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| The cat is located under the curve of the exhaust manifold, pretty far away compared to today’s typical close-coupled cat. We feel that this engine is going to be a bit hard to modify! |
This cross flow of cool intake air adds extra combustion chamber cooling to further reduce the propensity for detonation. The additional cooling also helps keeps the production of the pollutant NOx low. NOx is a byproduct of the high combustion temperatures created by efficient combustion and high compression ratios. The cooling effect of tuned overlap and conventional EGR keeps NOx low, even in this high compression motor.
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| The high pressure injector has six spray holes for good atomization and fuel mixing. |
With direct injection, fuel can also be injected during the intake stroke. As the fuel vaporizes, it cools the air in the combustion space which contracts with the drop in temperature. This also causes a drop in pressure and allows for more air to be taken into the cylinder improving volumetric efficiency.
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| The intake port is shaped for tumble into the cylinder as the piston drops from TDC. This helps ensure good mixing of the fuel and air by increasing cylinder turbulence. |
With lots of cylinder cooling, through direct injection, variable cam timing and exhaust tricks, along with a very homogeneous fuel air mixture due to the turbulent combustion chamber, smooth combustion with no detonation is assured even with 87 octane pee water fuel. The tricks to improve VE through super high compression (yes high compression improves VE), intake stroke cylinder cooling, variable cam timing tricks and efficient exhaust, plus the gains in thermal efficiency due to the high compression ratio, also yield pretty decent power output. To further increase thermal efficiency, the bore size has been reduced from 87 to 83.5mm to reduce the piston’s surface to volume ratio.
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| The tuned intake manifold is conventional and unremarkable. |
6 comments
These type of engines are only restricted by the fact most owners want to use 87 octane. Imagine if you could tune these engines for a 91 or higher octane. I imagine in hot weather these high compression engines detune themselves a lot with 87 octane. It is unfortunate that even recommending a higher octane is taboo in America. At least some manufactures are now recommending higher octane fuels and mapping engine management to take advantage of that fuel. Especially with turbo engines that add to the heat issues that many times require a engine to aggressively detune itself to prevent pre combustion.
High octane fuel is taboo in America? Every car in my garage uses high octane fuel. One V8 and a couple I4 turbos.
we are limited to 91-93 octane by the R+M/2 method
I have a newer version of this engine in a 2015 Mazda 6. I will reach 400,000 miles by the end of the year. Still runs and shifts great and getting 32-35 MPG hwy. The only thing I’ve ever done to this car was replace a lower control arm at 300k miles and the belt tensioner at 150k miles.
Yeah, but the direct injection itself has reliability issues…the cylinder heada will need to be removed between 100000-150000 miles due to the valves gumming up. I believe Toyota solved this problem by placing an injector BEFORE the valves to keep them clean. Does THIS motor have this feature?
I have a hundred and seventy five thousand miles on my indie, miata, in five and a half years running, mostly low octane fuel, I have done a few cleanings in an oxygen sensor other than that, she’s running beautifully.I do a lot of highway driving sometimes two hundred miles a day