Audi R4R

Hey Mike,

Sorry I'm not on the forums all the time, but I was checking on my previous threads and you said that the T-28 tops out with the 2.0L conversion??? I just have a hard time believing that since I drove a 2.0L conversion with a T-28 turbo in my area that was extensively tuned.

It drove really amazingly! I was impressed. We took it 7200rpm and it seems to fit the car perfectly! It was running a SDS EMS along with upgraded internals. It seemed to give my car a good run for its money. I haven't driven another T-28 turbo on a 1.8T so I have nothing to compare it with.

But now having experienced the 2.0L conversion, I am dissappinted with the minimal increase in low-end power. True, some is better than none; but not for that kind of price tag. Why didn't you decide to increase the displacement a little more and modify the bore along with the stroke? Just curious!

Cheers,
Steve

xr4tic

It may not be as efficient in the upper RPMs as compared to a larger turbo though. I thought the T28 was bigger than the GT25 that APR used.

For a 2.0, the bore is increased. The 1.8 is 81mm, stock 2.0 is 82.5mm, mine is 83mm, and I think Mike is running 83.5, which is about the limit for a turbo application.

The main increase is the crank from 86.4mm to 92.8mm The diesel crank is 95.5mm, and 99mm cranks are available, although I'm not sure what the limits are in the block.

Audi2ptzero

I have seen the dyno plot of a 2 liter T28 running 17-19psi and it has a hp peak at 5400-5500 rpms. The only way to increase that hp peak upward more is to run a lower boost so that the turbo does not hit full spool till later on.

SMOKINA4TURBO

Seems like those maps would be pretty vital in finding the proper efficient turbo for your application.

You should call up a proffessional shop that has experience with turbo's for your application and has the actual technical specs.

Audi2ptzero

as john states I have a 83.5mm bore which is the limit on the 1.8t block and a vw forged 2 liter crank. You have to understand that a turbo is going to hit full spool at some point, a 1.8t might be able to run 21-23psi and hit that point at 7k rpms while a 2 liter which is 200cc larger and will pump out more exhaust gas will hit the max spool much sooner. I can give you an example of what I am talking about

A 1.8t K04 running 27psi hits full spool well before redline, I run a K04 at 1 bar of boost and can hit the max spool even sooner then the car running 27psi. So what I am really saying is that the cfm that the turbo can max out at will be much sooner on a larger motor. I have a dyno pull of another T28 2 liter that showed that the T28 peaked for hp right around 5500 rpms running around 17-19 psi.

BTW using a larger motor will also need a well matched turbo to max out hp at the right point.

xr4tic

because it makes no f'in sense.

You can't increase top end HP by decreasing low-end boost.

I'd say 18-19psi of boost on a 2.0 is the max you can make on 440 injectors. Plus you start to run into fuel issues with the stock pump.

In other words, you can't say a turbo is too small, based solely on some dyno plot you saw.

Audi2ptzero

it at a much lower boost level.

Audi2ptzero

and was not even close to running those out.

SMOKINA4TURBO

You some god or whatt?Can I have whatever pills you take?

Yippers®

I've seen that posted many times but I thought the T28 flows in the upper 400 cfm and the APR spec'd GT25 in the mid 500's. To be fair I sure haven't seen any flow charts comparing them tho.