Miatapower List Archive

This read-only message was archived from a public mail list.
Mail From: "Abraham Mara" <(email redacted)>

I've got an FMII on my 00 car ("48 state", i.e. non-california) and I have =
more or less decided to make my own exhaust system. I'm still not sure whe=
re to find out what the trade off is between different grades of catalytic =
converter and performance and emissions.... (If anyone knows, let me know!=
!!)

My question is this: I've decided to make my own system, 3" all the way ba=
ck, but I've already got this nice downpipe from FM sitting on my turbo. B=
ut, it's a 2.5" pipe I believe. What's the point of putting a 3" cat+back =
exhaust on only to be behind the 2.5" restriction up ahead?

Does anyone have any experience with this? Should I try to fabricate that =
piece as well? The top bit that bolts to the turbo is NOT a trivial round =
pipe. I'm just wondering if there's big gains to be had by not using their=
piece, or big complication/expense in having a 3" version of it made.

Still looking at ideas here, but it's where I'm thinking of going.
-Abe.

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Mail From: "Todd Paciorek" <(email redacted)>

Still should see gains with the 3" from downpipe back. ever-increasing from
the turbo is fine, just don't go from larger to smaller.

_____

From: Abraham Mara [mailto:(email redacted)]
Sent: Tuesday, April 05, 2005 8:31 PM
To: (email redacted); (email redacted)
Subject: Custom Exhaust for an FMII

I've got an FMII on my 00 car ("48 state", i.e. non-california) and I have
more or less decided to make my own exhaust system. I'm still not sure
where to find out what the trade off is between different grades of
catalytic converter and performance and emissions.... (If anyone knows, let
me know!!!)

My question is this: I've decided to make my own system, 3" all the way
back, but I've already got this nice downpipe from FM sitting on my turbo.
But, it's a 2.5" pipe I believe. What's the point of putting a 3" cat+back
exhaust on only to be behind the 2.5" restriction up ahead?

Does anyone have any experience with this? Should I try to fabricate that
piece as well? The top bit that bolts to the turbo is NOT a trivial round
pipe. I'm just wondering if there's big gains to be had by not using their
piece, or big complication/expense in having a 3" version of it made.

Still looking at ideas here, but it's where I'm thinking of going.
-Abe.

This read-only message was archived from a public mail list.
Mail From: casey wheeler <(email redacted)>

Oh, I think I know this one....
Putting a 3inch exhaust on an FM car is really not that needed. I believe on the FM site they have comparisons of the same car doing back to back runs with a 3 inch system vs the 2.5 inch. They decided it wasn't worth it. Outside of their testing one would think you would gain *some* spool, but if your not pushing the limit of the T28, you probably wont gain any on the top or even throughout the RPM band. If you still decide on making your own piece, remember that restriction not only deals with the diameter, but also the length. Keeping that in mind, I have seen some folks that have gone with the standard down-pipe, then attaching a 3incher on there. Others have chopped the standard dp off right after the "shelf" that holds the brake booster,while the really eager have cut the shelf out to make room for a full 3 inch system. I think some have run into problems in the transmission tunnel, but don't quote me on that. I personally wouldn't go through all the trouble to do it; unless I
was running a T3/T4 setup.

my .02 cents
space

Abraham Mara <(email redacted)> wrote:
I've got an FMII on my 00 car ("48 state", i.e. non-california) and I have more or less decided to make my own exhaust system. I'm still not sure where to find out what the trade off is between different grades of catalytic converter and performance and emissions.... (If anyone knows, let me know!!!)

My question is this: I've decided to make my own system, 3" all the way back, but I've already got this nice downpipe from FM sitting on my turbo. But, it's a 2.5" pipe I believe. What's the point of putting a 3" cat+back exhaust on only to be behind the 2.5" restriction up ahead?

Does anyone have any experience with this? Should I try to fabricate that piece as well? The top bit that bolts to the turbo is NOT a trivial round pipe. I'm just wondering if there's big gains to be had by not using their piece, or big complication/expense in having a 3" version of it made.

Still looking at ideas here, but it's where I'm thinking of going.
-Abe.

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This read-only message was archived from a public mail list.
Mail From: "Larry Alster" <(email redacted)>

Size is an issue when trying to squeeze a 3" system in a Miata. More likely
the 2.5" system was the choice for ease of installation and reliability of
fit. Remember these are being sold as off the shelf, DIY installs.

If you want to take the time to design a 3" system and make it fit without
interference there is likely to be gains to be had. The question becomes
are the gains worth the time and effort and what about getting something
that doesn't end up sounding like a fart.


Larry

White Knight 1991 Crystal White #99 CSP
Silver Bullet 1992 Silverstone #17 EM FM I+ Turbo
Honey B 1992 Sunburst Yellow J.R. M45
Whooosh 2004 Titanium MazdaSpeed MX5

LowCountry Miata lowcountrymiataclub.net
Masters Miata
RAGS 074

----- Original Message -----
From: "Berck E. Nash" <(email redacted)>
To: "Abraham Mara" <(email redacted)>
Cc: <(email redacted)>; <(email redacted)>
Sent: Tuesday, April 05, 2005 9:01 PM
Subject: Re: [Miata] Custom Exhaust for an FMII


> Abraham Mara wrote:
>
>> My question is this: I've decided to make my own system, 3" all the way
>> back, but I've already got this nice downpipe from FM sitting on my
>> turbo. But, it's a 2.5" pipe I believe. What's the point of putting a
>> 3" cat+back exhaust on only to be behind the 2.5" restriction up ahead?
>
> This is going to sound silly, but do you know you'd get better performance
> from a 3" system?
>
> Wider is not necessarily better.
>
> It seems to me that FM probably decided the optimum size for a turbo
> exhaust was 2.5"? I could be wrong, and they're constrained to 2.5" for
> some reason other than performance...
> _______________________________________________
> Miata mailing list
> (email redacted)
> ftl.realbig.com/mailman/listinfo/miata
>

This read-only message was archived from a public mail list.
Mail From: Jason C <(email redacted)>

I have a full custom 2.5" exhaust with a hi-flow
carsound cat. At 10 psi / 240 whp, the cat has 3 psi
of pressure drop across it, the rest of the exhaust,
1.5 psi, the 2.5" downpipe, 0.5 psi.

I presume 3" piping might save 0.5 psi. Not much.
The cat, OTOH, would make a big difference.

Also, I have a theory that at higher boost, every 1
psi of pressure drop saved in the intercooler and
piping, will save 1.5 - 2 psi backpressure across the
turbine. So if you have 3 psi or more of loss across
your i/c and piping, there's more to be gained there.

This read-only message was archived from a public mail list.
Mail From: (email redacted)


The 2.5" is quite adequate on the FM-II you won't likely gain much if
anything even from an open 3" sewer pipe. (Trust me, I built one dyno'd it
and was pissed off that I did not pick up power!) I had my own dyno at the
time.

Mark



On Tue, 5 Apr 2005, Abraham Mara wrote:

> I've got an FMII on my 00 car ("48 state", i.e. non-california) and I have more or less decided to make my own exhaust system. I'm still not sure where to find out what the trade off is between different grades of catalytic converter and performance and emissions.... (If anyone knows, let me know!!!)
>
> My question is this: I've decided to make my own system, 3" all the way back, but I've already got this nice downpipe from FM sitting on my turbo. But, it's a 2.5" pipe I believe. What's the point of putting a 3" cat+back exhaust on only to be behind the 2.5" restriction up ahead?
>
> Does anyone have any experience with this? Should I try to fabricate that piece as well? The top bit that bolts to the turbo is NOT a trivial round pipe. I'm just wondering if there's big gains to be had by not using their piece, or big complication/expense in having a 3" version of it made.
>
> Still looking at ideas here, but it's where I'm thinking of going.
> -Abe.

This read-only message was archived from a public mail list.
Mail From: (email redacted)


240 RWHP using the Link piggy and FM-II turbo.

Mark


On Thu, 7 Apr 2005, Abraham Mara wrote:

> Out of curiosity, what HP were you at?
> -Abe.
> ----- Original Message -----
> From: <(email redacted)>
> To: "Abraham Mara" <(email redacted)>
> Cc: <(email redacted)>; <(email redacted)>
> Sent: Wednesday, April 06, 2005 7:02 PM
> Subject: Re: Custom Exhaust for an FMII
>
>
> >
> > The 2.5" is quite adequate on the FM-II you won't likely gain much if
> > anything even from an open 3" sewer pipe. (Trust me, I built one dyno'd it
> > and was pissed off that I did not pick up power!) I had my own dyno at the
> > time.
> >
> > Mark
> >
> >
> >
> > On Tue, 5 Apr 2005, Abraham Mara wrote:
> >
> >> I've got an FMII on my 00 car ("48 state", i.e. non-california) and I
> >> have more or less decided to make my own exhaust system. I'm still not
> >> sure where to find out what the trade off is between different grades of
> >> catalytic converter and performance and emissions.... (If anyone knows,
> >> let me know!!!)
> >>
> >> My question is this: I've decided to make my own system, 3" all the way
> >> back, but I've already got this nice downpipe from FM sitting on my
> >> turbo. But, it's a 2.5" pipe I believe. What's the point of putting a
> >> 3" cat+back exhaust on only to be behind the 2.5" restriction up ahead?
> >>
> >> Does anyone have any experience with this? Should I try to fabricate
> >> that piece as well? The top bit that bolts to the turbo is NOT a trivial
> >> round pipe. I'm just wondering if there's big gains to be had by not
> >> using their piece, or big complication/expense in having a 3" version of
> >> it made.
> >>
> >> Still looking at ideas here, but it's where I'm thinking of going.
> >> -Abe.
>
>