"remote" mount turbo

If I do a "remote" mount turbo in my X1/9 placing the turbo inside where the rear "trunk" is now, it would solve a few issues for me. I wouldn't need to relocate my alternator and the turbo would be suffeciently high enough not to have to worry about an external oil scavenge pump to return the oil (I was inistially planning on hanging the turbo off the stock manifold using an adapter - but that presented it's own problems as well)

It looks like the it will take less than 30" of pipe (including the manifold) from the exhaust ports to the turbine housing. The turbo will be a Mitsubishi TD04-12b from a Volvo 740. I am shooting for 130-ish hp, as I think that is about all the driveline can handle (Jonny P said he broke axles at 150-ish hp and broke his tranny at 175ish hp)

The car is my daily driver and occasional autocrosser (classes be damned, who cares!).

I know my "remote" isn't all that remote, but does anyone have experiance with a remote mount turbo for a 4cyl?

they seem to me like a terrible idea from an efficiency standpoint but people do it and it works. I mean you're loosing energy in the distance to the turbine and you're adding lag with the distance from the compressor. On a mid or rear engine car at least it wouldn't be so bad.

Given that it's an X1/9, the distance would be nothing. It's more like extending the engine bay.

Don't have a 'remote' mount, but I have studied them and done flow calcs for a V8. The real issue is exhaust gas expansion, or contraction in this case since the exhaust gas will have time to cool before hitting the turbine, i.e. less volume because of less heat of the gas. Squires Turbo Systems FAQ has a decent explanation if you're not up on your thermodynamics. Basically you're going to want a smaller turbine/housing to create enough backpressure to spool the turbo in a reasonable amount of time. I'm not sure what my guess would be as to what you're going to need for a turbo, but it'll be one of the smaller guys and may require hybridization to get the turbine spin up the compressor to cover your RPM range better. You're going to need to spend some time figuring out your flow map over your RPM range (descriptions of the procedure are covered all over the web). And then start comparing w/compressor maps. The trick here is figuring out how to size the turbine relative to the compressor to achieve the sameish map.

Squires says: "Front mounted turbos typically run an A/R ratio turbine housing about 2 sizes larger because the velocity is already in the gasses and the volume is so big that the turbine housing must be larger to not cause a major restriction in the exhaust system ......"

I say find the right compressor map for your engine, find the next two smaller turbos, get the turbine A/Rs off of each, figure out if they can be hybridized, if not get the compressor w/the smallest A/R, and live with turbo-lag. You could always go the opposite way and 'undersize' the turbo but you're going to need a VERY large external wastegate or two to make sure you don't overspin the turbo...

Goodluck, I'm interested in seeing how this goes!

(P.S. we have an intake length on our XR4Ti of near 10 feet of 2.5" with intercooler on a front mount setup and it's no big deal, the added volume is trivial and doesn't add any noticable lag on the intake size, and with a properly sized turbine it should feel just the same as a front mount)

Raze wrote: (P.S. we have an intake length on our XR4Ti of near 10 feet of 2.5" with intercooler on a front mount setup and it's no big deal, the added volume is trivial and doesn't add any noticable lag on the intake size, and with a properly sized turbine it should feel just the same as a front mount)

It's all relative. Temporarily disconnect your front mount setup and just run a 12" section of pipe from the turbo to your tb like they came from the factory. I bet you feel it.

Chuck Mallett does this to Pontiac Solstices. He told me the turbo lag is negligible.

belteshazzar wrote:

Raze wrote: (P.S. we have an intake length on our XR4Ti of near 10 feet of 2.5" with intercooler on a front mount setup and it's no big deal, the added volume is trivial and doesn't add any noticable lag on the intake size, and with a properly sized turbine it should feel just the same as a front mount)

It's all relative. Temporarily disconnect your front mount setup and just run a 12" section of pipe from the turbo to your tb like they came from the factory. I bet you feel it.

Um, considering we have an Holset HY35 on there instead of the puny stock T3 it's still going to lag :) That combined with the stock non-intercooled charge temp of over 170°F and the resulting timing map and fuel map changes in MegaSquirt would make be debate whether or not there'd be any difference whatsoever...

If we really want to make this point moot, get a variable geometry turbo, drive it electronically or mechanically, doesn't matter, get the A/R down to where you need it and open it up as you need it. It would be overkill for a 4cyl, and most are VERY heavy (the VGT Holsets are close to 50 lbs) but still it would solve pretty much all compressor sizing problems up front, during tuning you'd actually have to work out what size A/R you need :)

Just mount it on the muffler...

Build your own "log" manifold and mount the turbo where you want to.

JGSTurbo DIY Manifolds

Just use the universal kit, pic out the turbo flange you need and have a manifold flange cut on a water jet (or heck, use some basic metal shop tools) If you ask nicely, I'll build you one since I have a 1500 sitting on the floor in my garage and I'll time after the new year since my contract will be up.

From there, I would use a smaller turbo, after all the Exxie only has 1500cc's to spin the turbo. Tons of small Mitusbishi's turbos (TE04H) are available on Chrysler 2.2 and 2.5 turbos, the great thing about these turbos are that they are sized for a 1.6 to 2.0L motor and the Turbo-Dodge folks don't want them since they are too small for the 2.2/2.5.

Take the flange and the log manifold parts to a welder/machinist to have the main part of the manifold welded up. Take it home, mock up where the turbo will hang and mark it off on the manifold, go back to the machinist to finish it up.

Once the manifold is done and the turbo is hung, then you have to fit the coolant and oil plumbing lines in place. This means, fitting an oil drain back in the cast alloy oil pan. The intake and exhaust plumbing are relatively easy to work out after the previously mentioned pieces are sorted.

Resize the exhaust gas side and you'll never notice the difference. All the turbos I know come from the factory sized for near engine placement, but there's nothing inherently wrong with running the turbo further away, you just have to compensate for the (slighly) smaller volume of gas.

Of course I'd probably try it stock first and if you are dissatisfied with the response then look for a smaller gas side housing.