Veloce Raptor

Just to be clear, an E36 Euro M3 motor is very very different in power characteristics than a US spec E36 M3 motor. It is alot more like the E46 M3 global motor than anything else, IE, tons of power approaching at at the very high redline. The stock US E36 motor does not behave the same way. It was designed to make more low down torque which BMW at the time assumed was asligned with how Americans drive

mark kibort

Yes, Lets be clear. the curves i posted was a euro e36 vs (unnknown less modified m3) ... but in case you want to see a stock e36, here is a graph below. since you mention it, i also included a S54 M3 graph too.
dont confuse street driving vs racing..... if you are going to race either, you shift at redline, without exception in all gears. this is quite easy to see from the graphs and knowing the % RPM drop for each gear change.

you mention how "americans drive" well, you do have a point there. and the higher torque in the lower regions of the engine speed range, allow the car to be driven with adequate acceleration arount town, without High RPM.

again.. to the OP's question and my point to peter, it is VERY easy to determine shift points by just looking at a graph without any "program, or charts". Hp to the wheels at any speed , is a measure of its capacity to accelerate. maximize/optimize that , and you maximize acceleration period. with the BMW e36 the shift point from 7000rpm from 2nd to 3rd puts you at 4600rpm. SO, you better redlne for max accel!

BELOW: e46 S54 M3 dyno and two E36 dynos... very easy to tell the difernce by top RPM as you say... the M3 e46 S54 motor tachs out to 8krpm

for reference.: gear ratios for the M3
M3 Coupe 95 E36 Coupe Manual
1st thorugh 5th gear : (4.2 2.49 1.66 1.24 1.00) example above: 2nd to 3rd shift has a resultant RPM of 66% of redline or 4600rpm, 3rd to 4th would be 5200rpm... Also no question at all to redline for max accel

Cloudspin

Thank you. Please PM me when he does as I can see where this thread is going and I don't want to go along with it.
Thanks again.

mark kibort

cloudspin... did you read my post? i made a pretty good effort to make the facts very clear and show how easy it is to determine shift points by use of a Hp curve and gear spacing.
These discussions only go sideways when folks dont understand or accept the facts or rely on butt dynos or intuition.
Again, Im only trying to help the OP with his question of "where to shift?". I've provided the tools that are quite simple to do so. what you do with the information is up to you. the programs available are good too, it's just, I hope after reading my last post, you can see that you dont need them to determine shift point as they are extremely easy to determine, accurately(no guessing)

mark kibort

Peter,

I went though some effort to respond to your post and provide evidence that engine torque values are not more important in determining shift points, and that HP can determine these points relatively easy.

1. Can you explain why the torque curve is "more important" for this task, and by using the graph that i made for YOU? And can you tell me how any "program" will come up with a different shift point for a 997C2, than what the graph i provided indicates with the hp curve?

2. respond to my post made to provide the information you requested (plot torque on the 997 HP curve, which i provided.)

The link you provided was a purely hypothetical example, to show thrust cross over points. it showed pre-redline shifts for its torque curves. However, this is a very rare instance and yet still can be determined by the use of HP curves alone (with known gear spacing/ % RPM drops) to achieve the exact same result./answer.

The entire purpose of my response and information was to provide some clarity of the relationship of the HP curve and torque curve (directly tied together), and that HP can be absolutely synonymous to rear wheel acceleration forces, at ANY vehicle speed. With this information, anyone with a HP curve has the ability to determine shift points in a few seconds without the use of any other assistance or automated programs

Gofishracing

Where were you ?? I was worried

Thundermoose

Here's a good article that I found while trying to understand dyno's a bit better that has some relation to this thread. Link is found at the bottom of my thread.

One thing that puzzled me (though may have been known to others) is why you get pretty much the same HP vs RPM curve regardless of which gear you run the dyno in. Actually, if you select your 1:1 gear you get slight boost in HP curve due to reduction in parasitic transmission losses.

My initial hypothesis before reading this article is that you'd get higher readings with lower gear as that applies more torque to the drum and the resultant curve would show this. However it doesn't.

The article helped me understand the math behind the dyno.

HP as measured by inertia dyno (e.g. dynojet) is proportional to dyno inertia x angular acceleration x angular velocity. Basically, although gearing is a torque multiplier it does so in the simplest terms by trading torque for speed (and vice versa). So a 3rd gear pull may have more angular acceleration (than a 5th gear pull) but it will do so at a lower angular velocity. The power output from the engine will be very similar though across that rpm range. This is why dynos measure HP and then back calculate torque using rpm and measured hp.

What does this have to do with optimum shift points. One camp keeps talking about looking at torque, but the HP math suggests that optimum shift points have less to do with the torque curve than with the HP curve. Pretty much the same thing is said in the link that Matt posted (https://www.hpacademy.com/technical-...ractive-force/)

Let me illustrate with my E46 M3. I make max torque 248 ft-lb at 5200 rpm. HP is 244 at 5200 rpm. Max HP is 346 at 8200 rpm. If you subscribe to Torque matters you may conclude that I would short shift in the 5200 rpm range to maximize torque. However, the HP math would say this is wrong.

Per the math, HP = mass x acceleration x velocity. Since velocity and math are fixed at the point of the upshift, it stands to reason that acceleration would be reduced to (244/346) at 5200 rpm of what it would be at 8200 rpm. Even though the torque value is the highest at 5200, I would still accelerate slower than at 8200. Dyno's measure HP and then back calculate torque using RPM. The number is interesting but HP is the true measure of how fast in terms of speed and acceleration the engine can move the car.

So far my car, I want to shift at 8200 (max HP). I believe 997.1 C2S is making max power at 6500 rpm which is about where I'd shift.

I am not a pro but these are my conclusions based on the math and my analysis.

http://wotid.com/dyno/content/view/16/35/

mark kibort

Good job doing some research, and you were correct in your analysis, but incorrect on the conclusion of where to shift the 997C2. Again, you saw that your 8200 RPM value was max HP and you would want to shif there, but not if HP was still higher than in the next gear. in other words, YOU DONT SHIFT UNLESS HP is GREATER BY SHIFTING. (thats where you need the gear spacing)
Not all cars have peak hp at redline.. some do, not all. (and there are some exceptions... we really want the most average HP or HP-seconds that can be applied. averaging HP shift vs post shift is a easy way to integrate for area under the curve, and close enough for most comparisons)

You mentioned a few equations, but let me summarize.
Acceleration = power / (mass x velocity) this means for any comparison, the greater HP will yield the greater rear wheel forces and therefore , acceleration.

Just like energy is a body's ability to do work
HP is a body's ability to accelerate.

Engine torque can be any value... ...to figure out thrust forces you need a lot of information, and the "calculator programs"referenced in this thread. rear wheel forces go down proportional with speed, even while HP is or can be constant. (best case) So, with HP, it is always the simplest way to compare acceleration. You can compare ANY acceleration potential by just knowing HP at any same vehicle speed. its really just that simple.

this is why you just need a HP curve and RPM drop for gear ratio (in %) and you can easily, simply find shift points

The shift point for the 997 is redline. (in this case 7700rpm, not 6500rpm at peak HP), as it is for ALL the modern BMWs ive ever seen.
why? because the pre shift HP level is higher at redline , than it is post shift.
Let me challenge your conclusion.... got to the 997C2 HP /torue curve i posted and multiply out the rear wheel torque... see where you think shift points will be..... (hint, they willl be at redline, becuase post shift RPM HP is always less than redline for the car, and HP determines rear wheel forces at any speed)


(as a note)
matts link is generalized graphical description of this... yes, there are short shift points , as i have shown in one particular car engine dyno graph, but they dont represent modern engines or gear box ratios.. (clearly stated in the article) . it was done to show the overlap points of where post shift HP is greater and thus post shift rear wheel forces..

Coochas

morsini

Bahhh!!!!

Thundermoose

Thanks for the clarification on the 997. Most of my initial analysis was based on my car an I brought in the 997 as afterthought to connect to original question. I support your points. Cheers .

Dbuck

Does this help?