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Philbee

Exhaust Upgrade for a Hotrod

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Its not too often I get to post a new thread but here goes.... I'm considering upgrading my exhaust & headers at some point down the line. Backgroud: My hotrod is an 87 911 coupe underneath with a 993 engine (3.6, M64/05).  Currently, I know I have 964 headers & the exhaust is a custom job I've been told. Any good? Who knows....

Anyway, would like to get a bigger pipe, a better sound and that elusive 10% horses upgrade of course...  I'm thinking a monty, dansk or M&K as they seem to have good "2 in 1 out" exhausts and SSI headers seems to be the go.

But, I'm worried about buying an off the shelf exhaust as I don't know if it would fit. My assumption is that having squeezed a 993 engine into a 3.2 chassis gives me less room to work with. What do you think? Anyone got experience with this....  Do I need another proper custom job or can I get an off the shelf jobbie?

Here's what my butt looks like now. The exhaust seems to only cover half or 2/3 the width. Should be right across to get a good full sound... I've been told.

 

DA92FFFD-466F-4D6F-8A23-47E8C59EC450_zps

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I wouldn't have thought the engine bay size would be much different between the 993 and the 3.2? They are basically the same chassis just with some alterations for the more modern suspension, etc.

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There are some good threads (PP, Renn etc) on fitment of exhausts -backwards forwards compatibility etc.

often (I believe) the difference been the size of recess or not, at the back of the box. This does take into account slight engine and install differences.

rather than been called out for been wishy  washy with prefacing above with I believe as I'd prefer definitive .. you could also talk to mr google 

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As a first step, ie. not getting into HP improvement, I was just thinking physical space as I'm not quite std, ie. which muffler and/or headers can physically fit in the recess at back & will the tailpipe fit in the cutout I have of the rear valance as I don't have a stock rear bumper & don't want to cut or change the bumper... do I need to take measurements? How do you buy a muffler without some exacting measures to ensure it fits?  Sorry, if this sounds stupid cos this stuff is plug n play & I'm fussing for nought.

I'm sure my mechanic knows this stuff and hopefully he'll sort me out here but just trying to see how others have gone about sizing up a muffler (and headers with exchangers) in a non-std chassis/engine space.

@MFX, what you say is re-assuring, thanks. 

I've been looking on PP, Renn, etc.. having trouble finding someone discussing this....  

Although upping HP is a biggy too!! :)

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I am only guessing, but you should be able to use any muffler that fits a G series. It is more about what fits under your rear bumper than anything else I would have thought. You can see in these pics of a 3.2 and a 3.6. Both have basically the same engine mount bar on the back, and as such mount up the the same spot in the engine bay wether it is a G series or a 993. I don't think this should be a very difficult situation.

s-l1000.jpg

images?q=tbn:ANd9GcTMAs1690Q9w4cQxGcaVaU

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One of the main differences with say SC VS 3.2 are the pre silencer and the crossover pipe fitted to the 3.2. This means a 3.2 exh will fit up to an SC. But not vice versa, due to the recess in the back of the can on the 3.2 not the SC.

as for the choice when specifying speak to he manufacturer and tell em what your set up is.

Otherwise all the pipe positions and  I'd say side exit are the same, though due to size of pipe may require fettling.

same for 2 out either side. Straight through usually tuck under and clear rear valance/bumper or can do on earlier cars .

I think your concern about packaging based on the install is not the issue, but rather whether you are retaining mostly stock system adding exh only , or backdating headers etc

 

lets hear that sound clip

 

 

 

Edited by michel

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if you want guaranteed fit;

1) buy and fit some off the shelf headers (i have some 3.6 fabspeed ones on a shelf here if you need, though they will hang low and need a nip and tuck if you have backdated)

2) buy two $130 magnaflow mufflers

3) get any exhaust shop to make the remaining bits and fit mufflers, thus guaranteeing the system fits your car and it's idiosyncrasies

i.e. (without rear valence fitted here)

fVeC5iG.jpg

 

Edited by clutch-monkey

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well, that looks spectacular!  although I'm 1 outlet not 2.

1) buy and fit some off the shelf headers (i have some 3.6 fabspeed ones on a shelf here if you need, though they will hang low and need a nip and tuck if you have backdated)

Q: Off the shelf? Isn't there a performance or track version I should aim for to maximise my HP? I'd be interested to discuss the fabspeed ones you have... How much nipping & tucking are we talking?

2) buy two $130 magnaflow mufflers

Probably best to get a custom muffler made to make sure it fits right, etc and connects up to headers etc...

 

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Phil, why not take a drive to your local indy Pcar dude and show him and ask, Most of those workshops have done plenty of hotups over the decades and can probably tell you straight up what to use, what will (probably) fit, what to expect in noise and performance and what cost to fettle and fit - be prepared to add 50% $$$ to what they say :rolleyes:

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Phil, why not take a drive to your local indy Pcar dude and show him and ask, Most of those workshops have done plenty of hotups over the decades and can probably tell you straight up what to use, what will (probably) fit, what to expect in noise and performance and what cost to fettle and fit - be prepared to add 50% $$$ to what they say :rolleyes:

@sandy468 you're right.... I'm home this week so I read your entry & jumped straight in my car just now and wizzed over  stuart at nineauto. Really friendly guy, great to talk with.

He's helped but also confused me a bit too. He suggested for the headers I get SSI's (3.2 size) even though I have a 3.6. He said it will be ok (not restrictive, in fact should give me more horsies) and true to backdate, sound and look good too. But my reg mechanic and on this forum have commented they'll be too restrictive...less horsies!  Hmmm, nothing like conflicting info. More googling...

As for the muffler, could get a custom job done which he can arrange so it all fits and measures up but sound is unknown. Alternately, I could goto Monty as they're here in Melbourne and get them to tailor one of there's (2 in, 1 out) to fit. And I like the sound of monty. This settles the "will it fit" worry.... now its horses!

Specifically on upping the HP, he's also got a new thing he's done once before on a 993 (a custom mod by him) which he said made a great improvement on HP ... was he could increase  the std inlet manifold or throttle body (?) from 67mm I think he said to around 80mm,.. might have to suss this one out a bit further with him as its way outa my understanding of what he does to the car to do this...

 Might call monty tomorrow...

Any more votes on SSIs for a 3.6? Have 2 against and now 1 for... :wacko:

Edited by Philbee
typo

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A can of worms Phil! Maybe go with the lowest cost easiest option explained here, sound more important than power gains? ..... I'm sure the 3.6 goes well enough , but as fast as they go is it ever enough?:(

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well, that looks spectacular!  although I'm 1 outlet not 2.

1) buy and fit some off the shelf headers (i have some 3.6 fabspeed ones on a shelf here if you need, though they will hang low and need a nip and tuck if you have backdated)

Q: Off the shelf? Isn't there a performance or track version I should aim for to maximise my HP? I'd be interested to discuss the fabspeed ones you have... How much nipping & tucking are we talking?

2) buy two $130 magnaflow mufflers

Probably best to get a custom muffler made to make sure it fits right, etc and connects up to headers etc...

 

they are a generic muffler, they will fit- your exhaust guy makes all the connecting bits of pipe and such, to make it fit just so. So generic muffler and custom piping I guess haha.

My reasoning being no need to spend $2000 on a 911 specific muffler if you can get two generics for $130 apiece and pay your exhaust guy $500 to make it all fit and look pretty!

would be worthwhile asking opinion of a good exhaust shop I think.

SSI's too restrictive if it's for 3.2.

Edited by clutch-monkey

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@clutch-monkey I like the cheapness of your solution and as sandy468 said too, simple & cheap is a good thing... the result is probably same for a fraction of the cost. Will look into the "magnaflow" suggestion more.... thanks. 

On the SSI's, yes, that's what I've been told, too restrictive for my 3.6 but Stu at Nineauto was a definite "yeah-nah phil, the SSI is fine!"

@michel, I just youtubed scart.... sounds great! Hmmm... will check it out! 

 

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@clutch-monkey I like the cheapness of your solution and as sandy468 said too, simple & cheap is a good thing... the result is probably same for a fraction of the cost. Will look into the "magnaflow" suggestion more.... thanks.

 

these are the fabspeed extractors i have

diJ5Vh1.jpg?2

 

you can see on my car they hang low since there is no bumper that far down compared to 964

WBHmRqq.jpg?1

 

for this car i ended up doing the opposite of my suggestion above; keeping the fabspeed muffler and having tuned length extractors made in a flatter profile for $1100. Either method is effective at making something that fits your car better than a bolt-in system from a manufacturer three continents away etc

qgWHvza.jpg?1

 

Edited by clutch-monkey

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I would watch out just chucking on a bigger throttle body. Doing something like that is going to mess with your factory tune, so you would want to make sure you retune the ECU for any changes like that.

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First exhaust for sound, then ECU tune/chip for HP and calibration of new exhaust

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There is a lot of confusion about SSI's. The original SSI's are not optimal for anything over 3.0l. BUT......you can get SSI's with a bigger internal diameter and these work fine for bigger engines. IIRC, there is also a difference between the 3.2 SSI's and the 964 ones, although I think it is just the flanges. The added problem is that SSI is a brand while others do equivalent headers, so the key is to know what size they are, which isn't that simple because some quote external diameter and others quote internal diameter.

I hope that is as clear as mud.........:ph34r: 

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There is a lot of confusion about SSI's. The original SSI's are not optimal for anything over 3.0l. BUT......you can get SSI's with a bigger internal diameter and these work fine for bigger engines. IIRC, there is also a difference between the 3.2 SSI's and the 964 ones, although I think it is just the flanges. The added problem is that SSI is a brand while others do equivalent headers, so the key is to know what size they are, which isn't that simple because some quote external diameter and others quote internal diameter.

I hope that is as clear as mud.........:ph34r: 

Yep, I was googling last night and found larger ones on 'autoatlanta' site... says its for a 3.6 engine & seem to be larger diam but I couldn't decipher the specs exactly.  They were pricey though. Other forums, people saying too small, restrictive & referring to the original copies for the 2.7 and mentioning the 3.0 litre limit too. 

these are the fabspeed extractors i have

diJ5Vh1.jpg?2

 

you can see on my car they hang low since there is no bumper that far down compared to 964

WBHmRqq.jpg?1

 

for this car i ended up doing the opposite of my suggestion above; keeping the fabspeed muffler and having tuned length extractors made in a flatter profile for $1100. Either method is effective at making something that fits your car better than a bolt-in system from a manufacturer three continents away etc

My car is same as your orange one....  and I definitely wouldnt want that look, no offence... :(

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Phil,do you know if the ECU is stock 993? If it is I believe it is pretty fruitless chasing exhaust related HP without some serious nerd fiddling.

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Yep, I was googling last night and found larger ones on 'autoatlanta' site... says its for a 3.6 engine & seem to be larger diam but I couldn't decipher the specs exactly.  They were pricey though. Other forums, people saying too small, restrictive & referring to the original copies for the 2.7 and mentioning the 3.0 litre limit too. 

My car is same as your orange one....  and I definitely wouldnt want that look, no offence... :(

none taken that's why had custom ones made.. Might be the way to go

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There is a lot of confusion about SSI's. The original SSI's are not optimal for anything over 3.0l. BUT......you can get SSI's with a bigger internal diameter and these work fine for bigger engines. IIRC, there is also a difference between the 3.2 SSI's and the 964 ones, although I think it is just the flanges. The added problem is that SSI is a brand while others do equivalent headers, so the key is to know what size they are, which isn't that simple because some quote external diameter and others quote internal diameter.

I hope that is as clear as mud.........:ph34r: 

I spoke with a certain Peter Starr yesterday and he said SSIs primaries are fine on a 3.6, but he modifies the secondaries for a few different reasons, one of them being they're too small.  There is complexity to this stuff as there are trade off like gas velocity for mid range torque versus restriction for top end power.  Then there is the sound of course, and you also will want heat correct?  So headers won't do the job for you.  I highly doubt the zorst is going to make any difference in power, So really all you're chasing is the sound, and there's nothing wrong with that.  My GT3 probably loses power with the after market exhaust but it makes me feel like I'm faster and makes me happy.

My vote is keep the current headers and get someone who knows what rear muffler makes a nice sound and get them to figure the job out and send you the bill.  Or drill holes in what you've got.

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