I think the difference here is scoobyclinic are looking to see what they can get out of the engine, where as John is thinking reliability and warranty.

All are been setup for 98RON fuel, would not recommend any less than that for a WRX STi.

Neither would I personally, But Subaru generally cover a broad range of different types of SUL so its user friendly... What brand fuel are you mapping them on for 98 ?? as Tesco and v-power are 99.

Here's a silly question for you, if your car is mapped on Tesco 99ron is it fine to use v-power?

Oh well. Here goes! I will try to show the effect of retarding the ignition on the temperature of cylinder head, cylinder wall exhaust, turbo etc.
If you forget the charge for a minute, and just consider the piston compressing and decompressing air, then you'll know that as the air is compressed, it's temperature rises.

The temperature and pressure traces would look a bit like this.

http://img.photobucket.com/albums/v3...ps6900a423.jpg

Igniting the charge earlier means the mixture is burning as the piston is still rising up the cylinder on the compression stroke. The burning increases the temperature, which increases the pressure, but at the same time the piston is also increasing the pressure which increases the temperature!

Here's how the temp and pressure traces look when the charge is ignited 45° before TDC.

http://img.photobucket.com/albums/v3...pse250d62f.jpg

We can see that the two effects combined increase the pressure and temperature dramatically. The fuel is still burning past TDC, so the temperature continues to rise even though the piston is now descending down the piston which expands and cools the gas slightly offsetting the increase in pressure and temperature from the fuel burn.

Now consider what would happen if we ignited at TDC. The piston is now descending down the cylinder, again expanding and cooling the gas. This effect works against the increasing temperature of the fuel burn, meaning although the temperature from the burn is still high (still the same energy going into the same mass of air) the overall pressure is dramatically reduced.

http://img.photobucket.com/albums/v3...ps9cae35e9.jpg[/IMG]


You can see that the pressure and temperature are already dropping before the fuel burn really gets going so less of the energy can create work (power and torque). Notice also that because it takes longer for the burn to get going, there is more residual heat left at the end of the stroke, which increases Exhaust Gas Temperature and also transfers more heat to the head and cylinder walls, which in turn will go into the water jacket.

As for all the exhaust gases leaving the cylinder. If this were the case why bother flowing heads and headers or adding big bore straight through exhausts.

Oh and the STI has variable exhaust and inlet valve timing. Which can also be mapped and might be a clue to how you get big torque figures! And possibly beyond the average mappers knowledge base. But if you understand the graphs you will get there!

Can see this getting rather boring for people haha but...

All you have quoted there is correct and makes total sense.

Those graphs are spot on, theories correct.

Now, look at the numbers, those graphs are talking 45 degrees difference in timing. The difference between a high comp turbo motor staying in 1 piece forever and blowing itself to million bits is about 3 degrees timing when set up to the optimum. I don't think 3 degrees swing has anything like the effect you're talking about. I'll shy away from mentioning MBT points as most high comp turbo motors don't hit them.

Those graphs are quoted clearly for a normally aspirated motor where heat is your enemy. We're talking turbos, the more heat and pressure in the manifold the bigger the expansion rate over the turbo and the more boost. We're limited by materials getting too hot and failing. Too much temp and you'll overheat the runners/head/valves/wheels etc etc which then rolls onto charge temp and you chase yourself in circles.

Porting and such does work, but the vast majority of gains are on the inlet side for that reason, opening an exhaust port up but then still trying to blow into a 900 degreeC 1 bar of pressurised turbo manifold makes it less important. You seen the internal casting on o.e. turbo manifolds? Flowed headers again are NA tuning orientated, a long length turbo manifold works well at high sustained rpm, but not for punchy fast spool when a short runner setup will retain heat and low rpm turbo efficiency.

Big bore exhausts reduce backpressure on the turbo so the difference in pressure across the turbine wheel is greater so faster expansion, so faster spool and greater efficiency. Big bore NA exhausts don't work as the absorb the pulses so you cant use them as a scavenge effect at the collector.

...Still unsure how you think the gases are being held in the cylinder?

WRX STI thread I thought this was... Great cars by the way, impressive, when would a white one be available John? :)

It's already been mentioned John's specified lower torque levels for reliability and so a warranty can be offered. Greater numbers are clearly easily attainable but they don't want to risk every one of their customers new cars.

OK, 95% of that from you 2 has gone straight over my head, but I am sure my engine guy will be able to translate it all into plain English for me on Monday. I can answer 1 question though, a white one is available for delivery March redace :lol1:

Because of the warranty I offer with the car, I have to ensure there are sufficient tolerances built in as do the factory, else my warranty company will prevent me from offering them anymore as both Chris and redace have already correctly said.

Subaru have already posted on their site that any modifications will invalidate their warranty, as they are well aware there are plenty of modified ones out there already, and if I am selling these as ...bhp increase and ...torque increase, then everyone we do has to hit that target as a minimum, else I would not feel comfortable putting mine or the companies name on them.

Sorry, I meant 99 rob84, as I run mine on Shell V-Power, company fuel card won't work in Tesco :lol1:

Oh well. I will hand my PhD back. But my original post did say both were running the same boost pressure! I am off to read up on Mass Fraction Burned.

If we cannot talk about tuning the new WRX STI then I will go quiet.

The injectors max out at 350bhp by the way.

John is the 340/340 safety number based on the 340R pack then?

Why would you not use 98/99 Ron???

Just seems like penny pinching to me.

Yes, and no. Yes, as that was what was offered on the previous model, and that is what people were wanting on the new one, but Subaru said they would not be offering it on this car.

But no, I was lead totally by my engine tuner, who has worked on these for many many years, and both myself and my dealer principal (who has dealt with him for almost 15 years) trust him completely. If he says it is safe with safety built in, then we are happy, if he says it is on the edge, then we follow his advice. I have yet to meet anyone else who has the depth of technical knowledge he has, but that can also put it into plain English for me to understand as well :lol1:

I wanted originally a 50-60 increase, but his advice was that this would leave very little margin for error, and increase the chances of a failure and I didn't want that.

Hope that makes sense :)

:thumb:

Because you have no idea that it has any effect on engine reliability.

Quite agree, but you do get morons running sti's on 95 and wonder why they run like ****e all the time. it beggars belief :thumb:

I used to run mine on v-power and 20% meths for a bit of extra safe power

Makes perfect sense to listen to your expert that you trust. I trust my mapper and that is because he builds engine management systems, writes the software and he can answer all my questions.

Just to say got my car back today ��thanks to some great service from crossroads dealership. Just got to run it in now.

Also passed its first MOT :D

Tony

Glad it is sorted Tony. By the wording of your post it sounds like new engine. So that is 2 out of 204 that I know of. Any advance on 2?

Absolutely agree terzoscooby. It is great having someone working with you that has the same goals and values as you have, knowing they are there for the long run not just a fast buck overnight.

That's great news T5nyw :thumb:

Me too Tony, glad you're back on the road.

If that represents the total number of failures then 2 out of 204 is less than a 1% failure rate after three years.

I'd say that's pretty good going.

Could just be the tip of the iceberg and all that but I doubt we'd have had the thread at the top of the page if we'd been given the 2011 spec from the start.

Cheers guys and many thanks for your patience. I was not going to post anything until lit was actually back on my drive.

There are issues and are oil usage related. And not ring ring land failure.

By next week I'll start a thread in technical with my views, concerns and issues. For experts to discuss.

so I'll not post anymore in here as not to spoil or over run this thread.

Tony

Anyone seen the article in this months Top Gear?

Nope? Good?

They try to climb a 7 mile mountain in America covered in snow in the new Sti. I won't spoil it for you!

Have a quick look for your self, go to the comments at the bottom and let's just say the sti gives the bmw 235 a hard time.:norty:
http://www.topgear.com/uk/photos/BMW...WRX-2014-05-08

in case it's not obvious, you need to go through the pics one by one to read the full review.

That's not the article I was referring to, it's in this month's (August) Top Gear. They attempt to get to an observatory up a mountain which a car has never attempted before.

Anyone bored yet then �� Tattoo Park weekend ? ...