Interesting PDF on Formula Mazdas (Renesis Engine)
10-04-2012, 05:15 PM
#1
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Interesting PDF on Formula Mazdas (Renesis Engine)
Interesting read, I have never seen this before. Just thought I would share, I couldn't find it linked anywhere. Looks like they use the S2 Renesis? The page on engine speed limiting confirms what other builders have stated.
http://www.starmazda.com/competitors...isTutorial.pdf
http://www.starmazda.com/competitors...isTutorial.pdf
Last edited by 9krpmrx8; 10-04-2012 at 05:23 PM.
10-04-2012, 09:36 PM
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Fantastic read.
I agree with the >9,000, though I would interpret that page as 8,800-9,000 "slow engine damage" as related to the "fuel cut over 8,600 so the engine isn't getting the lubrication from the fuel"
This also implies that the fuel is premixed
Lots of great info for even street cars in there, like the EGT info, how to detect something is failing, etc...
And note that the coil testing procedure isn't OEM Mazda's, even though it's the street coil. It uses the spark tester.
I agree with the >9,000, though I would interpret that page as 8,800-9,000 "slow engine damage" as related to the "fuel cut over 8,600 so the engine isn't getting the lubrication from the fuel"
This also implies that the fuel is premixed
Lots of great info for even street cars in there, like the EGT info, how to detect something is failing, etc...
And note that the coil testing procedure isn't OEM Mazda's, even though it's the street coil. It uses the spark tester.
10-04-2012, 11:18 PM
#8
rev it up
Great information thank for finding and sharing. I will stay below 9000rpm from now.
They also talk about having an o2 sensor for every port. I am not sure if the current computers have the capability of handling extra sensors
They also talk about having an o2 sensor for every port. I am not sure if the current computers have the capability of handling extra sensors
10-04-2012, 11:31 PM
#9
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Skc I'm sure you have read it since you have been here longer than me but you know when the tach shows 9k rpm you are really lower than that by at least a few hundred rpm already.
10-04-2012, 11:48 PM
#11
rev it up
Yes, I did read that earlier. I had a habbit of staying in the same gear on the track on the straight and then bouncing off the rev limiter for the last 100m or so before brakeing. It did the same on the down shift.
I am trying to listen to the buzzer now for gear changes. Driving on the track is so demanding on the car and driver.
I am trying to listen to the buzzer now for gear changes. Driving on the track is so demanding on the car and driver.
10-05-2012, 07:17 AM
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No, I would say that the >9,000rpm damage is not just for the race cars.
If you read through the section:
I presume that this is because of the later section here:
Slow engine damage from no lubrication makes sense.
However, that is a very different implication than the >9,000rpm:
It doesn't note slow, or might, it says 'will'. Even bearing failure would be a 'might'. This is probably a direct reference to rotor tips contacting the housing, and even a single event of this WILL damage your engine. This same effect was shown by EricMeyer. For once I don't even think my argument of proper balancing would come into play here, because I would believe that these engines WOULD be properly balanced. So this is probably e-shaft flex allowing the contact to occur.
If you read through the section:
Extensive over revs between 8800 and 9000 on downshifts over a long
period can cause slow engine damage.
period can cause slow engine damage.
The ECU cuts spark above 8600 rpm, but it also cuts fuel at zero
throttle input. Therefore the engine is being starved of the lubricating
oil in the fuel at high rpm for long periods of time when running above
8600 rpm t zero throttle
throttle input. Therefore the engine is being starved of the lubricating
oil in the fuel at high rpm for long periods of time when running above
8600 rpm t zero throttle
However, that is a very different implication than the >9,000rpm:
Any over rev past 9000 RPM will cause damage to the engine
10-05-2012, 10:08 AM
#18
An interesting read. It would be good however to have more information on the engine installed and how it's used.
"The ECU cuts spark above 8600 rpm, but it also cuts fuel at zero
throttle input. Therefore the engine is being starved of the lubricating
oil in the fuel at high rpm for long periods of time when running above
8600 rpm at zero throttle"
Is this over-revving on downshift any different than running to 8-9k rpm and simply letting off the gas when in gear? (which also does a fuel cutoff, but is encountered much more often than overrev). Any premix is cut off, but the OMP continues to inject oil.
"The ECU cuts spark above 8600 rpm, but it also cuts fuel at zero
throttle input. Therefore the engine is being starved of the lubricating
oil in the fuel at high rpm for long periods of time when running above
8600 rpm at zero throttle"
Is this over-revving on downshift any different than running to 8-9k rpm and simply letting off the gas when in gear? (which also does a fuel cutoff, but is encountered much more often than overrev). Any premix is cut off, but the OMP continues to inject oil.
10-05-2012, 10:19 AM
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Hiflite,
I think the difference here is the ECU, since they don't run a street ECU. That portion of the comparison makes it harder to determine. You are correct that if the ECU cuts fuel with zero throttle input, then just letting off the gas anywhere in the rev range would be cutting off the premix. Although perhaps if there is not an active combustion, the residual fuel left from the last fuel injected provides enough lubrication for short periods?
There is no indication of if the Star Mazdas use the OMP in that document, but I have to believe they do. The street ECU injects OMP rate based on load, but I don't know what off throttle decel injection rates are like.
I think the difference here is the ECU, since they don't run a street ECU. That portion of the comparison makes it harder to determine. You are correct that if the ECU cuts fuel with zero throttle input, then just letting off the gas anywhere in the rev range would be cutting off the premix. Although perhaps if there is not an active combustion, the residual fuel left from the last fuel injected provides enough lubrication for short periods?
There is no indication of if the Star Mazdas use the OMP in that document, but I have to believe they do. The street ECU injects OMP rate based on load, but I don't know what off throttle decel injection rates are like.
10-05-2012, 10:20 AM
#20
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Yeah I'm not sure about the exact setup but I think they are running an S2 engine (based on injector colors mentioned) and they are likely using the new OMP setup on that engine.
10-05-2012, 03:19 PM
#21
good read
guys just use common sense---i have been saying for years that this is NOT a 9K rpm engine.
I redline at 8.2 K even though I have increasing power above that.
At that high rpm two things can happen--rotory tips can touch the irons etc ot the e shaft can flex. I have had a builder to tell me if you miss a downship and accedently get to 10K rpm--then just drive the car to the pitts or home, park it and remove the engine because the e shaft has flexed and damage has been done.
Besides the heat and the friction that increases dramatically between 8-9K is amazing.
What caught my eye is the oil temps. Everyone I know with rx8's on the track ( not dedicated race cars) are running too high oil temps. Most of us are measuring on the cool side and 220F is very very common. 230F is not unheard off and I have seen 240F on a few when I was riding with them.
Pause for though.
guys just use common sense---i have been saying for years that this is NOT a 9K rpm engine.
I redline at 8.2 K even though I have increasing power above that.
At that high rpm two things can happen--rotory tips can touch the irons etc ot the e shaft can flex. I have had a builder to tell me if you miss a downship and accedently get to 10K rpm--then just drive the car to the pitts or home, park it and remove the engine because the e shaft has flexed and damage has been done.
Besides the heat and the friction that increases dramatically between 8-9K is amazing.
What caught my eye is the oil temps. Everyone I know with rx8's on the track ( not dedicated race cars) are running too high oil temps. Most of us are measuring on the cool side and 220F is very very common. 230F is not unheard off and I have seen 240F on a few when I was riding with them.
Pause for though.
10-06-2012, 07:26 AM
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Great post, receiving reliable info like this from a reputable source is rare and invaluable. I found the oil change interval and 9k point rather surprising, but it's great to know.
10-06-2012, 10:38 AM
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I don't think many of us have ever encouraged >9,000. "Redline" is more of just the high RPM, and technically the red part of the tach starts around 8,500. Just going till the beep works too.