Cast iron 4:2 exhaust manifolds
- Thread starter Dr.Jeff
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Dr.Jeff
True Classic
The muffler layout has possibilities.
Are any of those greater than 2" inlet? I think that will be the difficult part of using something from a stock import with a small engine. I also wonder what level of flow they allow internally; between the 90 degree junctions and the stock vehicle quiet noise level I'd imagine they aren't exactly performance exhausts. Naturally I'm referring to ones from standard production vehicles. The one Janis shows looks to be an aftermarket unit so it's likely a better design (is "Simons" a custom exhaust maker?).
Are any of those greater than 2" inlet? I think that will be the difficult part of using something from a stock import with a small engine. I also wonder what level of flow they allow internally; between the 90 degree junctions and the stock vehicle quiet noise level I'd imagine they aren't exactly performance exhausts. Naturally I'm referring to ones from standard production vehicles. The one Janis shows looks to be an aftermarket unit so it's likely a better design (is "Simons" a custom exhaust maker?).
AKimball92
True Classic
The stock Miata muffler looks possible. Obviously not plug and play but if the dimensions fit that center inlet could be used with the 2-1 downpipe going below the cross member like mine. Mods would be needed to incoperate the hangers designed to take the rubber mounts and not our noisy springs. Or you could flip it over, and have the 2-1 go above the cross member and contain almost zero bends before the muffler. There's so many aftermarket options for the Miata that surely one would fit our design quite nicely if the space is anywhere close to the same as the X1/9. One could always weld extensions to the outlets if the X1/9 is slightly wider, not likely able to shorten if its too big.
rx1900
1981 X1/9
Yeah.....the stock Miata muffler looked to have potential. A while back I even bought one to see if it would work.
In theory.....it should be a good choice.....the center inlet should line up near a spot where a simple 2-1 downpipe would go under the crossmember and almost directly into it. That should be easy with just a couple of bends. My plan was to have the two tailpipes exit through the rear grill - my desired look. That would involve some cutting/rotating of the tailpipes. And of course fabricating some hangers.
In theory.....it should be a good choice......inlet size is about right - not too big......and surely should have easily enough flow - I think Miatas of that vintage (2006-2015 ish) were 2 litres with maybe 140 hp. And you would certainly think the Mazda engineers made it as less restrictive as possible to maximize performance.
In theory....it should be a good choice...the stock OE Miata muffler is a really nice quality piece - I think it is stainless - and comes with nice polished stainless tips that could surely be re-used. And you can get them pretty cheap barely used from someone who has upgraded to a performance muffler. I got mine for like $50 and it looks like new.
But.....in reality....i'm not sure. Fitting it appears to be a bit of a challenge. In person it is much larger than it appears in photos. And there is not a lot of room back there in an X1/9. As I recall, it pretty much fills all the available space. And as it is, the spacing between the tailpipes is slightly too wide to fit. They would have to be cut and tucked in closer to the muffler. And i have no idea what the sound or performance will be like. On the Miata, there is also a resonator further ahead in the system.
Yes, there are lots of performance mufflers out there for a Miata. And some would even appear to have a smaller muffler body that the stock one. So may be easier to fit. But most are quite expensive, and spending several hundred $ for one and then hacking it apart would seem to be kinda silly.....
So.....the jury is still out. I know others here like myself have bought one to try. Cant recall anyone who got further than I did........
AKimball92
True Classic
that is understandable. All I had to go by was the picture alone. We all are continuously searching for modern and convenient parts that could easily work in our cars. That is all, but those looking to keep originality.
Dr.Jeff
True Classic
Although I'm not familiar with the MX5 muffler, I agree that a lot of the factory stock mufflers are very large. I'm sure that is a way for them to get the noise level down without sacrificing a lot of flow resistance.
Now that the Miata is a Fiat 124, I guess using a muffler from one is still retaining at least some Fiat originality.
rx1900
1981 X1/9
Yup....you are correct. Generally - for a muffler - the bigger the better !!! Should - in theory - sound and flow great. But makes fitting more difficult. See the pic below for some perspective. For sure the Miata muffler is larger than it appears in the pic. Note the X1/9 rear grill behind it. If...you want the tailpipes to go out through that grill, you can see it will be......tight....And it would pretty much take up all the space in the X1/9's muffler cavity. Note the size of the large Saab muffler in front of it.
I think it will fit - just - but I have yet to have the cajones to chop the tailpipes off it to be able to try to insert the muffler can into the X1/9 cavity. Look at my muffler - it is almost new. As it is, I could always sell the intact muffler to some Miata owner who is tired of the fart-can performance muffler the previous owner put on. I think new they are about $700 US from Mazda.
I can tell you that the inlet on the Miata muffler is about 2.25" ID. And the tailpipes are 2" OD. So larger than you would expect. You would probably be happy with that Jeff. I reckon those are a bit too large for an X1/9 - at least in a stock-ish engine spec.
The Saab muffler would be a much easier fit. But would limit you a single tailpipe out the stock location. It has about a 1.9" ID inlet, and a 1.7" OD outlet. Much more suitable I reckon.....But by the way, the Saab 900 Turbo muffler is identical except for larger inlet and outlet pipes. And probably less restrictive innards.
I'm always on the lookout for something better.....
I think it will fit - just - but I have yet to have the cajones to chop the tailpipes off it to be able to try to insert the muffler can into the X1/9 cavity. Look at my muffler - it is almost new. As it is, I could always sell the intact muffler to some Miata owner who is tired of the fart-can performance muffler the previous owner put on. I think new they are about $700 US from Mazda.
I can tell you that the inlet on the Miata muffler is about 2.25" ID. And the tailpipes are 2" OD. So larger than you would expect. You would probably be happy with that Jeff. I reckon those are a bit too large for an X1/9 - at least in a stock-ish engine spec.
The Saab muffler would be a much easier fit. But would limit you a single tailpipe out the stock location. It has about a 1.9" ID inlet, and a 1.7" OD outlet. Much more suitable I reckon.....But by the way, the Saab 900 Turbo muffler is identical except for larger inlet and outlet pipes. And probably less restrictive innards.
I'm always on the lookout for something better.....
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Dr.Jeff
True Classic
That last one pictured kind of reminds me of some of the really early Porsche 356/VW Beetle mufflers. But I don't recall the actual configuration of the in/out-lets. Seems there were a few older makes of cars that had a similar type of mid entry like that. But they would have really small diameter pipes. The "sport" versions that were considered performance replacements usually went away from the mid-entry design. I assume they found better flow with other configurations. But it would depend on the internal design as to how restrictive it is.
AKimball92
True Classic
Here's an update on my exhaust 4-2-1 set up. Fully complete and installed. Once I get it running these weekend (fingers crossed) I will see how well everything fits and if any leaks. it runs just shy of an inch from the engine cradle and the rear cross member. If heat is an issue I'll have to fab up a shield for that location. I tried to move, shake, and bump everything as hard as I could and nothing came close to contacting the frame or crossmember. It also tucks up above the jacking point, a requirement I made for myself to allow for 2x4 assistance when jacking up the car. The welds are not as good as I would like or used to be able to do but this is the first time welding in the last ~4 years and getting SS to be the correct color is not easy at all.
dllubin
Don
Looks like the safety tabs on your rear cross member bolts are not set (ie. bent). Just happened to notice since I'm doing mine today.
AKimball92
True Classic
Thanks! I should bend them up. For now I will paint mark them and go from there. I hate to bend them and unbend them the next day should something need changed. I'll probably be under the car every date after each drive for the next good while. When the car gets trustworthy I'll lock them down correctly.
dllubin
Don
That is pretty much the same reason I have not bent mine back until now. I finally got the engine and rear suspension back in and just need to bleed the rear brakes and put the tires on. I plan to fire it up while it is still in the air and if nothing weird happens, I'll bend the tabs!
AKimball92
True Classic
Thanks Doc. Jeff. I TIG welded it work here, not my machine, gas, or rod but certainly better than any machine I could afford. The tubing is all 304L and the braided flex is 304 I believe. The rod they had was 308L. I hope that's not an issue but its all they had and they said they use it on all the SS metal that comes in so if any complaints, we're splitting hairs. I welded TIG for 5 years senior year of HS all through college but very little SS. It needs to be much cooler. I knew I was overheating the joint and discussed it with the guy at the shop. He says most of his SS welds are gold in color and if he overheats it too much its blue... I was happen to see even a bit of blue in my welds with most of the blue rainbows being outside the weld. When gray like that, it's almost low carbon steel by then...
Dr.Jeff
True Classic
That's my biggest problem in working with SS, I don't have the right welding equipment for it. And I hate having to take parts to a welder, then work on it more, then go back for more welding, etc. I'm sure yours is way more than sufficient and will have no problems. You should see some of the stuff I've found from "professional" shops.
kmead
Old enough to know better
Looks great, fine work.
A stupid question or two. When you come out of the engine bay you take a 90 turn to the drivers side of the car, then a u-turn to meet the OE muffler. In your mind if one were to instead take a sharp right towards the passenger side, is there enough room to then take that u-turn to go back across could one go into a catalytic converter and then the second U turn into the OE muffler?
Or is there just not enough room to fit the cat under there with this arrangement?
Thanks
A stupid question or two. When you come out of the engine bay you take a 90 turn to the drivers side of the car, then a u-turn to meet the OE muffler. In your mind if one were to instead take a sharp right towards the passenger side, is there enough room to then take that u-turn to go back across could one go into a catalytic converter and then the second U turn into the OE muffler?
Or is there just not enough room to fit the cat under there with this arrangement?
Thanks
Dr.Jeff
True Classic
When I was looking at how I want to make mine, I did not try that specific layout, but having played around with several ideas it seems it would be difficult to do that. To get two U-bends in there they would have to be very tight radius. And the type of muffler and cat would both need to be a very narrow design. There is some room to go up/down as well as back/front. So you might find a way to partially overlap them at different levels, while criss-crossing to each side. Another factor would be the changes in direction of the gas flow with the snaking back and forth. But that might not be a big issue.
As a side note. The notion of crossing side to side twice reminds me of another thing I found while planning mine. Regarding the total length of the exhaust, to try and maximize efficiency for a target power band. I assumed it would be difficult to get enough overall system length tucked away in the limited space. I envisioned having to do as you describe and cross back again just to make the pipes long enough. But that proved not to be the case. I was surprised how quickly the total length added up with just a basic routing; there was no need to try and work extra tubing into it.
AKimball92
True Classic
If you remember I really wanted to keep that Cat set up, maybe with new joints that aren't seized studs and stud springs magically held in place (bolt heads snapped off but springs wont budge). I just did not have the stomach to do the secondaries through the frame wall since the bends would be so complex. Also, my system costs 242 for the pipes and another 60 for the SS bracket. I didnt believe if it was worth it to buy more U bends to me to keep the cat. Also after my research and shopping around I went with Ace Race Parts for the tubing.