Cannysage

iTrader: (29)

upping the rev limiter will shift the power curve, right? throttle body stays open longer? peak hp change? input please.

rcdash

iTrader: (18)

yes. yes. no.

peak hp will occur at the same point unless you've got cams or intake that allows power to continue to climb all the way to redline... In other words, in most of our cars, peak hp is not redline limited.

Cannysage

iTrader: (29)

when I said peak hp, I meant it sustains/occurs at a different rpm range. so if stock car is rated at 250hp peak @6000rpm, it can potentially shift to 6200rpm? (these numbers are just examples)

VitViper

iTrader: (1)

Not with just raising the rev limit.

bbs350z

iTrader: (85)

so if the rev limit is raised to 7200, power will still drop off when? 6700?

i understand to make power you must add cams, etc, but lets say the motor will rev to 7200, but stop making power at 6700 for example, the ap from 6700-7200 doesnt make power?

VitViper

iTrader: (1)

Raising the rev limiter does absolutely NOTHING for your power curve.

bbs350z

iTrader: (85)

so its pointless unless you get cams, etc and a decent tune?

Cannysage

iTrader: (29)

I think you make power all the way to 7200, so the power curve should alter.. no? (in stock form, without cams).

Beeker

iTrader: (5)

You make power but not peak horsepower. If you look at almost all dyno charts of a Z (287hp) you will see that peak horsepower is around 6200 rpms. After that power goes down until redline. Adding boltons can change the curve and the point where peak power is made but just raising the redline won't. If peak horsepower happens at 6200 rpms then it still will no matter what the redline is set at.

The main advantage to raising the rev limit is so you don't hit the fuel cutoff so early. If you have all the common boltons and have been tuned then odds are that peak hp may occur at slightly higher rpms. Let's say 6500. If you leave the rev limit at 6600 then you will be hitting the fuel cutoff too often. By raising the limit to 7100 you can over rev a bit without hitting the fuel cut off.

The other advantage to a higher redline is that when you shift the next gear will be higher in the power band. If you dyno the car you will be able to see where your car makes the most power through out the rpm curve. Once you know that you can decide at what rpm you should shift at to stay in the most powerful part of the power band.

page04Z

iTrader: (1)

Raising the rev limiter on a stock car will do nothing for the car (as stated 100 times already).

The only advantage I could see by revving higher, assuming you aren't losing a ton of power going to 7k or so, is the fact that you will shift into more power... So, revving higher really excels in cars with a 6spd like ours.

I know when I was building my subaru, I was aiming for the 2.0L JDM block that revved to 8k, toss a big turbo on that with the 6spd and you have a serious powerband.


Oh yeah, my suggestion is don't mess with it. No offense intended but if you didn't know the answer to what you asked, you should do more research and learn more about cars (and engine physics) before you go revving the engine higher than the factory redline.

oro

iTrader: (5)

I think that's why he is asking, to up his knowledge on the subject since we have so many knowledgeable members on this board and the many shops who also help out as well.

first350

iTrader: (24)

a few more hundred rpms is also nice for autoX...I raised my '05 to 7200 rpms - I can stay in 2nd gear rather shifting to 3rd or boucning off the rev limiter.

rcdash

iTrader: (18)

The main factor to look at is the wheel torque at any given moment. Remember that your gears are torque multipliers. The biggest advantage raising the rev-limiter provides is allowing you to stay in a much more powerful lower gear longer. In fact, if you could safely set the rev limit anywhere you wanted, it should be at the following point to maximize the area under your torque curve as you shift into the next higher gear:

Torque@Gear1Redline * Gear1_GearRatio = Torque@Gear2JustAfterShift * Gear2_GearRatio

In our cars, torque falls off after peak torque is reached around 4800 rpms, but slowly. Even though you are "losing power" compared to the peak hp point (where the rise in rpms no longer compensates for the loss in torque output), you are still better off shifting as late as possible to take advantage of the lower gear torque multiplier.

page04Z

iTrader: (1)

True, I'm not saying I cared that he made a post asking a question. I'm simply stating that I think he should learn more about cars in general before he starts messing with redline or any function in the ecu.

shift-er

iTrader: (2)

raising the rev limiter on a stock Z regardless of year is pointless due to the diminishing power curve.

If power seemed to climb all the way to redline only to be restricted by a limiter then bumping it up may uncover a further peak along the graph....however this is not the case with the VQ.

Raising the limiter to 7200 rpm will only increase your rev range throughout each gear and will have no direct effect on power.

bbs350z

iTrader: (85)

i know my fair share about cars, and modding, but theres always something new to learn. didnt you ask questions as you were learning? by answering no, that would tell me that you were born with it in your brain that seems to works so fantastical (pun intended). trying not to be a smartass, but asking questions is the key to learning. better to ask and know then to not ask and seek the answer, and make a faulty judgement because of it. how much do you know about the vq motor sir?

Z1 Performance

iTrader: (564)

it will drop off at exactly the same place as it does stock

upping the rev limiter does not change the power curve - the only thing that affects the power curve are breathing mods (intake, exhaust, cams, heads, etc etc) and ecu tuning

An otherwise stock car will not benefit from an increased redline - the benefits are, as posted already- a buit more time before fuel cutoff happens, and makes it easier to drive on an auto-x, etc. since you will return to the 'sweet spot' in the torque range more consistently.

SergEK

Avg horsepower goes up with the redline, as others have stated by shifting higher the torque multiplier of a lower gear allows for slightly better acceleration

I have a RevUp which peaks slightly higher than a non revup but with two mods I have seen my peak power plateau to redline....while torque is slowly falling off I am still making near peak hp to redline (not more) so for me increasing my redline another 5-600 rpm would help me with higher avg hp in my 2K rpm powerband up top

Most folks who raise the limiter will also buy breathing mods --- the best way to take advantage of a higher redline would be to make sure the A/F is optimized so your not running super lean on older Z's or pig rich like my 06 RevUp....I think the older Z's will need some wideband 02's and a UTEC, OSIRIS type setup to get a good tune up top and at least maintain power to redline

OSIRIS is about 600 or so and I think widebands are like 3-400 these days maybe less so its not cheap, but as I stated earlier who doesnt do breathing mods while getting a higher redline? Even a reflash is like 4-500....while they make a few ponies the real meat is after bolt-ons when the A/F gets crazy (lean) on older Z's (thus the need for a wideband for tuning/monitoring)

I will be upping my redline when I get my OSIRIS setup ....I am mostly looking to clean up the A/F while also upping the avg hp of the car with a 75-7600rpm redline....currently my peak hp happens at 6329 while torque begins dropping off at 4977 or so....my two mods just held onto more torque from 4000 to redline producing some nice hp gains up top....at $87 for the TB spacer and $110 for the popcharger I would say most VQ owners could benefit from a higher redline with my mods.....if they shell out 1000 or so for the OSIRIS w/WBs whats another $197 for breathing mods or even another $250 on top for a plennum spacer....

My two cents anyway.....

gothchick

iTrader: (12)

Pop Charger = heat soak.
TB Spacer = Does not produce hp. Only good for additional vacuum/ boost feeds.
Maybe you should re-read Adam's post (Z-1) above about the affects of raising red line on a relatively stock engine.

page04Z

iTrader: (1)

I'm a subaru boy, so I don't know much about the VQ motor but I can tell you everything about and in between the ej205 or ej257 subaru motors. And I know enough from reading that revving higher does not mean more power.

And I didn't tell anybody to not ask questions. I told the OP that if he doesn't know the answer to that question, then he should just leave his engine alone. I didn't call him a noob and tell him not to ask questions - I told him the exact opposite that he should research it more and learn how an engine actually works. Learn what something called Volumetric efficiency is called and why you make more power with better flow. What I'm saying is get familiar with what you are doing before you go doing it. Thats my ADVICE, thats also my advice to you. His post had no signs that he was actually planning to do this, but I was giving him my advice to not do it.

Also your statement had no pun.