[DeTomaso] Engine Noise

Wed Apr 4 12:32:50 EDT 2007

I'm sure others will chime in, but here is my take on why the EFI and IR 
manifold make a difference.

At idle, there isn't a lot of vacuum signal at the holley, so doesn't 
meter fuel as well at idle as an EFI system.  This is also the case for 
an IR manifold, better vacuum signal at the carburetor.

Obviously, there is more to the sound than just the EFI and IR... cam 
and exhaust are probably more important.

Paul
#9270

Ken Green wrote:
> Maybe someone can describe the dynamics of a lumpy idle?  If switching to an IR system changes it, I suppose it's at least partly the interaction between cylinders.  If EFI reduces it (with a similar manifold) it would seem to be a fuel modulation issue?  But I think EFI just likes a different cam also, and maybe the cams which EFI likes just don't produce as lumpy of an idle? 
>    
>   Time to go back to school.
>    
>   Ken
> 
> Phil Lockett <montecarlo296 at yahoo.com> wrote:
>   I'd have thought that mudulating (lmao!) the airflow would make the engine hunt as opposed to acheiving lumpiness - as the air involved is fluid. I suppose a bigger cam for one of these is gonna be difficult - but you never know with our German friends and those Autobahns.
> 
> Phil
> 
> Ken Green wrote:
> If you really want the lumpy idle, I'd guess something could be added to an EFI with an idle air valve to mudulate the air flow at idle and get a lumpy effect. Kinda like the fake blow off valves the kids get. Is a lumpy idle (or the conditions which create it) hard on plugs?
> 
> Ken
> 
> adin at frontier.net wrote:
> When I was young Moses told me that lumpy idle was due to cam overlap. 
> Now Dan J says it is manifold affected. Weber/EFI probably won't 
> have the rumparumpa of a big Holley.
> 
> I do know the rumparumpa idle prevents street racing! ("I'm not 
> racing THAT thing!") True story.
> 
> Dan: did the Florissant gig go through? Have the Cobra - its a beast!
> 
> David in Durango
> 
> 
> 
> 
> Quoting Charles McCall :
> 
>> Phil -
>> Lumpy will be related to cam and throaty to exhaust, more or less.
>>
>> You may lose some lumpiness going to a stock BMW due to the cam and the FI.
>> I remember that Kirby Schrader had a fairly aggressive cam in his 377
>> stroker, and he commented that some of the lumpiness went away when he
>> installed EFI. He sounded kinda bummed about that! :-)
>>
>> I'd recommend separating lumpiness from sound level. A more radical cam will
>> give you a lumpier idle. The noise level, and to some extent noise quality,
>> depends on the exhaust. Stock Ansa Pantera exhausts are (relatively) quiet,
>> GTS a little less so, and some of the aftermarket mufflers like Mind Train
>> are, well, really really loud! When going from a Mind Train equipped Pantera
>> to one with a stock GTS system it sounded as though someone had stuffed a
>> pillow in the muffler.
>>
>> Describing sounds is really hard. The best way to decide is to go to a DTDC
>> meeting and go out in the parking lot and listen! Ask the owners what
>> exhaust system they have. Everything else will be subjective. How do you
>> define "loud", or "lumpy", or "awe-inspiring" or "wussy"?
>>
>> The only other advice I can give is that I have driven BMW-powered Guaras,
>> and a 5.0 liter powered Pantera Si. While both of them were quick, probably
>> quicker than a stock Pantera, I missed the rumble of the Cleveland, and
>> specifically the vibration that you FEEL more than HEAR. A Pantera shouldn't
>> just be loud, but should treat ALL your senses. You feel the Cleveland
>> rattling your fillings - not in a negative sense, but you can feel it in
>> your bones. The other powerplants felt too isolated. May be due to the
>> difference in construction of the later model cars, but that was my
>> impression.
>>
>> -----Mensaje original-----
>> De: detomaso-bounces at realbig.com [mailto:detomaso-bounces at realbig.com] En
>> nombre de Phil Lockett
>> Enviado el: Wednesday, 04 April, 2007 11:55 AM
>> Para: detomaso forum
>> Asunto: [DeTomaso] Engine Noise
>>
>> Guys, I've been listening to some Panteras on Youtube - mostly Euro based I
>> think. Most of them seem to have a seriously lumpy tickover with the
>> "splickety splack" noise (technical term) when throttled. Other ones are a
>> lot quieter and less lumpy - I expect being more standard setup. Is the
>> lumpy tickover due to tuning and aftermarket exhausts? The big question
>> being am I going to lose all of this if I fit a BMW engine? The BMW engined
>> Sprinter on Youtube sounds like a Wailing Banshee - but it's just not
>> throaty enough.
>>
>> Comments please (I've been offered a cheap BMW 4.0V8 engine.)
>>
>> Phil
>>
>>
>> Bigger,louder, faster, better.
>>
>>
>>
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