Fw: [Diy_efi] Lumpy engine in closed loop cruise

Sat Oct 22 05:15:03 UTC 2005

At 04:26 AM 10/22/05, you wrote:

>With a turbocharged car,  a lot of times light load crusing is right below "absolute zero" so to speak... only a light bit of vaccum, which really is 'almost boost' so to speak (if the turbo wasn't there, there would be lots more vaccum)

Well maybe um but the original poster was saying 100 to 130Kpa - which
means its between atmos and slight (+ve) boost, I find that surprising. My gut
feeling (admittedly based on minimal information) is there is either an
exhaust restriction or his valve timing is out a notch or
two if its a belt driven overhead cam or some other issue not allowing
reasonable amount of power to be developed without going boost, maybe
his turbo shaft is gummed up with deposits so it doesnt spin as freely causing
exhaust restriction, I've seen that happen some years ago.

btw: Lets not introduce weird definitions allude to an issue, some of the
less technical might just use that ~`:o  absolute is vacuum, atmos is
effectively 15psi or 100Kpa with respect to absolute, boost implies
something above atmos - which the original poster is suggesting...

For instance, on the RB30E motor - the holden service manual has an
error meaning the gear can be shifted around by one notch, this makes
a large difference to performance, I havent tried this on a turbo motor
but my feeling is it would result in rather different performance.. The
error is corrected in a service bulletin and in the Volume 6 3.0ET supplement.
Incidentally, it is possible to purchase a plate for the cam gear which allows it to be
rotated for more power lower down or higher up - pity its not dynamically
variable like more contemporary engines...

In my experience I used to cruise country at around 140Km/hr in
a ford escort with 1600 flat head motor, granted it had extractors and
huge air intake but it wasnt a turbo and I could cruise (fast) at something
like 75% throttle - therefore my comment that - that amount of manifold
pressure reported seems all too high to me...

Rgds

Mike

>-- LL
>
>On 10/21/05, Mike <<mailto:niche at iinet.net.au>niche at iinet.net.au> wrote:
>At 04:12 PM 10/21/05, you wrote:
>>I think what is happening here is a misunderstanding of "cruise". My old brain may be behind the times,
>>but to me 85 MPH is a bit over cruise. (unless it's an F1 or CART - tongue in cheek). 
>
>Thats really only 136 Km/Hr, bit fast for the freeway I guess,
>
>When I used to go country in the olde ford escort with 1600cc I used to happily
>'cruise' at 140 to 150Kms/hr, no turbo, not even WOT, somewhere around 75%, 
>so his setup with some boost suggests his valve timing might be out or
>he has a reasonably serious exhaust restriction...
>
>Looking forward to doing my block tomorrow with kids, depending on what
>I find I just might really do my block ! 
>
><chuckle>
>
>Rgds
>
>Mike
>
>
>
>
>
>>Geoff H
>>
>>
>>----- Original Message ----- From: "Mike" <<mailto:niche at iinet.net.au>niche at iinet.net.au> 
>>To: <<mailto:diy_efi at diy-efi.org>diy_efi at diy-efi.org>
>>Sent: Friday, October 21, 2005 1:57 PM
>>Subject: Re: [Diy_efi] Lumpy engine in closed loop cruise
>>
>>
>>>At 12:19 AM 10/21/05, you wrote: 
>>>>Why to you say it is heavy load ?  they is almost no boost. 0.3 bar max  which is nothing really.
>>>>Throttle is about 5-10% so the turbo is just ticking over.
>>>huh ? Did I miss-read when you said:-
>>>
>>>"In 5th gear,  trying to hold steady 85 mph,  3500 rpm, MAP about 100-130 kPa" 
>>>
>>>Am I correct in seeing that as absolute manifold pressure at that cruise ?
>>>
>>>To me that says you are at close to atmos pressure in your manifold to
>>>keep it at 85mph, thats a fairly high pressure for cruise - isnt it ? 
>>>
>>>>How do I richen it up,  that is one of my problems.  If you can the VE tabels will the BLM not pull it back.
>>>
>>>Dont know anything about your ECU, maybe aftermarket performance
>>>people can help. However, I have occasionally had similar problems,
>>>came down to electrical connections on air flow meter, the ECU interpreted
>>>this as faulty and switched in and out of limp mode.
>>>
>>>If the car is more than 5 yrs old really worth checking connectors, often 
>>>just cycling them (plugging in and out a few times) can help diagnose.
>>>
>>>Other thing that occurs, make sure all your low voltage leads
>>>are well away from your high tension (EHT) . A common problem on the Nissan 
>>>engine used here in the commodore is the cyl 1 ignition lead being really
>>>close to the crank angle sensor leads and the tags breaking so there
>>>isnt the normal separation, this allows high tension voltage noise to 
>>>get imposed on low voltage signals this can cause ECU to misread
>>>crank signals, in your case make sure the MAP is not being misread
>>>because any high voltage leads cannot corona discharge influencing 
>>>the main sensors. On one forum in Australia we had one guy who went
>>>through 4 crank angle sensors - suffice it to say - he didnt know having
>>>good EHT leads right next to low voltage leads would or could be an issue 
>>>ie. Even  brand new good leads allow some corona effect...!
>>>
>>>Fortunately its not as if its plasma ignition, that would be far worse
>>>
>>><chuckle>
>>>
>>>Rgds 
>>>
>>>Mike
>>>
>>>
>>>
>>>>Dermot
>>>>
>>>>
>>>>
>>>>>Bit of a heavy load for cruise,
>>>>>
>>>>>And yes does sound a bit lean, can you richen it up by 
>>>>>20% and observe the effect ?
>>>>>
>>>>>Rgds
>>>>>
>>>>>Mike
>>>>
>>>>
>>>>Regards from
>>>>
>>>> 
>>>>Mike
>>>>Perth, Western Australia
>>>>VL Commodore Fuse Rail that wont warp or melt !
>>>>Twin tyres for most sedans, trikes and motorcycle sidecars
>>>> http://niche.iinet.net.au
>>>_______________________________________________
>>>Diy_efi mailing list
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>
>Regards from
>
>
>Mike
>Perth, Western Australia
>VL Commodore Fuse Rail that wont warp or melt !
>Twin tyres for most sedans, trikes and motorcycle sidecars 
><http://niche.iinet.net.au>http://niche.iinet.net.au
>_______________________________________________
>Diy_efi mailing list
><mailto:Diy_efi at diy-efi.org>Diy_efi at diy-efi.org
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>
>
>
>-- 
>Sincerely,
>
>Lee M. Lemoine
><http://www.turbochargedsoul.com/>http://www.turbochargedsoul.com/ 
>_______________________________________________
>Diy_efi mailing list
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Regards from

Mike
Perth, Western Australia
VL Commodore Fuse Rail that wont warp or melt !
Twin tyres for most sedans, trikes and motorcycle sidecars
http://niche.iinet.net.au