2.7 with stock leistritz vs Dansk sport

[911MRP]

I don’t have paper parts book 74 on but appears the 01 suffix was for the 74 revision of electronic PET can be trusted on supercession? So it looks like Roberts’s example being early 74 what he refers to as pro type has had the part number stamp hand ans presumably form amended to the new version

Hi Steve.
I’ll run an original early bischoff tomorrow.
M preproduction 74’ Carrera still has it original muffler. A bischoff dated 4/73
I can’t remember what my first series rs had. Will look it up.

Today I still installed my early factory 3 pipe with caps, sport rallye muffler that bolts up to standard exchangers.
It yielded the 225hp I was looking for but not worth the 3hp to noise ratio. It Was cool when I was 18 but would only use it today for some race/rallye purpose today .

Regards,

On closer inspection of roberts example it seems like the first zero of suffix has been struck out using a diagonal then the 1 stamp added at end to make it ./01 ( rather than .001).


I suppose they modified the shape of the pipe of the 4/73 for the new facelift rear bodywork but the main parts of muffler box itself were as used in 72/3 TES and RS thereby with pragmatic amendments making it the appropriate part number ( and shape for) for 74 on during the transition?


Robert: there a version ((911/x) number like this stamped on it? If this is as seems highly likely an early part modified tail on an .00 exhaust silencer. Is it a stainless steel outer like my 10/72 or all mild steel like my other one 6/72?

What is clear is regardless of number stamp edits done by hand Bischoff was the OEM brand 72-73 based on my two examples and roberts that probaly got the interim modification until tooling made the revised version as impact-bumper volumes scaled-up.

Le parrots too probably but the three discussed here spanning 6/72 - 4/74 associates with model year are bischoff

Steve

[glaverbel911]

glaverbel911, Your test muffler 78’ dated leistritz early muffler style would that be the same as the 69-70 dated? And 2 in 1 out? I thought those are only for engine upto 2.4. It's not too restrictive for the 2.7?

The 78‘ coded muffler I use for test/tuning is a factory replacement for the early engines. The factory had done their homework . Nothing I’ve seen aftermarket to date out-performs them for the street and are a bonus even for the 3.0 - 3.2 engines.
Merry Christmas ,
Robert

[718RSK]

Robert, have you tried the current Porsche classic muffler?

[glaverbel911]

Hi Steve .
My 74‘ Carrera 0012 was built before model year production began. The muffler tip was still hand massaged to fit the new G style body work on the first few examples. It’s a dual layer type. Probably a low grade stainless and the part number probably a bit unique along with it. Performance is still all the same.

Bischoff and leistritz were mixed throughout the years. Not just in 72-73. my 70S still has its 69‘ coded Leistritz/single layer. The performance of the bischoff usually betters the leistritz by an extra 1 or two pony’s . I did not have a chance to too run the bischoff in the 2.7 just before the holidays

I’ve never seen a muffler with 911/X.
My early three pipe rallye muffler had the part number purposely welded over but still has a 911/1 Code.
My 69‘ 911S factory built M-List race car came with a megaphone rallye muffler. It’s coded 901/22

Regards, Robert

[glaverbel911]

Robert, have you tried the current Porsche classic muffler?

Hi.
No. Have not had one yet to test. Would be interesting.
Regards, Robert

[Arne]

My '72T has a Bischoff dated '74. I believe it was a replacement installed due to accident damage to the LR corner back in the '70s. It appears to be a multi-layer with a low-grade stainless outer shell. I've seen some indications that it may have a few pinholes in the shell, but nothing I'm at all concerned with. I love how it sounds, and while a stock '72T is not a powerhouse in any way, it seems to work well with the MFI.

I recall seeing posts from Chuck Miller that said over the years he had tried many different non-stock mufflers, but he always went back to stock because he felt that he lost low-end torque with every aftermarket muffler he tried. This thread adds to that narrative - not only for low-end torque, but top-end power as well.

[Chuck Miller]

I recall seeing posts from Chuck Miller that said over the years he had tried many different non-stock mufflers, but he always went back to stock because he felt that he lost low-end torque with every aftermarket muffler he tried. This thread adds to that narrative - not only for low-end torque, but top-end power as well.

Arne,

Here's that post from '2000 :
https://www.early911sregistry.org/fo...nions&p=242352

And my solution in post #8 from '2004:
https://www.early911sregistry.org/fo...ment-w-muffler

Still on the car almost 18 years later...

Pic of my early exit on my 'G' muffler....

Holiday Cheers,
Chuck

[Spyerx]

So…. What’s the hot ticket to make power on these?. Engine is 2.8, efi, bigish cams, big ports. Long tube headers with larger primaries. Loudness isn’t a concern, except it must have some sort of silencer. No straight pipes!

I have at my disposal but only tested the first one on dyno. Where the car made a tick over 240whp at the wheels (mainline chassis dyno which tends to read more conservative than the more common in us dynojet.

Likely will make one more trip to the chassis dyno after lots of drivability tuning:

M&k - 2 in 2 out 911S type muffler
Dansk stainless sport that was on SSI and the former cis 2.7, 2 in 1 out
Factory 77 911S muffler, 2 in 1 out

I’d be willing to do a swap to one of the other 2 if folks feel we’d see a bump.

[glaverbel911]

Spyerx.
Bigger primary headers and larger ports in most cases is not better. The Port is not the restriction. It’s the area around the valve head , throttle valving and intake stack. Exceeding the perfect cyl head port size by as little as .15mm +/- will kill your torque and horsepower dramatically.

For example on our 2.2L race motor with with a low 10/1 compression. It pulls 261Hp @8400.
Altering the intake port .2mm larger dropped 18hp and only Adding factory 3.0L RSR headers with larger primary’s dropped 22hp.
I run factory exchangers on my 2.8 TP, it makes 100hp/L with S cams with ports smaller than 36mm and an early factory muffler.
Hope that helps you out.

Regards, Robert

[911MRP]

Robert thanks for this interesting thread. Steve