Kevin

Not all cat bypass systems are created equal. Not all 100 cell Cat systems are created equal.. The 130mm diameter 100 cell cats with stock diameter piping (60mm) is good for most street engines. It isn't until around 750 NM that one needs to step up to (70mm).. TB posted pictures of his 130mm X 70mm cats.. You have to tune for cat bypasses and you have to tune for 100 cell cats to get the maximum torque out of the engine.. Power under the curve is relatively easy with the new compressor wheel technology and zero clearance turbochargers.

K24madness

Sounds like a sales pitch to me. Quite the self serving statement.

K24madness

Congrats on the K24/26 choice. Very nice combo. A slight adjustment in shift points and you will not be disapointed.

Cargraphics makes fantastic mufflers. Make sure you get the race version. The race version has larger pipes. If you combine the fabspeed catbypass pipes with those mufflers the spoolup will be very good. The difference between 100 cells and catless is minimal.

If you must have cats check with TB on the race cats he uses. They have 2 1/2 inch pipe also. The larger pipes have a major impact on spool up.

See Shiv's explation on the second post.

K24madness

Remember its the delta between Turbine Inlet Pressure (before turbo) and exhaust back pressure. Any time you reduce exhaust back pressure you change the ratio for the better.

If you had a TIP of 30 PSI and backpressure of 10 PSI that is a 20 PSI delta.
If you reduce backpressure to 2 PSI you now have a 28 PSI delta.
That pressure difference is what spins the turbo. Which do you think would spool up quicker 20 PSI or 28 PSI pushing on the turbine in the turbo.

pstoppani

Instead of attacking a person, why not just stick with a factual response ...

K24madness

My anwers are related to the question asked about "reducing lag and making torque peak lower on K24/26's" in the original thread. The Zero clearance plug was nothing more than a sales pitch. Its not an attack just an honest observation.

Kevin

Zero Clearance is directly related to power under the curve. If one can build boost sooner per wheel rotation, you are building power and torque.. Lag is reduced...

Red rooster

K24madness,
Are you measuring backpressure at the motor exhaust header or at the turbo exhaust ?

Geoff

Red rooster

Asked this question to get to whether the thread is about mild upgrades or serious power .


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K24madness,
Are you measuring backpressure at the motor exhaust header or at the turbo exhaust ?

Geoff

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Any input from an expert ?

Geoff

K24madness

Both places.

Before the turbo (exhaust header) is turbine inlet pressure after turbo is exhaust back pressure

Red rooster

OK , now I understand your numbers. Sure, reducing backpressure to reduce turbo inlet pressure is a good,good move.
Engine power is directly related to the relationship between boost pressure and header pressure.
Things really happen when boost pressure is the higher pressure.
For that reason anything that can reduce header pressure is good , provided that enough thermal energy is left to spin the turbo .
A quick look at the old F1 motors that got 1000bhp from 1.5 litres , in qualifying trim , shows that exhaust and intake pulse tuning, used effectively can bring outstanding results.
Maybe there is more to do in this area ?

Geoff

ttAmerica RoadsterAWD

Geoff, there are always trade offs. Ideally, one would want a high velocity gas exit from exhaust valves straight to turbine. This requires a cross section of the header to be small enough to achieve high velocity, yet large enough to avoid being choked off. In an ideal dream, the primary headers would be dynamic, ie, they would shrink in diameter when there is little velocity energy (just after idle), and expand wider with wide open throttle. The key would be to have the highest possible velocity without compromising with static-one size header primary-which is what we have.

This is sort of what happens to us in our cardiovascular system. The diameter of your arteries are dynamic-changing ever so quickly to achieve as much pressure as needed to keep you awake and alive whether you are in a fight or flight situation, or just sleeping and posting on rennlist. For sure, so far it appears that the absence of back pressure post turbine is optimal, until somebody proves there exists a harmonic diameter where a certain size exhaust is tuned harmonically to enhance elimination of exhaust gases.

Hope this helps.

Jaime

ps. Cool! just notice I finally got my RED member with "addict" on my avatar.....yes, addict I am!

Tms951

Lag, describes how fast a turbo spools up at wot, boost thresh hold describes minimal rpm to start producing boost.

the lower the rpm the laggier it will be, the higher the rpm needed to make boost the higher the boost thresh hold.

Red rooster

tt America AWD,
Agreed . One element that you havent addressed is the potential for resonance tuning of inlet/exhaust manifolds.Too often the turbo is expected to do all the work ! Just because there is boost pressure the assumption is made that maximum cylinder filling is happening . Although some of the rules are different ,a lot of the basic N/A principles still apply.
For example I dont think the 993tt inlet has a secondary resonance pipe like the N/A . Goodbye some top end power !!!!
All the best

Geoff

ttAmerica RoadsterAWD

Jeff, as a matter of fact, the tt DOES have a secondary resonance chamber on the intake manifold! It is blocked off but, If you so desired, you can punch it out and open it up. It's know to help higher end performance at the expense of lower end torque. Some people have done this. Todd Knighton is in the camp that likes doing it. He showed me a spare intake where he had dremeled out the partition incase I wanted to do the same.

cheers, Jaime