quote:

Originally posted by Lenny5160:
Of course this could vary depending on where you set your shift time, but I always figured that if you are shifting on time and the weather got worse, when the car shifts at the same time you are now at a lower RPM and making that run even slower than it had to be.

If the weather improves, now the RPM is higher at a given time on track and so the run got quicker both because of the weather and the shift point.

Seems like it would make the swings wider unless the baseline shift point was a little higher than optimal, RPM-wise.

If the car is shifting on time near the ideal RPM going higher RPM with better weather may do the opposite. Going past ideal shift point will likely slow the car not gain. Time is easy to control, and can be used to slow the car if need be by shifting early.

quote:

Originally posted by adv ET 266:
https://www.summitracing.com/parts/sum-830453

JUNK!

quote:

Originally posted by jmarkaudio:

quote:

Originally posted by Lenny5160:
Of course this could vary depending on where you set your shift time, but I always figured that if you are shifting on time and the weather got worse, when the car shifts at the same time you are now at a lower RPM and making that run even slower than it had to be.

If the weather improves, now the RPM is higher at a given time on track and so the run got quicker both because of the weather and the shift point.

Seems like it would make the swings wider unless the baseline shift point was a little higher than optimal, RPM-wise.

If the car is shifting on time near the ideal RPM going higher RPM with better weather may do the opposite. Going past ideal shift point will likely slow the car not gain. Time is easy to control, and can be used to slow the car if need be by shifting early.

Yes, that’s why I added the caveat to the beginning of my post. I’ve never shifted on time and don’t have a data logger anyway, so I don’t have a feel for how much the shift RPM would tend to vary over a day, weekend, or season when shifting at the same time after transbrake release.

Even doing a decent amount of throttle stop racing, I prefer RPM.

quote:

Originally posted by B KING:

quote:

Originally posted by adv ET 266:
https://www.summitracing.com/parts/sum-830453

JUNK!

^^^^^^^ X2.... Chinese Junk ……

Once I get the Lamplighter on track, I will have valid data provided by Racepac. I will experiment with both methods and relay the results.

Using Grid, I’ve had mine shifting on both Time and RPM together many times experimenting with the results. I’d set them up to initially activate at the same time and then review the results at the end of the day. Switch them around one leading the other.

The last 5 years I’ve had the RPM leading the Time by 0.10 – 0.20 and use it to catch a missed shift if I wopped early just prior to the RPM shift that came almost 5 seconds after launch.

I’ve recently switched gearing that moved the shift to 3 seconds after launch and am only using the RPM output to shift with.

Having the ability to use either RPM or Time to shift with is a nice option.

My old Horton is still around and still has that $50 ultra reliable rpm switch from Summit Racing. Ohh all your TV’s, Computers are made in China. Toss them in the garbage now. Don’t be a hypocrite

quote:

Originally posted by adv ET 266:
My old Horton is still around and still has that $50 ultra reliable rpm switch from Summit Racing. Ohh all your TV’s, Computers are made in China. Toss them in the garbage now. Don’t be a hypocrite

I just recycled an 8 yr old Vizio TV for failed audio that sat in a spare bedroom for company and probably didn’t have 100 hrs of actual viewing time.

I assembled this desktop that I’m presently using 6 yrs ago and the Asus MB failed less than 1 month after the build and was replaced under warranty.

I agree ones choice of country to purchase from is limited in electronics. Unlike the device link you posted, I believe the higher quality programmable RPM activated switches are not made in China.

Perhaps you could share with us the logged repeatable RPM activation accuracy of this product. Thought you were using MSD 7530T ignition for this task……..

I was just sharing a lower cost option, not having a clue what the OP’s budget was. My M&M used the MSD Digital 7 and or the Digital Delay box for the 1-2 shift. I had used that Summit house brand switch in 1999 with an analog MSD 7AL. Worked well for over a decade.

quote:

Originally posted by adv ET 266:
My old Horton is still around and still has that $50 ultra reliable rpm switch from Summit Racing. Ohh all your TV’s, Computers are made in China. Toss them in the garbage now. Don’t be a hypocrite

I like to keep it simple and would not have a problem with that Summit switch. Nothing wrong with those others if you want to use them. Sure they will work fine to.

It appears Bender got the recommendations he was looking for. Mark W. took the thread in a different and interesting direction, and it is really something that is worthy of it's own discussion, (Shifting on Time vs RPM - Although it may have been discussed on here before). Steve, Tony, Larry & others then brought up some good and interesting points on that topic for consideration. I will look forward to any data that Larry or others can share on comparison testing/data using both methods. About 10-15 or so years ago, Luke Bogacki used to publish an occasional article on his Big $$ bracket racing exploits. He usually included some tech tips, and one of them was to shift on time, rather than RPM. His logic was similar to what Steve said, IIRC his thought was if you spun early in a run, you already slowed, and that an earlier shift in the run would result, (based on the spike in RPM due to slippage), which would cause a further slowing because the fallback RPM would be lower. So he proposed that shifting on time would assume the tires would haze then regain grip, the car would still have been accelerating, (though not at the planned rate), and the time-based shift would not hurt your run as badly. But as some pointed out above, the effect of all this depends on a lot of variables, like shift point relative to power curve, etc. This subject could get deep, and be a fun bench racing topic. Like many factors in our sport, if done the right way could pull a W out of an L, (or you could over-think things and find another way to turn a Win light into a yellow slip).

Did a search & came up with this somewhat old thread mine.

Anyway, I'm shifting on time because that's what I had from the throttle stop days. I'm noticing some shift rpm differences in the data logs. They're usually 20-60 rpm difference during the race & I have noticed occasionally a difference of 70-100 rpm difference. It appears the bigger rpm difference happens when the event has longer periods of time between rounds; like 3-4 hours, I would assume the weather change is playing a factor.

What are you guys seeing in shift rpm differences when shifting on rpm on your data logs?

2BKING

If you track transmission pressure like I do you can see the pressure drop right on the RPM set point, it takes my trans anywhere from 75-125 RPM to actually complete the shift. This is the time it takes to release the band and apply the high clutches. In my experience the faster the car is accelerating the longer it takes to complete the shift. My TD took 200 rpm or more to complete the shift from activation.

My shift rpm is set to 6925 rpm and is accurate to +/- 4 rpm at worst. In the photo the RPM is the maximum rpm achieved after shift activated. The TIME is the time period from launch to maximum RPM. TT is the Trans Temp at shift max rpm. These 6 runs are over 8 hours time period.

I have my shift timer set at 3.00, I have a peak rpm reading around 7,000 rpm with the variances I listed in my last post. It's over or under, but mainly under.

I know you use time & rpm. With my data, looks like I need to do something different. Like using rpm, what do you all think?

This is what I'm looking at:

https://proshop.summitracing.com/parts/sbr-ddi-1067

2BKING

What are you using for ECU ignition trigger?? Crank or distributor trigger?? Won’t Holley (what ecu?) output a programmable rpm signal to shift with?

I only use rpm (MSD Grid) to shift with as it’s the most accurate in my ignition set-up.

quote:

Originally posted by markemark:
What are you using for ECU ignition trigger?? Crank or distributor trigger?? Won’t Holley (what ecu?) output a programmable rpm signal to shift with?

I only use rpm (MSD Grid) to shift with as it’s the most accurate in my ignition set-up.

Using a Holley Hall Effect distributor. Using a Holley Terminator X ECU, pretty sure no programmable rpm signal (have to check). The Terminator X Max probably has that capability.

2BKING

Dear G*d. How am I supposed to keep all this stuff straight as I am hitting the shifter? Take care. Tom Worthington