Re: EFI + MAC-14 maxing ataround 5k RPM

[antar at comcast.net]

I don't know how accurate     your O2 sensor is, but it does sound like an
ignition problem, especially     if you get it when revving in neutral. You may
want to pick up one of the     wideband o2 kits just in case. They're really
important for tuning in a     setup like yours. Does the ECU store any codes? I
would check the reference sensors and wiring,     and also the knock and hall
sensors. Intermittent sensors or wiring could     create noise and confuse the
ECU at high rpm. Oh, and is the megasquirt     close to the audi ECU? I think
megasquirt uses switched current to     regulate the injectors which creates a
LOT of noise.While you're in there doing the compression test, I would double
check the cam     timing. If the belt is off, this could move the power band
down.Last thing is I would change the oil now... I've heard it's good to change
it     after the 1st 500 miles on a new engine, because there's more wear than 
   normal use. Good luck.-Ameer
----- Original Message -----

>Date: Tue, 23 Oct 2007 09:41:43 -0400
>From:     "Ben Swann" <benswann at verizon.net>
>Subject: EFI +     MAC-14 maxing ataround 5k RPM
>To:     <urq at audifans.com>,    <quattro at audifans.com>
>Cc:     'Ben Swann' <benswann at verizon.net>
>Message-ID:     <011701c8157a$73484a50$0501a8c0 at swansong>
>Content-Type:     text/plain;    charset="iso-8859-1"
>
>I     think it is safe to rule out fuel delivery as a problem with my EFI?d   
 engine
>now that
>I have replaced fuel pump and assured getting     good fuel delivery at all
times.
>So back
>to the problem. I     think the ignition is dropping out at around 5000RPM,
but at
>a loss
>on     how to verify it and how to fix it. To review, the engine is completely
>rebuilt     MC-1
>with NF head being fed by Megasuirt V2.2 fuel injection through     42 lb
injectors
>? need
>to verify as these are Lucas Bluetops,     and might be 36#. 
>
>For ignition I am using the MAC-14     with dual knock sensors. I have the car
>tuned fairly
>well     by now in the below 5000 RPM range, and the engine runs great and
pulls
>hard     until
>it hits about 5000 RPM. It doesn?t matter what load and engine     can be
>free-revving and
>still reaches about a maximum of 5000     RPM. If I gun the engine briefly, the
>tach will
>hit 6K or     so, but gradually increasing RPM it will go to about 5300 RPM and
>seem     like it
>is hitting a rev limiter. Holding the throttle open, the     engine bounces ?
the
>RPM
>oscillates between like 4800 and     5400. Occasionally I have seen 6000 RPM
and
>holding,
>but     not able to maintain that result.
>
>Things that can be     automatically ruled out:
>Fuel pump relay ? this does not apply, as I     am providing continuous power
to
>the fuel
>pump with a direct     feed of #10 wire direct to the pump - relayed of
course, but
>always
>on     with ignition. Once I get engine tuned, I?ll enable cutout relay
circuit ?
>that     can
>actually be done through MS.
>
>Fuel delivery ? I have     set at 45 PSI and it maintains good pressure with
>regulated flow.
>There     is a pressure port on the regulator that can vary fuel pressure
about +/-
>5     PSI
>depending upon load/manifold pressure. I see not reason to suspect     there is
>inadequate
>fuel flow or pressure in the rail.
>
>There     are no codes from the MAC-14. Most of the fuel injection portion has
been
>disabled     and only providing power to O2 Heater at this time. MAC-14 is
being
>used
>mainly     for ignition only.
>
>I swapped coils and it made no difference.
>
>I     pulled wires one by one and no one cylinder deviates differently from the
>others I
>will     check plugs and do compression test ? again. When I installed the
engine,
>I     had
>even compression on all cylinders - consistant with a new     engine. Cap and
>Rotor are
>new. Engine now has about 2000     miles on it and still running on the
break-in
>oil.
>
>It     does not make sense that it is EFI since the cutout happens regardless
of
>how     the
>engine is being driven or not ? the cutout occurs at around 5000     RPM even
just
>opening
>the throttle without any engine load. If     it were fuel, I?d think it would
>happen only
>under     load. Possibly the injectors are maxing out, but this does not make
>sense,     as it
>should not take much fuel to rev the engine without a load. I     also don?t
notice
>any lean
>condition when the problem occurs ?     seeing like a 12:1 on the O2 guage. 
Still
>I won?t
>rule     out fuel injectors, but ..
>
>I think there is some reason the     ignition is dropping out ? like not enough
>current to
>the coil     when the engine hits around 5000 RPM. There is of course the long
run
>from     the
>battery located under the seat. I ran an additiona #6 wire to a     jumper post
>located
>near the coil and then runs down to the     starter. Although the engine cranks
>faster when
>starting,     the RPM limit problem is still there. 
>
>I?m wondering if     the coil is not saturating, and not enough current is
>available at
>higher     RPMs. Why this would happen on this car and not on a 200? 
>
>It     doesn?t make sense ? this balanced engine should be good for well over
7000
>RPM. I?m
>going     to post on some other forums ? Megasuirt and MotorGeek, but this
seems
>more     like
>an ignition problem where the MAC-14 is providing the     ignition. Maybe
>installing a
>capacitor or battery up front     to test?I?m looking for ideas.
>
>Ben
>
>
>------------------------------