HP Numbers

[Sig]

think he (Gerry) said his car was slipping or had problems with the straps, so we had somewhat of an incomplete reading.

When the plot was first posted a while back, I thought the incomplete plot was the cause too. . But I looked at it closer tonight and it appears that the hp curve flattens out well before the graph broke up due to slippage. Which brought the question to my head of, "How'dhedodat without spray?" Even if nitrous was used (which is not what I am saying), that plot is still quite impressive.

 

[KGP]

Gerry had just installed that monsterous exhaust before the dyno (if memory serves me correctly), and I wonder how much that can play a role in achieving the TQ numbers he has. Honestly, if I were GJ I don't think I would want to give up any tricks of my trade. But then, GJ has always been pretty forthcomming in the knowledge he has gained. Anyway, the hp:tq curve being relatively equal is indeed impressive, no matter the reason how.

 

[len3.8]

When the plot was first posted a while back, I thought the incomplete plot was the cause too. . But I looked at it closer tonight and it appears that the hp curve flattens out well before the graph broke up due to slippage. Which brought the question to my head of, "How'dhedodat without spray?" Even if nitrous was used (which is not what I am saying), that plot is still quite impressive.

Can't say for sure, I wasn't there. I can say that at expo I rode in both cars His and in FactorX's, while both were impressive. His was downright lethal at about 14psi, and he wasn't using nitrous.
I think he stated that that run was at 15psi, I wonder what would happen at 18psi, and using 100 octane....
If porsche , ford, and other can get even HP/Trq numbers, what about Hondas configurations make it hard for you to believe they can't produce those numbers.

Man if that shoot out happens I am front and center.

 

[sjs]

You rarely see torque and HP at the same level in high RPM engines in general, where as very low RPM engines often have a torque number much higher than HP. That’s simply because HP is calculated from torque (torque * RPM / 5252) so all else being equal doubling your redline doubles your peak HP but not your peak torque. Make sense? Adding boost allows you to raise and extend the torque curve, with higher boost at higher RPM. The tuning process at high boost and RPM also includes backing off the timing quite a bit, which tapers off the HP curve faster than the torque curve and also contributes to what you see.

All that said, I don’t see where the chart says that HP and torque share the same scale. They probably do, but the numbers don’t quite add up right.

 

[len3.8]

Maybe he's talking about were the HP hit 507 and then started to decline, right before the slippage began.
Gerry stated that the HP/TRQ are measured on the same scale.

 

[Gerry Johnson]

Gerry or TurboNSX-

I have never seen a Honda engine, NA or FI, do this without the use of Nitrous. Do you know something that nobody else has been able to figure out?

Congratulations nonetheless.

Are you doubting me?

First off the design of the system as a complete unit working together has a lot to do with getting the best of both worlds HP and Torque, if I wanted to see peak HP numbers I could use a larger turbo along with some race gas, add some timing and make some high number power. This was not my goal in building the Turbo system for the NSX, I set out to make it a very fun and exciting car to drive, NO LAG and excellent power down low.
I do have NOS on my car and have not been able to use it on any of the dyno runs, after I remove the Tiatec rear defuser I will go back and try to get a run with the NOS, I myself want to see how much a 60HP direct port fogger system will give me on paper.

 

[Sig]

b

Are you doubting me?

First off ..................

WOW, that response was surely a surprise! You have read waaaayyyyyy too much into my words. I will take the blame for that for not more clearly showing the context of the question. Hopefully, this post will help.

I knew you had a nitrous kit on the car from looking at your website. Since there was not a direct mention of whether or not it was in use, at least from what I saw, I thought it is a normal question to ask.

Since it did not come across in the post, I found/find it rather impressive that you were able to accomplish this with or WITHOUT spray. KGP said something similar to that last sentence and I agree with his sentiments.

So in short, NO, I was not doubting you. Just curious if there was a basic principle of tuning that you were willing to share. In this case, I guess it is hardware selection as well as tuning. If not... no big deal, I understand the value of secrets that have cost you many, many dollars to develop through r&d and experience.

 

[sjs]

I don't think he was doubting you Gerry, just curious. (edit: oops, so he just said before I finished this) And I agree that more boost + octane = big HP. F-X was honest about the extra octane to get there. I think we all know that bragging rights are one thing and real-world usable daily power is another. But it's still fun to see the numbers move up to the same territory that other imports have been doing for quite awhile. And I don't think it will be long before a few cars are running around with the ability to turn the wick up this high when they want to. I'm back to measuring under the hood for a small fuel cell to hold the hi-pop.

 

[Yellow Rose]

Does hp = torque at 5252 rpm? Isn't there some kind of formula like that?

The equation you are thinking of, comes from the textbook titled "Mechanical Engineering Design" by Shigley.

T = (5250 x HP) / RPM

Multiplying both sides of the equation by RPM shows that in theory, HP = T at 5250 RPM.

 

[apapada]

Does hp = torque at 5252 rpm? Isn't there some kind of formula like that?

The equation you are thinking of, comes from the textbook titled "Mechanical Engineering Design" by Shigley.

T = (5250 x HP) / RPM

Multiplying both sides of the equation by RPM shows that in theory, HP = T at 5250 RPM.

This formula does not apply to FI systems, just NA engines. Then there are "corrections" applied as you will notice not all HP curves meet the TQ curves at 5252

 

[CiaoBoy]

This formula does not apply to FI systems, just NA engines. Then there are "corrections" applied as you will notice not all HP curves meet the TQ curves at 5252

What?!? That doesn't make sense at all.

TQ is basically HP per time. How much HP per time? Well, the coefficient changes depending on what units you want to use, but that fundamental relationship between HP and TQ is always true.

TQ=HP / time

or HP = TQ * time

It doesn't matter whether the engine is NA or FI.

-CiaoBoy

 

[apapada]

What?!? That doesn't make sense at all.

It doesn't matter whether the engine is NA or FI.

Please remember that into the above formula (especially the 5252 part) they are some assumptions which, The way I understand it, are no longer valid for a FI engine, and one needs to correct for the added boost.

From memory, when using a FI engine, you are better of using the following formula (which equals the previous one if boost=0 like in a NA engine):
HP=(( 14.7 + boost)/14.7) * Torque x RPM/5252
Can't remember for sure why is that, I believe it had to do with the final compression ratio (with boost) vs the the built compression ratio of the motor.

 

[Yellow Rose]

This formula does not apply to FI systems, just NA engines.

Actually, apapada you are VERY wrong.

The mathematical derivation of the formula that I cited is based on fundamental basics which relate to an engineering field called "Mechanics of Materials". If you like, I will fax you the pages of my textbook and you will see that the derivation of the formula makes no reference to a forced induction engine. Why, it makes no reference to a naturally aspirated engine. In fact, the diagrams are not even predicated an engine at all. The free-body-diagram used for the calculations in the formula derivation depicts forces acting upon a shaft. For all we know, this could be a jet engine or a steam turbine or an electric motor or or or.

There are a few dyno plots here on PRIME that show the curves crossing at slightly higher RPM.....I surmise this to be attributed to slip between the drum and the tire because of the outrageous engine output.

Closing comment.....mine is supercharged and the torque curve and the horsepower curve exactly at 5250 RPM. The “5250” has nothing to do with compression ratio either.....the two curves crossed at 5250 RPM when I was still running 10.2: pistons.....I now run 9.5:1 pistons.

 

[KGP]

Okay....

So why do Gerry's HP and TQ lines cross at ~5800? Slippage on the drum?

[Edit]: In real world terms I could care less, just curious. I know what GJ's car can do, and it is simply amazing.

 

[Sig]

Re: Okay....

So why do Gerry's HP and TQ lines cross at ~5800? Slippage on the drum?

In addition to slippage on the drum, could aggressive timing control (retard or advance) affect this crossover point?

 

[Dinan M3]

Typically this anomoly happens when the computer (or operator) scales the magnitude of the vertical axis for HP and TQ differently.

 

[Gerard van Santen]

This one is mine:

CTSC 6PSI, CT headers, test pipes, CT Supertrap exhaust, K&N cold intake, short gears.

 

[sjs]

Typically this anomoly happens when the computer (or operator) scales the magnitude of the vertical axis for HP and TQ differently.

Which was why I wondered about the scales on GJ's chart. I don't doubt the overall results but there appears to be something just a bit off.

 

[apapada]

This formula does not apply to FI systems, just NA engines.
Actually, apapada you are VERY wrong.

I guess the misunderstanding comes from the combination of these two formulae:

HP=Torque x RPM/5252 and
HPafter = ((14.7 + boost)/14.7)*HPbefore

from http://www.superchargersonline.com/faq.asp?Tell=1& being one of the sites mentioning this:


How much power could I expect to gain with a supercharger?
Answer: Roughly, you can expect to gain about the same power difference percentage as you gain induction pressure percentage. The equation is HPafter = ((14.7 + boost)/14.7)*HPbefore. For instance, if you have a 200HP engine and you add 7.5psi boost, you can expect to have about 300HP. This is an estimate, not an exact calculation so take it for what it is worth. In reality, it will likely be just a bit less than that due to inefficiencies and air density losses due to heating. If you are intercooled, you will get closer to this estimated power.

 

[Dinan M3]

Which was why I wondered about the scales on GJ's chart. I don't doubt the overall results but there appears to be something just a bit off.

So let's go back to first principals:

T = (5252 x HP) / RPM

So if you look at the HP at 5252 RPM, the 5252/RPM term = 1, hence it drops out and you can deduce that the torque magnitude is equal to HP there.

ln the plot at issue, the HP scale is explicitly disclosed and the HP is about 460 at 5252 from which we conclude that the torque is also about 460 at 5252. So clearly the T is being graphed on a slightly different scale and at 5252 RPM we are pretty much at the peak torque, from which we conclude that this car is showing about 460 peak torque and about 507 peak RWHP.

Q.E.D.

 

[len3.8]

Work with me guys, I am still learning, and trying to apply some logic. So by all means correct me if I am wrong. (Most likely)
If 15psi equals one atmosphier, that means if you make 250hp at the wheels NA than at 15psi you would have 500hp, thats if everything is perfect. Would 3 more lbs of boost give me another 140hp? Or would my base NA car have to truly put out 300+ HP?
Did I make sense?

 

[sjs]

So let's go back to first principals:

T = (5252 x HP) / RPM

So if you look at the HP at 5252 RPM, the 5252/RPM term = 1, hence it drops out and you can deduce that the torque magnitude is equal to HP there.

ln the plot at issue, the HP scale is explicitly disclosed and the HP is about 460 at 5252 from which we conclude that the torque is also about 460 at 5252. So clearly the T is being graphed on a slightly different scale and at 5252 RPM we are pretty much at the peak torque, from which we conclude that this car is showing about 460 peak torque and about 507 peak RWHP.

Q.E.D.

Which, if you go back through my posts, is what I was suggesting until I was reminded by Len that according to Gerry HP & Torque were on the same scale. I'm not all that concerned either way, especially since it was only a partial pull interrupted by traction problems, and was only commenting on it because people were questioning details about that chart.

Perhaps Factor-X will post theirs and the debate can start again.

 

[sjs]

I guess the misunderstanding comes from the combination of these two formulae:

HP=Torque x RPM/5252 and
HPafter = ((14.7 + boost)/14.7)*HPbefore

Notice that RPM does not appear in the second equation. Torque does indirectly because it increases which in turn raises the HP, but they both go up proportionally at any given RPM and should therefore still cross at the same time.

 

[Dinan M3]

Which, if you go back through my posts, is what I was suggesting until I was reminded by Len that according to Gerry HP & Torque were on the same scale.

I'm not arguing with you - just presenting the outline of a proof based solely on the data presented and the equation for T = f(HP@RPM). Chris also did the same calculation earlier. Note that the calculated numbers correspond pretty well with GJ's prior 503RWHP/412TQ run at 16 PSI though in the more recent run the mid-range torque seems much improved.

 

[Yellow Rose]

HPafter = ((14.7 + boost)/14.7)*HPbefore

This equation applies only in an adiabatic process.....and we all know that compressing air raises the temperature. Classical thermodynamics. Regardless, it provides an approximate horsepower with added boost.

I will go back to my earlier post today. Mine is supercharged, and the horsepower curve and the torque curve cross each other at 5250 RPM.