TT-RS turbo inlet: better '3 or '4?

[kevin#34]

ECU/TCU stage 2, Wagner Evo 1 IC, high flow downpipe and stock turbo, which inlet better suits the engine needs? I read somewhere that the '4 is better at high rpm, but gives a weaker response at low when compared to the '3 one, is this true, or bigger is better all over the curve?

[DrMerl]

I've got the Wagner, 034 DP, 034 ECU/TCU and 034 4" intake with stock turbo and elbow on E85. I'll be installing their 4" elbow soon. 034 in general designs towards maximizing the stock turbo, they've related in their Q&A videos adding the elbow will add a bit more power, they were not specific where in the power band, but implied their E85S2 programming will accommodate the extra air flow. If they went straight to 4" on the elbow, I'd garner you'd want that, plus works with hybrids. The stock turbo doesn't really light off until about 3800-4K RPM, you don't really want to lug the DAZA below 3500 in high gears. Going with 3" would leave some power on the table.

[kevin#34]

ok, thanks!
any other opinion?

[mtwallace85]

I ran the Unitronic 4” elbow and intake for almost 2 years with the stock tune and you definitely lost some responsiveness and down low torque but gained some top end power. That being said, I think my 0-60 time stayed about the same. I haven’t had the chance to run the smaller elbow but now that I’m stage 2 e85 I don’t really notice the bottom end as much or I’m just used to it at this point.

[kevin#34]

interesting... thanks

[S4Corey]

interesting... thanks

I too experienced the same with 4”
Slight improvement on top end
Def noticed lack of low end response

HOWEVER

I also did i upgraded intercooler at the same time and ran it stock ecu software (intercooler being bigger also mean slight more lag/ response)

That being said,

After flashing the ecu and tcu (1+ 93oct, and stge 2 tcu), the response felt like it was restored and maybe just slightly better than when it was completely stock (like maybe 5-10%)

(I assumed the combination of better ignition timing and throttle mapping more percise and accurate, and on set boost improvements on ecu side, and the transmission shifting behavior on the tcu tune)

I would say go 4” for the head room and crazy top end with software

If you wanna keep it stock, or go as far as like stage 1 pump gas and appreciate the down low oomph as more of your driving style/habits/taste/need/ or want, then the 3” does have its place and might be better suited for you
The one advantage of the 3” is you can retain factory air box and pipe, OR run an after market intake and convert back and forth (weather for resale, parts and or car seperately) while leaving the 3” in car vs 4” which takes more time to install and remove because of size (more awkward than anything) , and requires a lot of messing around to try and get factory air box/intake pipe to work


So in short,
Car is short term for you and just wanna have a little fun with little hassle - 3”

Car is long term and you wanna have maximum fun with upward plans in the future - 4” and be done

[8STTRS]

I'd definitely go with 4". With an AWD car, you will always have some level of advantage with the low end power and how well you can put it down but on the top end, that's where you start to notice the stock turbo running out of steam. Any kind of help on the top end, is always welcome. Granted, I'm saying this knowing that I disliked the power I lost down low but, it was made up for quite a bit by top end power and pull while I was still stage 2.

[Jeff_Jeske]

I have a UNI 3" if you are interested. I also have an APR rear tube to mates with it. LMK

[kevin#34]

thanks to both, plan is to go for Unitronic ECU/TCU stage 2, keeping he stock turbo… really torn between the '3 and '4...

I too experienced the same with 4”
Slight improvement on top end
Def noticed lack of low end response

HOWEVER

I also did i upgraded intercooler at the same time and ran it stock ecu software (intercooler being bigger also mean slight more lag/ response)

That being said,

After flashing the ecu and tcu (1+ 93oct, and stge 2 tcu), the response felt like it was restored and maybe just slightly better than when it was completely stock (like maybe 5-10%)

(I assumed the combination of better ignition timing and throttle mapping more percise and accurate, and on set boost improvements on ecu side, and the transmission shifting behavior on the tcu tune)

I would say go 4” for the head room and crazy top end with software

If you wanna keep it stock, or go as far as like stage 1 pump gas and appreciate the down low oomph as more of your driving style/habits/taste/need/ or want, then the 3” does have its place and might be better suited for you
The one advantage of the 3” is you can retain factory air box and pipe, OR run an after market intake and convert back and forth (weather for resale, parts and or car seperately) while leaving the 3” in car vs 4” which takes more time to install and remove because of size (more awkward than anything) , and requires a lot of messing around to try and get factory air box/intake pipe to work


So in short,
Car is short term for you and just wanna have a little fun with little hassle - 3”

Car is long term and you wanna have maximum fun with upward plans in the future - 4” and be done

I'd definitely go with 4". With an AWD car, you will always have some level of advantage with the low end power and how well you can put it down but on the top end, that's where you start to notice the stock turbo running out of steam. Any kind of help on the top end, is always welcome. Granted, I'm saying this knowing that I disliked the power I lost down low but, it was made up for quite a bit by top end power and pull while I was still stage 2.

- - - Updated - - -

PM sent

I have a UNI 3" if you are interested. I also have an APR rear tube to mates with it. LMK

[Hollingsworth]

If you are planning to go Unitronic stage 2, I think one would have to be crazy to put on a 3" turbo inlet instead of a 4". The stock turbo inlet is supposed to be a major area of restriction. I'd think you would want as much unrestricted flow as possible. If you are going to the trouble of replacing your inlet, go for max benefit. IMHO, with your mods and the intention of doing a stage 2 tune, you should, without question do the 4". If you are worried about being able to keep your stock air box, CTS and APR both make inlet pipes connect a 4" turbo inlet to the stock air box. Anyway, just my IMHO.

On my 21 TT RS with stock tune, I just recently installed a Unitronic FMIC, the new 034 4" turbo inlet, an APR 4" turbo inlet pipe that connects up to the oem air box with a KN filter. The 034 turbo inlet fit perfectly, is of high quality and was an excellent value at $299. I am waiting now for Unitronic to come out with their flex fuel set up, see what it costs, evaluate it, and then make a decision whether to go with the Unitronic or do a DS1.

[kevin#34]

ok, thanks, my only concern about the '4 inlet was an eventual loss of torque at the bottom, but for what I read above, it should be marginal (if any)

[8STTRS]

ok, thanks, my only concern about the '4 inlet was an eventual loss of torque at the bottom, but for what I read above, it should be marginal (if any)

It's really only marginal, albeit noticeable. But, I wouldn't let that discourage you at all. You can adjust to that rather quickly. As others have mentioned, the gains had from a better inlet offset any losses you may get down low.

[kevin#34]

understood, thanks