Completed Project My 98 super charged EX

[CDW6212R]

Was that 1-3 shift something that was changed in the tune just before the event? How close are the 2nd and 3rd shifts in MPH? Is the 2nd gear so close in ratio that it possibly can be too close or unneeded? I'd like to have a close ratio trans, but we have what is available. The 4-speed 4R70W has a wider ratio, with the biggest gap between 2nd and 3rd.

 

[ahodges]

That's too bad, for a split second when I only read the times I thought "I still have a chance!". Not.. he missed a gear, no wonder.. LOL

 

[CDW6212R]

It's so fast it's skipping gears.

 

[4pointslow]

Gears

Here is a screenshot of one of the datalogs. It shows the commanded gear going from 1 to 3, then 4 and after the throttle is let off it goes to 5th.
There is a bunch of other stuff in the screenshot like spark timing being pulled between 3-4 shift to protect the transmission, and the torque converter locking up late.

When it is cold out (40F), traction is a little different so I end up screeching tires a little off the line. That causes me to hit rev limiter so I adjust the shifts and get the 2-3 shift so close to the 1-2 that it sometimes skips 2. It is even worse when it gets warmer and I have not retuned the shift points, skips 2 at wot every time.
The 2-3 was only 2 mph away from 1-2. Remember it(shift schedule) is only a command, it takes longer to actually complete the shift. When I got home I changed it to 4 mph apart, we will see how that goes.
The rpm drop is only 1,000 rpms from 1-2, and 2-3. 4 is a 2,000 rpm drop from 6,000 to 4,000.

Only 65% duty cycle on the 60lb injectors.

 

[ahodges]

Cool stuff! That's awesome that you only have a 1,000 RPM change from 1st to 2nd and 2nd to 3rd gears.

 

[4pointslow]

Normal shifting

Here is a screenshot of a datalog from last year in September, this is what it normally looks like.

 

[Dono]

That's actually a really cool graph. Shows the lag between commanded and actual amazingly perfectly.

 

[4pointslow]

Test and Tune

Made it to Atco for test and tune, I ran the truck and it was not skipping second since I changed the shift points. The shifts were happening at 5400 though. I tried adding 2 mph to each shift (1-2,2-3,3-4). I noticed no change, WTF?

I tried 3 times and noticed no change. Truck was also running 13.3's.
Boost was 17 lbs. I tried the 2.5 inch pulley, got 20lbs again but I had also removed 4 degrees of timing for engine safety. Ran a 13.41. If there was more time I could have tried to add timing back in, might have ran quicker.

I only got 4 runs in, place was packed.

Trans tuning did not go as planned, but at least I know how boost is dropping during weather changes from winter to summer, and that the 2.5 brings it back to 20lbs of boost. Hope to get some more track time soon.

 

[4pointslow]

Maybe Friday will bring nice weather and I can go to the track.

 

[CDW6212R]

Tires and wheels



I have been looking at this site for a year now.
https://tiresize.com/chart/

I think I could go down to a 29. The problem I may have if I go any lower is running out of gear in 4th before the 1/4 mile is finished. Can not shift into 5th at WOT, would destroy the transmission.

I really would like to see a second gen explorer with 275/60/17 size tires on it. Please get them and post pictures of them installed. They may just be what I was looking for. According to the tire size chart they are 30.1 inches. But would they rub bad enough to not want them on my lowered explorer sport? The other things is if they don't hook up then I need to get drag radials instead. Traction is king at the track, slipping tires cause slower times and inconsistent runs.
I also will not run wheel spacers, they are not safe for my application. So I need to get wheels with the right back spacing/offset.

To bring this back up, I've got my 275/60/17 spare out from under my Mercury. I can see how it fits my 98 truck in the next day or two. It's a 44mm offset OEM wheel as I recall, so the wheel isn't appropriate for a 2nd gen. I have 1/4" spacers available, which are 6.35mm each. I might be able to take a picture with two of those on, which would make the wheels just over 30mm offset. I doubt three would leave enough threads to attach a lugnut.

Anyway, you need to have four identical tires for the A4WD system. But also, do you have the stock front differential? If so, you likely have one tire in front spinning while the other one does nothing(road speed). It may be time to consider a limited slip diff. The Torsen has been unavailable for a long time, they've been planning a manufacturing run. I heard recently from them that they are working on them, the cases were off being heat treated. So there may be a Torsen available soon for the 2bd gen front diff. The last run were reported to cost near $500, so it's not cheap of course. More to think about.

 

[4pointslow]

Yea, I looked at that Torsen set up after I saw you mention it on another thread, it looks like a great design. Loved the videos on you tube that show how it works.
I would never feel safe running spacers of any kind. I may never find a tire and wheel combo to upgrade the ones I have now.
Glad to hear on my 2004 post that you are going to go with the Auto 4wd with that 331. I really like the system and how it launches with all 4 and then cuts the duty cycle back when the speeds get up there.

 

[CDW6212R]

I have the spacers I was using with the 18's that have a 35mm offset. I'll still use them for the time it takes to use up the 18" tires, and then scrap the wheels.

I mentioned the spacers to use just to show how the 275/60/17's fit on the 98 truck. It may be inboard a hair from whatever 17" wheel you might find for your truck. That 275mm width is about the limit for the front of our trucks, and it has to have just the right wheel offset to clear fully.

 

[4pointslow]

Got to the track yesterday, best time of 13.09.
Boost was topping out at 18-19 lbs max.
I think DA (density altitude) was around 30.14 at Atco Raceway last night.
I think the only race I won was because the other car had mechanical troubles. lol.

I am hoping to be back at the track on black Friday and get into the 12's again.

 

[vroomzoomboom]

I am hoping to be back at the track on black Friday and will be in the 12's again.

there, fixed it for you

 

[4pointslow]

LOL, we will see.

 

[4pointslow]

I need a new boost gauge.

 

[4pointslow]

So I picked up a highly modified GT500 supercharger off eBay.
I has been worked on by Stiegemeier porting (http://stiegemeier.com/).
It has been ported, a liquid cooled snout added(not hooked up yet), and best of all it has the custom snakebite overdrive gears in it.

My goal was to reach the same levels of boost I was hitting, but with a larger supercharger pulley or more belt wrap/friction area to eliminate belt slip.
I pinned the boost gauge past 20lbs with a 3.1 inch pulley, and dropped to a 3.2 inch pulley which had me hitting just at 20 lbs of boost.
The best time slip of the day (November 26th) was a 13.23 and it was with the 3.2 inch with less boost.
I would like to try bringing down the boost and advancing the timing to see if it would allow faster 1/4 mile times.
The VMP pulleys that are made for the Cobra using their 6 bolt hub, only go up to 3.3 inches.
I would like to go all the way up to the original Cobra size which was 3.65 inches but VMP doesn't have a pulley ring for that.
Maybe I can just get a stock one to try out, pain to remove though.

My thoughts are that if I can add more timing to get it around 28 degrees(total) at wot with less boost then it may be faster.
I am currently down to around 20 degrees total, with water methanol. 22 caused a little detonation with both pulleys.
I am thinking about getting camshafts to try out next, at least if the engine comes apart it probably wouldn't hurt the cams.
If I got cylinder heads and a piston broke at wot, I am sure the heads would become scrap metal.
Lets see what next year brings!

 

[jd4242]

Nice..how much or how well do those cooled snouts really work??seen them but never seen any data on it

 

[Dono]

20 lbs boost, stock motor and pump gas with only meth spray.

one word.......crazy.

I'm sure there are lots of people asking questions with you pulling 1/4 mile times like that.

 

[vroomzoomboom]

new blower eh? so......whatcha doing with the old one......hmmmm?