Engine tuning atmosphere differences

[Orion ZyGarian]

Hey everyone..I was just curious about what obstacles people have had in engine tuning between their home school and running at the competition in Detroit.

This is obviously a concern to me as I live in Florida where it tends to be much hotter and denser than Detroit

Yes I searched, nothing came up.

Thanks!

[Orion ZyGarian]

Hey everyone..I was just curious about what obstacles people have had in engine tuning between their home school and running at the competition in Detroit.

This is obviously a concern to me as I live in Florida where it tends to be much hotter and denser than Detroit

Yes I searched, nothing came up.

Thanks!

[Pete M]

I'd say most ECUs would have an air temp compensation table, right? If you tune that during the day and at night, you might be able to get a good enough range to cover you for comp (don't be afraid to extrapolate...). Failing that, you could just input a curve corresponding to the change in density with temp assuming an ideal gas, but that's not quite right.

The other thing to keep in mind is changes in barometric pressure with altitude. We noticed that our map sensor with the engine off was reading noticeably different at West than back home at sea level. Does anyone know what altitude that venue is at?

[Orion ZyGarian]

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Pete M:
The other thing to keep in mind is changes in barometric pressure with altitude. We noticed that our map sensor with the engine off was reading noticeably different at West than back home at sea level. Does anyone know what altitude that venue is at? </div></BLOCKQUOTE>

Thats my biggest concern. Even when temperatures are similar, pressure is quite different. For instance, I lived at sea level back home in Venice and would see barometric pressure always at 14.8 on a sunny day. I dont know if that is the case in Orlando as well, but you get the point; either way, Michigan would have lower barometric pressure and even a small change can easily make a noticeable difference in how the engine runs...my 1.6 Miata can attest to that

[ad]

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Pete M:
I'd say most ECUs would have an air temp compensation table, right? If you tune that during the day and at night, you might be able to get a good enough range to cover you for comp (don't be afraid to extrapolate...). Failing that, you could just input a curve corresponding to the change in density with temp assuming an ideal gas, but that's not quite right.

The other thing to keep in mind is changes in barometric pressure with altitude. We noticed that our map sensor with the engine off was reading noticeably different at West than back home at sea level. Does anyone know what altitude that venue is at? </div></BLOCKQUOTE>

Pete, look at my thesis :P its in there i believe

[Pete M]

I did, and it's wrong... You included data for "Los Angeles" which is rather vague. Let's just say the map sensor disagreed, by a lot. http://fsae.com/groupee_common/emoticons/icon_smile.gif

EDIT: Did a bit of hunting. The california speedway is at an altitude of approximately 1275 feet, and quickly looking up a table vs altitude gives me an absolute pressure of 96.7 kPa. For the record, our MAP sensor at comp usually read in the range 96-97 kPa before engine start, so it sounds pretty believable. It also sounds like something that you'd really want to compensate for if you're not already...

[murpia]

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Pete M:
We noticed that our map sensor with the engine off was reading noticeably different at West than back home at sea level. </div></BLOCKQUOTE>
Could you please elaborate on the differences in the readings? Was the hardware was identical and not been stripped and rebuilt? This data could have some relevance to the TPS vs. MAP thread.

Regards, Ian

[Pete M]

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by murpia:
Could you please elaborate on the differences in the readings? Was the hardware was identical and not been stripped and rebuilt? This data could have some relevance to the TPS vs. MAP thread.
</div></BLOCKQUOTE>

Sure... the car always read roughly 100-100.5 kPa at home. We shipped the car to the states for the 2006 West comp. For the duration of the comp, it read 96-97 kPa. Once we got it back, it was back to reading 100 kPa. No hardware changes in between.

[murpia]

Thanks. Obviously you are quoting the WOT reading, rather than any part throttle TPS to MAP relationship. I guess you saw a 3% fuel economy improvement, then...

Regards, Ian

[Charlie]

Your ECU has a MAP compensation table. Use it.

Air density is a bit more difficult to automatically take care of (when you take RH into account), but can be easily calculated and accounted for, if you so desire. Yo can also calculate it with and without RH change and see if it's worth the manual effort (probably not).

[Pete M]

I was quoting an engine off reading. Throttle position is hence irrelevant.

[Fabrik8]

One fun thing to do.. Go to the NOAA/Nat'l Weather Service pages and put in the local Detroit or Fontana-ish zip code. Instant baro readings. Do this every few days and you'll get a fairly good picture of whats going on in that area.