A 3.4 DOHC Build then... F40 Turbo (Page 30/57)
Fierobsessed NOV 08, 06:13 PM
I decided to make a timing table with a REALLY conservative boost section, keeping the degrees low for the time being. Ill test that sometime this weekend.

I learned something about my car today. I bypassed the boost controller, so that it was intake pressure acting directly on the half bar wastegate spring. Turns out, I think that the sound I thought might be compressor surge may actually be the unique sound that my wastegate makes when it opens. The wastegate solenoid seems to have been fluttering the opening of the wastegate. Bypassing it smoothed out the opening of the wastegate so that instead of the fluttery sound I was hearing, its more of a steady sound of high velocity air through a corrugated pipe. Which is what my wastegate dump flex is. So maybe I was mis judging it. I'll look into it some more later.

I'm going to work on my fueling tables in open loop via the wide band, and get them dialed in with conservative timing. Hopefully this strategy will keep knock at bay while I get the tables dialed in. I'm hoping I can achieve the boost levels I want, then step in some timing to make some more power. I'm just a bit worried about the pistons though. Down the line I plan on a forged bottom end, I'm just hoping that I dont have to sacrifice this engine to the tuning gods.
sspeedstreet NOV 08, 08:13 PM

quote
Originally posted by Fierobsessed:

But... once you remove the decklid, you're confronted with this catastrophe.



I replaced my cam covers (1992) with ones from the '96-'97 design motor. First off, they use stiff rubber sleeves instead of rigid plastic on the later plug wires. They bend enough to clear the rear window shelf without lowering the motor. A second benefit is their umbrella design that fits over a vertical wall cast into the covers. My original covers leaked badly when water got onto the motor; these seal completely.

~Neil
Fierobsessed NOV 09, 07:18 PM
Ah, yes! I remember those later wires. I actually like the early wires in the back, but the newer ones for the front. I live in Las Vegas, so rain isn't much of an issue. I also found by chance, an original decklid recall weatherstrip in the U-Pull yard. So that is my only defense against water. And it hasn't been an issue. I also am a bit liberal with my Dielectric grease on this engine.

This is my second 3.4 DOHC fiero, I used to have an 85 coupe with a 96 engine. Living in rainy Long Island, I had noting but problems with the front three all the time. Here, it's just never been an issue.
Silicoan86 NOV 10, 02:17 AM
I've also had issues with water getting in the front 3 plugs on mine, even with the recall strip attached to the decklid. It got to the point where the car was misfiring so badly that I couldn't drive it. About two months ago I had to come up with a solution, even if just temporary - but enough to get me through the rest of the season with the car.

I quickly made a cover out of aluminum to prevent water from getting in there. I didn't spend much time on it so it's not pretty, but it'll keep water out till I come up with a more permanent solution during the off season (which has now arrived here in MN). I tested it with a car wash and the plugs and valve cover were bone dry afterwards.

Joseph Upson NOV 10, 09:28 AM

quote
Originally posted by Fierobsessed:
It drives great in open loop, terrible In closed loop. I have my work cut out for me tuning wise.



It took me a while to get closedloop working pretty well, the biggest problem being a stable idle and fighting the stall saver spark control to get there. I recently switched back to openloop because of the occasional idle hunt that would result from turning on the A/C, which raising idle rpm pretty much resolved but I like to keep idle near 875- 900 rpm as opposed to just shy of 1000 and at the lower limit is where most of the trouble occurred. There are so many tables with obscure titles that can actually act inversely to what the title suggests, so you can make a problem worse before figuring out you need to go in the opposite direction. If all of the major tables were defined regarding their actual function the tuning process wouldn't be so testy.

Be sure to tease out your spark dwell tables, Robertsaar did that for me and after an article with data on ignition coil dwell time relative to other load factors suggested I should adjust mine upward closer to 7 ms, I have not had another episode of spark blowout (misfire) boosting in excess of 15 psi after doing so.
Fierobsessed NOV 13, 01:53 PM
Thanks for the tips. Most of the issues I've been seeing in closed loop idle appear to be excessive changes in injector pulse width. Which I assume is because I have rather large (60 lb) injectors. So I need to figure out what table or value needs to be tweaked to trim down the size of the changes in PW based on o2 swings. It just doesn't seem to like running at 13.5 - 14.7:1 at idle, It just suddenly shuts down very abruptly. 11.5 or so, runs beautifully, but that's not really what I want I'll try running the idle spark compensators from a 3.4 DOHC code and see if that helps.

Isn't dwell hard coded in the software? I cant find any reference to any tables or values at all for dwell. There are a hand full of dwell values in a small chunk of code, but It's a little hard to decipher exactly what they mean or do, or when they are called.
Joseph Upson NOV 13, 08:55 PM

quote
Originally posted by Fierobsessed:
Thanks for the tips. Most of the issues I've been seeing in closed loop idle appear to be excessive changes in injector pulse width. Which I assume is because I have rather large (60 lb) injectors. So I need to figure out what table or value needs to be tweaked to trim down the size of the changes in PW based on o2 swings. It just doesn't seem to like running at 13.5 - 14.7:1 at idle, It just suddenly shuts down very abruptly. 11.5 or so, runs beautifully, but that's not really what I want I'll try running the idle spark compensators from a 3.4 DOHC code and see if that helps.

Isn't dwell hard coded in the software? I cant find any reference to any tables or values at all for dwell. There are a hand full of dwell values in a small chunk of code, but It's a little hard to decipher exactly what they mean or do, or when they are called.



I had trouble at idle with the 60s so I can imagine what you're probably going through with even less displacement, especially if you are running a base fuel pressure in the stock 50 psi range. It's very strange but yes there is something about attempting to run stoich AFR at idle that the motors do not like and usually it manifests with a rough idle although the rpm maybe stable. You basically need to give it what it wants until you find the balance as there appears to be some fine tuning fuel delivery that I don't believe the wideband can pick up but you can feel the difference.

The tables I had to work with before my idle AFR would even budge toward stoich from a low AFR are:
FUEL INJ OFFSET VS. FUEL PUMP VOLTAGE

You're dealing with injectors that are newer and different in their characteristics relative to stock, I had to lower values to get my AFR to come up at idle as trying to do it via the idle fuel table was not working to the point where I thought the table was useless and when I adjusted the fuel table enough to get a response the results were poor and erratic. Setup a history table that tracks your pump voltage in the idle range so you'll know what your pump is seeing. You'll be able to observe the cell follower as voltage changes and note whether you need to increase or decrease fuel based on where the voltage sits with various loads on the system.

FUEL INJECTOR OFFSET VS. BASE PULSE WIDTH

This table may end up needing to be tapered off after 1 or 2 cells because theoretically larger injectors take slightly more time to open initially having more surface area pressure to overcome and weight of mechanical parts after which it tends to deliver a bit more fuel than the smaller injectors as it operates with the same linearity. I used this table to help with fine tuning things like the cooling fan and A/C coming on where the BPW would jump in desired amount.

I've been able to achieve idle AFR in the 13s but much more than that and it gets unstable in closed loop with electric loads switching on and off. Make sure you have no vacuum leaks of any kind, the problems come on slowly and progressive and can throw you for a loop until you discover how easy they can develop. I used the stock bolts in the exhaust manifolds and they made me pay about every 3 months. I have studs on the way now as it was a real headache to get at bolts barely accessible for tightening. I see you've nailed that one already.
RobertISaar NOV 13, 09:01 PM
look for "prop" tables..... they're highly involved with the injector skewing for closed loop control. there are also scalars that can come into play, especially at idle, though i would need to check my notes to see if they're actually enabled in 8F.

dwell..... those values are kind of hidden in the code, not sure of the best way to post info on them other than grabbing my disassembly and posting the entire section of code.
Fierobsessed NOV 13, 10:35 PM
I spent a long morning trying to tune idle. What a pain! And I agree with what you are saying. I'm clearly following your experiences.

What I am coming across is tweaking the idle VE table is getting me to 11.5-12.0 once it gets just a little higher than that it becomes completely unstable. It doesn't feel like the pulse width, nor the AFR's are reacting to subtle table changes, but rather large changes, and then when I get close, the AFR's suddenly jump, and the engine stalls. I tried zeroing out the idle spark compensator tables, then made the small area in the idle sweet spot in the main timing table flat. This gave me completely stable timing fixed at 23 degrees. Which is what the 3.1 had in the sweet spot. This made the car have an extremely stable idle, but only when pig rich 11.3-11.5. Any higher AFR than that it starts surging and it dies. I'm going to mess with the timing value some tomorrow, and try the voltage injector offset thing while I'm at it. I've found that the EGR BPW compensation table stops effecting the fueling at right around 40-41. So I can't trim any more fuel out there. It was frustrating to try to get the idle tuned in. I feel like I've made no progress, but I am learning a lot in the process.

I've been working on 8F for a bit, I know the code fairly well. It definitely can do what I am asking it to In modified form. But trying to get the idle figured out is testing my patience. It has left me wondering which tables are truly active while idling. And, whether I am hitting limits as I'm tweaking things in. I'm not sure if there are any pulse width limitations on the injectors in synchronous firing. I'll have to consult my hack for a while.

These are things that will be the death of me! But I'll keep working on it! Thanks against for the suggestions guys! You've given me some more things to try out.
Joseph Upson NOV 14, 06:22 AM
AFR VS COOLANT TEMP FOR COLD ENGINE AND CLOSED THROTTLE

Keep that table in mind, as you start to adjust tables that globally affect fueling at startup you may eventually encounter a problem with cold starts. Watch your BPW value in Tunerpro just before cranking, if the value is red and the motor starts without issue it should be fine, if it smells pretty rich you may need to reduce fueling (raise value actually) in this table some. If you encounter a problem where the motor starts okay but shortly after starts to run increasingly lean for a while and then returns to normal it is most likely this table and the lean problem lasts until it times out. I've tried the base pulse vs TPS table but found this one more effective since the TPS table did not appear to be time oriented and therefore did not fix the lean outs after starting.

[This message has been edited by Joseph Upson (edited 11-14-2013).]