hatchy

Isn't the "dip" seen on most stock 993TT dynos a result of either the ECU pulling timing or opening the wastegate? I am a little confused by the plot as well; if the K16s were not outside their efficiency range, and is able to maintain X bars to redline, why would the power AND torque drop off--is the ECU pulling timing?

Obviously, it would be great if the graph also included the boost level, or timing, or IAT.

Bill S.

Here's the chart for a Ruf Turbo R, independently tested by 911 & Porsche World. The numbers closely match those published by Ruf.

Note that the TORQUE IS NEARLY THE SAME AT 4000 RPM and 6000 RPM (the published Ruf torque is even higher at 6000 RPM, since minor changes were made since this 1998 test). The latest Ruf car pull to 7200 RPM!

To make our cars fast, turbos alone do not do the job. You need to FLOW MORE AIR THROUGH THE ENTIRE ENGINE. From start to end, you need at least the following to accommodate higher boost and provide a broad torque curve:

1. Free-flow air filter.
2. Larger turbo cold side (but not too large)
3. Higher-lift cams.
4. More gas flow (5 bar FPR).
5. 94+ gas to avoid detonation near 5500 RPM (or twin plugs)
6. Larger turbo hot side (but not too large)
7. Free-flow cats.
8. Better engine cooling.
9. Feedback ECU that properly adjusts timing, boost, and fuel by listening to detonation, measuring temperature and load, etc.

Without ADDRESSING THE ENTIRE AIR PATH, you may have a car that's actually slower than you have now! I've seen this many times since I've been modifying turbos (since 1982). Only very few tuners seem to have it all right. Why is Ruf, RS Tuning, Andial and Protomotive expensive? Because their cars are VERY FAST! Be sure you have everything covered before you start your mods. THE ECU SOFTWARE IS VERY IMPORTANT! Ruf works with the Porsche supplier (Bosch Motronics). There's millions of dollars invested in this software. It's not something anyone is going to duplicate easy.

Geoffrey

I'm not sure what you are confused about. What are you defining as the dip? Where are you expecting torque and HP to peak at? Redline?

In the graph you posted, the torque falls by about 125ft/lb between 4000 and 6000. I would not call that consistent. In the graph from my car it falls only 80ft/lb of torque at the wheels (about 100fw) from peak torque at 5000rpm to 6000rpm.


Also, with the way Dynapack displays the graphs, it is squished left/right compared with the RUF graph shown above.

gooseNSJ4

Bill.

Would you say that the Larger Garrett High-Flow Turbochargers would fit your list of extra mod's that you described above. The list would put you in the range of 600 or more HP at the crank.

Jean

Whoever has dealt with Geoffrey knows that he is very impartial, not trying to defend anyone here, but I am very thankful to him for sharing transparently his findings and experience.
Whether the turbos are better or not is still open for debate, most people who used them seem to be satisfied with the results, although no scientific testing has been performed to prove it (That I have seen). Same motronics program and same car with different turbos is what it would take for a conclusion.
Very interesting topic!

Obviously it is everyone's choice to buy them or not.

Geoffrey

Bill,

In your list of items for improvements, I don't disagree with most of them. You do need more fuel, but I'd rather use larger injectors than higher fuel pressure. I do disagree that you need a larger turbine which is what this thread is about. The Hybrids have the smaller turbines but with the larger compressors, actually flow more than the k24s.

OldGuy

Geoffrey alot of people here (at least stateside) are just waiting to get Kevins turbos including me. I am glad he has your endorsement too. that makes me confident that kevin is the way to go on this.
I ought to do it this summer as my TT will retire from the desert heat and wait till fall to come out and play.

Geoffrey

OG, thanks. The main issue I see with using Kevin's turbos centers around the ECU reprogramming. Most of the packages that you see out there have their ECU programmed for the turbos they choose - Garrett for Protomotive, K24s for FVD, Modified K24s for RUF, etc. You need to have reprogramming that reflects the airflow changes the new turbos can provide. I believe Stephen from Imagine Auto has done some work with GIAC to develop a chip reprogram for for these turbos so you might check with him.

The cars that I've done don't have the ECU limitation because I do only MoTeC or other aftermarket systems so I can make it do anything that needs to be done as far as timing, boost control, fuel, and allows a more free choice of components. This is why I selected the dyno sheet to post, because it was completely stock and can show the capability of the turbos without complication of better intercoolers, cams, intakes, etc. I only wish I had numbers for 1bar or 1.2bar, but 550hp is as far as I want to push stock 993tt rods.

Here is the MoTeC datalogging from the Dyno run on the earlier pages. It shows consistent boost and consistent timing while under boost at 15 degrees. Data samples taken ever .1sec.

Bill S.

Remember, HP does not equate to performance. If the turbo is very large, you might get good top-end performance, but you'll get blown away on the street and smaller tracks. I had a 600+ HP 930 with a very large K29 turbo running 1.3 bar. The car was untouchable over 120 MPH. However, it did 5-60 in about 6 seconds (no clutch drop). The car was not that much fun. My Ruf Turbo R will often break 4 seconds in 5-60 runs.

Check the following link for more on "my turbo is bigger than yours":

http://www.andial.com/content/faqquest/quest3.htm

Geoffrey

Bill, You and I are in 100% agreement about the total package approach and I love the RUF approach to building cars. These k16s provide flow on the top end without sacrificing the bottom end.

FWIW, I have a 640hp@1bar single turbo 930 that has excellent throttle response, great low end power, that is so much fun with no issues your 930 experienced. It has a much larger compressor than a k29 and was built by Kevin.

ScottMellor

OG, thanks. The main issue I see with using Kevin's turbos centers around the ECU reprogramming. Most of the packages that you see out there have their ECU programmed for the turbos they choose - Garrett for Protomotive, K24s for FVD, Modified K24s for RUF, etc.

This is exactly my concern. I have an FVD ecu and some kind of FVD k-24s. I have no idea if my ecu would be appropriate for a set of Kevins specials.

Geoffrey

Here is another's opinion on Kevin's Stage 2 turbos. Albeit a 996tt with custom ECU remapping specific to the turbos.

996tt board thread on Kevin's turbos

Bill S.

BTW, I ran against a Stage 4 GT 996 TT with my wife in the car (the other driver was alone). He could not catch my Ruf as we gradually pulled away with 91 octane gas. We plan to try it again soon.

gooseNSJ4

Does this make any sance, I heard this through a grape vine so I am not sure if the explanation is correct.
By changing the housing on the cold side of K-24 and changing the pitch of the impaler can reduce the lag in and increase spool up? I hope this has some merit to it. If possible can any one explain!

Thanks.

Geoffrey

There is something called the A/R number of a turbine. It determines the velocity the exhaust gasses exit the turbine and enter the turbine blades. In general, a lower number = higher velocity = less lag, but there is more to it than that. I believe that the k16 has a .8 a/r and the k24 has a 1.0 a/r, but I'm not positive on the k24. By changing to a lower a/r, the turbo will spool faster, but will create more backpressure and overall turbine rpm will increase.

You can "clip" a turbine which essentially makes the turbine blades smaller (the RUF pictured earlier looks to be clipped) so it doesn't "bite" as much air, again, helping spoolup, but trading some efficency.