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THIS DISCUSSION / SOURCE-DERIVED OVERVIEW
Discussion summary
YOUR RESEARCHGUNDO questions (size?)
Leading reported evidence
Use 1.5" pipe and everyone
Performed · outcome unconfirmed
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0
Reported fixes
0
Unsuccessful attempts
1
Discussions
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Discussions that performed work without a confirmed outcome
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Performed · outcome unconfirmed
I used a 1.5" pipe and everyone on the Canadian forum said I was crazy for not going 2".
Run straight pipe muffler bypass systems like those
No successful repair reported for this finding.
0
Reported fixes
0
Unsuccessful attempts
1
Discussions
Read evidence and context
Discussions that contain suggestions
1
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Suggestion
I've seen a number of dyno plots with guys running straight pipe muffler bypass systems like those from Fabspeed and the result seems to be a nominal increase in top-end power with a significant loss at the bottom end.
Leading evidence: 'Use 1.5" pipe and everyone' (no explicit attributable resolution; this is a reported action or suggestion). Across 1 matching discussions, The most frequently discussed action is 'Run straight pipe muffler bypass systems like those' (1 discussions). For that action, 0 discussions report a resolution and 0 report an unsuccessful attempt. No action has an explicit, attributable resolution report under the current rules. These are forum reports and suggestions, not a confirmed diagnosis.
Source reports, not a diagnosis or a success probability. Counts refer to discussions and can overlap.
Explicit resolution reports before identified causes, performed actions and suggestions. Within each level, matching component labels precede direct query mentions and inherited thread context; successful versus unsuccessful discussion counts, owner confirmations and independent discussion support determine order. This is not a probability of success.
Discussions that performed work without a confirmed outcome
1
0 original-poster resolution reports. Counts can overlap; they are not unique people or a success rate.
0 discussions have direct query context; 0 report a fix in that context. Other evidence may inherit the discussion’s subject.
Performed · outcome unconfirmed
I've ordered some used mufflers on EBAY and a mandrel bent piece of 180 degree, 1.25 inch pipe (like the one shown in the link above) last week that are supposed to arrive tomorrow.
Run straight pipe muffler bypass systems like those
Suggestion or failed attempt
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0
Reported fixes
0
Unsuccessful attempts
1
Discussions
Read evidence and context
Explicit resolution reports before identified causes, performed actions and suggestions. Within each level, matching component labels precede direct query mentions and inherited thread context; successful versus unsuccessful discussion counts, owner confirmations and independent discussion support determine order. This is not a probability of success.
Discussions that contain suggestions
1
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Suggestion
I've seen a number of dyno plots with guys running straight pipe muffler bypass systems like those from Fabspeed and the result seems to be a nominal increase in top-end power with a significant loss at the bottom end.
Explicit resolution reports before identified causes, performed actions and suggestions. Within each level, matching component labels precede direct query mentions and inherited thread context; successful versus unsuccessful discussion counts, owner confirmations and independent discussion support determine order. This is not a probability of success.
Discussions that contain suggestions
1
0 original-poster resolution reports. Counts can overlap; they are not unique people or a success rate.
0 discussions have direct query context; 0 report a fix in that context. Other evidence may inherit the discussion’s subject.
Explicit resolution reports before identified causes, performed actions and suggestions. Within each level, matching component labels precede direct query mentions and inherited thread context; successful versus unsuccessful discussion counts, owner confirmations and independent discussion support determine order. This is not a probability of success.
Discussions that contain suggestions
1
0 original-poster resolution reports. Counts can overlap; they are not unique people or a success rate.
0 discussions have direct query context; 0 report a fix in that context. Other evidence may inherit the discussion’s subject.
Suggestion
With all that in mind I planned to duplicate this set-up using a 1.25 inch pipe.
These are separate views of the same evidence. Frequency alone does not establish a fix, and these counts must not be added together.
Run straight pipe muffler bypass systems like those
No successful repair reported for this finding.
0
Reported fixes
0
Unsuccessful attempts
1
Discussions
Read evidence and context
Discussions that contain suggestions
1
0 original-poster resolution reports. Counts can overlap; they are not unique people or a success rate.
0 discussions have direct query context; 0 report a fix in that context. Other evidence may inherit the discussion’s subject.
Suggestion
I've seen a number of dyno plots with guys running straight pipe muffler bypass systems like those from Fabspeed and the result seems to be a nominal increase in top-end power with a significant loss at the bottom end.
0 original-poster resolution reports. Counts can overlap; they are not unique people or a success rate.
0 discussions have direct query context; 0 report a fix in that context. Other evidence may inherit the discussion’s subject.
Suggestion
I've never seen any dyno plots of Gundo hacks using different size pipes - it may be negligible - but in my mind, going to too large of a pipe starts to put you in that scenario.
Discussions that performed work without a confirmed outcome
1
0 original-poster resolution reports. Counts can overlap; they are not unique people or a success rate.
0 discussions have direct query context; 0 report a fix in that context. Other evidence may inherit the discussion’s subject.
Performed · outcome unconfirmed
I've ordered some used mufflers on EBAY and a mandrel bent piece of 180 degree, 1.25 inch pipe (like the one shown in the link above) last week that are supposed to arrive tomorrow.
Counts describe captured discussions, not unique people or a diagnosis. Author identities are not reliably stored. Exact duplicate evidence is counted once across matching discussions; one discussion counts at most once per action/state. Multiple repairs reported together remain a combination. Suggestions and failed attempts do not establish a fix. Matches cover whole discussions and can include related faults, model variants and incomplete threads.
5 eligible posts · 0 unverified posts · 1 discussions match the subject in their title or opening post.
Rennlist: 1 discussions
0 evidence records excluded for query context · 0 excluded by outcome qualification · 0 adjusted by outcome qualification.
0 acknowledgements have no verified action link; they do not establish a repair result.
Generation: 20261026T163944Z · outcome-qualification-6. Deterministic extraction; no AI model inference. How we use sources
Still "pondering" the Gundo Hack
What size "connector pipe did you use?
Are you happy with it?
Too soft. too loud?
Local shops want about $300 to do it...does that seem high?
RE. Pricing - I have not seen anything new on this lately. There are several posts that are a few years old indicating shop costs of less than $100. I presume this means you bring them you muffler. Obviously labor costs will be higher if the shop has to pull and remove both mufflers. Some posts indicate mufflers can be removed with the rear bumper cover on, but most indicate it is much easier with the rear bumper cover off. So all that together can tack on a couple hours of labor.
RE Size - I think I've read threads with ranges from 1.25 to 1.75. The 1.75-inch seems to leave very little room for error in terms of clearing other components when putting it back together depending on your routing.
I had some concerns over the potential loss in torque in the lower RPM range by going with too large of a bypass pipe. I've seen a number of dyno plots with guys running straight pipe muffler bypass systems like those from Fabspeed and the result seems to be a nominal increase in top-end power with a significant loss at the bottom end. I've never seen any dyno plots of Gundo hacks using different size pipes - it may be negligible - but in my mind, going to too large of a pipe starts to put you in that scenario. This is just my theory - no testing involved.
With all that in mind I planned to duplicate this set-up using a 1.25 inch pipe. It's on the small side, but I tend to err on the side of caution and the post indicates it made a really nice improvement in sound - which is really all this hack is good for. There are several audio clips on this thread that you can download of before and after.
https://rennlist.com/forums/996-foru...haust-mod.html
I've ordered some used mufflers on EBAY and a mandrel bent piece of 180 degree, 1.25 inch pipe (like the one shown in the link above) last week that are supposed to arrive tomorrow. I'm hoping to have the Gundo hack done next week and install them by mid-May. I'll report back in a separate thread with pricing and impressions once I do.
Just had mine done. I had mine done for $260 CAD and I think they did great work. Car sounds excellent! I used a 1.5" pipe and everyone on the Canadian forum said I was crazy for not going 2". Either way, I prefer the higher pitch at high rpms I get with 1.5".
Here is the work I got for $260.. no messy welds like I have seen in other cases. I believe this is the Fister style rather than Gundo, but I figured it was relevant enough.
I had the Gundo done with a 1.5" diameter pipe. I believe the Gundo is more work than the Fister, since you have to cut out that "blank". I think the sound is perfect. Very quiet at idle and cruise, no drone, but a nice robust sound on acceleration.
