Here is a Re-post of the old Power Change thread. (It's still in my cache) Power Change Author Topic: Power Change Chally I did a few tests on my 94 Q45 with the timing & had some weird results.I set the Timing at 10 deg, & when it was just Hot, 5 mins running, it went absolutely crazy. Could drag off most things. When the car ran longer, the performance reduced considerably, to the point it was woeful. (not to mention dangerous)

Re-set the timing to 16 deg, & the Just Hot performance was a bit better, but the performance STILL dropped off, the longer the car drove up to about 10 mins, where it stayed the same no matter how long you drove.

The difference in performance is from smoking the tires easily to having to really flog it to do the same.

Is this a normal thing for these engines, or is there something wrong? eg: coolant temp sensor etc.

Any help is appreciated.

Chally

Q451990Member posted July 20, 2002 10:23 AM Just remember that in hot ambient temperatures the car will retard the timing more often to reduce knock. As the engine really heats up it's more likely to knock, so it'll back the timing off as it detects it. That's probably what you're getting....Heath

Q45techMember posted July 20, 2002 11:14 AM The coolant temperature as read by the ecu shown on a Consult is the key to setting timing correctly.The coolant temprature should be 176F- to no more than 185F when you adjust the CAS.190F is where the ecu starts reducing ignition advance and every 5 degees F the coolant rises 1 degree is removed from the summing equation [initial as set by CAS + load advance + coolant temperature [+5 to zero to minus 7 degrees] minus knock count plus rpm advance.The total timing advance can be 15 DBTDC to 44 DBTDC depending on the calculations of all the variables. 40 at cruise 22-28 at WOT.

I been HAAARPING on coolant temperature for a YEAR trying every way I know to get owners to understand the functions.Setting the CAS a detailed proceedure outlined in you SERVICE MANUAL must be followered in rigorous detail!The choice of 13, 13.5, 14, 14.5, 15, 15.5, 16, 16.5 degrees with the IAC disconnected at 670-695 rpm in Neutral no AC is critical!

I have seen Q motors go crazy because the coolant temp was 210F [a 4 degree base timing reduction] and the CAS was set at 17 degrees and the normal 5 degrees of knock sensor reduction didn't do it so the ecu pulled out 5 more due to summer heat and gasoline: so +17 + [-4]+[-5]+[-5]equals only 3 degree BTDC so the engine was getting +3 + [+8 to +12] = 11 to 20 when normal would be 22-28 [in a 4,000 to 6,500 rpm acceleration].

The only way to know what is best is to use the Consult to monitor and record the Ignition Advance vs coolant vs rpm vs injector opening time. Make a half dozen runs and set the CAS accordingly.

The problem is the gasoline used may be different, the motor condition may have changed from new, the knock sensors maybe be cracked enough to not throw a code but to behave differently than new [check their resistance 550k] with a different sensativity [plus worn motors make more noise which may be interpreted by ecu as knock]. Dirty intake system means less air than the ecu expects, deposits in combustion chamber and on valves [exhaust valve guide wear meaning less heat removed..you name it a 100k motor is not NEW!

Another thing to look at is the coolant temp sensor may have an insulative film caused by not changing coolant every year. The resistance to REAL actual temperature may be off a little [the coolant might be hotter 1-5-10F] than it reports to the ecu or colder?

Chain stretch will change the position of the CAS in terms of the crank up to 2-3 [more?] degrees!

AZhitmanMember posted July 20, 2002 03:52 PM MAN I love these posts! Another incredibly informative missive by the man.I'm printing this one and taking it to the dealer next visit. Thanks Dennis.

Q45techMember posted July 20, 2002 04:59 PM Because of variable valve timing and tuned Helmholtz induction the Q engine acts like two different engines one above idle to 4600-4800 rpm and another from [4600-4800 to 6900] rpm. Probably more like 4 engines if you consider idle and the 1,750-2,000 rpm range.The ignition timing is calculated every 12.5 rpms until 4,000 rpm where the calculations get extended to every 50 rpms [ecu processor speed vs accleration time].

Anyway on older engines on an engine dyno you loaded the engine up and tweeked the distributer to find the advance that yielded max HP at each rpm increment [say every 100 till redline]. Still done today but the software is adjusted.

The 4,000 rpm point is the torque peak [by definition the point of maximum VE [volumetric efficiency] where the filling of each cylinder is maximum! 32 valve engines act like they are 20% larger than 16v engines because the extra valves have a very low restriction [curtain area] and they suck in 20% more air at the torque peak [they have way too large valves and runners at 1500-2700 rpm so they are less efficient in this range than 16 V engines!

The {first engine} might need 22 degrees at 4,000 rpm then rise incrementally to 26 degrees when the 4600-4800 shift signal occurs on the VVT then drop back to 23-24 degrees at 5,000 and undulate upward till the twin HP peaks at 5500 and 6,000 [27] and get to 27-28-29 at the VE cliff of 6600 rpm then lock at 28 there after to redline.

An old rule of thumb: says you can [should] advance the timing 1 degree for each 500 rpm from the torque peak to the HP peak rpm as the VE falls [that rule won't work [on a Q] and would be 2 degrees light due to the tuning after the VVT shift.

The difference in advance between regular and premium gasoline can be 3-4-5 degrees.As you lean the engine out to account for the lower VE from the Torque peak to HP peak and especially beyond you have to watch the ignition advance as the flame speed varies as a function of mixture [how much extra rich beyond 14.7 to cool combustion]....kind of like how the speed of sound varies with temperature and pressure.

To achieve maximum power [peak/average BMEP] you must complete 66% of the burn by 16-17 Degrees after top dead center.You may have to start the spark ahead: 58 degrees at 60 mph cruise, 30 at idle,36 at in drive idle, or 38 at WOT 4,000 rpm or 44 at HP peak.

One thing the 90-95 Q doesn't do is measure intake air temperature [a 100F variation is minor in the scheme of 1500F in combustion chamber] in that the ecu guesses summer vs winter by coolant temp.Since with a properly operating cooling system the coolant temp never gets above 185F when the outside temp is below 75F.AC on is a signal that the ecu sees [aha must be warm outside then the coolant temp is evaluated as to how warm].The 1 degree reduction every 5F [increase in cooltant temp] gives it something to work with - kind of a 1 degree equals 10 F ambient 85F, 95F, 105F, 115F [must be in Death Valley].

Years ago [1985-1989] Bosch had a system on BMW where a 5 position knob played with ignition advance and fuel injection [kind of a +4,+2,0,-2,-4] trim in Europe to take care of bad gas, cold or hot conditions. But the 1990 Clean Air ACT killed any though of letting the owner tweek the engine!

Q45techMember posted July 20, 2002 05:31 PM Still didn't answer the question about the off line acceleration.The Nissan has tip in [sudden WOT] retard much like what happens prior and during a shift. The duration and amount is a partial function of the coolant temperature!So flooring a cool car is much different than flooring a hot one!

ChallyMember posted July 21, 2002 08:52 AM Hey, thanks all for the responses.

Heath, the outside temp. is only about 12-15 deg C, so the temp isn't a problem at the moment. In Summer you are 100% correct as I have to retard it to stop the pinging.It seems to be affected buy engine temps only, & where Q45 Tech seems to have the answers I've been looking for.

The radiator has been serviced professionally & there is no obstruction to the air flow, & I've been thinking along these lines for ages, but I haven't had the info that the Tech has, so this info makes it easier, by knowing what the computer is thinking.

BTW, Q45Tech has confirmed the BMW adjustable computer, that so many people tell me was only an aftermarket item.

So for a start, I think I'll get a new Temp sensor & thermostat & check the difference.

Thanks again,

Chally

Q45techMember posted July 21, 2002 01:11 PM As to cold to warm up enrichment and idle speed:The volitility of cold gasoline is aways a factor as is getting the cats hot enough quickly enough to begin working.So an extra rich mixture is supplied along with extra [or less] timing advance and a higher than normal idle speed is produced as a function of coolant temp sensor. Additionally a mechanical system which opens the throttle plate a little [since the IAC system doesn't have enough range to get much above 1000-1200 rpm] is controlled by the actual flow of coolant throw the system [thermostatically controlled spring and throttle lift].

So if you set the timing advance [CAS] before the coolant is warmed up who knows what you are getting!

WARNING to all you do it yourselfers!!!!!!!We have seen ignorant techs adjust the idle speed with the warm up thermospring contacts/limit screws. WOW what a mess to correct takes days to get it correct even if you have winter conditions. In Summer you must figure a way to circulate cold water [below freezing] to set two screws correctly.It much easier to just sell a new $500 throttle body than to try to correct a misadjusted one.

One turn is a radical adjustment!

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wamQ45Member posted July 21, 2002 02:35 PM --------------------------------------------------------------------------------Note to self: Don't mess with idle or timing...IP: Logged Q45techMember posted July 21, 2002 03:19 PM --------------------------------------------------------------------------------http://www.allfordmustangs.com...Q.pdf How ecu determine things for a 301 [5 liter mustang] but close.

IP: Logged wamQ45Member posted July 22, 2002 09:40 PM --------------------------------------------------------------------------------Q45Tech: You stated that you have been harping on coolant temperature for some time now. Well I just experienced it first hand. I have had a sluggish Q45 ever since I replaced my radiator. Well I messed up the coolant/water ratio and put too much coolant in (I did not premix the coolant with water). Well today I check the water level by opening the filler cap. When I replaced the cap it broke the seal. I did not notice and drove to work, it over heated alittle and blew off some of the coolant. I replaced it with water and a new cap. All of a sudden I have power again and I don't think it is related to the $600.00 in parts I put in the trunk. Verrrry strange. I will still replace the fuel pump, sender and under plenum hoses but the car is much nicer to drive now.IP: Logged Q451990Member posted July 23, 2002 12:35 AM --------------------------------------------------------------------------------

quote:--------------------------------------------------------------------------------Originally posted by Q45tech:WARNING to all you do it yourselfers!!!!!!!We have seen ignorant techs adjust the idle speed with the warm up thermospring contacts/limit screws. WOW what a mess to correct takes days to get it correct even if you have winter conditions. In Summer you must figure a way to circulate cold water [below freezing] to set two screws correctly.It much easier to just sell a new $500 throttle body than to try to correct a misadjusted one.One turn is a radical adjustment!

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Also on that note... the slack in the throttle cables is supposed to be there. They'll bind if a mechanical genius decides that maybe he should take the slack out for better throttle response. That slack also needs to be there for the fast idle cams to work. Adjust all of the play out when it's cold and you'll always have a high idle. Don't ask how I know At least this mechanical guru didn't mess with the throttle body cams.

Heath