# ::: New Product::: Forge Motorsport 2.5T FSI High Volume Bypass Valve Elbow



## Forge US (Jul 31, 2002)

We are proud to announce the final release of an all new product for the 2.5T 5-cylinder FSI application found in the Audi TT-RS and RS3!

http://www.forgemotorsport.com/content.asp?inc=product&cat=&product=FMARSDV










Through extensive testing on numerous customer vehicles, we have found that the cast aluminium OEM bypass valve elbow, placed right in front of the throttle body, with it's very small discharge port size, is not capable of adequately discharging residual charge pressure at throttle lift. 

This issue is made significantly worse on vehicles that are tuned to produce higher than stock levels of boost pressure, especially vehicles with modified OEM turbos or even larger turbos.

The OEM discharge port size is far to small to effectively vent enough pressure when the throttle closes. In many cases, the ECU, through monitoring the pressure in the charge piping via the MAP sensor, will detect that too much pressure remains in the charge piping, and it will result in a fault code, but more severely, a potential reversion of pressure into the compressor of the turbo, potentially creating compressor surge, and slowing boost response upon reapplication of the throttle.

A video of the kit functioning can be seen here:






There is no easy way to modify the OEM elbow to increase its flow capacity, so we created an all new cast aluminium piece with a larger opening more than double the size of the OEM port, to handle a much larger volume of pressure discharge eliminating the potential for any problems.

The kit is also supplied with an all new Forge high capcity, aluminium piston-based, mechanical valve specially designed for this application, and a supplementary electronic solenoid that seamlessly interfaces with the OEM electronics to allow the ECU to continue to control our new replacement valve. 

Additionally, because the 2.5T FSI engine does not use a MAF sensor, and the engine management is based purely on MAP sensor readings, the option exists to use a fully atmospheric blow-off valve if desired without any adverse effects on the performance of the engine. The ECU is not monitoring airflow volume, so venting charge pressure to the atmosphere is not monitored and will not negatively impact the tuning at all.

The kit includes all of the components necessary to assemble the valve in either a fully recirculating configuration to maintain quiet operation like the OEM valve, as well as the components to assemble the valve as a fully atmospheric blow-off valve to achieve the oft desired sound. When setup to the atmospheric configuration, a plug is included to close off the intake recirculation port.

The elbow is cast in the UK, and the finish machining is performed entirely in house on our own MAZAK CNC machine centers. The valve, wiring harness, and all other accessory parts are also made and assembled in the UK, and the solenoid is purchased directly from OEM supplier Pierburg in Germany. 

The elbow retains the OEM MAP sensor bung, and all hardware necessary for installation is included. The valve is positioned and can remain hidden underneath the OEM engine cover if you so choose, and is compatible with the OEM intake/airbox assembly, and any other intake system that retains the OEM recirculation provision.


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## 311-in-337 (Feb 19, 2003)

canuckttrs said:


> fast & furious mod?



Did u not read their post? :sly:


Great work guys. Any info on that intake setup as well?


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## JohnLZ7W (Nov 23, 2003)

Does this just move the restriction to the other side of the DV if you're not venting to atmosphere? Are there plans for an enlarged pre-turbo port as well?


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## Forge US (Jul 31, 2002)

311-in-337 said:


> Great work guys. Any info on that intake setup as well?


The intake is something we're still testing. Need more data before we can release any info! :thumbup:



JohnLZ7W said:


> Does this just move the restriction to the other side of the DV if you're not venting to atmosphere? Are there plans for an enlarged pre-turbo port as well?


The recirculation port that returns back to the intake remains at 25mm / 1" to maintain the broadest possible range of cross compatibility with the OEM intake system return hose, which is kept the same size in all other currently available intake systems as well, however, we do increase the internal bore / decrease the wall thickness as much as reasonably possible.

Because the intake system is under vacuum, however, when the valve does vent, the vacuum of the intake system will help to draw the discharged pressure through the recirculation port, so while it does technically still remain a slightly smaller size than the new larger valve inlet, it doesn't restrict flow to a degree that is detrimental. All of our testing has shown that increasing the inlet port size to the valve alone has alleviated the issue, but the atmospheric discharge port is slightly larger than the recirculation port, so if you want or don't mind the atmospheric valve sound, it's going to give you the maximum amount of flow. :thumbup:


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## Black BeauTTy (Jun 11, 2011)

What issue is this addressing? I've not heard anything reported.


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## LongviewTx (Dec 26, 1999)

Just get one already and let us know how u like it. Your wife will buy it for you for Christmas!!!


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## joneze93tsi (Aug 8, 2008)

Question:

Does that valve flange have dimensions that would lend to mounting of an alternate Venting valves if so desired?

I know in other scenes you can order pipes with "greddy, hks, or other" flanges.

Just asking for the inner ricer in us all...


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## Marty (Jul 14, 2000)

Black BeauTTy said:


> What issue is this addressing? I've not heard anything reported.


Since when does there need to be an issue for someone to make an aftermarket part that claims to be "better"?


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## lpriley32 (Jul 28, 2012)

If you read the write up on their site it says for engines pushing 450+ hp. So, obviously not needed on a stock car.


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## canuckttrs (Feb 5, 2012)

Not entirely. If you read this post they imply that the stock setup is also inadequate. :/


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## Black BeauTTy (Jun 11, 2011)

Marty said:


> Since when does there need to be an issue for someone to make an aftermarket part that claims to be "better"?


LOL! *clicks the 'Like' button*


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## tdi-bart (Feb 10, 2011)

in europe lots of people are going into limp mode with tunes, perhaps this can help those with lesser tunes or whatever the reason is


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## Forge US (Jul 31, 2002)

We have many customers in the UK and Europe with modified OEM turbos (_larger billet wheels, etc_) like those from Loba out of Germany, and some with larger turbos that are experiencing this issue. Obviously this issue presents primarily at higher boost levels and larger volumes of airflow.

Most owners would not experience the actual fault code or check engine light until these power levels, but there is still an inadequate volume of discharge even for a mildly to heavily tuned stock turbo application. 

Consider that the opening within the OEM elbow is sized exactly the same as that of a 2.0L FSI engine with a K03 turbo. The same size as the much smaller 1.8T engine with an even smaller K03 turbo. Such a small valve opening is barely sufficient for these engines tuned or even stock, so it quickly becomes a much tighter bottleneck on a 2.5L engine with a much larger turbo that flows significantly higher volumes of air.

There is no harm in increasing the airflow capacity of the valve in lieu of future modifications or simply from a reliability standpoint. This is not specifically a performance enhancing product, except that it maintains positive boost response at throttle lift on highly tuned vehicles that can otherwise suffer from insufficient airflow of the OEM part.

And the flange of this part has an opening and a bolt pattern that is proprietary to this valve. It will not accept other aftermarket valves, most of which are likely to flow less anyway. The HKS valve is a pull-type unit that will never flow nearly enough airflow for this application. In fact, it's trademark high pitched whistle is quintessentially a sign of inadequate flow.


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## Black BeauTTy (Jun 11, 2011)

Thank you for the excellent response and information.:thumbup:


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## joneze93tsi (Aug 8, 2008)

Forge US said:


> We have many customers in the UK and Europe with modified OEM turbos (_larger billet wheels, etc_) like those from Loba out of Germany, and some with larger turbos that are experiencing this issue. Obviously this issue presents primarily at higher boost levels and larger volumes of airflow.
> 
> Most owners would not experience the actual fault code or check engine light until these power levels, but there is still an inadequate volume of discharge even for a mildly to heavily tuned stock turbo application.
> 
> ...



Thanks!

Seems like most will wait until it becomes an issue before handing over $5xx for what equates to a vented valve for most people.

I'm sure some people overseas will be quite please though!


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## hightechrdn (Dec 9, 2011)

Great looking product. Very glad to see the level of aftermarket support increasing for the 2.5TFSI engines. A few questions for you:

If the kit is configured to vent to atmosphere, is the port just left open like that? I am a bit concerned that something (water) could get into the engine with it facing up without any cover. I understand air pressure is going to blow most things up, but I can still see something heavy like a bolt, rock, etc falling inside... 

A bit of topic, but you mention MAP vs MAF based engines and that venting to atmosphere can be harmful on MAF type setups, which make perfect sense. However, Forge sells vent to atmosphere adapters for the 2.0 TSI engines which are MAF based. I have one on my son's 11 GTI in fact. Is the vent to atmosphere setup really a good idea for the 2.0 TSI engines? 

Though it is a little on the Fast and Furious side if vented to atmosphere, I am definitely adding this kit to my TT-RS build plans. I may even try out the vented setup for a while ;-)


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## Forge US (Jul 31, 2002)

hightechrdn said:


> If the kit is configured to vent to atmosphere, is the port just left open like that? I am a bit concerned that something (water) could get into the engine with it facing up without any cover. I understand air pressure is going to blow most things up, but I can still see something heavy like a bolt, rock, etc falling inside...


When setup to be vented to atmosphere, because we maintain the electronic solenoid control from the ECU, the valve does not just stay open all of the time. There is constant pressure applied to the valve to keep it closed during idle, cruising, and load conditions, and vacuum is only applied to open the valve at a throttle lift condition or when the ECU otherwise sends the signal for the solenoid to open the valve. 

If you didn't want to keep the cover over the valve or were concerned about the intrusion of anything, the valve can be mounted reverse with the horn pointing down. 



hightechrdn said:


> A bit of topic, but you mention MAP vs MAF based engines and that venting to atmosphere can be harmful on MAF type setups, which make perfect sense. However, Forge sells vent to atmosphere adapters for the 2.0 TSI engines which are MAF based. I have one on my son's 11 GTI in fact. Is the vent to atmosphere setup really a good idea for the 2.0 TSI engines?


There exists no universal truths regarding the use of any given type of valve on a MAF based application, which is why we offer application specific valve products rather than a single type of valve that is adapted to numerous applications. 

Keeping things in the VW family, while some MAF applications like the older 1.8T from the MK4 and the 2.7T from the B5 S4 are very sensitive to the amount of air discharged from the use of an atmospheric valve, applications like the 2.0 FSI and TSI engines have a totally different ECU architecture and mapping that is not nearly as sensitive to the same function. 

While we do offer universal style valves that can be made to fit the 1.8T and 2.7T, we do not only not recommend it, but try to discourage it. It will not specifically result in any damage to the engine, however, it can sometimes result in a rich fuel condition that the ECU cannot compensate for. We do have a hybrid style valve that was specifically made for the 1.8T, however, and has a very small fixed percentage of atmospheric discharge that we specifically measured to the be maximum allowable amount before issues would result.

On the 2.0T engines, we spent a long time testing the use of an atmospheric valve setup like our spacer long before ever releasing it to the public back in 2006. We found that maintaining the electronic control of the valve was more critical because the ECU was looking for the pressure to be discharged in a particular way, at a specific time and for a specific duration, but that it was not sensitive to whether the air was recirculated or vented to the atmosphere. We found no changes to the fuel trims, A/F ratio, ignition timing, nor any other engine function from the use of the spacer. We even dyno tested it, and found there to be no adverse affects on engine performance in any way. 

Various types of bypass valves for tons of applications are one of our core product lines, which we take very seriously. We have expanded our offerings over the last 15 years to nearly 70 different universal and application specific valve products. All of our products are thoroughly tested before release and come with a lifetime warranty, so you can be assured of optimal performance and support from us in the event of any issue for the life of the product.


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## hightechrdn (Dec 9, 2011)

Thanks Forge US!

I have had your spacer on my son's 11 GTI for 30k miles with no boost codes, so that speaks to the product. It does sound a little ricey, but my son likes it


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## summitsteel (Sep 2, 2014)

i am working for reputed forged elbow manufacturing company...AUDI is my one of the best favorite car...n thank to all guys to share all this information..


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## Kramer1 (May 6, 2014)

I've been considering this mod for about 4months now!! I'm glad this thread got brought back up....good to see and read some background on this mod.


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