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Discussion Starter #1
I just finished installing my custom turbo kit; it's a Holset hx35. The kit was originally put together by another member on these forums. Hot side piping is 2.5", the intercooler has a 2" in/out and cold side is 3" running to the stock throttle body. The turbo is huge so full boost doesn't come on until almost 4700 rpms but is my intercooler creating a choke point because of its size compared to the hotside and coldside piping? Also, would upgrading to a larger throttle body help with restrictions for my set up? Let me know what you guys think
 

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Jeez, that thing is huge on a focus. That HX35 pulls my 8k pound truck pretty good, I couldnt imagine it on a 3k pound car.

As far as the question goes, I know my intercooler on my truck is HUGE. I dont know if its that big for the size of the turbos that go on there, or what, but the small one on a focus could cause issues, I think. Dont quote me on that.
 

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It all has to work together, like JFrye mentioned above man thats a pretty good size turbo. On a n/a dtech the t/b is noticeable off idle.
 

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As I said, I cant be of much help on here as I have never done a F/I focus, but that thing is huge. I have seen quite a few of the Mitsubishi guys running a HX35 on Talons/Eclipses, and on some Evos, so if you cant find an answer on here, maybe you can snoop around some of those forums to see what they are running. That might give you an idea of what to look for that will fit a focus, and go from there.
 

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I have no issues with 2 inch from the turbo to the IC and 2.5 from the IC to the TB

By doing 2 inch it helps to spool ever so slightly quicker , if your 3 inch from the IC to the TB you could gain 1 maybe 200 rpm quicker spooling

It also makes a difference how the piping is run and how many turns or tight turns there are in the piping

As stated that is a big turbo so will be very slow to spool

Tom
 

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Discussion Starter #6
I have no issues with 2 inch from the turbo to the IC and 2.5 from the IC to the TB

By doing 2 inch it helps to spool ever so slightly quicker , if your 3 inch from the IC to the TB you could gain 1 maybe 200 rpm quicker spooling

It also makes a difference how the piping is run and how many turns or tight turns there are in the piping

As stated that is a big turbo so will be very slow to spool

Tom
Yeah, the plumbing probably isn't the most ideal route but it isn't terrible. I might change it around later on down the road. What are your thoughts on the stock throttle body?

Btw, your last tune was good. I should have a datalog for you sometime during the week.
John
 

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Discussion Starter #8
Just ordered an intercooler with a 2.5" inlet/outlet. Should flow a little better considering my current set up. So now, it will be 2.5" hotside, 2.5" intercooler, 3" coldside. I will eventually upgrade the throttle body to CFM's 67mm. I have a shorty K&N filter on the turbo because it is the only thing that fits. I wonder if that is adding any restriction.
 

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Discussion Starter #10
Can you not get any pipe between the filter and the turbo ? even if you can only get 4-5 inches it would be better then none

Tom
There is literally no room because the turbo sits so low. There are two linkage cables in the way. One of them can be moved a little so I'm going to see I can somehow get some piping on there or maybe even a silicone elbow and route the piping upwards
 

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C2H5OH
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What kind of pressure?
Because 4,700 seems really high if you're on low boost (under 12psi).

The neat thing about the twin scrolls is that you can spool sooner. But this also takes a well designed ex manifold. The typical open merge won't cut it. You want a divided merge; 1/3, 2/4.
Or if you're not going to build the correct manifold, you can bandage it by blocking one side of the scroll temporarily:

 

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Discussion Starter #12
What kind of pressure?
Because 4,700 seems really high if you're on low boost (under 12psi).

The neat thing about the twin scrolls is that you can spool sooner. But this also takes a well designed ex manifold. The typical open merge won't cut it. You want a divided merge; 1/3, 2/4.
Or if you're not going to build the correct manifold, you can bandage it by blocking one side of the scroll temporarily:

Yeah, 4700 is high but I'm not too far off. DSM guys are seeing 4300-4400 for full boost with hx35 when running an undivided manifold. The cast iron manifold I'm using is undivided. I've heard how a divided manifold can increase spool by 500 rpms which is crazy. That will probably be an upgrade later on down the road; a custom divided manifold for this beast.
 

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Think about it, 500 earlier on the ex mods, plus 500 earlier on the intake mods. That 3,700rpm'ish. One hell of a difference in power band.

Right now I'd bet you shift at redline and fall out of boost for the first little bit. Just think how much quicker the car would be if you had full boost after each shift ...
 

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Discussion Starter #14
Think about it, 500 earlier on the ex mods, plus 500 earlier on the intake mods. That 3,700rpm'ish. One hell of a difference in power band.

Right now I'd bet you shift at redline and fall out of boost for the first little bit. Just think how much quicker the car would be if you had full boost after each shift ...
I haven't pushed it too much because Tom and I aren't done tuning but I can guarantee that it most definitely will fall out of boost for the first little bit when I shift. You're right; 3700 versus 4700 is huge. Does anyone make a divided turbo manifold for the duratec?
 

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Fins Up!
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something is wrong there. i have an hx35 on a 1.8l miata

i hit full boost (currently 17psi) between 3000 and 3100 in 4th with 4.10 gears. it will hit full boost at 30% throttle in any gear but first at 3700 rpm.

my intercooler piping is 2.25 hot 2.5 cold 2.75 in/out on intercooler. 3" turbo back exhaust and a log manifold with open scroll t4i housing and 38mm wg

if you are running a open manifold with a divided housing you need to change that b/c that will kill spool. one way to avoid building an obscene manifold is to get a aftermarket exhaust housing that is a std t3 .63 or .70 ar.

 

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Discussion Starter #19 (Edited)
something is wrong there. i have an hx35 on a 1.8l miata

i hit full boost (currently 17psi) between 3000 and 3100 in 4th with 4.10 gears. it will hit full boost at 30% throttle in any gear but first at 3700 rpm.

my intercooler piping is 2.25 hot 2.5 cold 2.75 in/out on intercooler. 3" turbo back exhaust and a log manifold with open scroll t4i housing and 38mm wg

if you are running a open manifold with a divided housing you need to change that b/c that will kill spool. one way to avoid building an obscene manifold is to get a aftermarket exhaust housing that is a std t3 .63 or .70 ar.


First off, your Miata looks badass haha Can the open manifold running into a divided turbine housing really hurt spool that much? I'm just going off what the DSM guys have done but there's been a bunch who have ran this particular setup with good spool. My current setup has a lot of room for improvement. I really think the correct size intercooler, larger TB, and a larger air filter with piping will make a difference. I can almost guarantee that the shorty K&N filter I have directly on the turbo now is choking it up. I think I may be able to get a silicone elbow on there and route piping towards the front of the car with a larger filter.

I do like the idea of a standard t3 housing though. Obviously a ton cheaper than paying for a custom manifold; I'm going to look into it.
 

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Discussion Starter #20
Also, does a standard (undivided) t3 housing for the hx35 even exist?
 
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