stockboost

Still poking at me aimlessly because you do not understand? I will take your childish insult with a grain of salt, and decide not to comment on your "GT2 Conversion"

Overboosted, meaning that you believe these cars are running too much boost, but what do you mean by too much boost? Too much boost that the motor can handle? Or too much boost that the compressors/intercooling system can handle.

If by making too much power, absolutely there is a limit, much disputed by most of the porsche community. But as far as running as much as 17 pounds of boost into a stock motor, as long as intake temps are down, there is absolutely no problem.

My information comes from personal car R&D, and from customer car R&D over the past 10 years.

Geoffrey

Stockboost,

You forget about cylinder head temperatures which are critical in these air cooled engines as well as the ability to maintain proper ignition angle and spark energy, both of which are limitied in the stock form with single plug and inductive ignition.

There is no doubt that you can address some of these issues and run at higher output levels. In addition, the environment it is designed for will also determine its reliability and longevity (ex drag racing vs endurance racing)

Jean

Wise man, as the builder/owner of the fastest 993 in the US or the world it would have been a priviledge to hear from you, other than subjective criticism of course.

Of all the wise things you always say, the one where you are absolutely wrong is about insulting people, I have been here 5 years and never insulted anyone in my 1000+ posts, you have already managed to insult the board's (lack of, apparently) intelligence with your few interventions and claims, let us know see your contributions please and we will even be grateful to you.

Geoffrey, your AFR point is a good learning, thanks.
K24 I apologize for the OT.

sonny1

Jean, mi amigo, cojelo suave,no vale la pena discutir con este anormal,chao,Sonny.

stockboost

At higher boost levels in any car, you will at some point pass the efficiency level of the head design.
Once you pass that point, it actually takes more from the output of the motor while at safe charge temps, AFR's and EGT's than it does affect the reliability of the engine. What Im trying to say is not just turn up the boost and make the AFR's where you would want them. There is more to it, as you stated, and I am agreeing.

Ingnition upgrades are cheap, and they should be on the to-do list of any modified 993tt street car IMO.

My points are always up for discussion, nobody can ever be completely correct when it comes to something as complicated as these motors. I'm here to learn from you as well as add what little tidbits I have, from before and after my workday.

-Stockboost

JJayB

stockboost
"Define Overboosted"

When the cylinder pressure exceeds thermal and metalurgical design of componets. My definition.
Whats yours?

stockboost

I've yet to find mine. As I said before I've been doing this with street cars that are driven daily, with no problems.
-Stockboost

Geoffrey

I think a lot depends on your definition of reliability, longevity, etc. and what your goals are. I have seen, and it has been well documented that some individuals have built 911 Turbo engines to produce 800-1000hp and are running 30psi of boost. I think they would also agree that the engine is intended to run for 10 seconds at a time and that in turn putting on a road course and running it in that configuration would significantly reduce its lifespan.

I for one have no interest in drag racing, nor the compromizes that need to be made for that environment. Further, it hurts me everytime I watch one of these cars launched while I think of head lifting at 30psi of boost and axle stress. However, it is impressive nontheless.

We have been able to create an 850hp@1.1bar of boost 3.8l engine for road racing, however, it had billet heads to cope with the cylinder head issues, and all of the usually high end internals. It was/is a 30hr engine in a road racing environment and it did/does leak because of case walking, and the cylinder heads warp as the wide bore spacing allows them to slightly lift even with the sealing rings in place.

Woodster

STOCKBOOST,
Could you please enlighten some of us newcomers as to your car and its capabilities?
Is this a car that has been drag raced? Has it also been road raced or tested by any
magazines? I (as I am sure many), am curious about your "fastest 993tt in the world"
What is it's configuration?
thank you in advance!
Marty Kaye

K24madness

Overboost in my book is what you see when the boost gauge exceeds the amount of boost you want to run. It is not uncommon to see this on the factory controlled solenoid. I have seen cars spike up to .2 bar beyond wher they are suppose to be. Aftermarket EBC do a much better job of controlling boost.
On my car with the Greddy controller the boost climbs to the level I set and never exceeds it.

Couple of problems happen when overboost occurs. One is that the IC will heat soak quickly from additional intake temps. Another is that the wastgates will open all the way then you may see a following boost dip.

Boost gauge is a must for all turbo owners. It does not have to be mounted all the time. It should be checked from time to time to ensure there are no problems.

Geoffrey

The problem is NOT THE FACTORY BOOST VALVE...It works fine with aftermarket ECUs which can control them fine. It is because of the Motronic programming and not a limitation of the valve.

Konstantin

it is OT and I do not like to reply to OT but I lets make it short.
Due to the bad wheather teh cars had to make mor ethan one formation lap. They tried to keep the tires warm while boosting AND braking.
The Turbine overeved and got destroyed in the firts race lap.
The car runs now only 0,95 bar boost but it was faster than last year.
The lost 20 km/h top speed but due the AWD and some other mods found some speed in the corners.

Mantey racing had a broken engine due to a missshift and 11000 rpm

The limit on a new 996 TT engine is about 800 RACE HP.
The gear box will not hold up this power for long.
At 0.95 bar they make over 600 HP but with a lot other mods that normal tuners can never do/control.
Put a bigger Turbo another exahust give some more boost and remap the ECU can be done by "almost" anybody.
It is the rest that makes the fine difference.

Konstantin

K24madness

Thanks for pointing that out Geoffrey. In the future I will refer to the problem as a Motronic issue when controlling the factory valve.

Jean

This should remain as a reference point for hp claims that we see around here.


I am assuming it is because of the Motronic tuner and not the ECU limitations themselves.

Geoffrey

Jean,

I would think so, but I don't really know. I only know I use these valves all of the time in Porsche and non Porsche turbo applications and they work fine for me with MoTeC and Autronic.