jacsha

i have a 93 FD, around 60k milage, got intake, dp, mp, exh, ecu (14.7psi) installed
When i was driving at around 2000-2700rpm in 2nd and 3rd even 4th gear (no turbo kicks in). The EGT went up to 700-950 degree. Will i blow the engine in such a low rpm?
but after the turbo kicks in either 2500-7000 rpm. The EGT was showing between 600-750 degree only. Can anyone figure out what happen with my car? is that too lean or something wrong?
Please help. and Thanks

RETed

Welcome to the world of closed-loop electronics...

Under light load conditions (like highway driving), the ECU runs a closed-loop feedback system using the O2 sensor as an input.&nbsp The ECU constantly samples the O2 sensor input and readjusts fuel delivery to run about 14.7:1 stoic AFR ranges for better fuel economy.

When you put moderate loads on the engine (like WOT), the ECU reverts to internally programmed fuel maps.

What you are seeing is totally normal.



-Ted

jacsha

Thanks for the information, its normal, so i don't really need to care about the temp on low rpm? also the backfire is like continous firting, kind of scary.....

RETed

The real danger is only at WOT, so you can ignore all the low-load stuff...

I dunno about the farting thing, but do you have a way to adjust fuel?



-Ted

jacsha

i do have a non digital S-AFC. it works great.
Thanks for your reply

Anthony Rodrigues

jacsha,
The temps do seem like they are marginally high and an engine on light load should cycle at around 750-800 not 900+ continuous backfiring usually indicates lean running caused by vacumn leak, 950 is rather high and I would definitely be looking further into it. High temps prematurely wear turbos and internal engine seals, be carefull. Given that you have an ECU check to see what ignition timing you have there as that can also cause alterations in EGT. Although not enough advance will not usually cause a backfire.
Regards-Anthony

jacsha

The ECU i got sometime give me rough idle and easy to stall when i put in reverse gear, i have to cheat it, tune up the idle to 1100rpm, i bet its the ECU problem. The temp is really too high, thats what i'm worry about.

Anthony Rodrigues

Ignition timing or lack of it can do this and so to can an inlet manifold leak. If the mixtures are caused to go excessively lean, this should be beyond peak torque mixture ffor that point and would give it the tendancy to stall easily. Check all factors that could cause this condition, lack of fuel or excess of airflow at idle. Perhaps if you want to confirm this analysis, you could ignore your idle speed and add fuel at idle to compensate. If EGTs go normal and engine runs more smoothly, go and find the leak and you will be back in the groove.
Regards-Anthony

Damnfuct

jsut a thought.. if rx7's have EGR (Exhaust gas recirculation) and if it's disabled or malfunctioned, the car will take in more air than fuel than it needs, because it thinks that some of the air is inert exhaust gas.. anyways, you get a lean condition.

RETed

jacsha has a 1993 FD or Series VI to you.&nbsp These MAP-based systems are hardly affected by intake vacuum leaks, unless there's a HUGE one downstream of the map sensor position, which anything after the lower intake manifold; if he had that bad of a leak, you'll see lower boost pressures also.



-Ted

jacsha

i don't really see a boost drop from the gauge, and i just replace all of the vacumn hose and check with everything. hmm its really hard to tell

rxeng

IF IT WAS ME I'D BE RUNNING THE CAR UP ON A DYNO WITH A TIMING LIGHT CONNECTED TO CHECK WHAT THE IGNITION TIMING IS DOING.THE EGT'S THAT YOU HAVE ARE WAY TOO HIGH.
IF THE TIMING IS RETARDED IT WILL CAUSE YOUR EGT'S TO SKYROCKET LIKE THIS.
MAYBE THE ECU IS DOING SOMETHING STUPID AND RETARDING THE TIMING DOWN LOW & THEN CHANGING BACK TO NORMAL AS THE REVS RISE.
HOWEVER THE BACKFIRING THING USUALLY IS ASSOCIATED WITH THE ENGINE RUNNING EXCESSIVELY LEAN SO WHILE YOU ARE AT IT CHECK FOR AN AIR LEAK(INLET GASKET,VACUUM HOSE FALLEN OFF,FAULTY SOLENOID VALVE ETC)
IT'S EASY ENOUGH TO CHECK SO GO FIND A DYNO AND GIVE IT A TRY.
RE-GARDS
JON

jacsha

Isn't backfire cause by running rich? Is it possibile that too much fuel was burning and heat up the turbine which makes the reading went up?

PraxRX7

I tested that in my bug today, when I lean it out it pops and backfires...rich it just runs like ***.