Junkyard TBI tuning ????

[brokejeep]

I have a junkyard TBI on the AMC 360 thats in my scrambler. It is up and running but seems to be a little rich. The chip is one that was modified for the engine but I believe it could be dialed in a little more. Is there any shop that I can trust to do this or should I buy the cables and attempt to dial it in myself??? Any input would be great... Is there any body local that is fluint in this conversion Erussell had been helping me but has since moved on to greener pastures in cali.

 

[Caleb]

I'm not super familiar with that swap, but you can't just "dial" it in, I believe you have to burn a new prom. So you can buy the stuff to do it, but if it's just for this one project I don't think it would be worth it. Also, the settings aren't just plain text (so to speak), it's all hexadecimal so you have to decipher that. I was going to do the same thing with my TBI 4.3L and decided to leave it to the pros (I did buy the cables that I could monitor what was going on, but to make any changes...see above )

EDIT: Another option I think I've heard guys doing is depending on which injectors you are using, you can get different ones. I don't know exactly how that would work (maybe smaller orifice so less fuel???) but I've heard guys that needed more fuel getting injectors from a 454 TBI, so you could probably go the other direction too, just got to find a smaller injector

 

[brokejeep]

I have removed the stock chip and put in a programable from moates.net so if I hook my jeep to a lap top I can modify the fuel and timing tables on the fly. At least thats how it was explained to me. I am begining to think that a carb might not be better but at least I can tune it myself. Although once the TBI is dialed in it will be that way forever.

 

[lewis]

I had a similar problem on a 400. I ran the 454 chip since the 350 chip ran it too lean. It ran rich. I was able to get an adjustment thingy (I can't remember what it was called, bolts on behind the injectors) from Jet that restricted the flow and was adjustable. It ran great after that.

 

[bad_90blazer]

The fuel pressure regulator is what your thinking of. There are a few companies that make them. You might try checking out TBIChips.com there is tons of great tbi related info on that site, and Brian is very good with helping people. You might try CFM Tech and Howell EFI also for more parts and conversion info. I have TBI on my K5 and love it, you wont regret it once you get it all dialed in.

 

[brokejeep]

Yeah I know I wont regret it but I am impatient.... I talked with eric the guy who helped me with the conversion already. He's thinking that the computer is in limp home mode which makes everything rich and keeps the vehicle out of closed loop mode. I have a few tests to run and I will post the results.

 

[cheepin]

Which O2 sensor do you have and where is it mounted.The stock GM 1 wire needs to be mount up close to the head so it heats up correctly.Needs to get to something like 400*-600*.If not it will read the engine as running lean and richen it up.

 

[Tacoma]

GM mounted the O2 sensor either in the manifold, or on the downpipe near the firewall. Of all the TBI stuff I've had, there was no standard. Drivers side, pass, in or out of the exhaust manifold...

 

[waynehartwig]

Exactly. Single wire O2 sensors need to be in the manifold (or real clsoe to it) and no place else. If you can't get it that close, then go to a 4 wire setup - with the built in heater. Then you can mount them anywhere you want. The heated type are better as well.

 

[Tacoma]

there's nothing wrong with the 1-wire sensors the harness is set up to use... and if you can't get a sensor within 18" of the heads your in some packaging trouble anyway... plus, the 1-wire sensors are like $20 to replace...every 80k miles....

 

[cheepin]

GM mounted the O2 sensor either in the manifold, or on the downpipe near the firewall. Of all the TBI stuff I've had, there was no standard. Drivers side, pass, in or out of the exhaust manifold...

On my '87 3/4 ton 5.7L Suburban it is mounted in the driverside manifold.It is the same on the '88 7.4L 1ton motor in my CJbuggy.

 

[Tacoma]

I've got the following at the house:

87 dually w/454-- passenger side, in the downpipe
89 Blazer w/350-- drivers side, in the downpipe
90 Burb w/350-- drivers side, in the manifold

I've gone through...let me think now hahah....6 work vehicles and 3 personal vehicles, and I don't think any two of them in a row were the same..

 

[brokejeep]

I have the single wire. The engine has headers so the o2 sensor is in the collector where the 4 pipes come together. I will consider getting the 4 wire heated sensor... Thanks for the help

 

[Daviticus]

What software are you using to tune your tables with? I've messed with a couple programs [TunerPro RT among others] with decent results, but I don't know if I'd be of help to you. I've got an Ostrich and EPROM burner at my disposal, when you find the right tune for your engine I can burn the chip for you.

 

[waynehartwig]

I have the single wire. The engine has headers so the o2 sensor is in the collector where the 4 pipes come together. I will consider getting the 4 wire heated sensor... Thanks for the help

If it's in the collector, and they aren't shorty headers, then it's definately too far from the motor to be accurate. Really, they need to be about ~6-10" from the exhaust port. If not, go to a 3 or 4 wire setup and power it. No big deal...

 

[Tacoma]

Wayne, my factory TBI sensor location is just behind the bend in the driver's side of the y-pipe under the truck, about 18" from the closest port... right where GM put it....

so there.

 

[waynehartwig]

Wayne, my factory TBI sensor location is just behind the bend in the driver's side of the y-pipe under the truck, about 18" from the closest port... right where GM put it....

so there.

That's where mine is, too.. Doesn't mean it's right
NINJAEDIT: on my motorhome...

 

[Tacoma]

LOL I only point it out to note that if GM engineers spec'd their own system to work with the sensor in that location, it will probably be alright... not that it was really the optimum placement... On the other hand, for truck use, I wonder how much difference it can really make? Most of use aren't revving our rigs past maybe... 5k? rpm, if that, and any gains in fuel economy are going to be tough to quantify with all the other energy sucking additions we make to our vehicles. Aaaaannnyway

that said, the junkyards are full of TBI trucks, and the various manifolds are pretty readily available, as are pricy but shiny headers.

 

[waynehartwig]

LOL I only point it out to note that if GM engineers spec'd their own system to work with the sensor in that location, it will probably be alright... not that it was really the optimum placement... On the other hand, for truck use, I wonder how much difference it can really make? Most of use aren't revving our rigs past maybe... 5k? rpm, if that, and any gains in fuel economy are going to be tough to quantify with all the other energy sucking additions we make to our vehicles. Aaaaannnyway

that said, the junkyards are full of TBI trucks, and the various manifolds are pretty readily available, as are pricy but shiny headers.

The problem is:
O2 sensors, even the best of the best in the best situations and best etc are still more than 4% off
The colder they are, the more off they are going to be
O2 sensors can't function in high flow environments, like ~3k rpm + - ie, they can't react fast enough
O2 sensors can't distinguish between a little and a lot lean/rich - they only know one or the other

So the colder they are, the more error they have, and the slower they react to changes. Meaning, by the time a cold o2 sensor realizes your lean, you've already burned up your motor.

So if it's in the proper place, or using a heated one, you lessen the risks and increase their efficiency.

 

[Tacoma]

I'd agree with that. I might be wrong, but it seems to me that GM counters that with their initial tuning? Running rich until the coolant temp sensor and O2 sensors are warmed up enough to provide meaningful signal??? It's been a while since I read up on this stuff.