GTRgeoff

I have to agree on the EGT. It should be a heads up guage for track work. I haven't had time to respond but have been doing some research. Some SAE papers have indicated EGT's as a primary cause of failure of ceramic turbine wheels, because the adhesive is not up to the high temps or through a delta in the rate of thermal expansion. I'm still attempting to source a 1989 SAE paper on Garretts problems with ceramic turbines as that would have direct relevance. An extract from one.. While this performance advantage [low spool times] is the major factor in the consideration of ceramics for the rotors, the resistance of silicon nitride to the high temperature exhaust is also. Additionally, a lower coefficient of expansion can mean a smaller air gap between rotor and housing and more efficient performance. The major disadvantages of ceramic in this application is the low fracture toughness and the lower Weibull Modulus. A low Weibull modulus means that the strength data are more widely scattered. Therefore, the designer is faced with a very brittle material with more poorly defined strength. An additional problem for the designer is thermal stress at the attachment of the low coefficient of expansion ceramic to the high coefficient of expansion metal shaft. Finally, due to low volume production and difficult manufacturing, the cost of ceramic parts remains relatively high. So even though bog has mentioned the wheel cooling quicker it's close but not quite right. It's the shaft expanding too much causing the increased hoop stresses and failure of the adhesive bond. Some more to explain the lottery of why some turbos fail without warning and some last forever.... Strength Strength of ceramics is very dependent upon the flaw distribution in the materials. These "flaws" can be of a microscopic nature and may not be flaws from a normal perspective. For example, the strength of glass fibers is the highest immediately after manufacture, and simply handling them with clean hands can cause sufficient surface damage to reduce strength by 30%. Because small flaws can have a very large effect, the strength data of ceramics tends to be widely scattered. The most practical way of dealing with widely scattered data is the use of statistics. In the case of ceramic strength data, the standard statistical model is the Weibull distribution. A Weibull parameter (Weibull slope, Shape parameter, Weibull Modulus) is often stated when describing the strength of a ceramic. The meaning and use of this parameter is discussed in Section 2. Another result of flaw sensitivity is that ceramics are much stronger in compression than tension (it is hard to open a crack in compression). Testing of ceramics is often done in bending and the failure stress in bending is often called the Modulus of Rupture, MOR. And a temp vs strength table to compare the materials used.... An overall useful conversation. I still subscribe to overspeeding being a common root cause and will have to come up with some detail to support it, but admit outright temps are resolving as the critical factor so well done Cubes on a well thought through analysis, making me go and do some reading.

This should entertain. Also left the snipper skit as well. Damn 6.14Meg I'm afraid.

And I just got it on DVD so will post tomorrow.

Hell yeah. Thanks for the headsup Harry. Now for some other minor changes to make 'modern' cars competetive. Is there a location for a list of proposed changes?

You're just a ray of Sunshine today mate

Don't thank me until finished in case you stuff it

I'll grab an XXL. Any pics or designs to take a look at?

Finally got the seats from my mate. Thanks for bringing them down. Trader feedback left. Still too narrow but I can modify.

Cut a hole in it with a holesaw. Otherwise, heatgun and a mould to allow it to form the shape.

Cut a hole in it with a holesaw. Otherwise, heatgun and a mould to allow it to form the shape.

If it looks like you will be here for long just kill yourself now. What a cold miserable hole. 6 years and other than the track days and SAU outings I've despised every second. Miserable one day - shithouse the next.

So what's the problem? Scared of moisture ingress?? Your bonnet is not really a proper structural element so moisture absorption affecting the glass transition temperature is not relevant, nor is sudden snap freezing of the interlaminate moisture going to crack the material apart unless you take it from +20 to -30 in a matter of minutes. I would expect a little top coat clear sprayed into a container and brushed on gently would see you clear.

Yeah you're right to question. It's still a carry over for me from early uni days when it was strongly pushed by the materials guru as more a ceramic structure, even though almost all of the elements are metallic and is precipitation hardened. I argued the toss but decided to keep my averages up rather than piss him off by arguing further. Consider MMC's (metal matrix compounds) that are often held to be ceramics by some as well but I think quite different. Some articles so others can make their minds up. I will point out that all use the term alloy so I should adjust my terminology as well. http://www.burnsstainless.com/TechArticles...el_article.html http://www.suppliersonline.com/propertypages/Inconel706.asp http://hcrosscompany.com/metals/inconel.htm Cheers

Actually I won't accept it unless you provide the physical evidence and a significant enough sample. You said the shaft expands, not the shrink fit of the turbine onto the shaft causing excessive hoop stress. Methinks you are not an engineer at all and have decided to run and hide. I have not heard of one rupturing off boost.

High temps will be a factor of high boost on a turbo not suited to that level of boost as the small exit area forces the unburnt fuel to linger longer waiting to exit the turbine and so it continues to burn. Boost is a result of turbine rpm and at higher rpm the blades are subjected to increased tensile load until eventually they rupture. In Jet turbines I have calculated for up to 2mm of blade growth due to tensile loading. Paul the R33 gtst turbine is a larger diameter and as such would rupture at lower rpm than the R32 gtst turbine. It is a combination of the rpm and the actual mass in each blade. GTR turbos are often run at 1 bar with less incidence of failure because they are smaller again.

I think someone should ask for their money back for their engineering degree, or go back and study rotating dynamic forces and ceramic material properties. What you are claiming is the turbo shaft heats faster than the ceramic turbine at the interface, causing the turbine to break at the hub. If this is so then the rate of thermal expansion between the shaft material and the ceramic must differ greatly. Not a bad theory but not fully thought through. A root cause analysis would require that this would happen soon after startup every time, otherwise the adhesive material must be considerably flexible and the turbine over shaft tolerance must be very loose. Ceramic is more tolerant of thermal shock than other materials, hence its application in many aerospace roles as well as piston crowns and innumerable other useful high temp locations. Also, ceramics are not just ceramics. A floor tile will not be the same material as a ceramic turbine or an inconel turbine which is also a ceramic (the stuff used for an R34 GTR N1 turbine), and is usually temperature relieved in order to allow the item to become a single grain through high temperatur grain growth, especially in gas turbines in military jet aircraft. Having said that let me say again as I have mentioned in other threads that the most likely causes of ceramic turbine failure are FOD (foreign object damage) such as a loose piece of material like carbon dislodging in the exhaust and striking the blade(s), often after a turbo R&R or severe overexpansion due to excessive RPM. Ceramic is not tolerant of tensile loads so a situation occurs where the centrifugal loads increase due to the weight of the blades themselves causing one or more to separate. The resulting imbalance either tears the turbine apart or severely fatigues the shaft causing it to snap off at a stress concentrator like the turbine attachment or the bearing region. So, after a refit of stock turbos, play the lottery and hope for the best, or never run excessive boost which causes high turbo rpm. Cheers

SK you mean Bernoullis pressure/velocity conservation relationship of P1V1=P2V2. Reynolds number is a non-dimensional number to indicate an objects slipperiness or drag potential. At the inlet to the pipe the fluid has a certain velocity (V1) and pressure(P1), but as it travels along the pipe turbulent wall growth occurs and the injector takeoffs add turbulence so the effective pipe diameter shrinks, so the velocity (V2) of flow slows meaning pressure (P2) increases as it approaches the regulator. This is fine for steady state but what about if the injectors outflow the pump capacity? Then it turns itself over.

Not really off topic at all I think. Adds to the knowledge. What you are talking of is a pitot tube. Aircraft use both a static pressure sensor and a pitot tube for velocity pressure. Usually mounted close together as a straight probe and the L probe. I think the boost guage still needs to show static or instantaneous boost and a guage for flow rate would be interesting to log as well. Each inlet is so small though to get individual figures you run the risk of disturbing the airflow. Actually regulating the boost transition with a wastegate might better be done off the AFM with a stepper so you could use a big turbo and reduce the rate of power increase. Certainly something to tease the brain with for a few hours.

http://www.mmsport.com.au/Brakes.php http://www.racebrakes.com.au/ Just a start. Revolution Racegear used to have some as well.

Yep, I had the same problem on the GTS25TT. Single BOV just off boost was shuffling. Next setup has GTR BOVs ready to go in.

Aero is one of my specialities and my thoughts are that the extra air into 6 are related to the velocity pressure. It was mentioned before that pressure is the same everywhere. Not true. Air has mass, and that mass causes pressure due to the velocity it travels at, otherwise aerofoils woild not work and a car would experience no resistance due to air. I would predict that it is not a steady state across the rev range, the extra air in 6, but would change. It only needs to occur at a time when fuel flow is inconsistent and temperatures at the rear of the engine are high. Then you have a deadly (to the engine) mixture of events. Shaun, I recommend O rings and a good treatment for your coolant to reduce the deposits and rusting. Looks like the head was not clean or not entirely flat at the blowout at 6.

Memories of past glories. Competing at QRC at Jimna and all the other awesome rallies. Looking forward to getting back, picking up 60-80acres at Dayboro and being a short but fun drive from the main rally centres, and Lakeside. Nice catch Col.

ouldn't have said it better myself. I get mine from SelectMaz. Sealed, teflon and $90 each.

That's ok. Most English as a first language guys have problems with the terminology. BTW below you can see the amount of roll on a GTR33 with Whiteline blade adjustable bars set to full soft front and rear. I was throwing the car in pretty hard and you can see the outside tyres are in full contact with the tarmac pumped to 40psiF/38psiR. You won't need any more than the Whitelines.

Actually it's true by the normal definitions in racing. Traction is a straight line term. Anti-roll bars don't help in a straight line. Grip is a cornering term. Anti-roll bars contribute to the overall balance of a cars grip when cornering. The stiffness of a bar is not however proportional to the diameter but to the diameter to the fourth power, so the 27.1mm solid rear bar will be 2.81 times stiffer then the 21mm bar rather than a straight 1.2 times stiffer. I can bore you with even further detail, but unless you are a race engineer it won't make much difference. Don't buy them unless you are sticking to the race track. The question has been more than answered.