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Autocar have posted an update on their Project GT86 car;




"The Autocar/Fensport GT86R project car has had another outing. We’ve been helping with Cambridgeshire tuner Fensport’s development of a package of upgrades for the new Toyota. Well, ‘helping’ only in as much as we’ve been raving about how incredibly quick you can make one of these affordable rear-drivers, if you really want to – assuming you know the right people."


http://www.autocar.co.uk/blogs/motorsport/project-gt86-six-seconds-progress
 

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Musketeer said:
Very nice, but is it road legal? Lack of registrstion plates makes me think not.



It doesn't take much to pass an MOT so unless they've removed the cat (which they probably have done) then i'd be surprised if it isn't road legal.
 

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Interesting pic on the Fensport site of the standard fuel map, showing how rich it is at the top end.


Not the first time I have seen such a conservative stock map from Toyota.
 

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Martin F said:
Interesting pic on the Fensport site of the standard fuel map, showing how rich it is at the top end.


Not the first time I have seen such a conservative stock map from Toyota.

what does that mean then?
 

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All production cars that are fitted with catalytic converters are very rich 'up top'. It's not being conservative, it's required to run the cat within design! As soon as you remove the cat you can lean off most engines and free up a few horsepower, but you'd barely notice the difference.
 

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Celica66 said:
Martin F said:
Interesting pic on the Fensport site of the standard fuel map, showing how rich it is at the top end.


Not the first time I have seen such a conservative stock map from Toyota.

what does that mean then?
I believe a rich mixture has a bigger fuel/air mixture than a lean mixture. The catalyst will be damaged if unburnt fuel gets into it. THe lambda sensor(s) near the catalitic converter measure oxygen and are used with other sensors to determine if the engine is running rich or lean. How rich or lean is determined by the ECU and can be "tweaked"


Edited by: GT86Owner
 

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gt_sjo said:
It's not being conservative, it's required to run the cat within design!

















I thought the additional fuel was to ensure in-cylinder temps remained in-check and as a consequence to reduce the risk of detonation (although that's more of an issue on turbo cars) and that running too rich can lead to premature failure of Cats. I would have throught if you are running higher than 5000+rpm and the car is up to temperature then the Cat should remain in its optimum temp range.



Do you have any more info around (or is there something online) with regards to why this rich running is required to ensure the Cat is operating within design? Would like to understand more.
 

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It's actually quite simple mate, in theory anyway. Rich = more fuel/air mixture, lean = too little fuel/air mixture. At any given RPM the engine is sucking in so much air from the airbox, the MAF sensor detects how much and then looks at the map in the ECU to determine how much fuel needs to be injected into the mix.


As standard, it will run lean at certain RPM as this uses less fuel = economy. Too lean is also very dangerous as fuel is used tocool the engine and so too lean a mixture can melt your pistons.



Too rich is safer but then obviously you're wasting fuel. Also has other detrimental effects if it's too rich.... The O2 sensor does monitor this to some extent and re-adjusts the mix but by how much is determined by the ECU.



Hence a re-map can make a fair bit of difference as it's fine tuning that mixture amongst other things! The perfect fuel/air mixture makes the best power.... not toolean, not too rich.
 

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Kodename47 said:
It's actually quite simple mate, in theory anyway. Rich = more fuel/air mixture, lean = too little fuel/air mixture. At any given RPM the engine is sucking in so much air from the airbox, the MAF sensor detects how much and then looks at the map in the ECU to determine how much fuel needs to be injected into the mix.


As standard, it will run lean at certain RPM as this uses less fuel = economy. Too lean is also very dangerous as fuel is used tocool the engine and so too lean a mixture can melt your pistons.



Too rich is safer but then obviously you're wasting fuel. Also has other detrimental effects if it's too rich.... The O2 sensor does monitor this to some extent and re-adjusts the mix but by how much is determined by the ECU.



Hence a re-map can make a fair bit of difference as it's fine tuning that mixture amongst other things! The perfect fuel/air mixture makes the best power.... not toolean, not too rich.
Yep,

one thing to add. The Lambda sensor monitors O2 and with other sensors can work out the air/fuel mixture. It only checks air/fuel mixture is what is should be as set by the fuel map. If its running lean and it meant to be, the ECU will do nothing of course.



Edited by: GT86Owner
 

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Also for the catalyzer to work correctly it has to have a fuel to air ratio slightly above the stochiometric ratio (14.6-14.8 air to 1 fuel for petrol) from here

I believe that the car manufacturers were developing engines that could run efficiently at significantly leaner ratios than this, but development on them was halted (or at least not put into production vehicles) as they wouldn't work with the catalysers.

AlecEdited by: keelerad
 

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Martin F said:
gt_sjo said:
It's not being conservative, it's required to run the cat within design!

















I thought the additional fuel was to ensure in-cylinder temps remained in-check and as a consequence to reduce the risk of detonation (although that's more of an issue on turbo cars) and that running too rich can lead to premature failure of Cats. I would have throught if you are running higher than 5000+rpm and the car is up to temperature then the Cat should remain in its optimum temp range.



Do you have any more info around (or is there something online) with regards to why this rich running is required to ensure the Cat is operating within design? Would like to understand more.

Cats are designed to operate at certain temperatures. Below and above this you damage the cat. Old style 2-pass cats were typically designed for a 750C entry temperature, but some modern 3-pass ones can run up to 1100C or more. For example the Ford Focus ST has a special turbocharger and 3-pass cat which can run EGT's over 1000C.


When you map an engine with a cat (or at least how you should do, but I doubt a lot of tuners do), is you map one particular load site (e.g. 5000 rpm, full throttle) to what you call mean best torque (MBT). This is the the setting where spark angle/cam angle/fuelling produces peak torque. Unfortunately this setting often produces high exhaust gas temperatures (EGT) which are too hot for the cat (and potentially the exhaust valves and/or turbocharger). You have to add additional fuel at this load site until your EGT's are at an acceptable level. On most engines this additional fuel enrichment happens in the top 20-30% of the engine speed.
 

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My knowledge of Subaru ECUs goes back a few years, but I don't believe they'll look at the lambda sensor for input under WOT (wide open throttle).

I'd expect this is the same on the 86, and you'll only really see the ECU monitoring lambda under closed-loop control.

Now, for when the ECU switches between open and closed loop - there's another topic, but suffice to say, full throttle = open loop, cruising/cold-start = closed loop.
 

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The FA20 engine has a wide-band oxygen sensor AFAIK, whether or not it uses that at WOT I do not know. Bosch LSU4.2 type sensors aren't the most reliable, or consistent things in the world, so I would expect now, but you never know!
 

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gt_sjo said:
When you map an engine with a cat (or at least how you should do, but I doubt a lot of tuners do), is you map one particular load site (e.g. 5000 rpm, full throttle) to what you call mean best torque (MBT). This is the the setting where spark angle/cam angle/fuelling produces peak torque. Unfortunately this setting often produces high exhaust gas temperatures (EGT) which are too hot for the cat (and potentially the exhaust valves and/or turbocharger). You have to add additional fuel at this load site until your EGT's are at an acceptable level. On most engines this additional fuel enrichment happens in the top 20-30% of the engine speed.



I can't see this being a problem for leaning out at the top end on these engines though. I'm used to Honda's with higher RPMs and as much power and torque and it's not caused a problem with EGT and cats. It really shouldn't be a problem on N/A cars with this low power.
 
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