Need some tuning advice - Subaru WRX Forum
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post #1 of 9 Old 05-22-2017, 01:41 PM Thread Starter
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Need some tuning advice

Hello all,

I bought a 2002 wrx for my son and we have been building it for about a year now. we wanted to boost it some more because faster is always better right. so we just put in a FP71HTA turbo DW 300 fuel pump, and DW 1000cc injectors and had it tuned. it is running great but were just not feeling much of an increase over the VF30 that the car had on when we bought it. The VF30 was running 21-22 lbs of boost but would taper in the upper RPM's like they tend to do. Now the tune it has now is running 20 PSI all the way to redline, and we are only using 69% of the injectors. Our tuner tells me that this is as far as we can take it running 93 pump gas.

So the question is how do I read about all these people running 23-25lbs of boost on pump gas? Is the higher boost safe or not? And finally if it is not safe to boost higher, what is my best option to get us up there safely (meth injection)?

Mods=
JDM 207 block
CP pistons
Arp studs
Grimm speed balancer
Cobb 3 port boost controller
Tomei EL headers
TurboX BOV,Intake, FMIC
4.44 trans/Diff
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post #2 of 9 Old 05-22-2017, 02:35 PM
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Always remember that power is a function of not only boost but also fuel and timing. It's a balance of the three.

So yes, you can go up much higher PSI, but to be able to run such a hot charge without knock you would have to tone down the timing a few degrees which is a significant drop in power. So even though someone is running 23psi on a VF39 (I use this as a personal experience) doesn't mean they're putting in great numbers on the road. In my tuning experience (I specifically tinkered with these variables to see how far I could push my setup and how much power doing so would make.

In the end I settled for running the VF39 at around 19.5 psi with more aggressive timing. The car just runs better over all but also makes more power than it did at 23+ psi (I basically ran it unrestricted so it would peak to around 23psi and then taper off almost naturally toward red line).

There's another aspect to this too that has to do with timing. Certain tuners find it completely acceptable to crank up the timing and allow Fine Learning Knock values to appear (that's your ECU compensating for too aggressive of timing by pulling some in different areas of the map). Other tuners are more conservative. I am on the other side of the spectrum, I try to avoid ANY FLKC in my setup because I know what it's like to have to replace the motor and it's not a pleasant experience.

There's yet another aspect to this whole thing: How you perceive power. Your old map may very well have made more power at part throttle. Our cars like to create a lot of torque in this mid-range and I've made tunes where it felt like a slingshot and others where it's not as noticeable. The question is how does it work when wide open throttle? I bet it makes much more power but doesn't feel like it in other areas of the map? I bet that map can be tuned for more aggressive timing in the medium load areas and it would feel like a slingshot (and drink more fuel respectfully) in that area of the map.
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post #3 of 9 Old 05-22-2017, 03:07 PM Thread Starter
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Thank you Ruso, the comparisons were at WOT and we have a stock car for comparison. The car is a little bit faster and I am sure that is due to not loosing the boost at the higher RPM's but with this much bigger turbo, I really expected a bit more. We researched for a good long while before selecting the FP71HTA and chose it due to the good results people were getting. Unfortunately we live in the black hole of the Subaru world and I have no Dyno to take the thing to unless we take a weekend and go out of state for actual number to compare.

All my tuning experience has been on older cars and the supercharged 2.0 Ecotech. With the Ecotech as long as we had injector left and no Knock we just kept taking the boost up. We didn't have to play the timing game too much. So I just didn't understand why with only 69% injector utilization I couldn't add fuel and go up a lb at a time until we hit the first signs of knock and then fine tune? I asked the tuner, and he simply said 93 pump gas doesn't have enough octane for more??
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post #4 of 9 Old 05-22-2017, 03:50 PM
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What types of numbers did you put down on the dyno? (If you don't mind me asking).

octane is a rating for how much knock reduction the gas is capable of. But adding more fuel has the same result... reducing boost has the same result, decreasing timing also has the same result.

You can make more power by making the fuel a little leaner OR advancing timing a little OR increasing boost... but neither of the three will produce the same types of results on every car.

I've ran a VF39 at 23+ psi peak boost on 92 octane. Once again it ran, but it makes significantly more power at 19psi with more timing advance and a slightly leaner fuel ratio (I aim for around 11.5 numbers because I run an efficient Water to Air intercooler).

I'm no expert, I only tune my own car and if your tuner is an expert tuner who specifically has solid experience with a turbocharged/modified Subaru then my input is valid but may not apply to your case. If your tuner is NOT experienced in Subaru tuning and is just a general tuner, then I would question the numbers.
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post #5 of 9 Old 05-23-2017, 04:18 PM Thread Starter
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No dyno's in my state (MS) so I have no numbers on new setup. All tuning was done via e-tuning

My AFR is 11.25 and holds solid, my injector duty is 69% running 93 octane and my timing is 13 (4000 rpm) moving up to 19.5 and holding until redline.

It just seems to me that this is overly safe and I could still safely get more out of it by adding more fuel/boost?? I could send you my log and see what you think? I may have to do a road trip and find the closest AWD dyno to put it on, I know there are a few in Florida or maybe Tenn.
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post #6 of 9 Old 05-24-2017, 03:18 PM
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Quote:
Originally Posted by 458socom View Post
No dyno's in my state (MS) so I have no numbers on new setup. All tuning was done via e-tuning

My AFR is 11.25 and holds solid, my injector duty is 69% running 93 octane and my timing is 13 (4000 rpm) moving up to 19.5 and holding until redline.

It just seems to me that this is overly safe and I could still safely get more out of it by adding more fuel/boost?? I could send you my log and see what you think? I may have to do a road trip and find the closest AWD dyno to put it on, I know there are a few in Florida or maybe Tenn.
So if you're e-tuned, are you running a Tactrix cable? If so, if you want I could compare it to the maps I run on my setup side by side and send you screen shots / things I see.

A good email is: [email protected]

I'd also be down to check out some logs and/or poke around in your map after to see how your car reacts. You can always pop the old map back on.

By the way, that timing seems quite different than the numbers I came up with on my setup but I can't easily check right now (I"m at work).
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post #7 of 9 Old 05-25-2017, 10:10 AM Thread Starter
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map and log sent.
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post #8 of 9 Old 05-08-2019, 09:38 PM
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I have a very similar set up. Same turbo, same fuel pump, but only 750cc injectors. I just had a speed density tune on mine today. 300WHP and 267WTQ on a dynojet. My tuner said that's as high as I can go with the turbo on pump gas.

Other mods: built bottom end, grimmspeed TMIC, catless UP and DP, cold air intake.

What RPM are you fully spooling at?
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post #9 of 9 Old 05-08-2019, 09:39 PM
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Also, I was tuned at 20ish PSI
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