Metro 3-cyl General Info

[MetroMPG]

Originally Posted by JanGeo

Ok the vacuum is not going to be very high ... My Geo didn't show a high vacuum until I went down a hill with engine braking and even then with crank ventilation it didn't get very high

What's "high"? Some numbers would help!

[95metro]

Okay. Darin, I think your Blackfly's vacuum is fluctuating between 19 and 20 in Hg. Here's how I figure that.

A decrease in manifold vacuum means an increase in manifold pressure (acceleration).

14.7 psi = atmospheric pressure

30 in Hg = perfect vacuum (that's just for reference)

Your MAP sensor reported 4.7-5.1 psi. This should be manifold pressure. The pressure difference:

14.7 - 4.7 = 10 psi
14.7 - 5.1 = 9.6 psi

Should be vacuum.

10 * 2.036 = 20.36 in Hg
9.6 * 2.036 = 19.54 in Hg

At least I think this is correct. I haven't found info to absolutely confirm it. But if it is then mine is low in comparison.

EDIT: I'm thinking that my lower vacuum probably has more to do with engine age/mileage than with any possible problems. I've been considering a rebuild for some time. Perhaps by next year...

[JanGeo]

Oh sorry Yeah gauge is not here so . . . mine was marked in Green for highest then yellow and red for lowest I seem to recall mid 20's for down hill in the Rambler flat head 6 idle at the green yellow line which was I think around 20-22 inches 26 for a high - If I could find it I could remember it better. Tried to accelerate in the 15 inch range. When I used it in the Geo it was always so low it wasn't worth using it - engine was always lugging to reduce pumping losses. I remember when I went downhill in the Geo with it the vacuum did NOT get very high - EGR and PVC were working. Maybe 23 or 24 for a high down hill in the Geo.

[95metro]

Originally Posted by JanGeo

When I used it in the Geo it was always so low it wasn't worth using it

Yeah, mine is typically in the 5 in. Hg or less range while I'm accelerating. The engine is small and needs a lot of air to get the vehicle moving. I'm thinking that the G10 is pretty sensitive to wear and tear over time. They keep running, but they sacrifice efficiency.

[JanGeo]

I think we all need photos of our tail pipes!

If I get into the basement later today I will see if it is there. Would be interesting to see what the Scion xB is sucking for air...don't know were a vacuum line is however the engine has a cover over it.

[95metro]

The transmission/gear oil discussion kind of peaked my curiosity so I've done a little research.

Apparently gear oils and engine oils are actually the same viscosities, but are given different measurements by the SAE to differentiate their uses:

SAE gear and engine numbers cover the same range of viscosities; for example, an SAE 30 engine oil has approximately the same viscosity as a SAE 85W gear oil. This is because the formulation of engine oils is very different to that of gear oils in the automotive industry. An engine oil is far more stressed than a gear oil because it must cope with combustion by-products and blow-by gases which severely degrade the oil. As a result engine oils contain a much wider variety of additives than gear oils. Although not ideal, an engine oil will function in a gearbox while a gear oil will destroy an engine.

Quoted from: http://www.wearcheck.com/literature/techdoc/WZA007.htm (stupid layout on the website, but good info)

A pdf on Redline's website confirmed this by helpfully stating the gear and engine viscosities. 75W90 gear oil is similar to 15W40 motor oil, but the GM/Penzoil Synchromesh is actually closer to 5W30 motor oil viscosity.

Here are some fluid comparisons:

Legend:
Pour Point: Pourability at temperature (°C)
Viscosity Index: The higher the number, the less change in viscosity throughout temperature range
cSt @ 40: Kinematic viscosity in centistokes at 40°C
cSt @ 100: Kinematic viscosity in centistokes at 100°C

Short bit on kinematic viscosity:

In order to determine the differences between the three oils one has to look at the kinematic viscosity of each lubricant. The kinematic viscosity is essentially the amount of time, in centistokes, that it takes for a specified volume of the lubricant to flow through a fixed diameter orifice at a given temperature.

Quoted from: http://www.synthetic-oil-tech.com/d....weight_oil.htm

Penzoil 75w90 GL-4 (basically what the Metro manual calls for, but it's not the correct stuff!)
http://www.pzlqs.com/Tech/Pdsheet/Do...E75W90GL-4.PDF
Pour Point: -42
Viscosity Index: 149
cSt @ 40: 108
cSt @ 100: 15.3

Penzoil Synchromesh (apparently this is the GM synchromesh)
http://www.pzlqs.com/Tech/Pdsheet/Do...omeshFluid.PDF
Pour Point: -50
Viscosity Index: 208
cSt @ 40: 41.6
cSt @ 100: 9.08

Amsoil Synchromesh 5W-30
http://www.amsoil.com/StoreFront/mtf.aspx
Pour Point: -45
Viscosity Index: 194
cSt @ 40: 47.1
cSt @ 100: 9.6

Royal Purple Synchromax
http://www.royalpurple.com/prodsa/scmax.html
Pour Point: -51 (their PDF states -40...???)
Viscosity Index: 196
cSt @ 40: 35.3
cSt @ 100: 7.7

Redline MTL (70W80 gear or 5W30 engine)
http://www.redlineoil.com/pdf/6.pdf (pdf for a number of Redline transmission fluids)
Pour Point: -50
Viscosity Index: 183
cSt @ 40: 56.2
cSt @ 100: 10.6

Mobil 1 5W-30 Synthetic (engine oil - just threw it in to see the difference)
http://www.mobil1.com/USA-English/Lu...bil1_5W-30.asp
Pour Point: -54
Viscosity Index: 169
cSt @ 40: 64.8
cSt @ 100: 11.3

EDIT: The characteristics of some of these MTFs is very close to some 0W30 motor oils. Looks like krousdb's method may be perfect...???

https://www.amsoil.com/storefront/tso.aspx

[Gary Palmer]

Originally Posted by JanGeo

Oh sorry Yeah gauge is not here so . . . mine was marked in Green for highest then yellow and red for lowest I seem to recall mid 20's for down hill in the Rambler flat head 6 idle at the green yellow line which was I think around 20-22 inches 26 for a high - If I could find it I could remember it better. Tried to accelerate in the 15 inch range. When I used it in the Geo it was always so low it wasn't worth using it - engine was always lugging to reduce pumping losses. I remember when I went downhill in the Geo with it the vacuum did NOT get very high - EGR and PVC were working. Maybe 23 or 24 for a high down hill in the Geo.

Additional reference point: I've been running a vacume gauge on my 89 Civic. I typically see about 22 at idle. On deceleration I will see about 26. On accel, I typically try to stay 13-15, although at 60mph, it takes about 13-14 to stay at speed. I know it's not a 3 cylinder, but the number's are fresh, since I currently have the gauge hooked up.

[95metro]

I should check vacuum on my Aunt's 1.3L 4-cyl Metro. I wonder if it would read a fair bit higher than the 3-cyl?

If we consider MetroMPG's Blackfly as the "standard" or "best" at 19-20 in. Hg then it could be that most larger engines will read 22.

Of course, this could also point to the possibility of small and large engines reading lower and "mid-size" engines reading higher. Perhaps 4-cyl engines are more efficient overall. It's possible that the 3-cyls pumping losses may reduce it's actual efficiency percentage.

But, I'm just rambling hypotheticals.

[Gary Palmer]

Well, while your rambling, I had one other consideration. My car has new ring's and a competely rebuilt head, so it might be a little higher just because it's tighter?

[95metro]

I think you're right. That's why I considered wear-and-tear into my 202,500 km engine compared to MetroMPG's <5,000 km engine (What are you at, Darin?).

I'm certain an engine rebuild would increase FE fairly dramatically.

EDIT:

compared to MetroMPG's <5,000 km engine

Make that < 10,000 km. Man, that's not even broke in yet!