Once the turbo, clutch and injectors were installed in Project Evo X, Mike Welch of Road Race Engineering got to work on the dyno.
Let it be known right now that to make real power on 91 octane, regardless of the hardware involved, is a royal pain the rear. Mike had his work cut out for him before he even began.
Oh, and Mike raised the crazy up one more level. He filled our tank with 91 octane from 7-11. It's madness, yet there is method to it--if he can make our car knock-free on this utter crap fuel, then it'll be safe on any fuel we'll ever fill the tank with.
On to the tuning, then. First he scaled the bigger ID1000 injectors in the ECU and roughed in a conservative calibration. From there he gradually tuned the car, adjusting those scaling parameters, changing intake and exhaust cam timing, boost pressure and ignition timing.
During and between runs Mike monitors more than just output. There's knock activity, fuel trims, air-fuel ratio, coolant temperature, intake temperature, intercooler effectiveness... you could say that a tuner's job is like juggling cats next to a running chainsaw. If one cat gets away from you...
...ask him to switch off the chainsaw.
Eventually, the car stopped making power and started becoming knock-sensitive. That's usually the point where you're done and need to back off a bit to have a safe calibration.
The problem is that at this point, it just wasn't making much more power than it was with the stock turbo. Everything looked good otherwise (and we have a nice closed-loop idle with the ID1000s; no nonlinearities, and a relaxed 62% duty cycle at redline).
As for the power situation, long story short, our car still had the stock exhaust elbow and downpipe. And that was a problem.
This elbow is that part of the exhaust that connects the turbo's turbine discharge to the cat. Stock, it's a restrictive little thing. One theory is that Mitsubishi engineers had to make the elbow all kinked up to accomodate right hand-drive cars. Basically, to keep it away from the steering shaft that pokes down in that same region.
Whatever, the operating theory is that the stock downpipe was very likely choking off flow and introducing backpressure. To address this, AMS sent us a higher-flowing replacement they call a Widemouth Downpipe. It's an apt name. Comparison between the AMS Widemouth and stock piece can be seen below. You could drop a baseball in one end and of the Widemouth it would drop out the other.
It beautifully made, too, comprising cast stainless segments with a generously-sized flex section to replace the stock spring/bolt arrangement.
Back on the dyno with the new downpipe--RRE mentioned that installing the Widemouth was a bit tricky due to the physically larger GT30R--Mike noticed an immediate benefit. The car was now less detonation-prone, so he was able to better exploit the higher-flowing nature of the GT30R. From about 4200 rpm to redline, the Widemouth allowed him to tune in an additional 25 hp... and that's with running a bit less boost in the midrange, too.
So the lesson here is that matching components is critical when we're talking about the kind of output this 2.0-liter engine is making while being fed The Worst Fuel On Earth.
This post is getting long-winded so I'll post up a dyno chart of its final state of tune in a followup blog entry.
Jason Kavanagh, Engineering Editor @ 25,000 miles.
subytrojan says:
06:35 PM, 09/16/09
I should've put Arco 91 octane in my car (2004 WRX - EJ205) before I got it tuned in January 2008. I think I hear an occasional ping at WOT at times. :(
dragonzsoul says:
06:56 PM, 09/16/09
Ah! what a tease!! i want more information!!
church123 says:
07:31 PM, 09/16/09
+1 on the need for a better downpipe. We've been running a shorty downpipe and race cat (downpipe retains the stock O2 housing) on an EvoX with an FPRed.
Versus the stock turbo spoolup was a bit later 300-500 rpm, but the midrange hit harder with less boost. But we couldn't get much more peak power than with the stock turbo - more boost simply did nothing - same problem you had. Going to a test pipe freed up another 20 hp, but we're still stuck at about 360 whp from 5000-7500 rpm (stock cams). So, we've just ordered a divorced full downpipe setup from Ultimate Racing (separates the flow from wastegate and turbo outlet). Hopefully that will let us get closer to our 400 whp goal on stock cams on CA pisswater :)
Since you've already mentioned 25 hp gains I'm assuming you guys have already broken the 400 whp mark on the Dynapack. Should be a real blast to drive now. from 5000 to 8000 rpm should be epic.
subaru123 says:
07:39 PM, 09/16/09
Why does California only have 91 octane gas? Here in NJ we get 93 as premium. Only one station (Sunoco) has 87,89,91, and 93. Oddly our WaWa staions have 92 octane as premium. Does anywhere else use 92??
*For those of you who do not know, WaWa is the east coast version of 7-11.
http://www.navenewell.com/images/WAWA.jpg
http://en.wikipedia.org/wiki/Wawa_(convenience_store)
nealibob says:
07:52 PM, 09/16/09
Is one brand of gas really better than another? Is there any actual scientific evidence? Or are you just complaining about your dismal octane options? The only good thing about living in Chicago, from a driver's point of view, is the bountiful 93. I guess I will have to do some research.
oftech says:
08:07 PM, 09/16/09
http://www.toptiergas.com/
DCuerpoJr says:
08:18 PM, 09/16/09
Here in Seattle we have 92 Octane.
fuhteng says:
08:32 PM, 09/16/09
Only 91 in Kansas, and not much E85 either. I saw tons of E85 in MN when I was there for a summer.
spdracerut says:
09:02 PM, 09/16/09
Yes, gas brand DOES make a difference! With the previous generation evo, there's great freeware for datalogging the car and recording knock count. It has been proven time and again, 'cheap' gas is much more detonation prone compared to a top tier gas (Shell, BP, etc) of the same octane rating.
hybris says:
09:05 PM, 09/16/09
I'm guessing that at this point you guys can't have alternate tune for running on 7-11 87 octane?
church123 says:
09:21 PM, 09/16/09
Out here in CA I've had the best results with Mobil and Chevron gas. For some reason Unocal/76 seems more det prone, especially on boosted cars. Back when stations had a choice of adding MTBE or ethanol as an oxygenate I had better results with MTBE stations. So short answer, yes there is a difference.
As for why 91, the entire west coast distribution pipeline converted from 92 to 91 a number of years ago. The rationale was that with limited refinery capacity, they could produce more 91 than 92. Poor choice IMO, shouldve added more refineries
yellowbal says:
09:44 PM, 09/16/09
We have 92 octane in Oregon.
tryan says:
03:11 AM, 09/17/09
Anyone know the supplier for 7-11's gas stations and what other brands that supplier distributes to?
foxgtr says:
05:26 AM, 09/17/09
See, that's where I love the east coast, over the west coast. The Sunoco station we have here offers 87, 89, 93, 100, and 110 (110 is leaded). It's all at the pumps.
nealibob says:
06:35 AM, 09/17/09
I should mention that you can send it to me any time you want it tested on good fuel. :)
audisport says:
07:12 AM, 09/17/09
Makes me glad that 93 octane is the norm in Michigan. The ghetto no-name gas stations have 92 and Sunoco has 94. I was in Ontario, Canada (eh) and I was sad to see only 92, so I had to change my APR program to 91 octane. Couldnt really tell the difference but annoying none the less.
Oh yeah, and please post MUCH more info about the EVO.
oldchap says:
09:44 AM, 09/17/09
As an oil refiner, let me assure that unless a particular fuel station has some source contract with a fuel refinery, all stations in the area draw from the same fuel terminals. Usually these terminals are supplied by pipelines that draw from multiple refiners, so there is essentially no reliable difference between the base fuels of the same octane. But, each different fuel station will add proprietary additives and detergents to the fuel as they load their tanker trucks at the terminals. If a particular brand is using junky additives, there's no reason to fear other-branded fuel stations in the area.
estreka says:
10:01 AM, 09/17/09
The closer you get to Texas, the more 93 octane you're gonna see. Most of the South has 93, as do many breadbasket states.
"...91 octane from 7-11..."
I know "all gas is the same" no matter where you buy it, but I do agree that the quality of gas differs from place to place, particularly when we're talking additives.
cwmoo740 says:
10:23 AM, 09/17/09
I've seen one station just about 30 minutes south of SF that offers 91 and 99. Other than that, you're out of luck in the bay area unless you want to pay ridiculous money for 116 octane at Sears point.
misterfusion says:
10:44 AM, 09/17/09
Don't forget that there are some gas stations in Southern California that sell racing fuel. The Unocal 76 near my work (Citrus Ave in West Covina) has a 100 octane pump. It'll cost you, but at least it's available out there.
This website has a pretty good list (despite looking like a Geocities page from 1996):
http://www.davebarton.com/Unleaded_Racing_Fuel_in_SoCal
relyt says:
10:58 AM, 09/17/09
In Utah and other mountain states, "regular" is only 85 octane. At some stations, "premium" gas is on 89. Something to do with the elevation I'm told...
wayno_san says:
11:54 AM, 09/17/09
Quit your blabberings about the gas quality in your areas and start writing about THE CAR.
firstwagon says:
11:59 AM, 09/17/09
As I have never heard of a "7-11" refinery, I think it's safe to say their gas is the same as someone elses.
I do wonder who though.
kevinlch says:
03:13 PM, 09/17/09
To find race fuel in CA:
http://www.sunocoinc.com/site/Consumer/RaceFuels/260GT100Locations/