DeusEx Posted January 6, 2005 Share Posted January 6, 2005 Hey guys, I noticed a while ago that because of my weber manifold i dont have anwhere to attatch my vacum advance. Now that im working more on rev matching and stuff for down hill racing (if you could call it that) i notice that the carbs do not respond well to a quick burst of fuel and so the down change is screwed. Is this a result of not having vacum advance? If not is it hindering me not to have it? ANd how can i hook it up if i need it? Im not fussed on tapping a screw into the manifold as i dont want to disturb the air flow. Thanks guys Quote Link to comment Share on other sites More sharing options...
datsunlover Posted January 6, 2005 Share Posted January 6, 2005 I don't run my vacume advance, and havn't had any problems. Well, I DID have similar issues at first, but playing with the carb's and advance fixed it. By advance I mean just setting LOTS of intial advance by turning the dizzy. I had an idle around 950-1050 rpm, and it was a bit hard to crank on startup, but nothing major.. always satarted, and was very quick to rev whenever I taped the throttle to match revs/take off. Quote Link to comment Share on other sites More sharing options...
Tim240z Posted January 6, 2005 Share Posted January 6, 2005 It's for fuel economy during light throttle cruise.... Quote Link to comment Share on other sites More sharing options...
DeusEx Posted January 6, 2005 Author Share Posted January 6, 2005 Ah thanks Tim, thats the answer i needed. Lover, how much advance do you run, when i bought it i had 45 degree but a mechanic friend of mine turned it down to 20 something. Without the advance should i turn it back up? Quote Link to comment Share on other sites More sharing options...
JMortensen Posted January 6, 2005 Share Posted January 6, 2005 Rev it to 3000 rpm then and set it at 35º and ignore what it is at idle. Quote Link to comment Share on other sites More sharing options...
DeusEx Posted January 6, 2005 Author Share Posted January 6, 2005 Regardless of setup and carb tuning/numbers? Quote Link to comment Share on other sites More sharing options...
datsunlover Posted January 7, 2005 Share Posted January 7, 2005 Yah, I'd crank it back up a bit. I have mine set at about 30*. Any more, and I found I'd get 'run-on' when I shut in down. It would sort itself out afer a few seconds, but it was anoying to shut off my car and sit there for a sec while it went "cha CHG cah CHG.. pop." Part of my problem (I think) was a slightly bent dizzy shaft though, so it would 'bounce around' a bit. and I never had the carbs synced properly, so that could have been doing weird things.. Quote Link to comment Share on other sites More sharing options...
preith Posted January 10, 2005 Share Posted January 10, 2005 Thankfully I have a DIS now, but on my last car I searched in vain for someone who sold different distributor springs (recurving), which had less advance at idle and more later, maybe more so than 35 degrees as well. EDIT: I guess I could have searched first: http://forums.hybridz.org/showthread.php?t=76632&highlight=distributor+recurving Quote Link to comment Share on other sites More sharing options...
JMortensen Posted January 10, 2005 Share Posted January 10, 2005 preith, what timing curve are you running with your DIS setup? I've heard one other person (also with a very high compression race motor) suggesting a really wide advance sweep that goes way up in the rpm range as well. Everyone else I've ever heard talk about recurving, and this is regardless of the type of engine, says start at around 20º and end at the mid 30's at around 2000-2500 rpm. IME my car doesn't accelerate nearly as well with the timing cut down on the low end, it definitely has better throttle response with ~20º at idle. Quote Link to comment Share on other sites More sharing options...
preith Posted January 11, 2005 Share Posted January 11, 2005 preith' date=' what timing curve are you running with your DIS setup? I've heard one other person (also with a very high compression race motor) suggesting a really wide advance sweep that goes way up in the rpm range as well. Everyone else I've ever heard talk about recurving, and this is regardless of the type of engine, says start at around 20º and end at the mid 30's at around 2000-2500 rpm. IME my car doesn't accelerate nearly as well with the timing cut down on the low end, it definitely has better throttle response with ~20º at idle.[/quote'] It's an Electromotive HPV-1. It would be easier to explain with the graph that's in the instructions, which are here, see page 15 of the pdf file: http://www.directignition.com/pdf_files/hpv1.pdf But basically most of the advance occurs by 3000rpm, and from there to what ever value you have set at 8000 is linear (+or- 10 degrees). IMHO too many people don't put enough time into the timing, or are hampered by the stock distributor. Also there's a guy named Ken Bonneau in the SCCA Milw. region who I heard was running as much as 50 degrees advance on an IT motor! Quote Link to comment Share on other sites More sharing options...
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