# KO3 to KO4



## SiCk Gti1.8t (Apr 22, 2008)

I have a 2003 GTI with revo and a KO3 turbo in it. I just started working on this car but im still learning a lot about it. My first question is...would a KO4 be a good upgrade? if so would i have to switch my ecu or would i able to keep the revo i have now? Im not looking to make any crazy upgrades or anything but i think maybe a KO4 is an easy upgrade, no? Thank guys!!


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## Dub-Nub (Sep 27, 2005)

K04 is a really easy upgrade. All you do is switch the old with new and possible new turbo inlet pipe. The revo software will have to be changed to either a k04 file (not sure if revo has it), or use the BT software they have and tune it.
Everyone after me will tell you that K04 is a waste of money and i will tell you that aswell. You will spend $1000+ getting everything setup for it and you WILL want more trust me. If you want something that wont require rods talk to arnold at pagparts.com. He will be able to setup a kit for you that will be nice.


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## [email protected] (Jul 1, 2009)

*Re: KO3 to KO4 (SiCk Gti1.8t)*

The reason so many people bash the K04-001 is because it's a "baby" K04. With a 42/46 turbine and a K03s compressor it has substandard wheel sizes for the K04 series. It pre-dates the K03s by several years and was, for the most part, superseded by it.


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## SiCk Gti1.8t (Apr 22, 2008)

*Re: KO3 to KO4 (slappy_dunbar)*

well so whats the difference between the KO3 and this KO3 S ive been hearing about?


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## SiCk Gti1.8t (Apr 22, 2008)

*Re: KO3 to KO4 (SiCk Gti1.8t)*

i looked at the website u sent and their setup....looks good i just dont have that kind of money for that right now.


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## l88m22vette (Mar 2, 2006)

*Re: KO3 to KO4 (SiCk Gti1.8t)*


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## richardbachman (Jul 18, 2002)

*Re: KO3 to KO4 (l88m22vette)*


_Quote, originally posted by *l88m22vette* »_
















http://****************.com/smile/emthup.gif


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## SiCk Gti1.8t (Apr 22, 2008)

Hi, and u are..?!?


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## .iDubhXc. (Dec 2, 2007)

*Re: (SiCk Gti1.8t)*


_Quote, originally posted by *SiCk Gti1.8t* »_Hi, and u are..?!?

Thats Steven King.
But yeah. Ko4-001 is basically a ko3s. You won't notice any diffenece in performance really unless you get the file made for it. Then maybe roughly 10hp. Only way you'll notice a difference is with a ko4-2x series turbo. But that requires a lot more than just swapping turbos. In reality it is probably a better idea to save the money and go BT. It doesn't even have to be big, you could stick with a gt25/28 and be very happy with that.


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## SiCk Gti1.8t (Apr 22, 2008)

I guess i wanna avoid going BT at all cost...ill have to see other ways to improve performance before i can even talk about that. My goal is to only get around high or low 13s...


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## .iDubhXc. (Dec 2, 2007)

*Re: (SiCk Gti1.8t)*


_Quote, originally posted by *SiCk Gti1.8t* »_I guess i wanna avoid going BT at all cost...ill have to see other ways to improve performance before i can even talk about that. My goal is to only get around high or low 13s...

Pretty sure a k03s with all the bolt on a good tune and water/meth can get you into the high 13's no problem. http://****************.com/smile/emthup.gif


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## SiCk Gti1.8t (Apr 22, 2008)

eessh no water/meth...lol any other suggestion? u think stage 2 would do it?


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## Blackfin (Mar 10, 2006)

*Re: KO3 to KO4 (SiCk Gti1.8t)*


_Quote, originally posted by *SiCk Gti1.8t* »_well so whats the difference between the KO3 and this KO3 S ive been hearing about?

While the K03S (K03-052) is small, the K03 (K03-053) found on most pre-02 transverse 1.8Ts (01 Wolfsburg's being an exception) is a truly tiny turbo. Its compressor wheel has a 35mm inducer and a 50mm exducer with a tip height of ~3mm. It's also got a less efficient basic design with a 6/6 fin layout. 
The K03S improved the compressor side. It went to a 4/4 design, a 38mm inducer, a 51mm exducer and a 3.5mm tip height. However, the turbo remained unchanged on the exhaust side which is still very restrictive. It was used on the 180HP transverse applications from 2002 on and was also used on the 150HP Wolfsburg of 01 (the compressor housing is somewhat different in that application from the 02-on models...)
The K04-001 (which was never installed on a VAG product as far as I know) uses a larger exhaust turbine and more efficient wheel but actually uses a slightly smaller compressor wheel than the K03S though it's still a decent 4/4 design. The power obtained by going to a K04-001 generally comes from opening up flow on the exhaust side and even then, 20HP isn't out of the question.
If you're faced with a dead stock turbo and want a stock replacement, I think a K04-001 is a no-brainer. Its frame bolts directly in place and all the oil, water and exhaust hook-ups are identical. One thing you would have to look out for is that if you're replacing a K03-052 (K03S) with one, you'd have to get a silicone TIP because the K04's inlet is slightly smaller than the K03S and the mounting boss for the TIP retaining bolt isn't in the right place for the OE K03S TIP. As well, because of the better turbine (better flow, larger diameter), the K04 spools faster than the K03s so you might want a MBC in parallel with the N75 to help limit boost spikes. You might also want to look into a dedicated K04 tune though some of these may require adding TT225 injectors and MAF hardware (e.g. GIAC).
If your goal is OE fit and finish and your OE turbo is dead, seriously think about a K04-001. If you're looking to upgrade for the sake of upgrading, the K04 is probably not cost effective. Although "big turbos" are more expensive, require more hardware and tuning, do not use OE oil, water, intake or exhaust connections and so on, they do return a far better bang/buck ratio than the K04-001 does.


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## hootyburra (Feb 19, 2007)

*Re: KO3 to KO4 (Blackfin)*























DON'T DO IT


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## viasevenvai (May 8, 2006)

if your turbo is running fine, don't do it.
price for performance isn't worth it. Find another upgrade if you HAVE to do something.
My k03s was going out, so I got a stage III kit, I'm finding even that kit doesn't have enough power, so the k04 will be a waste of money for sure.


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## [email protected] (Jul 1, 2009)

*Re: KO3 to KO4 (SiCk Gti1.8t)*


_Quote, originally posted by *SiCk Gti1.8t* »_i...l i just dont have that kind of money for that right now.

You lost me. 
<$1000 Gets you BW K04-001 or a hybrid
<$500 Gets you a G-Pop Shop rebuild or a used K04-001


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## SiCk Gti1.8t (Apr 22, 2008)

yah i have that but if its just a waste of money i wont do it


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## jbutlertelecom (Aug 12, 2009)

or you can modify your current turbo with a specialized CHRA Hybrid (if you will) to avoid the problems accociated with going the k04-001 route... check out this link. They have CHRA's for the k03-005 or k03-029... just a thought
http://cgi.ebay.com/ebaymotors..._1165
This is something I am considering when my current turbo dies... 
Basically turns your current k03 into a k04 without all the headaches of things not aligning, bolts in the wrong place, custom TIP, etc...
_Modified by jbutlertelecom at 7:29 PM 9-18-2009_

_Modified by jbutlertelecom at 7:32 PM 9-18-2009_


_Modified by jbutlertelecom at 7:34 PM 9-18-2009_


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## [email protected] (Jul 1, 2009)

*Re: (jbutlertelecom)*

This is an upgrade kit for a longitudal engine. *It will not fit the OP's car.* 
Plus it's a lame upgrade. The specs are short of even a K04-001 (or, for that matter a K04-015, which, being longitudal-based, is the more appropriate point of comparison).
They are calling this a K03-29Sport. What it is, actually, is a facsimile of a K03-73, used in the 190bhp European-trim A4 Quattro. It is the longitudal cousin of the K03s. http://****************.com/smile/emthdown.gif


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## SiCk Gti1.8t (Apr 22, 2008)

so what do u suggest?


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## [email protected] (Jul 1, 2009)

*Re: (SiCk Gti1.8t)*


_Quote, originally posted by *SiCk Gti1.8t* »_so what do u suggest?



<$1000 Gets you BW K04-001 or a hybrid
<$500 Gets you a G-Pop Shop rebuild or a used K04-001[/QUOTE said:


>


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## jbutlertelecom (Aug 12, 2009)

*Re: (slappy_dunbar)*

Slappy, if you read the link then you will also note that they make other sizes AND other applications... I just posted the link for the logitudinal application so anyone can familiarize themselves with the concept... as I said, you can get just about ANY custom size compressor/turbine you want... it's just a suggestion for those of us that are NOT looking to make 350 whp...
get a grip and stop criticizing others for their choices and especially when trying to help others who don't want to spend 3000.00 on a BT setup or for that matter those of us who don't want the crazy HP....
Oh and also, the prices you quite do not include the other things that will be necessary for the complete install... what about the new TIP he will need? Add an extra 145-175.00
What about the custom ECU file he will need? Add another 300.00-600.00 
What about MAF requirements and Injectors? Add another 300-600.00
What about custom exhaust and such... The OP obviously doesn't want to spend more than 500-1000.00 so ALL the necessary upgrades have to be factored into the total cost, not just quoting the cost of the turbo....
From the website link:
"Additionally we offer many upgrades for other applications please email us with a specific application for more info"
"The K03-029/SP51R has the capability to muster 220hp/240tq (wheel) from a tuned and properly serviced 1.8t engine. If you desire more HP we offer additional upgrades for the K03 and K04 turbos. Currently our largest turbocharger for the VAG family is referred to as the K04 "Outlaw" capable of [email protected] [email protected] (wheel)"
_Modified by jbutlertelecom at 8:04 PM 9-18-2009_


_Modified by jbutlertelecom at 8:11 PM 9-18-2009_


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## [email protected] (Jul 1, 2009)

*Re: (jbutlertelecom)*


_Quote, originally posted by *jbutlertelecom* »_ They have CHRA's for the k03-005 or k03-029... just a thought


I wasn't getting after you or the help you're trying to provide. Just be mindful that the OP is probably not as familiarized as you are with BorgWarner's arcane numbering system. It's really easy to mis-type or transpose one number and you're suddenly dealing with a dramatically different product.








Just the same, though, as a competitor to this Ebay outfit, I see quite a few things in the listing that, well, cause me to doubt their capabilities.


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## dubinsincuwereindiapers (Jan 16, 2008)

*Re: (SiCk Gti1.8t)*


_Quote, originally posted by *SiCk Gti1.8t* »_so what do u suggest?

Dude.. Your car came with a ko3s.. Stay away from any other turbo starting with a K.. Unless your turbo blows of course.. 
The only "factory" turbo worth swapping in is the k04-023 from an audi TT225.. But you will need the exhaust mani, oil, coolant lines from the TT225 to make it work.. The K04-023 is capable of 250+ whp, or 270+ at the crank...
Save your cash unless you blow your turbo..


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## jbutlertelecom (Aug 12, 2009)

*Re: (slappy_dunbar)*

Well, I will let the OP sort out whether or not he trust's a seller with a 100% satisfaction rating... all the feedback looks legitimate enough to me... I have exchanged many emails with them and they seem polite and they respond quite promptly... I have a automatic (triptronic) so I can't get too crazy but hey, to each their own I guess...


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## dubinsincuwereindiapers (Jan 16, 2008)

*Re: (jbutlertelecom)*

The 100% satisfaction rating means nothing with a precision manufactured product like a turbo.. All that rating means in this case is that they found the seller to be responsive, and courteous, and that the turbo arrived promptly and well boxed... The purchaser see his shiny new turbo and is happy.. Then leaves a positive feedback. When the turbo fails a couple months later the buyer cannot go back and edit their feedback....... 
In conclusion the 100% positive feedback means nothing........


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## [email protected] (Jul 1, 2009)

*Re: (jbutlertelecom)*


_Quote, originally posted by *jbutlertelecom* »_Well, I will let the OP sort out whether or not he trust's a seller with a 100% satisfaction rating... all the feedback looks legitimate enough to me... I have exchanged many emails with them and they seem polite and they respond quite promptly... I have a automatic (triptronic) so I can't get too crazy but hey, to each their own I guess...

I think I was a bit too quick to jump on them. The broken English in the Ebay listing turned me off. However, after giving it a bit of research, I'm pretty sure these guys are loosely related to Borg Warner's Polish operations. Maybe they spun off from their day jobs there.... I don't know. But it's a good bet they are better trained than your average aftermarket vendors. They just need to bone up on their communications skills maybe.
One thing I have heard is that they turn around a good product. And I say this not just because of the Ebay feedback. I have seen postings from people who have dealt with them and the general tone of what they said was positive. http://****************.com/smile/emthup.gif


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## SiCk Gti1.8t (Apr 22, 2008)

how much do ko4-023 usually go for? where is the best place to get it?


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## [email protected] (Jul 1, 2009)

*Re: (SiCk Gti1.8t)*

http://forums.vwvortex.com/zerothread?id=4506444


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## Rileynauss (Mar 11, 2021)

.iDubhXc. said:


> *Re: (SiCk Gti1.8t)*
> 
> 
> _Quote, originally posted by *SiCk Gti1.8t* »_Hi, and u are..?!?
> ...


Will a ko3s compressor wheel work in a ko4


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## Vegeta Gti (Feb 13, 2003)

Don't do it first post

Sent from my SM-N975U using Tapatalk


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## BoostedHatchback (Jun 21, 2020)

Make it work. If it dosen't fit, get a bigger hammer.


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## Vegeta Gti (Feb 13, 2003)

Excessive space in the compressor housing will cause massive compressor surge and it will eat itself and throw all the parts into your engine. 

Worst case scenario. 


Best case, you lose some power due to velocity loss. Due to the spacee around the wheel from the larger compressor housing. 

Similar goes for exhaust housing. 

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