Thoughts on higher rev limit through tuning?

[KBBoss302]

I was just curious about what people thought regarding increasing the rev limiter on the Roadrunner engine. I have read a number of threads and articles that seem to imply that the motor is fully capable of withstanding 8k rpm or more. Anyone have any knowledge of engines going 'pop' from running higher revs? I know that some of tuners are running 8300rpm rev limits.

 

[svt1111]

My only thoughts are go for it and don't look back. These motors love to rev, and unless you plan on running a full race season spinning it at 8,300, you can expect plenty of longevity in a street car application.

I've revved mine a tad over 8,000 rpm only a couple of times, generally shift around 7,500 when driving aggressively. It is nice having the extra capacity and the sound at 8k is without many equals in a domestic car.

Try AED's tune.

 

[jbs$]

The RPM limits protect your engine and your pocketbook. If you pocketbook is deep enough, then don't worry about the engine.

 

[idhitit]

Unless its making power up there, there is no reason to rev it that high. Just wasting revs

 

[KBBoss302]

Thank you for the feedback, guys. I bump into the stock rev limiter pretty frequently so some added room up top would be nice. The more I read about these motors, the less concerned I am about running higher revs.

 

[12C/OBoss]

Set soft limiter at 7950 and hard at 8200 and dont look back!!!!!!!!!!!!!!!!



With JLT intake and catless x pipe the power over 7500 doesnt start dropping till 7800 or so and its REAL gradual...


and IT SOUNDS FREAKING SICK!!!!!!!!!!

 

[sprint200]

While the rotating assembly is "balanced" to 8500 RPM, the valve train goes unstable at around 7900 RPM (per one of the engineers who designed the valve train). But if you want to try it, it's a crap shoot. 9 times out of 10 you may get lucky. But that tenth time might bite you in the ass...........:cuss:oke:

 

[me32]

While the rotating assembly is "balanced" to 8500 RPM, the valve train goes unstable at around 7900 RPM (per one of the engineers who designed the valve train). But if you want to try it, it's a crap shoot. 9 times out of 10 you may get lucky. But that tenth time might bite you in the ass...........:cuss:oke:

so what part of the valve train gets unstable after 7900?

 

[nowwhat]

so what part of the valve train gets unstable after 7900?

what he said

 

[Rebel302]

He is getting that from this -

We should specify that for a valvetrain specialist such as John, Boss engine speeds do not end at the production car's 7,500 rpm. "We have a design guide so that if the fuel shut off is 7,500, we want the valvetrain to be stable to 400-rpm over that in case of over-speed events, missed shift on a downshift, or whatever. [This is to] make sure that if there is a momentary over-speed, the valvetrain doesn't come apart. If you throw a rocker arm or bend a valve--and it doesn't take long to do that under the wrong conditions--then you can lose your whole engine." Told that one of the Grand Am racers had managed to wing a RoadRunner to 9,000 rpm on a missed downshift with no apparent damage, Mark's commented, "I can only warranty it to 7,900, but I'm glad it worked!"

So, when Ford says redline is 7,500 rpm, their valvetrain engineers are really aiming closer to 8,000 rpm. John detailed the spring design process. "Because of higher lift, the lobe profile on the exhaust side, and the higher speed, we went to a stronger spring. To handle the stress from the higher speeds and the higher lift, we improved the grade of steel used in the spring, going to one with a higher tensile strength so we wouldn't have fatigue failure problems."

Read more: 2011 Ford Mustang 302 - Inside The Boss - 5.0 Mustang Magazine

 

[jaywoo]

Good article on the roadrunner engine and RPMs.

2011 Ford Mustang 302 - Inside The Boss - 5.0 Mustang Magazine

Hey! Ya beat me by 2 minutes!

 

[kbroush]

Unless you are doing a full all-out NA build I don't see the reasoning to raise the limiter except for safety from hitting the limiter, I've done this also.

 

[TXPD]

These motors love to rev, and unless you plan on running a full race season spinning it at 8,300, you can expect plenty of longevity in a street car application..

i guess i'd want to know what you would want to spin that expensive motor to 8300 rpm on the street?

 

[svt1111]

Set soft limiter at 7950 and hard at 8200 and dont look back!!!!!!!!!!!!!!!!



With JLT intake and catless x pipe the power over 7500 doesnt start dropping till 7800 or so and its REAL gradual...


and IT SOUNDS FREAKING SICK!!!!!!!!!!

i guess i'd want to know what you would want to spin that expensive motor to 8300 rpm on the street?

TXPD- what I was saying was you mitigate the chances of hurting the motor running on the street with an 8,300 rpm limiter. IE, its not as is you're running the high banks at Daytona for sustained 8k rpm's for hours at a time. That would push the motor into the outer limits if it's engineering spectrum, whereas having an 8,300 rpm limiter on the street allows you to play around and bang shifts at 7,800-8,000 rpm safely without hitting a limiter.

On track, personally, I'd keep rpm's below 7,500 during a session. No sense making a ton of heat spinning it to the moon for a DE event.

Drag racing is another animal altogether and these cars respond well shifting at 7,800-8,000 at the strip. Remember the motor is only in the 8k rpm range for maybe a second at a time.

 

[Rebel302]

Good article on the roadrunner engine and RPMs.

2011 Ford Mustang 302 - Inside The Boss - 5.0 Mustang Magazine

Hey! Ya beat me by 2 minutes!

:lol: ...:beer:

 

[Rebel302]

i guess i'd want to know what you would want to spin that expensive motor to 8300 rpm on the street?

Because the benchmark E92 M3 can do it oke: