Cbystrack

alright i just put my new 355 in my iroc and what i have for questions are the following i put a 160 t-stat in the car thinking that running cooler would be a good idea seeing how i live in NC and it gets warm here. Anywho i have a stock computer and i read that the computer does not take over till 180ish? i am having tons of issues with my engine swap as it is and i think this is one of them that i need answered.... anyone have any advice?

Marc 85Z28

Uhhh, what is the problem exactly? You didn't say...

Anyway, you WILL need to have the ECM properly calibrated along with the installation of a manual fan switch.

Cbystrack

what i was trying to get at is if i read correct then my 160 t-stat will hold my computer from taking over as stock serttings for computer to take over is 180's???? i am hoping that my computer will learn the bigger injectors and cam but without it reaching proper temp it will never learn it???? sorry i am confused a bit.

i also tried to re-time it today because the timing was way off... what i understand is the i have to unplug the wire above the heater box then set it to 6 degrees? then shut car off and re-plug it in and go? i am a newly converted to chevy's from 80's mustangs and everything is wayyyy diff.

any input would be great!

quickchicken

being you now have a 355, everything your stock programming does goes completly out the window. you need to find someone that tunes chips to bring everything into play, otherwise you car is going to run lean when you drive it even though you have bigger injectors.

you feeting it more air but the fueling hasnt been adj to the bigger cam so your not geeting the proper fuel and its going to be off in other areas like cruz, idle, decel, WOT and so on.

Marc 85Z28

Your question makes no sense. Again... have the computer tuned and put in a manual fan switch. Stop trying to make sense of it and just do it. The computer will not "learn" the bigger injectors - you have to tell it what you have. With the 5.0s you would calibrate the MAF to the injector. With GMs, you do it the right way, with the computer calibration.

'91 1LE

To answer your original question, the computer goes into closed loop at around 130. If your cam is stock or close to stock you should be able to use your stock injectors. Being as your car is MAF, it has enough flexibility to compensate for 5 more cubic inches (assuming your car started as a 350). And you are correct on setting the timing.

quickchicken

everything iv ever read says the ECM goes into closed loop @ 166. i'll see if i can find where i read this at.

'91 1LE

We were both wrong. According to my '91 Factory Service Manual "closed loop" operation begins when the following conditions are met:
1. The O2 sensor has varying voltage (indicates it is hot enough to operate).
2. The Coolant Temperature Sensor (CTS) is above a specified temp, about 104 deg. F.
3. A specific amount of time has elapsed after engine start.

The specific temps and times (2&3) are referenced to the MEM-CAL for each particular engine. For a 5.7L TPI, closed loop can start at 104 deg F.

Marc 85Z28

If he's running a 6" rod, it's a safe bet that the heads and valvetrain aren't stock. Therefore the stock injector and tune is nowhere near adequate.

rjgarciasr

I have to pass emissions so I use a 180 T-stat, and the ECM is programmed to turn on the fan (no A/C) at 210 (stock was 225.95), and off at 195 (stock was 220.55.) As for the ECM unless the cam, initial timing, and or injectors size have changed there's no need for reprogramming. But, that's my experience I'm sure others will counter my opinion.

'88 TPI 6.4 Liter IROC-Z.

Cbystrack

the car is an org 350 tpi/700r4

the heads/cam/injector size was a kit put together by a local camaro guy who says it will work no prob due to the lobe seperation being close to stock. Only reason the car has not been brought to him with the issues is because he had a stroke shortly after he finished the build for me.

The valve train is roller (cam) which the stock engine was with 1:5 comp cams roller rockers

lower end is 6'' rods, shaved crank, and bored.

The fans are hardwired with the ignition (have been that way since car was stock) I took the 160 t-stat out and put a 190 in it and it did help a little. I still have to put the o2 bung on the new y pipe because i am sure thats ALOT of my issue running without an o2.

i got a walbro 255 pump going in tomm i hope. From the research i have done it should feed the 30lb injectors without any issues. I am sorry for being a noob or acting like i dont know anything... i just came from carbs so im a little lost with EFI. Thanks everyone for the input and i will keep this post updated.

BigBadLou

Welcome to the club Cbystrack.

Yes, if you have a different valvetrain and injectors, it changes your engine running conditions considerably. You will need to make some small changes to your chip and burn a new one.
What cam are you running? Just curious.

Fans hardwired to ignition are not a good idea. For sevaral reasons. The most important being:
- if they draw power from the ignition circuit, you introduce voltage drop to the coil and other components because the circuit wasn't designed to run the fans as well. And you are chancing blowing the fusible link. By Murphy's law, that would happen in a remote location.
- the fans' life-span will be shortened considerably - they will burn out within a few months because they are not designed to run constantly. They are needed only if the vehicle is not moving, or moving slow. (stoplights, traffic)

If you have an overheating issue with the engine, running the fans constantly is not a solution, it's merely a patch. It would be better to find the real cause of the condition.

When installing an O2 sensor in the Y-pipe, be sure to use a heated O2 because the sensor is too far away from the exhaust ports now. You can use 3-wire or 4-wire, both types will work.

Yes, the 255 Walbro will feed 30-lb injectors just fine, no worries.

Questions and answers are what all of us are here for, so just ask away.

Hope this helps.
Lou

Cbystrack

okay thats for the feed back, i will run the fan to a switch. im assuming there off the ignition because once the key is on there on.

What kind of o2 are you talking about??? my o2 is a single wire hook up? and its odd the car only had one o2 on the drivers side exhaust manifold.... now with the 255 fuel pump (which made A WORLD of change when i took it for a test spin) should i replace the factory fuel pressure reg with an aftermarket one????? or just check fuel pressure off the fuel rail with the car running? i dont want to run too rich or lean god forbid ya know?

BigBadLou

O2 sensors need to be VERY hot to work properly. The stock O2 sensor in the stock exhaust manifold is close enough to the exhaust ports to be heated by the exhaust gasses.
However, if you put aftermarket exhaust on and move the O2 sensor away from the exhaust ports in the heads, the O2 won't get hot enough to provide proper readings. That's where the heated O2 sensors come in. Instead of a single wire, they can have 3 wires (1 for the O2 reading and 2 for the heating element) or or wires (2 for the O2 reading and 2 for the heating element). You just connect the heating element to an ignition-controlled power source and it will keep the sensor hot enough to operate properly, even that far downstream. I'm sure Google will be able to assist you with more information, diagrams etc. If not, feel free to ask.

I agree that it would be a good idea to put a fuel pressure gauge on the fuel rail to monitor the pressure. That will tell you whether your FPR is capable of bypassing the flow from the Walbro or not. If your fuel pressure stays steady with the engine off (all fuel getting bypassed) and doesn't increase, you should be good to go.

For the electric fans: it is also possible that the relays are simply grounded so when the ignition is turned on, the relays are activated and turn the fans on. The fans still draw from their own power supply wire but you are still chancing their early demise.

Hope this helps.
Lou

Cbystrack

lou this helps alot indeed. now for my next question... where can i get a good eprom burnt??? pcmforless??? and the heated o2 the feed wires that is just 12v+ and a ground??? then my actual reading wire for the sensor correct??? do you think there will be thread difference of should they be the same??? thanks -chris