[urq] EFI + MAC-14 maxing ataround 5k RPM

Ben Swann benswann at verizon.net
Fri Oct 26 06:13:31 PDT 2007

Hall sensor with stock ignition setup for 1990 Audi 200 turbo quattro.  Uses flywheel
sensors.  Should not be the problem if wiring is correct and no defective parts.  This
ignition provides plenty of headroom and variations were used on the 5 cyl turbo's from
'81 on.

One reason I stuck with OEM ignition is because I know it works - provided the
installatin is good.  With a homebrew system, I'd have a lot more unknowns to deal with.


-----Original Message-----
From: Claus Vegener [mailto:vegener at post7.tele.dk] 
Sent: Friday, October 26, 2007 4:50 AM
To: Stephen Redford; Ben Swann
Cc: URQ; quattro at audifans.com
Subject: Re: [urq] EFI + MAC-14 maxing ataround 5k RPM

What cranksensor is used ?
I had the same cut-out at 5000 rpm with a 034EFI box.
The VR sensor was the problem. Balancing an changing thoot depth and VR 
sensors for the 60-2 front wheel did not change things real; months of 
Changing to a general Hall did the job.
Urq 20V 2.5l 525 Hp
----- Original Message ----- 
From: "Stephen Redford" <shr42 at msn.com>
To: "Ben Swann" <benswann at verizon.net>
Cc: "URQ" <Urq at audifans.com>; <quattro at audifans.com>
Sent: Friday, October 26, 2007 11:21 AM
Subject: Re: [urq] EFI + MAC-14 maxing ataround 5k RPM

> ------------------ Ben , you can get Megasquirt with Spark,  Why the 
> hybred combo?  It sounds like spark might be the issue and maybe the Mac 
> 14 is the reason .    Just a guess.       Stephen Redford  '85Urq with 
> Megasquirt and still in the shop !!!     :)))
>  ----- Original Message ----- 
>  From: Ben Swann<mailto:benswann at verizon.net>
>  To: urq at audifans.com<mailto:urq at audifans.com> ; 
> quattro at audifans.com<mailto:quattro at audifans.com>
>  Cc: 'Ben Swann'<mailto:benswann at verizon.net>
>  Sent: Tuesday, October 23, 2007 6:41 AM
>  Subject: [urq] EFI + MAC-14 maxing ataround 5k RPM
>  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
>  _______________________________________________
>  Audifans urq mailing list
>  Send posts to: mailto:urq at audifans.com<mailto:urq at audifans.com>
>  Manage your list connection: 
>  Have an urq question?  Check the Audifans Knowledgebase!
>  Have an urq answer? ... Please help others by adding to the KB ... all 
> contributions welcome!
>  You can help keep the audifans site running by shopping at 
> http://audifans.com/shop/<http://audifans.com/shop/>
> _______________________________________________
> Audifans urq mailing list
> Send posts to: mailto:urq at audifans.com
> Manage your list connection: http://www.audifans.com/mailman/listinfo/urq
> Have an urq question?  Check the Audifans Knowledgebase!
> http://www.audifans.com/twiki/bin/view/Audi/UrQuattro
> Have an urq answer? ... Please help others by adding to the KB ... all 
> contributions welcome!
> You can help keep the audifans site running by shopping at 
> http://audifans.com/shop/

More information about the quattro mailing list