why, the age old and track proven 16/24's hybrid's with tune and suporting mods of course

 

You bring up some good points. Boost (torque) that comes one too suddenly and without the ability to smoothly modulate the onset is the enemy of low lap times.

Since I assume the boost limit on 92 octane pump gas is in the 1.1 to 1.3 bar range for straight K24s and K16 billets it would be nice to see some dyno graphs with similar supporting mods and peak boost pressures to get a better idea of how the two turbos might feel on the track. The stock K24s must also operate at a lower P/R vs the K16 billet with the small turbine side

 

My comment above was tongue-in-cheek (that's why the smiley was there - sorry if it came across otherwise). A digital throttle is def a negative anywhere - even in a straight line.

That said, there are plenty of K16 based setups that make decent power w/o becoming undriveable due to all torque coming in at 3000 and plenty of K24 based setups that make an early 930 seem lag-free.

After driving both NA (GT3) and various turbos both on and off track, I have all but decided to go with K16s in the first iteration of my street/track car. Who knows. Maybe I'll be calling you for K24s in a years time (though I have to admit - I have already been oogling A28s for the next iteration :-p ).

 

stevemfr what configuration are you going to use for your street/track 996TT?

 

Just call Sam! He's as good as it gets in my book! I'm getting set up with a clutch kit gauged to my GIAC tune designed for k16billets as you and I are after the same goal on power etc. I'm going clutch first then turbos.
He will help you understand the options without pressure. I have his info if you need it PM me - most in here do lol.

 

IMHO, for roadcourse use, you generally want a turbo(s) that are slightly oversized compared to a 'street/strip-use' turbo, and not undersized, or the commonly compromised hybrids...want a turbo that flows efficiently for many minutes/hours straight without excessive heat build-up.. hybrids are great for street/1mile/strip/etc. but often the hot-sides are undersized(which gives greater spool) but retain excessive EGT's....VGT turbo are the 'compromise' solution but work in a relatively narrow power-band..
Likewise a street/strip IC/intercooler isn't necessarily a good roadcourse IC, large core(great short-term heat-retention) vs. a truly efficient(heat shedding) core...
A good tuner should be able to guide you...
Cheers,

 

Cheers Brock.
I will also add that this all depends on some important factors...The car, driver, goals and budget. One thing may work for one person and not for another and is not always general. There's almost 31 flavors and 32 prices these days as for turbo options. I think the best thing to do is map it all out and deal with someone who you're comfortable with to help get you there.

 

I went form RUF K24/26s to K16/997GT2RS turbos. I like the K16s better for track use. Good programming will determine usability of the turbos. Mine feel very much like an NA car, very smooth gradual build up of torque without any boost peaks...

 

Hello,

Can you explain what modifications were performed to make an "K16/997GT2RS" turbo?

Thanks,
JR

 

K16 housing is modified to accept a 997GT2RS compressor wheel. Turbine inlet housing is ported and the compressor side housing is zero clearenced to the wheel. The compressor inlet is much larger than on a K16 or 24 so a reducer must be used to connect the turbo inlet pipes. Turbos pull strong without let up all the way to 7200rpm.

[url=https://flic.kr/p/pA7m7U]

 

i've never understood the difference btw the 16/24 "zero clearance" and the older? hybrids i have, as they are excellent and also spool nearly instantaneously and pull strongly up to 7200 without flat spots either.

i guess i'd have to drive a car with those to understand exactly how they are different ( if al all ) in their delivery of boost etc. and if they actually make the car quicker or whatever it is that makes them "better", than 16/24's with the older housing?

 

I agree that tuning plays a HUGE roll, but you also need to factor in with a 1 bar wastegate spring (which most upgraded turbo users have), there's very little programming can do below 1 bar to control boost. If you have a slow second gear turn where the car is coming through at 4000+ rpm, there's very little programming is going to be able to do to eliminate some kind of surge in boost when getting back on the gas.

 

That's where the right foot takes over the programming. Most drivers don't understand the concept of gradually increasing throttle as more grip becomes available once lateral g's decrease. Gradually squeezing the throttle on exit uses as much power as is needed (or better yet as can be contained by the car and the driver working together).

But that should in theory work as well on a big turbo as a small one considering that you are already in the efficiency range of even the bigger turbo. You aren't foot to floor max power mid corner anyways (assuming not bogging). Feasibly, if you can keep revs in a 4500 range, and begin throttle application early it nullifies the throttle input advantage of the smaller turbo from apex to near trackout. The car will only put down so much power (not near all of it)

I can only think that in super slow corners, like hairpins or sharp off camber turns where you will inevitably leave the optimum rev range, where the smaller turbo would be advantageous. That and the very low end straight line accleration where the smaller turbos should pull harder. But my question remains which will be faster to 60-130 or 60-165 given same car, same power level, bigger turbo or smaller one.

The thing I've found challenging with the big turbo is in fact modulation though, as 2nd gear is useless (too much torque/gear), taking slow, low rev turns in third means you have to plant the foot well early to give that boost time to kick in, but when it does it comes in like a hammer. I'm thinking that will be easier to manage with a smaller turbo as you won't have to anticipate as much.

 

Who built the turbos for you?

 

pretty sure those are umw's but im still cant figger out the difference lol