View Full Version : Air filters and cooling ST165

06-09-2009, 01:06 AM
On the 165, the stock car suffers really badly from heat management under the bonnet.

Increase the boost, and the temps just get worse.

Few observations and tips from my own experience.

1. If you are not getting rid of the battery, keep the stock air box and go for a panel filter. I junked the standard box and fitted a Blitz SUS filter, pointless in the stock location, it gets only hot air from the fan etc. I am convinced I actually lost power when I first fitted the Blitz.
Where is my filter here going to get decent volume of cool air??

2. Look at ways to vent the bonnet, I cut out two triangles above the turbo, fitted mesh and away you go. Possibly not as effective as a proper scoop, but its a great way to let the latent heat from the turbo escape.

3. If you can move the battery, fit a straight intake and get the filter better positioned... However, bear in mind that the engine fan sits just infront of the filter, so all that hot air, gets sucked in.. still not great.

4. The stock rad is not great, engine cooling on these tightly packed bays is at a premuim, look to upgrade to a decent rad. Otherwise, your cooling will always be marginal.
If you do go aftermarket, make sure you have a good air tight seal round the edge of the rad, I am doing this very soon, it forces the air though the rad, rather than finding ways round the rad.

5. I cheated and got rid of the AFM, and then finally got my Filter to work as it should, by building a cold air box.
It was constructed from Foamex, covered in Nimbus heat shield, sealed with draught excluder taper and foam. It has three feeds, one from the wing with my vents cut into it. A proper aero guy will tell you that these vents need to be different to work really well, but it does help,. a further scoop from underneath ( not to low as it gets thrashed in the wet) and from a small pipe under the headlight space.
Prior to cold air box fitment.

Cold air box

6. lag your down pipe, and keep the turbo heat shield, lots of people junk this, IMO thats a mistake if you still have the stock turbo housing and manifold. Get some extra heat protection on the manifold and it really does help.

7. Check and protect your sensors. The temp system in the 165 is complicated, with multiple temp sensors, found in the rad base and the water elbow. I replaced all three when they started to give strang signals, they commonly fail due to age and heat, and by the time they go, it may be to late to stop further damage. It is costly, but it saved me doing a further head swap. I plan to fit digital temp sensors soon, but its well worth checking the OEM ones.

8. O2 wires, they get cooked by the downpipe, mine were destroyed by heat, giving intermitent error codes and driving issues. you can get univeraal sensors cheap enough and its easy to add heat protection to the wires.

I have stripped out the AC to further help the cooling, although the extra mocal rads and FMIC do restrict this a bit

Hope this helps a bit.. all my opinion, based on driving the car and track times with the different filter set ups.

06-09-2009, 01:17 AM
Nice write up ol' boy!

06-09-2009, 01:18 AM
wing and bonnet pics



joe's gt
06-09-2009, 03:19 AM
Beautiful work. How'd you get rid of the AFM? Full blown ems?

06-09-2009, 03:20 AM
Beautiful work. How'd you get rid of the AFM? Full blown ems?
Yes, took the plunge and went to a Haltech unit. big cost but well well worth it for the benefits.

06-09-2009, 06:07 AM
Dude, I don't care if I'm NA, I'm totally cutting those vents in my hood. My benefit will be minimal, but they look freaking sweet!

06-09-2009, 06:14 AM
its actually pretty easy, if you look at the suport struts in the frame of the bonnet, you will see the shape is already there ready to cut out. A steady hand and plenty of time and you should be done.

06-09-2009, 06:38 AM
I removed the rear weatherstrip from the back of the bonnet near the air vent intakes. Really helps get the heat out, especially when it sits idle.

Car could really use a full cowl imho and should be sealed on the bottom of the bay (think a piece of metal or plastic covering the bottom of the bay from the front to just behind the tires).

Sealing the radiator to the body is a good idea. An even better one would be to make ducting all the way from the front of the bumper so that the entry to the core is guided, tapering in towards the nose. A duct with a taper like so puts MUCH more air through than flat surface where pressure escapes sideways.

06-09-2009, 06:45 AM
Rear strip was first thing I did, cheers,

I still have all the OEM under trays on the car, so the bay is sealed a bit. What do you mean by cowl? a scoop?

ducting is great idea, but in practice would be pretty hard for me to achieve, as I have the rads for the power steering and gearbox, in front of the rad as well. having said that, I could knock up some plastic shields for both sides to stop the air leaking round.

Cheers for feedback..appreciate it all.

06-09-2009, 07:34 AM
Always nice to see a clean 4th Gen. Nice and sensible mods. Glad to have you aboard.

06-09-2009, 07:48 AM
I still have all the OEM under trays on the car, so the bay is sealed a bit. What do you mean by cowl? a scoop?


(wtf is up with that car?)

The raised area makes an area of low pressure towards the rear.

06-09-2009, 09:26 AM
Arh see what you mean, unless I can afford a custom Carbon job, I dont think I will be able to stretch to that.
I did try raising the back of the bonnet, but I was un happy with the way it flexed and moved on track. It is not the strongest thing in the world.

cheers for the pic now understand :-)

BTW that car looks....er um, different?

06-09-2009, 01:48 PM
holy crap a sunfire!!! lol.

edit: or is that a sunbird?

06-09-2009, 01:55 PM
cavalier z24 i think...or maybe not even z24

06-09-2009, 02:10 PM
This is great stuff, heat management should be on everyones list near the top! For sure these cars do not vent out the heat very well under the hood.

06-09-2009, 02:25 PM
mine does good now! lol.
look at the grill chris.

06-09-2009, 05:10 PM
Sunbird. The little Pontiac emblem should have given it away.

GM actually made a turbo Sunbird there for a stretch in the 80s.

06-09-2009, 05:20 PM
I thought it looked a bit like our Cavalier models in the UK. part of the "j" car range?

on Topic lol, There are so many ways to vent the hood, the only drawback I have is that you have to factor in weather protection, I left mine outside one time and it rained all night. Took a while for everything to dry out. ( mine normally hides in a garage for the night ) so if you do vent the bonnet, possibly think about a way of protecting the bay at night if your car is left out all the time.

06-09-2009, 05:30 PM
Hey Rich, you need to get some more pics of your GT4 on here. Too many people have forgotten just how beautiful a 4th Gen can be when taken care of properly.

06-09-2009, 05:34 PM
hi fella, loaded up the garage section, and a bit in the motorsports section, reckon, people will be sick off poor Trinity.

good to share info on here. as with other sites, its great to hear everyones viewpoint.

06-09-2009, 05:53 PM
Phenolic spacer + wrapping the intake manifold or coating it would do a bit more if you want to get crazy. I had mine coated inside and out, cost $160. After the IC thermal barriers EVERYWHERE. :runaway: I'd be the happiest man alive to get high pressure, ambient air to the valve.

06-09-2009, 06:46 PM
I thought it looked a bit like our Cavalier models in the UK. part of the "j" car range?

Yes, the Sunbird and the Cavalier are J-Bodies. Completely unreliable but fun while they last. I have owned a small handful of them, the Z24 model with the 2.8 V6 was a little bit of fun, till you blow the headgasket and cook the whole motor.


06-09-2009, 07:34 PM
Phenolic spacer + wrapping the intake manifold or coating it would do a bit more if you want to get crazy. I had mine coated inside and out, cost $160. After the IC thermal barriers EVERYWHERE. :runaway: I'd be the happiest man alive to get high pressure, ambient air to the valve.

One day I will go crazy with Cermaic coating, I have spare manifolds sitting ready.

Money and time... never enough of both.

06-09-2009, 10:24 PM
we never do.

06-09-2009, 10:31 PM
we never do.


06-22-2009, 07:08 AM
If you remove the weather stripping from the back of the hood, Wouldn't that introduce a lot of problems on a DD? Water in various components or all that heat getting sucked into the air intakes for the cabin air system?

I don't have AC in mine, so not only does it get hot under the hood, it gets stupid hot inside as well.

06-22-2009, 07:18 AM
never had any isssues re the re strip, the only time I could see the air being sucked in is if you sat in the car for long periods stationary.

06-25-2009, 04:55 PM
Pulled my strip off last night. Had never occurred to me before. :)

I notice you have Redline decals under the hood...are you running water wetter? Any thoughts on that? I'm thinking of using some on my ASI radiator - I suspect part of the negative results some have found might be that it is closer to the turbo and DP area as it is thicker, and now seeing some localized boiling as a result...

I also completely agree with you on that airbox. When I first installed my straight intake, I certainly lost power. The ECU promptly pulled timing back as intake temps got too hot. It was absolutely necessary to build a box.

Here was my first attempt. It didn't work out so well as the aluminum sheet I used was too thin.


Since moving to a better intercooler, the ECU did not seem to respond to the open filter, however, I have now decided to build myself a new box.

I also have a hose running from my bumper up to feed cool air to the filter:


Then I moved to the ST185RC intercooler after doing the swap, ended up like this:


Lastly, the ST205 IC and ditched the AFM:


06-25-2009, 07:49 PM
I used the water wetter in my CC when I had it, worked really well, but I am not convnced of its worth with the main engine. I noticed a fair bit of corrision in my charge cooler pipes when I was stripping the system out.

IMO airboxes need to have proper lids to help stop hot air leaking into the intake. too many systems I see just rely on a tight seal with the bonnet, which too me does not work that well, it flexes while you drive and stationary, the panel heats up in sunlight.

What rad do you use with the charge cooler, I had great results, even with the 165 cooler, by upgrading the rad, to an actual car one, I used rad that had both fixings at one end, which made plumbing in easier.

I was then able to use the rads factory temp sensor to moniotor the water temps.
VWs are good sources off suitable rads.

06-25-2009, 08:00 PM
Fans on the IC rad are an enormous boost to cooling capacity. Water wetter works by reducing surface tension. I tried using a little bit of dish soap, and it did the same thing :hehe: I still use the water wetter though because of it's lubricating and anti-corrosive properties.

06-25-2009, 08:55 PM
I use this one, measures 29" x 5.5" x 2.5"


I'll update this thread when my newest airbox is fitted. I started on it last night, will run the whole right side up to the strut tower, similar to the fensport way...

06-26-2009, 04:45 AM
Nice, I'll be interested to see that :) Next thing I'm doing is a battery relocate and a staight air intake. Probably going to stop by the local wrecker and see if I can source a better IC rad and maybe if I get really lucky, I'll stumble across a 205 IC.

ChrisD, in your third picture you have 2 additional hoses, is that for a water injection system?

06-26-2009, 03:43 PM
Which hoses do you mean?

06-26-2009, 05:48 PM
The hoses look like they are for the catch can?

Look forward to the pics off the airbox.

Have you kept all your under body shielding? I have found that the car runs a fraction cooler with them in place.

06-26-2009, 06:59 PM
ahh k, catch can makes sense.

I gotta put my shielding back in place, after I find proper nuts/bolts for it. When I first removed it, all the screws sheared right off >:/

06-26-2009, 10:42 PM
yeah its not unusual to suffer sheared ones on the heat sheild, I did one, just means getting busy with the drill and the easi outs lol

06-29-2009, 06:17 PM
A good penetrating oil is a must have when working on old cars like ours.... :D

06-29-2009, 07:08 PM
oh yes!! that and a good long breaker bar!

06-29-2009, 08:00 PM
and lots of headache medicine.

06-30-2009, 04:54 AM
and lots of headache medicine.
Yes. Also a hammer. I use the hammer alot. Probably much more than I should. :hehe:

07-20-2009, 06:05 PM
New air box! Next step, wrapping the intake pipe and downpipe too.


and a pre-sticker shot:


07-20-2009, 06:14 PM
NICE BOX! make me one!

07-20-2009, 06:27 PM
lol, i think my patience for building such a thing is about used up. :P

Maybe about 5 hours total of work.

07-20-2009, 07:10 PM
Nice Chris :bigthumbu

Definite motivation for me to do mine.

07-20-2009, 08:13 PM
very sweet indeed!! love it

07-21-2009, 04:21 AM
Looks spectacular, Excellent job man

07-21-2009, 06:14 AM
Beautiful :bigthumbu

07-21-2009, 03:51 PM
Awsome! I was planning on doing the same but I still have the bulky afm :(

08-21-2009, 04:02 AM
Nice thread, lot of good tips.