[DeTomaso] Carb hesitation on level ground at cruise
Julian Kift
julian_kift at hotmail.com
Wed Jul 31 00:06:55 EDT 2024
I don't think that's a fair comparison in today's age of bolt on throttle bodies with self-learning computers. An EFI system is mechanically simpler than a carb IMO, a throttle body and injector(s), with a few sensors, admittedly it's a different skill set to manually tune, but a lot of people are far more comfortable in front of a laptop than at a bench with a carb apart.
Julian
________________________________
From: DeTomaso <detomaso-bounces at server.detomasolist.com> on behalf of Mike Drew via DeTomaso <detomaso at server.detomasolist.com>
Sent: Tuesday, July 30, 2024 8:54 PM
To: Asa Jay Laughton <asajay at asajay.com>
Cc: detomaso at server.detomasolist.com <detomaso at server.detomasolist.com>
Subject: Re: [DeTomaso] Carb hesitation on level ground at cruise
AJ,
If you are a bit lost with a carb I think you will be completely in the woods with injection. A carb is an extremely simple device by comparison.
Smart people, chime in!
Mike
Sent from my iPad
> On Jul 30, 2024, at 20:45, Asa Jay Laughton via DeTomaso <detomaso at server.detomasolist.com> wrote:
>
> Owner has asked if we could fix all problems with fuel injection. I’m not a fan of saying that because I know a well tuned carb can be just as good as well tuned EFI.
>
> If the owner persists, what is the collectives opinions on various EFI systems out there today?
>
> Thank you,
> Asa Jay
>
> Sent via radio waves
>
>> On Jul 30, 2024, at 20:37, Asa Jay Laughton via DeTomaso <detomaso at server.detomasolist.com> wrote:
>>
>> Hi all,
>> I'm working with a PIM 427 Hammer (stroked Windsor) in a Pantera. This has a Demon carb on it. I don't know what it has for jets. I know it runs a little rich.
>>
>> Here is my situation and in a bit of humility, am stumped at the moment. Sam and I just took it out for a long test drive and it has problems on leverlk ground, no load, cruising mode.
>>
>> It idles at about 800 rpm, a bit lumpy but starts right up cold, doesn't die, no choke (no choke on the Demon carb).
>> It revs easily and pulls away from a stop sign beautifully.
>> Under load, moderate throttle or foot to the floor, it runs great.
>> Off throttle, engine braking, it runs fine, though it doesn't burbble like I would expect
>> Uphill great, downhill not so much (that cruise position of the foot on the go-pedal)
>> On level ground, 5th gear, holding cruise at 60 MPH at around 2,000 rpm, it hesitates, jerks, feels like it's misfiring.
>> Same when in say 4th, holding cruise at a higher rpm but no load either with go-pedal down, or engine braking
>> It does this hesitation at nearly any rpm from 1,500 to 3,500 only when holding cruise speed, not when accelerating (even mildly)
>>
>> I'm thinking the problem is the idle mixture and speed settings. I'm thinking the throttle plates might be closed wee bit too much and idle mixture is compensating. When the throttle is at off-idle, at cruise, the transfer ports aren't giving enough gas, or maybe it's air. Trouble is there is no AF gauge on it, and my portable can only be stuffed in one of four exhaust tips.
>>
>> <sigh> so I'm asking for the collectives opinions, I know there are some good ones out there. I figure I need to re-check timing, advance, and carb tune again.
>>
>> Thoughts?
>> Thank you,
>> Asa Jay
>>
>> --
>> Asa Jay Laughton - W7TSC, MSgt, USAFR, Retired
>> Spokane County ARES-RACES-ACS EC/RO
>> ******************************
>> https://w7tsc.org
>> https://www.teampanteraracing.com
>>
>> _______________________________________________
>>
>>
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-------------- next part --------------
I don't think that's a fair comparison in today's age of bolt on
throttle bodies with self-learning computers. An EFI system is
mechanically simpler than a carb IMO, a throttle body and injector(s),
with a few sensors, admittedly it's a different skill set to manually
tune, but a lot of people are far more comfortable in front of a laptop
than at a bench with a carb apart.
Julian
__________________________________________________________________
From: DeTomaso <detomaso-bounces at server.detomasolist.com> on behalf of
Mike Drew via DeTomaso <detomaso at server.detomasolist.com>
Sent: Tuesday, July 30, 2024 8:54 PM
To: Asa Jay Laughton <asajay at asajay.com>
Cc: detomaso at server.detomasolist.com <detomaso at server.detomasolist.com>
Subject: Re: [DeTomaso] Carb hesitation on level ground at cruise
AJ,
If you are a bit lost with a carb I think you will be completely in the
woods with injection. A carb is an extremely simple device by
comparison.
Smart people, chime in!
Mike
Sent from my iPad
> On Jul 30, 2024, at 20:45, Asa Jay Laughton via DeTomaso
<detomaso at server.detomasolist.com> wrote:
>
> Owner has asked if we could fix all problems with fuel injection.
I'm not a fan of saying that because I know a well tuned carb can be
just as good as well tuned EFI.
>
> If the owner persists, what is the collectives opinions on various
EFI systems out there today?
>
> Thank you,
> Asa Jay
>
> Sent via radio waves
>
>> On Jul 30, 2024, at 20:37, Asa Jay Laughton via DeTomaso
<detomaso at server.detomasolist.com> wrote:
>>
>> Hi all,
>> I'm working with a PIM 427 Hammer (stroked Windsor) in a Pantera.
This has a Demon carb on it. I don't know what it has for jets. I
know it runs a little rich.
>>
>> Here is my situation and in a bit of humility, am stumped at the
moment. Sam and I just took it out for a long test drive and it has
problems on leverlk ground, no load, cruising mode.
>>
>> It idles at about 800 rpm, a bit lumpy but starts right up cold,
doesn't die, no choke (no choke on the Demon carb).
>> It revs easily and pulls away from a stop sign beautifully.
>> Under load, moderate throttle or foot to the floor, it runs great.
>> Off throttle, engine braking, it runs fine, though it doesn't
burbble like I would expect
>> Uphill great, downhill not so much (that cruise position of the foot
on the go-pedal)
>> On level ground, 5th gear, holding cruise at 60 MPH at around 2,000
rpm, it hesitates, jerks, feels like it's misfiring.
>> Same when in say 4th, holding cruise at a higher rpm but no load
either with go-pedal down, or engine braking
>> It does this hesitation at nearly any rpm from 1,500 to 3,500 only
when holding cruise speed, not when accelerating (even mildly)
>>
>> I'm thinking the problem is the idle mixture and speed settings. I'm
thinking the throttle plates might be closed wee bit too much and idle
mixture is compensating. When the throttle is at off-idle, at cruise,
the transfer ports aren't giving enough gas, or maybe it's air.
Trouble is there is no AF gauge on it, and my portable can only be
stuffed in one of four exhaust tips.
>>
>> <sigh> so I'm asking for the collectives opinions, I know there are
some good ones out there. I figure I need to re-check timing, advance,
and carb tune again.
>>
>> Thoughts?
>> Thank you,
>> Asa Jay
>>
>> --
>> Asa Jay Laughton - W7TSC, MSgt, USAFR, Retired
>> Spokane County ARES-RACES-ACS EC/RO
>> ******************************
>> [1]https://w7tsc.org
>> [2]https://www.teampanteraracing.com
>>
>> _______________________________________________
>>
>>
>> Detomaso Email List is not managed by POCA
>> Posted emails must not exceed 1.5 Megabytes
>> DeTomaso mailing list
>> DeTomaso at server.detomasolist.com
>> [3]http://server.detomasolist.com/mailman/listinfo/detomaso
>>
>> To manage your subscription (change email address, unsubscribe,
etc.) use the links above.
>>
>> Members who post to this list grant license to the list to forward
any message posted here to all past, current, or future members of the
list. They also grant the list owner permission to maintain an archive
or approve the archiving of list messages.
>
> _______________________________________________
>
>
> Detomaso Email List is not managed by POCA
> Posted emails must not exceed 1.5 Megabytes
> DeTomaso mailing list
> DeTomaso at server.detomasolist.com
> [4]http://server.detomasolist.com/mailman/listinfo/detomaso
>
> To manage your subscription (change email address, unsubscribe, etc.)
use the links above.
>
> Members who post to this list grant license to the list to forward
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list. They also grant the list owner permission to maintain an archive
or approve the archiving of list messages.
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