more power above 8400 rpm?

Gents,

It's rare to SAFELY get to the upper band on the s65's power curve but today and a few times before I have the the chance. Maybe I'm nuts but I swear the engine isn't letting up at 8400 rpm. It feels like it's still building explosive power.. It's almost scary, time slows down a bit cause the crazy car seems to be going nuts at hyper RPM's. It feels like it's just getting warmed up.

I'm not planning to tank my engine to find out though. i've got all the bolt on mods on mine with tune so im aorund 455 hp I think.

Curious to your thoughts on this.

Thanks!

templarklimek wrote

Gents,

It's rare to SAFELY get to the upper band on the s65's power curve but today and a few times before I have the the chance. Maybe I'm nuts but I swear the engine isn't letting up at 8400 rpm. It feels like it's still building explosive power.. It's almost scary, time slows down a bit cause the crazy car seems to be going nuts at hyper RPM's. It feels like it's just getting warmed up.

I'm not planning to tank my engine to find out though. i've got all the bolt on mods on mine with tune so im aorund 455 hp I think.

Curious to your thoughts on this.

Thanks!

Thats exactly why I love this car so much. Once you get the RPM's up there it just keeps pulling and pulling. Though I dont have the sack to push it up past 8400. Ive redlined it two or three times (completely by accident) and became super parnoid that I was gonna blow my engine.
Ive owned a good amount of cars, and NONE have given me the rush that the S65 gives me above 8000 rpm. Its just sickening how amazing it sounds. Push your car hard, but be safe its a mighty expensive engive to replace if you kill it.

Very much agreed, but do you think it's still making power after redline? If so I wonder why no one has offered cam kits or the like to take advantage of it..

It's my understanding that 8300 is the max for hp for this motor. Raising the rev limiter to 8600 only increases the max speed in that gear, not necessarily the acceleration. FWIW hitting red line is not bad for a well-maintained S65, I wouldn't worry about it.

If you look at the HP and torques curves for the S65 you do see linear characteristics past 8000 RPM but a steep drop off after 8300. So this is why it feel strong all the way up to the limiter.

shendrick wrote

If you look at the HP and torques curves for the S65 you do see linear characteristics past 8000 RPM but a steep drop off after 8300. So this is why it feel strong all the way up to the limiter.

I think the drop is because the rev limiter kicks in. It would be nice to look at a dyno of a car tuned to have the rev limit increased.

Schrick makes cams for the S65, with them there might be some more power past 8400, but with stock cams power does indeed start dropping off after 8300.

There is a member on here with schrick cams in his car, maybe he could chime in with a dyno graph.

templarklimek wrote  

Gents,

It's rare to SAFELY get to the upper band on the s65's power curve but today and a few times before I have the the chance. Maybe I'm nuts but I swear the engine isn't letting up at 8400 rpm. It feels like it's still building explosive power.. It's almost scary, time slows down a bit cause the crazy car seems to be going nuts at hyper RPM's. It feels like it's just getting warmed up.

I'm not planning to tank my engine to find out though. i've got all the bolt on mods on mine with tune so im aorund 455 hp I think.

Curious to your thoughts on this.

Thanks!

455 hp? Wow what mods do you have to produce this much power? Did u dyno your car? I haven't seen any dynos of an NA S65 (except a stroker 4.6) above 400 whp on the dyno site. Thx.

Longboarder wrote

455 hp? Wow what mods do you have to produce this much power? Did u dyno your car? I haven't seen any dynos of an NA S65 (except a stroker 4.6) above 400 whp on the dyno site. Thx.

he never said whp. maybe flywheel hp?

Euro spec engines are around 420HP where US spec are at 414. Same engine, different tune. You're not hurting your US spec car by red lining.

templarklimek wrote

Gents,

It's rare to SAFELY get to the upper band on the s65's power curve but today and a few times before I have the the chance. Maybe I'm nuts but I swear the engine isn't letting up at 8400 rpm. It feels like it's still building explosive power.. It's almost scary, time slows down a bit cause the crazy car seems to be going nuts at hyper RPM's. It feels like it's just getting warmed up.

I'm not planning to tank my engine to find out though. i've got all the bolt on mods on mine with tune so im aorund 455 hp I think.

Curious to your thoughts on this.

Thanks!

Let's assume the engine is stock for a moment. Even with a completely stock power curve, your car would be faster and quicker if you removed the 8400 rpm cutoff and shifted it at somewhere around 9000 rpm or so. Of course it would eventually blow up if you were to do that a bunch, but isn't that a small price to pay for being a little quicker?*

The reason the car would be quicker is that, even though you're falling off the power curve at anything past 8300 rpm, you're still making a bunch more power than you would be if you were in second gear at that point, where you're making somewhere around 275 HP at around 5000 rpm after the 1-2 shift. And it's power that governs acceleration at any given instant. Yeah, we've gone 'round and 'round about torque at the drive wheels, but HP is the great shorthand in this regard, eliminating the need to do the torque-to-wheels calculations.

The reason the car feels as if it's accelerating even harder at 8000+ rpm (it isn't) is that the sturm and drang increases as the revs climb, and the sound during the last 12-1500 rpm in that car is a brassy, blaring, clarion call to battle that makes the driver feel as if it could go on forever. Combine that with a torque curve that falls very gently on its way from 3900 to 8400 rpm, and you have the rest of the picture.

With your modifications, the torque curve will tend to fall off even more gently, exacerbating that go-on-forever feeling, and raising the optimum shift point even higher, to, say, 9200 or even more.

Bruce

*Reminds me of when one of my sons was in U.S. Navy flight training back more than 20 years ago, and the instructor was warning the students during the pre-flight briefing that "I don't want any shit-hot maneuvers out there today, because that will get you a smoking hole in the ground".

Whereupon a wag in the class raised his hand, and said "But sir, isn't a smoking hole in the ground a small price to pay for a shit-hot maneuver?"

Yeah, you have to be a little crazy, I guess. My son is back at it after a stint in Afghanistan. Been doing it since '91.

bruce.augenstein@comcast. wrote

Let's assume the engine is stock for a moment. Even with a completely stock power curve, your car would be faster and quicker if you removed the 8400 rpm cutoff and shifted it at somewhere around 9000 rpm or so. Of course it would eventually blow up if you were to do that a bunch, but isn't that a small price to pay for being a little quicker?*

The reason the car would be quicker is that, even though you're falling off the power curve at anything past 8300 rpm, you're still making a bunch more power than you would be if you were in second gear at that point, where you're making somewhere around 275 HP at around 5000 rpm after the 1-2 shift. And it's power that governs acceleration at any given instant. Yeah, we've gone 'round and 'round about torque at the drive wheels, but HP is the great shorthand in this regard, eliminating the need to do the torque-to-wheels calculations.

The reason the car feels as if it's accelerating even harder at 8000+ rpm (it isn't) is that the sturm and drang increases as the revs climb, and the sound during the last 12-1500 rpm in that car is a brassy, blaring, clarion call to battle that makes the driver feel as if it could go on forever. Combine that with a torque curve that falls very gently on its way from 3900 to 8400 rpm, and you have the rest of the picture.

With your modifications, the torque curve will tend to fall off even more gently, exacerbating that go-on-forever feeling, and raising the optimum shift point even higher, to, say, 9200 or even more.

Bruce

*Reminds me of when one of my sons was in U.S. Navy flight training back more than 20 years ago, and the instructor was warning the students during the pre-flight briefing that "I don't want any shit-hot maneuvers out there today, because that will get you a smoking hole in the ground".

Whereupon a wag in the class raised his hand, and said "But sir, isn't a smoking hole in the ground a small price to pay for a shit-hot maneuver?"

Yeah, you have to be a little crazy, I guess. My son is back at it after a stint in Afghanistan. Been doing it since '91.

Well written explanation, thank you Bruce.

To answer the other question it's flywheel HP. intake/exhaust/pulleys/xpipe and tune.

jamze132 wrote

Euro spec engines are around 420HP where US spec are at 414. Same engine, different tune. You're not hurting your US spec car by red lining.

Euro and US car S65 engines make same power. There is no difference in tunes.

I am paraphrasing something I found on the intrawebz but it goes something like this

A scottish dude named Watt figured that a horse could do 746 watts of work.

Germans estimated that their horses could only do 736 watts of work and they called their measurement Pferdestaerke or PS (which they refer in their specs as BHP)

Conversion factor is approx 0.9866 BHP = 1 HP ergo the 420 BHP figure = 414 HP.

A Dinan tune raises rev-limit to 8600 rpm. If the power drops off at 8300 rpm, you'd never know it - things are moving fast as he** once you get above about 8 grand!

As far as my knowledge goes, each engine keeps piling up HP as it revs higher. It's the peak Tq. that drops after a certain point.

So let's say you tune a car to have a 7,000 RPM rev limiter and then to 9,000 RPM rev limiter. The peak HP with the 9,000 RPM will be higher, while most likely the peak Tq. figure will be the same.

Some cup cars basically have the same engine as the street version but with higher quality components while retaining the same displacement to be able to rev higher. While the torque figures between the street and the cup car are very similar the peak HP figures are much different due to a higher red line.

The rev limiter is there to prevent from shortening the engine life, hence the reason why cup cars need much more frequent rebuilding and have certain "operating hours" before a rebuild. The wear gets accelerated much more.

last night I just went out for a drive. Not to anywhere or for anything. I did a few high rpm pulls in 2nd gear, in tunnels and underpasses....gawd I love this engine.

It's my understanding that 8300 is the max for hp for this motor.

jamze132 wrote

Euro spec engines are around 420HP where US spec are at 414. Same engine, different tune. You're not hurting your US spec car by red lining.

I believe you are comparing the BHP figure to it's converted HP figure.

sin911 wrote

As far as my knowledge goes, each engine keeps piling up HP as it revs higher. It's the peak Tq. that drops after a certain point.

So let's say you tune a car to have a 7,000 RPM rev limiter and then to 9,000 RPM rev limiter. The peak HP with the 9,000 RPM will be higher, while most likely the peak Tq. figure will be the same.

Some cup cars basically have the same engine as the street version but with higher quality components while retaining the same displacement to be able to rev higher. While the torque figures between the street and the cup car are very similar the peak HP figures are much different due to a higher red line.

The rev limiter is there to prevent from shortening the engine life, hence the reason why cup cars need much more frequent rebuilding and have certain "operating hours" before a rebuild. The wear gets accelerated much more.

Power curves and rev limiters are two completely different things. The rev limiter is there for safety reasons only.

Reving higher is pointless unless you have the air flow capacity and valve action to fill the cylinders and empty them efficiently at that rpm. The power peak can be defined as a point after which engine torque is falling faster than rpm is rising. The higher the rpm at which you can make torque, the more power you will make, in a completely linear way. That is to say, if you can make 295 pound feet of torque at 3900 rpm, that's 219 HP, but if you can make 295 pound feet at 7800 rpm, that would be 438 HP.

The M3 V8 can't quite do that, but it's close. The torque curve only falls to about 262 pound feet at 8300 rpm. That's only about an 11% drop over a 4400 rpm span, which is absolutely terrific for a smog legal street motor.

Bruce

ThunderMoose wrote

Euro and US car S65 engines make same power. There is no difference in tunes.

I am paraphrasing something I found on the intrawebz but it goes something like this

A scottish dude named Watt figured that a horse could do 746 watts of work.

Germans estimated that their horses could only do 736 watts of work and they called their measurement Pferdestaerke or PS (which they refer in their specs as BHP)

Conversion factor is approx 0.9866 BHP = 1 HP ergo the 420 BHP figure = 414 HP.

Good explanation, but a slight error slipped:

BHP has nothing to do with the German standard. It can stand for either Brake Horsepower (bhp or SAE gross hp) which is power at the crank without accessoires, mufflers of filters; or Boiler Horsepower (BHP) which is an older American definition of power.

The German PS is usually referenced as DIN hp (Deutsches Institut für Normung) as opposed to SAE net hp.

So 420 DIN hp = 414 SAE net hp

CanAutM3 wrote

Good explanation, but a slight error slipped:

BHP has nothing to do with the German standard. It can stand for either Brake Horsepower (bhp or SAE gross hp) which is power at the crank without accessoires, mufflers of filters; or Boiler Horsepower (BHP) which is an older American definition of power.

The German PS is usually referenced as DIN hp (Deutsches Institut für Normung) as opposed to SAE net hp.

So 420 DIN hp = 414 SAE net hp

Thanks for the clarification. I knew that BHP stood for brake horse power and it was clearly intended to represent something different than hp since we all use 414 hp when describing the power that our cars make, while the M3 technical information references 420 BHP and 309 kW. I couldn't find the net to gross conversion, but I did come across the ps to hp calc which coincidentally matched the bhp to hp calc. Anyway, thanks for the information.

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