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Old 02-16-2011, 05:22 PM   #3
Scooby Specialist
Member#: 74110
Join Date: Nov 2004
Location: PERRIN Performance

I know, its been a while since i posted, but there was tons to compile and just not enough time in the day to complete this. Anyway here you go! I will repsond to some of the customer posts in just a few!

The Build and the Results

Installing the EFR, or should i say building a turbo kit surrounding this turbo wasn't too hard, it just took some time and planning. I spent alot of time placing the turbo in an area that balanced clearing everything, while still providing a decent intake path and downpipe path. At the time i didn't have the larger EFR8374 or something representing the size of it. On BW's website there were no dimensions that showed the overall size of the bigger turbos, so i resulted to figuring out the scale of the pics in relationship to the part i had. Hoping that the larger turbos would still fit with my initial design, i finished up the upppipe and downpipe and started the install. Below is a pic showing it all mounted up.

As many of you know I had had somewhat of a wasted dyno session/weekend dealing with the medium pressure actuator for the EFR. Essentially what it comes down to is our Subarus run high enough exhaust backpressure that some autowastegating occurs. This is when the exhaust pressure is pushing open the wastegate door not the wastegate actuator. While BW says the Medium canister cracks at various pressures, in my testing I found these don't pertain to actual boost pressures found. Meaning, BW says the Medium canister with 10mm of preload (plus the 2mm added at the factory) will crack open at 14psi of pressure. I found to actually crack open around 12psi and on the car ran about 11psi of boost. Even though I found contradicting info there is no need to go over my wasted efforts in trying to make this Medium Canister work.

So while the Medium Canisters the OE wastgates for these turbos, for our car, you need the high pressure one which is rated 17psi to 32psi. I have now been able to do a bunch more testing on these and I found 32 is not hard to hit! Yes, the simple solution is the BW high pressure wastegate canister. A more complicated answer is using a push/pull setup like this PERRIN prototype we built a few years back.

Amongst all my troubles with the High Pressure Wastegate Actuator, Full-Race sent me an EFR9180 to test out. This thing is freaking huge! I only had it for a couple of days and didn't get to dyno it as they needed it back, only to ship me an EFR8374! But anyway I will eventually toss this on to see how the spool characteristics are. I know it will make huge power with the right boost, but when will it reach 20psi, that is the question. And yes it did fit! Luckily i made a second uppipe and left it installed on our 2011 STI so i could just drop this into place. Sure enough there was tons of room!

More details will follow on our prototype kit and its design over the next few months, but there are a couple of really cool tricks and things that i think will make customers really like the install of this, IF we make kits surrounding the EFR.

Before I made time to dyno my car with the new actuator, I did some road testing and while this isn't an exact test, it does show how much more responsive the EFR is compared to the Garrett GTX. IF you look at this 2 second window comparing the GTX3076R w/.82 to the EFR7670 w/83, both reached the same boost level at the same time, but the EFR was floored about .5seconds later and about 200-300RPM later. This is a great example of the light weight CHRA coming into play.

In this diagram the Green line is a run on the GTX, and the red line is the one done on the EFR. You can see the sharp vertical line that represents throttle position. You can see how the EFR was floored later.

I did some other road comparisons and I was getting excited to see how this performed on the dyno. On the road, with the new high pressure actuator installed, I was noticing that the EFR was much snappier feeling. Cruising at 3000, I would floor it and it really felt alive as the boost started building. This is different compared to the GT or GTX3076 turbo, which turbos have much less response off throttle, and also at those lower RPM full throttle areas where the turbo is building boost. But when they come on boost, they hit pretty hard which makes them feel fast.

If a turbo feels fast that doesn't mean its really that fast right??

That is one of those things that is hard to describe to customers when talking about turbos. I hear customers say they were in their friends GT35 powered car and it felt so fast. It was because of that huge lag then huge hit of power. This makes cars feel faster than they really are. The reason why I mention that is the EFR actually doesn't have that huge hit power on the road like the GT turbos, especially the GT35.

Its like saying a Z06 Corvette feels slow compared to Rotated turbo kit STI. I have driven them back to back and the Vette with the flat TQ and linear HP curve actually feels slower, until you look at the speedo! This is the same with the EFR. On full throttle 2-4th gear runs, it doesn't have that huge hit of power, but when you look at the speedo you realize it's time to hit the brakes all of a sudden.

So, that is how I "Feel" about the EFR7670 with high pressure canister so far, not knowing how the EFR spools on the dyno. Until this point I had only dynoed the EFR7670 w/.83 with the medium canister and found it was slower spooling than the GTX3076R w/.82 housing by about 400RPM.

Hot Headers and Cold Headers

Below is a graph showing hot and cold runs. This is an important thing to understand because hot headers versus cold headers, makes a huge difference when the turbo spools up. The EFR7670 is the red and yellow lines from one set of runs at 25psi, and the green and blue are a set from the GTX3076. I consider the cold runs to be typical tuning runs where a run is made, a few things may be adjusted, and 30 seconds to 1 minute later another run is done. During this time, the header cools off as well as the turbine housing. A hot run I consider when a second run is done 10seconds or so after a run. During this time the header is still plenty hot as well as the turbine housing. The reason why it spools the turbo faster is that less of the exhaust energy/heat gets sucked out of cold headers which slows down exhaust velocity. When they are already hot, that energy/heat stays in the tubing and the exhaust velocity stays the same. The header on this car is not wrapped but wrapping would help this out between runs. This is also the same un wrapped header as used on the GT/GTX test so it a valid test as far as that goes.

If we use the 20psi mark, you can see that the EFR7670 with cool header crosses that point at just past 4000. But when hot, the change is pretty significant and decreases the spool point just past 3750. That is a 250RPM increase. The GT or GTX when cold was hitting 20psi at 3750,and when hot it would only decrease this RPM about 125 RPM. Either way all runs shown from here on out are done with the GTX or GT turbos with a cool header as well as the EFR with a cool header. All these runs
Before we start with the dynos let talk about the car, the dyno and all that stuff. I am sure many have see our GTX vs GT testing we did and while that info is still the same I know, not all of you, know about the car or dyno. So here we go.

The Car and The Setup

My 08 STI was used for these tests and its setup like a typical PERRIN GT rotated turbo kit car would be.

Parts installed: PERRIN Headers, PERRIN EFR Turbo kit, PERRIN FMIC, PERRIN Catback, and our PWI-2 Methanol Injection kit, PERRIN EBCS Pro, Deatchwerks 850cc injectors and Walbro 255lph pump. The engine is built with Cosworth Rods, Pistons and bearings, and ARP Studs. Things to take special notes on are: Stock heads, Stock Cams, OEM head gaskets, OEM TGV housings in place and functioning and stock fuel rails with PERRIN Stumble fix installed.

We use 92 ocatane fuel here in Oregon, but like any big power car running on pump gas, we run 50/50 methanol. The kit is setup to flow around 800cc's per minute. But can go up to 1200cc's.

Tuning duties are controlled by a Cosworth ECPro standalone ECU. An Innovate Wide Band, and EGT is integrated into the ECU as well as into the dash so i can visually watch AFR along with logging it.

The Dyno

Setup: Dyno we are using is our awesome Dynapack Dyno. Car is setup to run in 4th gear, starting at 2000 RPM and ending at 6900RPM. We use a settle time of 4 seconds, which means, the dyno holds the RPMS at 2000RPM for 4 seconds before the run starts. During these 4 seconds, we have the car at 100% throttle for about 2-3 seconds. The fans we use are not super crazy fans that flow 100MPH wind, but each fan flows exactly 28MPH (measured with our anemometer) and both are aimed at (not on) the intercooler). This doesn't provide perfect airflow to the intercooler compared to driving on the street, but it does provide very accurate and repeatable results and if anything lower HP that you may see on the road. Since the dyno has a pretty heavy load, it does provide pretty much the ultimate RPM for which a turbo will spool. So in these tests you will see ZERO benefit from the Titanium Aluminide Turbine wheel. Also all dyno readings are in Wheel HP not flywheel. Stock STI's make about 230-240WHP on our dyno as a reference.

All runs were done with the ECU reading about 30C intake temps, and this was very consistent. The dyno temp measured 60-65F. The dyno runs were done with about the same amount of time between them as well as coolant temps were always at 90C. The idea is we did it consistently to eliminate as many variables as possible. These same exact things were done with the GTX and GT tests a few weeks back and of course we did it on the EFR to ensure that the results were the same.


Regarding the tuning. Like the other GT/GTX tests, I tried not to do any tuning beyond AFR. I of course tuned for boost to be able to match the same 1.2 bar, 1.5bar, 1.7bar and 1.9bar runs I did with the GTX test. For sure the AFR needed tuning between these turbos and in fact I found that I needed to add fuel compared to previous runs. But I started with the same ignition timing as used on the other tests. The idea is to ensure that no unfair tuning was done to increase HP or TQ beyond a normal level. Keep in mind the whole idea here is that these are tests for PERRIN to determine if the EFR turbo is something we are interested in making kits for. There is no reason for us to fudge results, or make one turbo look better than the other.

Engine Demand

On last thing to hit on is, engine demand. Using engine airflow calculators, or the Borg Warner Matchbot program, you can see what your engine requires for air flow for a given boost level and redline. The next thing to look at is if a turbo fits these demands and if it does it efficiently. If you compare this against some of the popular turbo upgrades you will see that in most cases customers are running off the compressor map but getting great power. So its not always 100% important that your engine airflow needs fit within the boundary of the turbos compressor map. Far too often I get calls from customers that look way to deep into this and try to match their power goals to perfectly on the compressor map.

EFR7670 vs GT3076R

This is the turbo that BW said it compared to the most, but should make more power. After the first few pulls I noticed that I was getting a bit more engine noise that previously. I ended up pulling timing around the 5500-6000 range to keep some of the noise down. In the end this didn't change power at all. First let's compare the GT3076R w/.82 housing. In this test you can see the EFR is slower spooling on the dyno. Keep in mind these are cool runs and hot runs were faster spooling as well as heavy load on the road showed better performance, but none the less its consistent.

The green line shows the GT3076r w/.82 housing making more TQ at 4000 because it was making more boost there., but as soon as the EFR and the GT cross the same boost path the more efficient compressor wheel starts to kick in. Even at 1.7 bar of boost the EFR was showing a pretty solid 20WHP gain over the GT. In this case it's easy to see that the slightly laggier nature of the EFR was worth the trade off in HP. The "Area Under the Curve" the EFR has, outweighs the GT easily. I feel this is the best boost (1.7bar/25psi) to test all these turbos at because this is a very common boost run on Subaru's. Of course you see more, but when it comes down to boost being used on the street, 25psi or less is pretty common.

Now on to the comparison of the 1.9 bar runs. Even at 1.7bar, the GT3076R is running out of in relationship to the compressor map, but at 1.9 it really starts to. I remember in previous dyno runs with the GT, I had to pull timing out to ensure it was ok. With the EFR, it was way happier. As you can see, its making 20-30 more WHP at the same boost. There is only one thing with the GT3076 run, it's that it was on the hotter side of things and it was spooling faster than the other. For some reason when I did the 1.9bar GT runs, I spent the first few runs dialing in boost and this purple line ended up being on the hotter side of things. Either way you get the idea on HP gained, and from the other results you will get and idea on the spool.

I did do the other 1.2 bar and 1.5 bar runs but no need to show you the same basic gains of about 20WHP.
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Last edited by PERRINJeff; 10-24-2013 at 12:48 PM.
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