Dear Fellow Dubbers, I am currently converting my KR to run ITBs.... I am stump as to how and where to draw vacumn for both MAP and Brake. I am aware that some of you here has completed your conversions and I hope you would share. I can also run TPS instead of MAP but as my car will be a daily so it could stand in traffic so getting the car to idle properly is essential... Thanks for your time.
vacuum For the brake servo you need vacuum, tapping into one runner ( from throttle bodie to head) usually on inlet manifold, just find somewhere suitable and fit a hose tail, then connect to the brake servo with a proper rigid pipe, soft rubber will colapse with the vacuum. One tap into a single runner works fine for the servo even though at low revs the vacuum is pulsing like mad. Because of the one way valve in the pipe connecting to the servo the vacuum picks up just as well as the standard setup. No one ever finds a problem. As for a stable MAP reading for the ignition timing this is all together more involved, but not difficult. If you have a programmable ignition setup you will be able to get good results. Many resort to the TPS solution for engine load monitoring and really this might be best as ITB's usually have provision for mounting one. Check out the Megajolt/ autosport labs forum for some discussion on the subject. As a note VW with the 16v etc engine use a simple TPS to get a stable idle (and improved emissions), when the switch is closed the timing is stabilised, just on/off. When the throttle is pressed a bit the MAP comes into play
cheers f1steve. Your explanation is very clear, however will try to read the sites your recommended. I will be running Megasquirt, ignition and fuel, have you had experince with this before?
hi h2zero, I've no experience with megajolt apart from chatting with a geezer who used it for a mk1 diy turbo install, he was having some problems with the VE tables. However it seems a popular engine management system, and has got to be cost effective if you can program it yourself. Plenty of info on VW vortex forum, maybe someone will even share their base setup as a start. A stable idle when warm should be easy to achieve, it appears as though cold starting is the tricky bit. There's coolant and ambient temperatures to consider, these are highly variable over a relative short space of time, each setting has to be tested summer to winter, freezing engine to only left for a couple of hours. This can take a long time to fine tune. Remember the old manual chokes? out a bit in a bit, try getting a computer to do such an analogue thing!! Best of luck. The megasquirt FAQ on this forum should have most of the information you need. Just been on vortex forum and see you've asked question there as well. Good man, doing research before taking the plunge. Just to try and get back to your topic about vacuum, for the braking system there is NO pulsing to the pedal or the brakes themselves if you only tap ONE runner. I had expected otherwise when I first tried it, but its fine. Usually when you need the brake assistance the engine revs are quite high, any vacuum pulse measured with a gauge only becomes noticeable at low revs. The brake predal does become harder if you press it quickly and several times if the engine is only ticking over, but really this is not an issue. I'd recommend getting the megasquirt install running with a TPS and I'm sure you'll have no problems.
again thanks F1steve, my tuner wants to go Alpha-N as he has previously tune a similair engine set-up, anyway I would love to use the TPS. As for cold start well I am in Malaysia the tempreature here is hot and hotter so I don't think I will need to tune the car that many time .... Yes I am on the TEX too just wanting to find out as much as I can. ANyway thanks will let u all know how I get along.... cheers to all
