Grumpy

I just got a new TBI setup running and thought I'd share abit about it.

For those that know me, you're aware that I'm a real junk yarder for using parts. So in getting the engine to run there were a number of false starts (no pun meant). 2 bad ecms, and 3 sets of injectors that wound up being bad. So a few hours were wasted diagnosing things, but at $20-30 for an ecm, and $50 for injectors, for what we saved, it was all worth while.

Anyway,

Once the engine started and ran, it was a matter of roughing things out for BPW (base pulse width) and fuel pressure. The injectors I wound up with were the late BBC 80. So I started at 12 PSI and tinkered till the engine ran as best as it could using a stock prom. The engine is a 355, 9.5 CR, Comp Cams 270.

With the above set, I then startedd working with the BPW, the original setting in the prom was 140 so I went in steps of 10 downwards (was rich). At 100, the engine started and ran well, and then we went for the first test drive.

The motor was a lil flat, so I added some in the higher VE areas, and since idle was 50 K.Pa, I slid the 30-40 entries over to the 50 area. I also set the idle so that it was about 20 of timing.

Next drive was a tad too rich.

So I leaned out the higher VE entries (split the difference actually), and added a little more timing in the higher VE areas.

Test drove.

Still a tad rich, and it liked the added timing.

Lessened the fuel, set the EGR enable to 255, disabled the EGR flag, and added a few more degrees.

Test drive.

Well the drivibility was right, and in cracking it open to WOT it was too rich.

Did another chip.

So there you have it. In about half a dozen chips, the car is quite drivible, and the grin factor was about a 6 (on a scale of 10).

You'll note, basically one change at a time (well a few timing changes of 2-3 degrees) and it was running, and pretty well I might add.

Yes, I've done a bunch of chips, and have an *idea* of what the car wanted, and what the tables should look like, but even if it took 2x as many attempts, it would have still been less then a dozen.

If your pretty well versed in engine work and diagnostics, then it's a matter of OBJECTIVELY looking at what you have and doing what LOGIC tells you. You'll note, I didn't try changing the prom to get the injectors to work. It was easier to change the injectors, and just make ONE CHANGE AT A TIME. I went to get the stock stuff running as well as possible parts wise, and THEN started on the chip. Again, one step (area) at a time.

Now, it's just a matter of hooking up the GTech and WB, for doing the WOT stuff, and I'd expect that to be 4-6 chips.

So there you have it. From new combo to correct chip in 12 tries.

Disclaimer:
The first chip for my first TBI took 400 tries to get right. What was PRECIOUS about that was the study time involved with each change. I dithered with things, and was **** about them, but in doing so many learned alot about how changes *felt*. In my GN it took 40 or so chips. Now in this setup a dozen. While intially you might want to hurry up, and the idea of on-the-fly-tuning sounds soo inviting, long term you'll always be chasing around, because you don't have the *seat time* or understanding of how the system actually works.
Once you get to UNDERSTANDING EFI, it's really easy. 1/2 the battle is telling you mind (ego) to shut up and sit down so you can think thru things. Remember, if it looks like a duck, walks like a duck, you don't have to hear it quack to know it's a Duck.
Gather lots of extra bits to play with. When your buying junk it's not at all expensive. For TBIs I just love finding old Cross fires. In this latest car it's a ported cross fire, with a new lid that I made out of 1/4" AL using an electric drill and files. Other then the fuel pump this conversion from CCC to TBi was less then $100 (ignoring the junk stuff). Granted I have lots of time swinging wrenches, but the point is EFI and Prom burning are no big deal. just gotta get in there and do it. If you're new at all this, be sure to get an old clunker that you can fix up a little, so that you can take your time, and never rush or burden yourself or others while doing project cars.

Whew,
L8r
Hmm, nice and sunny, I think the GN needs some exercise..

JPrevost

I'm following you're footsteps to a T.
I've been absorbing everything I can and it seems to be paying off in a big way.
I wish I had the money for a wideband o2 sensor and the parts for the boards. I guess I'll just need to keep grinding on school.
BTW, in one of my engineering classes we've got a group project due in Fortran code. The project has 8 people and the topic is my recommendation of calculating better transmission gears for 1/4 mile performance. I sit back and everybody shoots me questions and I seem to have the answers without having to think about it. I don't know what my hobby would be without thirdgen.org or the diy_eprom section. If I went carb I know I wouldn't have bothered learning about any of this stuff. Pabli, Grumpy, Glenn, Ken, Jonas, you guys ARE thirdgen.org (yeah, Dirk too, only because he's good for a laugh once in a while ).

Grumpy

1) You don't have the money NOT TO build one. Long term it will more then pay for itself in gas spent tuning a car.

2) just use the square root of the preceding gear. 1/4 mile is easy, it's all the other compromises that are a PITA *usually* speed limits or customer satisfaction.

3) Nasty thing arrogance.
Never fall into the trap of Pat answers. All that is regurgatating info., and doesn't involve thought. Ego plaement can be a good or bad thing. Way too often bad.

JPrevost

3) They ask simple questions like, why is a car faster when it's cold out. Simple stuff like that. Those questions are easy to prove, it's the tranny gear selection, traction, drivetrain rotational weight, and aerodynamics that I don't know much about. I have a gist but even told everybody, "I'm not an expert, this is just my hobby."
I even sugested that we make a LOT of assumptions considering the time we have. So time it takes to shift and the slop of the powerband is going to constant. We're going to just focas on using simple equations like the weight and hp formula that spits out a mph in the 1/4. I'm not even the team leader .
How do you know the square root is the best gear? Do you have any information to back that up? Do you know a good book or internet source that has links to formulas regarding transmission gear ratios and how they effect 1/4 performance?
I've been looking everywhere and nothing I've read so far has gone into the depth I'm looking for. The most detail I've gotten is from the board about how the closer the gears are together the less rpm is lost after a shift. I've already got a plan to figure when too many shifts would deterimental to the actual 1/4 time. We said each shift takes .25 seconds so if you had a 20 gear, you get the idea.
Any information would be greatly appreciated.