Safe rev limit
Discussion
Duke Thrust said:
Quick question chaps, what is the rev limit on a 3.0?
Also, is there a limiter? (If different from above, when does it cut in?)
Phil is correct about the shift point, IF you are still using the stock exhaust. The rev limit is actually 7200 (at least on cars in the US). If you get rid of the stock exhaust with its y-pipe restriction, and have it remapped, it should pull all the way to red line and your shift point can be at ~7000 with no problems. The problem with the stock exhaust is that the restriction causes a large loss of power over 6,000 rpm and that is why you are better off shifting then. Getting a true dual exhaust installed and getting it remapped really transforms the car into a monster in the way it performs compared to a stock setup.Also, is there a limiter? (If different from above, when does it cut in?)
While a great theory, the last 2 posts are technically inaccurate.
A remap will (should) allow you to take advantage of the capabilities of the motor and particularly the ancillaries Turbo Injectors, intercooler, fuelling quicker, with the liklihood that they'll hit their upper limits EARLIER in the RPM range, not later.
Phil, I see kinda what you were trying to say, but it came out wrong I guess?
Limiter is usually around 6700 - 6800 but there's little point. Better to change @ 6000 or slightly less. Same speed but much less temperature = more speed in the end.
Taking advantage of the powerband by carefully selecting change-up points based on known powerband is likely to increase (for example) track lap times while also being sympathetic to the engine, but "more speed" is a function of (being able to achieve) maximum rpm against gearing.
Mike
A remap will (should) allow you to take advantage of the capabilities of the motor and particularly the ancillaries Turbo Injectors, intercooler, fuelling quicker, with the liklihood that they'll hit their upper limits EARLIER in the RPM range, not later.
Phil, I see kinda what you were trying to say, but it came out wrong I guess?
Limiter is usually around 6700 - 6800 but there's little point. Better to change @ 6000 or slightly less. Same speed but much less temperature = more speed in the end.
Taking advantage of the powerband by carefully selecting change-up points based on known powerband is likely to increase (for example) track lap times while also being sympathetic to the engine, but "more speed" is a function of (being able to achieve) maximum rpm against gearing.
Mike
Assuming a standard car, if you rev to the limiter, the engine generates so much more heat than changing before 6000rpm, that the ECU knocks back the timing to the point that huge amounts of horsepower disappear.
Doing this on the track to improve laptimes was proved to a number of us by Lee Noble and the sales director at a couple of trackdays.
Obviously if you change bits this situation may not still be true, but for the majority of cases it is.
Doing this on the track to improve laptimes was proved to a number of us by Lee Noble and the sales director at a couple of trackdays.
Obviously if you change bits this situation may not still be true, but for the majority of cases it is.
ThatPhilBrettGuy said:
Assuming a standard car, if you rev to the limiter, the engine generates so much more heat than changing before 6000rpm, that the ECU knocks back the timing to the point that huge amounts of horsepower disappear.
Doing this on the track to improve laptimes was proved to a number of us by Lee Noble and the sales director at a couple of trackdays.
Obviously if you change bits this situation may not still be true, but for the majority of cases it is.
Phil,Doing this on the track to improve laptimes was proved to a number of us by Lee Noble and the sales director at a couple of trackdays.
Obviously if you change bits this situation may not still be true, but for the majority of cases it is.
That was because of the stock exhaust. It is a big limiting factor. The factory mapping had to take it into account too, because ti was like pushing on a rope above 6,000 rpm. Further R&D by Noble would have revealed this, but they were under time constraints and budget constraints, I'm sure.
The excess restriction of the stock exhaust causes the engine to work too hard. This creates more heat. In fact, where boost has been increased while still using the stock exhaust there is so much added pressure inside the cylinders that the stock valve springs have a difficult time opening the valves at high rpm. This is why some US cars have switched to beehive springs. Had they just installed a true dual exhaust, the beehive valvesprings would not have been necessary.
The restriction in the y-pipe of the stock exhaust was discovered very early on in the remapping research done at TurboHoses in the US and the ability of the 3.0 to operate with an expanded power curve all the way to redline after installing a true dual exhaust is a proven fact.
The other added benefit of replacing the exhaust is that you don't have to increase boost beyond 1 bar to get serious hp increases. The lower boost also means less heat. Some tuners will just increase boost to 1.4 bar to try to overcome the stock exhaust restriction to get the same hp results. This can be disastrous, because of the added cylinder pressure this places on the valvetrain. A really good tuner doesn't have to do that.
There is nothing inaccurate about this. It has been proven time and again here in the US. Get rid of the stock exhaust, install a true dual exhaust, remap it to 1.0 bar and your smile will widen exponentially.;)
caccobra said:
Phil,
That was because of the stock exhaust. It is a big limiting factor. The factory mapping had to take it into account too, because ti was like pushing on a rope above 6,000 rpm. Further R&D by Noble would have revealed this, but they were under time constraints and budget constraints, I'm sure.
Well, in the case of the UK Nobles, M12 3/R Etc. I don'r believe that to be the case, the smaller Turbo on the UK cars is well matched for up to a little over 400BHP. I think that was a "well specified" Turbo choice to run at the lower output the cars came out of the factory at.That was because of the stock exhaust. It is a big limiting factor. The factory mapping had to take it into account too, because ti was like pushing on a rope above 6,000 rpm. Further R&D by Noble would have revealed this, but they were under time constraints and budget constraints, I'm sure.
caccobra said:
The excess restriction of the stock exhaust causes the engine to work too hard. This creates more heat. In fact, where boost has been increased while still using the stock exhaust there is so much added pressure inside the cylinders that the stock valve springs have a difficult time opening the valves at high rpm. This is why some US cars have switched to beehive springs. Had they just installed a true dual exhaust, the beehive valvesprings would not have been necessary.
What back pressure was being seen at what boost levels and RPM when this theory was tested on a factory exhaust?The factory exhaust on my car hasn't proved restrictive so far and I'm at 427BHP. (running only 1 bar boost) so, to imply that it was "done wrong" at the factory simply isn't true.
I will add at this point though, that even at a cursory glance, there are obvious and dreadful flow areas and restrictions which could have been "designed out"?
These are not sufficient to cause major problems unless chasing some serious horsepower though, which would mean having to re-design the exhaust system anyway?
caccobra said:
The other added benefit of replacing the exhaust is that you don't have to increase boost beyond 1 bar to get serious hp increases. The lower boost also means less heat. Some tuners will just increase boost to 1.4 bar to try to overcome the stock exhaust restriction to get the same hp results. This can be disastrous, because of the added cylinder pressure this places on the valvetrain. A really good tuner doesn't have to do that.
"Added cylinder pressure on the valve train" 
I don't understand that?caccobra said:
There is nothing inaccurate about this. It has been proven time and again here in the US. Get rid of the stock exhaust, install a true dual exhaust, remap it to 1.0 bar and your smile will widen exponentially.;)
I don't actually disagree with that statement, suffice to say though, the same result can be done easily by leaving the stock exhaust on. I'm waiting to bolt 2 x hybrid Turbo's onto my car, (Once the R&D and testing on my custom Tilton clutch is complete), they will be good for circa 550BHP, I will be monitoring EGBP so that I can determine at what point the exhaust starts to hinder progress?Mike
ThatPhilBrettGuy said:
caccobra said:
...good stuff...
Yup completely with you. Maybe the question should really be what's the best rpm change for my car, then detail the car. For a standard car though it stands for the reasons you've said. Change at or before 6000rpm.The only time revving out past there is required would be on something like a top speed run where the additional RPM can affect top speed, (if there is sufficient power to push up to max RPM of course).
Mike
king hellMike Tuckwood said:
caccobra said:
There is nothing inaccurate about this. It has been proven time and again here in the US. Get rid of the stock exhaust, install a true dual exhaust, remap it to 1.0 bar and your smile will widen exponentially.;)
I don't actually disagree with that statement, suffice to say though, the same result can be done easily by leaving the stock exhaust on. I'm waiting to bolt 2 x hybrid Turbo's onto my car, (Once the R&D and testing on my custom Tilton clutch is complete), they will be good for circa 550BHP, I will be monitoring EGBP so that I can determine at what point the exhaust starts to hinder progress?Mike
Even after remapping, does your dyno plot still show power falling off rapidly over 6,000 rpm like the others I've seen posted here? If so, that is the stock exhaust restriction causing that. Compare that to some of the dyno plots on cars that have replaced the stock exhaust with a true dual exhaust before remapping and you won't see that kind of power loss anymore. Take a close look at the y-pipe and explain why you think that isn't restrictive at high rpm at full boost. If you still feel you can get the same tuning results with the stock exhaust as with a true dual exhaust, I have to think that you just haven't tried tuning a Noble with a proper exhaust on it yet.
Too bad you won't have a U.S. tuned car at your upcoming dyno meet for direct comparisons.
But in lieu of that, it may be worth reviewing this thread from last year on the subject of power tuning:
http://www.nobleforums.com/showthread.php?t=3253&a...
where it is clearly shown that the drastic power drop-off above 6k rpm that a stock car suffers from can be completely eliminated by upgrading components and doing some careful tuning. Any Noble owner will feel the differences immediately as an entirely new power range is unlocked without sacrificing motor durability or drivability.
But in lieu of that, it may be worth reviewing this thread from last year on the subject of power tuning:
http://www.nobleforums.com/showthread.php?t=3253&a...
where it is clearly shown that the drastic power drop-off above 6k rpm that a stock car suffers from can be completely eliminated by upgrading components and doing some careful tuning. Any Noble owner will feel the differences immediately as an entirely new power range is unlocked without sacrificing motor durability or drivability.
Mike Tuckwood said:
caccobra said:
The excess restriction of the stock exhaust causes the engine to work too hard. This creates more heat. In fact, where boost has been increased while still using the stock exhaust there is so much added pressure inside the cylinders that the stock valve springs have a difficult time opening the valves at high rpm. This is why some US cars have switched to beehive springs. Had they just installed a true dual exhaust, the beehive valvesprings would not have been necessary.
What back pressure was being seen at what boost levels and RPM when this theory was tested on a factory exhaust?The factory exhaust on my car hasn't proved restrictive so far and I'm at 427BHP. (running only 1 bar boost) so, to imply that it was "done wrong" at the factory simply isn't true.
I will add at this point though, that even at a cursory glance, there are obvious and dreadful flow areas and restrictions which could have been "designed out"?
These are not sufficient to cause major problems unless chasing some serious horsepower though, which would mean having to re-design the exhaust system anyway?
Mike
causing valve surge and consequently damaging the heads IIRC these were running at 1 bar to try to achieve the 425 quoted HP.
I believe the cause was the heads have poor flow charachteristics and needed to be fettled for more flow and/or fit stronger valve springs.
Mr Yellowshed may correct me here but I think I remeber correctly.
F.C.
caccobra said:
Mike,
Even after remapping, does your dyno plot still show power falling off rapidly over 6,000 rpm like the others I've seen posted here? If so, that is the stock exhaust restriction causing that.
Lets get one thing clear from the start, the 'Y' piece is a hideous piece of exhaust engineering, I know that as we do our own (well researched) exhaust design and fabrication here, I'm not denying that.Even after remapping, does your dyno plot still show power falling off rapidly over 6,000 rpm like the others I've seen posted here? If so, that is the stock exhaust restriction causing that.
HOWEVER, you can't blame it without actually testing what is ACTUALLY happening.
Oddly enough, the tail off in power accurately mimics the profile of the compressor map for the Turbo (on a UK car at least).
While the stock system is "far from optimal", it's also far more capable than is being implied.
I know what to look for within the data we assess while mapping and so far the exhaust hasn't ben any kind of limiting factor in terms of achieving power.
Mike.
F.C said:
Actually there were issues with the factory mapping on the M400.
Yes, I can believe that part easily. 
F.C said:
more than a few engines were replaced under warranty due to over boost throughout the map
causing valve surge and consequently damaging the heads IIRC these were running at 1 bar to try to achieve the 425 quoted HP.
I will be keeping a close eye on this, there are some relevant pointers and known issues that can cause head problems, I have a few suspicions but that doesn't place weak springs in the front of the firing line?causing valve surge and consequently damaging the heads IIRC these were running at 1 bar to try to achieve the 425 quoted HP.
head flow seems very good so far from what I've seen, issues like that are more usually down to set-up rather than component based? Always good to consider all angles though so I'm keeping an open mind.
Mike.
Adrian W said:
Mike Tuckwood said:
head flow seems very good so far from what I've seen, issues like that are more usually down to set-up rather than component based? Always good to consider all angles though so I'm keeping an open mind.
Mike.
have you seen the head on a flow bench mike?Mike.
Mike. LOL
Mike Tuckwood said:
Adrian W said:
Mike Tuckwood said:
head flow seems very good so far from what I've seen, issues like that are more usually down to set-up rather than component based? Always good to consider all angles though so I'm keeping an open mind.
Mike.
have you seen the head on a flow bench mike?Mike.
Mike. LOL
Again, have you seen a Duritec 3 litre head on a flow bench?
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