Well, new motor is in. Mods are all in sig. A friend of mine is helping me burn proms until I get a burner and equip soon. Anyways, I went from a 305 to this hotcammed 350 and 24# LT1 injectors. Upon intial startup car ran fine, was a little rich, but ran fine otherwise. Burned new chip to disable VATS (it went haywire) and turned off the EGR, reset inj const to 24# from 19#. The car then ran like crap. Ran ok at WOT (not as good as b4), but at partial throttle it would stumble and the o2's would drop to almost 0. Replaced o2 sensor, fixed header leak, and put stock FPR back on (My Holley AFPR diaphram broke). Anyways, all that stuff didn't help it. Still would stumble bad. We kept playing with the chip. Changing inj constants again trying to get the BLMs back up. BTW- as soon as it would go closed loop, my BLMs would drop and drop and drop... all the way down to like 83 or so. After playing with the timing A LITTLE and still adjusting the inj. const. more, it still wouldn't run any better. Finally we went back to the stock (hypertech) chip and just turned off the VATs and EGR. It runs fine again. Not optimal by any means, but it pulls strong and gets over 20mpg like this. WTF? I don't understand what we were doing wrong concerning the injectors. Is there something else we needed to change with my SD TPI besides just the injector constant? I thought I read somewhere (Ed Maher or Glenn91L98) that there was something else you had to change on a SD chip when changing injectors. I think this is one of the first things I need to change in the chip. Yes or no?? Thanks alot! I'm just trying to get "control" over this motor. Open to all suggestions and help. I'm just here to learn!

 

No one?????


TTT please

 

Well, since it seems to be running "ok" with the hyper#$%& chip in it set for 19# injectors, try getting a stock bin for a 350, disable vats, set injector constant to 19# and see what that does. If it runs like the hyper---- chip (rich) start slowly increasing the inj constant, 19.5# then 20#...and so on, until you get it running better and leaner.

 

Thanks! We tried a JET 350 chip with 22# or 24# constants but it still acted up. If I have it at 19# right now, and my BLMs are low... won't raising the inj constant just make my BLMs try to go even lower?? Its worth a shot I guess. Gees, I definately need a burner soon! THX

 

Nope, you'll be telling the ECM that your injectors flow more and it will shorten the pulse width, thus leaning out the A/F and the BLM's will rise.

 

I'm still confused. I thought that when the BLMs were low, it meant that the ECM was actually cutting the injectors back. If thats the case, then raising the inj constant would make it think it had bigger injectors and cut them back even more. Right? or not? Because when we had it at 22# or 24# the thing would run really BAD. BLMs were REALLY low too. It just doesn't make sense to me or my friend who does the chips for me. He is running 28# GN injectors in his 350TPI. He adjusted his constant to like 26# to get the BLMs at ~128. He knows what he's doing, but my car isn't responding like his. Is it b/c MAF and SD are different or what? Is there something else we need to change?

*Raising my inj constant is NOT helping it at all. Thanks!

 

Raising the injector constant will RAISE the BLMs. You are thinking incorrectly. Think about it this way ... when you tell the ECM that you have larger injectors then it shortens the pulse width on the injectors. By shortening the pulse width LESS fuel is supplied to the engine. Thus, if you are running rich (low BLMs) then now you will be running LESS rich because you squirting less fuel into the engine. So - BLMs will increase. BLMs higher than 128 mean that fuel is being added because too little fuel is being supplied. BLMs lower than 128 mean that the ECM is cutting fuel because too much fuel is being added via the injectors. So, if you decrease the amount of fuel being added (higher injector constant) then the BLMs will begin to raise because the ECM will not have to subtract as much fuel.

Tim

 

EXACTLY! But when we raise the inj constant, the BLMs are NOT coming up. They're doing the same thing as when we use the 19# setting in the chip. This is what I don't understand. Is there something wrong or something else we need to do. The only way its driveable is with a 19# setting in the chip. WTF??? Thanks for the help TRAXION, but I understand what its supposed to do and how it works, but mine is NOT responding well to this change. Me and my buddy are both puzzled. THX again!

 

How low are your BLM,S?
Try raising the injector constants by the % you are from 128.
If the injector constants are really not doing anything at all
then maybe you have a bad vacuum leak or a sticking injector.
Check all or your plugs,all look the same? is one soaked?

 

Are you considering your INTs? This is why I like to LOCK my BLMS because INTs ARE a factor. Which is richer a BLM of 120 and INT of 126 or a BLM of 126 and INT of 120? Answer, they are the same.

To truly see the effects of modifications, I have found locking the BLM to give the best results. Then you don't have to wonder if BLM/INT 120/126 or 126/120 are the same.

 

They're down all the way to like 85 or so when they drop (most the time when driving). I'm beginning to think its the injectors. They're used from a friends WS6 with low miles, but they sat for awhile b4 I bought them off him (he went 30# SVO's). I'm wondering if one is stuck or they're all dirty maybe. Vacum leak could be possible. I did change the plugs for the first time a few eeks back (~2000 miles on new engine) and a few were really rich. Back cylinders I believe. It would have to be on the driver's side (o2 side) though right? If its a passenger side inj sticking, the ECM wouldn't even know because of no o2 info from that side. Guess I need to just pull the plugs again, maby pull injectors for cleaning, and put new runner gaskets on again. I'm also considering a heated o2 for it. Another post in this section suggests I need it. Guys are having searching/low BLM's with long tube headers and NO heated o2 sensor. (like I'm doing) Well, gotta run. Thanks for the suggestions.

 

Glenn, sorry we were posting at the same time. I just now saw your post. As for the INT's, I'm not sure I'll have to go drive and scan it and post in a little while. What exactly do the INT's do then. I understand what the BLM's do. Not sure on the INTs! Do both the INTs and BLM's need to be close to 128 or what? Thanks! I'll post INT info in a few hours. Later!

 

GTA,

Glenn is right. Lock the BLM's at 128 and tune using the INT's. Stands to reason that if the short term INTs are very close to 128, then the longer term BLMs will also be very close to 128. Once the INT's are close, then unlock the BLMs and fine tune for 125-128.

 

Thanks man. I see what you're saying. I just got back from a somewhat long trip. Ran the scanner on the way back. It looks like my INTs are about 110-115, while my BLMs are lower. Sometimes (maybe most the time) the INTs are even at almost 120 or so. Pretty decent I guess?? Still is rich though and chip is still set at 19# inj constant. What should I do next then? Lock the BLMs and see what it does or will that not really change anything? Should I lock them and switch to a 24# inj constant and see what it does?? Thanks for the help. I just wanna try and get it a little more tuned to see how it does. Later

 

GTA,

With the BLM's unlocked, the INTs will move in the opposite direction. If the BLM is below 128, then the INT will move to lean it out and vice-versa. With the BLMs locked, the INT will mimic what the BLMs would be doing but on an "instantaneous" basis.

 

Thanks! That clears things up quite a bit. I'll try that and see what that does. THX again!

 

What ever happened with this? I'm having exactly the same problem now. originally had a 305 in my car (19#), went to 350, kept the 19#ers. It ran fine until 2 of my injectors went bad (took them 203000 miles to do that =). So I upgraded to accel 24#ers. Runs perfect with the stock (19#) chip, other than being pretty rich (same as GTA91's, ~85 BLM). I started with a stock '89 305TPIm5 bin and simply increased the injector constant. The BLM's evened (128) at about 23#, but the engine isn't running smoothely at that point. So I need to revert back to the stock chip and let it run rich.

Though my car is a MAF car, did you (GTA91) figure out what was wrong with your tuning? I need some advice too.

Also, other than milage, will running this rich damage anything?

Mark