NefMoto

Im currently driving a 180 FWD Audi TT, and the turbo is starting to leak some oil when building bigger boost, its not smoking constantly or on idle, just when doing a small pull, there is a puff of stinking white/blue-ish smoke.

Only thing I know is the fact that it has a K03(non s), not sure what model exactly. Our marketplace is very limited when it comes to turbos for these cars, there is a K04 and a K03s. Everyone will say go for K04, and I'd love too, but does someone have a flow comparison, or some graphs with proof how much better the k04 is over the k03s. 

Have you checked their compressor maps?

I couldnt find a good K03s compressor map, but I did found a K03 vs K04. And it hold boost so much better over the rev range. I'd love to have a stable 1.5 bar (21 psi).

(https://www.golfmkv.com/forums/index.php?attachments/k03ko4overlay-jpg.40663/)

I did read that the compressors on the two are very simular, but the K04 as a bigger intake port. And the k03s could only get you ~10bhp more.

Just wondering the opnions and experiences on the forum.

Ford 1.5 bsr flat you need GT28RS or equivalent.

Also you have to change fuel system, intercooler and exhaust for a K04.
Another thing is the compression ratio stock CR is too high even for K04.

Hmm I do have a upgraded ic and exhaust, for ghe fuel system, are BAM injectors not enough? I did see allot going drom k03 to k04 with succes. But your advise would be a k03s i assume?

Fuel pump should be upgraded, injectors changed (IDK why you would want to use BAM ones, EV14 are much better).
And last but not least, you will never make the same power as a BAM engine because of too high compression ratio and small port head.
K04 boost profile is something like 1.3-1.4 in middle and tapering down on top iirc to 1.2 bar. That's with the turbo maxed out on a BAM engine. Obviously you might need higher boost to get the same airflow.

I honestly dont want to upgrade the fuel pump and/or injectors if I dont have too. Its still my daily and I am not looking forward to burning a hole in my pocket for gas(its €2,60 per liter for us).

If I can have 1.3-1.5 bar stable on my current setup, with the possibility for more in the future that would be awesome.

You will burn the hole in your pocket anyway

K04-023 is a very punchy turbo i've driven a mapped otherwise stock BAM before and it feels much stronger than a maxxed out K03s.

Though upgrading the K03 over a K03s to me is very much worth it.

Im reading more and more, and I was considering the K04-023 at first, but I am leaning more and more to a k03s.. Pure on the fact that its a daily, I barely punch the gas on the road anyways, and I am not looking forward to buy 10 different mods just to run a K04.. I rather buy a TT with BAM engine

Just buy chinese k03/04 hybrid with 42mm inducer. Theyre fine

Doesnt matter how much bar of boost youve got.

replacing a k03 with yet another k03 makes zero sense to me. compression limits notwithstanding, there are almost no drawbacks to going to k04s imo


you don't need those to run a k04, and you can always do those incrementally.

I meant from k03 to k03s is a small improvement. K03’s supposedly only get you to 190-200 bhp, and the k03s from 210-255 bhp.

Dude, if you don't want to do anything, just buy a CHRA only for your current turbo, swap the CHRA, and job done. They cost peanuts for original BW CHRA.
You don't need to change anything.

There is near to zero benefit going K04 or K03S without upgrading injectors and fuel pump.

So either go with what you have now, or upgrade the fuel system and go for bigger turbo.

I think you are right. I currently have a K03-035, and they sell a brand new K03-052 cartridge for only 180 euro.. all OE. Since the k03 and k03s have same dimensions, it should be a direct fit, and it could even get me a little bit more power.

Found the info here; https://www.audi-sport.net/xf/threads/the-facts-about-the-k03-turbo.5970/ (https://www.audi-sport.net/xf/threads/the-facts-about-the-k03-turbo.5970/)

A little off topic but I was confused for why JE sells 9.5:1 stroker pistons off the shelf and currently readily available, but I realized they are probably made exclusively for race fuel(100octane+) or e85.

This forum is a lot more informative about actual tuning experience when it comes to choosing a CR for a BT 1.8t, which seems to always be 8.5:1 for 93 octane or 9:1+ or higher with race fuel, E85 or W/M. I was under the impression that you can use 9.5:1 on pump gas(93), no water methanol at that boost level but I guess I was wrong. 8.5:1 seems to be the best choice for high boost/knock Safety without sacrificing a noticeable difference in low end torque.

Edit: Not sure if below is true. Id like someone to verify

Then there's bad turbo sizing to match expected airflow which will create bottle necks from excessive flow from cam and throttle body upgrades. This then causes a back up and create high EGT's and back pressure in smaller turbine housings if not choosen correctly. It seems like, in most cases, high EGT's can be bypassed using E85 or methanol so you can use whatever set up you want.

People are saying it's harder to tune(9.5:1) but some say it's possible to make high(400+)HP  on "pump" fuel but I think octane is rated differently in Europe than the US for some of the guys that make those claims.

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k04 is the best option.......very good spool and keep 1.5 bar to the red line with all needed components, injectors, maf and a good cooling. Fuel pump not need to be change if it is in good conditions. If you works with 9.5:1 engine you will have more retards but at 1.4-1.5 bar boost will be ok.....BUT>>>>>>>>>>>>>>>>K04 will btoken the RODS after some boost if the torques is agresive!

You will not feel any low end torque difference until down to 7.0:1 or so. This low end torque BS is a myth being continuously regurgitated on forums for no reason.
8.5:1 is not for high boost. 8.5:1 on standard fuel without any octane boosting is good maybe for 1.7-1.8 bar boost on large port head. After that you need to go lower CR or higher octane or you are going to have EGT problems. The cars with 9.5:1 CR run like 0.6-0.7 bar boost from factory. This is why they also have this CR. If you care only about power, even on a K03S you will make more power on 8.5:1 CR than on 9.5:1. But the fuel efficiency will suffer.

The reason for these astronomically high compression ratios are fuel efficiency requirements. It has nothing to do with "low end torque".

It was a common occurrence for me back in the past that people would ask me to tune their self assembled shit with 9.0:1 or higher CR on 98 RON, and made a pikachu face every time I said that it's a waste of time.
Was ages ago then, after a while I realized that there's never any point to tune anything you didn't build yourself, and this problem went away, along with a host of other issues.

Its funny when someone builds a 12.5:1 turbo setup thinking they are going to make SO much more than a low compression setup. Every time the dyno shows much less difference than expected and then octane requirements make them not pump gas friendly.

I just sold my JE 9.5:1 pistons after realizing that and getting feedback from guys on this forum. The stock Evo 8-9 comes with I think 8.8:1 with a bottom end that can hold up to 450wtq. So 8.5 it is for my G25-660 build. I was gonna go with the EFR7670 but full race discontinued their twinscroll manifold!!! I'm gonna have Race3 make me their V-Band Ramhorn Manifold and try out the G25-660 to see if I can hit 500whp with 2008cc, cat3658 cams, SEM intake manifold, 75mm throttle body, built AEB head, ID1050x and 93 pump gas from the US. But I'd be happy with 450whp if it can't and do W/M later on...

Then there's the dynamic compression ratio calculation with larger cams that will drop ACTUAL compression ratio. AND then turbine and A/R sizing to prevent high EGTs So just trying to make it easier for my tuner when the time comes and will eventually make my own tune when I figure out how to tune myself. Hopefully the G25 turbine isnt too small for all the flow that I'm expecting with my setup.

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The more torque you want to make at a given displacement the higher the pressure in the cylinder is and the lower the compression ratio needs to be.

For 450whp on pump fuel on 1.8T I would use 8.0:1 CR...

I personally don't think 8:1 is necessary plus with the catcams it will lower actual compression ratio even further. Guys are making 500whp+ with 8.5:1+ on pump gas but if it does manage to clear the 500whp mark then Ill be looking into a W/M system either way.

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You can think all you want. I know.
Without octane boosting it will be. It sounds like you never in your life built or ran anything on pump gas that made any significant hp/liter.
Also, on a built engine or a hobby car there is no reason ever to have a compression ratio that is going to limit your power output and raise your EGT, as the only thing that will suffer with a lower CR is fuel efficiency, and at higher CR everything BUT fuel efficiency suffers. Reliability, thermals, power output etc.

I don't know why you keep on repeating this, because this is blatantly false. All things being equal to make a certain torque you need a certain cylinder charge.
This cylinder charge will be compressed based on the compression ratio. If you have leaky cams with overlap, it just means you need more flow to get the same cylinder charge.
In the end you still have to get and compress the same amount of charge into the cylinder. And what cams you have does not matter. Cams do not affect this whatsoever. Engine breathing will determine how much charge pressure you need to run to get a certain cylinder charge, but not how much torque it's going to make with the same cylinder charge being compressed after the valves are shut.
If at a given cylinder charge you are knock limited, you will make more power with a lower CR and the same cylinder charge, and of course there is less heat.

What does affect CR is if someone cuts a chunk out of the combustion chamber, after which the volume of the cylinder has to be measured using liquid to again know the true compression ratio.
If material is removed from the cylinder head, then the 8.5:1 piston can become 7.8:1 really quickly.

Btw, it's a really shitty idea to have overlap on a turbo engine higher in the rev range when backpressure starts being a factor. It completely destroys power output.

Nothing to say to such internet gods.

My recommendation is to curb your enthusiasm until you have actually achieved something.
I don't need to look at what "guys are making" because I have my own hands on experience.
And there's a huge difference between a short dyno pull and sustained EGT.

I take your word for what your saying since you claim to have the experience. I won't lie, as of right now I don't. And yea I haven't built my car yet. I'm just doing research and going off of what I've read on forums. So far I can see that everyone has their own builds and if I commented on someone else's build on audizine they would call me a troll, which one guy did right after I helped a guy get his car running. So I'm definitely open to more opinions about CR.

One guy from Audizine referenced one of the tuners on here about why you won't notice a difference in low end torque from 9.5 to 8.5, so that's all I wanted to hear because alot of mixed info out there.

That made me sell my pistons and now I'm set on getting either 8-8.5:1.

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I'm not sure why I'm thinking the G25 housing is too small because the 2.7 guys are using it as well as other platforms with 4+ cylinders. EGTs will definitely be higher and get hotter sooner but the speed at which it increases and the temp probably isn't as much as I might be thinking.

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