Jon Steiger wrote:
> On Mon, 14 Feb 2000, Shane Moseley wrote:
> [...]
> > > There is no MAF conversion for our
> > > engines(nor is any probable). The best you could get at this time is
> > > custom programming to suit the mods you have.
> >
> > I disagree big time here. It is true - as we all have seen - that custom
> > programming can better suit the mods you have...BUT its so dang costly! (and
> > legal? I dunno bout that) $400-$600 every time I decide to mod my truck??? No
> > Way! Just buy an aftermarket system ($400 on up if you shop Ebay and the swaps)
> > and make the changes yourself everytime you mod it. If you really want the cats
> > arse - look into FP-performance's SEFI8LO system from the Fel-Pro people. That
> > system is truly awesome (read: costly 8-)
>
> Shane,
>
> Do you have any info about the SEFI8LO? I first heard about it in a
> magazine that someone (Peterson?) did about fuel injection, and I knew
> immediatly that its exactly what I've been looking for.
>
Not much more than that. That particular magazine was chock full of excellent EFI
info wasn't it? I've seen other rags rant and rave about the SEFI8LO but not much
more info than that issue you speak of. Most people cant possibly comprehend the
benefits to dialing-in any air/fuel ratio for each individual cylinder for any rpm
(and this is just a small part of what this system can do). Not to mention what it
can do with power adders like N2O. This is truly remarkable. Light years ahead of
ANY previous EFI system.
>
> Unfortunately, I haven't been able to figure out exactly what is
> going on with it. It seems like it was developed by a couple of people,
> and then was bought by Fel-pro? But the last time I checked, the demo
> program on their web site still listed the old company's name???? I've
> been a bit wary of it for that reason. I want to be sure I can get
> support and such.
Was it in Ashland, MS? Believe me - you dont have to worry here. LOTS of the big
guys in IHRA and NHRA are trading in their existing systems and buying into SEFI8LO.
> Probably the biggest reason I like the SEFI8LO is
> the fact that it can use a wide range O2 sensor to run at closed loop
> 100% of the time. I love that you can just plug in a target A/F ratio
> and the computer will do all the work for you. Although I do plan
> to plug in some sane static values, that feature alone will probably
> save me a load of cash since I don't need to tune on a dyno. For my
> personal situation, if a system can't do closed loop at all throttle
> positions, I'm not interested, because I won't be able to afford the
> dyno time. I want something I can tune at home, by myself.
Closed loop is nice if you can control everything for sure. Closed loop around 14.7
A/F sucks tho 8-)
>
> I have heard rumors that Accel has come out with a system in their
> DFI line that will do 100% closed loop also, but I haven't been able to
> dig up any solid info yet.
I have read about that one a little also. It still is orders of magnitude behind the
SEFI8LO system tho.
>
> By the way, the wide range O2 sensors are pretty expensive in general,
> but back when I was researching the SEFI8LO, the general consensus was
> that it used a sensor from one of the Honda VTEC motors, which was set
> up with a wide range ("lean burn") O2 sensor. Since that sensor was
> mass produced, it can be had for $130 or so. Still expensive, but
> a bargain when you compare it to $600-$800.
>
> I *will* be using an aftermarket EFI system on my Dak; the only
> question is when will I be able to save up enough money? :-)
> (I'm hoping to keep the total cost below $2K. If I can do it for
> $1K, I'd be ecstatic.)
>
OK - here it is - how about this theory: I'm not gonna go into much detail about the
existing system - suffice it to say that it spends like 90+ percent of the time in
closed loop (around 14.7 a/f ratio for emissions sake). We only get open loop when
cold (first minute or so of operation) and WOT. So 90+ percent of the time the O2
sensor is controlling almost EVERYTHING. This is what kills our mods - for example,
if at 2500rpm with some MAP, some temp, etc. the injectors are pulsed for 3.5ms
(guessing - bear with me) in order to get to the "magic" 14.7:1. Now I add 24#
injectors and back to 2500rpm with same MAP reading, same temp reading, etc. the
injectors are now pulsed for 2.9ms to get to the magic 14.7. Did I gain anything? No
- same amount of fuel. OK I change the fuel pressure - same results, less time open.
Ok so we start changing the breathing capabilities with heads, cam, supercharger.
This helps and feels stronger during closed-loop but at WOT what happens? Jon, I know
you and Will and TomF and several others know (yes, I've been lurking that long 8-)
but for the sake of the list I'm going thru all this - bear with me 8-) At WOT the
computer goes open loop and ignores the O2 sensor reading instead the built-in tables
for what that injector pulsewidth should be at 2400rpms, same MAP reading, same temp
reading, etc. Well, now we risk going lean because it pulls that factory 3.5ms (or
whatever) but because we have enhanced the breathing so much - thats not enough fuel -
burn city - oops! Damn computer is limiting us.
Ok on to the theory - suppose we put in a 160 thermostat (or whatever is less than the
magic temp) which wont allow the engine to reach the magic threshold that tells the
computer that it has warmed up now - its ok to go closed loop. O2 sensor isnt a
problem now and ALL the time we are reading from that built-in map. Built-in map -
thats constant! Using EGT sensors or a wide-band O2 sensor - cant we basically make
the motor do pretty much ANYTHING we want? Just up the fuel pressure or bigger
injectors to match the extra breathing at ALL rpms? Sounds good - at least part of
it. That dang 160 degrees stands out like a sore thumb tho. Cant imagine much power
with a cold motor. Have you noticed that some of those 12s trucks run 160
thermostats? Will this work or Where is it falling apart? Any ideas?
Enjoying this,
Shane
-- '96 IndyRam w/lots of mods (mine) '96 IndyRam w/lots of options (wifes) - also a numbered (#142) "Track Truck" '74 Triple-Black Dodge Challenger Rallye 360 home-brew EFI R&D vehicle '68 Black Corvette Convertible 427 (For Sale)
This archive was generated by hypermail 2b29 : Fri Jun 20 2003 - 11:48:07 EDT