Shift RPM?

[Steve Wood]

respectfully.. .baloney! Man has always been limited by his lack of imagination   Some dare to lead, some deign to follow, and a few sit back and watch

[reality]

Well in this one thread you have covered BOTH ends of the spectrum so which is it. Reality or perception?


Imagination has no place in basic math.

[Steve Wood]

Makes sense to me.  Perception is often reality.  Depends upon one's vantage point.

[Tim Hensley]

Thanks for the time on this thread.My 5500 shift was just picked because it’s the number I felt good with,no scientific data.It took me two try’s to get the governor to shift at 5500.Thanks Steve for your input,I believe the transmission is ok.I didn’t talk to Lonnie at EX but the guy I did talk to said the new converter could make the shift go up.Im glad I took time to ask this question, I was about ready to pull the pan and work on the governor,but I’m convinced to raise my rev limiter. I may have been leaving power on the table by not  reving  it a little higher.
I was hopping some one would have had some Dyno numbers with a DLS cam.Some people talk that these make power down low and some rev them pretty hard i was shooting some were in the middle.
Lonnie and Edge said to lock it and I did a time our two but I didn’t see any reall improvement.
In Hawaii our speed limit is 55 and most of the time 45 so I don’t miss that anointing clutch locking and unlocking 40 times in 50 miles.

[Steve Wood]

Tim, I would be very surprised if my cam and your cam are somewhat similar in specs.  Dan Strego was at PTE when I got that cam from them and he was the engine guy-not Harry.  I'm guessing it has a bit more lift than mine as mine was apparently designed to clear stock guides, I suspect.  As we know, Dan was a very talented engine guy.  I know he built the engines for Tweaked 2 and I recall LC talking to him about the first Tweaked.

My cam has a very flat power curve starting off idle and continued all the way to 6200 when it would go POP!  The third gear rpm curve on PL never showed any change in the acceleration rate.  It was flat as a board in trend.  There was/is no "getting up on the curve" at some point and then falling off later.  Even in no boost, normal, driving, it has no weak spots.

The only problem I see is letting the engine go past the point where the valve train can no longer control the valves.  Hydraulic rollers have a significantly lower point for loss of control due to component weight than do solid rollers and much more than flat tappet lifters.

I picked 5800, not because it was at the end of the "power" curve, but because after shifts, the rpm curve showed no real change of of acceleration rate and it kept me away from the point where things would end with a bang.

I am particularly nervous about the tranny failing to shift as we spent a year with William Avila's car trying to get it to shift to third under wot conditions and three transmission experts said the tranny was okay.  He was having to shift manually to third (at least when he remembered that he had to shift) and performance was all over the place.

In your case, I would suggest setting the rev limiter to 6000 and see if that gives it enuf room to shift properly consistently.  I confess that I was confusing hitting the rev limiter with failing to shift.  And, yes, a looser converter can/will change the shift point a bit higher particularly if the car is making more power.

Ah, you mention converter lock up...I just changed my original Precision converter which had a very low stall that did not want to work with my T66 turbo to one that probably has about 700 more rpm of stall.  On the original, the lock up was a hard thud every time it locked up.  It did not matter if you were going 45 mph, or had touched the brake momentarily to unlock it at 75 and then it relocked...Ban g!  The worst case was when the car was in overdrive.  The new converter does not seem to lock nearly as hard.  I'm not sure what is up with that but I think it is the higher stall/more slip..but, so far, I'm not complaining!  LOL

I think Rich is correct on your car.  You need to launching between 10 and 15 psi.  I don't know what kind of tires you run at the track, but, you need sticky ones!

Hope you get it all sorted out and have some serious fun!  That sounds like an oxymoron...

[Steve Wood]

BTW, Tim, you are running a 28" tire in the rear, aren't you?  Besides suggesting to the engine you are running a taller gear and giving you more usable power band preventing you from needing a shift point into fourth gear, it gives you a longer foot print so you can launch harder.

[Scoobum]

PL logs from my own car show me having to flash the convertor to 3950 to get into the 1.5's. As a comparison, I followed Murphsters thread as he posted all the data he had from taking a stock turbo to its limit. He was flashing the convertor to about the same RPM to hit the 1.5's.

You'll need enuf RPM drop at he shift points to keep the engine in it's 'wheelhouse' instead of buzzing the engine past it's RPM limit of making HP.

A good convertor will give a slip percentage in the single digits.

In general, a looser convertor makes it easier to launch...but will give up some slip on the big end. If you can tune, you can run a tighter convertor and get it to flash at a higher RPM...and give nothing away on the top end charge.

My own car goes through the 1/8th mile traps at 5500 and the 1/4 at 5900.

[Forzfed]

PL logs from my own car show me having to flash the convertor to 3950 to get into the 1.5's. As a comparison, I followed Murphsters thread as he posted all the data he had from taking a stock turbo to its limit. He was flashing the convertor to about the same RPM to hit the 1.5's.

You'll need enuf RPM drop at he shift points to keep the engine in it's 'wheelhouse' instead of buzzing the engine past it's RPM limit of making HP.

Wasn't he using a higher stall converter?  Did I mention I pulled a 1.61 60ft with the stock converter?

[Scoobum]

What did the stock convertor 'flash' too...that's the data that's important. Most will hold it to a certtain PSI and launch. They have no idea what the convertor is doing.

You'd be surprised how low the stall is on my 16930...but with Scoob tuning low gear...he can get it to flash anywhere he wants.

Norbs ran a 2800 Precision LU multidisc with a 70 Ptrim and a large v band exhaust housing and went 1.51. Sounds like a match made in hell..but he got it to work via tuning and leaving at 20 PSI off the transbrake.

[Steve Wood]

It's really dangerous to compare various converters as they probably have different torque multiplication ratios...yeah, they act like a gear as well LOL

[Scoobum]

It's really dangerous to compare various converters as they probably have different torque multiplication ratios...yeah, they act like a gear as well LOL

Exactly why it's important to get out to the track and log what the convertor is doing.

[Steve Wood]

while remembering that it may act differently on another car that has more or less power coming out of the flexplate

I always remember the 9/11 that I bought.  It would flash to 4000 any time I hit the pedal, was slushy as heck in normal driving, and never showed a blip in the rpm curve when I locked it....I never saw less than 22% slip at wot on the top end...  I think it was a bad converter from day one.

Converters are extremely complex and when you get a good one, you know it.  I still maintain it is the most important part in the combination.  25 years ago, the AC converter was damn good, and today, it still is hard to beat.  It does not slip much in normal cruising.  Gas mileage is not hit very much and it is very streetable

Non lock ups are lighter weight and generally accelerate more quickly than a lock up

[Scoobum]

This AC 16930 I have sure works nice with the 6262 JB. It does it all.

[Steve Wood]

Yaklin's old car ran mid tens with that converter and a big turbo...stock cam

[Scoobum]

Yaklin's old car ran mid tens with that converter and a big turbo...stock cam

Joe ran bottom 10's for years with a 109 and a 19930. One of the locals went 9.68 with a 19930 and a 109.