Its the needles. The profile is not right for the engine and at steady throttle
you are going lean. Since it does not lean out on hard acceleration (which is
enriched by the damper), it is not a fuel feed problem, which is the only other
thing that could cause this. Just to be sure, check your fuel pressure and float
level settings, but I'll bet they are within specs.
Lots of folks are starting to run into a lean-out condition like this, even with
a stock engine and new stock needles. I am not sure why. We miked several new
needles to see if they were different from the older versions and they were
identical, within tolerances. Same engines, same carbs, same needles, but now
the cars are running lean??
All I can think of is that something they have done to the gas is causing the
problem. I know that on my FI cars a change in gas formulation is very
noticeable. When I drive down to SoCal, my cars always run worse on CA gas than
they do on the OR gas. We get a different formulation up here. So I am wondering
if one of the newer additives, like say the MBTE or other "oxygenators" is
causing the fuel to act "leaner" somehow. Any chemists on the list that want to
try and answer this? Anyone else got any ideas?
Nathan Ruffcorn wrote:
>
> Mike-
> I have always experienced the same problem on my 2L (N17 needles). Mine
> will keep power while aggresively accelerating, but if I hold a steady
> speed, it tends to surge. I hate to do this, but if I'm on the highway I
> pull the choke out part way. You may try this as it will help determine if
> you are truly getting enough fuel. The choke cleans it right up, but I hate
> the chance of running too rich and washing my cylinder walls. I've
> experimented with richening the carbs dramatically, but I get the same
> result (also required radically increasing idle speed setting to run-not too
> practical). At first I thought the needles were causing the lean condition,
> now I'm not so sure. Any thoughts?!
> BTW, manifold vaccum is good through all RPM's.
>
> Nathan
>
> ----- Original Message -----
> From: datsunmike <datsunmike@nyc.rr.com>
> To: Datsun Roadster List <datsun-roadsters@autox.team.net>
> Sent: Thursday, May 31, 2001 8:08 PM
> Subject: Runnin Outta Gas
>
> > Well I finally took my car out for a spin and it was great! I haven't
> driven
> > my car in over a year and I forgot what it felt like.
> >
> > While the car generally runs well I have no power above 4K RPMs. It feels
> > like it's running outta gas. I have 2L carbs with N17 needles and one1/4"
> > fuel line supplying both carbs from the Facet electric fuel pump to the
> > carbs. Do you think this could be the problem? I am not running lean as if
> I
> > richen it my idle deteriorates.
> >
> > Thanks for any help you can provide.
> >
> > Mike
--
Marc Sayer
82 280ZXT
71 510 2.5 Trans Am vintage racer
|