Today we had an opportunity to compare my Q [256k] with the perfect under 50k 1990Q of another member. Same tire diameters [235/15 vs 255/16] same loaded weight, same gasoline level, same road section, probably within 2-3F [60F]ambient,950 'AMSL. Both trannies had the same under 50k mileage one new in 1990 another a factory reman [mine] . Both oem factory air intakes. Both TB cleaned. Close as one could get to being identical except for mileage, equal age [time] engines.Mine had Mobil 10w30 the other conventional oil but synthetic ATF vs mine conventional......should have washed/equalized.
After doing data logging on the 4k-6.5k range to check ecu/inj/system performance after a chain guide replacement.
The ranges were 5.8-6.2 seconds[stop watch method floored at 40 mph] both cars.
My absolute best time used to be 5.3 seconds [but the ambient was colder when accomplished and that was with 100k miles not 256k.Also a 4.44 volt MAF reading was the orginal peak.......0.09 volts is significantly more flow at the top [might be 5-8% more flow].
We attribute the 0.3 sec difference to my ecu vs oem ecu [side by side comparsion of rpm data showed mine had 2-3 degrees more advance in the acceleration range.........the injector opening time [mine a tiny bit learner] and MAF peak reading [4.35 volts] were essentially identical.
We probably should have done 5 runs each to average variances but I tried to be consistent.
Q 50-80 mph acceleration
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Q45tech
- Moderator
- Posts: 14296
- Joined: Tue Apr 30, 2002 3:19 am
- Car: 1990 Q45 342,400 miles 22 years ownership with original engine
1995 G20t 5 speed 334,000 miles 16" 2002 wheels - 205/50/16 Sr20ve vvl
Another interesting fact is the week before, I had changed my spark plugs at 56,000 miles - 3.2 years]. The plugs looked rough from some blowby and oil/deposits.We did 4 per day [limited time] and did compression test at the same time...............all readings were below factory spec but were done with the engine cold [maybe 75-100F] so the rings were not sealing well COLD............some were below 100 psi [145 psi minimum].....adding oil brought some as high as 220 psi.
Yet a warm [176F] power balance is/was perfect. Rings seal ok once heat expanded.
When you are dealing with high mileage Q engines different criteria need to be evaluated.Idle smoothness, power balance, oil burning, smoke on WOT/idle/startup, acceleration or dyno test.
My motor mounts were changed at 120k [6/98]...........5.3 years and or 136k seems to be the life limit as we measured displacement under load vs new units.
Yet a warm [176F] power balance is/was perfect. Rings seal ok once heat expanded.
When you are dealing with high mileage Q engines different criteria need to be evaluated.Idle smoothness, power balance, oil burning, smoke on WOT/idle/startup, acceleration or dyno test.
My motor mounts were changed at 120k [6/98]...........5.3 years and or 136k seems to be the life limit as we measured displacement under load vs new units.
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Q45tech
- Moderator
- Posts: 14296
- Joined: Tue Apr 30, 2002 3:19 am
- Car: 1990 Q45 342,400 miles 22 years ownership with original engine
1995 G20t 5 speed 334,000 miles 16" 2002 wheels - 205/50/16 Sr20ve vvl
14 years of dry starts [before the oil pressure comes up] can take there toll..............even with maintenance and Mobil 1.If we average 26 miles per start that would be 10,000 starts vs say 250-500 on the Mobil 1 Million Mile Test. {they left it to idle every driver change} only stopping for oil changes every 3 days.
Much of my Q's early life to 50k had 5-10 mile driving cycles. Then it changed to 60 mile [many 200 milers] for the next 100,000 miles, now somewhere in between.
If the engine/car has lost 0.5 seconds in the test that might equate to a 30 RWHP loss............but we have to assume the 50k 90 engine was meeting spec so the who knows.Change stretch is a variable as is MAF voltage accuracy.
Human errors in the stop watch method might be 0.25 seconds.
The point is high mileage engines don't have to be slower.
But a G35 C 6 MT at 5.2 secs [best 50-80 C/D 01/03] might beat me if the driver was good and didn't try it in 4th gear.
Now when it gets to 6.3 secs time to change engines, I'll accept 10% but not 20% down.
I can adapt to 2 car lengths in a pass but not 4 car lengths.
Much of my Q's early life to 50k had 5-10 mile driving cycles. Then it changed to 60 mile [many 200 milers] for the next 100,000 miles, now somewhere in between.
If the engine/car has lost 0.5 seconds in the test that might equate to a 30 RWHP loss............but we have to assume the 50k 90 engine was meeting spec so the who knows.Change stretch is a variable as is MAF voltage accuracy.
Human errors in the stop watch method might be 0.25 seconds.
The point is high mileage engines don't have to be slower.
But a G35 C 6 MT at 5.2 secs [best 50-80 C/D 01/03] might beat me if the driver was good and didn't try it in 4th gear.
Now when it gets to 6.3 secs time to change engines, I'll accept 10% but not 20% down.
I can adapt to 2 car lengths in a pass but not 4 car lengths.