# Any worthwhile mods to be done to the stock 225HP intake manifold?



## Longitudinal (Nov 13, 2004)

To celebrate my upcoming purchase of an AC/DC TIG machine, I am contemplating the 225HP intake manifold and what improvements might be done to it. 

Has anybody reworked a TT 225HP intake with success? Bigger plenum? Tapered plenum? Rework runners? Anything?


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## 18T_BT (Sep 15, 2005)

Increasing the plenum size alone makes a decent difference. Depends on how involved you want to get, but straightening out the throttle body flange would create much better flow across all runners. This of course, would mean a modification in intercooler piping to the throttle body.


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## ejg3855 (Sep 23, 2004)

18T_BT said:


> Increasing the plenum size alone makes a decent difference. Depends on how involved you want to get, but straightening out the throttle body flange would create much better flow across all runners. This of course, would mean a modification in intercooler piping to the throttle body.


Look to SEM and IE for plenum ideas. Tons of people DIY.

As for the throttle body angle, there is a reason it sits about 9-11 degrees from perpendicular and its not because of piping. Im trying to find the tech article on it to post....


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## 20v master (May 7, 2009)

ejg3855 said:


> Look to SEM and IE for plenum ideas. Tons of people DIY.
> 
> As for the throttle body angle, there is a reason it sits about 9-11 degrees from perpendicular and its not because of piping. Im trying to find the tech article on it to post....


To promote unequal distribution to all cylinders? :laugh:


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## rstolz (Jun 16, 2009)

hahaha!

More to do with the rebounding waveform and turbulence in the plenum. The shorter the runners, the bigger the impact on incoming air. And the 1.8T has really short runners.

My GUESS, is that the angle on the TB helps to redirect incoming air around the turbulence, OR it shields the air on the tubing side of the TB from the same waveform /turbulence.

Looking forward to the article


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## 20v master (May 7, 2009)

rstolz said:


> hahaha!
> 
> More to do with the rebounding waveform and turbulence in the plenum. The shorter the runners, the bigger the impact on incoming air. And the 1.8T has really short runners.
> 
> ...


The angle is there more for packaging requirements (alternator on AWP/ATC/180hp 1.8T's, battery box and tray/fan control module on AUM/BAM/225) than for flow turbulence avoidance. VW/Audi aren't that performance oriented.


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## Marcus_Aurelius (Mar 1, 2012)

rstolz, I believe there is more to it than that though. IMO, the engineers had to deal with lots of packaging restrictions, and many things reflect just that. I don't think there was any waveform or turbulence thoughts put into the deformed plastic pressure sensor pipe that snakes under the battery tray... the battery tray was in the way, and Hans took care of it by designing a deformed length of tubing that would work around the obstacle. :laugh:

If they were going all out to design a performing manifold, they would put much more into it, I think. There are a lot of things that could have been approached differently if that that was the ultimate goal. Personally, I see mass production with packaging constraints in the stock manifold (the injector bung placement right in the middle of the flow path of an already restricted runners is a dead giveaway).
*
Edit: Adam beat me to the punch, but that's exactly my thoughts on the manifold design*


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## 20v master (May 7, 2009)

Marcus_Aurelius said:


> *
> Edit: Adam beat me to the punch, but that exactly my thoughts on the manifold design*


Gotcha!


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## ejg3855 (Sep 23, 2004)

*FV-QR*

I am not to sure I agree with the packaging reason, both 225 and 180s have the angle designed into them. 

Sure its seems like the reasoning, but I'd guess some engineer in Germany said it needs to be this way and they packaged around it. 

I am pretty sure that both IE and SEM incorporate this design feature for the same reasons as VW.


For us Flow Chart Nerds. -> http://josephrinek.com/intakemanifold.html


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## rstolz (Jun 16, 2009)

"Dis iz da only vay, ya!"

I'm completely on board with your guys' assessment of the performance aspects, based on research and VAG tech documents, the original goal for the engine was to be the first PLEV turbo, the outstanding performance almost came across as a happy coincidence. Of course I can't find anything stating that. 

But redirecting airflow and protecting from that waveform is not only a performance thing, it's an efficiency thing, the more air you can get into the plenum in a smooth flow (along the outside wall), the smoother the airflow will be going into the combustion chamber, smoother airflow means more velocity, and more predictable behavior for a better controlled ingress to the combustion chamber.

maybe i'm reading too much into it:screwy: 

some cool tech reads if you're interested, one includes a nifty little calculator:
http://www.enginebuildermag.com/2008/02/intake-manifolds-from-mild-to-wild/

https://www.rbracing-rsr.com/runnertorquecalc.html


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## Marcus_Aurelius (Mar 1, 2012)

I understand what you guys are saying, but I'm almost positive VW didn't put that much thought or effort into it. It totally makes sense if designing something and looking to make able to perform as efficiently as possible, but that was obviously not the case for components of this motor, low cost and mass production was the driving force. I mean, why go through the trouble of optimizing flow into the plenum, when you're going to cast your injector bungs right in the middle of the runners and obstruct any possible gains made in the plenum? It just doesn't make sense to me, and if you look at every other components around, it becomes clear that the goal in the design process was anything but performance. 

Eric, I have an SEM manifold and it doesn't look like Donato thought it was necessary to incorporate the rather large entrance angle that is in the stock unit (which seems consistent with the other performance manifolds out there too, including the VW racing ones they used in those race engines). I could be off, but there is some evidence that the entrance might not have been done in the name of performance.


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## ejg3855 (Sep 23, 2004)

*FV-QR*

I guess since none of us are VW engineers we can agree to disagree on the design intentions. 

I think that emissions was the primary design intent when compared to packaging. If packaging was prime concern many things would be different (SMIC is the first thing that comes to mind)

I could have sworn I read DonR mention the angle in the SEM but looking at mine (haven't seen it in a few months lol).


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## 20v master (May 7, 2009)

The angle that is present on the SEM is due to the taper of the manifold and that you want the air to flow along the plenum wall opposite the runner mouths, as someone said above. That taper isn't present on either OEM intake manifold. This is also why you want to have the throttle plate axis running up and down (relative to the ground) with the plate opening towards the plenum wall opposite the runners (to allow the air to stabilize as much as possible in the plenum to promote even distribution). Don himself would confirm all of what I just typed. The angle that is present in the throttle flange on OEM manifolds has nothing to do with performance, resonance, turbulence, etc. If you can't look at both unmolested AWP and AMU engine bays and see that, then you aren't thinking like an OEM that has many different factors to include in the design rather than all out performance (cost, packaging, weight, ease of installation, etc). From my 1.8T intake manifold comparison......



> OE Small Port Comes free with your car.
> Hated the throttle angle. Again, they commented on air not wanting to make that kind of turn, and said they (VW) set themselves up for failure from the get-go by pointing the throttle at the roof of the intake over cyl 2. And again, they hated on the injector bosses.


Those are my own words, and the description was based on comments from the flowbench operator that tested all the intake manifolds. This was done 7.5 years ago, and nothing has changed in terms of fluid dynamics and engine tuning, so I'd say the throttle angle still isn't good for flow, velocity, and smooth (relative to more turbulent) airflow into the plenum. Would anyone think that same angle is good for flow into your turbo inlet, your intercooler inlet, or your throttle body inlet? If so, I have some HP boosting snake oil to sell you too.


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## rstolz (Jun 16, 2009)

> Would anyone think that same angle is good for flow into your turbo inlet, your intercooler inlet, or your throttle body inlet?


No, but then again, those other inlets have different forces to contend with.

It also sounds like that quote in your post is focused on the AEB intake, as that's the only one with a goofy upward angle pointing directly over cyl 2.

The angle on an AMU intake, whether intentional or not, will promote the smoothest possible airflow into the plenum. Is it essential? Not at all. Is the benefit going to be noticeable from the drivers seat? Probably not. Is a tapering of the plenum more effective? Probably, but that could also just be the increased total volume.

None of this is arguing right or wrong, just speculating on intake design decisions. We should be able to share ideas and info without resorting to "I'm right, you're wrong".

In that vein, 20V, do you have a link to that full article or conversation? I'd be interested in taking a gander at it.


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## [email protected] (Dec 14, 2013)

Nice wish I had/could tig weld congrats. I would love to have you tig weld a map sensor flange on my awic pipe ....if you really need something to weld


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## Longitudinal (Nov 13, 2004)

[email protected] said:


> Nice wish I had/could tig weld congrats. I would love to have you tig weld a map sensor flange on my awic pipe ....if you really need something to weld


Will weld for money.


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## 20v master (May 7, 2009)

rstolz said:


> No, but then again, those other inlets have different forces to contend with.
> 
> It also sounds like that quote in your post is focused on the AEB intake, as that's the only one with a goofy upward angle pointing directly over cyl 2.
> 
> ...


It doesn't matter "the forces," it's all about flow velocity. Turns and changes or direction are bad for flow. That's not hard to understand. Some are inherent, some aren't. The angle on the inlet of the throttle isn't. I can assure you that Don's CFD showed it wasn't a benefit at all, or it would be incorporated into the SEM manifold. I was closely in contact with Don during development of the 007 manifold and the SEM manifold, and saw most of his CFD work. Also, no AEB intake was tested. A large port passenger side throttle transverse manifold was tested. The placement of injectors in the flow path directly at the port is the same for AMU/BEA, AEB, and ATC/AWP manifolds. If you think the throttle flange angle is good, why isn't it present on other intake manifold designs? It isn't a matter of me being right, it's that you guys are attempting to justify something that is a detriment to flow and even distribution. 

This can also be seen from the fact that w/m injection users with a single nozzle in a throttle plate see uneven distribution of their injection, with the cylinders farthest from the plenum (1,2 on AMU, 3,4 on AWP) inlet getting less than the cylinders closer (3/4 on AMU, 1/2 on AWP).


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## Marcus_Aurelius (Mar 1, 2012)

I haven't done much in terms of flow testing like Adam or CFD analysis like Donato, but I can attest to water injection exposing the flow-distribution flaws of the stock manifold (was discussed and documented in one of my threads about IAT charge cooling). 

The cliffnote on that is with nozzle placed and spraying downstream of the throttle body, the first and second runners would starve (first runner), and struggle (second runner) to get fluid, while the other two runner farthest to the TB would get most of the injection (I talk only of runners instead of cylinders to keep the conversation consistent between driver/pass manifolds). This is a clear and empirical demonstration of the flow-distribution deficiencies of the stock units with the large entrance angle. 

To support what was a theory at the time, I then placed a single, dedicated, nozzle in the plenum to supply the first two runners (was a necessity as I would get timing correction only in those problematic runners starving for juice at 30+ psi). Well, the result told the whole story (at least for me), the two runners that were struggling to get fluid became the ones with the least corrections when things got pushed further. This whole thing is what lead me to dive into experimenting and consequently running a direct port setup with 4 nozzles in the plenum to ensure even distribution to all the runners. 

This experiment is far from proving exactly what another medium is doing (pressurized air will undoubtedly behave differently than straight water or an alcohol mix). However, I think it shows clearly that the angle of the throttle body placement, is detrimental to distribution at least with the suspended water droplets... it just shoots the heavy fluid right over the first runners and towards the last two. I'd put my money on airflow distribution not deviating much from how the suspended water droplets did.

Edit: here one of the thread where the distribution problems of the stock mani was brushed 
http://forums.vwvortex.com/showthre...Charge-Cooling-quot-a-different-approach-quot


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## rstolz (Jun 16, 2009)

Cool stuff on W/M. 

Don't confuse "smoothest flow into the plenum" with "optimal distribution to the runners." They are separate. 

No one is invalidating the work that's been done to date with SEM's intake and W/M. The biggest thing is just to not dismiss design details just because you (I mean the royal "you", not anyone specifically) don't understand why they were made. 

Consider that most users rarely use WOT, spending most time between 2-3k rpm. At this point the throttle plate is not open very far, which, without the bend, leaves 2 sharp bends for the air to get around before entering the plenum chamber. With the offset bend, you reduce one of those angles and promote smoother flow, which becomes a detriment as the throttle opens further and further.

just a thought, one that maybe got overlooked when pursuing power. And that, honestly, is fine, as anyone looking to drop serious cash on an intake, is likely not very interested in low end response, preferring the upper ranges. 

What improves response at the low end, is generally a detriment at the high end.


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## Don® (Oct 11, 2011)

Going to chime in here briefly; Adam pretty much summed up the essential aspects of the SEM development.
As for the stock intake and its angle of entry, it's solely for packaging, not performance.
If you have a manifold that distributes airflow very well then W/M would essential follow the same path in the case that W/M is injected pre or at the TB.
W/M for individual runners, would of course be best located at the highest point of velocity.


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## 20v master (May 7, 2009)

And there's the source.....thanks Don. :beer:


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## Marcus_Aurelius (Mar 1, 2012)

Don® said:


> As for the stock intake and its angle of entry, it's solely for packaging, not performance.
> 
> If you have a manifold that distributes airflow very well then W/M would essential follow the same path in the case that W/M is injected pre or at the TB.


Thanks for your input! It made no sense to me that VW engineers would go out of their way to promote airflow into the plenum (as it was suggested), if the effort ultimately went against proper flow distribution to the runners. That angle must be mostly for packaging IMO.


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## PernellGTI (Jan 1, 2010)

*Intake mods*

I didn't dyno the car, but I ported the inlet to 70mm, and slightly ported the runers, added a 70mm TB and the difference was night and day, much more response and a lot more power in the top end. I was really happy. I would imagine increasing plenum size also would yield more power if done well. If you have the means, why not try?


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