Are Franken F21 Turbos a Good Choice? Change my Mind.
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Being that Stage 3 is in the future.. It's time to start looking at options! Tell me.. Are Franken F21 Turbos a good choice?? Here's what I think.
Twwinnnn Turbskiii's boys
Ignoring price, I think the F21 is the best choice. First, I think it is best to ignore bigger turbo options.
1. Due to the car being so heavy with the weight in the front, and
2. the fact that heat is what kills the 2.7 engine (not just the turbos, but all the rubber/plastic bits in the engine too), the B5 S4 does not make a good track car.
3. The engine starts throwing rods around 500 HP and other components start failing after that. Once you hit higher numbers, you have to build out the engine which makes it less desirable to actually drive (we are spending $10k+ to enjoy the car right?).
4. Things like a heavier clutch and constantly rowing gears really makes it less enjoyable, and makes gas more expensive, etc.
5. The appeal to the 2.7t is that having two smaller turbos rather than one big one lets the engine have a huge flat diesel-like torque curve ala less spool time. Bigger turbos means more spool which takes away from what makes the engine great.
With all of these reasons, IMO it is best to rule out bigger turbos (RS6, tials, etc).
The sweetspot for this car is the 400-460 HP range- enough to still be really fast, well behaved to drive, gas is still expensive but defensible, etc. So that leaves the smaller turbos- KO3, KO4, F21, and other hybrids. There's nothing inherently wrong with the KO3, but the KO4 and F21 push way more air than KO3s so that rules that out. Between KO4 and F21, the F21 has slightly more spool time but considerably better top end, which is a net gain. Frankenturbo also has excellent customer service and a long track record of reliability.
The above heuristics is how I came to be using F21 turbos. I've had them since 2014 and I average ~17,000 miles per year. No matter what turbos you get, if you drive like a reasonable person, they will last just fine. If you drive like a college kid that bought a $7000 twin turbo car, you will blow them up. Don't be a stereotype. Turbos are considered a wear item with a maintenance interval (really, check the maintenance schedule in the owners manual) and will all fail with abuse.
I'm a Pennsylvania kid and I bought my S4 during college too.
I think you wrote a bunch of shit you read on forums
F21s are a good turbo option I would not deny that. Are there better options out there. Yes there are. I have tuned a few F21 cars and even more k24 cars and I recommend the k24s over the F21s even tho the f21do spool a little faster. I daily drive my S4 74 miles a day with K24s and almost 40k miles on them and I love the all around power they provide. The F21s will be suited better for 1-3rd racing but once you get to the top of 3rd and into 4th a k24 car will be gapping a k04/F21s car running pump gas. E85 is a while other discussion. I would not recommend running F21s on a stage 1 or 2 tune you will be maxing out the stock injectors. A stage 3- tune with a 5bar fpr is needed but I recommend just upgrading fueling to stage 3 at the same time at least 550cc injectors, walbro 450, DW300 and 85mm maf housing. I know this is a lot of info but I have a lot more if you need it.
Where are you from GermanELiteTuning?
smokinblu81 Phoenix Arizona.
German Elite Tuning what are the pricing differences? I guess for UA-cam videos, 4th and 5th acceleration is good, but the majority of the time, you'll be in around town. Aren't the F21's more reliable? Thanks in advance
Warren A Journal bearing k24s are $1695 plus inlets, hardware kit and oil feed lines of you want them. The Ballbearing option is another $900. It’s hard to really say what’s more reliable most of my experience is with K24s and they have been performed very well and have been reliable.
I agree. Frankens are nice for sure but... I'm going k24s on mine.
I’d still buy the k04 from FCPEuro with that lifetime warranty. If you ever blow a turbo or two the cost will offset. This is just me stayin on the safe side though.
A friend of mine had a set come to him in his shop to be rebuilt. Turns out they modify the turbine shaft and compressor wheels. They can’t be rebuilt unless you modify the turbine shaft and compressor wheel once again. I’d go with genuine KO4 RS4’s or SRM with RS6 compressor wheels.
I have f21's and I like them. But I haven't driven anything else. I went with 750cc injectors and all the other stage 3+ stuff with an E85 tune. I daily drive my car and I'm dealing with a minor boost leak but it's still fast and fun! Beat a Z06 with the boost leak!
I’m trying to buy one that’s really cool absolutely good to know
Tune it the k03s they're going to blow it took me maybe 8k.went k04 with an apr tune after and blew one but beat it for 45k.got about 8k on the f21 with a daz tune on 93 it pulls good no issues.that is just the turbos this thing is a money pit I've owned my b5 for 12 years and believe me it breaks alot.2 transmissions later multiple motor pulls I still own it and the f21 setup is running great.you will be spending money to keep this car on point but it's worth it imo.
If i could post pictures i would show you how on one of members of the facebook page im part of just bought F21s and went all out with custom pipes, wrap ect. One of the F21s then BROKE. The weld at the wastegate just broke off. And as u know, its an engine pull to get to them. And then another guy who had them and they didnt last 10,000 miles. GO TURBO CONCEPTS. GO TURBO CONCEPTS. But im running PJK04s from Rotomaster. Assembled and balanced in North America, $1600 with inlets and 85mm MAF housing. 20,000+ miles on 18 and now 20psi (soon to be 22) with no issues. Im running rotormaster turbos, 630cc EV14 injectors, JHM's Lightweight flywheel B7 RS4 clutch combo, downpipe decat, stock airbox, and a tune from Aaron W. Hes in PA. Does remote tunes.
You got his info for the tuning. I'm bout to swap turbos and need a good tune guy
Im kind of in the same boat as you. Im still in college and I bought a B5 S4 3 months ago. Im in the process of putting on F21 turbos and going stage 3. I got them because it was one of the cheaper options available. Keep up the good work man!
Just had my K03’s rebuild and ballanced with 360’ thrust bearings, the stock K03, K04 use the same 270’ thrust bearing the main difference is the size of compressor and exhaust turbine. The 360’ thrust s better for extended higher boost. $75.00 for one 360’ performance bearing kit. The upgraded bearing also has 3 oilers as opposed to a single oiler.
How are you liking the k03s with the upgraded thrust bearing? How much boost are you running?
I'm really curious on how k03s with better bearings hold out
I’d say go for BWK04. OEM spec is proven and reliable power as they’re seen in stock RS4’s here. Saying that, it’s nice to go different and try the Frankenturbos’s and blog how long they’ll last :)
As some other on here have said I'd look strongly at turbo concepts. I'm running their stage 3 turbos and very happy with them. The customer support they have is fantastic. Another local s4 is running the same ones as me on e85 and is making over 500whp. They spool great and I haven't seen any issues with them so far
Andy Reed for how long have they been running the turboconcepts
Hector Santiago I've ran them for 3k miles I'm not sure how long he has but at least 2 years
Dude I just bought f21s last weeks so I hope so!! Lol . Also the reason I didn’t go k24s or rs6. I did some research and found some 2.7t engines had bended rods pushing around 450whp in one of the cases 440hp so I want maybe 420whp to be on the safe side since I want my car to last at least a couple years
Turbo at 197k on my 1.8T and still running strong 💪
slow a4
I debated this myself but went with borg warner k04's. Just need few more odds and ends and then I can do the swap.
Im running my f21 franken turbo on my r56 n14 jcw with forged pistons loading 28psi or around 2bars, i blew one bcs of bad instalacion and since then its been great, franken send my a new one
I heard that the frankenturbos are kinda unreliable tho
I looked into the frankenturbos and all I could find were issues with reliability. For around the same price I decided to go with the ever-so-popular SRM K24’s. Can’t wait to get them, but it’s been a nightmare dealing with them, it’s been 3 months now and I still don’t have my turbos.
I’m still on stock k03 turbos at 225000 miles
Im at 218k, and still pulling hard with the stock K03 lol. German engineering
205k here. 15 psi she pulls like a champ
I was just looking into these due to my turbos leaking oil..
My buddies lasted 2 drift seasons before needing a rebuild, 1.8t single turbo running 22+psi
im still on stock boost too, im feeling taking the ko4 route
To me the idea of the F21 is not that bad, it's a nice upgrade over a RS4 K04 while keeping it simple. That said, I would never trade them for my BW RS4 K04s with RS6 compressors. They are similar in design and of course BW. I can't really comment on the reliability of the of the Franken turbos, but I'd suspect they are not quite as good as the BWs though there are certainly a good number on the road. You should know that there was a controversy not too long ago in which it was found that the compressor maps shown on the Franken turbo page are not real. As for you other options, there are plenty, but of course there is always the pay to play factor. There are plenty of RS6 K04 frame turbos out there with modified wheels producing well into the 500s among many other K24 etc. options. Keep in mind that the accepted HP max is considered to be around 600 HP with our rods. The F21s are probably good for the low 500s on a fairly aggressive tune.
I'd make you choice based on the following. If you think the F21s might be relatively lesser quality than other options, especially the BWs, the cost savings is null if they break. You are easily into $2k for a shop to replace them or a whole lot of work yourself most would like to do only once. Secondly, what's your tolerance and financial resources for running an engine 85-95% of its full capacity without major internal work? Third, how much does low end response mean to you? I'm guessing a lot based on your comments. If a 3- tune is enough for you to consider, then I think F21s are over kill given the likely loss of reliability compared to the BW K04s. There are easily 100k miles (on 3 different cars including 2 destroyed engines) on my hybrid RS4 K04s with probably 70 hours of redline track time on them over 14 years. I can certainly vouch for the quality of the BW turbos. :-)
The best option for an upgrade is and will always be Borg Warner K04s. They are plug and play, Tons of support, tons of people running them reliably, i’m sorry, but anyone who say F21 is better, frankly has no idea what they are talking about. I know this video is several years old, and at that time K04s were about $25-$2700. These days they can be Had for around $2000 and they simply are the most proven turbo for this platform. You can make a pretty amazing power numbers on them with all the supporting mods and even more with E 85 or better fuel. I have driven about 75 different B5 S4‘s, in every different state of tune and mod level. From k03/k04, F21, k24, STK- both 2.7 and 3.0, RS6, TTE550/780, TiAL 605/770, Turbo concepts, GT28, etc. I will always contend that the best builds are always either the really well-sorted k04 setup, or a fully built engine on big turbos. The cars with setups in between are either compromised, or risky I’ve been in this game for a very long time and there’s a reason I went with TTE 550. It’s a k04 on steroids - but also pricey. I think the TTE offerings are simply the best, But for most people it’s not the right answer because they are not really cost effective.
I️ had an F21 stage 3 B5 S4, lasted 30k miles on an aggressive J Fonz tune. This go around I️ ordered SRM RS6 K24 Ball Bearing turbos with Tial wastegates. I’d recommend SRM tbh
you didnt build the block?
was the 0-100 time slower??>
If i had to go back to smaller turbo it would be the TTE 550 or TTE600 USP sells them know.. Check them out.
I have an a6 with a 2.7t, my turbos are going and im personally going the turbo concepts dzx 271's
Srm k24+/rs6 turbos are wonderful on my car. Better than anything out their
wants to go stage 3, then sells it for a GTI??? come on
Thinking K04 would be more reliable🤔
xavier hunte getting a full stage 2 audi tt from my buddy with a blown franken turbo, would u recommend getting the turbo rebuilt or putting a ko4 on it? I want it to be reliable and quick
Yes they are bigger than ko4s and will make a but more power. But... they are Chinese housings and they arent going to last you as long as oem ko4s. If i were you id snag some bw ko4s and some e85 or even 91, but down 400whp all day long and they will last you a hell of a log longer. Plus they will spool fast just like ko3s maybe a fee 100 rpms later if that.
Sane Fuse, well considering bw has 7 turbo production plants world wide and 2 of them are in china, the chance of getting a "chinese" housing oem bw k03 or k04 is pretty high. But maybe u'll luck out and get them from Hungary, Mexico, Poland, or south korea.
Garrett gt25 or gt28 is a better choice than a hybrid ko4.
I’d go with the SRM ball bearing k24s.
I just bought some SRM K24 BB
KO3 is very reliable turbo if you don't push it beyond it's OEM specifications! If you take care of it can last very long, more that (400 000 Miles) here example:
ua-cam.com/video/Wk-isKUjWBQ/v-deo.html
Even if you don't take any care of it can run kinda "OK" if you are lucky. This is one hilarious link:
ua-cam.com/video/0jiM7z1fURE/v-deo.html
I’ve had wastegate failures on Fh4s and F21s.
people
who are suggesting that k24 is a better turbo. you are comparing apples to oranges....
You really need good coolers, don't ask me from where i know that... Go for Wagner and you are set to go :)
If anyone knows how to rebuild fraken turbos please hmu🙏🏼
That’s what I’m getting in a couple weeks lol
Im Uncle Drew Go with SRM
SRM K24's, more power and about the same price
Its all about Tial 605
I didnt see Any evidence at all of anything
I prefer k24's