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Old 01-01-2008, 06:36 AM   #7
Process West
Former Vendor
Vendor Sales Rating: (0)
Member#: 71459
Join Date: Sep 2004
Location: Sydney, Australia
2008 STi Silver
R Spec


Originally Posted by scoobienoobienoo View Post
Well all, after all the great things I've read about the Process West TMIC design and arguments made for efficient airflow and optimal core thickness design, I decided to plunk down the $1086 shipped from MastroWRX for both the TMIC and air splitter.

A note about my application: I have an '06 STi with a Cobb TBE and AP V2. I have in hand a part list including an FP Green turbo (ported, 2.4" inlet, 7cm exhaust, internally wastegated), 850 cc deatschwerks fuel injectors, 255 lph Walbro fuel pump, Buschur Racing CAI, and Buschur Racing uppipe. I wanted to run a a mid-high 11s daily driven street car with a stealthy top mount.

What really appealed to me about the PW TMIC design was the thought process involved and efficiency arguments. I really appreciated the way they considered airflow and heat exchange and weren't about to just cram the largest chunk of aluminum they could squeeze under the hood. The pictures on the website and other forums show a very impressive improvement over the WRX with substantial core size increase and truly impressive matching airsplitter designs, which truly are a very nice upgrade for a WRX. Dyno curves were supplied showing improvements and part of the promised testing was supposed to be a direct comparison of a stock STi TMIC with the PW TMIC. I am not able to find these test results. Anyway, I approved of the methodology and decided to go for it anyway. I called Mastro to ask about the TMIC and was told that it really was a substantial TMIC and would be a good upgrade for an STi. SOLD!

So, I received the PW TMIC and splitter on 12/17/2007. The following are photos comparing the stock STi components with the PW components:

TMIC comparison....

At first glance, I am hard pressed to tell any real size difference at all between the two. Sure, the internals may flow differently, but it's nowhere near as obvious an improvement as over the WRX TMIC. So I get out a measuring tape. Along the cooling fins, there is no measureable difference along the short direction and thickness that I can tell, and the PW is about 2 cm larger in the long direction. Also note that the stock TMIC has about 34 columns of fins compared to about 27 on the PW TMIC. In terms of heat exchange, the STi TMIC appears to have MORE surface area as more fins are packed into the same area/volume. The cooling fins on the stock TMIC are also connected by a wing shape as opposed to a block shape on the PW TMIC. The implication being that air would flow with less turbulence through the stock TMIC design. Of course, I cannot compare the internals. So this is my own external inspection.

Top view:

Side view:

Again, externally there appears to be little difference.

One major difference between the two TMIC's that I think is very clever of the stock STi TMIC is the lip which is actually designed to mate to the stock air splitter like a sleeve. I will show how this comes into play later.

Now I will directly compare the air splitters. I unbolted the stock STi air splitter and you are looking at the bottom of both of them (or the side that mates to the the intercooler). What is immediately striking is that the PW TMIC opening appears to be very similar to the stock STi air splitter. Actually the PW splitter is a bit larger and would sit on top of the PW TMIC or on top of the lip on the stock STi TMIC where the stock STi splitter is slightly smaller and designed to fit inside the lip. Another obvious thing is that the PW splitter does appear to provide far superior cooling to the turbo as seen on the left side of the picture. I should also note that I did not apply the seal that was included with the PW splitter as I was keeping the parts in mint condition for my inspection.

Another air splitter comparison.

Now shown is the PW air splitter on top of the stock STi TMIC for placement purposes. What is shocking to me is that after all the arguments about channeling max air flow through the TMIC that the design is reliant upon a seal resting in place. To me this seems inferior to the sleeve type design of the stock STi splitter/TMIC interface. It does not matter that the PW splitter is on the STi TMIC and not the PW TMIC. Its going to be press fit either way and the top of the PW TMIC actually angles DOWN away from the center of the TMIC. This design would be more prone to air leaking out than the stock design.

PW splitter shown on top of stock STi TMIC:
Stock STi splitter shown on on top of stock STi TMIC:

For fun, I took a side photo comparison of the two. Pretend that there is no lip and the seal is in place on the PW TMIC. To me it seems obvious that the sleeve type design is better. Nevermind that there does not appear to be any substantial gains in surface area to be had by the PW splitter.

As for the PW air splitter itself, I wasn't overly impressed with the craftmanship of the piece that I received. There were several warped areas in the metal. It just wasn't a quality piece like the PW TMIC. The PW TMIC was a very nice piece and the assembly work was top notch. Here are some photos of the PW air splitter that I received. The item was packaged poorly and there was a ding where it poked through the box and maybe you could attribute one slight bend to that. However, there were several unacceptable flaws in the construction. I spent a lot of money on my car and the PW product. It should be a nice flush finish without any bending required.

So, I felt like I had purchased a TMIC with quality construction. However, all of the air flow arguments no longer made sense to me and it was not clear in any way to me that this WAS in fact an upgrade for an STi. I looked around for a while and still can not find a single dyno plot where a stock STi TMIC was compared with a PW TMIC.

I decided to ask Kevin at PW about it. I PM'ed Process West at NASIOC and again emailed at the process west website. I wanted to give them a chance to make me feel good about my purchase and explain technically why this was an upgrade for an STi as I truly cannot readily see for myself.

I sent the following on 12/17/2007.

I received no response whatsoever. I still have not received a response and it is 12/28/2007. I wanted PW to tell me, yes this is an upgrade for the STi and here is why. Here is our test result. Because of this, I have to conclude that there are minimal if any gains to be had for the STi using this setup. So after 5 business days I decided enough was enough and called Mastro to express my concerns and inquire about sending the items back.

Funny enough, Manny at Mastro told me that he had the PW on his STi and did not see any power gains at all, but it 'ran cooler'. Well, being the empirical engineer that I am, that's not good enough for me. I asked to send the items back. Manny told me he'd check with management since he wasn't authorized to make that call and that they don't take performance parts back, but he'd have the manager call me back on 12/26/2007 since he wasn't in. Instead of a call, I got the following email on 12/26/2007:

Now I'm pretty sure this email is from Manny who just told me he didn't see any gains at all with his PW TMIC on his STi. So I called back and asked to speak to the manager (Joe). He wasn't in. So I waited till 12/27/2007. I got the feeling from Joe that Manny never consulted him, and just told me they couldn't take the parts back. Joe helped me out. Thank you very much, Joe, for being a gentleman! I'm a fair guy. I'm not trying to take advantage. I wasn't asking for them to pay shipping. I'm not trying to get something for nothing. I offered to pay the restocking fee since I don't feel this intercooler is for me and I did not feel I should have to pay any restocking fee for the air splitter since I do not feel it was a quality product. Anyway, thanks again Mastro for taking the parts back.

To make a long story short, I believe the PW TMIC is a high quality piece and a very excellent upgrade for a WRX. I feel the PW air splitter is also a very good upgrade for a WRX, but the craftmanship of the piece I received was poor. Do I think it's worth $1086? Not really, probably you can get the same results for a lot less with the stock STi TMIC and air splitter. You can also drill your own holes in the stock splitter for better turbo cooling. However, I do not think that this product should be marketed as an upgrade for the STi until there is testing that shows a definite quanitfiable improvement. If there is testing showing this, then I apologize profusely, but this information should be readily available and shown very publicly.

Im sorry to read this.

I didnt recieve a PM from you..(untill I had a look in my inbox now) .I dont visit here every day and I also dont recieve email notification when I get a new PM (dont know why).

Also didnt recieve a email.

1. If you have an STi you should NOT have been sold a dont need it..use the factory splitter. If fact you will go backwards using my splitter with the STi hood scoop. My splitter is designed to suit the internal shape of a WRX hood scoop and hence you will have a large gap between the top of the splitter and your hood scoop.

2. My intercooler is much thicker than the Sti intercooler. My intercooler is 90mm thick....the Sti intercooler is 60mm thick....measure the actual core...not the plates on the side of the intercooler which are much thicker than the actual core.

3. Do some intercooler outlet temperature measurements and you will see the difference...especially for pro-longed periods..(like a circuit)...the difference is night and day.

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Last edited by Process West; 01-01-2008 at 07:23 AM.
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