MK1 Focus RS power loss
Discussion
Wondering if someone can help with a problem I'm having with the car.
Basically the car was mapped and dyno'd at 260whp, it sat for a couple months and went back to the same dyno for a rolling road day and only made 230whp.
Any idea what could cause a power loss like this, I've checked everything i can think of, even replaced turbo as it was starting to go, but its made no difference.
Basically the car was mapped and dyno'd at 260whp, it sat for a couple months and went back to the same dyno for a rolling road day and only made 230whp.
Any idea what could cause a power loss like this, I've checked everything i can think of, even replaced turbo as it was starting to go, but its made no difference.
In my opinion unless it feels down on power it's probably nothing! Variance in the dyno potentially or if I was really cynical I'd say the operators fudged the figures when it was mapped to make you more happy but then you said it was whp so probably not then!
If it feels alright I wouldn't worry too much!
If it feels alright I wouldn't worry too much!
Fresh fuel? Makes a big difference as modern high octane stuff goes off very quickly. The fuel pumps are also weak on these, could be a sign its struggling to meet demand in the injector duration is maxed out (you can check this by seeing if the fuel trims are high) If the pump has never been replaced I would put a new one in before it lets you down, they tend to last 10 years and go without warning.
Max_Torque said:
Different ambient temp, different ambient pressure, variations in rolling roads (especially the highly suspect calc / estimate of flywheel power from wheel power, and for turbo's the rate of acceleration /gear used during the run)
if the car still "feels fine" it probably is!
Ambient temp, air pressure, humidity should not make a difference because the figures are corrected. On the road, yes it will be quicker on a cooler day with high air pressure but the RR should compensate for these differences. if the car still "feels fine" it probably is!
Kidders said:
Max_Torque said:
Different ambient temp, different ambient pressure, variations in rolling roads (especially the highly suspect calc / estimate of flywheel power from wheel power, and for turbo's the rate of acceleration /gear used during the run)
if the car still "feels fine" it probably is!
Ambient temp, air pressure, humidity should not make a difference because the figures are corrected. On the road, yes it will be quicker on a cooler day with high air pressure but the RR should compensate for these differences. if the car still "feels fine" it probably is!
(however, it's more likely to be the flywheel power "correction"....)
Max_Torque said:
You are assuming that the generic rolling road "correction" is what occurs to the engine in the car. Which it won't be.
(however, it's more likely to be the flywheel power "correction"....)
No I'm not.(however, it's more likely to be the flywheel power "correction"....)
If he went to the same RR twice, on Day 1 the weather was 10c, 1030+mb pressure and 60% humidity, the car would make for arguments sake, 220 bhp @ the wheels, corrected it makes 230bhp.
The next day it's RR'ed again, this time 20c, but 1010mb and 85% humidity, the car makes only 200bhp @ the wheels, but correction figures are used to calculate this back to a 'default', corrected power, 230bhp @ the wheels.
There are so many variables, like the inlet temperatures which could pull the timing back, thats why correction factors are added. You are talking about the calculation made to establish '@ the flywheel power' which is different to atmospheric correction.
Kidders said:
Max_Torque said:
You are assuming that the generic rolling road "correction" is what occurs to the engine in the car. Which it won't be.
(however, it's more likely to be the flywheel power "correction"....)
No I'm not.(however, it's more likely to be the flywheel power "correction"....)
If he went to the same RR twice, on Day 1 the weather was 10c, 1030+mb pressure and 60% humidity, the car would make for arguments sake, 220 bhp @ the wheels, corrected it makes 230bhp.
The next day it's RR'ed again, this time 20c, but 1010mb and 85% humidity, the car makes only 200bhp @ the wheels, but correction figures are used to calculate this back to a 'default', corrected power, 230bhp @ the wheels.
There are so many variables, like the inlet temperatures which could pull the timing back, thats why correction factors are added. You are talking about the calculation made to establish '@ the flywheel power' which is different to atmospheric correction.
(pity you're completely wrong but hey, we all gotta start somewhere ;-)
Blatant copy and paste -
''One common use of the dyno correction factor is to standardize the horsepower and torque readings, so that the effects of the ambient temperature and pressure are removed from the readings. By using the dyno correction factor, power and torque readings can be directly compared to the readings taken on some other day, or even taken at some other altitude.''
How's it calculated?
The Society of Automotive Engineers (SAE) has created a standard method for correcting horsepower and torque readings so that they will seem as if the readings had all been taken at the same "standard" test cell where the air pressure, humidity and air temperature are held constant.
The equation for the dyno correction factor given in SAE J1349 JUN90, converted to pressure in mb, is:
where:
cf = the dyno correction factor
Pd = the pressure of the dry air, mb
Tc = ambient temperature, deg C
The pressure of the dry air Pd, is found by subtracting the vapor pressure Pv from the actual air pressure. The relative horsepower is simply the mathematical reciprocal of the correction.''
''One common use of the dyno correction factor is to standardize the horsepower and torque readings, so that the effects of the ambient temperature and pressure are removed from the readings. By using the dyno correction factor, power and torque readings can be directly compared to the readings taken on some other day, or even taken at some other altitude.''
How's it calculated?
The Society of Automotive Engineers (SAE) has created a standard method for correcting horsepower and torque readings so that they will seem as if the readings had all been taken at the same "standard" test cell where the air pressure, humidity and air temperature are held constant.
The equation for the dyno correction factor given in SAE J1349 JUN90, converted to pressure in mb, is:
where:
cf = the dyno correction factor
Pd = the pressure of the dry air, mb
Tc = ambient temperature, deg C
The pressure of the dry air Pd, is found by subtracting the vapor pressure Pv from the actual air pressure. The relative horsepower is simply the mathematical reciprocal of the correction.''
Edited by Kidders on Wednesday 10th September 21:36
The std SAE correction factor formula is a "generic" formula, used for power certification, to enable MINOR differences in ambient conditions to be, to some degree, negated.
However, it is NOT a universal panacea. This is because there are many more effects on engine output than simply that caused by intake air density (which is what the SAE correction factors attempt to correct for). Crucially, with a turbocharged engine, such as that in an mk1 RS (which, incidentally, I developed and calibrated for Ford) the engines spark sensitivity, the effective "gain" of both the intercooling system and the main cooling system, and the characteristic efficiency of the turbo charger (both compressor and turbine) all play a large part in determining the power output for any given set of inlet conditions. The SAE std formula is not designed, and indeed makes no attempt, to correct for those additional factors.
But, as i said, it's all pretty irrelevant anyway, as in this case, there will be a bigger margin of error in the actual rolling road and coastdown/loss estimator factors than the engines output......
However, it is NOT a universal panacea. This is because there are many more effects on engine output than simply that caused by intake air density (which is what the SAE correction factors attempt to correct for). Crucially, with a turbocharged engine, such as that in an mk1 RS (which, incidentally, I developed and calibrated for Ford) the engines spark sensitivity, the effective "gain" of both the intercooling system and the main cooling system, and the characteristic efficiency of the turbo charger (both compressor and turbine) all play a large part in determining the power output for any given set of inlet conditions. The SAE std formula is not designed, and indeed makes no attempt, to correct for those additional factors.
But, as i said, it's all pretty irrelevant anyway, as in this case, there will be a bigger margin of error in the actual rolling road and coastdown/loss estimator factors than the engines output......
Hey guys thanks for all the replies.
We are sure it must be a problem with the car, as the same mods on other cars make far more power.
Car has:
OMEX 600 ECU
John FRS Turbo
Airtek Intercooler kit
Full turboback 3" Exhaust
Fuel Pump
The weirdest part is that it seemed to be hitting a wall at 230whp, with boost at 1.2bar and 1.5 bar there was no increase in power.
We are sure it must be a problem with the car, as the same mods on other cars make far more power.
Car has:
OMEX 600 ECU
John FRS Turbo
Airtek Intercooler kit
Full turboback 3" Exhaust
Fuel Pump
The weirdest part is that it seemed to be hitting a wall at 230whp, with boost at 1.2bar and 1.5 bar there was no increase in power.
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