Strange dyno results
11-09-2012, 04:59 AM
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Strange dyno results
Hello, today i took my car to a rolling road to make sure its still making decent numbers, engine health ect.
My first run was fine, 188.3bhp at the wheels (im happy with that), then he goes to do the second run and pulls off the throttle at around 4000rpm because the AFRs are very lean , the car isnt making power and the injector duty cycle has dropped!
I tell him it could be the intake temp so he runs the car until the intake temps ar at 27deg, carries out the third run and the same again, so i gues this excludes intake temps as the problem?
On the fourth run we monitor MAP sensor and he thinks that could be the problem, he carries out the run and AFRs are ok and the car makes 189.6bhp at the wheels. He said the MAP looks fine so we carry out the 5th run and the car bogs down again, lean AFR, low injector duty and low power.
The guy then notices my TPS is only reading 89% open at WOT to he over adjusts the TPs to read 94% at WOT, with the 5th and 6th runs the car is great and makes 194.9bhp at the wheels. But obviously the car fuels on overrun and stalls at a stop.
Does anybody have any idea what could have been the problem? It seems heat related but the IAT and coolant temps where ok. My car has exhaust, test pipe and k&n intake.
My 3 best runs...
BHP of the 3 good runs...
Injector duty for the 3 good runs...
AFR for the 3 good runs... (He said the AFRs will look leaner than what they are because of the twin exit exhaust and the sensors need to be in the test pipe)
Bhp of one of the bad runs in red... (He pulled off the throttle at 4500rpm)
Fuel duty of one f the bad runs in red... (He pulled off the throttle at 4500rpm)
AFRs one of the bad runs in red... (You can see why he pulled off the thottle at 4500rpm!)
Last but not least my car...
My first run was fine, 188.3bhp at the wheels (im happy with that), then he goes to do the second run and pulls off the throttle at around 4000rpm because the AFRs are very lean , the car isnt making power and the injector duty cycle has dropped!
I tell him it could be the intake temp so he runs the car until the intake temps ar at 27deg, carries out the third run and the same again, so i gues this excludes intake temps as the problem?
On the fourth run we monitor MAP sensor and he thinks that could be the problem, he carries out the run and AFRs are ok and the car makes 189.6bhp at the wheels. He said the MAP looks fine so we carry out the 5th run and the car bogs down again, lean AFR, low injector duty and low power.
The guy then notices my TPS is only reading 89% open at WOT to he over adjusts the TPs to read 94% at WOT, with the 5th and 6th runs the car is great and makes 194.9bhp at the wheels. But obviously the car fuels on overrun and stalls at a stop.
Does anybody have any idea what could have been the problem? It seems heat related but the IAT and coolant temps where ok. My car has exhaust, test pipe and k&n intake.
My 3 best runs...
BHP of the 3 good runs...
Injector duty for the 3 good runs...
AFR for the 3 good runs... (He said the AFRs will look leaner than what they are because of the twin exit exhaust and the sensors need to be in the test pipe)
Bhp of one of the bad runs in red... (He pulled off the throttle at 4500rpm)
Fuel duty of one f the bad runs in red... (He pulled off the throttle at 4500rpm)
AFRs one of the bad runs in red... (You can see why he pulled off the thottle at 4500rpm!)
Last but not least my car...
11-09-2012, 11:55 AM
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Thanks chris but its UK spec and unrestricted.
So what sensors would make the ECU lean out the fueling in open loop? Coolant temp, intake temp, MAP, TPS? is there anything else? i know the lambda sensor controls fueling in closed loop.
Thanks Rob
So what sensors would make the ECU lean out the fueling in open loop? Coolant temp, intake temp, MAP, TPS? is there anything else? i know the lambda sensor controls fueling in closed loop.
Thanks Rob
11-09-2012, 12:19 PM
#4
I had extremely lean conditions on a dyno run some years ago... a lot of discussion about my ECU but in the end it was a blockage in the dyno equipment and after it was cleared all runs were normal.
11-09-2012, 02:22 PM
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True i suspected faulty AFR gear myself at first until he pointed out the 4th pic up where the power does not increase from 3500rpm to 4500rpm it just flat lines until he lets off the throttle. Im happy my engines heathly but whatever has caused this is really annoying me! I had a evo 6 run lean a couple of years ago that would not respond to me adding any fuel to the map, i changed the ECU, fuel injectors, fuel filters, fuel pump, MAF sensor, it cost a fortune! Ended up being a injector resistor pack for a few quid. Typical!
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11-12-2012, 01:54 PM
#9
yes,
The slower the ramp time the more the heat builds up on the inside of the combustion chamber.
I build race engines and I fit NGK race plugs pn R5672A-8. These are a cold plug of conventional design. Owners then fit fancy expensive plugs with tiny centre electrodes and notice a slight misfire in 5th or 6th gear when the engine is on full noise for extended periods (long straights). What is happening is the tip of the plug is starting to heat up and cause pre-ignition. It sounds like a slight exhaust leak or ripping paper. Putting the original plugs back in solves the problem.
Normally the power drop off from this is minor but enough to allow other competitors to get a slip stream pass easily.
I would chuck in a set of conventional/colder plugs in a do a few back to backs to see if its something simple like this. Plug design is a balance of enough heat to keep the tip of the plug clean but not too much so the tip starts to glow. I've found the high mileage iridiums tend to favour running the top hot so it stays clean for the long service period.
The slower the ramp time the more the heat builds up on the inside of the combustion chamber.
I build race engines and I fit NGK race plugs pn R5672A-8. These are a cold plug of conventional design. Owners then fit fancy expensive plugs with tiny centre electrodes and notice a slight misfire in 5th or 6th gear when the engine is on full noise for extended periods (long straights). What is happening is the tip of the plug is starting to heat up and cause pre-ignition. It sounds like a slight exhaust leak or ripping paper. Putting the original plugs back in solves the problem.
Normally the power drop off from this is minor but enough to allow other competitors to get a slip stream pass easily.
I would chuck in a set of conventional/colder plugs in a do a few back to backs to see if its something simple like this. Plug design is a balance of enough heat to keep the tip of the plug clean but not too much so the tip starts to glow. I've found the high mileage iridiums tend to favour running the top hot so it stays clean for the long service period.
11-13-2012, 01:07 AM
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Thanks Chris I will do that. I want to attend some track days next year so anything I can do to keep temps down is a bonus. Iv also noticed my radiator is well passed its best also. Time for a new one I think!
Edit- i ordered a new alloy rad today!
Edit- i ordered a new alloy rad today!