st165 Downpipe

Q&A regarding engines, turbos, and intercoolers and power upgrades

st165 Downpipe

Postby yoursymphonyinc » Tue Sep 21, 2004 7:30 am

So i'm considering a DP as a place to start improving my car (Because although the 165 is EXTREEMLY fun to drive, its just plain underpowered for the feeling i want)

i notice 935 sells them for $300. They recomend buying the midpipe for $315 as well. I've been told that with a new DP, you can expect a raise of about 15HP. This puts the 165 near 200HP-ish. My questions are:

a) is this worth buying
b) is the midpipe that important
c) is a 15HP increase a big jump (like, will it be a noticeable jump in performance?... i'm a newbie)
d) any better ideas to get HP for cheap on a 165?
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Postby TexasAlltrac » Tue Sep 21, 2004 12:51 pm

First thing I would do is finish all maintenance items before you start upgrading. If those are done, then by all means, proceed to the mods.

Now, in my opinion, I would not purchase the DP until I was ready to go ahead and do the whole exhaust system. the 15HP gain is dependant on the condition of the rest of the exhaust in many respects.

Until you are ready to do the full exhaust package, hollow out the pre-cat. This is something I am doing on my ST165 tonight/tomorrow infact. My car looses boost progressively after 4000 RPM (as much as .2bar) and this should fix some of that as the exhaust is restricting airflow. This mod is very inexpensive, just labor intensive (but then so is a DP).

Another cheap mod is to get some aluminum flashing from Home Depot and build a heat shield for your intercooler.

You can go one step further and get a cone filter (I got the TRD one with adapter off Ebay for less than 30$. I just had to file out the opening some on the adapter to the mass-air as it was smaller than the mass-air inlet). I then used the same aluminum flashing around bubble-type insulation and built a cold-air seperator for the filter. Afterwhich I ran a 4" aluminum flex-pipe up from just behind the front airdam to feed air to the filter at speed.

All four of these mods (IC shield, filter, cold air box, cold-air pipe) combined made a huge difference in performance for me even though the stock 7psi boost remains unchanged. My intake temps are dramatically less. I am easily at 200 crank HP even before I have messed with the exhaust, though I think that some turbo and some exhaust work was done by the previous owner.

The bill was less than 50$ all told. If I can borrow a digital camera, I will make you some photos.

~Todd who is having a slow day at work...
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Postby yoursymphonyinc » Tue Sep 21, 2004 6:04 pm

Thanks for the speedy reply Todd, i'd LOVE to see some pics of that heat shield and especially some of the cold air box/pipe. feel free to post or email them to me (yoursymphonyinc@hotmail.com)

As far are hollowing out the pre-cat, i was told that basically involved taking out the stock downpipe, and banging out the ceramic parts inside, but that you're still left with some iron parts restricting airflow, any information you have on this procedure would be great to have too (beacuase cheap and labor intensive i can do, its the damn $ i dont have right now.... stupid college...)

i've also heard that you can buy cone air filters with an adaptor for the 165 for about $60, although $30 does sound Nice.... again, i'd love to see how you installed it and removed the stock air filter box (send me lots of pics! :D )

thanks man
-Jim
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Postby TexasAlltrac » Tue Sep 21, 2004 6:10 pm

http://cgi.ebay.com/ebaymotors/ws/eBayI ... ename=WDVW

That is the one I bought...it is even cheaper now. It worked fine. I just had to file down the inlet on the cone adapter as it was slightly smaller than the inlet on my st165's mass air.

As to the pre-cat thing...I will be starting that tonight and will let you know what I find inside of it.
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Postby yoursymphonyinc » Tue Sep 21, 2004 7:16 pm

http://cgi.ebay.com/ebaymotors/ws/eBayI ... ename=WDVW

i found this one after looking at the one you bought.... it Seems to be ideal for our cars... we'll see.... when i get my student loans, i'll probably try buying one since its such an easy upgrade.

any other info i'd need to install (like, ducting air to it..?)
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Postby yoursymphonyinc » Thu Sep 23, 2004 2:15 am

anybody got pictures of new Downpipes in 165s?
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Postby TexasAlltrac » Fri Sep 24, 2004 6:58 pm

Well, I am about to go home and hollow out the pre-cat. I took some test whacks at it last night and with a large chisel (I am using a ball-joint seperator), and a hammer, it should go fast.

Mine was very blocked up, so i should be spooling much faster when I am done.

I build a manual boost controller at the same time and will run 8psi till I get a BOV. I am expecting some noticable difference.

I will say this...pulling the turbo and manifold, and everything that went with it to get it off...was a royal pain!

I could do it in half the time now, but wow...breaking loose the bolts from the pre-cat to the midpipe....I almost broke my breaker-bar getting them loose.

Anyhow, Symphonyinc, I am about to have a 4"+ downpipe from the elbow to the mid-pipe. Pity the rest of the exhaust is just 2".

I took some pics of the process and also of my induction system and intercooler heat shield. I will post them once I get them developed and scanned in.

I will let you know how it goes.
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Postby Kyoto » Sun Sep 26, 2004 4:20 am

Anyhow, Symphonyinc, I am about to have a 4"+ downpipe from the elbow to the mid-pipe. Pity the rest of the exhaust is just 2".

If it was going into a 3" DP it wouldn't be so much of an issue, but isn't 4" into 2" a bit of a bottleneck?

See this thread: http://www.alltrac.net/phpBB2/viewtopic.php?t=1263

I put on a 3" Aussie pipe a while ago, i'll get you a pic as soon s the car gets back from the workshop.
Tim // Melbourne, Australia

1986 ST165. 152,000km on chassis
ST205 WRC engine / IC system / rear LSD with 82,000km
Blitz K1-380V
Apexi Power FC
Aussie 3" dump pipe to 3" catback system
TWM short shifter.
Whiteline front strut brace
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Postby alltrac.net » Sun Sep 26, 2004 5:39 am

I would suggest suspension BEFORE the exhaust system if possible. Upgrading the suspension makes it so fun to drive, you forget about the lack of power.

Also make sure your engine is running properly, no leaks etc, before you start modding.
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Postby yoursymphonyinc » Sun Sep 26, 2004 7:28 am

so, as far as upgrading the suspension in the 165, obviously some lowering and stronger springs, but what about struts? i'm damn poor and i'll have to install all myself probably (with help of course from a fellow alltrac owner!) what do you guys suggest for struts (thinking most bang for the buck, so to speak) ?
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Postby TexasAlltrac » Mon Sep 27, 2004 12:26 pm

The car is back together.

Here is what hollowing out the pre-cat accomplished:

I can hit peak boost below 3000 rpm and it holds to 6800 or so when it starts falling off again. It used to peak at 3500 and hold till 4500 before it would start dropping.

The car is much faster overall. Even though the boost level is unchanged, it pulls much harder. My clutch is having trouble holding in 3rd and 4th.

The car sounds much throatier. It is more like a V8 at idle with a low rumble and at full scream, is more of a deep roar than the 4-cylinder signature farting sound that you hear on the Honda/Acuras.

Overall, I am very happy with the results.

I can only imagine what a full 3" from the turbo to the tailpipe will do.

>If it was going into a 3" DP it wouldn't be so much of an issue, but isn't 4" into 2" a bit of a bottleneck?

Yes, 2" is an issue, but clearing out the pre-cat still made a huge diff.

Symphonic, if you are on a budget like I am, hollow the cat out and then go for a drive. I think you will be happy with the results long enough to save up the extra change you need to get the Aussie DP.
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Postby yoursymphonyinc » Mon Sep 27, 2004 6:16 pm

righton man! glad your car is running great now, i'm definatly going to have to hollow out my cat. so what was the hardest part of it all? did you just use a metal pipe to bang the cat out or what?
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Postby TexasAlltrac » Mon Sep 27, 2004 6:36 pm

Removal is a pain as the bolts are usually frozen at the lower 3-bolt flange to the mid-pipe. I almost broke my breaker bar on them. Ah the irony....

Here is a quick run down on what you will need to do:

Make sure the engine is COLD..otherwise you will not be very happy when you do this.

remove all the heatshielding. You will want to remove the alternator shield and oil filter too. Maybe remove the alternator just to allow more tool-room.

Loosen and unbolt the midpipe from the bottom of the pre-cat. Set the exhaust pipe off to the side.

Unbolt the side-mounts from the pre-cat.

Unbolt the pre-cat mounting bracket that is below the alternator.

Unbolt the elbow from the turbine housing.

At this point, you should be able to drop the pre-cat and elbow down to the ground (carefully)

Separate the elbow and the pre-cat.

Hollow out the pre-cat, clean all mating surfaces and reverse the uninstall process.

Start the car and make sure you do not find any exhaust leaks. If you do, make sure the bolts are tight. If you still have leaks, you will need to replace/install gaskets. Fortunantly, My cracked manifold was the only leak (or unfortantly...how ever you want to look at it).

-----

Once the cat was off, I was able to take my ball-joint splitter (sort of a two-pronged chisel) and a hammer and would hammer the splitter in about an inch at a time, and then pry out the ceramic material. I had it done in less than 5 minutes. I then sprayed some brake cleaner in and blew it out with an aircompressor.

Putting it all back together went much faster than taking it apart...a nice change.
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safety concerns

Postby tim » Tue Sep 28, 2004 12:47 pm

Please tell me you did this with some sort of protection over your mouth/nose! Removing the cat matrix produces phenomenally toxic dust. If you're oing to remove your cat, two things you can do to be safe are: 1) wear something over your mouth and nose to avoid breathing in the dust; and, 2) soak the cat with something like dishsoap....this helps to reduce the amount of dust.

Tim
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www.aussie-speed.com
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Postby TexasAlltrac » Tue Sep 28, 2004 1:54 pm

I guess I will be dead by week's end. :|
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