I'm finally ready to tune this for performance! Need some advise!

Discussion in '1994 - 1995 Specific Tech' started by Zero Signal, Mar 4, 2006.

  1. Alrighty, I spent all day screwing around with the tune to get the driveability down just right. I finally got it to idle without maxxing the idle screw and it feels totally stock when under 2000rpm. No bucking, hanging idle, dying or surging :SNSign:

    So now I'm loading up the J4J1 MAF curve again since the stock curve killed my HP enough to where I can really feel it. I think the stock MAF curve is just too lean now. And untill I get the WB, I won't really know the A/F ratio either.

    BUT, I can still play with the timing. I went through the timing tables and set the spark_bdln_table to all 55 and the spark_MBT_table to 55. I stole Grady's timing tune and subtracted alittle here and there but left my max at 34° from 4k-up at full load.

    So what do you guys think? Is 34° max timing too much? I've seen up to 36° :eek: but the stock tune is less than 30°. Are there any good ways to get a ball-park tune without a dyno? :shrug:

    What's the standard method of properly tuning the A/F ratio? Changing the fuel tables or the MAF curve?

    Grady, did you tune yours ON the dyno or tune it THEN dyno it?
  2. Sounds Great :banana:

    Drivability is the hardest part of tuning anyway :D

    I'd use the Cobra, not the GT curve as it is a bit fatter.

    If your spark values you see in the dlogs don't track what you are calling for in your cal file you may need to kill the altitude table as well.

    Remember you are using iron heads and sometimes they don't take too well to the same spark values as Aluminum. Since you don't have a wb, you might wanna sneak up on values of 32 or more. Just listen for the ping thing.

    Total advance at 4K is gonna feel pretty lazy. After you get your wb and can be assured of saftey, you'll wanna get it all in quicker.

    Fuel Tables :nice:

    I only use the dyno for a final fine tune :)

    Street tuning duplicates real driving conditions or Load Factors where the dyno does not place as much load on the car.

    Since I have a wb, I can do 95% of my tuning on the street :D

    The only down side to street tuning is the speeds get quite high when dialing in your final af ratio. Second gear does not give enough data events for accurate data IMHO so the higher third gear speeds then come into play.

  3. For now I'm gonna basiclly use your timing table Grady. It seems like if I make any changes is loses performance. I had to reduce timing down low to around 9° becuase it would surge while driving around the parking lot.

    Now I can't wait to get a WB goin.
  4. Again, good to see you are making progress John :D

    When you get your wb, you'll see several things in a different light!

    I gave you some stuff that should be helpful in your other thread on the tech forum.

    I also took the opportunity to share some extra stuff I seem to get asked over and over which deals with the things you are working with at this time.

    Hope you don't mind. :)

  5. I have gt40's preaty heavly worked and shaved...as in a .065 mill:eek: . I ran 32* total...didnt want to go higher as I was having some "issues" shaking it down last summer.

    I found MASSIVE valve float...but I would start at around max of 30* then ever so little go up. I have my tables getting full spark advance at WOT or .80-ish load at around 2000-2500rpm.
  6. Yeah right now I'm maxed at 34° total at 2500 full load. I don't want to go higher untill I have the WB and get on a dyno. My heads were only milled like .020" so with I may be safe. Besides, I have it running about 20% richer than the stock J4J1 at the top end just to be conservative. I'm gonna pull the plugs after 1000 miles or so to see how they're lookin.

    Out of curiousity, how did you find that you were floating the valves? Did you have some way of measuring it indirectly? Did you see a tell-tale pattern in your datalogs? That would be great info to know.
  7. well power was WAY off when on the dyno at the start of the year...like 199rwhp with this setup...it flatlined at the "start record" point on the dyno.

    SHimmed the rockers .090 and it was a bit better. Ran a best of 14.1 @100 with 26* total at the end of the year last year...I was getting realy :( :shrug: :( .

    I took it apart this winter to focus on the rocker geo. and check the PR length with a checker PR. I was adding crane 1.7rr, and wanted to set it up proper as it was the ONLY thing I was not 100% sure on when I put it together.

    I got the correct rocker travel on the top of the valve set with the correct shims and adj. the pushrod to be set with 0 lash...or with just ever so slight drag on the adj. PR when it was adj. I used a mag-base with a dial and set the cam to mid lift and double checked everything.

    I got the adj. PR meas. (big thanks to Tmoss BTW for the help and meas. while doing this). PR came out to 6.13 in length...so I am buying a 6.15 that thankfully is avail. as a reg. PR and not a freak special order. Basicly I am sure a .100+ PR too long would cause some valve float.

    BTW I cleaned up my chamb. on my iron heads as it helps fight det. so I would still start off at like 30 or so just to be safe...you can always add it until you get the hint of det. Go to hight and you may be too late too quick.