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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... |
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.
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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. |
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: Quote:
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: Quote:
Penzoil 75w90 GL-4 (basically what the Metro manual calls for, but it's not the correct stuff!) https://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) https://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 https://www.amsoil.com/StoreFront/mtf.aspx Pour Point: -45 Viscosity Index: 194 cSt @ 40: 47.1 cSt @ 100: 9.6 Royal Purple Synchromax https://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) https://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) https://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 |
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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. |
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?
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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: Quote:
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