Car getting slower Roadcourse - Mazda3 Forums : The #1 Mazda 3 Forum
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post #1 of 12 (permalink) Old 06-28-2013, 03:04 AM Thread Starter
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Car getting slower Roadcourse

Hi guys,

as some of you know i like to track my car very often on roadcourses. I noticed that the data logger is showing that my top speed on the straights is not as high as it should be. Its 5km/h slower then my best times.

This is the last year this track is open and i want to break my personal best of 69.44 My lines and understanding of the corners improved but somehow the times are not reflecting that. After reviewing the data, seems like when i clock my best time at 69.44 the long straights speed was 158km/h where as nowadays i am getting 153km/h. Same shift points though and corner speed prior to the straights.

69.44 sec:

current sessions equivalent:

What could be wrong? I blew my motor and the 69.44sec lap is the first track day the new motor went though after swap. I always put some octane boosters. Only power mods is CAI. Filter is new. MAF recently cleaned

Thank you

Last edited by AtomSphere; 06-28-2013 at 03:06 AM.
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post #2 of 12 (permalink) Old 06-28-2013, 08:16 AM
PZ
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My guess is that the new engine is probably down a couple ponies from the old one. Nothing you are going to feel on the butt dyno, but obviously shows up on lap times.

Edit: Could also be that the new engine, being new, has more internal drag because the parts have not worn and the engine is not revving as fast as the older, more 'loose' engine was. That would also cost you at the end of a long straight.

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Last edited by PZ; 06-28-2013 at 09:00 AM.
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post #3 of 12 (permalink) Old 06-28-2013, 08:32 AM
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There are a lot of factors, most notably is the different engine. Others are things lik air temperature, humidity, your fluids, and anything creating drag (I.e., a brake pad not fully releasing). It's really difficult to say. If you went back in the fall after the temps drop and the humidity dries up you might hit similar speeds. But, as the person above posted, it's likely just the difference in the motors (or too many timbits).
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post #4 of 12 (permalink) Old 06-28-2013, 04:46 PM Thread Starter
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I agree could be a ton of factors and I didn't even feel any difference. If I have 5hp more, I can't perceive the small changes.

The 69.44 lap was done on a new engine though. Just anything a few months after turns out to be slower only on the long straights. Nothing changes on the other corner's entry speeds. Air temp was approx the same. No brake pad drag. I tried figuring out as much as I could because I service my own car for the most part.

This is puzzling.
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post #5 of 12 (permalink) Old 06-29-2013, 11:29 AM
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More weight in the car?

OR

Climate and the likes.

Paul
2007 MS3 Blue Mica
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post #6 of 12 (permalink) Old 06-29-2013, 12:50 PM Thread Starter
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Weight is the same. Climate on those track days are very similar
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post #7 of 12 (permalink) Old 06-29-2013, 05:17 PM
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Maybe exceptionally good gas for that best time, or slightly worse after that?


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post #8 of 12 (permalink) Old 06-29-2013, 10:28 PM
PZ
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Let's try this again. If nothing else is significantly different, then it is the engine.

Either:

1. You are down a few HP from the OEM engine (is this a rebuild or a Mazda sourced new engine)

or

2. The new engine has more internal drag than the old engine, which means it will not spool up as fast, costing you some speed at the end of a long straight.

or

3. Both


You lost 3 mph at the end of a straight. Big deal. Personally, I think it is #2 and you will get those rpm's back as the engine wears.

2008 New England Region SCCA HS Class Champion
2008 New England Region Stirling Moss Championship co-winner.
92HS - 2007 Mazda 3s Sport Sedan -2006 Miata Wheel, 16x6.5, 15lb w/ Hoosier A6 245/45R16 (f) and 225/50R16 (r) MS Accessory Sport Shocks
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post #9 of 12 (permalink) Old 06-30-2013, 02:08 PM
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How many miles are on the motor? Are you using the same oil as well?

Also someone asked if it was a Mazda OEM motor.... or was it built?

Paul
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post #10 of 12 (permalink) Old 06-30-2013, 05:42 PM Thread Starter
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It's a new Mazda Motor.
There must be some misunderstanding, the best time is clocked with the new motor after replacement. It was the first track day after replacement

Subsequent track days gave me lower top speed. Although its 5kmph, it's fairly significant when it comes to time attack
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