K24madness

Kevin,

How about in your free time (if you have any) combine your machining skills and attention to detail on a set of K24's with a 32-36 lb compressor wheel (my super 60 works great). Add in the 10lb wastegate springs like I have and lets see the results. I have no doubt that if you did the work the results would be even better than what I was able to achive.

Kevin

I have said this before, making large turbochargers is easy, it is the programming and engine internals that take is to the next level. Here is a project that has been sitting on my bench for awhile. This is a K24/27.. The compressor wheel comes from the 930 K27-7200 turbocharger, when I make my Hyflow's I have a glut of 7200 wheels.. The inducer measures 54mm.

K24madness

You might never hear me say this again but I think thats overkill. From what I have seen on various turbos on the 3.6ltr motor running 1.1 to 1.3 bar a 32-34 lb wheel is ideal.

I will have to look at the MAP for that compressor. I bet its 800+ rating for the two. I don't think we have the best plumbing to support such a beast.

Rassel

As part of my "This is a very good thread" policy, I'm pushing the rate button on this thread. I hope more do the same.

I also request (Sorry for being a PITA Jean), Jean posts the charts in a new thread and we get John.D to make it a sticky. The choice of Turbos is somewhat one of the main topics on this board. Now that we finally got some data about the different Turbo choices compared. It should be spread to all the 993 TT owners. (Oh boy, the 996 TT Forum has a lot to do to catch up.... )

Thank you, all of you providing the data!

mjims

Jean,

A bit late in the thread but I thought you would be interested to know that PSI uses the following EFi Engine Management:

http://www.efitechnology.it/Euro6_Eng.html

Which is programmed by a chap called 'Ole Buhl' from Italy.

Jean

K24,
You seem to be much more knowledgeable about this turbo thing, but a 32-34lb K24 compressor will take you to 500-550HP maximum, unless you have a highly efficient engine with modified intake paths and heads. These engines have a BSAC of 8 at 1.1 Bar of boost if you are lucky. You dial-in more boost, and nothing will happen.

With a heavily modifed engine (breathing mods), you will have enough to get 600hp or so with the 34lb wheel theoretically (Intercooling aside). You need to keep in mind that they cannot be compared to the 996TT, which has a BSAC of 10 or so, and therefore a K16 (28lb wheel) will take you to 520-530 decently.

Kevin's turbos can therefore come in very handy for a 650hp engine provided he ca make them spool fast. I would be the first one to try them.


Jim, thanks a lot for the link, Ole has shop in the UK as well if I am not mistaken. I don't know if PSI are still using him, I was just translating the PSI article.

Rassel, I don't mind posting the charts on another thread, I will add some more graphs first hopefully like the ones Kevin posted, I hope someone shares a few more.

K24madness

Jean,

Based on my fuzzy math 32-33lb wheels (not K24's) are good for 680hp worth of airflow. Not sure how that applies to the 993tt. You have seen my results (on race gas) on 2 different dynos. I won't start a war by guessing my crank HP. I think you would agree that 500 WHP on a AWD mustang is more than 500-550 crank HP though.

FWIW when going from 1.1 bar to 1.2 bar on the dyno I saw a 25 whp gain.

All in all this has been an excellant thread!!!!

TB993tt

MK
RS Tuning don't endorse or have a Maha or any chassis dyno.
Kevin
Great news about the K24RSs thanks a lot
Back to these curves, made very readable thanks to Jean, The only truely comparable ones are the ZC Stage 3, K24RS and 996tt K24/26 and probably the Porsche 408/450 ones IMO. THe caveat about the Stage 3s is valid as with specific mapping as Kevin said, they would doubtlessly have lit up quicker. The windyno curves are interesting being so similar at the bottom end - all in the measurement ?
I have been talking some more to RS and I am now even more convinced about the limits of our 3.6 engines in relation to the intercooling. 550RShp is right about the limit period. Had a discussion about how other "reputable" Bavarian tuners may be able to show 589hp and the response was that sure RS can show 600hp but you will not get it on the road. My simple enquiry about a bit of "Rennlist" tweaking on my next visit to Germany - going 3.8 and gaining 20hp was met with the list of parts- exhaust manifolds, more new turbos, expensive p and c kit and even then 20hp would probably not be possible due to the intercooling . The chat here about turbos seems in a different league (no disrespect meant) compared with the knowledge that to get a few extra hp, a new set of turbos is needed due to the back pressure limits in the (K2426) turbos, the bench testing done over the years to get this type of knowledge is immense and the attitude of RS must be unbelievable to some other tuners. Here is me ASKING how I can be relieved of several 000 Euros and quite happy to accept 20hp gain, and they don't want to do it !!! they won't even take my cash, frig the dyno sheet and make me happy - truely unbelievable.

Kevin

TB maybe they (RS Tuning) are wishing that you would purchase a 996TT or GT2 for your HP endeavors

Why don't you just go and buy the Secan unit and do the intake modifications to get in shoe-horned in.. You car would look awesome with a GT2 wing, especially with the matching Secan intercooler..

I would think that the power available in tuning with more advance and boost with that cooler, would net you more than a 3.8 kit (20HP), and like you said you would still facing a intercooler issue???

Woodster

TB,
where did/does RS Tuning do their Dyno work?
What kind of dyno is it?
MK

Jean

K24Madness
BSAC X 2 (turbos) X compressor flow size= Max "sustainable" HP. This is the ulitmate efficiency measure of an engine as it measures the amount of air needed to produce 1 hp

My mistake on the 32lbs compressors, the K24s have the 28lbs compressors mentioned. A good 993 engine flows around 8-8.5 hp/#/min. With ZC etc.. you will improve the efficiency of the wheel therefore improve the overall output.
This takes us back to TB's last post and the necessary changes of turbos for the improvement of performance. There is no way you can get sustainable 680hp or anywhere close to it on an air cooled 993 engine with those turbos, don't look at the maps, the engine efficiency will not let you get there.

TB
Other than agreeing with Kevin about RS wanting you to get a waterpumper, as I think it represents still "some" challenge to them vs. the "tried it all" air cooled, I think the clarification that needs to be made is that RS talks about VERY sustainable hp, not just "any" hp. If an engine dyno is showing me 700hp and all the parameters verified, I will trust it, however, and here is the catch, I will not claim getting more than say 600-620 (example) sustainable hp on the road. But do a quartermile run and you might still get 650hp at the end of the run.

There are formulas out there that can give you a much better feel for real hp on the road albeit for a short acceleration run, these formulas have been thoroughly tested and seem to be very close to factory specifications published.

Marty, RS have their own engine dyno at home.

K24madness

Jean,

I want to let you know when a compressor wheels are rated to support the airflow and HP levels they do not take into account the abilty of any motor to gulp that amount of air. Thats just how they are rated. Getting that airflow into and out of the motor is another story. The BMEP of each motor will determin accual output. One way to raise it (keeping everything else equal) is to improve fuel quailty.

I have edited my post to clairfy the "680hp" rating.

TB993tt

They still do 993s, they have just completed a 640PS Secan GT2 3.8 race engine apparently.
Jean, your comments above on the hp ratings are spot on although from what they tell me (and this is aimed at KKK engines rather than yours which is far more exotic and I have no doubt can run near or over the 600RS hp level) the power won't last for a 1/4 mile run unless maybe the I/C is covered in ice or something similar. Kevin keeps mentioning the timing and I think this is the area people don't appreciate enough. Because of the speed the ECU can adjust the timing and the degree to which it can retard it, engines which run too high boost with configurations which reach the heat limits very quickly can be saved from destruction easily by the ECU, this just means less power. I am quite shocked about being told about needing bigger turbos to get more power, it shows just how fine all these limits are and I guess once they have built an engine to a certain hp strength (eg Carrillos/head sealing) they can then use the biggest parameter numbers (which they have determined are below the limit of ovaling the bores within an acceptable mileage by testing and racing) possible. I think RSs dogmatism comes from knowing these numbers and knowing that they are not up for debate and that if I want to go up to 3.8 and 20hp then the turbos have to be able to flow "X" amount of air at "Y" temperature (which is affected critically by the back pressure in the turbo) and the ones I have will not do this.
K24Madness
On the timing issue, you are knowledgable about these things I know, I presume you have data logged your timing whilst at WOT, I'm very interested what does it show. I only profess to having an inkling on the theory of these things and don't actually know what numerically timing being retarded looks like I presume their is an optimum number, (is this widely accepted or is that again open to tuner experience/interpretation) and then if the ECU starts to detect knock it retards the spark timing by degrees, but how many is a lot and how many a little ? can we know how much affect a degree of retardation from optimum will reduce hp or does that depend too much on the variables of boost and temperature at the moment of the ECUs decision ??

Kevin

TB;
I have seen on the dyno at the programming level. The 5.2 Motronics places knock control on a high comand structure. If the knock counts are beyond the map table values, it will instantly adjust timing & boost. What is interesting, the value in the map aren't large enough to control destruction of your engine.. What I mean is, if you have a 100 octane program, with 29 degrees advance (that's the number that I have seen) if you by accident run 91 octane, you will induce detonation and destroy your engine because there isn't enough of a threshold to pull timing enough to save the engine.. With that said, you can run two ECU's or twin chip switchers to have a low octane and a high octane program. On the other hand I was able to see 100 octane in use, and it wasn't enough on high boost applications 1.6bars.. Timing was reduced to 22 degrees MAX in the entire 28 second dyno run. HP numbers were low, the torque numbers were decent.

A faulty plug wire will trip the knock count. The ECU pulls timing. In the ECU you can actually see which hole is effected.

My personal opinion is that Timing rules the torque curve on these engines more so than boost. Timing is yanked quicker on these air-cooled engines vs any other application. If you can twin lug your engine and run higher fuel grades, more power can be delivered successfully vs applying more boost..

TB993tt

Got you on the low octane thing, I know when I left Germany to go to Italy, RS gave me (actually charged me full whack ) a few cans of Octane booster which I was instructed to put in if I deviated from the 98RON. Also on all their invoices it says in German about using 98RON minimum.
Regarding the degree angle, this is BTDC right ? 29 sounds a lot to me and so does even 22 - are we saying that the ECU cannot retard any more than to 22deg ? why not less than 22 I guess if you reach the limit of the ECUs range of retardation and the boost does not drop fast enough, you hit that limiter thingy which feels like a rev limiter - I can still trip this in mine when I purposely play with the overboost in a high gear. If the limit is this 22deg, then what happens in say Jean's or Madness's engine if say a plug lead goes bad and the ECU can't retard far enough. The ECU cannot control the boost 'cos its fixed - I guess you go straight to that limiter ?

This excellent explanation is written by Steve W www.rennsportsystems.com (hope its ok the use ?)
Porsche has used twin-ignition in their air-cooled racing engines since the 4-cam Carrera engines. The high-domed pistons necessary for high compression ratios requires another spark plug to start another flame front on the other side of the piston dome. The best place for the spark plug is the middle of the combustion chamber. From the center, the flame front will have the least distance to travel for complete ignition. This reduces the need for as much ignition advance to start and finish the combustion process when the piston reaches Top Dead Center. Since the spark event is starting closer to TDC in the compression cycle, there is less pressure from the beginning of ignition that is pushing 'back' down on the piston crown as the combustion event progresses. This lessens the 'negative' work done by the expanding gasses and allows all of the pressure building in the cylinder to push the piston in the correct direction, making the engine more efficient.
The offset-plug position on a 911 delays the combustion process. By installing two spark plugs per cylinder, you will increase the acceleration of the ignition sequence. This can reduce the required advance by 10 degrees or more thus lowering cylinder head temperatures. In terms of power, twin-ignition will add some 3-4% or more depending upon compression ratio, over a single ignition system. RPM can increase as much as 700 RPM at top speeds. If high compression ratios are to be used, twin-ignition allows all of the power benefit to be gained from the increase. Twin-plug equipped 911 and 930's run much crisper and cleaner with lower cylinder head temperatures and improved throttle response. Plus, a twin-plug 911 is much less prone to plug fouling with today's fuel.