Rev Limiter Question

[BAKnBLK2010]

He's using the 19" tires in his example.

The 19's are 27" tall also so it doesn't make a difference.

 

[stang910]

The 19's are 27" tall also so it doesn't make a difference.

He isn't running factory wheels and tires on his car. I believe his tires come out to 26". Sorry for the confusion.

 

[GrnBullitt08]

I just bought a SCT programmer and CAI from American Muscle. On the race tune 93, I noticed the rev limiter is set to 7,600 rpm.

This seems high to me. Probably because I'm just not used to the high revs. I shifted at 7,300 and the car was still pulling hard. Totally woke the car up. Unbelievable.

What RPM will these motors go to safely? I'm thinking of kicking it down to 7,200.

Beefcake had detonation @ 7500.....

 

[05yellowgt]

Beefcake had detonation @ 7500.....

But he also had a blower that caused the detonation. 7500rpm n/a seems to be ok, at least thus far.

 

[GrnBullitt08]

But he also had a blower that caused the detonation. 7500rpm n/a seems to be ok, at least thus far.

Yeah, 7500 is safe rpm from what I've been reading....from what I have picked up in this thread there are a few that are running 8000+

 

[DennyMcLain]

He's using the 19" tires in his example.

That's absolutely correct. The Brembo brake package and P255/40R19 tire. Didn't bother to look up the exact diameter but my program puts it as 27.03 tire diameter. Really doesn't matter if it's off a bit this way or a bit that way as the shift points remain the same.

 

[DennyMcLain]

Yeah, 7500 is safe rpm from what I've been reading....from what I have picked up in this thread there are a few that are running 8000+

Need a tiny but of help.

In the process of selling a 370z and on the fence regarding getting a Boss or doing my own thing on a regular 5.0. The factory rev limit on the Boss is 7500 rpm and the promo's I've seem list forged rods. Are the bottom ends the same? If so, it's kinda a no brainer for me.

 

[Wish I Had a Nice Car]

That's absolutely correct. The Brembo brake package and P255/40R19 tire. Didn't bother to look up the exact diameter but my program puts it as 27.03 tire diameter. Really doesn't matter if it's off a bit this way or a bit that way as the shift points remain the same.

im gonna have to try that next time i get out to the track. It just seems so weird to be shifting at different points each time. I figured you would shift at the same spot due to the power band being the same in each gear?

Sorry if its a dumb question, ive just never gotten into the specifics of where to shift when drag racing before.

 

[GeorgeInNePa]

Need a tiny but of help.

In the process of selling a 370z and on the fence regarding getting a Boss or doing my own thing on a regular 5.0. The factory rev limit on the Boss is 7500 rpm and the promo's I've seem list forged rods. Are the bottom ends the same? If so, it's kinda a no brainer for me.

The Boss has the same steel crank, but gets better rods and pistons.

 

[DennyMcLain]

Never such a thing as a "dumb question". Well, almost never. Somehow Chicken of the Sea comes to mind. Chicken or fish?

The reason the shift points change is due to the transmission ratio's in various gears. If the trans ratio's were spaced evenly so it dropped to the same rpm in the next gear, then you would shift at the exact same rpm every time. In this case they are not and as someone posted, you're looking at peak power for the next gear.

In the real world, not sure what a couple hundred of rpm's either way really makes. Of course there is always some human error factor in hitting shift points. In a car that made 480 N/A at the wheel adding a 125 hit of nitrous created a real pucker factor during the 1 to 2 shift. Kinda felt like it came up pretty quick for some reason.

im gonna have to try that next time i get out to the track. It just seems so weird to be shifting at different points each time. I figured you would shift at the same spot due to the power band being the same in each gear?

Sorry if its a dumb question, ive just never gotten into the specifics of where to shift when drag racing before.

 

[BlownAway05]

Lots of good info in here, like a few guys said before, you want to shift to give yourself the most hp throughout the run, can't just look at 1 gear independently.

 

[46foxcoupe]

i may be dumb....but my how are you getting to 122mph at 7200rpms in 4th gear? I trap at 115@7300ish with the 3.73s, which was the gear ratio used.

Keep in mind, that trap speed is not your speed at the end of the quarter. It's the average mph your car reached over the last 60' of the track. You're going faster at the end of the quarter.

My rev limiter is set at 7300. I run a 26" tall slick, my trap speed is 117. My car will barely tap the rev limiter when I cross the stripe in 4th.

 

[06MUSTANGGT24V]

Keep in mind, that trap speed is not your speed at the end of the quarter. It's the average mph your car reached over the last 60' of the track. You're going faster at the end of the quarter.

Do what? Have I been missing something this whole time?

 

[FlyByNight]

The Boss has the same steel crank, but gets better rods and pistons.

EDIT: My bad, looks like you're right.
Hi-Po 4V Ti-VCT V8 engine

The 440-horsepower* Hi-Po 302 4V Ti-VCT V8 engine features a "runner in the box" intake manifold and forged pistons, sodium valves, valve springs, new rods, oil cooler, and high-lift cams. This engine is capable of 7,500 rpm.
*Preliminary data. Premium fuel required.

 

[Falkinman]

If you guys havent used it yet, the two step feature works great too in the SCT tunes.

How does this work? I read about it once but can't seem to find it again. I think it uses the buttons on the steering wheel to set the launch rpm. How does it activate, brake or what? How does it turn off when you launch? Who does their tunes with this feature? Sounds really cool.

 

[Falkinman]

Anybody??

 

[BAKnBLK2010]

How does this work? I read about it once but can't seem to find it again. I think it uses the buttons on the steering wheel to set the launch rpm. How does it activate, brake or what? How does it turn off when you launch? Who does their tunes with this feature? Sounds really cool.

On the handheld SCT tuner you simply go into the tune you are going to download to your car and set the desired clutch in rpm you want. When you have the clutch pushed in the car won't rev past whatever rpm you input.

 

[Falkinman]

OK, that's slightly different than what I read. I wish I could find the thread. The way someone described it is that you used the buttons on the steering wheel to change the launch rpm and you could see what changes you were making using one of the digital readouts somewhere on the instrument panel. Has anyone seen this anywhere?

So BAKnBLK, with what you're talking about, how long would it take to make a launch rpm change between rounds at the track?

 

[Germeezy3]

Need a tiny but of help.

In the process of selling a 370z and on the fence regarding getting a Boss or doing my own thing on a regular 5.0. The factory rev limit on the Boss is 7500 rpm and the promo's I've seem list forged rods. Are the bottom ends the same? If so, it's kinda a no brainer for me.

The Boss rods are better but they are still forged using powder forging.

 

[GeorgeInNePa]

The Boss rods are better but they are still forged using powder forging.

I thought the info was changed to "forged", with no mention of powdered forged.