boost from boot to boot

[iXe<30]

I want to cam my m20 and all supporting mods valve springs, injectors, headers etc. Then next spring add a rear mounted turbo :shock:. If im going for 12psi which size turbo should i shoot for? I think ill need the smallest possible to avoid lag from the extra ic piping? I plan to elliminate the spare tire hump which will give loads of room. Any suggestions?

[lolcantturn]

Why?

[iXe<30]

Why?

For some reason its really appealing to me... lower running temps and i can get better flow from the headers and imo the engine bay will look way better with headers and vs a turbo kit... I could go on but regardless i want to do this but im unsure which turbo to go for for a decently quick spool

[redsubdivisions]

Good luck. Being different is always cool, but if that rids efficiency, then you are being stupid. Top mount it and call it a day.

[iXe<30]

I don't feel it will rid efficiency with the proper turbo. Correct me if im wrong. Also, Ive heard that these rear setups are great for prolonged boost/reliability.... which i would like ALOT. Might not happen, but well see.

[downforce22]

I don't feel it will rid efficiency with the proper turbo. Correct me if im wrong. Also, Ive heard that these rear setups are great for prolonged boost/reliability.... which i would like ALOT. Might not happen, but well see.

Not sure what you are going for, besides maybe a stealth type turbo, but mounting a turbo charger in the rear seems rather pointless. You would need to route the exhaust gasses all the way to the spare tire hole (correct me if I am understanding this wrong) and then re-route that air intake charge back to the intake in the FRONT of the car. Not only would you have terrible pressure losses in the piping, you would have abnormally long turbo lag as well as lots of piping underneath the car.

There is already plenty of room under the engine bay for this, even in an iX. It has been done before. The only benfit I see is that a longer charge pipe would cool the gasses entering the turbo charger and give a cooler air intake charge (possibly) from a longer route. But what you would make up in power gains would be lost in turbo lag. You can do this with a simple heat exchanger anyway to achieve the same thing...

It is essentially like making a car with more doors. Yes it would be more efficient at hauling people, but after about 5 doors are added it becomes impractical, complex, and hard to implement. I suggest sticking with a known to work setup. And if you don't know why the principals I am talking about affect the setup I would recommend doing more research on turbochargers, heat exchangers, and how one choice can affect an entire system. A simple system can have prolonged reliability if you design it correctly and tune it well.

Good luck, and look up maximum boost by corky bell, he explains why one system works better vs another.

[e30leigh]

im not saying go for this by any means.... i dont like the idea of them.

however meny v8s have run this set up with from what ive seen was good results.
yes you need a smaller turbine, however you need a larger compressor to accually shift the air. so its a real hit and miss as to response and flow. and the right sized turbo.

yes there is pressure drop to be had. alot of it.

yes there is power gains from the cooler air charge. custom air intakes can be used in the back for the turbo. use a blow through for the maf in the engine bay. with the piping.

you will have to run piping under the car. unless you want to run it inside. but there goes your interior space. and it could be hot and burn people or melt the interior.
you will have to keep your intercooler piping heat insulated and away from the exhuast otherwise its completely undone any advantages and you just have a turbo in the boot with alot of lag.

also ride height will need to be kept up. risk of scrapping holes in the system could be huge. and the biggest issue you are going to encounter. is the oil (and if it has it, water) supply to the turbo. and also the return. extra pumps may need to be fitted in the boot to get the liquids there and back again. both high pressure to feed oil and low pressure to return it to the sump. these are going to be super hot! so they will need to be under the car. no doubt.

there is alot of extra work and money involved. for what is a stealth look and possibly a super loud turbo sound that no-one can find.

its up to you. there some tips on what needs to be done.

[ak-]

Let him do it. It's fun to watch.
Make a build thread about it.

[devon.818]

you have to run more like 18psi to get 12psi at your intake.

[Curt Hayes]

Pressure drops would just depend on the piping diameter. My concern is that you'll have a lot of heat loss between the head and the turbo, which will kill your efficiency. Turbos work better the hotter the inlet temperature. That heat is converted into the energy that drives the compressor. So you either need to insulate the crap out of the exhaust pipe or live with much reduced efficiency. Newest v-8 BMW engines are reverse-flow, with the turbos tucked into the vee. Keeps the pipes nice and short for minimum heat loss.
If you do build this, do make it a thread so we can all watch.

[The Humjet]

OP, to me this idea of running your turbo all the way at the back of the car and cutting your the spare wheel well sounds like a total head fuck especially for something that's gonna give you probably worse off results. Due to not only the pressure drops in the longer charge pipes but also the heat loss from the manifold to the turbine housing which will result in a greater spool up time, and possible boost control issues.
Let's not forget where are you gonna find the room for all these pipes with the e30's small undercarriage space. Where are you gonna mount the mufflers, how are you gonna get oil to the turbo and back.
Ideally you'll want the pressures from the exhaust collectors and the pressures from the inlet manifold to be 1-2% of each other. In order to archive this you'll have to have well designed turbo and inlet manifold, properly sized up charge pipes and intercooler, a good exhaust system and a nice camshaft to make use of a highly efficient setup. What your planning to do sounds like a big shambles to me.
I understand you want a neat looking engine bay. FWIW I'd drop an LS3 with a cam and a set of extractors. It will look good and will make 400+whp with zero lag.

[LowR3V'in]

Put the crack pipe down.

[iXe<30]

Thanks guys, once i get some cashola together i will start a thread and let you know how it goes.

[einstein57]

Turbo location should not determine what size you get. If you do the math 8 feet of plumbing will be filled faster then you can count.

[iXe<30]

Turbo location should not determine what size you get. If you do the math 8 feet of plumbing will be filled faster then you can count.

True... e30s are practically a square...