We just installed a 7-8lb flywheel in my GSR w/ITR block and came
across some interesting findings.

I usually run my ignition timing at 17-18BTDC and I decided to check it
about a week ago before we did the clutch/flywheel. I saw it was at 17+deg (just a skoche behind 18) After the flywheel, I decided to check it for grins. It was at 14-15BTDC! Driving the car this way still felt awesome, I couldnt believe my eyes. I checked again... yup 14-15BTDC! WEird. Car ran great... I am figuring that
having less inertia that between strokes at idle the motor actually "slows down" creating the few degrees in timing retard. my question is this though:
once the motor picks up rev speeds, would the timing track the same
as if it were stock>? I.E. with 14BTDC set at idle would it track through the map similarly to stock once the motor is at speed? My guess is once the motor is in gear accelerating the engine's flywheel accelerates with greater ease, thus perhaps allowing the timing to charge forward a wee bit as compared to a stock 15-18lb flywheel. I really dont know. I am feeling that I need to take it to a dyno and check 14, 16 and 18 BTDC resetting the ecu between runs. So all that being said, has anyone noticed the timing and maps being "off" seeing as how the motor is operating on a different load? Any hondata tuners noticed this? I noticed a few
points fell off my MPG also, my guess is due to the clutch/flwyheel
transferring more load into the engine at speed I got 265 on my tank in the
"city" at 12.5 gallons, driving WOT VTEC about 25-50% of the time. Thats about 115-120 on the first half, 125-150 on the second half tank in my integra. thanks guys. the timing is currently set at 16BTDC. What would be the best means of checking timing in this case now? Would I need to learn how to check total degrees advanced> with a different gun? I really only know how to use a basic blink blink at idle Any suggestions would be much appreciated

 

perhaps check again with an advancing light and see what you get.

 

id have to get access to one to try it. as far as total advance degrees>
how do you set total advance degrees properly? What should an ITR
bottom end have in total advance degrees? Like I said, I usually run
16-18BTDC on my car before this flywheel. thanks...

 

I got an 8lb flywheel too, but the motor is all stock. Should I be worried about my timing too? I want to see what you find out.

 

I wouldnt be worried, however I will dyno 14,16 and 18BTDC and compare the graphs. once I do I will let you know. I plan on dynoing sometime this coming week just for giggles.

 

I don't think it's your flywheel that changed the timing. Timing is controlled by the cam gears and distributor (make sure your dist. isn't loose). However, if your timing belt stretched, then your timing would retard. Better check out your timing belt before it breaks.

 

thanks. my motor is maintained perfectly. My new timing belt was installed when we put in the new R block at 49950 and I have 76450. my timing belt deflection and valve lashes are checked every 5K miles and returned to spec if necessary. I run my car with the upper timing cover off so I can keep tabs on the belt tension at TDC routienly. the timing was checked and marked before the clutch install and right away the timing went from 17-18 to 15BTDC. I am lead to believe it is the difference in the flywheel weight due to the amplified deceleration between strokes of the motor due to lower rotational inertia at idle. A timing belt tooth is 10.28 degrees and my cam gears are stock. If I jumped a tooth or if my belt loosened it would have had to do it a couple days from when I checked the timing. If it jumped a tooth in either direction it would be WAY OFF THE SCOPE 10 degrees in either direction. It wasnt, only 14/15BTDC. My clutch went in on 7/11 and the timing was checked at 7/02 17-18BTDC checked with the service connector bridged at 500 rpm with the IACV unplugged. The car was parked from 7/04-7/11 and not driven. On 7/15 the timing was checked and it was at 14-16BTDC or 15BTDC. I was breaking in the clutch and the motor never saw above 6K rpm. Nothing mechanically failed causing this curious observation with the timing retard at idle. What makes me curious is if when the flwheel is under load spinning with the motor would the dynamic shift the other direction a few degrees due to faster ACCELERATION of the motor. My theory is that too much timing advance at high rpm if the motor due to the flywheel is mechanically clocked 2-3BTDC more than it would naturally be due to the increase of rotational intertia at speed. IE if my motor before on the 15lb flywheel was 18 at idle and say 40 (est(total) at 8K, then with the 8lb flywheel/base timing at (Same distibutor setting) 15 the total degrees would still be at 40-42(est). I notice my car does not pull as hard with the timing advanced to 18 like before. It feels like there is too much say 55-58total up top (est). Once I dyno the car and see the curve at 14, 16 and 18 and see where it has, loses or makes power I will be able to better approximate it. It is responding differently. The crank fluxuation sensor and the TDC sensor in the distributor is obviously noticing a different input.


Modified by MikeSarr_GSR at 3:37 PM 7/18/2003

 

let me kno when u dyno it iam interested to see what u come up with. pm if possible

 

I was actually planning to have my car dynoed too. I can't wait to see what results you come up with.

Unfortunately I dont have a timing gun, otherwise I would see if my car is doing the same thing with the 8lb fly.

BTW your idle is still the same though right?

 

check engine light was bridged?
engine was completely warmed?
idle rpm was set at the correct rpm?

 

bridged
normal operating temperature
IACV unplugged 500rpm sustained
(idle rpm wont clock timing way off unless over 1000rpm)

any other questions as to my method of
checking ignition timing