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  1. #1
    Veteran Member Four Rings
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    1996 Audi A4 2.8 V6 quattro; 2009 Dodge Journey, KLR250
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    2.7T - intake bottlenecks - Bi-Pipes?

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    Aside from the 'feel good power increase' (as many modifications carry), is there a REAL benefit in upgrading the intake side of the 2.7T?
    Which parts truly represent bottlenecks, considering a power level of say a) K04 b) RS6 turbos?
    Also considering 'bang for the buck' ratio:

    - Bi pipes
    - Y pipe
    - larger MAF
    - larger TB
    - RS4 intake plenum
    1998 Passat 1.8T, Kraftwerk Turbo TM2, 550cc, 3" MAF, 3" DP, FMIC, S4 clutch, SMFW, FSI coils, C3 stg 5 tune
    1999 Passat 1.8T, Kraftwerk Turbo TM3, 550cc, 3" MAF, 3" DP, FMIC, FSI coils, SMFW, Krafterk Turbo tune
    2001 Allroad 6 spd, custom stg 1
    2002 Allroad 6 spd, Kraftwerk Turbo TM4, 750cc, 3" MAF, piggy, FMIC, CM stg 5
    1996 A4 2.8 stock, terrrible gas mileage
    www.regulatorfix.com
    www.kraftwerkturbo.com

  2. #2
    Veteran Member Four Rings Trigger Happy's Avatar
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    Jun 17 2008
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    30034
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    2K S4
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    Rockville, MD

    IMHO the biggest restrictions to our intake are the bi-pipes, stock airbox, and maf in that order. I have upgraded my bi-pipes to the ARD 2.125" ones and I can vouch for how much better they will flow. The stock pipes are tiny, I can't even fit my finger through part of them, while the ARD's are round the entire way through, also ceramic coated. The stock airbox is easy to fix and has proven gains in flow. There are logs floating around here that shows the difference between a darintake (swiss cheese airbox) and the stock model showing that the DARintake flows better. That plus a good cone filter adaptation is probably the best bang for your buck on the intake side of things. The maf is just small and gets changed out with every tune I know of, so again no real world data, but logic says bigger is better. Almost all the other intake mods get expensive fast. Technically intercoolers are part of the intake too and adding larger ones will flow and cool better.
    "Clearly, a liger is not as practical as a Katana. S4s can't carry ligers. fucking 500lb cat in my backseat using my alcantara as a scratch post for its HUGE FUCKING CLAWS? I dont' think so bro"

    Understeer is when you hit the wall with the front of the car and oversteer is when you hit the wall with the rear of the car. Horsepower is how fast you hit the wall and torque is how far you take the wall with you.

  3. #3
    Veteran Member Four Rings
    Join Date
    Feb 20 2010
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    1996 Audi A4 2.8 V6 quattro; 2009 Dodge Journey, KLR250
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    Brighton, MI

    Trigger:

    Thanks for your suggestions/tips.

    I take your word regarding benefits/restrictions from bi pipes and put them on my list.

    Darin intake: I did it, but did NOT log an performance difference. Could be that the rest of my current setup is hitting the limits (assuming that even on my custom stage 2 tune, the ECU throttles back to 'safe' limits if for example fuel injectors are maxed out, IAT getting to high, or similar). IIRC, there is also a very detailed post out there measuring the impact of the Darin mod with really detailed data logs during various driving conditions. He did not find any improvements that are not falling within the measuring tolerance/variations.

    Also IMO, any cone MUST hold up to a physics/math check: surface area bigger than stock.

    And certainly cannot be a 'HOT AIR INTAKE' (as seen on lots of kids' cars, trading a functional true cold air stock intake for a HOT air intake (that admittedly may be a nice noise maker). Consequently, it need to suck in cold air from the front (or other places). Carbonio does it right, or cone in stock box (plus Darin?) (only if larger surface area can be fit in).

    MAF limit: larger MAF housings are installed not because they are a flow bottleneck, but rather that the sensor measures air speed, and is calibrated to provide a max output signal (5V I think?) when the max speed it is designed for has been reached. Modified engines need to flow more air. Increasing the MAF area (and corresponding change of the tables so the ECU gets the correct flow reading) reduces the air speed in the same ratio as the area increases, thus also increasing the upper limit (example: 72 mm ID to 85mm diameter = 1.18 diameter increase = 1.39 area increase. Stock MAF measuring limit (say 280 g/sec - I am at 260 g/sec) x 1.39 = new measuring limit of 389 g/sec. The limit is signal limit, not necessarily a flow restriction.

    Intercooler: any increase in volume in the 'pressurized' part of the intake will also result in an increase it lag (more air volume means more time to compress). So 'bigger is better' deserves an asterix, or at least be aware of the downside. I have looked at 800HP twin turbo 300ZX with huge turbos (and similarly upgraded Supra) and was amazed by the (relatively) small diameter piping they run. I put 2.5" piping on my 1.8T (and regret getting the 2.75 thick intercooler (cause lots of install headaches and was clearly NOT needed for my relative mild power goal of 300 hp). Next 1.8T will get 2.25 piping (2.5 max) and 2.5 thick intercooler.

    In a similar fashion on the exhaust side: I found that back pressure is NOT only your enemy, it is also your friend (if you are looking for reduced turbo lag, spool up. At least for low/mid range torque/power. High rpm peak HP applications are a different story, I am sure.

    Surprised that no one is hitting on the throttle body diameter? In my naturally aspirated (Corvette) times, this was one of the first things to do. Not an issue on our turbo engines?


    Quote Originally Posted by Trigger Happy View Post
    IMHO the biggest restrictions to our intake are the bi-pipes, stock airbox, and maf in that order. I have upgraded my bi-pipes to the ARD 2.125" ones and I can vouch for how much better they will flow. The stock pipes are tiny, I can't even fit my finger through part of them, while the ARD's are round the entire way through, also ceramic coated. The stock airbox is easy to fix and has proven gains in flow. There are logs floating around here that shows the difference between a darintake (swiss cheese airbox) and the stock model showing that the DARintake flows better. That plus a good cone filter adaptation is probably the best bang for your buck on the intake side of things. The maf is just small and gets changed out with every tune I know of, so again no real world data, but logic says bigger is better. Almost all the other intake mods get expensive fast. Technically intercoolers are part of the intake too and adding larger ones will flow and cool better.
    1998 Passat 1.8T, Kraftwerk Turbo TM2, 550cc, 3" MAF, 3" DP, FMIC, S4 clutch, SMFW, FSI coils, C3 stg 5 tune
    1999 Passat 1.8T, Kraftwerk Turbo TM3, 550cc, 3" MAF, 3" DP, FMIC, FSI coils, SMFW, Krafterk Turbo tune
    2001 Allroad 6 spd, custom stg 1
    2002 Allroad 6 spd, Kraftwerk Turbo TM4, 750cc, 3" MAF, piggy, FMIC, CM stg 5
    1996 A4 2.8 stock, terrrible gas mileage
    www.regulatorfix.com
    www.kraftwerkturbo.com

  4. #4
    Established Member Two Rings
    Join Date
    Apr 12 2011
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    Location
    Canton, OH

    The lower (hot side) intercooler S-hose (D/S) is a major bottleneck as well. It has very arbubt changes in direction in a small area. Also, not a popular change, but I am not hot on the shape of the cold side S-hose leading from both intercoolers to the bipipes. There is room for a more gradual transition here.

    -Bryan
    2003 Audi A6 2.7T - TIP - Type-RS DVs, Darrintake, custom oil cooler, -8an breather tank, 2.5" catless exhaust with X-pipe, Magnaflows and Manual Cutouts, 17" BBS RC Wheels, Front StopTech Slotted Rotors & Hawk HPS Pads, stock k03s still rockin' at 113k!

    2006 VW Jetta - TIP - Wife's Wip, all stock still

    2001 VW Jetta 12v VR6 - 5spd - VR6 turbo project underway

  5. #5
    Veteran Member Four Rings
    Join Date
    Feb 20 2010
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    1996 Audi A4 2.8 V6 quattro; 2009 Dodge Journey, KLR250
    Location
    Brighton, MI

    Quote Originally Posted by TwinTurboYacht View Post
    The lower (hot side) intercooler S-hose (D/S) is a major bottleneck as well. It has very arbubt changes in direction in a small area. Also, not a popular change, but I am not hot on the shape of the cold side S-hose leading from both intercoolers to the bipipes. There is room for a more gradual transition here.

    -Bryan
    I am putting new (silicone) hoses on the engine (while on the engine stand); will take a look how bad it is.

    Down the road (for next upgrade step with K04/RS6 type turbos, clutch, etc), the stock side mount IC will be replaced with FMIC. Hope this will also make the hot piping smoother?
    1998 Passat 1.8T, Kraftwerk Turbo TM2, 550cc, 3" MAF, 3" DP, FMIC, S4 clutch, SMFW, FSI coils, C3 stg 5 tune
    1999 Passat 1.8T, Kraftwerk Turbo TM3, 550cc, 3" MAF, 3" DP, FMIC, FSI coils, SMFW, Krafterk Turbo tune
    2001 Allroad 6 spd, custom stg 1
    2002 Allroad 6 spd, Kraftwerk Turbo TM4, 750cc, 3" MAF, piggy, FMIC, CM stg 5
    1996 A4 2.8 stock, terrrible gas mileage
    www.regulatorfix.com
    www.kraftwerkturbo.com

  6. #6
    Established Member Two Rings
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    Canton, OH

    Quote Originally Posted by vtraudt View Post
    I am putting new (silicone) hoses on the engine (while on the engine stand); will take a look how bad it is.

    Down the road (for next upgrade step with K04/RS6 type turbos, clutch, etc), the stock side mount IC will be replaced with FMIC. Hope this will also make the hot piping smoother?
    Depends on the routing of the pipes. For example the JHM kit is very nicely designed with smooth transitions and smooth bends. However, I've never personally been a fan of a stacked FMIC wherein the top core receives limited air flow (unless you cut the bumper cover). When I do my FMICs I will have two individual, side by side (although welded together for one solid unit, but the tanks and cores will have their own individual circuits) mounted up front. Looking at the Treadstone same side style, these seem to have promising results.
    2003 Audi A6 2.7T - TIP - Type-RS DVs, Darrintake, custom oil cooler, -8an breather tank, 2.5" catless exhaust with X-pipe, Magnaflows and Manual Cutouts, 17" BBS RC Wheels, Front StopTech Slotted Rotors & Hawk HPS Pads, stock k03s still rockin' at 113k!

    2006 VW Jetta - TIP - Wife's Wip, all stock still

    2001 VW Jetta 12v VR6 - 5spd - VR6 turbo project underway

  7. #7
    Veteran Member Four Rings
    Join Date
    Feb 20 2010
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    1996 Audi A4 2.8 V6 quattro; 2009 Dodge Journey, KLR250
    Location
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    In theory, the covering up the top more than the bottom in 'dual stacked' FMIC may pose a problem. Not sure if in practice the intake temp will vary much between top and bottom (and they get mixed anyway). So weather you cover up symmetrically, or not: total combined cooling result will be the same. Plus, there is lots of air turbulence and flow, even if covered. Think of those rear mounted radiators in Baja cars. In our case, there is the pusher and the puller fan, and 2nd puller.
    I don't worry too much about it.

    I have the standard JHM design in mind. There is also a new style, 2-in 1-out. Can't remember if they are stacked vertically or horizontally, or else. Aside from plumbing benefits (trading one larger intake pipe against 2 smaller), I don't see much benefit either (assuming total heat exchanger surface is the same). Plus 'novelty' charge of $100 or so.

    Love your turbo Caravan!! I gave up on my twin turbo Pacifica 4.0l V6 (already had custom lowering springs (couldn't find ANYBODY to offer ANY firmer shocks!), 22x9.0 wheels with 265/35x22 Yokohama) when I couldn't find ANYBODY to tune the auto trans (I could have lived doing the engine as standalone or piggy (Haltech), but the trans definitely needed to be adjusted for the higher torque, shift points; auto stick to hold gears no matter what (only low/high rev override)).
    1998 Passat 1.8T, Kraftwerk Turbo TM2, 550cc, 3" MAF, 3" DP, FMIC, S4 clutch, SMFW, FSI coils, C3 stg 5 tune
    1999 Passat 1.8T, Kraftwerk Turbo TM3, 550cc, 3" MAF, 3" DP, FMIC, FSI coils, SMFW, Krafterk Turbo tune
    2001 Allroad 6 spd, custom stg 1
    2002 Allroad 6 spd, Kraftwerk Turbo TM4, 750cc, 3" MAF, piggy, FMIC, CM stg 5
    1996 A4 2.8 stock, terrrible gas mileage
    www.regulatorfix.com
    www.kraftwerkturbo.com

  8. #8
    Established Member Two Rings
    Join Date
    Apr 12 2011
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    73869
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    Canton, OH

    Quote Originally Posted by vtraudt View Post
    In theory, the covering up the top more than the bottom in 'dual stacked' FMIC may pose a problem. Not sure if in practice the intake temp will vary much between top and bottom (and they get mixed anyway). So weather you cover up symmetrically, or not: total combined cooling result will be the same. Plus, there is lots of air turbulence and flow, even if covered. Think of those rear mounted radiators in Baja cars. In our case, there is the pusher and the puller fan, and 2nd puller.
    I don't worry too much about it.

    I have the standard JHM design in mind. There is also a new style, 2-in 1-out. Can't remember if they are stacked vertically or horizontally, or else. Aside from plumbing benefits (trading one larger intake pipe against 2 smaller), I don't see much benefit either (assuming total heat exchanger surface is the same). Plus 'novelty' charge of $100 or so.

    Love your turbo Caravan!! I gave up on my twin turbo Pacifica 4.0l V6 (already had custom lowering springs (couldn't find ANYBODY to offer ANY firmer shocks!), 22x9.0 wheels with 265/35x22 Yokohama) when I couldn't find ANYBODY to tune the auto trans (I could have lived doing the engine as standalone or piggy (Haltech), but the trans definitely needed to be adjusted for the higher torque, shift points; auto stick to hold gears no matter what (only low/high rev override)).
    Nice! Never heard of anyone doing a turbo setup on a Pacifica. Would be fucking sick though! And ya thje Van does something for me that the Audi simply can't do. Its such a blast driving around and having people pointing, laughing and kept confused.

  9. #9
    Veteran Member Four Rings
    Join Date
    Feb 20 2010
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    1996 Audi A4 2.8 V6 quattro; 2009 Dodge Journey, KLR250
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    Brighton, MI

    Quote Originally Posted by TwinTurboYacht View Post
    2.5" catless exhaust with X-pipe, Magnaflows and Manual Cutouts
    My AR 6 spd is now on the hoist. Still stripping, but engine/tranny should be out end of this week. Tranny goes for synchro overhaul; spare engine with custom K04/RS6, 85mm billet MAF, 5 bar MAP, 750cc EV14, custom tune, JHM FMIC, Clutchmaster 6 puck w/single mass steel FW going in. Debating if I should sand and paint the intake Y on top of the engine. Couldn't find a resonably priced solution to upgrade the intake piping (even so some posts here suggest it IS a bottleneck).

    Saw "2.5" catless exhaust with X-pipe, Magnaflows and Manual Cutouts" in your SIG. I decided to keep my gutted stock downpipes, and are not too concerned that the stock exhaust is too restrive (and backpressure is not ONLY bad; see above). But my stock exhaust has NO sound. Can't stand 'tin can' sound some S4 kids are driving around with. The Miltek with resonator on my 1.8T A4 was PHANTASTIC; just nothing like it out there. Deep, just loud enough, NO resonance. Just the way a good exhaust should sound. I trust the Miltek version for my 6 spd AR would be just as good, but COST PROHIBITIVE! I already looked into the cut out option, and now would be the time. I would try an electric system (tuner would send trigger signal based on boost, throttle position; RPM if all fails. Plus a push button for manual).

    What X pipe (brand/type, source)?

    What Magnaflows (type/number, source)?

    No resonators?

    Where did you locate the cut outs? I would towards the rear, maybe after resonators?
    Maybe a photo of your setup showing the layout?

    How do you activate the manual cutouts?

    Do you have a decent soundfile? Post or email to info@regulatorfix.com
    1998 Passat 1.8T, Kraftwerk Turbo TM2, 550cc, 3" MAF, 3" DP, FMIC, S4 clutch, SMFW, FSI coils, C3 stg 5 tune
    1999 Passat 1.8T, Kraftwerk Turbo TM3, 550cc, 3" MAF, 3" DP, FMIC, FSI coils, SMFW, Krafterk Turbo tune
    2001 Allroad 6 spd, custom stg 1
    2002 Allroad 6 spd, Kraftwerk Turbo TM4, 750cc, 3" MAF, piggy, FMIC, CM stg 5
    1996 A4 2.8 stock, terrrible gas mileage
    www.regulatorfix.com
    www.kraftwerkturbo.com

  10. #10
    Veteran Member Four Rings
    Join Date
    Jan 06 2007
    AZ Member #
    14660
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    01/02 S4, '04 Mazdaspeed MX-5
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    Virginia

    Quote Originally Posted by Trigger Happy View Post
    I have upgraded my bi-pipes to the ARD 2.125" ones and I can vouch for how much better they will flow. The stock pipes are tiny, I can't even fit my finger through part of them, while the ARD's are round the entire way through, also ceramic coated.
    ~5% over stock. A better option is the APR bipipe that flows ~12% over stock.

    Stock -> APR Stg1/2 -> GIAC Stg2 -> APR K04 Stg3 -> EPL/TiAL 605 -> V̶A̶S̶T̶ EPL/Frankenturbo F4H -> Audi Tuned K03's
    MyAudiS4.com

  11. #11
    Veteran Member Four Rings
    Join Date
    Feb 20 2010
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    1996 Audi A4 2.8 V6 quattro; 2009 Dodge Journey, KLR250
    Location
    Brighton, MI

    Has anybody logged the MAF readings before/after upgrading the bypipes? Or before/after quartermile times, or dyno?
    I still remember the 'pazebo effect' of the 'Darin Intake Mod'. I was impressed, too. Then did 6 log runs (3 with stock, 3 with 'Darin'). Unfortunately, the 'spread' (statistical variation) was larger than the effect, i.e. a statistical 'nope' or 'not measurable'.
    1998 Passat 1.8T, Kraftwerk Turbo TM2, 550cc, 3" MAF, 3" DP, FMIC, S4 clutch, SMFW, FSI coils, C3 stg 5 tune
    1999 Passat 1.8T, Kraftwerk Turbo TM3, 550cc, 3" MAF, 3" DP, FMIC, FSI coils, SMFW, Krafterk Turbo tune
    2001 Allroad 6 spd, custom stg 1
    2002 Allroad 6 spd, Kraftwerk Turbo TM4, 750cc, 3" MAF, piggy, FMIC, CM stg 5
    1996 A4 2.8 stock, terrrible gas mileage
    www.regulatorfix.com
    www.kraftwerkturbo.com

  12. #12
    Active Member Two Rings
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    Nov 19 2013
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    Items for Sale

    Sorry guys but I need help and don't know how to post my post on tech.
    So I just got a s4 b5. Pulled out on the street and paddle to the metal and shifting from 2nd to 3rd loud pop under the hood and in Exhaust and the car shut off. I bought the car two days ago, it had few codes when I scanned it with vag com. It was coolant temp sensor, cat converters/ 02 sensors, and multiple mis fire. I had a chance to change the coolant temp sensor and drove it about 20 miles after changing it and this happened. The car was making loud belt, pulley or fan noises when It ran, like usual German cars but a bit louder. I managed to sneak by fingers thru the timing belt covers and the belt is still attached properly but isn't as tight as is it should be. Please help me out here. Thanks in advance



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