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Discussion Starter · #1 ·
Why do AT and IT temps vary on these rollers? What does it do?

For example if one read 23/23 and the other reads 12/16, what is the difference?

:confused:
 

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Someone told me that for every Degree higher than it should be at the inlet its 5bhp , so if measuring inlet in wrong place you get higher readings etc :confused:
 

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Discussion Starter · #4 ·
Using the example above and the 5bhp theory thats 45bhp difference??? So what the point of dyno the car????
 

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Rule of thumb is within 5 degrees inlet and ambient .

You see all the time people's graphs with huge differentials . Its common theses days to see 330atwhp+ from a MR turbo running low boost and road fuel . I have never seen this repeated once either on a chassis dyno or engine dyno .

IMO they will never do that with there arse hanging out !! But the believers out there can think what they want .

Best and only form is to use the Tarmac dyno ,only way to get the car to perform under the correct load .
 

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Discussion Starter · #6 ·
I agree about the tarmac dyno.

So why do we need to dyno the car? What does it prove?

Should we use 3rd or 4th gear?
 

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It proves whether you have got more power than you had before although the actual figures are irrelevant IMO

It's useful as a before/after tool but not much more.

Andy
 

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Well obviously its for pub talk! But like Andy says it gives an indication of a difference after your car has been tuned or whatever, bearing in mind that surrounding conditions are similar as to when you done the first run!

And a hell of a lot of people would be lying if they said 'I don't want to know what power my car has, I'm not interested' I'm sure deep down everyone would like to know what their own car running, especially with the amount we spend on parts etc..!

Also, I always thought 5 speed manual runs were done in 3rd and 6 speed in 4th, I don't know why its just what I thought!
 

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Discussion Starter · #11 ·
Can the tuners provide some light here!

Should the correct readings be 23/23 to produce accurate results?

Would having the AT/IT to 12/16 produce lower readings?

Please confirm you DD experts?
 

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I tested this on my own Focus @260hp base run at and it the same, I then move the air temp sensor i.e it and rasied it 15c and added 2.5% Hp,
So when ever I dyno the it probe is out of the engine bay so no correction can take place, Yes correct for room temp but I dont belive you should correct for engine bay temp.

Mark
 

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Discussion Starter · #15 ·
Mark - What was the AT reading though?
 

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Raj

TOTD run the air temp the same way as I do.

Mark
cheers for the info Mark

:)

and I wasn't casting any shadow on TotD, was just curious since I've been looking at a lot of dyno run graphs and it doesn't seem to be often that the IT and AT temps match
 

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cheers for the info Mark

:)

and I wasn't casting any shadow on TotD, was just curious since I've been looking at a lot of dyno run graphs and it doesn't seem to be often that the IT and AT temps match
The offical line from dyno dynamics is to run the it probe in the airfilter,
I do not belive this to be correct as you are correcting for hot air temp a problem the car will always have,
So should all my cars run hot airtemp 15c 2.5% increase for free:jump:rockon:
No correct for room temp thats all.

Mark
 

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cheers for the info Mark

:)

and I wasn't casting any shadow on TotD, was just curious since I've been looking at a lot of dyno run graphs and it doesn't seem to be often that the IT and AT temps match
Adding 15c to yours adds just about 10hp;)so you have more power than you thought:thumbup:

Mark
 

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ross that will explain the powerloss,at 60 degrees ive mapped it to remove 6 degrees of timing!!!

as mark says though the proper line from dd is to measure at air filter but this gives inconsistent readings on the high side too.
i sit the 2 sensors just out side the dyno cell and have done for 8 months now,much better!!!
but i did speak to the dd tech from oz and he reckons it should measure intake temp after intercooler

I was a bit sceptical about the IT figures logged by TRL dyno (No offence Matt) , untill I ran my own car at the Dyno Day there:

Quite Warm :eek:

 

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the it and at difference does not product 5 hp per degree of difference for sure, if you lower the temp it doesnt raise the hp, only if you raise it for example putting the temp probe onto manifold. However this is only done as a calculation for loss of air density ie i forgot the sum now but so many degrees of raised temps, reduces density by so much so therefor you would lose horsepower hence the correction.

nothing too much, its easy to see, at and it should be similar, if they are the same, its fine, if they are way out, need to have a look at why
 
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