[urq] 20vt ur-q Backfires - Thoughts?

[Mike Fitton]

Exactly.  What's after the exhaust valves can change the quality of the 
exhaust note, for example any given Honda with any given muffler driven 
by any given kid, but the initial nature of the sound is determined in 
the head.  I don't think CIS vs. EFI would affect it enough for the 
human ear to notice, except for noises made by the injectors themselves. 
  It seems to me that the amplitude of the pressure wave made by the 
escaping hot exhaust gasses would be roughly halved with the 20v head. 
This is why the 10v sounds throaty and the 20v sounds more fluid.  I 
have some pretty serious sound analysis software...anyone have a good 
mic and both a 10v and 20v engine with similar exhausts?  I'd love to 
make some comparisons.

-Cheers!
Mike

p.s.  Oh yeah...backfiring.  Sounds like you're just getting some 
unburned fuel in the exhaust somewhere.  Hopefully it's out at the 
tailpipe...hot fuel hits oxygen etc.  Rotaries do this a lot, especially 
the ported ones...big streaks of fire pretty much at will.  Do you have 
a good a:f meter?

Louis-Alain_Richard at computerhorizons.com wrote:

> Don't go that far upstream, Mike. :-)
> 
> Instead of a EFI 10VT owner, what we need to answer this question is a 
> musician. Or a sound engineer.
> 
> The sound produced by a fixed amount of hot gas exiting through an 
> aperture will be different if this aperture is a big one (10V) or 2 small 
> ones (20V).
> More, the exhaust manifold is not a kind of flute, in a way?
> 
> Musicians: Please chime in... 
> 
> Louis-Alain
> 
> 
> 
> 
> 
> "Michael Hopton" <Michael at siliconoptix.com> 
> Sent by: urq-bounces at audifans.com
> 2004-08-31 16:41
> 
> To
> "Brandon Rogers" <brogers at terrix.com>, "Rich Letsinger" 
> <ricoletsinger at yahoo.com>, <urq at audifans.com>
> cc
> 
> Subject
> RE: [urq] 20vt ur-q Backfires - Thoughts?
> 
> 
> 
> 
> 
> 
> Maybe it is the CIS, can anyone comment from a 10vt
> with EFI?
> 
> Cheers, Mike
> 
> -----Original Message-----
> From: Brandon Rogers [mailto:brogers at terrix.com] 
> Sent: Tuesday, August 31, 2004 4:42 PM
> To: Michael Hopton; Rich Letsinger; urq at audifans.com
> Subject: Re: [urq] 20vt ur-q Backfires - Thoughts?
> 
> ehh I don't know about that.  My WX with K24 sounded just like it did
> when I
> had the K26, ISTR.  But I could have early onset memory fade.....
> 
> that said, I do not understand why the 20V sounds more refined, less raw
> than the 10V.  I mean, it's still 5 cylinders with the _exact_ same
> exhaust
> from turbo back....
> 
> Brandon
> 
> 
> ----- Original Message ----- 
> From: "Michael Hopton" <Michael at siliconoptix.com>
> To: "Rich Letsinger" <ricoletsinger at yahoo.com>; <urq at audifans.com>
> Sent: Tuesday, August 31, 2004 12:13 PM
> Subject: RE: [urq] 20vt ur-q Backfires - Thoughts?
> 
> 
> Rich,
> You could be right with the definition, so this is pops and
> bangs out the exhaust and not into the inlet manifold.
> 
> I get it to a much lesser extent on the 10 valve WX. I do
> miss the rumble and deep throaty sound of the 10vt, I think
> the K24 muffles the sound much more.
> 
> Cheers, Mike
> 
> -----Original Message-----
> From: urq-bounces at audifans.com [mailto:urq-bounces at audifans.com] On
> Behalf Of Rich Letsinger
> Sent: Tuesday, August 31, 2004 1:42 PM
> To: urq at audifans.com
> Subject: Re: [urq] 20vt ur-q Backfires - Thoughts?
> 
> Correct me if I'm wrong, but I believe a backfire is
> ignition of gasses in the intake tract or in the
> cylinder while the intake valves are open.  It ends up
> coming out on the intake side in the engine
> comparment.  This is more of a carburetor thing and
> would be very bad on a fuel injected engine.
> 
> This isn't what you guys are talking about.  You guys
> are getting pops or bangs out the exhaust.  This is
> just unspent fuel buring in the turbo or cat, which
> happens with my 3B too.  The former that is, no cat on
> my car. ;)
> 
> Rich
> 
> --- Brandon Rogers <brogers at terrix.com> wrote:
> 
> 
>>My car occasionally has small backfires on hard 1st
>>to 2nd gear shifts.  And
>>I do have cats.
>>
>>Glad to hear I'm not alone....
>>
>>Brandon
>>'84 ur 20V
>>
>>----- Original Message ----- 
>>From: "Martin pajak" <martin at quattro.ca>
>>To: "Michael Hopton" <Michael at siliconoptix.com>;
>><urq at audifans.com>
>>Sent: Tuesday, August 31, 2004 8:13 AM
>>Subject: RE: [urq] 20vt ur-q Backfires - Thoughts?
>>
>>
>>
>>>Now now... ;)
>>>
>>>I do get some nice ones once in a while......
>>>I've scared few pedestrians waiting at a bus stop
>>
>>once... ;)
>>
>>>If we had Catalytics this problem would probably
>>
>>not be there.
>>
>>>How did you like Belgian GP???
>>>Sorry I missed it... my Taxi service was not
>>
>>available.. :(
>>
>>>Cheers
>>>Martin
>>>
>>>-----Original Message-----
>>>From: urq-bounces at audifans.com
>>
>>[mailto:urq-bounces at audifans.com]On
>>
>>>Behalf Of Michael Hopton
>>>Sent: 31-Aug-04 10:00
>>>To: urq at audifans.com
>>>Subject: [urq] 20vt ur-q Backfires - Thoughts?
>>>
>>>
>>>I get quite a bit of backfiring from the 3B engine
>>
>>in my
>>
>>>'84 ur-q. It has the stock rear muffler and 3"
>>
>>pipe from
>>
>>>the down pipe. Stock turbo (250,000 mile!) K24.
>>>
>>>Sometimes between shifts and also on lift throttle
>>
>>I will get
>>
>>>back firing. Sounds good, but I am guessing you
>>
>>can have too much?
>>
>>>I don't have an O2 meter but I am guessing rich
>>
>>spikes, or
>>
>>>possibly oil though the turbo seals?
>>>
>>>Martin's car also backfires, probably not as much
>>
>>as mine or he
>>
>>>just doesn't lift his foot off the throttle, which
>>
>>is true.
>>
>>>Cheers, Mike
>>>
>>>
>>>
>>>
>>>
>>>
>>
> ------------------------------------------------------------------------
> --
> 
>>--
>>
>>>-----
>>>This e-mail and any attachments may contain
>>
>>confidential information. If
>>you
>>
>>>are not the intended recipient, please notify the
>>
>>sender immediately by
>>
>>>return e-mail, delete this e-mail and destroy any
>>
>>copies. Any use, review,
>>
>>>dissemination, forwarding, printing or copying of
>>
>>this email or any
>>
>>>information or attachments contained herein by a
>>
>>person other than the
>>
>>>intended recipient is unauthorized and may be
>>
>>illegal. Silicon Optix
>>
>>>reserves the right to monitor all e-mail
>>
>>communications through its
>>networks
>>
>>>for quality control purposes.
>>>
>>>
>>>_______________________________________________
>>>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.audi-quattro.org/cgi-bin/twiki/view/Audi/UrQuattro
> 
>>>Have an urq answer? ... Please help others by
>>
>>adding to the KB ... all
>>
>>>contributions welcome!
>>>
>>>_______________________________________________
>>>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.audi-quattro.org/cgi-bin/twiki/view/Audi/UrQuattro
> 
>>>Have an urq answer? ... Please help others by
>>
>>adding to the KB ... all
>>contributions welcome!
>>
>>_______________________________________________
>>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.audi-quattro.org/cgi-bin/twiki/view/Audi/UrQuattro
> 
>>Have an urq answer? ... Please help others by adding
>>to the KB ... all contributions welcome!
>>
> 
> 
> 
> 
> 
> _______________________________
> Do you Yahoo!?
> Win 1 of 4,000 free domain names from Yahoo! Enter now.
> http://promotions.yahoo.com/goldrush
> _______________________________________________
> 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.audi-quattro.org/cgi-bin/twiki/view/Audi/UrQuattro
> Have an urq answer? ... Please help others by adding to the KB ... all
> contributions welcome!
> 
> _______________________________________________
> 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.audi-quattro.org/cgi-bin/twiki/view/Audi/UrQuattro
> Have an urq answer? ... Please help others by adding to the KB ... all
> contributions welcome!
> 
> 
> _______________________________________________
> 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.audi-quattro.org/cgi-bin/twiki/view/Audi/UrQuattro
> Have an urq answer? ... Please help others by adding to the KB ... all 
> contributions welcome!
> 
> _______________________________________________
> 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.audi-quattro.org/cgi-bin/twiki/view/Audi/UrQuattro
> Have an urq answer? ... Please help others by adding to the KB ... all contributions welcome!
>