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Rear mounted turbo?
Been looking around the forum for a couple months now doing some research before I try anything or say anything stupid but...
I searched but couldn't find anything on this and was wondering if anyone had tried a rear mounted turbo on a miata. I know a friend who put an STS rear mount on his rx8 and is running 7-8 PSI pushing out about 350 RWHP. I'm not sure where there would be room for a turbo under a miata but it seemed like a decent idea to keep the engine bay temps down. I'd like to know what you guys thought about this system. Thanks in advance... STSturbo.com |
There is a guy on clubroadster doing it... the majority of us think he is silly for doing it. He's doing a much cleaner install this time around, still rigged in back a bit though.
On cars that don't have space to do it... its usefull. On cars with space... its stupid... period. |
there is plenty of room under there once you get rid of the factory muffler.
We toyed with the idea a bit for my daily driver before I settled on the BEGi S. the idea of having to run an additional pump(s) to get oil(& water) back there turned me off. |
The increased plumbing for both the charge piping and oiling isn't something I would want to deal with. Kurt Rohmer has threads here and miata.net about doing it. Most of his problems stem from not using the correct parts for any of his build. Everything he used was super cheap, such as rubber hose for charge piping.
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Originally Posted by paul
(Post 249106)
there is plenty of room under there once you get rid of the factory muffler.
We toyed with the idea a bit for my daily driver before I settled on the BEGi S. the idea of having to run an additional pump(s) to get oil(& water) back there turned me off. |
Yes, that's one of the reasons I considered it. That and I had a hard-on for keeping my RB 4:1 header for some reason.
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under the hood is the easier way of doing it. high engine bay temps aren't really a problem, just build it right.
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i don't see a problem with it but i tend to like different stuff. the miata does have a good amount of room back there i don't think that will be a problem. My only worry is the oil system, it's gotta be just right. in my mind they work better with bigger turbos and lower boost?
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That guy has no hair on his ass.
Lucky fuck. |
What about using a rear mount for a twincharged setup?
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Originally Posted by miatamania
(Post 249138)
What about using a rear mount for a twincharged setup?
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Originally Posted by miatamania
(Post 249138)
What about using a rear mount for a twincharged setup?
here's the link for anyone who cares- http://altaminiperformance.com/produ.../22/Twurbo-Kit |
imo its not worth the effort, especially since miatas have so much room under the hood for a proper turbo setup
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I know you CAN do it under the hood, I was just thinking of where a rear mount could actually help?
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on a gto or a corvette where there is little room under the hood i can see it working....IN FACT, the sts kits they tested on the vettes were VERY impressive
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Rear mount turbos are used when a turbo can not be confined closer to the engine in the traditional way. In a miata a remote mount would offer no real appreciable advantages. The added complexity sucks. Plus it will spool later.
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1 Attachment(s)
Attachment 213310
Volvo 440 turbo as its nice and small to minimize spool up time. Boost came in about 4k, lag was almost non-existant. Enough said. That toy of a turbo should spool fully during cranking. IIRC, it's a Garrett T2 compressor wheel and a T15 Turbine at .48 A/R. |
Rear mount turbo on a Miata is super awesome...
If you have an LSx in the engine bay! |
Originally Posted by Braineack
(Post 249255)
http://i156.photobucket.com/albums/t...awes/turbo.jpg
Enough said. That toy of a turbo should spool fully during cranking. IIRC, it's a Garrett T2 compressor wheel and a T15 Turbine at .48 A/R. Will it even hold up to a 2 mile test drive without falling apart. |
that piece of turd may hold up, but why in the fuck is that thing in the trunk?
Isn't the whole point of rear mount to save space, and you got plenty under the trunk... |
breathing in your exhaust leaks sure does cause you to make bad decisions.
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Originally Posted by y8s
(Post 249430)
breathing in your exhaust leaks sure does cause you to make bad decisions.
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no airflow = great heat = more iefficiency :jerkit:
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i dont know about rear mounts, but subaru mounts their turbos at least 30" from the cylinder head, and so does porsche to a lesser extent.
http://www.agency-power.com/catalog/...apheader4a.jpg Granted this is because of the packaging disadvantage these cars have, but what if the turbo is mounted just before the stock cat location in the miata? I'm sure a tiny KKK off a VW 1.8T or similar would fit there, and spool pretty well too. This would bring down the cost of the whole system, for example the manifold and downpipe wouldn't be needed. Of course, you'd still have to deal with problems like oil scavenging. The oil inlet and water lines wouldn't be an issue other than being freakishly longer than normal. |
but at the same time, there's plenty of room next to the engine, without the need of pumps and bracketry and this and that.
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Definitely, but I'm just thinking about the cost aspect of it. That's nearly $500 saved in parts alone for someone who's on a really tight budget. I'd have done it if I hadn't been this deep into my build. Even at the risk of getting ridiculed and laughed at.
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I'f I had to rig it that bad, I'd rather not Turbo at all.
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wow... that is hideous. Its not the greatest layout for a miata.
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haha i like that lsx comment. Ive sat in some of my classes daydreaming about just building an insane LSx miata with twin turboes mounted in the rear. I mean why not? ...
dont answer that |
The only good part about that rear mount in the trunk is you can fab a grill screen and to while tailgaiting after a good boosted run.
Would be pretty nice to have some steaks ready after a good mountain run. |
Originally Posted by The_Pipefather
(Post 249477)
i dont know about rear mounts, but subaru mounts their turbos at least 30" from the cylinder head, and so does porsche to a lesser extent.
http://www.agency-power.com/catalog/...apheader4a.jpg http://www.vividracing.com/catalog/w...wastegate7.jpg I'm sure a tiny KKK off a VW 1.8T or similar would fit there, and spool pretty well too. I think a WRX turbo would be a better choice, as it's nice and small and is frequently upgraded. |
:lol: man are you serius? I will give you props for asking intelegnetly but as my buds have said and shown a rearmount turbo is one of those if you can and wan to then do type things. There is so much room in our engine bays it isn't even funny man, turbos do not take up alot of room. And ceramic caoting is a great way to keep temps down. GL I hope you survive the initial hazzing cause you actualy seem intelegent. :bigtu: Just not knowledgable.
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Originally Posted by The_Pipefather
(Post 249477)
i dont know about rear mounts, but subaru mounts their turbos at least 30" from the cylinder head, and so does porsche to a lesser extent.
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Originally Posted by SolarYellow510
(Post 249755)
I've thought about the K03, because people take them off all the time. It spools off idle, but it runs out of flow and torque drops off rapidly after about 4800 rpm on a 1.8L. Even on a 1.6L, it would be small.
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the turbo being mounted where it is on a subaru doesnt have much to do with anything more than space...the place it sits pretty much is THE ONLY place you can mount it, and THE CLOSEST that they could get that sucker to the actual exhaust ports in heads.
take a look at my engine bay during turbo swap: http://i54.photobucket.com/albums/g9...Picture020.jpg there is BARELY any room in there as is now dont quote me on this, but i think the long header piping actually has something to do with subaru's generally having more torque than say evo's, while the evo's turbo sits mere inches away from teh engine, it holds boost all the way up top and usually has a little bit less torque and more peak power. on a subaru, even with a large turbo, the power usually peaks a bit before the redline and usually boost starts to taper, even using a large turbo and a mbc, it still tapers up top. so they usually have a SHITLOAD of torque come on in the midrange, and then start to die off towards the top....im assuming a rear mounted turbo kit would have more lag than normal, then have a ton of torque, and start to taper off up top pretty steep....which is kinda dumb: no lowend, no topend, just a mild push of torque exactly in the middle where its not here nor there.... feel free to correct me if im wrong.....i am merely speculating |
Originally Posted by 18psi
(Post 249798)
the turbo being mounted where it is on a subaru doesnt have much to do with anything more than space...the place it sits pretty much is THE ONLY place you can mount it, and THE CLOSEST that they could get that sucker to the actual exhaust ports in heads.
take a look at my engine bay during turbo swap: http://i54.photobucket.com/albums/g9...Picture020.jpg there is BARELY any room in there as is |
well they COULD raise the engine a bit and fit some small ass turbo in there, but that would be dumb as hell, not to mention kill the cars cornering/performance
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Then they'd also have to run a lot more intake piping
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haha o shit didnt even think about how fucked up the intake piping would have to be on a setup like that good point
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Which reminds me, rear turbo on a miata +1 for the bad idea. You mention not needing an intercooler because the charge air cools as it heads up to the motor anyways, but it also works against you because there is not a lot of exaust gasses to spool the turbo as is. Why let them cool that much before getting to the turbo? And throttle response will be balls
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Originally Posted by J.T.
(Post 249818)
...And throttle response will be balls
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Originally Posted by 2kBlk
(Post 249829)
The rules are different with forced induction. Charge pipe length has almost no effect on throttle response.
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Originally Posted by 2kBlk
(Post 249829)
The rules are different with forced induction. Charge pipe length has almost no effect on throttle response.
On another note, both throttle response and turbo lag will increase greatly by adding a lot more piping(although given a miata isn't THAT long, its still a good amount more piping). |
Ummm... I'm pretty sure that maximum boost says charge piping doesn't make a whole lot of difference unless you stretch it into the next county. been a while since I read it though.
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JT and 18psi, how tough do you think it is for Subaru to switch the position of the intake and exhaust ports on the cylinder head.........not very. With that they could have drastically shortened exhaust manifolding and also run a front mounted intercooler very easily.
Even with all those advantages they still didnt do it. I think its beyond me and you to speculate why. I'll take Corky's approach and say that Subaru knows a thing or two more about turbocharging than any of us here. Hence nothing wrong in copying their layout and giving it a shot. Speculating that one layout or the other is "balls" and "crap" without trying it, IMO, is stupid. But hey, no harm in following convention for the majority of us. |
Once the charge pipes is pressurized it has no affect, it may take a millisecond longer to pressurize in a rear mount situation. The delayed spool happens due to exhaust gases cooling of too much before reaching the turbo, loss of heat=loss of energy, so you need mroe exhausts gases to have same spool. End of story.
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Originally Posted by The_Pipefather
(Post 249919)
JT and 18psi, how tough do you think it is for Subaru to switch the position of the intake and exhaust ports on the cylinder head.........not very. With that they could have drastically shortened exhaust manifolding and also run a front mounted intercooler very easily.
Even with all those advantages they still didnt do it. I think its beyond me and you to speculate why. I'll take Corky's approach and say that Subaru knows a thing or two more about turbocharging than any of us here. Hence nothing wrong in copying their layout and giving it a shot. Speculating that one layout or the other is "balls" and "crap" without trying it, IMO, is stupid. But hey, no harm in following convention for the majority of us. I didnt say the setup was balls or crap I said throttle response and or turbo response. And to put the intake underneath would not work out too well, there isn't that much room under there(don't tell me there is I stand under them for 6+ hours a day. Plus where you gonna put the oil pan with that intake under there? It would likely take a strange setup with some really awkward super unequal runners. And 18psi knows a thing or two about subies too ;) Anyways, it might be able to be done with a dry sump system, but they weren't trying to make a super expensive supercar. Once the charge pipes is pressurized it has no affect, it may take a millisecond longer to pressurize in a rear mount situation. The delayed spool happens due to exhaust gases cooling of too much before reaching the turbo, loss of heat=loss of energy, so you need mroe exhausts gases to have same spool. End of story. |
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The "next county" comment is directed specifically at speed-density based ECUs where no AFM/MAF is used.
Originally Posted by Corky Bell in Maximum Boost
It is distinctly possible to upset the basic throttle response if an engine is equipped with an airflow meter positioned too far from the throttle body, Opening the throttle causes a low-pressure pulse to be created that travels up*stream toward the airflow meter, The time it takes this pulse to reach the flow-meter and cause it to react is indeed the delay in throttle response. Typically, such a pulse must travel from the throttle body to the intercooler, through the intercooler, back to the turbo, then to the flowmeter, in order for the flowmeter to register a response. It is not until the flowmeter receives this pulse that the air/fuel ratio can change to account for new load conditions in the engine. I should point out that there are exceptions here, based on the style of throttle-position sensor with which the engine is equipped. Nonetheless, it is generally true that the farther the throttle is from the airflow meter, the poorer the throttle response. Thus, this path length should receive some consideration in the design process.
When an engine is equipped with a speed density type of EFI system, wherein no airflow meter is utilized, or a blow-through carbureted turbo system, the length of the intake tract tan extend into the next county with no negative re*sults insofar as throttle response is concerned. The overall problem in designing an intercooler system, then, lies in maximizing the ability of the system to remove heat from the compressed air while not adversely affecting boost pressure, losing throttle response, or contributing to any delay in boost rise. |
Originally Posted by Joe Perez
(Post 250043)
The "next county" comment is directed specifically at speed-density based ECUs where no AFM/MAF is used.
Originally Posted by Corky Bell in Maximum Boost It is distinctly possible to upset the basic throttle response if an engine is equipped with an airflow meter positioned too far from the throttle body, Opening the throttle causes a low-pressure pulse to be created that travels up*stream toward the airflow meter, The time it takes this pulse to reach the flow-meter and cause it to react is indeed the delay in throttle response. Typically, such a pulse must travel from the throttle body to the intercooler, through the intercooler, back to the turbo, then to the flowmeter, in order for the flowmeter to register a response. It is not until the flowmeter receives this pulse that the air/fuel ratio can change to account for new load conditions in the engine. I should point out that there are exceptions here, based on the style of throttle-position sensor with which the engine is equipped. Nonetheless, it is generally true that the farther the throttle is from the airflow meter, the poorer the throttle response. Thus, this path length should receive some consideration in the design process. When an engine is equipped with a speed density type of EFI system, wherein no airflow meter is utilized, or a blow-through carbureted turbo system, the length of the intake tract tan extend into the next county with no negative re*sults insofar as throttle response is concerned. The overall problem in designing an intercooler system, then, lies in maximizing the ability of the system to remove heat from the compressed air while not adversely affecting boost pressure, losing throttle response, or contributing to any delay in boost rise. Thank you. Exactly what I've been trying to say, but couldn't find the passage. And anyways, when your out of boost and driving on the street your engine will be acting like a non turbo motor anyways. |
Actually, the quoted passage disagrees with what you said:
Originally Posted by J.T.
(Post 249833)
On another note, both throttle response and turbo lag will increase greatly by adding a lot more piping
BTW I wasnt alluding to you when I made that "balls" and "crap" statement. The point is, unless someone tries this setup (near the cat, not near the muffler), speculating on its performance is of no consequence. |
Originally Posted by Saml01
(Post 250038)
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I bet you that's a member here that still has not come forward to tell us he is using a rear mount for fear of Epic Flamage
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Originally Posted by Zabac
(Post 250090)
I bet you that's a member here that still has not come forward to tell us he is using a rear mount for fear of Epic Flamage
he was banned here before your time. |
Originally Posted by Braineack
(Post 250091)
he was banned here before your time.
BWAHhhhahahahahahaha |
Links? Was it Epic though? :giggle:
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Originally Posted by Zabac
(Post 250110)
Links? Was it Epic though? :giggle:
I did love his comments like (from his tuning video on youtube) "ran autotune on spark map last night, so that's worked out" 3:00 watch at the end in "boost" slowest 15psi ive ever seen, in matters of spool and speed of car. |
wow, looks like a total 'tard, that car moves abuot as fast as my stock 1.8.
Looks like the kinda guy who never had friends, and still doesn't. |
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