engine health/power check

[hardtailer]

popped across the border with a mate in his T350c (3.6l speed six, 3,46:1 diff, 255/35R18 rear tyres) to Germany to legally (& traffic permitting) do some gps-logged acceleration runs.
This is what we found:

______speed lo (mph)
split(s) speed hi (mph) increase (mph)

---

________35,05
0:00:07 123,97 88,92
________32,13
0:00:06 90,23 58,10
________50,15
0:00:06 115,58 65,43
________3,98
0:00:06 47,16 43,19
________14,73
0:00:05 59,22 44,49
________30,14
0:00:04 64,75 34,61
________97,44
0:00:05 124,03 26,60
________0,56
0:00:03 63,32 62,76 --> gps signal seems unreliable
________1,74
0:00:04 67,11 65,37
________47,04
0:00:05 73,70 26,66
________73,57
0:00:10 117,20 43,62

Unfortunately I can't provide what gear each 'run' was done in (either 4th or 5th, some will obviously have been 5th) but we would love to hear what sort of times people achieved who have logged trackdays.

Thanks in advance

[Sevenman]

Interesting mix of times.

Speeds measured to 2 decimal places, but time to one second is probably not the combination you would want, but I guess that is how it outputs the data. The unit should be able to measure time very accurately, speed could be within 1 mph.

35 to 124 mpg in 7 seconds seems quicker than might be expected for a stock car, was that the red-line in 3rd?

The line below it shows 32 to 90 in 6 seconds, which might sounds reasonable but is a low slower than the first.

I think gear information would be helpful - some of it may be guessed from the data, but guesswork doesn't add accuracy

Another way to do an engine health / power check would be to do a dyno run, which gives clear figures and an air/fuel ratio. As long as you remember to add 15% to TVR Power wheel figures to get flywheel and take 10% off Surrey Rolling Road fywheel figures (special unnecessary-debate starting adjustment factors).

[leef44]

it's difficult to make out anything from this. To go from 35 to 124mph in 7 seconds seems impossibly quick in any gear while 4 to 47mph in 6 seconds seems very slow. But like you say, you're not sure what gears you were in while mainly in 4th or 5th.

I'd hate to think that the ones starting from 1mph and 4mph were starting from 4th gear!

Anyway, I guess you are asking others to see if they have any times to compare to help you sense check your data.

[hardtailer]

Thanks for your replies and comments.

The datalogger (My Tracks app on Galaxy S2 smartphone) seems to have a 1 Hz logging rate that's why it turns out the way it did with 'odd speeds for whole seconds'. So seconds are 1'00" if you will.
I exported a gpx file and used a gpx editor to get the samples I posted. Turns out that the 35 to 124 mph in 7 seconds is false, judging by the trace in the app itself as it did not show these speeds. Turns out that it was a sample involving a fly over to get from one motorway onto the next and driving underneath screwed up the speed measurement so that one can be discarded. Strange that the export mangles some numbers...

5s from 97,44mph to 124,03mph must have been in 4th gear and seems a solid measurement.

the 6mph one is also not to be found in the trace within the app, only in the export so ditch that one too...

Ok, this is obviously not a dependable way to guesstimate engine health.

Edited by hardtailer on Sunday 28th April 12:42

[leef44]

hardtailer said:

Ok, this is obviously not a dependable way to guesstimate engine health.

Edited by hardtailer on Sunday 28th April 12:42

But it still good to get some data. Some of it makes quite impressive reading. High speed acceleration is pretty impressive in your car.