12a turbo disaster
11-11-2005, 03:03 PM
#11
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Lynn ....
You said oil temps over 160 hurt power... where is that temp messured?
I always thought oil would normally = water temp.
Also, when a stationary gear is starting to fail. What do you expect to see on the magnet in the oil pan? Large pieces or just like a slurry?
James
You said oil temps over 160 hurt power... where is that temp messured?
I always thought oil would normally = water temp.
Also, when a stationary gear is starting to fail. What do you expect to see on the magnet in the oil pan? Large pieces or just like a slurry?
James
11-11-2005, 03:47 PM
#12
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Join Date: Oct 2004
Posts: 83
You can also create the effect by under reving the engine with a load on it. From cruise at low revs just press down the throttle, during a period where another system is already close to critical.
Ah, I wondered if you could run a turbo rotary too low rpm per load.
My turbo set up was making boost very low but was so loud I would almost always drive and accelerate from 25mph in 5th- boost by 1,500rpm. It did it smoothly and faster than most passenger cars in "proper" gear and no knock sounds that I noticed (though the exhaust was so loud even at 2,000rpm most people on the street thought I was "racing" them- and winning!).
I once raced an old American pick up stop light to stop light through town shifting at 2,500 rpm- I won. Though having less wheel spin helped me as well.
I read an article on the Hennesy Viper where it was slower than stock Viper in the top gear 25-65 mph acceleration, so I had to test mine. My car was faster than Hennesy, but slower than stock Viper.
Is it OK if I am retarding timing enough and coolant, oil, intake temps are low (80C, 80C and 30C) to drive WOT at ~1-2 psi @ 1,500 rpm and 2-4 psi 2,000 rpm? It was spooling so well the higher egts from knock would make a lot of sense. I just installed dual EGT sensors to check on that. I ran LOW timing split at low boost and lots of fuel- that could raise EGTs as well?
There was evidence of detonation on teardown- the dowel pins were noticeably worn where sidehousing meets rotorhousing, lots of chatter marks, very little carbon in there. ~13,000 miles on engine w/ new rotor housings.
Could have been the 20psi+ boost creep issues on 91 octane as well though...
The engine actually finally died of warped 3mm aftermarket apex seals and cracked cornerseals from too high EGT on long 3-4,000 rpm burnouts on an exhaust port w/ no bevel (professional engine buiders for ya). Got too add fuel to the low vacuum ranges in higher rpms... was ~12:1 AFR.
Don't mean to hyjack, just want to learn about "lugging" a rotary.
Ah, I wondered if you could run a turbo rotary too low rpm per load.
My turbo set up was making boost very low but was so loud I would almost always drive and accelerate from 25mph in 5th- boost by 1,500rpm. It did it smoothly and faster than most passenger cars in "proper" gear and no knock sounds that I noticed (though the exhaust was so loud even at 2,000rpm most people on the street thought I was "racing" them- and winning!).
I once raced an old American pick up stop light to stop light through town shifting at 2,500 rpm- I won. Though having less wheel spin helped me as well.
I read an article on the Hennesy Viper where it was slower than stock Viper in the top gear 25-65 mph acceleration, so I had to test mine. My car was faster than Hennesy, but slower than stock Viper.
Is it OK if I am retarding timing enough and coolant, oil, intake temps are low (80C, 80C and 30C) to drive WOT at ~1-2 psi @ 1,500 rpm and 2-4 psi 2,000 rpm? It was spooling so well the higher egts from knock would make a lot of sense. I just installed dual EGT sensors to check on that. I ran LOW timing split at low boost and lots of fuel- that could raise EGTs as well?
There was evidence of detonation on teardown- the dowel pins were noticeably worn where sidehousing meets rotorhousing, lots of chatter marks, very little carbon in there. ~13,000 miles on engine w/ new rotor housings.
Could have been the 20psi+ boost creep issues on 91 octane as well though...
The engine actually finally died of warped 3mm aftermarket apex seals and cracked cornerseals from too high EGT on long 3-4,000 rpm burnouts on an exhaust port w/ no bevel (professional engine buiders for ya). Got too add fuel to the low vacuum ranges in higher rpms... was ~12:1 AFR.
Don't mean to hyjack, just want to learn about "lugging" a rotary.
11-11-2005, 05:24 PM
#13
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Originally Posted by wanksta' post='777591' date='Nov 11 2005, 01:03 PM
Lynn ....
You said oil temps over 160 hurt power... where is that temp messured?
I always thought oil would normally = water temp.
Also, when a stationary gear is starting to fail. What do you expect to see on the magnet in the oil pan? Large pieces or just like a slurry?
James
In both piston and rotary engines, oil is used to cool the pistons and rotors. Rotay oil temperatures above 160
indicate rotor temps over 350. The incoming charge is being overheated and is expanding rapidly while the intake port is still open, causing reversion in NA engines, and wasted boost in turbo engines. Also remember that detonation is charge temperature dependant. So cooler pistons/rotors means more power and less likely detonation. I measure oil temp at the entrance to the rear main gallery.
Fuzz on the magnet is usually the gear. Normally there should be nothing at all on the magnet. Blue flakes is usually the rotor gear walking out and dragging on the iron.
Lynn E. Hanover
11-11-2005, 05:24 PM
#14
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Join Date: May 2002
Location: California
Posts: 22,465
we (xs engineering, and mazda do this too, i hear the mazdaspeed 6 is really bad about it too), tune the ecu so that when you have a temp get too high (water, air etc) that it pulls some timing, and maybe add fuel, it would be nice if you could limit boost too.
how much really depends on your tune in the first place, ive got a t2 running 14btdc and it pulls timing out as the intake air temp gets over 55c (i think up to 6degrees?), car gets reeeeeeaaaaalllllyyyyy sloooooow.
how much really depends on your tune in the first place, ive got a t2 running 14btdc and it pulls timing out as the intake air temp gets over 55c (i think up to 6degrees?), car gets reeeeeeaaaaalllllyyyyy sloooooow.
11-11-2005, 06:38 PM
#15
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Posts: 6
Originally Posted by Lynn E. Hanover' post='777255' date='Nov 10 2005, 06:54 AM
I am here Grasshopper.
You said the magic word.
Knocking.
That is detonation. While it is very nearly impossible to detonate a Normally Aspierated (NA) rotary (Although my driver can do it) it is quite easy to detonate a turboed rotary.
Detonation is intake charge temperature dependant. There is no more to it. There is only temperature.
I can hear the hair standing up on necks around the world, but wait.
There are a number of items that cause the charge temperature to go over the limit either over a long period, or instantaneously.
The rotary, with a wide space between the plugs and no squish areas is practically designed to detonate.
Detonation is the autoingnition of the mixture remote from the plug(s) and AFTER the planned ignition event.
All you need is a bit of extra heat to start it. You can do it with an actual over temp of some system, like water temp and , or, oil temp, (rotor face temp too high) and intake air temp too high. You can also create the effect by under reving the engine with a load on it. From cruise at low revs just press down the throttle, during a period where another system is already close to critical.
The rotor turning below normal RPM for a particular situation, looks like an accelerated flame front (lower octane fuel) to the engine.
See that in your minds eye. The head space is not getting bigger fast enough to allow for the expanding gasses, and as a result, the pressure (temperature) gets too high, too soon. This would not be a missed shift but a lack of a downshift, when required.
Stationary gear failures from long term over stress (fatigue) tend to just get cracks between the teeth, and can be caught early by checking the magnet on the oil drain plug. You would also see shiny rear main bearing from the stationary gear and crank flexing (ouch).
Parts of teeth coming off without cracks between the teeth is more likely the result of a (number) of high overstress events.
So, what to do?
I have no personal experience with turboed rotarys, so this advice may be crap.
Lower charge temperature.
Induction air from high in the center of the radiator opening. Highest pressure, coolest air.
Program more ignition retard when knock sensor is triggered.
Program a bit richer when boost is up. (over rich and way over lean mixtures mimic higher octane fuel)
Observe RPM before applying throttle, downshift if you will still be below redline after shift.
Add induction water injection.
Lower temp thermostat. Plug the bypass hole and run an American 160 degree stat as God intended.
Add radiator capacity.
Bigger intercooler.
Apply water spray to the intercooler when boost is up.
Bigger oil cooler. Rotors are oil cooled. Oil temps over 160 reduce power output.
If OMP is in use, use a straight weight dino oil. If premixing, Redline racing 2 cycle oil in the fuel, Your favorate Synthetic oil in the sump.
Reduce total boost.
use higher octane fuel.
Use a few extra pounds of torque when doing case bolts.
If that iron is not twisted and can be smoothed with a DA (orbital sander) and silicon carbide paper and light oil.
Lynn E. Hanover
11-11-2005, 07:06 PM
#16
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Originally Posted by BLUE TII' post='777605' date='Nov 11 2005, 01:47 PM
You can also create the effect by under reving the engine with a load on it. From cruise at low revs just press down the throttle, during a period where another system is already close to critical.
Ah, I wondered if you could run a turbo rotary too low rpm per load.
My turbo set up was making boost very low but was so loud I would almost always drive and accelerate from 25mph in 5th- boost by 1,500rpm. It did it smoothly and faster than most passenger cars in "proper" gear and no knock sounds that I noticed (though the exhaust was so loud even at 2,000rpm most people on the street thought I was "racing" them- and winning!).
I once raced an old American pick up stop light to stop light through town shifting at 2,500 rpm- I won. Though having less wheel spin helped me as well.
I read an article on the Hennesy Viper where it was slower than stock Viper in the top gear 25-65 mph acceleration, so I had to test mine. My car was faster than Hennesy, but slower than stock Viper.
Is it OK if I am retarding timing enough and coolant, oil, intake temps are low (80C, 80C and 30C) to drive WOT at ~1-2 psi @ 1,500 rpm and 2-4 psi 2,000 rpm? It was spooling so well the higher egts from knock would make a lot of sense. I just installed dual EGT sensors to check on that. I ran LOW timing split at low boost and lots of fuel- that could raise EGTs as well?
There was evidence of detonation on teardown- the dowel pins were noticeably worn where sidehousing meets rotorhousing, lots of chatter marks, very little carbon in there. ~13,000 miles on engine w/ new rotor housings.
Could have been the 20psi+ boost creep issues on 91 octane as well though...
The engine actually finally died of warped 3mm aftermarket apex seals and cracked cornerseals from too high EGT on long 3-4,000 rpm burnouts on an exhaust port w/ no bevel (professional engine buiders for ya). Got too add fuel to the low vacuum ranges in higher rpms... was ~12:1 AFR.
Don't mean to hyjack, just want to learn about "lugging" a rotary.
OK,
why do we have any particular timing setting?
So that the maximum cylinder pressure will be developed by a specific crank angle. This is how maximum power is developed. You are tuning to get that max pressure in a specific place in the cycle.
The best location (crank angle) for this high pressure is built in as a function of the engine design. The crankshaft degrees of ignition advance required to get that pressure at that ideal location changes from second to second based on all of the operating conditions and throttle setting.
For example, flame front speed will be one velocity for a specific mixture, say 12.5 A/F and requires an advance of 22 degrees. If the A/F were to drop off to 14.0 the flame front speed would be dramatically reduced. So the max pressure would be late. So more advance is called for, say 24 degrees to get max pressure where it is best. Then let us say that the A/F were back to rich at 11.7. Then again the advance needs to be closer to 26 degrees. One thing you can see here is that over rich and way over lean mixtures mimic a higher octane fuel. The slower flame front speed of a higher octane just by going richer. There is a slight added benefit of fuel cooling that is not available from going overlean.
Best power power for any condition is about 75 degrees rich of peak EGT. However, prolonged operation at that position will have you at peak EGT from time to time. And that can melt things like pistons or in rotaries crack a corner seal or sag an apex seal.
So now we have this idea of retarding timing to stop detonation. It works, but now the engine feels like a dog.
Maximum pressure is now well after the ideal crank angle and torqure is way down for any throttle setting.
So, a better method of avoiding detonation without altering ideal timing should be used first. Timing is the quickest, so it remains at number one in the trick bag, but all of the schemes as in the other posts are available. Once you add a bigger radiator it is there all of the time ready to fight detonation. Bigger intercooler
same thing. Mild detonation may exist without tripping the sensor. Shut the damn radio off and roll down the window. The tinckling sound when you add throttle in top gear is it. Add a bit of fuel map if you just have to lug around in 5th. Better yet, if you need power, down shift.
You can still detonate the engine with the timing at zero degrees. Just open the throttle and drag it down to real slow with the brakes. Or go up a long hill in 5th and use full throttle now and then. You can detonate a
NA engine doing this. Its just easier in a turbo.
Lynn E. Hanover
11-11-2005, 08:22 PM
#17
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Join Date: Jun 2003
Location: Mexican Border
Posts: 105
Lynn,
Wow, I don't understand how you could keep the oil temps under 160.
Just driving gently in my car I see 180F. Getting on it it goes up to 200F.
I am measuring that with the RB Adapter on the Oil filter. Where do you measure your temps?
I only have about 1800 miles on my engine so I guess the .... not really fuzz but just a lil slury on the end of the magnet.
James
Wow, I don't understand how you could keep the oil temps under 160.
Just driving gently in my car I see 180F. Getting on it it goes up to 200F.
I am measuring that with the RB Adapter on the Oil filter. Where do you measure your temps?
I only have about 1800 miles on my engine so I guess the .... not really fuzz but just a lil slury on the end of the magnet.
James
11-11-2005, 11:30 PM
#18
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Originally Posted by wanksta' post='777683' date='Nov 11 2005, 06:22 PM
Lynn,
Wow, I don't understand how you could keep the oil temps under 160.
Just driving gently in my car I see 180F. Getting on it it goes up to 200F.
I am measuring that with the RB Adapter on the Oil filter. Where do you measure your temps?
I only have about 1800 miles on my engine so I guess the .... not really fuzz but just a lil slury on the end of the magnet.
James
One way to get cooler oil is to add cooling capacity. I have three 13 row Setrabs. But I have lots of room in my tube frame car.
If the irons were worked on, it is possible that component cleaning prior to assembly was less than ideal.
Beyond that what, in a rotary has a steel to steel junction that could possibly generate ferric swarf of any description.
The distributor and OPM drive gears. The thrust assembly. The oil pump. And the rotor timing (stationary) gears.
Clean the magnet. Change the oil. Check crank endplay. If oil pressure is OK it isn't the pump. If there were new rotors or stationary gears installed, then a minimal amount of fuzz will be seen as the new gears work in.
That would be expected early on. And that is why there is a magnet.
After 5,000 miles I would look for next to nothing on the magnet.
If it's running well, it is well.
Stand on it and enjoy. (In an off the road situation under the control of a reconized sanctioning organization with paid up insurance and qualified experienced supervision).
Lynn E. Hanover
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