Hi,
I've just installed a new 383 engine replacing the stock l98 of my 1991 TPI c4 and ran into some problems. The manifold is edelbrock highflow, upper plenum port matched, 1205 size ports, stock TB
specs: mild cam with 0.495/0.502"lift, 202"1.6"valves,9.8 compression, 1.5 hidraulic rollers ,220/224deg duration @0.05", 65cc/195cc. 16-34 deg recomended ignition, 112lsa
injectors are 43lbs bosch aka 'greeen giants'
I can start it up with throttle input but it dies if I let out the gas quickly. I did idle initialy a bit rough but then I set the correct initial timing to 6 degrees from 8 and after doing a warm up cycle id didn't idle anymore.
Then I reduced the timing a bit and at the last run I kept the rpm to 2500 for a minute then attempted to see if it idles when we noticed the exhaust manifold starting to glow red, it was at dusk but definitely EGT off the limits. Everything was done in neutral. Now I'm woried about potential damage to cyl. heads

I have the calalythic converter on the car and two high flow 100cpsi on the front, they were glowing as well. I will remove the Main CAT which is on V bands and I have straight pipe to replace, before running next time.

I have two log files, I can analyze but data seems confuzing.




The O2 seems to the lean side but BLM seems to try to compensate for rich. The history table show 112 through 118.





The computer seems to try to reduce fuel and the O2 looks slightly lean but not excesively.
Another weird thing is the MAP going UP and IAC up when attempting to idle (TPS low or zero)
I also suspect high friction (engine or accessory like AC?) causing IAC to stay high and bogging down the engine.

Any help would be much appreciated. Many thanks

 

Some initial questions regarding your fuel delivery...

If so, have you changed you injector constant to 42 lb?

Have you checked your fuel pressure?

Have you input the correct voltage offsets for those injectors from the injector datasheet?

If you have the actual datasheet, it should also show flow rate vs fuel pressure. In which case, you should use the flow rate for your fuel pressure in your injector constant.

With Bosch-III's, it's also recommended to zero out the Low Pulsewidth Compensation Table as well. These types of injectors don't need any "help" to deliver the right amount of fuel at low pulsewidths.

Other comments:

With that cam you may want to bump up the commanded idle speed into the ~800-900 rpm range.

Recommend (at least for now) zeroing out the spark advance/retard idle speed error compensation tables. Those tables can sometimes cause "hunting" where the ECM chases it's tail on trying to maintain the prescribed idle speed and you get unstable idle speeds.

On the spark timing map, where your idle may be moving around a bit between one RPM row and another, try not to have a big difference in the timing values. I.e., if you have say, 20 deg at 800 rpm and then 30 deg in the next row at 1000 rpm. That can possibly cause idle instability as well. I'd also try to be running a minimum of ~25-27 deg at idle.

Lastly, try to reduce your IAC counts at idle by opening the throttle blades a bit. On mine, I run about ~5 counts in neutral. Makes it less sensitive to what the ECM tries to do.

Once you get a stable idle, you can revisit some of these changes above and move back toward stock a little bit a time.


Personally I think those injectors are too big, but you can probably tune around them. I might have gone for something in the 30-32 lb range.

 

thank you
the bin file is set up for 42lb, cylinder volume for 383ci and I also have a new offset table, I will post it later. idle speed is set to 1000rpm.
I’ve thought of removing the spark plugs and spin the engine to see how much the torque is required. the battery was able to crank it without difficulties though but it seems to stop too fast after I switch it off. the flywheel is aluminum which is a factor but it could still be something wrong.

 

You might also get WB O2 sensor and temporarily replace the NB sensor (though obviously for monitoring purposes only, not trying to run the ECM off of it)

Then restrict the ECM to running open loop until you get the AFR dialed in and everything else stabilized.

Basically find out where the engine likes to idle AFR-wise.

After all that is done, you can put the NB back in and re-enable closed loop operation.

If you found that you need to idle around 14:1 AFR or something like that, you may need richen up the idle O2 rich/lean threshold to force a richer mixture while still being able to maintain a ~128-ish BLM.

 

currently is set at 14.1 as the E10 fuel has a lower st. AFR. I have an AFR but didn’t mange to install it yet. it is ready to be plugged in and I have 4 threaded holes on the exhaust, on the right there is already a secondary O2 hooked up to an external module that can take the AFR input as well. I also have en EGT sensor but needs a threaded hole. I could use a friction drill to prepare it, although it might be too late considering that glowing exhaust manifold that can mean serious trouble.

 

If my car idles at 2500 rpm for a couple of minutes, the headers will glow red. I wouldn't worry about it. Make sure as mentioned you get your O2 sensor working so you are not in the dark. Those injectors might be a bit much for your 383. I ran 30lb injectors when I ran a 383. I'm 36lb with my 406. Plenty of fuel to 6800 rpm.

 

The new data for the injectors is in the bin file but too large means worse atomisation qnd potentially pronlems with low pulse width but that’s what I found at that time.

 

Just to verify... you have this injector datasheet?

https://www.tiperformance.com.au/wp-...1379511446.jpg

 

Like already mentioned, I'd also try to open the TB blades a little bit more. Looks like IAC is trying to keep it running with max steps at idle. Can you share your datalog files?

 

yes. i’ll try that once I take the CAT off and install AFR. it makes sense. If I remember correctly the tps resets itself on next startup after adjusting the TB stop bolt?!
many thanks

PS the injectors offset is a bit different, I got it from a forum where it was reccommended:

 

Yes, TPS will reset.

Your offset values are probably close enough to the datasheet... only off by a few microseconds.

But yeah, like I said, highly recommend doing your initial tuning and stuff in open loop so you're not fighting the ECM when trimming the fuel.

 

I've seen a clip with a guy talking about breaking the engine in and he says in the first minutes of elevated rpm in neutral(2000-2500) the friction will be very high and the exhaust will glow red. However, In my case the engine idled initially and when it got to operating temperature it showed what I think were signs of increased friction, the glowing exhaust and some screeching noise after it shut it off

 

Not sure about that. My HT383 short block started up and idled and ran perfectly without any need to do anything special. During the "break in procedure" I drove the car around normally (albeit doing the special things that GM requires during that period). No running problems or issues with AFR or glowing red exhaust.

 

It seems to me that you do not have enough spark advance, especially at low intake manifold higher RPM. Your base throttle blade setting seems to be too low and you need to open it more to allow the engine to idle with some IAC control. The glowing headers may not be a problem but could be related to too little spark advance at low load and 2500 RPM idle speed. In general you can run 40 plus degrees of spark advance at low load higher RPM. AT WOT your timing should be around 32 to 36 degrees above 3000 RPM and you seem to be very low unless I am not seeing total spark advance.

 

Not that it matters at this point, but you have a roller cam and there is no real break-in procedure for that type of camshaft. You don't have to fast idle the motor for 10 or 15 minutes like you would with a flat tappet camshaft.

 

the procedure came with the engine so maybe that’s how they do it , but it means that part isn’t that critical

And a question. Can I feed the AFR 0-5v analog to the ECM O2 wire and force open loop without damaging anything , or is it too high? My idea is it should at least work with a voltage divider then create an AFR variable in Tuners pro to log it

 

If your converters were glowing that usually either means they are clogged or you have unburnt fuel dumping into them, either because one or more plugs is not firing reliably or you are running very rich.

 

both sides were the same, so a general heating condition. we-ll see when I open up the exhaust

 

The 7730 ECM has another 0-5V port which can be used for that. The S-AUJP code has that functionality built into it already as well.

https://www.thirdgen.org/forums/dfi-ecm/616360-repinning-7730-wideband.html

 

thanks, I’ll check that.
anyway, I have a module that I built to control the alternator for my Lithium 12v battery and it can take the 0-5V and output whatever signal I want but it would be a bit easier to not use the module