dealer is telling me no power loss?

[mpoyner]

If you'll recall, I just got a 95 Q45a a couple of weeks ago, and feel that the engine doesn't have the power one would expect. I recall someone here saying "the Q45 is a FAST car," when I asked about this before. It is smooth, but just does not feel very strong or fast to me, until I am around 40-50 mph, with the engine revving. That's when the power seems to kick a little and the car is noticeably pulling faster. Sometimes I can floor the pedal (from a stopped position), and it barely starts out and then gradually gains more and more power. At first, though, it feels like a 4-cylinder to me.

The dealer checked it our for me and his comments on paper are "Performed engine diagnostics/power balance test/alpha fuel/mixture ratio test -- Vehicle operating to factory specifications."

Does this mean it's in my head, or would these tests only show up a couple of the causes for power loss, but not really prove that the car is operating at full power?

I'll put the results of his printout here for Q45Tech and others who understand these things better than I.

Mixture Ratio Test Results

CMPS-RPM(POS)-----------2049rpmMAS AIR/FL SE-------------1.8VCOOLAN TEMP/S-----------86 degrees CelsiusCLSD THL POS-------------OFFINJ PULSE ------------------2.2msecINJ PULSE-R----------------2.2msecO2S1 MAX-------------------0.8VO2S1 MIN-------------------0.1VO2S1 COUNT---------------9O2S1 (B2) MAX-------------0.8VO2S1 (B2) MIN--------------0.1VO2S1 (B2) COUNT---------11A/F ALPHA-------------------101%A/F ALPHA-R-----------------102%

Power Balance Diag Result

Reference DataNo.1-----59rpmNo.2-----60rpmNo.3-----57rpmNo.4-----64rpmNo.5-----60rpmNo.6-----66rpmNo.7-----63rpmNo.8-----69rpm

Base DataCMPS-RPM(POS)------------843rpmCOOLAN TEMP/S------------85 degrees Celsius

I have one other question: is this car made to be shifted from 2-3-4 manually to achieve power, such as some new sports sedans are? I don't presently do that. Maybe that's why I don't get the performance? I tried it once tonight and certainly had more off the line acceleration, but I suspect I shouldn't have to do this, hmm?

[PalmerWMD]

your power balance test looks very good.Some thins can';t be easily found though.

A well running Q will never generate complaints about power.I ahve had PPL drive my 94 Q with my weak engine that was dpwn 50-70 hp and comment on it being a powerful car and that was also a somewhat slow year.

I could write more but its late; teh Gurus will pick up the rest.

Fred...

[greg_atlanta]

The Q is a highway cruiser, but it's not very perky around town. It only drops into first gear if you're going under 25 mph (roughly), so when you punch it anywhere over 25 mph it will stay in 2nd gear until 2nd gear redlines around 80-85 mph.

That's why you can be going 70 mph, punch it and WHOOOSH!!! (drops into 2nd)

Q45a is a little heavier than other Q45's and the active pump eats up a little power.

Just a matter of getting used to the car. Notice most new luxoboats have gone to 5 or 6 speed transmissions to give better performance around town. MB is coming out with a 7 speed automatic for S-class and M-class pretty soon.

[AZhitman]

WOW - I wish my PB numbers looked that good!

I'm gonna start pissing and moaning about mine to my dealer tech again....

[Q45tech]

What I do is use the 4 seconds of Consult memory storage to record a stream of data from 3500 rpm to redline [takes some practice to not hit record to early and drive the Q WOT.....usually takes 2-3 tries for me to get the data I want hard to find a place that is safe [where somebody can't pull in front of you] and law free......in town.Then I snapshot in 500 rpm increments and hand graph the changes thru the acceleration. Injector open time [2-11 millisecs] and ignition advance vs rpm vs MAF...........looking for problems that ecu might encounter. Ignition advance vs rpm is the thing to study as setting the base timing too high will cause knock in Summer and the power is way off till the ecu recovers. Setting the base timing too low will make the Q feel sluggish.A real accurate 15 degrees works best year around. Not to say that 17 degrees won't work in winter but you would have to change it back in April. Ambient air temp is critical!The Q can stand 27 degrees total at 6,000 rpm [28 at 6,500-7,000] but only 22-23 at 4,000.

The test you provided looks like an inbay test at 2,000 rpm in park.The O2 counts 9 or 11 are good as 10 switches per second indicate good accurate sensors and ecu responses.

I know my engine by heart and can compare it to other 90-93Q on an rpm by rpm basis.The problem is I don't have a PERFECT 94-95 active Q to compare with others. We all say they are down on power but pump losses and weight can't amount to much over 0.3 seconds in zero to 60 or quarter mile compared to a standard Q of same year group.Traction control is a big variable and non oem hard tires can cause this to engage when it shouldn't limiting acceleration.

Dyno testing is so inexpensive even if it is just a speed vs torque graph in 3rd gear or better yet the on the level highway rolling 50 mph to 80 mph locked in 2nd gear stop watch test [multiple times to average [5.4-6.5 seconds]......zero to 60 [6.7-7.5] or even 80 [10.2-12 secs] [are ambiguous because of launch and tires and driver].

Most Q are pretty slow from zero to 30 mph [~~ 3.3-3.7 secs]whereas a modern 5/6 speed AT [MB SL500= 2.70 secs][SC430=2.65] [BMW 745= 2.3] due to the Q's suboptimal 1st gear multiplication necessary to get a smooth wide 2nd gear from 50-85/90/95 mph.

A within 12 rpm PB is good and the standard I shoot for, as much beyond this [25 rpm] will show up as a less than perfect idle. 37 rpm variance can be felt even by the average owner...........due to rounding in the Consult especally the Consult I [reads in 12 steps], it is rare to see a perfect PB but if you do it 3 times you can find one on a perfect Q.

[mpoyner]

So, what your saying is, this testing didn't necessarily tell me much, but the signs are good that the engine is functioning properly?

It sounds like maybe I have expected too much off-the-line acceleration? There are times, however, that there is a noticeable slowness. Maybe this is due to the traction control engaging when it shouldn't? If you all recall, when I got the car, the Slip and TCS lights were on and I discovered that it was disconnected under the hood. I reconnected the wire harness and the lights went off. Maybe it's not functioning properly and that's why it was unplugged? That may be why I have sometimes no acceleration off the line?

[Q45tech]

Measure with a stopwatch and report the results . The word slow is so relative. Where does it fit in 0-30;60;80 [and 50-80] mph numbers I gave you earlier?

[elwesso]

I am experiencing the same thing you are describing.... A really low power from the get go, but once you get past 3500 RPM, it just shoots off like a rocket, but its a dog up until there......

I suppose if they did a PBT then they would have seen if the ECU was retarding the timing, or the knock sensors were bad!

[sultan]

I suppose if they did a PBT then they would have seen if the ECU was retarding the timing, or the knock sensors were bad!

the PBT won't tell you that, but other diagnostic screens will. the PB just measures drop in RPM, retarded timing wouldn't affect that (right?).

i did the PBT on 6 of my cylinders today, came out good. we were using a diagnostic tool a local guy is working on, it uses a palm pilot. i believe it works just like the consult. it is known to work on the 300zx, 240sx, and sentra, but i guess it's not set up for eight cylinders. it only read one of my O2 sensors, but both work (throws no codes for O2 sensors) and i think it said ignition timing was 45 degrees BTDC at idle. unfortunately someone was borrowing the guys consult so we couldn't try that.

[reggiegsd]

Remember, its August and its hot outside. Does the car run better on cool damp evenings? There is an obvious difference in my '94 Q's performance at 65 degrees verses 90 degrees.

[Q45tech]

But 1% per 11F is hardly noticeable even 120F ambient vs 70F wouldn't be 5% [ 15 lb/ft] ............but 3-5 degrees reduction in advance would be severe from [205-215F] coolant temp increase!

Having the AC on [besides the 4-5 HP drain] signals the ecu to use a middle equation for rate of advance even if the coolant temp is at the 194F normal limit.[where no extra amount is subtracted].

Ac on, 200F coolant, and 100F ambient makes the car feel 50 HP lighter.

When you study the idle injector time 2.2 msecs and turn the AC on it jumps to 2.6 msecs...........since the low flow/dead time/ramp up is 1.5 millisecs .........this is the functional equivalent of a 27-30% fuel increase over no AC idle.

By definition there is zero extra HP at idle or the idle speed would increase and increase and increase.

Sure the ecu cuts the compressor at WOT but the on signal is still in place .Turning AC off at HVAC panel is the only way to get out of summer mode........then you only have the reduced air density and the coolant temperature to worry about

[greg_atlanta]

90-93 Q has stronger 1st gear than 94-96 Q.... that makes a difference. But 90-92 Q were programmed to start in 2nd gear on normal starts.

[mpoyner]

I buried a separate question at the bottom of my novel-length topic starter :rolleyes , so you guys probably missed it.

Here it is again: what about manual shifting the auto transmission. Is there a wear-and-tear issue with that? Or, was this transmission made to allow you to do that, like some other luxury sedans have been?

I experimented yesterday and found that if I start with the transmission manually shifted into second gear, first seems to feel stronger, for some reason; second does, also. And it is a smooth manual shift into third after that, with excellent performance all the way through from 0 to 80mph.

I only did this a couple of times because I don't want to put undue wear on the transmission if it isn't made to accept that.

[Q45tech]

You are not manually shifting the transmission, you are signaling the tcu that you want it to shift at a different time than the program. It will attempt to comply within safety parameters!The TCU then applies a voltage to one of 3 solenoids and the internal valve body tries depending on ATF pressure to follow the wishes of tcu.

All the modes are graphed in the FSM.

[mpoyner]

you're absolutely right! "Manually" is not the word I should use.

So, in your opinion, is it a bad idea to shift this way on occasion.

Also, should I really be getting the same performance whether I do it or not?

[Q45tech]

I do it all the time.............use 1,2,3, and 4th not necessarily everyday.

[mpoyner]

thanks for all the replies!

You are a huge help to Q newbies like myself and we really do appreciate it, even if it seems we take advantage and ask to many questions sometimes.

Matt