Do higher RPM mean more power?

[triplep]

So I did a search, albeit it was not very long, so this might have been already answered. I am wondering if you were able to increase your red line, say from 6700rpm in my case to 8000 rpm, would you experience much more power at the top end?

(I am just looking for my next engine mod)

I was just looking at my dyno graph, and it seems as though above 6500 I start to drop off with power, which leads me to believe, even if I did get titanium springs etc, I would not see any noticeable power gains above 6500 and I would need more aggressive cams, or would I still see more power at above 6500, as the engine is starting to cut off fuel so that I don't go past the redline on my car?

[Twin_Cam_Turbo]

Probably dropping off at higher RPMs because it struggles to breathe.

[Darell_n]

Theoretically yes, more RPM = more power if you can maintain the amount of torque being produced. Typically this involves lighter and stronger valve train, ported heads / larger valves, larger and better designed intake and exhaust and a re-tune, higher overlap cam profile. Basically more air in and more air out. Many ignition and fuel systems are also limited to lower operating speeds. This will cost thousands of $$ or you can just buy a $200 nitrous kit off Kijij and go have fun.....

[pheoxs]

Originally posted by triplep
So I did a search, albeit it was not very long, so this might have been already answered. I am wondering if you were able to increase your red line, say from 6700rpm in my case to 8000 rpm, would you experience much more power at the top end?

(I am just looking for my next engine mod)

I was just looking at my dyno graph, and it seems as though above 6500 I start to drop off with power, which leads me to believe, even if I did get titanium springs etc, I would not see any noticeable power gains above 6500 and I would need more aggressive cams, or would I still see more power at above 6500, as the engine is starting to cut off fuel so that I don't go past the redline on my car?

Power is a by product of torque and RPM. If you can maintain torque and increase RPM = more power.

But if you look at your dyno and you're torque is dropping off too fast, then higher redline won't do shit.

Different cams and other mods though can shift the power band high/lower. Look at some of the street bikes, little torque but crazy high RPM. Likewise bigger V8s make huge torque but low RPMs.

[revelations]

OP youre correct that, if your dyno chart drops off rapidly, simply increasing the RPMs by itself wont make any more power.

[zieg]

Just something to consider..

HP = torque (in ft-lbs) X RPM / 5252

Which is also why the HP and TQ curves always cross at 5252 RPM..

[Toma]

Total airflow in a period of time is what creates power.

Each cylinder "sucks" a volume of air with each 2 engine revolutions.

The faster the engine rotates, the more of these suction events can occur in a given time.

So the faster you can turn your engine, the more air you can move, and hence more power you can make.

However, the faster you spin the engine the less time per suction event there is to completely fill the cylinder. If there is any restriction in the inlet tract, at some point in rpm, you will start to not fill the cylinder "completely". So even though rpm is rising, power will level off and then fall as the restirction results in less and less of a cylinder fill.

An engine that makes peak power at say 6500 rpm cannot be just cammed to make peak power at 8500. Cam typically "rocks" the power curve around a peak power rpm, but port flow and valve curtain area, and also diameter typically "fixes" the peak rpm point.

So, yes, you are right, to make big power NA, you have to have RPM. But to make power at RPM, you need parts that flow the air.

When we go "class" racing in the US, the V8 NA engines are turning 11,500rpm in some cases to be competitive. Even Derek's XDR turbo small block we run upto 9500.

[HO2S]

Originally posted by Toma
Total airflow in a period of time is what creates power.

Each cylinder "sucks" a volume of air with each 2 engine revolutions.

The faster the engine rotates, the more of these suction events can occur in a given time.

So the faster you can turn your engine, the more air you can move, and hence more power you can make.

However, the faster you spin the engine the less time per suction event there is to completely fill the cylinder. If there is any restriction in the inlet tract, at some point in rpm, you will start to not fill the cylinder "completely". So even though rpm is rising, power will level off and then fall as the restirction results in less and less of a cylinder fill.

An engine that makes peak power at say 6500 rpm cannot be just cammed to make peak power at 8500. Cam typically "rocks" the power curve around a peak power rpm, but port flow and valve curtain area, and also diameter typically "fixes" the peak rpm point.

So, yes, you are right, to make big power NA, you have to have RPM. But to make power at RPM, you need parts that flow the air.

When we go "class" racing in the US, the V8 NA engines are turning 11,500rpm in some cases to be competitive. Even Derek's XDR turbo small block we run upto 9500.

The air flow into a na cylinder should be 14.7 psi no matter the rpm. You will hit a rpm were the flame will chase the piston down the cylinder and not make any power. It should be around 6700 rpm. Same thing with forced induction. Their are more To power curves than the last 2000 rpm.

[rage2]

Originally posted by HO2S
The air flow into a na cylinder should be 14.7 psi no matter the rpm.

Not true, otherwise you'd have max torque everywhere. You're never drawing a full volume of air due to restrictions in the intake path from the air filter, to the airbox, to the throttle bodies, to the cams, valves etc. Even though you're drawing air at ambient air pressure (say 14.7psi @ sea level), the restrictions will drop your inlet air pressure.

[Toma]

Originally posted by HO2S


The air flow into a na cylinder should be 14.7 psi no matter the rpm. You will hit a rpm were the flame will chase the piston down the cylinder and not make any power. It should be around 6700 rpm. Same thing with forced induction. Their are more To power curves than the last 2000 rpm.

What??

Nonsense.

[revelations]

Originally posted by HO2S


The air flow into a na cylinder should be 14.7 psi no matter the rpm. You will hit a rpm were the flame will chase the piston down the cylinder and not make any power. It should be around 6700 rpm. Same thing with forced induction. Their are more To power curves than the last 2000 rpm.

[triplep]

Thanks for all the answers. Just a few questions.

What is a significant decrease in torque? As up to 6000rpm it stays fairly constant then starts to drop off around there.

Also to Toma I have attached my Dyno sheet (might look familiar) Based on the power curve, is the car starting to get restricted and hence why the power seems to peak? and is that why the Torque drops off as well? I know my redline is around 6700, and based on the dyno, it seems to slowly drop off at around 6000 rpm.

So if air is an issue, would a larger intake manifold and larger diameter throttle body help out? I have a feeling the car is a little starved for air at higher rpm. I could go from my stock 67mm tb to a 75mm tb, and I am wondering if there would be significant advantages to doing this.

[Toma]

Originally posted by triplep
Thanks for all the answers. Just a few questions.

What is a significant decrease in torque? As up to 6000rpm it stays fairly constant then starts to drop off around there.

Also to Toma I have attached my Dyno sheet (might look familiar) Based on the power curve, is the car starting to get restricted and hence why the power seems to peak? and is that why the Torque drops off as well? I know my redline is around 6700, and based on the dyno, it seems to slowly drop off at around 6000 rpm.

So if air is an issue, would a larger intake manifold and larger diameter throttle body help out? I have a feeling the car is a little starved for air at higher rpm. I could go from my stock 67mm tb to a 75mm tb, and I am wondering if there would be significant advantages to doing this.

Yeah, torque is basically a measore of "per suction event" efficiency. Ie, out of a possible 10 units of air, how many units is it actually ingesting per event. When torque is rolling of, your efficiency is also falling.

This is a combination of many things, and USUALLY the throttle body is not your major worry. Normally, it is the valve head itself, and the "throat" area just above the valve that is the biggest restriction in most motors.

I do not recall what motor this was??

If the cam is very conservative, there MAYBE decent power gains there without giving up much drivability.

[triplep]

It was the v6 black accord (this was about last year around this time). As far as the cams are concerned, I know that I had upgraded them from stock Accord cams to Acura TL type S cams, so they are more aggressive then the original accord cams. What would decent power gains be? I remember when we dyno'd it, we had an AFR of around 12.7, after much research (and other individuals doing testing), I have found that in open loop the ideal AFR would be around 13.7. I wonder if I were to change this so that it is around that, if I'd be able to see more power as well.

[Toma]

Originally posted by triplep
It was the v6 black accord (this was about last year around this time). As far as the cams are concerned, I know that I had upgraded them from stock Accord cams to Acura TL type S cams, so they are more aggressive then the original accord cams. What would decent power gains be? I remember when we dyno'd it, we had an AFR of around 12.7, after much research (and other individuals doing testing), I have found that in open loop the ideal AFR would be around 13.7. I wonder if I were to change this so that it is around that, if I'd be able to see more power as well.

Ahhh, yes. I remember.

Well, first, what kind of power gain are you after?

That is great power for a V6, and wasn't it auto?? A V8 93 Mustang only makes 185 lol.

Every motor is different, there maybe small gains leaning it out. I usually let NA Honda's out the door at around 13 to 13.2 or so. But yes, on some Honda engines, under certain conditions, we have continued to eek out power towards 14:1. But that is not normally how I would send a street, stop and go traffic car out the door lol. And we are talking small gains, maybe 5-7 hp if it picks anything up. The dyno tells me where AF needs to be, and where the point of diminishing returns is.

For your car, I have no experience, so trying it is the only way to know for sure.

Just put some nitrous to it lol!

[star-k]

Stock form: rpm looses slight power because of the rich a/f ratios. Factory programmed the ECU to prevent lean condition --> motor protection

Higher RPM is a result of several items modified working together in an orchestra, also note that there is not a single tuning item that will be generous enough to release extra power, it is the combination of several items combined.


ECU upgrade is highly recommended
valve spring retainers (titanium weight is lighter; shorter life)
valve spring seat pressure (should be higher to accomodate potential valve lift; consider dual valve springs)
and alot of other things ..consider the costs of tuning for both reliability and performance.

you can tune for purely performance, but the reliability is questionable.



better to go fi instead of NA build << could

[triplep]

Hahaha, no nitrous...

I honestly don't know if I have a specific goal as to what I want to reach, I think I just enjoy doing mods to my car and I haven't done one for a while. But if I had to put a number on it, I would say based on results, that 260+ would not be an unreasonable number. I have one mod already lined up for an intake spacer, I just have to find someone with a reasonable price to mill down an intake spacer for me.

And no it was a standard. I was just looking at the AFR and noticed that I am pretty consistent up to 5700 with a 12.4 AFR and then after I start to dip down to 12.1 (it is at this point as well that my torque beings to decrease as well). I just mention the 13.8 as a bench mark as most builds such as mine have been tuned to that AFR, and I am wondering if hitting that in open loop would have a significant advantage over the 12.1 that I showed close to red line. I think on the bottom end, I have enough power/torque, so I would be more interested in the upper end, hence I was wondering about the higher rpm.


I think that once we slow down at work (May) I will finally install my wideband, and maybe pay you a visit.

[triplep]

Originally posted by star-k
Stock form: rpm looses slight power because of the rich a/f ratios. Factory programmed the ECU to prevent lean condition --&gt; motor protection

Higher RPM is a result of several items modified working together in an orchestra, also note that there is not a single tuning item that will be generous enough to release extra power, it is the combination of several items combined.


ECU upgrade is highly recommended
valve spring retainers (titanium weight is lighter; shorter life)
valve spring seat pressure (should be higher to accomodate potential valve lift; consider dual valve springs)
and alot of other things ..consider the costs of tuning for both reliability and performance.

you can tune for purely performance, but the reliability is questionable.



better to go fi instead of NA build &lt;&lt; could

I was under the impression that higher compression engines were not ideal for FI? As I am pretty sure I am over 11.1 as that was the stock block with the stock stroke.

Also, there are no readably available options for FI. I have seen some turbo applications but they all seem mish-mash type of adaptations. The only one I would consider is either getting the comptech supercharger and altering it to my specific needs, or getting an MP90 and altering it to my needs.

[HO2S]

Originally posted by Toma

What??

Nonsense.

My bad, that was a inebriated post.

[tomt64]

Originally posted by HO2S


The air flow into a na cylinder should be 14.7 psi no matter the rpm. You will hit a rpm were the flame will chase the piston down the cylinder and not make any power. It should be around 6700 rpm. Same thing with forced induction. Their are more To power curves than the last 2000 rpm.

Confusing atmospheric pressure with absolute pressure possibly?