Oil in cylinder 5 (Page 4/7)
pmbrunelle JUL 16, 08:22 AM
When it comes to estimating engine performance, quarter mile trap speed has a better signal-to-noise ratio.

0-60 mph is largely affected by traction and driver technique.
1985 Fiero GT JUL 16, 08:33 AM

quote
Originally posted by pmbrunelle:

When it comes to estimating engine performance, quarter mile trap speed has a better signal-to-noise ratio.

0-60 mph is largely affected by traction and driver technique.



Yes, I'm well aware of that, but I have nowhere I can safely/legally do a 1/4 mile test, I do all my 0-60 in the same weather, on the exact same specific stretch of road and I do several runs, noteing the best ones only after 2 others that are ballpark close (6.72 was the perfect one I got, I also got 6.78 and 6.82, before I considered it to be in the 6s). In the last year, I estimate I've done 60-100 of these runs, last year I was thrilled with an 8.4 second 0-60 haha!
pmbrunelle JUL 16, 08:47 AM
What kind of test/measurement setup do you have?

Myself, for doing a rough engine performance evaluation without going too fast, I have done a 2nd-gear pull (clutch fully engaged the whole time) from X to Y RPM (such as 2000 to 6000), measuring the time it takes to go from X to Y.

This eliminates the clutching/shifting variables.

[This message has been edited by pmbrunelle (edited 07-16-2024).]

1985 Fiero GT JUL 16, 09:07 AM

quote
Originally posted by pmbrunelle:

What kind of test/measurement setup do you have?

Myself, for doing a rough engine performance evaluation without going too fast, I have done a 2nd-gear pull (clutch fully engaged the whole time) from X to Y RPM (such as 2000 to 6000), measuring the time it takes to go from X to Y.

This eliminates the clutching/shifting variables.




Yeah I've wanted to do some testing like that as well, but I haven't gotten around to it haha. My measurement setup is the app "dragger" on my phone which auto logs a run, and starts the timer upon acceleration felt by the phones accelerometer, using the highest resolution GPS settings. I always check manually after a good run, to make sure it didn't start the timer late or otherwise effect the time.

The 6.72 is probably the most accurate run I've ever done, the speed is exactly 0 at 0 seconds, and it has a very close point to 60 to extrapolate from
1985 Fiero GT JUL 16, 03:55 PM
Just got an even better run, felt absolutely perfect, not sure which numbers to believe, this one is slightly less precise, the "number"it gives me is 6.16 seconds, but looking at the GPS graph, I would estimate closer to 6.38 seconds. Definitely under 6.5 seconds, regardless of the way it was calculated.


(First GPS measurement happened half a second in, but the timer starts when the phone feels acceleration, not when GPS measures a speed, so should be accurate on that end)

(Previous GPS ping was 58.71 MPH, at 6.05 seconds, so the real time is somewhere between 6.05 and 6.38, closer to the higher number though)

Interesting, I notice a pattern, my slower "fast" run above hit 0.77Gs acceleration, right off of 0, and decreased from there (dumped the clutch a little harder), my fastest run, I slipped the clutch the tiniest bit, keeping the rpm more steady, which appears to have helped some, although I only got 0.54Gs acceleration, it was spread out over much more of first.

[This message has been edited by 1985 Fiero GT (edited 07-16-2024).]

pmbrunelle JUL 16, 07:17 PM

quote
Originally posted by 1985 Fiero GT:
Interesting, I notice a pattern, my slower "fast" run above hit 0.77Gs acceleration, right off of 0, and decreased from there (dumped the clutch a little harder), my fastest run, I slipped the clutch the tiniest bit, keeping the rpm more steady, which appears to have helped some, although I only got 0.54Gs acceleration, it was spread out over much more of first.



I don't think that the app measures enough points for you to analyse the runs in detail like this.

We don't see the gearchanges, where we would expect no acceleration, or even slight deceleration.

If anything, you probably have greater peak acceleration than the numbers indicate, because the app measures a more averaged acceleration which includes the zero-acceleration gearchanges.

I think that for no-gearchange measurements, the small number of points the app measures would be less of a limitation.

********************************************************************************

What is this at 49 mph?


A gearchange?
1985 Fiero GT JUL 16, 07:22 PM

quote
Originally posted by pmbrunelle:

What is this at 49 mph?

A gearchange?




Yes, that is 2-3, the other run pictured has the shift from 1-2. Depending when the GPS points are taken it can be more averaged out or very visible like those, and yes the acceleration is definitely very vague and not useful, but I personally tried 2 different techniques, and the second gave me a quicker time, and felt much better for the launch, albeit much harder to reproduce haha.

The app also gives me GPS acceleration, which has much more points, the acceleration estimate is just a smoothed simpler version that is the default, just as it has a smoothed speed line, I choose speed by GPS as that is most accurate, acceleration I chose the another line for purposes of demonstration, you can clearly see the gear changes in this

(Slower run)

(Fastest run)

I don't know why I'm the fastest run, first gear looks so slow, and second gear it just took off, compared to the slower run. It definitely isn't perfect, but it beats using a stopwatch and the speedometer, while driving!

[This message has been edited by 1985 Fiero GT (edited 07-16-2024).]

cartercarbaficionado JUL 16, 07:32 PM

quote
Originally posted by 1985 Fiero GT:


Interesting, I notice a pattern, my slower "fast" run above hit 0.77Gs acceleration, right off of 0, and decreased from there (dumped the clutch a little harder), my fastest run, I slipped the clutch the tiniest bit, keeping the rpm more steady, which appears to have helped some, although I only got 0.54Gs acceleration, it was spread out over much more of first.



yeah I've noticed that too. it's a completely normal behavior because the engine is free to make more power keeping the revs up while the transmission isn't transferring all of its speed and power directly meaning its acceleration after it begins moving when the engine is held at 2000 rpm is much much faster. (to the tune of 40 mph across a 4 way if you do it right)
pmbrunelle JUL 16, 07:32 PM
A 2-3 shift at 49 mph with 205/60R14 tires and the M17 transmission suggests you shifted at 4851 RPM.

Why the short shift? The Fiero 2.8L V6 continues to generate power above that RPM.
1985 Fiero GT JUL 16, 07:34 PM

quote
Originally posted by pmbrunelle:

A 2-3 shift at 49 mph with 205/60R14 tires and the M17 transmission suggests you shifted at 4851 RPM.

Why the short shift? The Fiero 2.8L V6 continues to generate power above that RPM.



Well... I don't like the higher rpms haha, I don't know, but 5000 is usually the highest I'll take it.

Also, factory size 215/60 R14 (not that that makes a difference in rolling diameter).

I also edited my previous post with more info.

[This message has been edited by 1985 Fiero GT (edited 07-16-2024).]