Rear mount turbo,does this setup sound ok?
 

Hey guys,

I'm hoping to get some input on the specs of my rear mount turbo setup.From the searching i've done on this site some people will say 'don't bother just put it under the bonnet' so i'll say it now it's not going to happen :)

This setup will be going on a 2005 Mitsubishi Magna (Diamante) manual 3.5l V6 running LPG and i'll be aiming for 190-200kw@wheels on 5psi.

To make it easy i'll describe the setup from start to finish.After the RPW headers are merged a Tial MRV-R wastegate will sit just before the cat and will VTA,the exhaust (2.4'') will continue on up to the turbo (headers and exhaust pipe to be wrapped in Titanium wrap).The turbo i've been recommended is a CT46262 with a T3 .82 exhaust housing (i think .64 would be more ideal) with triplex ceramic bearing core so no need to run oil lines or a scavenge pump,it will take the place of the current rear muffler.

The turbo will suck through a 4'' intake pipe with the pod mounted up as high as possible to minimize the chance of sucking up water.The compressed air will run back down the car and up into the engine bay and about 20cm away from the MAF will be a Synapse BOV which when off boost will allow the turbo system to be bypassed which will give better off boost throttle response and economy.Boost will be run at the wastegate pressure of 5psi.

The fuel system won't have to be touched as the car will only start on petrol then once warm will automatically switch to LPG which has enough capacity for the power i'm after.

I'll be using the lesser known Profire ECU which has been specifically designed for the use of petrol and LPG (runs a seperate fuel and ignition map for each fuel)

I'm happy to listen to suggestions :)

Thanks.

That's quite a list. though i know little up front about the CT4 - 6262 turbocharger, i think that you still need to run a water line (water only / no oil) to the CHRA. i will research some more. Those triple ceramic ball bearings do sound quite promising. i would just be a tad hesitant at not using any kind of lubricant or coolant.

Venting to atmo prior to the cat might be cause for pause. Wastegates can leak. this might affect how your Cat behaves. maybe place the wastegate much closer to the turbo. And the wastegate will run cooler, and might enjoy a longer life span. also cooler exhaust gas temps will be nicer to gate, imho.

make sure the Synapse BOV is UPSTREAM of the MAF. ie... air filter - turbo - bov - maf - throttle plate - intake mani. and make sure you filter the BOV... you don't want foriegn contaminants to sneak in through the BOV while it is open.

LPG... low pressure gas correct? interesting.

sounds like you have the basics covered. let us know how it proceeds.

Hey ronmer thanks for you're reply,

Yer i will be running a coolant line i just forgot to mention it.

I would have thought leakage would be minimal with a genuine Tial?? yer i agree running a part at a lower temp usually does result in alonger life span,but i'm prepared to sacrifice longevity for better placement and noise.

Yep got that sorted,i'm rigging up the BOV so it breathes through the stock airbox to keep the off boost inlet temps cool and the noise to a minimum.

LPG - liquid petroleum gas,it has an octane rating of 102-108RON.

if you have to run a coolant line, it will still need a scavange pump. it just wont be as critical pressure wise.

A genuine TIAL will not leak.... initially. but over time, EVERYTHING FAILS. it's just that simple.

Great idea on throating the BOV back into the stock airbox! When it is vacuum it uses the filter to get clean air, and when it vents boost, it puts it back into a clean location, brilliant!

Hey Kurt. Why is a scavenge pump necessary for the coolant loop? There isn't a pressure loss across the CHRA or much of one so why won't it circulate itself? Supply coolant from pre-thermostat and return to intake side of water pump?

Be careful when deciphering the octane rating of LPG, over here in Australia the lpg (propane) is spiked with a percentage of butane, which lowers the octane rating somewhat! Two other factors that reduce the octane rating of lpg are the heat of the inducted air/lpg mix, and the intake velocity into the chamber, the faster the air/lpg mix the lower the det. threshold. Water injection can counter the detonation problem, as can the newer injected lpg systems which inject the gas from a liquified state, causing charge cooling (and a large power gain) just like petrol does (or "gas" does in the u.s.a.).

I've perused their site a bit, you definitely need to still run a coolant line to the turbo, this will be the only form of cooling.

One of the cornerstones of ceramic ball bearing performance is the need for very little lubrication. Lubrication causes drag. It looks to me like CT uses 3 sealed ceramic ball bearings in a sleeve which is inserted into the CHRA. The sleeve is then surrounded by some type of oil which is used as a heat sink between it and the CHRA.

I wonder how hard it would be to make this kinda sleeve and modify my TD05 CHRA. I've pressed bearings into steel sleeves I've turned down from steel pipe for oversized hole applications. The right tools and sequence would be important.

Metric...you have a point..rethinking the need for a coolant scvg pump...you are probably correct in not needing one.

The only thing I dislike about a Remote Mount Turbo is a scavenge pump system. It seems like the weak link to me, maybe just a mental block, I dunno.

Have you looked at what Comp Turbo has done with angular contact ceramic ball bearings? This mod would not only provide the benefits of ball bearings but also remove the need for an oil supply loop with a scavenge pump. The loose tolerances they talk about on their website make it sound real easy to make not to mention lots better longevity in a remote mount due to less heat to begin with and better cooling.

I wonder if a sealed bearing could be used in a remote mount application due to the lower heat involved. They talk about a grease they use that can be reapplied as necessary instead of oil. A sealed ceramic ball bearing would have the right amount of grease and it wouldn't migrate away from where it needs to stay.

I searched but didn't find much discussion here on making a ceramic ball bearing upgrade to a traditional design, which surprises me being a DIY turbo HomeMadeTurbo site. Have you found any sites that go into this more?

The car will be doing very low mileage so it should last a few years hopefully.

Cheers! yer seems so obvious but i've yet to see it done.

Interesting thanks for the info,i will be telling them to go ultra safe on the tune so hopefully that is enough but i am thinking of putting in one of Frozen Boosts W2A systems if it'll go inline under the car.

Yer as i said in my first post So with regards to the turbo does anyone think it's too big? i mean i want early spool but i don't want the turbo hitting a brick wall way before redline either.

Sorry buddy, didn't mean to hijack your thread, I found it searching for something else.

-How did you determine the 2.4" pipe size after the cat to the turbo?

-How big is the charge piping from turbo to BOV?

Did CompTurbo recommend this turbo? It covers a wide range of displacement, 1.5 to 6.0 liter engines.

I am curious if anyone here has made their own ball bearing cartridge similar to how CT does theirs and this thread came up when I was searching. I wish I had the cash to get one of theirs.

Ohhh ok all good.

It's the general consensus within the magna community that 2.4'' is the diameter of the stock exhaust piping.

I'm still unsure on that..perhaps 2.25''?

Yep CompTurbo recommended this turbo,just seems like overkill given i'm only looking for 350hp@flywheel.

I called to get a quote too and the smaller turbo was more expensive than the next size up, probably due to popularity.

So, it is a common practice with a rearmount/remote mount to run OE size exhaust tubing to the turbo? For a Miata OE is around 2" OD and the preferred cat back tubing size for a naturally aspirated engine is 2.25". I was planning on running 2.5" but I suppose the size of the turbine determines the restriction and anything larger will just slow velocity.

Yep that's the way i understand it.

Can i ask what they quoted you for the CT46262 with the triplex ceramic bearing core?

I didn't get a quote for that one, I believe it was a T3 frame with just the triple ceramic, oil-less option. I don't recall exactly but around $1,500 or so.

Not too bad.

What did they quote you for the CT46262 and with what options?

Haven't recieved a price yet.

Has anyone considered using a power steering pump to provide oil pressure and scavenge return for a rear mount turbo?

A popular mod for Miata's is to depower the steering rack. Gives much better feel at speed and is just a bit harder when stopped. Once moving at all it gets easy. The pump can make crazy pressure when dead headed, up into the 1000's of PSI. Using a return style fuel pressure regulator should make getting 30psi possible.

Not everyone will be able to do this as losing PS is not a realistic option on some cars.

Sounds a little big. I would move down to a CT4-5862http://www.turbosource.com/CT4-Series-s/1876.htm