Does anybody have the current TF and FC rev limiter specs?

[.]

I'm looking for RPM numbers and time when they're activated.

 

[qtermile14]

I'm looking for RPM numbers and time when they're activated.

I'd be interested to see that too!

 

[ironpony]

F/C was adjusted to 8100 as of the new england race. When the car hits the rev limit it starts to retard timing, I do not believe there is a set time.

 

[ironpony]

T/F is 7900, also it is not a rev limiter it is a timing retarder, reason being if they were to use a true rev limiter it would cut power to the ignition which in nitro classes would cause a mis fire and very large BOOM............

 

[.]

Since everyone calls it rev limiter I thought if I said timing controller nobody would know what the hell I was asking about. Do both of them activate at the same time into the run? I thought it used to be that TF also started pulling timing sooner than FC.

 

[ironpony]

my understanding is that they start to pull timing when the RPM is reached, I do not know of a set time........hopefully one of the more knowledgable will chime in

I think referring to T/F pulling timing sooner is because of the lower RPM

 

[.]

From what I remember from several years ago is that they ignored RPM until so many seconds into the run, then they started yanking timing at so many degrees per second. I thought it used to be like 2.8 and 3.0 seconds for TF and FC, respectively.

 

[Just Paul]

Yes the timing retard is on a delay like you said Brent.

 

[Just Paul]

FC was changed to 8100 after Topeka last year. TF is 7900 last I heard.

 

[ironpony]

At about 2.75 seconds into the run, if the MSD system senses the engine speed is too fast, then it starts pulling timing back.

MSD Keeping Eye on Top Fuel Speeds With New Power Grid System
found it Engine Labs article

 

[Pete]

When they instituted a rev limiter back in 2004-5, it was causing a lot of finishline boomers and downtime. So that's when, I believe, it was changed to a timing retard.

 

[none]

When they instituted a rev limiter back in 2004-5, it was causing a lot of finishline boomers and downtime. So that's when, I believe, it was changed to a timing retard.

It was always a retarder, never a traditional ignition scatter type limiter.

And I don't know the exact specs, I meant to ask this weekend and never got it done. But it is time vs. RPM and the TF cars get there sooner. Tony did a nice segment a couple of weeks ago where he overlaid an Antron run with a Hagan run showing the FC starting the retard sequence approximately 0.25 second later. in that time the FC speed surpasses the TF speed and carries the momentum to the finish line.

Alan

 

[.]

When they instituted a rev limiter back in 2004-5, it was causing a lot of finishline boomers and downtime. So that's when, I believe, it was changed to a timing retard.

That was because they yanked the timing out too quickly when it activated. They've changed the slope numerous times and that really helped.

 

[.]

From NHRA Indy tech dept

TF: activated 3 seconds after hitting 7900, pulls 20 degrees/sec
FC: activated 3 seconds after hitting 8100, pulls 20 degrees/sec

 

[T.Smith]

From NHRA Indy tech dept

TF: 7900 RPM, activated at 3 seconds, pulls 20 degrees/sec
FC: 8100 RPM, activated at 3 seconds, pulls 20 degrees/sec

Thanks...not sure why I have 8250rpms in my mind. It all starts running together after awhile.

 

[.]

Thanks...not sure why I have 8250rpms in my mind. It all starts running together after awhile.

It was 8250 so that's probably why. I didn't know they'd dropped it to 8100.

 

[mick]

another really great thread.
thanks everybody for info and input.
made a comment in 'acceleration' thread
about this. simply amazing math, engineering, and physics.