R33 Flat Lines Once It Hits Limiter?

[SkyHi_33]

You cant be serious dude?

The engine has a rev limiter, this limiter is there to protect it from blowing up, once you go PAST this limiter (which can happen in a stock car) the engine goes in to safety mode and cocks out for a moment losing all power.

Ideally you should never hold the engine on its limiter no matter how well its built, 95% of engines reach their peak power and torque before the redline anyways as stated above, which means going beyond this is not necessary, however the extra 1,000 or so rpm are there to set you up for the next gear and should be plenty of time to change up.

A skilled driver will have no problem with this no matter if youre dropping skids, doing burnouts or spinning out... a trained ear will know how hard the engine is going without looking at the revs and you should then know how to adjust your right foot accordingly.

All I can suggest is practice changing up/down within the engines limits (and inside the power band) and soon enough things will just click.

If you think otherwise then good luck with future engine repairs... hope that conrod doesnt shoot out between your ears.

[FineLine]

You cant be serious dude?

If you think otherwise then good luck with future engine repairs... hope that conrod doesnt shoot out between your ears.

Shouldnt be a problem, There's plenty of room for it.

[89CAL]

I think your mistake was using the word flatline..... imagine your revs in a graph.... its going to gradually go up to a point where ur limiter is then remain flat (if its a flatline)

I think what your talking about is ur car hitting a safety or limp mode at redline which is causing the car to die. Get an ECU, or start changing to second.... even a standard skyline can handle second gear burnouts.

Dont blame the people on here for being smartasses if your going to give a vague description then call everyone a loser for not giving you the response you wanted

Edited July 20, 2009 by 89CAL

[Strik3r]

hes probably putting cheap fuel in and its pinging its ass off when he gets up it causing it to go into r&r

[mr-r33]

hes probably putting cheap fuel in and its pinging its ass off when he gets up it causing it to go into r&r

to be honest i use that 98 octane fuel and nothing less .....and yes for some reason it pops its ass off come done the gears but i think that is timing

[Damit]

and yeah that about sums up this thread

[DaGr81]

Man everyone is so harsh...

Maybe his missus is after the "pop pop pop ...flame goes here... Pop pop"

get a flame thrower it'll fix that right up.

On a side note

max torque at something like 5500rpm so change at 6k or so. Either way I don't see a point in going past 5k unless ur at the strip, even a skid pan you don't need to go that far...

[mad082]

wow, so many people not understanding what he means and just being tools for no reason, which also makes them look like tools.

anywho, to actually post on topic, it sounds like you have a problem. it sounds your ecu is going into limp mode, or the soft cut limiter isn't holding the revs low enough so it is going to a hard cut. the skyline rev limiter should just let it sit there and pop away until the engine blows. as someone said above, the SSS pulsar have a harder cut limiter where once you hit it it won't just sit there and pop away, it cuts out completely and lets the revs drop again by about 500rpm and then it comes back to life and will rev out again.

now you can choose to try this or not (at your own risk), but go for a drive and rev it up and hit the limiter until it cuts out. however don't change gears. just hold your foot on the acclerator and see how far the revs drop before it kicks back in. if it is only about 500rpm then kicks back in and repeats the process i wouldn't be too worried. if it drops well back down the rev range then there is something going on. you could listen to these idiots and just not rev it out so far, but that ignores the fact that there may be an underlying issue.

also you could open the up the ecu and see if has been remapped (will have a chip installed if it has), because if it has then it may have had the rev limiter settings altered and is the reason you are getting a hard cut. that would probably be worth doing before testing out the limiter again. if you are unsure of what to look for, open the ecu up and send me a pic.

[mad082]

Man everyone is so harsh...

Maybe his missus is after the "pop pop pop ...flame goes here... Pop pop"

get a flame thrower it'll fix that right up.

On a side note

max torque at something like 5500rpm so change at 6k or so. Either way I don't see a point in going past 5k unless ur at the strip, even a skid pan you don't need to go that far...

max torque is actually under 5000rpm, however it is usually a pretty straight line, so the torque you are making both before and after max torque won't be much less than max. also the higher you rev out, when you change gears the higher in the rev range you will be in the next gear, so the more power you are making. but as you said, unless you are on a track or drag strip, reving up to redline is pointless. it's just shortening engine/turbo life

[Birds]

If he has a GTS-T and hasn't done the solenoid mod then max torque will occur above 5000rpm at the second stage of boost.

Problem with shifting at high RPM is...the higher you shift, the faster and more efficient your clutch/throttle coordination needs to be in order to keep everything running smooth (smooth is fast), so it doesn't always make for the best shifts. Ideally you want to drop into the next gear at or just above maximum torque, which is always before the most conservative redlines.

The only time I would ever carry a gear to redline is to either hear the engine sound revving that high or when timing a 0-100km/h dash where a change to 3rd will be detrimental to the time.

[mad082]

max torque as quoted by nissan is at 4800rpm. obviously that is without the high boost mod, so adding the boost mod would possibly lower it a bit. changing just after max torque is not the most ideal place to change gears. for example, here is the torque and power chart of a porsche gt3

max torque is at 300ft lbs 5500rpm, and at 5500rpm it is making about 310hp. however if you rev it out for another 2000rpm you will be making 10 or 15ft lbs less torque but making an extra 100hp. the other thing to take into consideration, which i also said above and is extremely easy to show with that graph, is that if you were to do it your way and change gears just above max torque (lets say 6000rpm) and you drop 1500rpm on the gear change (on lower gears you will drop more rpm) you are going to end up down to around 266ft lbs and 218hp, a drop of around 35ft lbs. however if you rev out to max power, you will be making 415hp, your torque will have dropped to a bit over 280ft lbs, but you would have spent nearly 1500rpm longer at close to 300ft lbs, and then when you change gears you will be dropping into the rev range around the point where it makes peak torque and where it is making about 80hp more than changing just after peak torque. then there is the fact that you are also using that extra power in a shorter ratio gear, which then amplifies the power as well.

if it was best to change just after peak torque, then ever race driver in the country, in fact the world, is doing it wrong. i'd like to see you try and tell all the engineers of the F1 teams that they should be getting the drivers to change gears earlier to go faster.

[mr-r33]

here is a pic of my ECU...but i think it is just a stock one

[Birds]

Sorry, I re-read my sentence and it does sound a bit confusing on second reading. What I meant by "ideally you want to drop into the next gear at or just above maximum torque", is that you want the next gear to be at or above maximum torque once you have selected it, not perform the gear change at or above maximum torque.

[mad082]

ah, yes i see what you mean. however that doesn't work for every gear. in the case of the skyline, with max torque being at 4800rpm, when you change from first to second, even changing at redline you will end up a bit before max torque.

some cars will also have their torque at a range where even a decent rev out will mean the next gear is past its peak torque. the 190kw falcon motors are a good example. their peak torque is at only 2500rpm, yet max power is at 5250rpm. and you have to remember that power is a byproduct of torque and speed. that is why small motors with small amount of torque are able to make bigger power when they rev their tits off. for example a f1 car puts out about as much torque as a stock skyline, but a lot more power, because it revs much harder. it is also why a tractor or truck puts out massive torque but not much power. because it revs very low. so if you have a motor making max power a long way after making max torque, it is going to have a relatively flat torque, or if torque has dropped off a lot then you will end up with a relatively flat power curve. dyno's actually measure torque then calculate the power from that.

but ideally you want to change at around max power. the reason being that while you might be past peak torque, especially with smaller motors, your power is what is making you accelerate, which indirectly is your torque, but you will be accelerating quicker the closer you get to your max power.

[mad082]

here is a pic of my ECU...but i think it is just a stock one

yeah it is stock. it hasn't been chipped at all. if it had you wouldn't be able to see the white line around the larger chip in the upper right hand corner

[mr-r33]

If he has a GTS-T and hasn't done the solenoid mod then max torque will occur above 5000rpm at the second stage of boost.

Problem with shifting at high RPM is...the higher you shift, the faster and more efficient your clutch/throttle coordination needs to be in order to keep everything running smooth (smooth is fast), so it doesn't always make for the best shifts. Ideally you want to drop into the next gear at or just above maximum torque, which is always before the most conservative redlines.

The only time I would ever carry a gear to redline is to either hear the engine sound revving that high or when timing a 0-100km/h dash where a change to 3rd will be detrimental to the time.

boost is set to 10psi

[Birds]

ah, yes i see what you mean. however that doesn't work for every gear. in the case of the skyline, with max torque being at 4800rpm, when you change from first to second, even changing at redline you will end up a bit before max torque.

some cars will also have their torque at a range where even a decent rev out will mean the next gear is past its peak torque. the 190kw falcon motors are a good example. their peak torque is at only 2500rpm, yet max power is at 5250rpm. and you have to remember that power is a byproduct of torque and speed. that is why small motors with small amount of torque are able to make bigger power when they rev their tits off. for example a f1 car puts out about as much torque as a stock skyline, but a lot more power, because it revs much harder. it is also why a tractor or truck puts out massive torque but not much power. because it revs very low. so if you have a motor making max power a long way after making max torque, it is going to have a relatively flat torque, or if torque has dropped off a lot then you will end up with a relatively flat power curve. dyno's actually measure torque then calculate the power from that.

but ideally you want to change at around max power. the reason being that while you might be past peak torque, especially with smaller motors, your power is what is making you accelerate, which indirectly is your torque, but you will be accelerating quicker the closer you get to your max power.

I agree with the first two paragraphs, but given power is just a product of torque at a given/specific RPM...not a range of RPM...I don't think you'll be accelerating quicker the closer you get to your max power. Once torque starts to drop off, power continues to climb but at a slower rate (and consequently slower acceleration due to torque dropping off). Sport motorbike engines are the best at demonstrating this, as they rev far above their torque bands. After the torque band drops off significantly, acceleration turns to shit...the engine is still developing slightly more power...yet it feels like you've hit a brick wall in terms of acceleration.

That said, as you say, changing at redline in a Skyline renders you slightly below max torque in the next gear...so we don't have to worry about it in our cars.

[mad082]

I agree with the first two paragraphs, but given power is just a product of torque at a given/specific RPM...not a range of RPM...I don't think you'll be accelerating quicker the closer you get to your max power. Once torque starts to drop off, power continues to climb but at a slower rate (and consequently slower acceleration due to torque dropping off). Sport motorbike engines are the best at demonstrating this, as they rev far above their torque bands. After the torque band drops off significantly, acceleration turns to shit...the engine is still developing slightly more power...yet it feels like you've hit a brick wall in terms of acceleration.

That said, as you say, changing at redline in a Skyline renders you slightly below max torque in the next gear...so we don't have to worry about it in our cars.

yet they all rev out to redline in races before changing gears. maybe you should go have a chat to casey stoner and give him a bit of advice to help him win the moto GP. you are still going on with your same point you made earlier. it seems you still think that revving out past max torque is pointless. also if torque drops off too dramatically you will find that power also flattens off.

you also might want to rethink what you said about the sports bikes. take the r6 for example. it's max torque is made at 10,000rpm, and max power at around 14,500rpm, yet redline isn't until over 16,000rpm, and when you change gears at redline you will only be dropping down to around 14,500rpm. and i can garantee that anyone who races bikes will be reving them out to redline and not changing down around 12,000rpm in order to be at max torque when they open the throttle again. i know that on my dirt bikes i sure as hell reved them all the way out before changing when racing. and if you watch any videos on youtube you will see that they accelerate just fine even though they are 5000rpm above max torque

[Birds]

Racing bikes and F1 cars are very different cases compared to road going vehicles, it's a pointless comparison. They are tuned with torque curves that place big emphasis on top end, hence modifications such as multiple throttle bodies and camshaft profiles that benefit high RPM yet are useless in the low range. The specifications of these engines maintain a good distribution of torque all the way to their redline. So no, I don't argue with Casey Stoner wanting to change gears at redline...that is what his bike is designed to do and I'm willing to bet his bike doesn't see much below 10,000rpm around the track. Road vehicles on the other hand are tuned for daily drivability and fuel economy...they are given much more emphasis on low and mid range. Consequently, torque at the top end suffers and during a drag race it is pointless taking the engine to the point where it is no longer making power at the significant rate it once was. Yes it will accelerate fine, but the acceleration is not as fast as it was during the torque band. As I said earlier, it is a moot point for our cars though, because according to you our peak torque comes in around 4800rpm where redline and a gearchange will leave us at about peak torque in the next gear.

If you do several 0-100 or quartermile runs on a road going bike you will see - your best times will come from efficient shifts and smooth power delivery in the peak torque areas as opposed to maximum power or redlines. It is all about the torque and how long the engine can sustain it for. Power is only an indicator, it's not the thing that is pushing your vehicle.

[simpletool]

Shhhh......

Not too sure on the various relative pressures on the intake side when cutout occurs but it sounds like you are revving it too hard anyway.

Sounds suspiciously to me that the problem might be due to an after market BOV that is causing the engine to give the sensation of "dying" when it hit cut-out. This cutout should not make the car die completely until the next gear. I came to this BOV conclusion since you said it also pops on overrun - so do you have an after market blow-off valve? If so put a stock one on - it will make the car much nicer to drive in many subtle ways - trust me/us.

As for the shift point question - it's all about maximizing the amount of work or energy put into moving the car from the engine. This energy is proportional to the area under the POWER curve and is influenced by the RATE of increase of torque before the powerband compared to the RATE of decrease after the powerband. The best shift point (for racing) is determined by shifting at a point where the revs for the next gear will fall to a rev that maximizes the area under the power curve before the next shift point. This is slightly different for each gear as the rev range is compressed as you move up the gears - at least on a road car.

For street use I would say shifting around 5500rpm is a nice balance - I would use 6200rpm on a track and maybe 6800 if you want to overtake someone. Avoid rev limiter - unless driving a V-TEC or 4AGE - they love it

Edited July 22, 2009 by simpletool