Kiko

Oh KEEVIIIINNNN!!! (calling) LOL

Oak

They may spool slightly quicker but run out of breath quickly. I have the FVD hybird turbos k26/24 and there is much more mid-top range torque. More sustained torque overall. What ever difference in lag is not an issue. Been there done that.

Woodster

I'm with Oak on this one, these cars build good torque down low (thanks to Varioram),
I do not believe the lag is noticable or an issue! There are other types of turbo cars where
it is more of an issue, the 996TT is not one of them.

Marty K.

Kevin

The GT1's or Stage 1 do not run out of air when compared to "STOCK" X50 or GT2 turbochargers. OAK you show me a set of K24/26 that you have that will beat my Stage 4's or Stage 5's.. and they are still K16 based.. Sharkster's shootout car turned low 11's with them and I don't know of any K24/26's that will do that.. I seen 28PSI in Sharkster's car..

GT1's will deliver the goods, Stage 2 will surpass Stock K24's.. Jean has a video that he will post.

Kiko

Kevin:

As you know I'm still looking for a used set of headers to send you but I was here thinking and... doesn't the ceramic coating increase the turbo's thermal stress? If the heat is not radiated through the header it will increase systems efficiency (Carnot's cycle) but in the real world it will increase the turbos operating temperature a lot, or not?

Woodster

Jean,
Can you help shed light on this complex and ongoing discussion ??
K-24 madness: how about your thoughts ??
Steven at I/A: how about your thoughts ??

maxwell

Yah, I would love some clarification as well. I have Stephen's stage II kit on my car with stock k16's and it puts down 440hp and 447tq to the wheels. I would love to get the car to about 500/500. Other than going with a stage IV/kkk24 kit like evo/IA sell, what configuration of the kkk16 will produce about 500/500?

What are the stage I,II turbos? Are they based on the kkk16?

Oak

Kevin, I agree compared to stock. But from my personal experience the K16 hybrids would become heat soaked much sooner and start to loose their efficiency very quickly. Very noticeable if you run them at any length of time like at the track, or canyons or even in hotter temps. Sure, just cruising around at street speed and occaisional punching the trottle the hybrids will spool quickly and out pull stock turbos.

Red9

This thread is to relevent to dissappear. What are some of the answers to the questions posed?

Woodster

Yes heat does make a difference, I was at Brainerd Intl speedway on July 5th this year,
993tt with ported headers, 100 cell cats, Kevins K-16 base stage 2 Z/C, ceramic coated imp,
Protomotive "540" software, etc,
I got out accerlated by a stock Viper GTS (450 H.P.) on the 1 mile long straight,
I am not blaming this on the turbos but Kevin promised me "tire shredding performance"
I do not believe that at the STAGE 2 LEVEL AND BELOW TURBOS will give me the
"tire shredding performance". Just my opinion, but that is what I experienced. BTW, the
other 993TT at the track that day (w/K24's could also pull me on the straights...!)

Jean

I am not at all a turbo expert and probably I should not be giving my opinion here but I feel there are a lot of questions that people have that are in fact much simpler to answer than what they appear to be.
1- It is subjective to assess what turbo is better than the other, it is about what turbo is the correct size for your needs, obviously you need to know what your needs are, and be very specific with the builder.
2- A great turbo with unmatched programming, intercooler, exhaust or intake will underperform vs. a stock turbo with matching components and programming. Too large of an intercooler for the turbo and you might increase lag, too much exhaust restriction for the turbine size used will increase lag and heat, too small of an intercooler will not let the turbo boost as far as it should, etc..
3- Whether a turbo can give you 500 or 800 hp on a certain engine is a very simple calculation, how does it deliver that hp is another story. Too much boost dialled on a small turbo or using an inapprorpiate intercooler, will not generate increased HP, it might "spike" on a dyno but that's about it, some people are happy with bragging rights, which is fine too. The turbo will just flow hot air, increase the temperature, and drive the knock sensors to retard timing, increase the boost, you will see another spike and then the increased heat will again pull the timing, until your performance gets reduced by 200hp because you are boosting too much on the wrong turbos or inefficent I/C.
4- A hybrid turbo uses different sizes from what a stock turbo has, it mixes and matches compressor (cold side) sizes and turbine sizes (hot side). There is a lot more involved, such as the housing used, the shaft, backplates, bearings, clearances etc..

Does Kevin's hybrid deliver better than a K24? There is no straight answer to that, it depends how well it is mapped and matched to the rest of the engine, it depends on what type of performance you are looking for etc..

A 996 and a 993 will not perform similarily with the same hybrids, the engines have different characteristics and different powerbands and efficiencies.

Marty, I have seen stage 2 ZC hybrids have tire shredding performance on a 996TT, but I bought those turbos with their exhaust, intercooler, modified headers, LWF/PP/ clutch assembly and matching ECU at once. I also bought stage 5 ZC turbos but bolted them on an ex-Gemballa engine, Gemballa exhaust, top mounted Gemballa I/C, modified MAF and intake etc.. and guess what, the stage 2ZC beat it. Same turbo supplier, same ECU supplier.

A K24 compressor and K16 turbine will spool faster than a stock K24, meaning faster boost response, less lag, eventhough the smaller turbine will increase back pressure. The K16 turbine will reach a point where it will be spinning too fast and will not flow anymore where the K24 will continue doing so. If you reduce the clearances to the housing (ZC), you increase the efficiency of the turbo as it will need to spin less to flow more air (no air is being wasted).. A ZC hybrid turbo will therefore outperform a normal hybrid, the combination of smaller turbine, large compressor and high efficiency is what makes them great and deliver across the powerband. Check out the thread on the 993TT board with the different dynos.

If your car was properly balanced and calibrated, I doubt a car with STOCK K24s would outperform you, if he did, it means something was not running in sync in your engine. A modded K24 is a different story.

A test on modded 996TTs performed by a German magazine showed that K24 based turbos had slightly better performance than hybrids in acceleration runs to 125mph, however, that does not mean that the Hybrid based cars would not have beaten the K24 based on a roilling start in 2nd gear, from 50-90mph or from a red light to another.

If what you need is track performance, the stage 2ZC is probably not your best bet, as the smaller turbine will generate heat at continuously high RPMs, further stages are better suited, but for the street, they are hard to beat.

Any combination and mix and match of turbos, hardware, different tuners etc.. will not yield anywhere close to one epxerienced tuner doing 100% of the work and tuning accordingly on his dyno while testing how every new component is impacting performance. More importantly, the best turbos, best intercooler, best exhaust, best intake and best ECU program, will run like sh$t unless they work well together (turbos too small for the I/C, intake great above 5k RPMs while turbos are dying at those levels, etc..)
Get one tuner to do it all.
If have given any wrong information please feel free to correct me.

wross996tt

Jean, Very, very nice write-up. Thank you! I am definately not an expert, but am interested in possibly upgrading my turbos. At this point it seems "we" (the perhaps less knowledgable) must rely on a good tuner to pick the right combo? This scares me as I have no way of knowing until after (and a dyno).

Jean

wross996TT
Thanks. If I may suggest that you do some research on the net, read some books, have long chats with Kevin (sorry Kevin ) and give it a try to learn about turbosystems, it is very interesting, and a nice way to relax and do some numbers for fun. Try to make your own choices and then talk to your tuner or turbo supplier, but at least you will understand what he suggests to you and why.

Woodster

Thanks Jean,
My two years of daily research have produced similar conclusions to what you have laid out:
for most of us, Unless you have the do it yourself know how and technical abilities of a Tom
Hogan (K-24 madness), Geoffrey, Jean, etc., A complete package from a "good tuner" will
work very, very well.
cheers it will be fun choosing and then comparing notes next Spring/Summer !
marty K

K24madness

For purposes of this discussion lets start by looking at the turbo in two different parts.

1st is the hot side. Turbine
2nd is the cold side. Compressor

If we assume that two different turbos use the same compressor wheel but different hot side housings, the one with the smaller turbine/AR ratio (k16) will spool faster than one with a larger turbine A/R ratio K24. The difference will be approx 500 RPM's. After 4,500 RPM's both will be fully spooled. From 4,500 on up to about 5,500 they would be pretty much even. From 5,500 the larger K24 turbine A/R ratio would really start to pull away from the smaller K16 based turbo. The difference is quite dramatic.

Now those that compair stage 2 K16's to stock K24's need to consider that if they put the same stage2 compressor into a K24 turbo the above would still apply. Zero clearance or not.

The moral of the story is if you are willing to delay power for 500 RPM's you will be rewarded with HUGE gains in power on the top end.

FWIW you can also reduce lag in many other ways. My current hybrid 24's (not Kevins) spool faster than stock K16's do.

PM me with any questions you may have. I don't troll this board often.

Tom