# f21 vs. f23 on a FWD 180hp



## pneffkell (Jul 8, 2015)

So I have an 02 tt FWD and I am looking to do a turbo upgrade. I want to try to get a reliable 300whp. Frankenturbo says to use the f21 on the 180 but I wanted to know what would it take to do an f23. I have the 034 modular downpipe. Is the difference just a downpipe fit issue or is there more to makeing the F23 fit?


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## ttwsm (Feb 27, 2011)

If by "fitment" you refer to the 180 degree inlet direction difference and different turbo housing, I suspect yes, it's mostly fitment. The Frankenturbo value proposition seems to mostly be about minimizing fitment issues by using the same turbo housing - I think that's why they recommend F21 for K03-based engines and F23 for the K04-based engines.


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## jsmith2015 (Mar 7, 2015)

You would need a 225 exhaust manifold downpipe and oil and coolant lines for the turbo to make the f23 fit. You can get all that from franken turbo just more dollars

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## jsmith2015 (Mar 7, 2015)

If you are going to try and fit the f23 as far as cost goes your not far from just going with a gt28

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## pneffkell (Jul 8, 2015)

*thanks*

Thanks guys. In looking into it. It feels like the value point here is the f21. It just snowballs to try to move to the f23


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## cdketrow (Dec 21, 2014)

Just another thing to keep in mind. The intercooler system on the 180 is different from the 225 (which is what the F23 was built for). There is only one SMIC on the 180 vs the 2 SMIC's on the 225. That's going to manifest itself in high intake air temps. It may be a good idea to look into an FMIC or a 225 Intake Manifold and the entire intercooler system from a 225. I'm not sure what that conversion process would look like, but that seems like a round about way of getting to 300 whp. There are going to be quite a few supporting mods required with the f23 as well like an upgraded fuel pump, and larger injectors are suggested as well. Talk with Doug at Frankenturbo. He helped me out a lot with my f23 build and any questions I had along the way. Great guy, great customer service. I don't want to sound too much like a downer, so in light of this post, anything is possible with a bit of ingenuity and of course the all powerful $$.


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## v_dubn (Dec 30, 2010)

Not looking to argue but having a larger turbo often leads to cooler air charge. And also able to flow better. No disagreeing that the OP should upgrade the intercooler,first in fact, but simply adding a larger turbo won't necessarily raise the intake air temp.


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## pneffkell (Jul 8, 2015)

*Quick Update*

Figured I would write a quick update. I decided to go ahead and go with a CTS turbo FMIC. It is every arrives I will be installing it. I had some good conversations with Nick at Turbo Concepts and I am going to be running one of there stage three turbos. I should have the turbo by tuesday of next week so next weekend should be the big day to intall. Nick seems to know his stuff and he was very open to having a back and forth conversation about how he builds his turbos and the quality materials he uses. They actually have some of their parts cast up in Detroit and he seems to have a real focus on quality materials.

I decided to go with Motoza for my tuning. I have a lot going on in this car and I want to get the tune right. Their entire process involves several rounds of tuning. My current revo tune runs so rich its crazy so it was important for me to get something more custom this time round. 

I am also going with a Grams 70mm throttle body & a set of 550 injectors. 


This weekend I am replacing all of the a/c components, the oil pan and pickup, and doing some other general cleanup and maintenance. I am really looking forward to getting this thing back on the ground.


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## cdketrow (Dec 21, 2014)

v_dubn said:


> Not looking to argue but having a larger turbo often leads to cooler air charge. And also able to flow better. No disagreeing that the OP should upgrade the intercooler,first in fact, but simply adding a larger turbo won't necessarily raise the intake air temp.


The higher compression of air directly correlates to it's increase in temperature. For more information of Gay-Lussac's Law of thermodynamics click on the nerd alert. There is a reason Audi puts one SMIC on a K03 setup and 2 FMIC's on a K04 setup. 

Nerd Alert!


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