I can't explain it. It seems like it defies logic.

I installed a 3" Helix V2 downpipe, a Perrin 3" cat back, and then sent my ecu to Shiv with the instructions that I need a map for 93 octane and a full 3" turbo back exhaust for my Evo 9. (I actually didn't have the "full" exhaust yet... i.e. didn't have the cat delete yet) So, I got the reflased Vishnu Ecutek back in the mail... plugged it in and boy, what a difference. I loved the power bump, very good turbo hit.

Well, the thought of running my car with the stock 2.5" cat in place bugged me, especially since the ecu was tuned otherwise. I felt like it was a cork in the system. So, I bought the Ultimate Racing 3" test pipe and installed it expecting to experience the full potential of the ecu... i.e. like an extra 12-15 hp increase with a catless system vs the stock cat. After the install, I felt like the power wasn't exactly there. If anything it almost felt less powerful. It was a smoother power delivery with a louder note but, it just doesn't feel like I'm pushing more power or perhaps it feels like I lost some of the torque that I had before when the cat was in place.

What's going on? Anybody else felt this before? Am I going crazy?

 

my guess is your butt dyno was already calibrated with the flash for the time you had the cat, then when you took it off the 10hp diffence was hard to feel now your guessing. Call vishnu and ask if it was flashed for tbe or not.

 

I kinda get what your saying and agree that it defies logic but I swear that there must be a difference not in power but torque around the onset of boost. I do feel that the car doesnt rev as freely with a cat and the top end isnt quite as good. So I dont have the proof but what I think you are explaining and what I feel is an increase in torque not power and its near boost peak, though the actual HP is less especially in the top end

 

That's weird. Because I did everything almost exactly the same as you, except when I put the test pipe on, it made a world of difference. And now that the flash has been dyno tuned by shiv, it's even better.

So I'm not sure what to tell you, except that I did my reflash the same way and have had nothing but better than expected results!

 

So you got Shiv to do a custom dyno tune or did you ship your ecu in and get an off the shelf reflash? I got mine in the mail... not a dyno tune.

I wish that I could have had a custom tune done like I did with my suby but I couldn't fit it into my schedule this time. Oh well.

 

You lost some backup pressure then you lost some low end torq, thats normal.

However, your top end should be much improved. When I installed my test pipe on my 03 from a cat I lost some low end torq but had better spooling and better top end.

 

Reset your ECU? :B

 

This is the real reason here. Good post!

Torque curve is probably higher than hp curve at a particular rpm with a cat on it. Believe it or not, but *some* backpressure is good for the motor.

I just recently changed my high-flo cat out for a testpipe with the same results. The horsepower is probably now more equal to the torque at that rpm so you feel less of a difference, but more on top end.

In short, the testpipe made the area under the curve between the torque and horsepower smaller and so your butt dyno feels less "omph" at the onset of boost.

-M

 

Well that's what I was wondering. I asked about this on the general discussion forum but, I didn't get any response. I do this on my WRX every so often and I can feel a difference. So, does this work well with an Evo reflashed ecu like it does for a suby? Anyway, here is what Shiv posted over on NASIOC.

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Just a little trick that has been shown to accelerate the factory ECU's ignition timing learning process.

Background: There is something called "Ignition Advance Multiplier". It represents, by some complicated algorithm, the average learned positive knock correction applied to the ignition maps. It's represented in 1/8th degrees increments. 1 being the lowest and 16 being the highest (1/8 to 2 degrees in absolute terms).

The "happier" (knock free) the car is, the higher the number will be. Conversely, the lower it is, the more knock prone it is. This number, after ECU reset ore ECU swap defaults to 8 and usually creeps up to 16 (if well mapped) through normal driving. Depending on driving characteristics, this can happen within a few hours or a few weeks. Well, here's a way to make it happen in about 5 seconds ....

First: With the car fully warmed up, reset the ECU. This can be done by killing power the ECU or by simply pulling off the neg. battery terminal and pressing the brake pedal for a couple of seconds.

Second: Drive to a nice open road without traffic. Don't go on boost until you get there. Put the car into gear (3rd gear works the best) bring the revs up to 2600rpm. Push the go pedal down slightly so boost stays right around 2-4psi. You will need to MAINTAIN 2500rpm and 2-5psi for approx 5 seconds. You can do this by left-foot braking gently as to prevent acceleration. During these few seconds, the advance multiplier (which you can't see so you'll have to trust me) will go from 8, to 12 and then to 16. Works like a charm. And on our reflashed ECU, is worth an immediate 10-20 horsepower

In an attempt to save a lot of dyno time between reflashes (when the advance multiplier resets itself), I do this little trick after every reflash. In a typical dyno session, it's not unusual to reflash the same car up to 5 times. On the dyno, all I need to do is tell the dyno to hold revs to 2600rpm. Then I just lay on the throttle until I see a few psi of boost... Bingo!

Warning: This little trick artificially speeds up the learning process. This is only a good thing if the re-mapped ECU is mapped properly. If there are trouble-spots where knock is present, this trick will make it even more present. So be careful!

Cheers,
shiv
www.vishnutuning.com

 

I take it that we don't reset Evo ecu's judging from the lack of responses. I just seems weird that what works well on a subaru ecu won't work well on a mitsubishi ecu.

 

No you dont the EVO and subaru ECUs are very different.

 

Thanks. That explains it.