K16 v K24 the "lag" issue
 

With the 996tt forum begining to look like an offshoot of 6speed with lots of talk and little substance I thought I would treat 993tters with some data I found.

This data comes from Flat 6 magazine, the cars are 993tt stock 408PS and 993ttS Euro spec which means K24 and 450PS the gearing is the same for both cars, the temperatures were similar for all the tests

The time between when one hits the throttle pedal and when the turbos spool up and start boosting is one element of "lag" which is never tested for however the other element is using WOT from low revs and timing how long the car takes to accelerate between two times giving us a picture of the boost curve of the turbos.

I have extrapolated approximate rpm's from the before and after speeds to give the following numbers:
K16 K24
3rd gear 3650rpm - 5470rpm 2.8s 3.2s
4th gear 2820rpm-4235rpm 4.1s 4.3s
5th gear 2380rpm-3570rpm 6.2s 6.6s
6th gear 1760rpm-2640rpm 8.6s 10.4s

Just because I have the numbers here are the timings for the same speed increment for the K16 420hp 996tt versus the X50 K24 450hp 996tt

K16 K24
3rd gear 3.77s 3.80s
4th gear 4.4s 5.0s
5th gear 5.48s 6.4s
6th gear 7.2s 9.0s

What we need now is some hard data from a K16/24 hybrid car - Phelix :) ?

TB,
This is really interesting subject at least for me.
I suffer from K24 Lag, and searching for additional info.

Hope to see the hot discussions and diverse opinions on our forum too, but more specific than on 996TT forum.

I have real world experience with this. My brother (996TT X50) and I did some 3-4th gear pulls on the highway. Both cars stock (I have muff bypasses). Each time I pulled him from the beginning and we ran out of room before he could get to his higher horsepower. We were on our way to drop off his car for a upsolute flash and exhaust (probably good for nearly 100hp). Needless to say, the next run left me in his dust from the start. His car hits boost like a rocketship now-very intoxicating.

what is the size differential for the K16 vs K24 turbine housings?

K24's really benefit from muffler bypasses and a ECU upgrade

Very interesting thread. Lag is always seen as evil in turbo circles :) Measuring it can be tricky business, especially when things such different engine setups are concerned...

The way TB is looking at it might be one of the best ways, when comparing two similar cars (lbs/HP ratio). But how does one differentiate "lag" from torque on a dyno chart?

Notice (from another TB993TT thread) how the HP and torque factory curves are somewhat higher at low RPMs in the K16 setup, and then the lines cross each other around 3K RPMs, where the K24 takes off and never looks back. THIS is "Lag" (Boost onset), whereas a curve that remains higher than the other throughout the RPM range has little to do with lag if anything, but rather has more to do with higher boost used and programming.

http://forums.rennlist.com/upload/dy..._vs408_mod.jpg

I have seen my torque vary by more than 25% at the same RPM point by simply using two different dynos and loads with the same exact engine....

This is where the comparison in this thread is interesting! Real life comparable data.

From Flat 6 magazine also, I am providing some additional data to this topic. Listed by better Lbs/HP ratio to worse. Time it took to achieve a 80-120kph (50-75mph) in 3rd, 4th, 5th, 6th gears.

Observations:

- 996TT vs. 996 TTS, very close in 3rd and 4th, from 3200RPMs or so upwards....Bigger difference in 5th and 6th, where they start at around 2K RPMs.

- 993TT and 993TTS, big difference in 5th and 6th whereas not so much when starting from 3K RPMs+ in 3rd and 4th....

- 993GT2 favourable lbs/HP ratio, therefore it offsets the lag of its K24s somewhat and beats the stock 993TT, except when it starts in 6th gear, at less than 2K RPMs, where even the better lbs/HP does not help it.

- 993TT vs 996TT, same lbs/HP ratio, the 993TT out accelerates the 996TT in 3rd because it starts at 3600 RPM (different gearing), but in 5th and 6th, the 996TT eclipses the 993TT as a result of more efficient intake and exhaust, which reduce lag even with the same turbo in both cars.

-993TTS vs. 997TT, same lbs/Hp ratio, very close numbers in 3rd and 4th, however the 997TT shows its fantastic VTG technology quickly from 5th gear and then 6th gear is way ahead.

- Lag differences are very limited with runs starting at around 3K RPMs+, starting at 1.5-2K RPM in higher gears, they are substantial.

Also interesting to note that despite larger turbos having more lag, they accelerate faster from a standstill to 200kph (125mph), or even in a 100-200kph run going through the gears, where RPMs don't drop below 4K RPMs. The 993TTS puts over a second vs. the 993TT over a 100-200kph run despite the big disadvantage seen on the table below for the TTS running within the gears. :eek: The same thing is true between the 996TTS vs. the 996TT.

Morale of the story, decide what your needs are before making a decision based solely on lag. For the track I would choose somewhat bigger and laggy turbos as I will not suffer from it, if you like cruising in highways in 5th. at 50mph and nail it, go for smaller ones for sure. Torque throughout the RPM range is a totally different story, good mapping and *mainly* boost levels makes the difference, not lag.

http://forums.rennlist.com/upload/80120kph_runs.jpg
Thanks TB, interesting angle to the lag question. :cheers:

Some bosch engineer at the track today was saying one can reduce lag by retarding the ignition at lower rpm's? This causes the combustion to occur even in the exhaust, is harder on the turbos, but is a way of reducing lag? Never heard of this before but was wondering. I'd love to be able to go around the track at 4K and always be on boost.

You can do 2 things to help improve spool up
1)retard timing
2)run a leaner fuel mixture
both the above lead to increased exhaust gas temps which in turn increases exhaust gas velocity and thus quickens spool. It is a common trick that some tuners implement in their programming though it can be dangerous if done carelessly

Acropora, if you don't have boost at 4K RPMs, I would consider a thorough check up on your setup. :confused: Also, try getting off 6th gear every now and then :p..j/k

Are these runs done starting at that speed/rpm or from a lower rpm and the clock "starts" when you hit the entry speed? And please post the road speeds as well. I'll see what I can do ;)

TB and Jean, this is all great info. I'm always amazed about the amount of knowledge/time/energy/effort you guys put in to get us this type of info! Now I know why my car seems so fast compared to others starting in 3rd or 4th at reasonable speeds.

I (and I'm sure many others) really appreciate this kind of stuff.
Thank you,

Ryojo

looking at the bar graph nicely illustrates available torque under the curve. The graphs with the widest discrepancy between 3rd and 6th are peakier/narrower power bands such as the 993TTS which has a 7.2s spread between 3rd and 6th times. The VTG of the 997tt seems to offer no real advantage over the non VTG 996tt - both have about a 3.4/3.5s spread between 3rd and 6th times. Granted, the run length is very short.

Ryojo

Thanks for the kind words. Glad to see some people like this stuff. :cheers:

Eclou,

IMO these numbers are a great testament to how well the VTG techonology works! One should not look at third gear looking for lag effect as much as the higher gears.

These VTG turbos are about the size of the K24s, yet see how much faster they take the 997TT in 5th and 6th gear when compared to the 996GT2 even with its better lbs/HP ratio, it absolutely destroys it and is as fast as the K16 based 996TT.

What we don't see on these graphs is how well they pull at the higher end of the RPMs as well, this is what makes them unique IMO. Small turbos will spool faster for sure, but they will not deliver at the top end, whereas the VTGs do.
:cheers:

It would be interesting to see what the numbers are for the K16/24 and other hybrid turbos - to see how much of an advantage the VTG is in comparison...

Looking at the numbers again, I'm surprised that the 993tt does so well in 3rd and 4th when the rpms are higher, and not as well in the higher gears where the rpms are lower, where you'd think the smaller turbos should build boost faster. I guess the hp differential overcomes the lag at lower rpms in these cars? I would have thought the larger turbo cars would do better in the lower gears where the rpms start off higher - almost counter intuitive... I guess in the lower gears, the larger turbo cars still take longer to get on boost (rpms still not high enough) - despite starting at a higher rpm. Is this just testing off boost engine torque in the higer gears?

Good point Jean. BTW the EVOMS GT700 package 997tt (bigger VTG turbos) pulled 185mph at the Texas Mile. IIRC this is about the same as the RT12 did last year

I don't want this thread to peter out just yet ! What are the opinions from experience of the turbo variations that have an effect on lag? What is the trade off for top end HP against intial response?

IMO there is not really such thing unless you move to VTGs. You can have a decent sized compressor (K24 or K26) with a smallish K16 turbine that will boost almost as fast as a stock K16, but it will normally also run out of breath faster than a large compressor/large turbine at high revs, as it will create backpressure and heat soak resulting from the faster spinning small wheel.

Hybrid turbos deliver in the low end but fail to deliver as good as their larger cousins in the upper end of the RPMs, as seen by TB993TTs test on a properly loaded engine dyno run, and also by real life datalogs.

Large turbos have a more pronounced "lag" which can be somewhat reduced with good mapping and tuning and the right hardware, but lag will always be there!

Heat is the main issues in the smallers turbos - think of the turbo like a bicycle gear. You can get to a certain speed in 1st if you spin like a hamster, but it is much easier in 10th gear, where you can comfortably push with your legs. The cyclist stuck in 1st is going to heat up really fast and wear out. Turbos are similar. The K16 will get up to the same output as the K24 to a degree, but it is spinning so fast the air is superheated and then loses all charge density. One cheater solution used by many import tuners (and now in the 944 turbo world) is to inject water/methanol into the intake after the IC. This fogging mist greatly drops the temps of the superheated charge thru the latent heat of evaporation in the combustion chamber. The end result is also a richening of the mixture. A guy named Laust Petersen has been running mid 20's boost on a stock K26/6 on a 944 and getting more power than many using T04's. Without the injection system the K26 cannot hold more than 16# to redline

I'm thinking of going to maybe K24/super 60's or something to try to move my torque curve about 1000 rpm lower. The big kick in the back happens around 4300 rpm in my car. What I'm worried about is the 'surging' some tuners have seen using too small a wheel.

following on from Jean's dyno graph......

I have a dyno sheet of K16's and hiflowed K24's
back to back on the same car, no other modifications,
both using the standard K16 engine mapping
http://www.qplanet.org/q/993TT/xede/...tdcomp&k24.jpg
for those who want to know what the differences are in driving the 2 setups
the power curve really does match the way it drives.
these K24's were slow to respond, but the top end felt so smooth and effortless.
it didn't feel boosted, it just felt that is the way it was supposed to be.






adding a remap, and some more boost changed it's behaviour quite dramatically
http://www.qplanet.org/q/993TT/xede/993dyno_3stages.jpg

Interesting-- define high-flow K 24's please.

Would be nice to see all (well a lot of them)the potential combinations on a progressive chart of performance expectations! It would be nice to see the comparative claims and results.

In this instance, new compressor wheels were fitted, housings machined, turbine wheel cropped, wastegate enlarged.

My brief to the turbo guy was to hiflow a set of K16's so I would have minimal lag, and some decent top end.
He hiflowed a set of K24's instead :soapbox: so I got everything i did not want....
BIG pic HERE
http://www.qplanet.org/gallery/500/k24_6004.jpg

Some things I've read that I'm not sure about: so if you have hybrids, say K16/24, the turbine and compressor wheel run at the same speed. The K16 part (turbine) spins faster/earlier, but it's directly coupled to the K24 compressor, building boost faster/earlier. ECU keeps boost say at 1.1 bar. With the hybrids, 1.1 bar reached faster (earlier in engine rpm) than say k24/24. I understand up to here okay.

So, why would the hybrid turbines run faster (and build heat "super heat"?). The turbo rpms needed to reach 1.1 bar on the compressor side - isn't it the same - if the compressor is the same - ie. K16/24 vs K24/24. Ie if the compressor side is the same, it would only need to run at a certain rpm to reach 1.1 bar? why would K16/24 run faster than K24/24? they should be runing at the same speed at 1.1 bar.
I would suspect if the turbine and compressor is not 'matched' to a certain extent, the turbine K16 side wouldn't be able to tranfer enough torque (not enough leverage) to turn the larger compressor side as the compressor side gets bigger?
Just trying to understand...

The hybrid turbos will only need to turn the compressor wheel at the same speed as the K24 to achieve the same pressures - correct, but the turbine keeps spinning with the exhaust pressure no matter what. In other words, you cannot control how fast the turbine spins or stop it from spinning past a certain speed. The wheel keeps spinning like a car stuck in a lower gear. The excess pressure is just bled off by the wastegate after 1.1 bar is achieved. This just means the hybrid will bleed off pressure quicker/at a lower engine rpm than the K24. The new VTG turbos CAN bleed off excess exhaust pressure before it overspins the turbine by allowing the vanes to open and bypass the turbine wheel. This is like a "pre-turbine" wastegate.

eclou, Okay thanxs I think I understand. But the waste gates -don't they recirculate or bypass the exhaust gas (to control boost) so the turbine doen't run any faster? Wouldn't the wast gates open at say the 1.1 bar and keep the turbine from spinning faster once 1.1 bar is reached? I thought the wastgate bleeds off exhaust pressure proximal to the turbine (vs the diverters or blow off valves with bleed off the compressed air ( in which case I could see if the diverters were opening that the turbos will keep spinning)). I'm pretty sure that waste gates bleed off exhaust "pre-turbine".

I am even confused by what I wrote. All wastegates bleed off pre-turbine. The pure K24 and the hybrid K24 should have the same shaft speed to produce the same intake pressure, but as the rpms increase the smaller turbine wheel of the hybrid will not be able to flow as much exhaust as the larger turbine and more exhaust pressure and heat will build up in the smaller turbine and then transfer that heat to the compressor side as well.

Depending on which K24 setup one runs, the "lag" is more prominent or less prominent..

On my previous 993TT I ran FVD K24 race turbos with FVD sport cats and muffler bypasses and I was building boost at 2,500RPM or so.. By 3,500RPM I was at full boost if memory serves me correctly. I absolutely loved that setup and my car was a bullet..

I never had a K16 car stay with me with that setup.. In fact the only time I took a loss was against a Yamaha R1 on the highway...

What I find "laggy" is my 996 GT2 K24 setup.. That car has LAG. I dont see boost until 3,000RPM or more. Car only starts to wake up above 3,500RPM.

I think this is the main reason alot of K24 setups are given a bad rep..

I would have thought that pressure/heat/energy would be bled off with the waste gates opening and not be transmitted to the turbos (the extra exhaust gas not going through the turbos but being vented by the waste gates) in the scenario I was going through - and not exposing the smaller turbine turbo to the heat.

It must be that the volume of exhaust gas/energy required to spin/transferred to the K24 compressor (whether K16 or K24 turbine) must be similar for a given turbo RPM, and although the K16 turbine turbo starts spinning earlier/lower engine rpm, there's some 'efficiency' factor that gets maximized at higher turbo/engine rpm at which point the smaller turbos require more exhaust/pressure/engergy/heat to maintain turbo rpm... or something like that....
I'll stop thinking out loud now, I think I've strayed a little from this thread.

Ryojo

Assuming the runs are 80-120 kph here are my figures for a UMW stage 2:

3rd 2.13
4th 3.49
5th 5.62
6th 8.51

ambient temp was 12 deg C

My experience with the stock k 16's and the same setup with an FVD ECU reprogram compared with stock sport K24's and FVD 1997 ECU reprogram is like night and day. By 3700 RPM the car pulls hard and is light years ahead of the K16's. No question that good tuning and a well matched combination contributes to this result. Now if I can get the bypasses and 100 cell cats, things will only get better.

If you could get hold of a GPS device (Driftbox, Performance box. AX22) you could make the above meaningful and run some 50mph-75mph times in the different gears and ascertain whether what you say above is actually true :)

Here is the data for Porsche K16 and K24
K16 K24
3rd gear 3650rpm - 5470rpm 2.8s 3.2s
4th gear 2820rpm-4235rpm 4.1s 4.3s
5th gear 2380rpm-3570rpm 6.2s 6.6s
6th gear 1760rpm-2640rpm 8.6s 10.4s

Appreciate the effort everyone has put into the graphs and technical info. Great information.

Hard numbers aside, the driveability of my K24’s completely changed the car’s personality. With the K16’s acceleration was fairly linear to the throttle application and early in the rpm range. The K24’s respond differently depending on how fast the pedal moved. If you have quick but even throttle application the car will go through the 3700 rpm range quickly and continue to pull. “Stomp” the pedal and it revs up the same until it hits 3700 and the power hits in the way everyone has been describing.

For those of you who are contemplating a change to K24’s and reading this thread with all its data and wondering what does it translate into in real world driving? I can say that after a slight modification in driving stile you will find your car exponentially more fun to drive. The “lag” is minimal and in street use may never be an issue. On the track I tend to like the power moved up the rpm range a bit to offer a little more throttle control before the majority of the power hits. Guess I am just posting some defense for the “perceived” bad rap the K24’s sometimes get. Personally I think they make the car a two-headed monster with a bit more controlled drivability down low and a very hard pulling car when you need it. As Jean’s graph shows it does not take long for the K16 & K24 lines to cross over. No looking back after that point.

Besides a LWF, 5 bar fuel reg. my motor is stock. The exhaust post cat has been bumped up to 2.5” for 2.25”, 100 cell cats, two resonators and then out the back. Not too loud and a bit of a drone at constant 3K rpm. Maybe not for everyone but it certainly has open flow. A non-data based observation, made a huge difference in how the K24’s spool up , but again the extra noise may not be for everyone.

Rick

For the under/ sub500HP 993TT the K16 hybrid with modded turbine section when mounted with the very same K24 compressor wheel will outperform the K24's.. If you take TB's factory graph and raise the boost to the threshold of 1bar or equal the same output the lines will rise higher and sooner vs the K24's..

What ECU are you running with your K24s?

Fleix,

Evo Motorsports / GIAC ECU. Not sure what stage for sure. We think it is a stage II.

If you can get your hands on a datalogger to generate some more numbers to add to TB993tt's table that would be great.

I should have mine back soon and he is welcome to it since we live in the same town....

OK, not that it means very much but always of interest in building a data base I got the DB out and ran some 80-120kph runs.

I did about 3 runs in each gear and these are the average.
Temp 14DegC running weight ~1545kg (4WD, full tank, new HD battery :o)
My turbos are 996tt 2006 RSK24/26 car is 3.8litre higher CR than stock
Ran off a couple of 60-130s around 7.8s.


K16 K24 UMW stage2 TB993tt
3rd gear 3650rpm - 5470rpm 2.8s 3.2s 2.13s 1.60s
4th gear 2820rpm-4235rpm 4.1s 4.3s 3.49s 2.63s
5th gear 2380rpm-3570rpm 6.2s 6.6s 5.62s 4.32s
6th gear 1760rpm-2640rpm 8.6s 10.4s 8.51s 8.16s

Amazing is how lethargic the 6th run was - I thought it was going to rattle the big ends loose :) Absolutely amazed to see that it is similar time to stock - jeez those stock cars are slowwww :icon501:

Edit: My WOT engine dyno boost curve at the low end is:
2540rpm - 0.45bar
3050rpm - 0.93bar
3490rpm - 1.11bar
this may have been slightly helpful to explain the above, I noticed in 6th there was virtually zero positive boost (on the gauge) during the run :)

Here's an 80 to 120 km/h run in my Ruf Turbo R in 6th. HEIGHT VARIATIONS MAKE A HUGE DIFFERENCE! I saw runs vary from the 8 to 11 second range. This one is the flatest I could do.

BTW, I'm not sure how meaningful this data is besides maybe 3rd and 4th gear, since you wouldn't normally drive your car like this. There would be no reason for the engineers to focus on this.

Bill -below is one of the 6th gear runs I did -slightly uphill...

It is quite interesting to compare the 3rd,4th,5th and 6th gear runs since for cars with the same gearing like ours (and with known weight) one can get a feel for what the lag is like and how fast the car is in daily driving. Yours is interesting since it appears that the cams possibly move the on set of boostslightly up the rev range ? It would be great to see your 3rd.4th and 5th numbers :thumbup:
http://forums.rennlist.com/upload/80120.jpg

Now it's getting interesting. Here's my 3rd gear run...

TB993TT, your numbers are mind boggling... For a car that has so much top-end, this is very serious performance.

The main benefit of higher compression is exactly what you are seeing here, better performance at the low end (think about it as early boost), this is where experienced engine building and tuning make the difference, by finding the absolute best balance of compression/boost levels/performance, to keep overall intake temps in check while performing like a N/A at the low end and a race car at the top end . I would simply say that your car serves spot-on the purpose that you wanted. :thumbup:

From all the above, 6th gear seems to be the only meaningful measure of lag, other gears are directly impacted by tuning levels more than turbo size. Great thread!

For these cars, the 6th gear runs are primarily based on displacement and compression. That is, most of the time the car is off-boost.

I think these tests may be a little miss-leading because they don't include throttle response (i.e., when you release the throttle and step on it again, how long does the turbo take to spool up?). The bypass valve helps a little here because it allows the turbo to maintain its speed when you let up on the throttle momentarily. The other delay is when you first press the throttle when the turbo is not already spooled up.

How about running tests in 1st gear from a 5 mph roll to right before the 2nd gear shift point? That's where you'll see a huge difference in the 993 vs. the 997. This test will include throttle response... that is, the time it takes the turbo to spool-up after you press the accelerator.

Bill

What you are saying makes perfect sense if boost was nowehere present during the run in 6th, but it is not really the case, some boost has built by then before the end of the run.

If you look at the run in 6th gear, and taking TB's data, he starts at 1.7K RPMs and has 0.45Bar of boost 100 RPMs before the 120kph mark, meaning you are really measuring his boost onset, as it could have been not there at all.

In his 5th gear run, he is only 100 RPMs without boost, and then it is almost full boost before he has finished his run, you are therefore measuring boost onset only for 100 RPMs, the rest has to do with tuning state. Anything lower than 5th gear you are only measuring the tuning as boost is there throughout the RPMs.

I agree with you that this test is really meaningful to measure "lag" only if the 2 993TTs have similar displacement and compression.

I have zero consideration for lag as I simply don't believe it means much if anything, unless the turbos or tuning are really unsuitable, the 6th gear test is meaningless from a practical, however the only one that really shows boost onset threshold and it's impact, which is the subject of this thread.

None of us would be accelerating from 2k RPMs in 6th gear if he was looking for performance anyway. So this is only interesting as far as data is concerned.

Jean, I completely agree with you. Check out my new Got LAG? thread. That may make it more interesting.

For a car used purely as a road car I have to disagree with the above.......

Engine flexibility is what makes road cars "nice" to drive and contributes massively to a superb driving experience in a daily driver -It is always an objective for Reinhold Schmirler (Mr RS) to produce the widest possible torque curve on the road engines he builds. With my engine it meant on and off the dyno many times whilst different cams and timings were tested, apparently he would lose bottom end and gain top and vice versa until he was happy with the outcome. I believe Ruf also works on this principle.

We call it "lag" which implies it is ALL about the turbo, the sizing of the hot and cold wheels, the flow within the housing, the ZC etc but in reality "lag" comes from the whole of the engine build, matching of components and the ability to test their function (that expensive engine dyno) so it replicates what happens on the road.

Building engines like this is very expensive (due to the componentry and development time) and in a world where (uninformed) people focus purely on a peak power number, it is much misunderstood and often gives rise to people's incredulity at the huge sums $$$$$$ being asked by the best Euro tuners for "hp" which is available in the US for a fraction of the price. The numbers I gave show how this approach translates on the road .....

It would be great to get some more numbers from other RLers -I'd like to see what a well mapped K24 could do ?

BTW I checked the actual revs for the 80-120kph using GPS and rev counter and they are as follows:
3rd gear 3659rpm -5400
4th gear 2950rpm -4250
5th gear 2200rpm -3430
6th gear 1750rpm -2650

Great info! If we get the revs for 5, 10, 15, 20, 25, 30, 35 and 40 mph in 1st gear, you can clearly see the "lag" vs. rpm from my 5-60 mph run by looking at the longitudinal Gs. You can do this in other gears also, but the 5-60 mph run gives a consistant rpm range, and also gets the real low rpm. You don't really need to shift into 2nd to get to 60. I only included that so we can get some performance data at the same time, since 5- 60 mph times are widely published in the US. That is, many people care about the "stop light" performance of their car.

But traction plays a part in a 5-60 time which is a variable that's more difficult to control. In that way the 8-120 test is more consistently repeatable.

TB, I agree with the above. Of course having a responsive engine is a major win on a street car, where I disagree is that this is related to lag... Lag AFAIK is how early boost comes on. In anything less than 6th gear, the difference between different turbos is offset by the tuning setup... i.e. in your case, the reason your car is so fast in 3rd gear, is not because you have less lag than a stock 993TT, but because you have a very well built engine, that pulls very strongly in those RPMs and goes up to 1.2+ Bar etc etc..

Where real lag comes into play, is when you look at your 6th gear run. This is a much more indicative measure of lag. The strength in your engine is that RS Tuning has been able to achieve very little lag for the big turbos that you have, and this was done through state of the art tuning, smart engine building, and components. Like for like, a car with your turbos would have gotten a 10 second run most likely. This is why I am saying turbo lag is not that important, unless it is seriously bad. The real measure of it is in 6th gear at 2K Rpms, any lower gear performance below 6th. is rather related to overall engine build, boost limit, etc.. In all the other gears, boost is already present from early RPMs, so we are not measuring how long it takes boost to show up (lag)

Latest update:

997 GT2 (530 BHP) 80-120kph:

4Th: 3.6s
5th: 4.8s
6th: 7.4s

It has taller 4th-5th and 6th gearing than the 996 and 997TT, yet look at those numbers!

I've been thinking about a simple approach to test the debate between the K16 vs K24 turbochargers. I think that while looking at car vs car is good, the ECU has a large impact on improving the performance.

One approach would be to take one car and structure the road tests 0 to 60, 5 to 60 or 60-130.. Keep the car and the tests consistant..

Start with mounting K16's on the engine and install a stock ECU.. Run the battery of tests.. (mount the 450HP ECU and run the test as mentioned below before taking off the turbochargers)

The mount up K24's on the same engine and keep the stock ECU in place.. Then run the same tests..

While the K16's are still mounted install the Porsche Motorsports 450HP ECU and run the same tests..

When the K24's are mounted install the Porsche Motorsports ECU in and run the same tests..

Fellas..what an incredibly insightful and helpful thread..I'm contemplating putting K/24's on my 993TT w / GT2 body work ,also cat by-pass,and fabspeed muffler by pass..
And have been wondering what ECU modifications would benefit the greater breathing capaity of the
larger compressors,,either Motorsport,GIAC, or FVD?
Not yet at that stage but completing some prior projects,but it awaits in the garage! Thanks Bert

Bert, thanks for saying thanks :thumbsup:
My only advice would be to buy the blowers AND the ECU program from the same vendor and choose one who has a solid rep.....

Budge96: My car (Frank) is set up pretty much exactly as you describe with the FVD setup turbos and ECU. If you would like to take a drive you are welcome. (Assuming it has not sold before you can make it by.):)

Old thread bump.

Does anyone know what is the intake inducer diameter of the K16 turbo and the intake inducer diameter of the K24 turbo that were equipped in the 993tt's?

I have a feeling that my car is equipped with K24's and most likely from factory.

Thanks,

If you have standard factory installed K24s then the part number plate on the turbos should reflect this, as would the part number on the ECU and the option code sticker in the service book and under the front lid.

I have photos of the current turbos in my car (didn't see any blue or any other color plaque stamped just random numbers from the casting).
My car has the 430cv power package option. I do have a photo of the engine ECU as well. However my car is a euro spec and my service book didn't come with any sticker like the US specs Porsche as I have seen through the internet.

I suspect I have K24 because of the lag I feel (no tmy first turbo car) and the very little info I found on the web about the size of the inducer for the compressor side of the K16, my actual turbos are arround 3mm +/- bigger.

EDIT: My right side turbocharger is stamped on the compressor housing the following number: 5324-101-5075. The I google itand found these links:

http://www.stwtuning.de/turbolader/p...1-2005/a-6986/

https://rennlist.com/forums/993-turb...hargers-3.html

Anyways, to be 100% sure, I would need to measure the turbine housing. I might do it soon as I need to replace some seals arround that zone.

Blue plate with info on it, this one has "K16" on first line
http://www.type911shop.co.uk/.media/688057795952.jpeg

^^

Triend to locate the ID tag in my turbos but couldn't find them. I wonder arround what RPM kick the turbos in 2nd gear going WOT from say 2000 RPM. Mine does kick about 4500-4700 RPM.

When K16's and K24's left the factory the ID tag was placed on the backplate. It's tough to see when the turbochargers are installed. They are now placed on the compressor housing cover.

If you are seeing 1 bar of boost around 4300 to 4600 RPM's you most likely have K24's or K24 hybrids.. The only way to verify your turbine wheel, is to read the raised casting number on the K24 hot/turbine housing. Or remove your CAT's and measure the exducer of the turbine wheel.

Thanks for the advise Kevin. I will measure the turbine housing to be 100% sure what I have and will report back.

My display only read 0.8 BAR as we know, but I would have add an aftermarket boost gauge to monitor the boost build up and later remove it since I don't want aftermaket gauges in my car :)