I guess I've been preaching prom tuning here the last couple days, but you guys that want your TBI motors to haul got to know this. You can mod your motor, but if you dont tune it after words you will get the dissapointing results that give TBI a bad name.
Case in point.

I wanted to use my Gtec and do 0-60s to accuritly measure response to WOT chip adjustments to a particular block in the AFR fuel table. The only problem is that I have wheel spin all the way through first gear now, and I didn't know how to get the tires planted so I could have consistant runs. The area I was wanting to tune was 4000 and above. I ended up taking 15* of timing out of the main timing chart below 3600 RPM at WOT. The first time I tried it the car left the line with about 2' of spinning and hooked up. When it hit the normal timing at 3600 the difference was like a 125 shot of NOS. It spun alittle but not to bad (I was allready rolling and above my TC stall speed of 2000). This did enable me to get consistant back to back runs and make adjustments. Buy the time I got the AFR right it was smoking the tires when it hit the timing.

This was a timing chart that I had tuned to this cam when I had it in a lo3. I'm tuning a 357 now.

Heres my point. Removing 15* of timing made my car fall flat on its face off the line till it hit normal timing at 3600. At 3600 it went from ho-hum to smoking tires with nothing but a change in timing. I am running about 12* more timming at WOT then the stock Lo3 bin, and 17* more then the cop car bin. If you dont chip tune you are in compromise. You might argue that you can just change your base timing and use AFPR to get the fuel right at WOT. You can if you want to tune just one area. After a moderate cam change your idle and light cruise (highway) will be rich and your WOT lean. Mine is a daily driver and I need everything working right. Especially at $2.00 a gal.

 

***, i cant wait to get my bird flying right so that i can start getting in the ecm... first time 'playing' with proms...

 

Hey JokerRS, how was it all in all tuning in that engine combo, specifically the ZZ4's powerband. I'm still contemplating whether or not I should throw it in my motor. If you are having success with it, that may sway my choice. Maybe if I swap in the cam you could give me some tips for it?

 

I would love to see those kinds of gains. After my mods (heads, cam and headers) I'm only running a 16.2.

I need tuning bad. I read the articles and I just don't get it. It's not sinking in.

 

Hang in there man. We have some people here writing some tuning stuff for TBI cars and should be in the sticky in a week or so to help novice tuners out.

 

Yeah, I cant wait till I get into the prom stuff. I am running 16.1's now bone stock, But I bet I could get a big increase if I got into the ECM.

 

BTW? Where in the buckeye state are you located and what track do you run at?

 

I tuned mine (383/AFR/roller/crossfire/7747) on a dyno and picked up 60rwhp with a change of 4 degrees in timing above 2800rpm.
There's a lot to gain from having the timing table correct.

 

looks like a gtech is in near future. getting back to jokers post it would seem a set of street slicks would help you hook up as well and allow more timing under 3600 rpms. if i launch at 2400 tires smoke badly but goes. at 2000 tires break loose but when hook up the car stalls(stumbles). maybe i need more advance sooner for a 2000 launch. better gears would be a help too as the engine is loaded with 3.08 gears.

 

It was easier the second time. The first time was in my Lo3 and I was new to tunning. It took longer to tune the timing then the fuel. This time I allready had a timing chart that was close. I did have to take a couple degs this time arround out because of knock ( I'm running more compression). What are you wanting to put a ZZ4 cam in?

Ronny, I put the timing back into the lowwer RPMs of the chip after I was done tuning the AFR table. Ya, I'm woundering about BF goodrich drag radials, but thats another board. I have done zero traction mods so that will be next. Keep in mind also that this is my (summertime) daily driver / stress relief so I wont be getting to radical.

 

Well, I have a stock L98 longblock. So its the stock iron heads 64cc and I'll probably give them a valve job. Then I'll have headers and full exhaust along with a Holley intake (also have some 65# injectors) and my 3.42 gears. I think it will be a nice setup, but that ZZ4 cam would really be nice. I think we'd have very similar setups then, other than the heads.

I was planning on leaving in the stock cam but my thoughts are that I'll be happy with the power for a while then just want more, so maybe I"ll just cam it while the engine's sitting on the stand. This will take some thinking to decide!

 

A cam swap is much easier on the stand!

 

Tuning a ZZ4 cam in a 350 goes better then in a 305. The smaller displacement of the 305 makes the cam act much bigger then it is.
You gota do it! If you don't do it now, you'll hate yourself later when you see that tuning aint that bad. I'm telling you that the torque is obscene! I am running a 2000 stall lock up TC so that helps in the torque department also. I got a fairly smooth idle and great drivability. I am running my 65# injectors at 25psi and I got plenty of fuel. I got a 48mm TBI and I am getting alittle short on air right on top end (about 95 kps at 6000rpm) I think 98 kps = 1.5" Hg . I still got to shave my trottle shaft and see if I can get just alittle more air. I got so much torque I'm shifting at 5500 anyway. You probably should plan on a 2" TBI unit for you 350.

 

Well, you guys may have convinced me. I'll have to machine the heads too, so I'll look into the costs of all this first.

JokerRS, you think you could PM me a copy of your bin so I could take a look at what you've done to get an idea of roughly what needs to be changed and by how much. That'd help me get a good insight on it.

 

Joker: nice to see 95 map at 6000 rpms. my cam is going in soon and it is 5800 rpms with current 2.00 inch TB(crossfire) converted to 7.4 L TB unit. 350 cid at 6000 rpms seems the upper limit for 2.00 TB. guess i wont need the Holley 900 !

 

Joker, I have encounter much the same thing with my tbi 350. I spent hours and many miles doing wot runs with my WBO2 and although it helped to get it dialed in at approx 12.5 afr, it wasn't till i started playing with the timing tables that I really noticed a difference. I did the same thing you did after many attempts and found a sweet spot in the timing chart by taking out timing below 60kpa and below 3600 rpm that just kicks *** when I hit it. I am still having a hell of a time with WOT timing though! I am gonna try what you did but the problem I am having is the ecm uses the last values in the tables for over 3600 rpm and you just end up with a compromise at higher rpms.
I used jon's program to get the ECM to spit out knock retard and that is what got me to pull timing out down low.
I am gonna try using some of the values you mentioned at higher RPMS to see what happens.

Of course, I would love to see your spark table but understand that stuff is kinda sensitive...........bob

 

Gotta be careful. Not saying your wrong, but, you can get to where your overfueling the motor, and actually raising the Compression Ratio with the extra fuel. And then with a bunch of extra timing, you can get some short term impressive results. Short term meaning eventually knocking the ring land above the top ring off.

One of the most difficult things to get about timing, is running as little as possible while retaining best performance. Pro racing and that sort of thing, they often go for threshold of detonation tuning, but, they know plug readings, and don't depend on a knock sensor. BTW, a Knock Sensor can be fooled.

 

ya, I been thinking along the lines of backing the timing off slightly and see what happens. Was even thinking of using that extended spark rpm slope thing and ad a negative 1* each 1k above 3600 to see if it pulls any harder in 2nd and 3rd gear. Right now my max WOT timing is 31* at 3600. That seems low enough to not cause damage . I've heard of alot people using 32*-34* total advance. I'm certanly open to opinions though

 

joker, I took your advice and plugged in the stock 305 speed spark values and I was amazed at how well it performed. I was working with the cop chip table and had modifed that but I guess that was the wrong way to go. I am going to start again but use the 305 bin as a startr. Also, the cop bin was for an automatic and the 305 bin i have is for a 5 speed I think (AXKU) but I am not sure if its for tbi or tpi. Anyway, looks like it has potential..Glad you made this post.......bob

 

I've got a laptop, the cable from AKM Cables and WinALDL. What else do I need to buy to tune my car? I'd like to get that Rom or Promuator thing where I can tune on the go. Is that the only other thing I need to buy for now?

 

Joker- just wondering..... above 3600 RPMs @ WOT what is your total timing now? Initial @ distributor + computer supplied timing = ????

When tuning a non-computer controlled (carbureted) setup it's pretty common to shoot for something like 32-36* from about 3000 on up @ WOT as a good roughly-right starting point on most motors.

Would love to know how closely your programming tables would line up with what a well tuned mechanical/vacuum advance distributor would give.

 

i'm at about 36* WOT, it backs off to about 32* by 6k. at idle i am at about 24* total, and at full timing by 3k it ramps up from idle to 3k, then slowly backs off

 

my base timing (with the wire unpluged) is zero. For simpicity reasons I put all the timing in the chip. My total timing at WOT is 31* @ 3600 rpm. I have close to 10-1 compression and run 89 octain gas.
Dewey how are you backing of the timing? have you extended your chart or are you using another means?
I had my timing a little higher at 3600 but backed it off because it needed less above 4000.

 

That is a good question. Dewey, are you romless, or using another ECM?