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Discussion Starter · #1 · (Edited)
It's taken me a while to finally write this novel of a thread, but I hope it encourages discussion and it helps other 2.5L owners.

In February/March of this year, I came across some (what I felt) really good deals on a gently used Magnaflow exhaust and a never-used Eurojet header.

I’d owned my 6-speed automatic 2008 Rabbit for a little over three years and wanted to begin modifying it beyond aesthetics. (I didn't want to delve into turbocharging the car for a number of reasons.) But I wanted to “do it right,” so I read up on exhaust headers and eventually even went and had it ceramically coated (to encourage heat resistance) before installation.

In addition, I was going to get Unitronic’s Stage 2 software installed simultaneous to the exhaust and header. I thought that doing all three of these upgrades would make a respectable, but not enormous, difference in the power my car was creating. Since there hadn’t been too many other 2.5L owners that had done such modifications, I was going to document the transition though dyno’ing the car after each mod.

After all, Magnaflow posted a Dynojet graph declaring a “10HP & 10LB•TQ Gain!” from the exhaust on a 2007 Rabbit.
(Granted this was the year where the engine was rated at 150HP, not 170HP like 2008+ years.)


Eurojet was claiming “Dyno-proven HP gains,” on every retailer’s website, without any dyno graphs.
Unitronic suggests a “15HP & 13LB•TQ” gain, albeit also without any dyno graphs.

Now granted, Unitronic’s numbers are going to be at the engine, not the wheels, for horsepower and torque gains. Which is why, quite honestly, I’d be more inclined to believe Unitronic’s claimed numbers out of all three manufacturers, because they do the testing with just the engine outside of the car. As we all (hopefully) know, there is approximately a 15% drivetrain loss, so let’s assume for the sake of argument that Unitronic’s software actually puts out around 12HP and 10LB•TQ. If you’ve been paying attention, the hyperlink above was to Unitronic’s Stage 1+ software, not Stage 2 - I’ll get back to that in a few paragraphs.

I brought my car to Mobile One in late April of this year. Aforementioned, I wanted to “document” the progression from stock to modified by dyno’ing the car after each installation. Mobile One has a Dyno Dynamics dynamometer, which have been known to be brutally honest about the power your car is delivering to the wheels. I don’t care to argue about Dyno Dynamics VS. Mustang Dyno VS. Dynojet.

The first dyno graph revealed almost exactly what I was expecting - about a 15% loss in the horsepower and torque figures that Volkswagen suggested for that year - 170HP & 177LB•TQ x 15% (loss) ≈ 144HP & 150LB•TQ:


The shop then installed the header and exhaust, and dyno’d the car a second time. The posted dyno results from Magnaflow of 10HP & 10LB•TQ from their exhaust - in addition to Eurojet’s claim of “Dyno-proven HP gains,” I was expecting a result of maybe 15HP & 15LB•TQ. Two runs in, the results show a gain of almost 14HP and 5LB•TQ:


After searching the databases and eventually calling Unitronic, Mobile One couldn’t find the Stage 2 software for my Rabbit’s engine/transmission combination, so they flashed my ECU with Stage 1+. The owner of the shop (Jason) even called Unitronic’s headquarters to escalate the problem and explained that he’d notify me once Unitronic notified him of the release of Stage 2 for my drivetrain combination. He also mentioned to them that I had a Eurojet header and a Magnaflow exhaust installed, so maybe they could further tune it for me. After Stage 1+ was flashed, the shop dyno’d the car a third time, but the results were interesting. To our surprise, we saw a decrease of about 6HP when this software was installed:


Mobile One kept in contact with both Unitronic and myself on the status of my Stage 2 file until July. After nearly five months of testing, Unitronic adamantly concluded that the Eurojet header that I have installed, actually lost power when tested by them on their engine dyno with my specific engine/exhaust/header combination. The shop and myself were surprised, and not quite sure how it's possible. Obviously they are not going to spend any time making a file for a piece of hardware that produces negative results.

I plan to remove the Eurojet header and replace it with the stock header, then dyno the car again to see the results.
It’ll be interesting to see what the outcome is.

If something positive has come out of all the work that’s been done thus far is how gnarly and unique my exhaust note is.
Really laying into the throttle brings a smile to my face. My girlfriend has a 2010 Jetta with the same engine/transmission combination and in comparison, the Rabbit is undoubtedly quicker. It's difficult to describe, but the car pulls away smoother and it's a lot more fun to drive.


I went into this blindly, not knowing what to expect. If there's one thing I've learned, it's to patiently wait for the proven numbers by a manufacturer. A lot of us 2.5L owners are holding on to our money, waiting for new and improved performance parts to arrive. Keep waiting, there's a lot of stuff on the horizon and I have a feeling 2012 will be a good year for us.

I'd still recommend Unitronic software and the Magnaflow exhaust to any 2.5L owner. Unitronic put in the hard work behind the scenes to finally reach an (unexpected) outcome. I also highly recommend Jason and the team at Mobile One in Glenview, IL.

I plan to continue updating this post.
In a way, it’s my build thread.

PERFORMANCE MODIFICATIONS (as of 12/6/11)
•Eurojet Stainless Steel Exhaust Header
•Magnaflow Stainless Steel Cat-Back Exhaust
•Unitronic Stage 1+ Software

Added 8/6/12
•Black Forest Industries Stage 2 Transmission Mount
•Black Forest Industries Stage 2 Torque Arm Insert
 

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Interesting the the headers caused that issue.
my thoughts exactly.. i mean some low end torque loss would be expected but an overall loss of power doesnt make sense.


@ OP either way good to see others are still interested in the 2.5l. good luck with build
 

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my guess is that the stock airbox is limiting the amount of air in while the full exhaust is allowing too much out.

I'm sure an intake will solve this problem and an SRI will make it perfect.

edit: This is with the assumption that you do not have an intake already
 

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Exactly what I was thinking. the amount of back pressure needed is something that can be debated, but if you dont have more air passing through the engine, you really don't need the exhaust headers.

It's good that he has those though, it's almost all down hill from there. :thumbup:
 

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This is very interesting to see. I'd like to know if there would be a difference with moving to a stage 2 file. OP you should post up a comprehensive list of all mods you have that will affect the dyno.

Sent from my BlackBerry 9700 using Tapatalk
 

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OP you should post up a comprehensive list of all mods you have that will affect the dyno.

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2nd this
 

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yo broski are u in chicago? I went to mobile one too and got a dyno on my 2010 golf. 163whp, 156ft tq with intake and 2.25 catback with crush bends.
 

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Like the others said, you should put a cold air intake like bsh or carbonio or short ram like neuspeed and dyno again before getting rid of the headers.

The biggest bottle neck on this engine is the airbox. just putting an air intake yields some good results.

give it a go, you might be surprised with the results.

edit: if you already have an intake then I have no clue...
 

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Discussion Starter · #14 ·
DerekH said:
I would say even just a cold air intake would help out a lot.
pennsydubbin said:
I'm sure an intake will solve this problem and an SRI will make it perfect. My guess is that the stock airbox is limiting the amount of air in while the full exhaust is allowing too much out.
thygreyt said:
I would assume he as an intake...
I think you're all right - an intake would help the situation but I don't have one on my Rabbit.
I did pre-order the BSH intake when it was first released; soon after it arrived and I read the installation instructions about cutting the wiring loom to re-route the MAF sensor, I decided against it. I've heard that they've re-done the installation procedure, but that kind of worried me.

I do have my eye set on the Neuspeed P-Flo intake, and I plan on installing in addition to an intake manifold once they become more widely available for the 2.5L.


lessthanalex said:
I'd like to know if there would be a difference with moving to a stage 2 file. OP you should post up a comprehensive list of all mods you have that will affect the dyno.
I have update the original post with the list of "performance" modifications currently on the car, which really are the three that I talked about in the original thread.
 

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^ like said above, you just carefully cut through the tape and separate the wires of the MAF sensor from the other wires, tape them back up and have the wires that go to the MAF on the right side of the battery coming to the front rather than behind, if u wanna see how i did it just pm me and ill send u a pic....there really wasnt anything difficult to do in the installation.
 

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^ it's not difficult, you just need a small pair of finger nail scissors to cut the tape wrapped around the wiring harness. nail scissors were the best recommendation given to me, as they are very sharp, and very small so that you don't accidentally slice anything on accident! :laugh:
 

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I'm planning to get C2's SRI Installed at the end of the month as well as a Eurojet Header and Eurojet High Flow Catalytic Converter.

Currently have a Neuspeed Intake and Techtonics Dual Borla Exhaust so I'm curious as to what my car will put down in the end, especially after reading this thread. Unforunately, I'm not sure when I'll ever get the car dyno'ed but I'm still looking forward to the finished product nonetheless.
 
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