Technical Understanding of the IHI (Why does my Power FALL off?)

[Dybz]

Originally Posted by SkullV

I've seen a couple IHI/K03 housings with K04 internals locally. Done to skirt the rules on stock turbo for SCCA class.

lol... on GTIs?

[SkullV]

Originally Posted by Dybz

lol... on GTIs?

Yeah, full race prepped GTIs.

[daz_pd]

Originally Posted by Dybz

not worth spending time to make a hybrid k03... just go k04.

surely cheaper to change some internals than buy a whole new turbo kit?

[Dybz]

Originally Posted by daz_pd

surely cheaper to change some internals than buy a whole new turbo kit?

probably not once you start taking into account labor costs required to machine it.

[Dybz]

Originally Posted by SkullV

Yeah, full race prepped GTIs.

PM me a contact? might be interested in how they went about doing it and what sort of gains they see.

[Outkasted24]

great read and now it's all a little more clear, Thanks!

[excelevant]

Originally Posted by Dybz

PM me a contact? might be interested in how they went about doing it and what sort of gains they see.

+1 for gains/info

[Bcastine]

Came across this awful scan of an IHI RHF5 compressor map:



Crunching the numbers I believe it to be accurate, and it tells the story.

Earlier in the post it was discussed as to the effect of turbine A/R on a compressor map. It should be noted that turbine A/R does not effect the map, the map simply illustrates what the compressor side can do. The turbine A/R can just shift where in the map you are. Anyways....

Decoding the map at stockish boost levels, to make it easy 1 bar of boost, our engine assuming 90% volumetric eff. will flow about 11.5 cubic meters/min into the turbine @ 6500rpm. So draw a horizontal line from 2.0 and intersect it with a vertical line from 11.5 and you can see we are beginning to loose efficiency, but at least still in the map and probably not blowing all that much heat. This is assuming the turbine A/R is adequately sized as to not choke the engine, which we know its not, well at least with the stock DP and its effect on flow through the turbine. So in the real world we are somewhere to the left in the map at a lower pressure.

The map shows us hitting Peak boost 1 bar @ 1800rpm, well it at least states the compressor is capable of such a feat. Look at where the map begins at 2.0PR on the horizontal, draw a vertical line down and we are at approx 3 cubic meters/min. Using a compressor map calculator, our engine outputs 3 cubic meters/min of flow at 1800rpm.

To see the effect of a stage 1 or 2 tune, what are they 18psi? anyways, (18+14.7)/14.7= 2.22 pressure ratio. At 18psi our engine flows 13 cubic meters/min @ 6500rpm . Draw the intersecting lines once again and you will see we are off the map. Regardless of the turbine a/r, this compressor can not support 18psi on our engine, well at 6500 rpms anyways.

Lets look at our midrange though at this boost level, at 5Krpm we are flowing 10 m3/min, and at a 2.22 PR we are in a pretty descent eff. range for this compressor, actually at about all it should be tasked to do(in theory 247chp). Digging deeper we can see that at a 2.2 pressure ratio the compressor is all done at 12 m3/min. That is 6000 rpm with our engine. So if the turbine a/r is not the limiting factor, this compressor can only hold 18psi till 6K rpm with our engine.

In short our turbo is to small LOL, I know captain obvious... If a stage 2 car can hold 18psi till 6K rpm there is nothing even a larger turbine a/r could do to help. But if not, a larger turbine a/r, giving up rpms at spool up would help hold boost on the top end. On a side note the theoretical max output of our compressor is 297 CHP according to the above map(12 m3/min = 29.7 lb/min and rule of thumb lb/min x 10 = crank HP).

Stage 2 proves that adding a down pipe has a similar effect to enlarging the turbine a/r as it extends desired boost into later rpms.

Hope this makes sense, I find it kinda fun to play around with compressor maps, its unfortunate that turbine a/r isn't as easy to figure/plot out.

Compressor flow map calculator:
http://lovehorsepower.com/joomla/ind...tuff&Itemid=49

[Tg2098]

Sorry if this isn't the right place but is the k04 a direct swap for the IHI compressor? Is all you the the compressor and manifold? I'm starting to lean more towards K04 than just a tune if that's the case

[visceralsoup]

I didnt go through all the pages to check, but would you say the k04 would have a similar map to the f23 turbo? It has the same housing as the k04.