[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]
Re: Performance difference w/o a cat? (end!) for Scir.org (long)
You can file this and delete all the other posts.
Doug.
87 16v "GTX"
**********************
Does anyone know how much of a difference in performance/power there is in
running without a cat? The motor in question will be a 2.0 16V. And yes I
am aware of the enviromental aspects and laws associated with doing this;
it's just a question, hint hint, nudge nudge.
John Worden
Old Town, ME.
'84 Scirocco (under construction) Brakes and Suspension currently
***************************
only a few hp way up top (like over 6K).
chris
86 16V scirocco
****************************
I don't know specifically about a 16v, but when I removed the cat from my
QSW
(2.2L 10v I-5), it made a large difference in throttle response and
high-rpm
power. Same for the 8v Sciroccos I've done it to.
-Josiah
'84 GTI
'87 QSW
******************************
Truthfully, the performance gains should be minimal-- if not negligable.
The reason there were substantial differences for Josiah were probably due
to the cat's age and clogged-ness. A new or good-condition cat should not
restrict the exhaust enough to cause more than a 1-2hp loss... The engine
was designed with it; leave it.
Jason
***************************
simply removing a cat will NOT give you 10hp. the difference between
the 129hp and 139hp has to do with more than just the cat. they also
used K-jet instead of KE-jet, vacuum advance ignition, etc. they
probably removed it to allow a richer mixture that may overheat a cat,
or maybe to allow the use of leaded gas which would allow more ignition
advance. THAT i can see adding 10hp up top. but JUST swapping out a
cat/downpipe with a catless downpipe will not net 10hp. no way, no how.
chris
86 16V scirocco
*************************
Not so many days a discussion what differed the eurpoean version
(Old information)
>from the US version. We got to versions here, early cars with no
>cat and 139hp and later versions with cat and only 129hp. So
>10hp difference with a cat vs no cat setup on US cars don't seem
>so strange.
>
>But if you compare a car with a free flowing race cat or no cat
>it might not be any big difference.
>
>Roland Johansson
>Scirocco 1,6l TIC -82
>Http://hem.passagen.se/toker
> One of the magazines I just got (don't remember which one)
>was working on a project car. They were doing an exhaust thing
and found their car had a hollowed out cat. They put a new cat on, and
the
car made more power with the cat than without.
I agree. Precious exhaust gas velocity is severly
hindered when the downpipe opens up into the cat, then must be re-funneled
into the rest of
the system. Not exactly a device designed with performance in mind,
although it is a
highly efficient unit, as
far as cats go. Going with a catless downpipe like the new TT offer
greater torque, throttle response, and hp (I think TT claims 11 peak).
hold on, 11hp?!?! hmmmm... i seriously doubt that, VERY seriously.
maybe comparing the single outlet manifold/downpipe w/cat to a dual
outlet manifold/dual long downpipe, then MAYbe it would be close to
11hp. but not comparing the 16V dual downpipe with or
without a cat, no
way...
chris
86 16V scirocco
*****************************
At 08:38 PM 1/27/99 -0500, Jim Buck wrote:
"New 2" Racing Dual Downpipe for Scirocco 16v
Same as above except with 2" primary pipes. This
downpipe was designed for modified engines. Adds
approximately 11hp."
I don't claim that it adds 11hp Chris, TT does.
Snip
à yeah, i know. i have the catalogue too (chris 86 16V scirocco)
Unsnip
It may be less, it may be
more, but my main point was (and still is) that consistent pipe diameter
throughout the sytsem will provide more torque and hp than a big ole cat
chamber just 1
1/2 feet downstream from the header (read: turbulence=bad). The Scirocco
cat is
one of the best out there, but still is no match for a non-cat dual
downpipe,
even if the one i've described is for modded engines. Get one=go faster.
Jim
Snip
à i understand that. i never said there is NO difference. BUT, notice
the comment about "designed for modified engines". take a cat off a
stock 1.8 16V and you won't get 11hp. no way. the racing downpipe is
also bigger in diameter, so we are talking about not only removing the
cat, but also increasing the inside diameter of the downpipes. this
will help an engine with a p&p job, hot cams that is being restricted by
the stock exhaust. but the stock 1.8 16V is not that restricted, and
removing that cat *without doing anything else* will not add 11hp. that
was/is my point.
The Scirocco cat is one of
>the best out there, but still is no match for a non-cat dual downpipe,
even
>if
>the one i've described is for modded engines. Get one=go faster.
again i agree, but the question is "how much faster". the answer is:
stock engine, not much faster, *a little*, but not much. modified
engine, yes, you may see up to 11hp, but only if the engine flows
enough.
i don't remember if it was you or someone else, but there was a comment
made on how rich mixtures don't overheat a cat. this is not true, rich
mixtures DO overheat cats, sometimes even to the point of
melting/catching fire. in europe when they sold the scirocco, leaded
gas was still readily available. maybe some of you yurpeens could help
out with facts here, but my theory is that the difference between the
129 and 139 hp figures is that the catless 139hp engine used leaded
fuel, which allowed it to used more ignition advance (K-jet), and
perhaps a slightly richer mixture too.
chris
86 16V scirocco
********************************
That's the one that Potterman is getting me.
("New 2" Racing Dual Downpipe for Scirocco 16v)
When I get it all together
I'll see about getting the car dynoed. Then we can see what kind of
increase it has. The only problem will be no original baseline. It's a
standard 16V with a 2.0 bottom end so it's probably somewhere between the
123hp and 134 hp of the motronic 16Vs(halfway between the two maybe?).
Anybody know what it costs to get a car dynoed(chassis type).
John Worden
'84 Scirocco (under construction) Brakes and Suspension currently
*****************************
Aw man,
You gotta get it dyno'd _before_ & after. Else you rely on the
EuroCarMag Mk1 Dyno Butt, and those are notoriously hard to calibrate.
Maybe the place you find to get it done might make you a deal on a now
n' later package, after all that's one of the whole points to getting it
dyno'ed in the 1st place, eh?
Tberk
*****************************
To Tberk:
I agree, but the problem is that it is an '84 going from 8v to 16v and it
has no exhaust at all right now. If it had something there I would dyno it
but I can't.
John Worden
********************************
"At 08:38 PM 1/27/99 -0500, Jim Buck wrote:
>"New 2" Racing Dual Downpipe for Scirocco 16v Same as above except with 2"
primary pipes. This
> downpipe was designed for modified engines. Adds approximately 11hp."
This is the down pipe that I have. I cant see it adding anywhere near that
much. 2-3hp max. I was enthused to get it but kinda of disappointed at
losing so much bottom end and only gaining a 2 or 3 more thousand rpms of
usable power. The biggest mod i have really felt was Brian Honnolds home
made enrichment module. That thing is well worth whatever he would
charge....at first test I tought i broke my tach the thing spun up so fast.
But I do have just a 1.8 16V.
Thank You for Your Time,
Shannon Fenton
********************************
To: Shannon Fenton
Yes that's the super duper TT ripoff fuel module that I designed built and
tested all on my own.....
Guranteed to land yer ass in jail for doing 95 in a 35......eh Shannon!!!
Brian Honnold
'78 Rocco Ragtop
**************************
Jeez...and I wanted to make a good impression on the new list members. Now
they
all know how dumb I am...do I fluant youre failures in front of others
Brian...jeez, try to give a guy a compliment....at least I dont have fire
prone
headlight wiring ehhh sparky......
Thank You for Your Time,
Shannon Fenton
???The biggest mod i have really felt was Brian Honnolds home
made enrichment module. That thing is well worth whatever he would
charge....at first test I tought i broke my tach the thing spun up so fast.
But I do have just a 1.8 16V.???
**************************
Hehe point taken...my sincerest appologies to Mr. Fenton
And as a note to all of you who are contemplating relays for your
headlights, don't use electrical tape to hold the positive wires to the
relays and always use fuses. Lotsa fuses
Brian Honnold
'78 Rocco Ragtop (crispiest wires in Sacramento)
*************************
AH HA!! So that settles it!! Meze and I aren't the only jailbirds on the
list! :) WooHoo!!
And Shannon, could you do me a personal favor? Turn off the return receipt
notification thingies? Thanks...
Jason
****************************
> i understand that. i never said there is NO difference. BUT, notice
> the comment about "designed for modified engines". take a cat off a
> stock 1.8 16V and you won't get 11hp. no way. the racing downpipe is
> also bigger in diameter, so we are talking about not only removing the
> cat, but also increasing the inside diameter of the downpipes. this
> will help an engine with a p&p job, hot cams that is being restricted by
> the stock exhaust. but the stock 1.8 16V is not that restricted, and
> removing that cat *without doing anything else* will not add 11hp. that
> was/is my point.
Then we each had different points, and we both were right!
> The Scirocco cat is one of
> >the best out there, but still is no match for a non-cat dual downpipe,
even
> >if
> >the one i've described is for modded engines. Get one=go faster.
>
> again i agree, but the question is "how much faster". the answer is:
> stock engine, not much faster, *a little*, but not much. modified
> engine, yes, you may see up to 11hp, but only if the engine flows
> enough.
Right. The engine must be modded to increase flow for the larger pipes of
that
particular item. But I'm still maintaining that if you replace the
cat/downpipe
of a 16v roc with a non-cat one of the same pipe diameter and routing as
the
original, it will provide both more torque and hp. I'm not sure on how
much more,
just more. Otherwise, IT and club racers would be scrambling to bolt up
cat/downpipes to their race cars, which would be nonsensical. As a general
rule,
cats interrupt flow to the detriment of performance, no matter how well
designed.
As far as the Euro Rocco 16v goes, I think the 139hp comes from:
50mm intake runners
more radical intake cam
no cat
vacuum advance distributor
--
Jim Buck
****************************
--
To unsubscribe, send "unsubscribe scirocco-l" to majordomo@scirocco.org.
If you experience other problems, email: scirocco-l-probs@scirocco.org