Datsun 280Z -77 - Build thread

peter_s

Club Member
You said he is known for accurate numbers on stock cars, which you can't really inflate the figures on.
If he is intentionally putting in a high ambient temperature, he is inflating the BHP result which will reflect well on him if the software performs the correction.
I don't get it.

If you don't look at the recalculated number for crank (who cares about that anyway), the car delivered 298.3 wheel horsepower onto the roller. That figures is not temperature dependent, that's mechanical?
 
I don't get it.

If you don't look at the recalculated number for crank (who cares about that anyway), the car delivered 298.3 wheel horsepower onto the roller. That figures is not temperature dependent, that's mechanical?

Its not, its a calculated figure based on the software(thus the software config and settings).

By altering figures on correction or adaptation values, you could make it say 5bhp or 5000bhp.

Its a lovely curve though and I like how it likes to rev!
 

Mark N

Club Member
I don't get it.

If you don't look at the recalculated number for crank (who cares about that anyway), the car delivered 298.3 wheel horsepower onto the roller. That figures is not temperature dependent, that's mechanical?

That figure is still corrected by having the 55 degC ambient temperature input into the system, the only thing that is not calculated is transmission losses to get the flywheel figure.
Don't get me wrong, I think you have had a great result but you should definitely challenge that ambient temperature value with your tuner and get him to check his manual which states "air temperature - put in the ambient temperature, not intake temp!".
 

jonbills

Membership Secretary
Site Administrator
I haven't followed the debate about ambient vs inlet, but I don't get it either.
the engine isn't sucking in air at ambient temperature, its sucking in air at the inlet temp. so any correction for air density should be from the inlet temp, not the temp. of the air somewhere else in the world.
No?
 

Mark N

Club Member
I haven't followed the debate about ambient vs inlet, but I don't get it either.
the engine isn't sucking in air at ambient temperature, its sucking in air at the inlet temp. so any correction for air density should be from the inlet temp, not the temp. of the air somewhere else in the world.
No?

The placement of the IAT sensor would then determine the correction.
Cars with the sensor further away from the heat of the engine would have less of a correction and thus make less power if corrected to inlet temperature.
My 280Z with the FAST system has the IAT in front of the throttle body, do you think it will ever see 80 degC?
 

jonbills

Membership Secretary
Site Administrator
well I agree an IAT can be badly located, and measure the air temp of the engine bay or whatever. But you do want to compensate for the temp of the air entering the engine, right?
And that is what the IAT is intended to measure.
 

Mark N

Club Member
The closer an IAT sensor is to the heat of the engine, the less accurate it will be with heat soak.
The IAT is just used to detect the the temperature differences from the day it was mapped and adjust fueling accordingly.
Why wouldn't every Tuner place the IAT in the hottest spot on the inlet then claim the largest correction possible?
 

peter_s

Club Member
Will do
That figure is still corrected by having the 55 degC ambient temperature input into the system, the only thing that is not calculated is transmission losses to get the flywheel figure.
Don't get me wrong, I think you have had a great result but you should definitely challenge that ambient temperature value with your tuner and get him to check his manual which states "air temperature - put in the ambient temperature, not intake temp!".
So this is not how it works. I understand if it were 20 deg and you put 55 deg as the temperature, then you would get an annormal increase.

However, the dyno takes the input air temp (mine is located right outside a trumpet). The dyno takes that as a referance and calculates it against the DIN standard. The ambient temperate doesn't matter, only the temp just at the intake. Or rather, that is what the ambient temperature is at the intake.

Corrected the car made 335ps flywheel, and the dyno also calculated that I can gain 14ps if I can lower the intake temperature.
 

jonbills

Membership Secretary
Site Administrator
The closer an IAT sensor is to the heat of the engine, the less accurate it will be with heat soak.
The IAT is just used to detect the the temperature differences from the day it was mapped and adjust fueling accordingly.
Why wouldn't every Tuner place the IAT in the hottest spot on the inlet then claim the largest correction possible?
I located my IAT so it can always give an accurate measure of the temp of the air entering the engine, so the ECU can calculate how much fuel to inject accurately.
why would a good tuner do any different for a customer car?
 

peter_s

Club Member
I located my IAT so it can always give an accurate measure of the temp of the air entering the engine, so the ECU can calculate how much fuel to inject accurately.
why would a good tuner do any different for a customer car?
Indeed, it's a key part of making the map.
 

Mark N

Club Member
Ok, if you put two completely different engines on an engine dyno and, uncorrected, they put both down 200BHP when the ambient temperature is 27 degC.
The first one has an inlet temp of 80 degC as the inlet is above the exhaust and the second one has an inlet temp of 50 degC as the exhaust is on the opposite side.
If you use inlet temp to correct the BHP value to DIN at 20 degC, the first engine will have the higher BHP value.
If you correct with ambient temperature, they will both increase by the same amount.
 

peter_s

Club Member
But my car was showing less power when temps increased.

I get what you are saying, but the figures still follow the formula that more heat =less power, which means the dyno is compensating for it
 

jonbills

Membership Secretary
Site Administrator
yes I can agree with that. If your IAT isn't measuring the inlet air temp, it wouldn't be much use for this.
 

Mark N

Club Member
But my car was showing less power when temps increased.

I get what you are saying, but the figures still follow the formula that more heat =less power, which means the dyno is compensating for it

Your car made less power due to engine heat raising your inlet temperature, they dyno would have measured this drop in power, not compensated for it.
It would then correct that power figure to the DIN 70020 value based on the ambient temperature value of 55 degC that was input.
The ambient temperature and atmospheric pressure inputs are there to compensate and standardize the atmospheric conditions (to Din 70020 in this case) to create comparable results across the globe.
 
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peter_s

Club Member
I will have a discussion with my tuner next week, but so far I don't think the number is off.

The tuner is really good (aren't they all), there have been tons of race cars here going through his shop, they all confirm the numbers are correct for their application.

I have had several dyno charts now from other DSI Stage 4 builds with the exact same setup as mine, they all produce 300whp.
 

Mark N

Club Member
Coincidentally, 55 degC is pretty much the highest ambient air temperature recorded on Earth (Death Valley).
 
I will have a discussion with my tuner next week, but so far I don't think the number is off.

The tuner is really good (aren't they all), there have been tons of race cars here going through his shop, they all confirm the numbers are correct for their application.

I have had several dyno charts now from other DSI Stage 4 builds with the exact same setup as mine, they all produce 300whp.

it’s obvious it’s a very strong engine with a lovely curve, no one is arguing against that.
 
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