mpesik

Hello there. It's been cool and damp here the last few days. I've been accelerating proudly these last couple of days. The weather now is nice, but with only a differance of 5 degrees C. The vehicle does not accelerate nearly as well as the days before. Car starts fine cold and idles super. -This seems to always happen ,the warmer it gets the slower I get. I understand about air density,Barometric pressures and all. But a 5 degree change in temperature should'nt be so obvious on me ars. Thanx -If you reply. mikE.

GRGGOODSPEED

BELOW 70 IS GO TIME
My car does the same thing, when it 80 + it's SLUG!

mpesik

Hi Mr. GRGGOODSPEED. Thanks for your reply. I'm talking about Yesturday morning 10 degrees celsius and a little rain.This Morning sunny 15degrees celsius. And I'm a 944! Mike.

sharkmeister85

I've noticed a similar performance pattern with my '85. I know it runs rich, probably much too rich (intend to deal with this soon). I think (SWAG) that on colder days the denser air helps use the extra fuel making more power, but when the days get hotter, the over rich is amplified and starts killing power. Any other theories?
Glenn

GRGGOODSPEED

Where are you?

mpesik

53degrees west 113 north. Mike

mpesik

Hi Mr. sharkmeister. I too am running rich-can smell it -bad! Hmmmmmm. Mike Thx 4 reply.

GRGGOODSPEED

Mike
Bittern Lake, AB, Canada
Approx. altitude: 746 m (2447 ft)

mark kibort

You guys are killing me!! hey, 10 degrees is less than 1% net change .. Im sure you all can feel the difference in your 928 rocket in the quartermile in 15.1 seconds vs 15.2 seconds

even 40degrees F would be in the 6% range, and thats only 10hp on top of 200hp. sorry folks, just cant feel this delta in HP, although you think you can. try 60-100mph in 3rd vs 4th. NOW theres the noticable difference. with a 200hp car its like comparing to a 265hp car. (35% increase in HP effectively)

its not just density, its also humidity as well. 10 degrees cooler with more humidity, could yeild the exact same power! got to look at the charts for sure.

mk

GRGGOODSPEED

Mark,
Good point but,
It's more like 30 degrees is a BIG change.
The car runs much stonger at 45 than 70+
and hates 80+

mpesik

MR.Kibort -I ****e you not! No underestimations nor exaggerations. there is a differance from yesturday to today and I don't have a hangover. Something is amuck here and if I can't find the problem out ,I'm going to be humiliated by the next nissan. Do you all on this forum want that. For god sakes I'm one of the representatives of the 928! Mike.Certified-Not Insane.

Garth S

Altitude will always reduce power in any normally aspirated eng; however, that is a constant in the case of living there ( at 53/113) so has no bearing on day to day varience. Temperatures much above 30 C start to be noticable in power loss, but in the comfort zone of 25 C to the cool of 15 C I've never noticed much change. We used to join several P cars from Calgary (~3000') to run up to Banff/Radium (Rockies) on 30 C summer days with no probs.
So, .... you either have a far more sensitive personal accelerometer than some, or there is a genuine metering problem of some sort. There is all the classic good stuff to read up on the MAF from John S and Rich, and others.
Alternatively, there remains the possibility of the FPR losing the ability to regulate correctly. While early cars have one damper and two FPRs, the latter cars have the reverse.
A misbehaving FPR will generally increase supply pressure leading to extra unmetered fuel = rich: beyond a certain point, if the pressure were to increase excessively, injector currents do increase in some cars to the point of the injectors being shut down by the ECU.
Sooooo, it just might be a good thing to take a fuel pressure measurement if this thing continues to turn the S4 into a 944.

PS - if you start to make up a pressure tester, set aside 2 of those H2S spec gauges for me!

sharkmeister85

I'm no mathematician (I'm not even sure I can spell it ), but you are pretty good at it so indulge me please. I don't follow how "10 degrees is less than 1% change". If 10 degrees were 1% does that make 1000 degrees 100%. Sounds stupid, so maybe I am. Just looking for answers, not trying to be a smartass.
Thanks,
Glenn

Garth S

Yeah, confusing! Go back to intro Physics and the Gas Laws: The world of temperature starts at Absolute Zero, -273K: Consquently, small changes in ambient temperature are referenced to absolute zero .... so the relative change in density for a 10 C change is 'peanuts', for example!

mpesik

Be aware of this one .For garth is DARTH!!!!!!!!!!. mike-the sensitive **** guy.