At higher speeds combustion chamber filling is down and thus combustion pressures are down... |  |  |
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My friend's brother has a Lotus he had prepped for the track.... always tweaking.... then he had a tuner install and ECU chip and tuned the car for 100 octane track fuel. Off the track, he would occasionally fill it with 93 octane. Well, doing this burned up his engine.
Good description of what happened
Peace
Bruce in Philly
Good description of what happened
Peace
Bruce in Philly
| Re: Dangers of Low Octane - Blown Engine MarcW - 9 years ago |
Not a surprise. The demands of street driving can really tax an engine and the gasoline's octane rating.
On the track under real hard acceleration the ECU goes open loop and can fuel the engine richer than it would otherwise. This is to help satisfy the torque demanded by the driver as the engine makes more power being fueled richer. In this richer fueling condition though the engine is less inclined to detonate. Additionally the combustion chambers do not fill as much with air and combustion pressures are down. Ignition timing is not nearly as advanced as one might think either. While detonation is always a concern under these operating conditions it is not as much a risk as one might think. (Or more engines would expire on the track due to detonation as many drivers do not use race fuel while on the track.)
However, around town under low RPM and high load driving such as is encountered when cruising at lower speeds in higher gears the engine is run leaner, at the 14.7:1 mixture at which the converters are most efficient at processing exhaust gases. But a low engine speed at part throttle operation under high load conditions with the throttle butterfly valve open more fully the combustion chambers manage to fill up quite a bit with air and combustion pressures are quite high. Ignition advance can be as advanced under these operating conditions as it ever can be and detonation can occur. In fact much more likely to occur than one might think.
The next time the friend of your brother should get a dual tune: one for the track; and the other for the street. These can be selected by a toggle switch located somewhere in the car's cabin.
On the track under real hard acceleration the ECU goes open loop and can fuel the engine richer than it would otherwise. This is to help satisfy the torque demanded by the driver as the engine makes more power being fueled richer. In this richer fueling condition though the engine is less inclined to detonate. Additionally the combustion chambers do not fill as much with air and combustion pressures are down. Ignition timing is not nearly as advanced as one might think either. While detonation is always a concern under these operating conditions it is not as much a risk as one might think. (Or more engines would expire on the track due to detonation as many drivers do not use race fuel while on the track.)
However, around town under low RPM and high load driving such as is encountered when cruising at lower speeds in higher gears the engine is run leaner, at the 14.7:1 mixture at which the converters are most efficient at processing exhaust gases. But a low engine speed at part throttle operation under high load conditions with the throttle butterfly valve open more fully the combustion chambers manage to fill up quite a bit with air and combustion pressures are quite high. Ignition advance can be as advanced under these operating conditions as it ever can be and detonation can occur. In fact much more likely to occur than one might think.
The next time the friend of your brother should get a dual tune: one for the track; and the other for the street. These can be selected by a toggle switch located somewhere in the car's cabin.
Most of what you said made perfect sense. but i'm not following this:
"Additionally the combustion chambers do not fill as much with air and combustion pressures are down. "
presuming that you mean on track, then with WOT the chambers should be as full as they will ever be, and the compressed pressures therefore as high as ever.
Or am i misreading you?
G
ps: google, gmail and utube all blocked here.
Grant
gee-lenahan-at-gee-mail-dot-com
"Additionally the combustion chambers do not fill as much with air and combustion pressures are down. "
presuming that you mean on track, then with WOT the chambers should be as full as they will ever be, and the compressed pressures therefore as high as ever.
Or am i misreading you?
G
ps: google, gmail and utube all blocked here.
Grant
gee-lenahan-at-gee-mail-dot-com
Laz - 9 years ago |
| Oops, No. China. Shenzhen. grant - 9 years ago |
Laz - 9 years ago |
| At higher speeds combustion chamber filling is down and thus combustion pressures are down... MarcW - 9 years ago |
The air just can't get into the chambers as readily at higher speeds as it does at lower engine speeds. The engine still makes plenty of HP as it is turning at a real high RPM.
Combustion pressures are highest at low engine RPM with a large throttle opening. This condition is obtained at relatively slow speeds in the higher gears under part throttle cruising. The engine is most efficient under these operating conditions. Instantaneous gas mileage -- this in my GTO with its 6.0 400hp V8 -- would climb to over 30mpg and timing advance would be around 30 or more degrees advanced.
Combustion pressures are highest at low engine RPM with a large throttle opening. This condition is obtained at relatively slow speeds in the higher gears under part throttle cruising. The engine is most efficient under these operating conditions. Instantaneous gas mileage -- this in my GTO with its 6.0 400hp V8 -- would climb to over 30mpg and timing advance would be around 30 or more degrees advanced.
Laz - 9 years ago |
The text indicates that it was supposed to simulate a turbine blade failure. Destroy one blade and the whole thing is out of balance and kaboom. Turbine version of IMS failure.
Edited 1 time(s). Last edit at 04/21/2015 12:42PM by Guenter in Ontario. (view changes)
Edited 1 time(s). Last edit at 04/21/2015 12:42PM by Guenter in Ontario. (view changes)
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