I've read a few different comments for other cars and there shift limits, but they were all manuals. How does it differ for an Auto.

I have a 90 IROC-Z 350TPI all stock cept for 8.5mm Superconductors and Cat-back exhaust into 4" pipes to 4" Flowmaster. I Took her to Los Angeles County Raceway and ran a best 14.785 @ 92mph on street tires. I was shifting 500 before redline, but I've never really known as far as using the stock auto-tranny, and having that shift lag what the best shift rpm was. thoughts?

 

Well you make pead HP at 4400rpm....Try shifting at around 4600-4800rpm.
Experiment, see what makes the best time.

 

5400

 

After 4400rpm he is losing power....Why would you recomend 1000rpm after peak hp?

 

Maybe the extra time he loses not making power past that point is made up by falling into the next gear at a much higher point in the power band.

 

When my car was stock I tried different shift patterns, my max hp came on at 4000rpm. Stock, when left in drive the auto trans would shift at 4500rpm at WOT. I tried shifting manually up untill 5200. Past 4400 there is a noticeable decline of power. Like I said, try different shift patterns untill you find the one that yeilds the best e.t. Use that pattern.

 

i picked up about 2 tenths by shifting at 4700rpms over the 4300rpm shift point with the auto doing it.

thats the only reason i would shift it. if the auto doesnt shift at atleast 4400-4500rpms by itself then manually do it at 4600rpms. should be happy with that.

remember 700r4 has 3.06 first gear and 1.6 second i think. thats alot of gear drop so try winding out first to 5000rpms and shift
hold 2nd till 4600rpms.

 

I do see what you are saying though Stu, and it makes sense. The autos are kinda slow-shifting. Untill you get a shift kit, use B&M "trick shift" fluid. It seems to firm up the shifting action slightly. I like it.

I did notice however that if I shifted at 5000rpm (that's 1000rpm over my max hp) That I would feel a bigger "jump" into the next gear. But the time it takes to spool up 500rpm may or may not be worth the extra "jump".

Experiment!

 

trick shift sucks get lucas or redline

 

Works for me. back at 'cha

 

Thanks guys. Ill definately try both and see which works better. I wasn't aware that the powerband for the trans was so low. we'll see if I can get better times between shifting lower vs the high shifts at about 5200rpms I was making.

 

heres a HUGE tip..

if you're using the stock tach, go into the redline.

why?


because the tach is totally inaccurate and reads low.

so while you THINK you're shifting at redline, you're realy short shifting that..


that ALONE made over 7 tenths of a diff for me.

 

are you sure mr dude?

most are only off by alittle. you better check first before you do go to redline. LOL thats a way off tach. mine idles at 600-700rpms when warmed up and i do about 55 mph when in third gear rolling at close to 2000rpms. I forget my exact numbers but i calculated it slightly off 200-300rpms. i think it was too low, so i go to shift at 4700-4800rpms. but it feels strong till 5000rpms so maybe....

 

positive. 99% of them are off... lol.

2 quicky ways to check it:

1. use a laptop and ALDL cable

2. use a aftermarket tach.


the third way is to note the RPMs and speed and do the math
but with the speedo inaccuracy, tire size diffs, cable diffs and/or mechanical->digital->mechanical changes, its just not accurate enough to tell if you're off.

 

next trips to the track will be with my 3.27 gears and firmer adjusted shift kit, so i will try shifting at different points. i probly will get 4 runs or so. i will try 4500rpms, 4700rpms, 5000rpms and maybe 5200rpms. whenever spring time comes, i will see how it goes and get some numbers. LOL

 

/nod

 

I dont know about you guys but my new 700R4 without a shift kit shifts at 6300 RPMs all by itself. I also have 3:42 gears ... mods are in sig.

 

I read that one of the mags(I don't remember)got its best results shifting the auto at 5400. I personally don't even shift my car. I have a transgo kit and it does just fine by its self. I shift and lose time or get about the same times, but thats just me.

 

totally check your factory tach.. i didnt relize how far mine was off unitil i got to the track and hooked up to data log with my friends pc and cable.. odds are your is to. as far your shifting, i woudl get a good torque convertor and leave it in drive. thats how i been abel to get teh most ET out fo my car.