choke adjustment on 7747

[hammertime371]

ya saw that one as well but i figured that was gonna be to much. i have a stock regulater that has been made adjustable. I think maybe i just take the spring out and stretch it some and retry it. i got everything i should need so i dont see why it dont work right.

[EagleMark]

With one pump doing the job correctly maybe it's time to do a data log? Have to reset your BPW to correct for that pressure.

[hammertime371]

ok well it was 121...thats for 20 psi right? the best im getting is 19 so more like 122 or 123? i did go back to bin correction 4 which was 121 and been driving on that. had a couple backfires this morrning but not as bad as it was befor. its just annoying that things arent working as they should. maybe put a quarter under the spring and check it again

[EagleMark]

19 PSI is 116 BPW at 95% VE is 280 HP

20 PSI is 113 BPW at 95% VE is 288 HP

23 PSI is 106 BPW at 95% VE is 308 HP

We were above 100% on VE tables and still lean... untill you get a new spring you may as well give it a shot and see if one proper pump can supply fuel needed.

121 was testing adding to BPW for more fuel which didn't help... it made low end rich and high end lean...

[hammertime371]

so i was checking out an extra tbi i have and I have come up with a way to bench test the spring. rather simple actually so ill take a pic and show ya after i make it tommorrow. this way i can find out whats going on

[hammertime371]

ok so i made some mods and im getting 21 psi to 25psi with this spring combo. made a special cup to hold both springs so on the bench im getting good pressures. ill install it tommorrow and test again

[hammertime371]

check this log. 22psi with 108 pw. used bin corection 6

[EagleMark]

Hey! Your not only in the ballpark your in the infield!


How did it drive? Was cold start OK? Any issues?

Only issue with that datalog was it had some VE over 95 to start in that bin. But your so close all you need to do is one final data log with attached bin and you'll be done. Really you could call it quits time...

But you seem to be having fun with this and with the ease of fuel pressure adjustment you have... if I had my hands on it I would add 1-2 more PSI, adjust BPW, then do last datalog described below. This will get VE away from the high 95s.

Warm up and drive a little like you have been doing but this time stop and pull batterey cable for a minute to clear learn. Connect, start truck and when it goes closed loop start data log and do like you have. With that we can adjust/check VE and turn stuff back on.

Then you can look for little issues like if it's still popping at cold start etc...

How did your test pressure on bench with air compare to test pressure on truck with fuel?

That's a neat setup for testing. But the little cable and knob is SWEET! Did you build that? Does it just stay on there?

[hammertime371]

lol...you like my flow test huh... i tested with air. actually it shows 21 psi with air but with fuel it shows 22psi. not sure why but its close enough for me. the regulator diaphram has flutter with air so maybe thats why. ill send ya the aluminum block i made if you want 1. its very simple to make if you have drill press or milling machine. the adjuster for the pump spring is just brake line with a piece of speedo cable inside. i made the knob on the end and it does stay connected all the time. it was way to hard to take the tbi off every time to change fuel pressure. i can get up to 25psi with the duel spring. its a stock spring with the extra added in. the spring i bought from ebay is clearly stronger than the stock so im not sure why that didnt work. but mark you helped me out greatly please feel free to ask me for some thing you need made. I sit in the machine shop and find ways to fix things that other people mess up. So making this stuff is no problem. Im just not good at or have the time to figure out what you already know about tuning. this was my first injection project and ive been working on it since december. I have another in the works that should bring 400 or so hp to the table. ill do as you suggested and another log. it drove nicely but idle seems to be rough. almost lopey like a big cam would be. didnt get any pops today but it was warm this morning about 70.

[hammertime371]

I still see high knock counts so is that something to check out?

[EagleMark]

No where near as many as when you had the 10K switch on and added 10 degrees...

Knock is hard to detect on 7747 as it's an accumulater so theres always counts. Even a stock motor with 10 degrees removed from stock table gets counts WOT... I'll look at your log in morning, have to watch for incresing numbers in an area while data tracing the spark table.

Next hack is spark retard! Then you can see if it's .09 degrees which is nothing or 8.0 which is an issue!

Where's your distributor set?

[hammertime371]

the disributor is set at 0 degrees.

[EagleMark]

I do think some of that knock is real. I took 2-4 degrees out, maybe do to trucks weight over the car I used to build that table in.

But I thought you had Vortec haeds and cam? That was why we were needing so much fuel... spark table is getting closer to stock heads...

This bin, same as last but spark removed, ready for data!

[hammertime371]

lol the heads are vortec with the small valves. the cam is crane. the heads are probly only better than stock. about 10cc smaller chamber and they flow better with larger runners then stock. the wife dont want me messin with it today! ill send ya a log monday

[hammertime371]

can out this morning to add some pressure to find that its already at 30psi when cold...it started to come down as it warmd up. not sure why but im thinkin maybe a block off plate for the regulator and ill get and external regulator thats more reliable... if i rev the throttle quick it misses. much like when ya got the wrong accel pump cam on a holley