First, let me thank all of the contributors here - while I still feel quite lost somedays, searching and reading the posts here has provided me with a great base knowledge and lots of ideas.

Here's my situation - I have a fresh 355 with 10.5:1 compression and a 110 LSA cam under a ported cross-fire system in an 83 camaro. (I can provide more detailed info if requested) The stock ECM ('6026) runs substantially rich at idle, but still has good throttle response. I have an '8746 with the Harness Adaptor Module that allows it to connect to my original harness.

I have tried a few stock bins from the '8746, although none of them has the same feel as the stock ecm.

I've done quite a bit of datalogging, and took the "police" bin and started trying to tune the VE tables. I did improve some of the 108 BLMS, but the current symptoms are that the car still runs way rich at idle or very light cruise. If I just let the car idle, even with significant VE% reductions, the average will hit 108 over time.

As I was reducing the VE percentages, I started having a stumble as I would begin open the throttle blades. I then started adding "pump shot" by experimenting with both pump shot tables. I could lessen the condition, but not remove it entirely. Sometimes the stumble is accompanied by a pop from the intake.

I plan to have a fuel pressure gauge on the car within the next month, and I will be buying a wide band o2 sensor (Innovate?) in February or March.

I've done lots of reading, on different tuning strategies, but at the moment, don't have a clear set of next steps.

Some of the questions rattling around in my head are:

1) Which bin should I use as a base?

2) Do i have a physical problem, or a prom issue that is causing the stumble as I start to accelerate?

3) Would a wide band help diagnose this issue, and if so, how would I use it? Would I watch the output as the car stumbled, then determine lean / rich?

4) I have not worked with timing - should I prioritize this over fuel? I need to read more of the tuning strategies for timing - at the moment, I would only increase to knock, then back off a bit, not sure if this is the best way.

5) At WOT, I get all 128s - is this a true reading?


The car clearly is not performing as well as it should given other comparison cars (Last run was a 15.0 with poor traction). I have a set of throttle bodies and larger injectors (has the stock 305 injectors today) ready to be installed, but I thought that if i couldn't tune this setup, I shouldn't introduce more variables.

If anyone wants to help me answer those questions to build a plan, or point out some errors in my logic, I'm all ears.

Thanks!
Ian

 

Are you using the stock CrossFire Injectors?.
Did you know they are two different sizes?.

I'd suggest you first split the fuel lines so the Throttle Bodies are in pararrel rather then in series, and then use a set of injectors from an 8746 application.
Then start tuning.

Y-ing the fuel system is going to take some $$, and money. The AN bits to do it, get kinda pricey, as well as having to get a remote FPR.

That'd be what I recommend doing first.
BTW, I had a CF running mid 13s..

 

Yes, staggered original stock injectors. I have a set of the early bbc injectors on my desk at home waiting for install with the 2" throttle bodies.

Which regulator did you run, and did you run it at a set pressure, or variable with vacuum? There is an aeromotive one that gets discussed over at the crossfire forum - Aeromotive 13301 @ SummitRacing


My engine setup is pretty close to your firebird - a little more compression, but similar heads (i've got iron World Torquer 305s, I believe you had aluminum vette heads) - I've got the xe268 cam, I think you had the 270 from memory... I can only hope I see results close to yours within significant amounts of tuning.

Thanks for the recommendation

 

if you have stock 305 injectors i dont think they will work on a modded 355? i had to replace stock 350 injectors and go to 90 lbs to make car run so-so. now that cam will confuse the ECU especially low map. that may account for the rich down low. it did that to me. datalogging was super rich on bottom end and lean on top with 90 lbs with proper BPW for FP/ injector size day one. i think any 350 cid TBI bin will work with corrections. there are a couple on the crossfire forum to borrow. i would guess no mechanical problems just out of tune. at WOT i dont believe you can datalog in tradditional sence. it does not use the 02 for feedback just adds onto base table xtra fuel in PE/WOT. wide band should help but dont do WOT till you have the bottom close. i just ordered the WB so will play with that in spring. i used stock gm tables to start for spark. only took away spark where i saw KC did not advance spark from stock yet. stumble may get better as you tune. i too had stumble that adding pumpshot helped. i assume i am not masking another probem and needed the PS due to my intake flow.

 

You can datalog at WOT in the traditional sense, I think you're confusing (as I have) closed loop and open loop datalog results.

There's a recent TRAXION thread that deals with this, and he has posted in another thread where I couldn't understand why a datalog was showing closed loop, but locking BLM's at 128.

Ian, as I understand it, you're getting 128 BLMs under WOT conditions because you're in PE mode, not because your VE's are correct.

John

 

John??? Are you suggesting running open loop all the time? Then the 02 is not functional? Or running closed loop and relying on the 02 sensor to provide you with data in PE. That confuses me! Does the 02 sensor provides a voltage reading in PE? if so is is at all reliable? I was of opinion it is so far off outside of stoich that you may as well disregard? I have an A/F gauge hooked up to 02 and it pegs rich at WOT so apparently the 02 sensor is putting out voltage. my wide band is on order and shoud have in a few days. Are there any postings here as to whether the A/F ratio in PE/WOT shoots right to 12.5 or 13.0/1 or is a gradual progression form 14.7 in closed to 13.0 as the rpms come up to redline? in other words i will be tuning PE A/F but need to know what to shhot for. i see stock GM PE WOT is gradual enleanment and rich at 12.0/1 in bin.

 

I ordered the aeromotive fpr today - will start collecting all the parts to get the fuel lines run with it - will install the larger tb's and 80# injectors in a parallel setup within the next few weeks.

Ian

 

check into aeroquip fittings with push on fuel lines. makes job a whole lot easier.

 

Ok, I have all the pieces back together - running 80# injectors on 2" tbs with parallel plumbing and the aeromotive fpr.

I'm having a huge issue with tip-in lean spikes - currently playing with the pump shot settings, although I've added HUGE increases with only minimal improvement.

I will be replacing the fuel pump soon since I added a fuel pressure gauge, and I think the problem may be the pumps inability to keep up with sudden changes.

Grumpy, did you need signifcantly larger pump shot settings (than the stock bins) with that cam and the 7747 application?

Thanks all!

Ian