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Yea tough to say whether this was the exact same wrx, and whether it was sone on the same day, as temp and humidity have a bigger role than airflow characteristics of the two pipes. Majority of the added power is from getting rid of the precat.
 

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i wonder how the crucial racing systems uppipe fairs compared to the helix. Since it's thermal coated inside, the air should flow a tad bit smoother....
 

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Yea tough to say whether this was the exact same wrx, and whether it was sone on the same day, as temp and humidity have a bigger role than airflow characteristics of the two pipes. Majority of the added power is from getting rid of the precat.
No, this is not the same WRX, or the same day. These are dyno's I have had stored away for a long time non. I was looking through and noticed a comparison with mutliple Stage 1 Tunes. Many of the gutted uppipes seem to make less power up top versus a helix uppipe (more even flow, though still has a flex pipe). A would even say a non flex pipe (straight pipe) would work even better but installing the uppipe with no leaks takes a more skilled hand.

So my thoughts led me to believe that the gutted inside diameter has poor flow causing poor airflow.

A simple thought, when you change you stock axle back for a straight through, do you notice a difference? One flows well, one doesn't.

Any questions or other views please speak I am more than willing to discuss.

Cheers,
Bill Knose
Lead Tuner
I-Speed USA
 

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That is exactly what we use to sell, the JDM uppipes, exactly for the reasons given, stock looking, yet flows like most aftermarket pipes.
 

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Were the two cars running the same boost post 6,000rpm?

I know that you were using stock engine management, but I am surprised that there is that big a difference if there isn't a difference in the amount of boost.
 

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Discussion Starter #10
Rich10 said:
Were the two cars running the same boost post 6,000rpm?

I know that you were using stock engine management, but I am surprised that there is that big a difference if there isn't a difference in the amount of boost.
exactly! so the gutten stock approach vouched by many just ain't all that great flowing like they say it is.
 

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skywalker said:
So my thoughts led me to believe that the gutted inside diameter has poor flow causing poor airflow.
How is the inner diameter of the Helix up pipe different than the gutted stock up pipe?
 

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Discussion Starter #12
the helix inner diameter is around 1 7/8". the pipe inside has a rippled section for the flex. the outer braided cover has nothing to do with the flow. i saw pipes out there without the braided cover. you can see the rippled flex pipe. it's kinda ugly without the braided cover.
 

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Rich10 said:
Were the two cars running the same boost post 6,000rpm?

I know that you were using stock engine management, but I am surprised that there is that big a difference if there isn't a difference in the amount of boost.
No they were not. Though the way I tested it was with the same EcuTeK reflash map. The gutted uppipe boost was a little lower and less steady (moving up and down a little bit).

Were you thinking that maybe the lower boost caused the power loss. Makes sense, though why was there a power loss in the first place on the same map?

This could be from the tune, the gutted uppipe might need a better tune. Though from tuning numerous gutted uppipes, it sure seems like more power can be had with a smoother flow.

Cheers,
Bill Knose
Lead Tuner
I-Speed USA
 

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These results are in conflict with another test that was performed between a gutted stocker and an unnamed aftermarket uppipe on the same WRX, same day, etc. I believe they were within a fraction of a whp of each other. I'd agree that small differences in boost could account for most, if not all, of the discrepancy between the two aforementioned dyno graphs. Without proper controls and repetition, these data are pretty much meaningless.
 

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Integra96 said:
These results are in conflict with another test that was performed between a gutted stocker and an unnamed aftermarket uppipe on the same WRX, same day, etc. I believe they were within a fraction of a whp of each other. I'd agree that small differences in boost could account for most, if not all, of the discrepancy between the two aforementioned dyno graphs. Without proper controls and repetition, these data are pretty much meaningless.
I understand what you are saying about repetition and controls. Though what do you consider proper control and repitition or even proper testing? The dyno's plots I had were two different cars, and there are a few more in the past with, gutted uppipes, aftermarket uppipes, with similiar results as above. Yes they are over a period of a few different days, yes, different boost levels, (though same EcuTeK'd maps, and darn close temperatures. Boost could be the cause of it, though why would boost be down if the setups are identical, besides uppipes? Maybe the car? Might be...

As for another test, how can one say that the same car, on the same day was even accurate, dyno's can be off by up as much 3-5 hp per run, cars can relearn and adjust to different characteristics every time you drive them. Who is to say that was even an accurate comparison. Though the information was helpful, as it gave a closer look at gutted versus aftermarket.

The only way to really tell with true testing, is in a totally closed enviroment, with an ECU that does not learn. Where a test can be setup with the exact same tune. Though what is to say you should not or should be tuning both for optimal power. But what is optimal power, don't you need a tuner for that. How does that tuner even know what is optimal for that setup unless he has done it numerous times?

The information I offer to the public is is from experience, I have been tuning Subaru's for a few years and have noticed things through the years about different parts, some good, some not. I make my statements based on multiple hand-tuned cars over a period of time, not just one car. On the average have found the gutted uppipes do not work quite as well. Showing it on the dyno is probably the worst idea, as those really can be incredibly off.

Great Discussion and Great Points!
Bill Knose
Lead Tuner
I-Speed USA
 

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I'm not at all surprised by those results... the idea of a gutted up-pipe brings up visions of nasty turbulence to me. Now if you cut it open and welded a straight pipe in, then you're in business!

For reference, I have a JDM up-pipe. Paid $115 for it and got it from a local sandrail builder. Can't beat that for a high quality up-pipe! Another added benefit is the lack of an EGT probe that could break off and kill the turbo. Worth every penny!

PS. Hi Bill! :thumbup:
 

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skywalker said:
No they were not. Though the way I tested it was with the same EcuTeK reflash map. The gutted uppipe boost was a little lower and less steady (moving up and down a little bit).

Were you thinking that maybe the lower boost caused the power loss. Makes sense, though why was there a power loss in the first place on the same map?

This could be from the tune, the gutted uppipe might need a better tune. Though from tuning numerous gutted uppipes, it sure seems like more power can be had with a smoother flow.

Cheers,
Bill Knose
Lead Tuner
I-Speed USA
I'm not surprised that a constant diameter pipe has better flow characteristics than a decatted stocker with a bulge, but I am surprised that the difference is as large as shown in the graphs. I'm not saying that your results are wrong. I haven't done the test.

You wrote earlier that you have noticed this trend in other dyno plots. Is the hp difference usually this great?
 

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yea, i have no boost issues with my gutted OEM, its just as ugly as it was before, doesnt raise an eyebrow when in for warranty and with stage II software, my powerband is smooth from 1900 to 7k... 16.4 psi from 3400-6000 16.0 from 6k-7k ... no complaints all smiles
 

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Me thinks a gutted oem pipe would flow a little less optimaly than a well designed smooth as silk uppipe- I don't think anyone would argue that point. What is open to deabte is to what degree these flow characteristics would influence power- my guess would have to be not very much.

12 whp- that's probably what a uppipe is worth in totality. A gutted uppipe probably slightly below that.

Guys that are gutting their uppipes aren't doing to wring every last bit of power out (otherwise they'd be forking $ out for a well designed aftermarket one)- instead they're getting very close to the same power, a proven non leaking design, stealth look and the price is damn good.

I'd be very suprised if there was more than a couple hp difference between the two. The aftermarket ones (including the STi/JDM ones) will flow better, that I'm pretty sure of. 12 whp more, only if they forgot to take the cat out of the decatted one.

Big Sky
 

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Rich10 said:
I'm not surprised that a constant diameter pipe has better flow characteristics than a decatted stocker with a bulge, but I am surprised that the difference is as large as shown in the graphs. I'm not saying that your results are wrong. I haven't done the test.

You wrote earlier that you have noticed this trend in other dyno plots. Is the hp difference usually this great?
No offense taken about the results. A lot has to do with how you explain the data you have and how other poeple interpret it, especially to poeple on a forum! Much different then standing up in front of 50 poeple in a small room. He he...

Good questions and no the difference is usually not this great. The plots represent the range of what can be expected on this particular setup so these are the outer limits. These happen to be the lowest ad highest hp made with various stage setups. Could there be higher or lower yes, though this is what I have seen with many tunes over the years.

Wow, I am surprised at the questions, they are actually good. Is everyone feeling ok? ;) Keep them going!

Cheers,
Bill Knose
Lead Tuner
I-Speed USA
 
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