[Mk2] [Turbo] 500bhp on a 3071R!

[Jimbob]

Ok,

I think I get what you are saying after reading it a few times.

The previous runs were done with no IT, i.e it was just in the cabinet where the computer was so IT and AT were pretty much the same as the AT is manually input isn't it? I remember 24'C being typed in from a little weather station thingy sitting next to the screen. The previous runs in this configuration were running in the 490's

What I don't get is why the IT is used for correction. If the AT is being measured then that reflects the ambient conditions on the day and as such your IT. Unless your intercooler cooling is non-linear which it won't be if its sized right. On a 20'C day you might have 40'C AT, then on a 30'C day 50'C, why would AT be required?

I don't think I have any of the plots with a different AT on, let me have a look round.

[Kongaroo]

What I don't get is why the IT is used for correction. If the AT is being measured then that reflects the ambient conditions on the day and as such your IT. Unless your intercooler cooling is non-linear which it won't be if its sized right. On a 20'C day you might have 40'C AT, then on a 30'C day 50'C, why would AT be required?

I don't think I have any of the plots with a different AT on, let me have a look round.

It's to make things more accurate as the temperature of the air entering your air filter is quite possibly going to be slightly warmer (eg. by a few degrees) than the ambient temperature shown by the thermometer in the dyno cell.

The intercooler shouldn't come into it at all as it's an atmospheric correction factor that will hopefully allow you to have similar BHP readings regardless of fluctuations in temperature that day and not a measure of how efficient your intercooler is.

What I don't understand is why they would want to leave the IT sensor on the wall and then bring it out for the final runs - did they just forget about it initially and remember about it at the end?

[Jimbob]

I can't see much point in it being used unless you have a hot engine bay. I guess it's good for shootouts as people will have better looking figures.

It wasn't used on the day, presumably as they didn't deem it neccessary. It was used on the last runs as the IAT sensor was starting to show some higher temps and we wanted to verify it was reading correctly. As I said before I am pretty sure it was put on with no correction, just for temp verification.

[Kongaroo]

I can't see much point in it being used unless you have a hot engine bay. I guess it's good for shootouts as people will have better looking figures.

It wasn't used on the day, presumably as they didn't deem it neccessary. It was used on the last runs as the IAT sensor was starting to show some higher temps and we wanted to verify it was reading correctly. As I said before I am pretty sure it was put on with no correction, just for temp verification.

Ok that's cool I think I see where you're coming from. I do monitor my MAT sensor readings when I'm mapping but if I'm not mistaken with your car being a rev 2 you don't have a MAT sensor which is why you have mounted the AIT sensor before the throttle body instead. Is that correct?

One thing though - in DD shootout mode the operator cannot turn on or off any correction factors. This shootout mode was created specifically to try and make a standard mode that would give comparable figures from one Dyno Dynamics to another.

Prior to this being introduced DD dynos were criticised for the operator being able to apply different correction factors leading to some dynos reading higher than they should. Mustang Dynos are often crtiticised in the USA for this very same reason.

Basically what this means is that as you were running in shootout mode (in this case shootout4F) the correction factor was automatically applied and cannot be disabled. There would have been a higher positive correction factor on the run with the IT sensor at 53 degrees than at 24 degrees. Exactly how much depends on what atmospheric correction standard is used on the DD but if it was SAE J1349 it can be calculated using the calculator in the link I posted earlier.

In the interest of IMOC dyno research I think 60 members should chip in a pound each so you can take another trip back to a DD dyno and run on the same map and PSI but with IT sensor in the air box and see whether there is any difference (I'm joking of course )

Anyway thanks for the interesting debate - look forward to seeing how you modify your beast from here

[Jimbob]

I may give the dyno a ring to ask what correction factor was used as how one run made 490's with the AT reading atmospheric temp and then made 509.6 with it reading 53'C is beyond me. It must have been a very small correction factor unless there is one which does no correction?

I may get it dynoed again if I get some NOS to help the spool. It's only £45 per run at the dyno I used.

Not much to come in the way of mods. I'd quote like an Abflug front end and may have a little dabble over winter and keep my bumper for track use. Did some Carbon mirrors (border) and still got to fit an EDFC and pillow ball mounts.

[Kongaroo]

I may give the dyno a ring to ask what correction factor was used as how one run made 490's with the AT reading atmospheric temp and then made 509.6 with it reading 53'C is beyond me. It must have been a very small correction factor unless there is one which does no correction?

I may get it dynoed again if I get some NOS to help the spool. It's only £45 per run at the dyno I used.

Not much to come in the way of mods. I'd quote like an Abflug front end and may have a little dabble over winter and keep my bumper for track use. Did some Carbon mirrors (border) and still got to fit an EDFC and pillow ball mounts.

There are a few different atmospheric correction standards. The SAE J1349 one mentioned earlier is one of the more popular and conservative ones in terms of correction applied.

I read that there is a difference of about 4 percent between the most and least 'generous' correction method used. For eg. 'STD' correction often used in the USA is known to be around 3 percent more likely to inflate the dyno figures than SAE J1349. Some dynos also cap the correction at around 10% (positive or negative) but some don't.

Would be interested to know which correction standard is the default for the dyno dynamics and whether you can swap between them or if it is fixed for each shootout mode. If you do manage to find out please update me