back from the track again

Chris

I've seen the threads that say those heads have been milled a pretty good amount.

Couple of Q's about your valve train.

1) have you marked a valve tip and checked the geom?
2) have you used a dial indicator to see if you are getting the correct amount of valve travel?

A Q about your combo's ability to take total spark advance if you will.

What is the total amount of spark you can use in the highest load rows of your spark table without ping? Not every combo is the same but for most combos I've tuned ...... total advance right to the point of ping and then a value of -1 or -2 would produce the best wot performance verified by 1/4 strip times.

Grady

blksn955.o said:

(Greg actually I wont hold it against you, I am horrible with names)

Click to expand...

I knew that but just was not thinking straight, ...... Sorry Greg.

I am going to tear into the valvetrain realy, realy soon. I have an adj. checker and am going to be swapping on a set of 1.7rr (why I have been waiting due to the wanting to get it correct for the 1.7 and not the 1.6). I plan on doing all that you listed when I do the adj. along with using a solid lifter. My heads have a hefty shave and my block deck also has a mill so I know I need a fair bit shorter pushrod. Right now I have 90 in shims and I have some noise/taping and do not want to cause any damage so I am going to do this I hope in the next few weeks or before the month is over.

Click to expand...

It will be interesting to see what you find.

I am beginning to wonder if I am not setting up my tweecer for full control in the spark tables. In my datalog I am showing the increase in spark but the perf. is not there plus I have not heard any signs of det./ping. The highest I have gone timing wise is 32. I have the base and alt. set to the same values, MBT and Boarderline are set to 55's (just 2 of them the base ones)

That last tune has the factory spark (at what 26*) and A/F table (isnt that at like 11.2 or something) and ran 2mph faster than a tune that runs 32* and 12.8.

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If your dlogs show you what you wanna see, I don't know why there would be anything wrong with your Tweecer.

As for your fuel ratio, only a wb can tell you for sure as you all too well know.

Grady

Greg

When I started to tune the sig combo as you see it, here are some of the things I found out by experience.

Drivability was my first goal and then I went for max wot power. Having said that, I don't have any reference for wot performance with each file or a way to compare them to each other.

I worked with the t4m0 cal file for about a week and made little progress with drivability issues and you better believe that I had a bunch of em.

I then moved to the j4j1 cal file with the following tweecs:

t4m0 maf curve
low inj slope at 36
high inj slope at 30
t4m0 break point
inj offsets for 30's

Drivability was much better and if I had to guess at a number, I'd say it would be about 85% of the drivability gremlins were gone with that one quick upload of the j4j1 cal file.

At this point in time I knew I would not go back to the t4m0.

The GT file just sucked big time compared to the Cobra file.

I then worked on the tb air flow and ISC neutral idle air flow function values for a more steady idle.

At this time I had pretty good drivability with a slight surge at idle every once and a while and a slight bucking at light load cruise conditions.

I then turned my efforts to wot tuning.

I dialed the spark back a good bit for safety and made several mid throttle blasts for a base line dlog.

Did the same for two thirds throttle and wot as well.

All base line dlogs showed to be too fat.

I killed the high speed fuel enrichment function and set the stabilized OL fuel table for 12.25 in the top two load rows for a fat but safe place to start wot tuning.

To keep it short and not make this too long .............................................
I tweeced (or tweecered ... as JT calls it, lol) the wot part of the maf curve to the point of where my wb matched the lambse (commanded) value in the top two rows of that table.

At this point in time I knew the wot af ratio was fat but safe.

IIRC, I made the first wot blast with total spark advance value at about 30. This was the first time I had pushed things with the new stuff and it was pretty strong I must say but my dlogs showed I was very close to pegging the little stocker maf, lol.

I just played with the spark and fuel knobs a bit more for the best wot power and that, I guess, is all there is to tell.

In a nutshell as they say ... Just the basic stuff I went through.

Grady

blksn955.o said:

hmmm.

my tune in the j4j1

t4m0 MAFtransfer
stock breakpoint
stock slopes
offset left alone

ran great drivability wise no bucking, the dyno showed commanded A/F was spot on.
--------------------------------------------------------------
1st t4m0

t4m0 MAF transfer
j4j1 slopes
j4j1 breakpoint
j4j1 offsets
-----------------------------------------------------------------
the tune that ran better with alot less timing and alot fatter fuel.

t4m0

t4m0 MAF transfer
just quick 24.xxx and x 1.2 for a quick slopes so it would idle/ect.
t4m0 breakpoint - only time I have used this breakpoint in any tune
j4j1 offsets for 24's
----------------------------------------------------------------------

I wonder if the t4m0 breakpoint should be used with the t4m0 MAF transfer, realy that is the only diff. if I have my spark tables set up properly.

Click to expand...

I do see one thing that is common from the things you have said Greg.

Cobra files give best drivability but GT files give best power. I have seen many others say the same.

My thoughts on those findings are this .......................

You see lots of peeps say the GT has less fuel and more spark but for the most part, that is a closed loop kinda deal. At wot or high load open loop conditions, the differences between the two is not that much if you look at the tables.

I just knew that drivability issues were gonna be way harder to get right than wot performance cause after all, all you need for good wot performance is two things only ..........................
Best amount of fuel
Best amount of spark

When the Cobra file seemed to make my life easier I went with it in a heartbeat, lol.

As for the breakpoint ..........................

Over the years I've seen the thinking change some what about that topic.

Peeps used to say it had no effect in the Cobra file due to the slopes matching. Then peeps started to say ...... bla, bla, bla.

My thought about things like this is kinda like this ...................

Who is right and who is wrong? Lots of times both camps of thought have things to say that make sense.

I usually pick the one that makes the most sense and put it all in place and see what the dlogs tell me. That is the proof I need to tell me which way to go.

I use 30's and most use 24's and that could make a difference for sure but I can tell you this.

I have set up files with the inj values that follow the j4j1 pattern and I have set up files with inj values that follow the t4m0 pattern. The big difference was the offsets have to be greater if the slopes are different.

My advice to you is just try different values for the breakpoint and see if you get better results with those changes.

One last thing about the differences in the files.

I have always thought those who said the j4j1 would not work for them had their focus on max power and did not take the time to work things out with the j4j1

or

they were not as demanding as me when talking about drivability.

I'm done now, lol.

Grady

When i went from my stock comp to the Tweecer i didnt notice much of a difference power wise, i started right away with the J4J1. I dont really see how either one could make you faster at WOT, if you tweec it. All there really is to WOT performance like grady said is the timing and fuel. The breakpoint is imporant for drivability but either comp is gonna be in the high slope if you are at WOT, so then all that comes into play is the Timing and the Fuel Tables, and since most of us change them it doesnt matter which comp you use, because they will be the same for WOT performance. So because the J4J1 has better drivability its the logical choice.

Right, Im using a Pro-M MAF so i have the Curve loaded with the stock J4J1 breakpoint, i wonder how they are reacting together. The thing is all the breakpoint is is when the comp switches from the low slope to the high slope. Something would have to be very out of place for it to somehow stay in the low slope. A bad breakpont would only really lead to driveability problems.

So you are using each computers stock Timing tables? Because the stock GT one is better than the stock cobra timing table.