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Timing advance setting with Engine Management System



good info dan.
 now does anybody else have a headache after reading that much techinical 
info

 On 5/3/05, Dan Bubb <jdbubb@ix.netcom.com> wrote: 
> 
> For full throttle I think what you have is pretty close.
> Full advance by 2500 seems a little fast to me, so I'd lower the value at 
> 2440 somewhat.
> 
> Couple general comments about spark timing and setting up load points on 
> an aftermarket engine
> management just cause I can't help myself.
> 1. I don't think these engines need a huge amount of total advance at WOT 
> based on input from both
> TT and NGP. I would think 32-34 max would be good. Plus you have a higher 
> than normal compression
> ratio and that speeds up the burn rate meaning you need even less advance.
> 2. The burn rate in the combustion chamber varies with throttle opening. 
> More throttle=higher
> density in the chamber=faster burn rate. So, at partial throttle (cruise 
> conditions) you need to
> have more advance. So, you might try adding more advance in the lower load 
> positions. As an example,
> if your engine cruises at .5 bar/15"vac then you probably want to have 
> 12-15 deg more advance at
> that RPM point then you do at WOT for that RPM. In other words you want to 
> emulate the vacuum
> advance of mechanical distributors.
> 3. Engines are generally linear in their requirement for fuel or ignition, 
> but with some exceptions.
> One is around idle where some monkey business , mostly with the ignition 
> timing, can improve idle
> quality especially if you have wild cams. The second is engines with wild 
> cams tend to have weak low
> speed performance and at a certain RPM "come on the cam".
> The TEC II (and also Megasquirt) has 8 load and 8 RPM points. I would 
> adjust the RPM points so you
> have a couple close to the idle speed, and several around the RPM where 
> the cams kick in to handle
> the drastic change in fuel required there, of course one at your max RPM, 
> and last one or two in
> between those points.
> For idle, one at the desired idle speed, then one RPM point a few hundred 
> below that. This lets you
> put in the actual idle advance at the idle RPM and really bump up the 
> advance if the idle should
> falter some. So, say 6 deg across all load points at 1000 RPM and 20 deg 
> at all load points at 700
> RPM. Idle drops down, advance kicks in and helps to bump the idle back up.
> Let's say your cams kick in around 4000. If it's a big change in power 
> then you may want an RPM
> point at 3700, one at 4000 and one at 4300. The ignition requirements 
> don't change drastically when
> the cams come in (or maybe it just doesn't matter that much) but for good 
> drivability the fuel will
> change quite a bit and that's why you need a bunch of RPM points around 
> non-linear behaviour.
> Also, since you're running ITB,s I'd also bunch the load points towards 
> the higher end of the range
> especially if your using MAP (manifold absolute pressure) for load. Maybe 
> if you're running throttle
> position for load this would be less important.
> 
> I'd put in an ignition map here but the formatting will be all hosed. So, 
> if you'd like my idea of
> an ignition map LMK and I'll send you one in Excel.
> 
> And one last comment. You are going to run more than 7000 RPM?? I bet your 
> power peak will be that
> high and you need a few hundred RPM beyond that for maximum performance 
> through the gears.
> 
> Anyway, that's what I think. Most of this is based on experience with a 
> 2.0L 8V with ITB's and a 306
> cam using Megasquirt running to 8000 RPM.
> Hope this is clear for all that read this far.
> Dan
> 
> ----- Original Message -----
> >From: "Don Walter" <dswalterwi@gmail.com>
> >To: "Scirocco List" <scirocco-l@scirocco.org>
> >Sent: Monday, May 02, 2005 9:56 PM
> >Subject: Timing advance setting with Engine Management System
> >
> 
> >Okay with the TEC 2 I can set an 8x8 grid for the Advance based on RPM 
> and
> >MAP (manifold air pressure). I have a 16V 2.0L with Autotech Sport Cams 
> and
> >have looked heavily throught the Bently on an idea how I should be 
> setting
> >the advance table. As near as I can find the idle advance should be 
> around 4
> >to 8 degrees with the full advance by 2500 rpm as 13 degrees mor than 
> base.
> > Quote from Bently:
> >CIS-E rpm-dependent timing advance:
> >total timing @ 2500 rpm = measured base timing value (4 to 8 degrees 
> BTDC)
> >plus approixmately 13 degrees
> > In the TEC 3 grid I have it set on average as:
> >12 degrees at 816 rpm
> >17 degrees at 1628 rpm
> >34 degrees at 2440 rpm
> >36 degrees at 3252 rpm
> >36 degrees at 4064 rpm
> >36 degrees at 4876 rpm
> >36 degrees at 5668 rpm
> >36 degrees at 7000 rpm
> > 36 degrees total I am thinking about turning down to 28 degrees total.
> > Does anyone have any input as to how they have theirs set?
> 
> --
> Don Walter - Waukesha, WI
> 1986 2.0L 16V TEC 2 Black Scirocco (see progress at
> http://www.cardomain.com/memberpage/708939)
> 1986 2L 16V Toronado Red Scirocco (under repair)
> 1988 1.8 16V Toronado Red Scirocco (sold on 3/29/04)
> 1984 1.8 8V Pewter Scirocco (sold years ago)
> 1971 Karman Ghia (sold)
> 1969 Karman Ghia (sold)
> 1969 Beetle (sold)
> 
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