Robert Kastle
New Member
- Joined
- Mar 12, 2004
- Messages
- 81
I work for a large engine manufacturer and while at work I struck up a conversation with one of the mechanical engineers. The topic was turbin failure. Our engines are about the size of a TR stacked four high and alomost two deep.
What I learned was that to little timing is just as bad on a engine at a given power level as to much timing. Although to little is harder on the turbo and the engine. He mentioned that as the timing is retarded the exhaust temps go up. The headers start to work kind of like an afterburner on a jet,,, burning fuel as it leaves the cylinder. This will improve turbo response but possibly raise the turbin temps through the roof. He gave an example of a French built tank that would inject fuel directly into the exhaust system to quicken the turbo spool-up ( The Engine was a big failure ). He also mentioned that at a given hp level the engine with less timing is going to have to run more boost,,, working both the turbo and engine harder. The lower timing engine will more than likely have higher intake temps due to the higher boost and have possibly higher cylinder pressure for the same given power level. If the lower timing engine were to detonate it would be more likely also to blow a head gasket due to the higher boost levels run to maintain the power. The engine is also much less efficient at lower timing levels
Higher timing equals a more efficient engine,,, lower boost levels for a given hp level and lower exhaust temps.
Now is this true for all engines,,,,,, no. Each engine is a little different so they will not all respond to timing in the same manner.
You should want to tune to have the limits of the turbo (compressor and turbin),,, fuel and the engine converge at the same point.
The trick is that if the turbo limit is not reached to figure-out if the engine responds better to more timing or more boost but always keeping in mind the physical limit of the engine components.
I am one of those nuts that run 26* of timing on pump gas at 16lbs of boost . My car loves it and runs great with no knock. It runs stronger that way than it does with 20* and 20lbs of boost.
I run 32* of timing at the track. I run 115 mph in the quarter in a 3750lb car at 16lbs of boost with race gas. I am looking to lower that timing some,,,, but just a little.
I am no expert just passing on some info that I thought might be worth thinking about. I am an electrical engineer and I work with controls,,,, so when I have a question on engines I go down the hall to the mechanical guys. Most of which are all HOT RODDERs also,,, most of them are into Mustangs.
What I learned was that to little timing is just as bad on a engine at a given power level as to much timing. Although to little is harder on the turbo and the engine. He mentioned that as the timing is retarded the exhaust temps go up. The headers start to work kind of like an afterburner on a jet,,, burning fuel as it leaves the cylinder. This will improve turbo response but possibly raise the turbin temps through the roof. He gave an example of a French built tank that would inject fuel directly into the exhaust system to quicken the turbo spool-up ( The Engine was a big failure ). He also mentioned that at a given hp level the engine with less timing is going to have to run more boost,,, working both the turbo and engine harder. The lower timing engine will more than likely have higher intake temps due to the higher boost and have possibly higher cylinder pressure for the same given power level. If the lower timing engine were to detonate it would be more likely also to blow a head gasket due to the higher boost levels run to maintain the power. The engine is also much less efficient at lower timing levels
Higher timing equals a more efficient engine,,, lower boost levels for a given hp level and lower exhaust temps.
Now is this true for all engines,,,,,, no. Each engine is a little different so they will not all respond to timing in the same manner.
You should want to tune to have the limits of the turbo (compressor and turbin),,, fuel and the engine converge at the same point.
The trick is that if the turbo limit is not reached to figure-out if the engine responds better to more timing or more boost but always keeping in mind the physical limit of the engine components.
I am one of those nuts that run 26* of timing on pump gas at 16lbs of boost . My car loves it and runs great with no knock. It runs stronger that way than it does with 20* and 20lbs of boost.
I run 32* of timing at the track. I run 115 mph in the quarter in a 3750lb car at 16lbs of boost with race gas. I am looking to lower that timing some,,,, but just a little.
I am no expert just passing on some info that I thought might be worth thinking about. I am an electrical engineer and I work with controls,,,, so when I have a question on engines I go down the hall to the mechanical guys. Most of which are all HOT RODDERs also,,, most of them are into Mustangs.
), the tune is much more finicky with high timing. At 20 deg of timing with the boost right at the threshold of detonation so maybe one pass out of three you get 1 deg of retard and zero the rest of the time, if you add one psi boost you may get 1-3 deg of retard on two or all three passes. However, at 24 deg of advance if you add one psi of boost when you are already at the threshold, you will get 5-7 deg of retard on every pass. Same for fuel adjustments. The "cliff" is much steeper here 
