 Posted January 31, 2008 Posted January 31, 2008 It depends A TB setup normally employed on a Westfield will usually require the throttle butterflies to be adjusted to obtain the required idle speed. However, it is possible to fit a valve that is contorlled by the ECU which allows air to bypass the butterflies. This allows the ECU to control the idle speed, rather than a mechanical fixed adjustment. Finally, on aftermarket TB's such as Jenvey, each individual TB usually has a 'fine adjustment' to allow the flow of air to be accurately adjusted, or 'balanced' for each cylinder. However, this facility should not be used to actually adjust idle speed. In theory at least, one of the 'fine adjusters' will not be touched if tuned properly... A TB is merely a tube with some means of controlling the airflow. Old carbs can be made to work as TB's. Some bike TB's are a little more complicated though, but many can be used as a cheap alternative to the aftermarket choices. Handy if you dont mind a bit of fabricating... Quote
davebo Posted January 31, 2008 Author Posted January 31, 2008 I've been looking at Jenvey after market t/bs and also bike t/bs. I have some bike t/bs and they seem to have all sorts of extra bypasses. I was expecting to end up blocking the extra bypasses up. So i guess I can proceed with this, and then set the idle speed with the mechanical end stop for the butterflies ? Quote
fatbaldbloke Posted February 1, 2008 Posted February 1, 2008 Fairly sure the early 600 GSXR throttle bodies (one of the favourites for conversion) are all set with the butterflies. Quote
Jenko Posted February 1, 2008 Posted February 1, 2008 I'm in the process of doing a bike TB conversion (GSXR600 TB's) - on each TB there are two connections for 'vacuum tubes'... As I understand it, when fitted to the bike all the TB's are connected together via tubes, the center of which 'I think' goes to a fuel pressure regulator (but really not sure on this)...The others are blanked with the exception of one that is used for the MAP sensor....... I've also been thinking about the idle, and was wondering how much part the vacuum tubes will play?..... Quote
fatbaldbloke Posted February 1, 2008 Posted February 1, 2008 QUOTE As I understand it, when fitted to the bike all the TB's are connected together via tubes, the center of which 'I think' goes to a fuel pressure regulator (but really not sure on this)...The others are blanked with the exception of one that is used for the MAP sensor....... I'm fairly sure it's the other way round - at least it is on my car now! The common tube goes to the MAP sensor, this gives you a much smoother signal, and the single tube, which as I recollect is off TB no.3 goes to the fuel pressure regulator. As these are all vacuum tubes and don't, or at least shouldn't, see any airflow they will have no part to play in the actual idle setting. Quote
Jenko Posted February 1, 2008 Posted February 1, 2008 As I understand it, when fitted to the bike all the TB's are connected together via tubes, the center of which 'I think' goes to a fuel pressure regulator (but really not sure on this)...The others are blanked with the exception of one that is used for the MAP sensor....... I'm fairly sure it's the other way round - at least it is on my car now! The common tube goes to the MAP sensor, this gives you a much smoother signal, and the single tube, which as I recollect is off TB no.3 goes to the fuel pressure regulator. As these are all vacuum tubes and don't, or at least shouldn't, see any airflow they will have no part to play in the actual idle setting. Ahh yes...it could be that way around.......So, what did you end up doing with your Vacuum tubes - If I recall, you are using a TPS for the load bins and not MAP......Have you simply connected all tubes together and blanked off the end and the other vacuum ports?, or just blanked all ports?........ Quote
fatbaldbloke Posted February 1, 2008 Posted February 1, 2008 Ahh, firstly mine has one vacuum port from bodies 1,2 and 4 and only 2 ports from TB number 3. The single tube on mine is connected to the vacuum port on the top of the Power Boost fuel PRV. There's been some debate on the forum of late whether you should use this or not. I think the main conclusion was that whether you connect it or not seems largely immaterial provided you have to set your ECU fuelling table up in the mode you're going to run. The other 4 linked pipes are connected back to the map sensor in the megasquirt, I use it for the accelerator enrichment trigger (which I have also set to rpm based) as it gives a really crisp signal when you crack open the throttle. The signal in mine is really smooth and I haven't used any mechanical damping at all but I know of a couple of guys I've helped who have got spikes on the MAP signal for each engine cycle large enough to trigger the AE which of course isn't what you want. In those cases I've advised them to just use tps for AE trigger. I would connect it up and see whether you get a decent signal or not, it also serves to blank them off from atmosphere. Can't do any harm. Good luck, any idea when you're going to have yours running? Ian Quote
Jenko Posted February 2, 2008 Posted February 2, 2008 Hi Ian, Still waiting on the TB adaptors, and the fuel rail to be drilled.....But most of the things are done......Fuel system installed (using a swirl pot), Wiring loom made up, TB's all spaced and ready to fit...... I'm hoping to at least get the car started during Feb, then the hard work starts....THE SETUP!!..... At which point you willmost likely get a barage of emails Cheers. Paul . Quote
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