This is an Nasioc Post we made regarding our older T31 turbo kits and changes we made to make the kit better.
First off fitment issues with the PERRIN turbo kit, are not common. While we have had issues time to time, we have taken care of those who had them. I should say we have taken care of those who have called us and explained their problem. There are a lot of our kits out there, and of course when there are problems, people say €œHey I have a problem€, weather by calling or by posting on forums. Those who don€™t have problems, generally go happily on their way, and never say a word. So while it seems like a lot of kits don€™t fit, this is just not the case. We have many many satisfied customers and dealers who have complimented us on our kits, and how well they do fit.
While this is a hard part to install, we do get calls and comments about parts that are not fitting together well. Generally the customer just hasn€™t adjusted something correctly, or installed things out of sequence. To combat this we have changed instructions, and how the kit is €œpre-installed€, which has help quite a bit. Secondly we have taken extra measures to ensure each kit fits together perfectly before it leaves the building. This means that the uppipe and DP have both bee fit together to a turbine housing and to the WG to ensure all pieces mate together properly.
Complaints of fitment with WG v-band are very common. This is because this connection is very, very precise and it being off a little is very easy to spot. This concern is easily fixed by customers following the directions and preassembling the kit outside the car. Then you are not dealing with trying to fit and align it in tight quarters. As much as going to a 2 bolt type flange or WG would solve some problems, this is not something we are going to do. The compactness, and performance benefit of the larger 44mm WG is well worth it.
Originally we made our kit somewhat universal to other FMICs. While the connection from the turbo to the FMIC can be made, it was a little tricky to get just right. With our current kits we are shipping we simplified this quite a bit with a single Silicone hose that goes from the turbo to the FMIC connection. This Jog eliminates extra couplers, and pipes that caused some issues.
TURBO AND HOUSINGS
Lets go over a couple things with the housings. Like I have said many times before, and have shown many times before, there is no difference in the housings. We choose to use the housing we did (a long time ago), as this housing was much more compact, and was readily available from our turbo supplier. These are the T31 exhaust housings people are referring to. These housings are a T3 inlet and have a short 2.5€ outlet. The newer Garrett GT housing has the same T3 inlet but a longer 3€ outlet. With out saying anymore, people jump to the conclusion that the 3€ is better as it is bigger, because in a turbo exhaust system bigger IS better. You have to look at both housings and understand what makes them different, not better. First off the turbine wheel inducer for all these turbos are smaller than 2.5€, which means that in order for it to get to 3€, some flaring is done. Its in this flaring where things vary from the T31 to the Gt housing.
The T31 housing basically has no flare (inserter Office Space joke here). The end of the turbine wheel is very close to the flange where the DP bolts to. Our DP bolts to this and starts at 2.5€ then quickly is flared to 3€.
The GT housing is very long so it goes from the turbine wheel to the 3€ oulet in a couple of inches. Basically accomplishing the 3€ OD in the same distance as our kit with the 2.5€ outlet.
Since we have a Garrett Engineer assigned to us of course I proposed the question whats the difference, his exact response below.
€œWe have never run a test between the two housings for that exact turbine
wheel. (I asked hims specifically on the GT3582R ) We did do a test a different turbine wheel and the performance for the 2.5" housing was slightly less (on the order of the uncertainty of the measurement). I would suspect you would observe no performance difference.€
Add to that are some pictures showing the differences:
Proof is in the pudding!!!!!! (Not sure where that came from but I am sure Wikipedia has something on it) There are a couple of naysayers out there about this housing, but they are not comparing apples to apples. If this housing was so bad, then we would see some HP or spool differences in cars with GT housings, but this is just not the case. We have cars with Gt3076R w/.82 turbos and they spool around 4000, and make about 400WHP on pump gas, and 460 on race gas. This is the same thing seen on the GT housings, and in fact a somewhat local customer had one our kits modded for the GT housing, and his car spooled just like others, and made about the same HP as others. If this T31 exhaust housing was a choke, or a hindrance to the WRX€™s making power, I think there would be a lot more people complaining about how their car doesn€™t make enough power.
Regarding the support brace. This is a part we have developed a year or 2 after we release our kits. The brace is a very simple and effective brace that limits the €œpossibly€ damaging left and right vibrations. We say possibly as there are many turbo kits out there with no brace and have no issues. Because of the way the kit bolts to the car, it is somewhat braced in its self. This is why so far, there is no need for one.
We currently have braces in stock for the old GT35R, but since our kit is changing, we will not have braces for the other turbos for a while.
That should clear up peoples concerns about the kits performance and fitment issues.
Now onto the changes we have and are making. We are switching to the GT housing!! Since there are those who €œThink€ the T31 is not as good as the GT housing, what better way to satisfy everyone than to change to the GT housing! While we feel there is ZERO benefit in HP or spool, the other benefits are supply issues. Since the inception of our turbo kit, we have gone direct with Garrett, and getting the newer housings is much easier, as they are an off the shelf part. So switching housings forces a few things like DP and uppipe changes, which we have added more room around the WG, and clearance around the chassis. While our kit will hang a little lower, it will eliminate any issues with clearance with different motor mounts or slight variation in cars.
Blow thru boost tube
This is a part we have been selling for a while now, but it is change to the new kit because you HAVE to have it (or a stand alone ECU). We have found that this part makes tuning simpler, eliminates issues with stop and go traffic (making the MAF see high temps), nearly eliminates rich or lean conditions with leaks in boost tubes, or intake hose.
This is an item that was made for this future kit, as well as the old kit. No more silicone! Well at least big pieces of silicone. The new intake system is now a cold air tube that fits down in the fender well. While this part is a little trickier to install, it really cleans up the engine bay.
I like guys at Crawford performance, and in no way do we say they make a bad part. Both of us have great parts that fit people€™s needs. Their kit requires their FMIC, ours fits with our FMIC and other OEM turbo fitment types.
Your spool characteristics are probably right in line with what you would have had, if you just got a new turbo from us. Clark makes it seem like there is some huge difference, and this is just not the case. But going from a 4000-ish spool and adding 800-ish isn€™t that much different when it comes down to it. Also with the hit of power you have, it makes up for that loss of power right before the boost comes on.
Remember the T31 is a Garrett part, and its machined to fit the volute and the profile of the turbine wheel just like the GT housing. I agree that it would be nice to put the T31 housing debate to rest, but it will go on forever, as long as people keep using them. Your statement about why would Garrett come out with a new design is a good question. But the answer is simple. They had more demand from the gasoline performance world wanting bigger 3€ oulets to make it simpler to build exhaust systems. Garrett didn€™t change it to increase spool or performance. Yes, Garrett really pushes their new GT turbos as better spooling but this is because of change to Ball Bearings, not a change in the housings.
You definitely had a kit that wasn€™t correct. And like other people we would have taken care of you had you called us. I am sure you understand that, and I too understand that sometimes you just can€™t wait. You€™re in the middle of the project and something happens, and you just deal with it. Especially on the weekend, this is not something that can get fixed and it can be frustrating.
Regarding some of your CONs of the PERRIN kit.
We will never use a bellows anywhere on the kit. This is because they do not hold up to the temps and pressures seen before the turbo, or at the WG dump tube. We looked to using these a long time ago, and no one would guarantee theirs would hold up under 1600 degrees+ and deal with the pressure. Using one after the WG dump is an ok place, but it is not needed as the catbacks contain the flex.
The filter is a tuff one. If you understand how they work, there is no reason to have K&N on your mind. If it is a looks thing, well we are changing something there.
The oil drain is pretty simple, a flange, fitting, and hose connecting it to your OEM drain. Getting it nice and smooth is easy. This is not something we have had issues with.
Flanges welded to the outside. This is something we well also not change. Welds on the inside of the pipe or butted up to them, do not have very good support. The tubes will have better support if fit tightly to the ID of the flange, then welded on the outside. Welding on both sides is really bad with Stainless steel. This is because SS shrinks when you weld it, and it can cause stress on the weld when welded on both sides.
Regards to no BOV. I know where they got this info. At SEMA a couple years back Precision turbo was next to us and it came up in conversation. I thought they were nuts, but whatever. I asked Garrett about this, and while their new turbo can take 10 times the force of the journal bearings, but that doesn€™t mean you shouldn€™t use a BOV. Also they have as part of their warranty questions are they using a BOV or a functioning BOV.
Now a couple of situations come up when a BOV is not necessary. A race car that does 99% of its shifting with flat foot shifting. In this situation, the throttle never closes during shifting, so there is no need for a BOV. The other situation is low boost. Say up to 5 or so PSI, a BOV is not that necessary. At this point the 5psi of back pressure trying to stop the turbo (during shifts) isn€™t that bad for the turbo. And generally an engine/turbo running 5psi is pretty responsive so re-spool isn€™t a problem.
But you still want to use one in any Subaru application. They run too much boost, and if you want your turbo to last as long as possible us a BOV. While not running a BOV may be OK on a turbo, its not good for respool. That sound is the air backing up in the boost tube going through the turbo. At the same time, your turbo is either stopping or really really slowing down. Also this rush of air going backwards through the system will cause bad MAF readings and poor drivability at low speeds.
Using Crawford as an example may not be the best as all of their shop cars are race cars. They don€™t even need a throttle plate! But it is very interesting that they have gotten good life from their turbos.