Matching shift points to get the most power from the 5sfe, a discussion about the 5s Options

[enderswift]

alot of people (myself included) go on and on about power modding the 5sfe when in reality theres really not that much to do except throw cams in or turbocharge. Because that sucks I figured I would try to squeeze out the most power from the 5s by shifting at the perfect rpm's. After mulling over stock 5s dyno charts and testing at the local warehouse lots, I figure shifts at 5200 get you the most power.

heres my reasoning. prepare for your eyes to bleed:

The power produced by an engine is defined by two units of measure, HP and TQ. Alot of people have a hard time telling the difference between the two. I like to think of TQ as the ability to overcome the inertia of mass, and HP as the rate of change of torque. So a high torque low horsepower engine wont accelerate very fast because the rate of change of its massive amounts of torque will be low. The benefit to this setup however, is either you can tow ALOT, or dont have to worry about having a heavy ass car. The way people make cars with this setup go fast is to use steep gear ratios where the torque muscles them to speed, like my friends mustang. The flip side is high horse power low torque cars READ: honda. With these setups the engine cant overcome alot of mass but the rate of change of its torque is impressive. Weight is the plague to these setups as the torque cant fully utilize the horsepower. The way people make civics (non turbo) fast is strip down as much weight as possible and multiply torque through gearing. The PERFECT kind of setup has HP and TQ distributed equally throughout the whole rpm range.
good luck finding/making one. all this being said the ideal TQ/HP balance on the 5sfe sort of occurs between 4600 and 5100. At this point the horsepower and torque are able to utilize each other better than at any other spot on the rpm range. To make up for our transmission gearing, shifting at 5200 brings the revs right into the meat of the 46-51 range. this = most power. observe:



This chart was borrowed from celicatech and cleaned up a bit for our purposes. I'm sure theres a member here who will recognize it

anyway our engines have a good amount of torque at low rpms, which makes the heavy ass celica feel peppy but the horsepower isnt there to really make ideal use of it. further up the HP starts to match the TQ and thats when the greatest acceleration occurs. At one point the HP and TQ are equal but because of our ****ty flowing head thats actually a bad spot to shift for. After 5200 rpm the 5sfe turns starts to wheeze out as the head wont let it flow any more air.

Im no engineer (yet) so theres probably a flaw in my reasoning somewhere so free to correct me politely or chip in some wisdom.

please tell me if I am completely wrong or not. this is as best as I could figure

This post has been edited by enderswift: Aug 14, 2008 - 12:06 AM

[purplegt4]

if you shift too early would you not be at a good rpm for the next gear?

[enderswift]

very true but shifting at 5200 brought it down to around 46/700 which is the beginning of powerband. I tried revving to a higher rpm but it just felt like the engine got louder without actually accelerating anything. So the last thing you want is to waste time revving higher. I see what you mean though, making sure to set up the next shift properly so as not to bog the engine. Ill try shifting at 5300 again to see if the ass dyno registers different than before. hopefully my friend isnt sick of standing there with a stopwatch

This post has been edited by enderswift: Aug 14, 2008 - 12:20 AM

[enderswift]

http://www.youtube.com/watch?v=zo-U_TmgtGk

a video of me messing around with different rpm shifts. the first one was a lower shift 4900 or so. the next one was the ideal 5200

[808celica]

hmmm imma have to try this in a safe local track environment i do shift at 5300 when doing spirited driving and 3rd sucks so i cant help but shifting at 5800, again in a safe local track environment. i would love cams

[playr158]

^cams aren't really going to help outside of a FI application.

[Rayme]

The power produced by an engine is defined by two units of measure, HP and TQ.

Power = Horsepower, reapeating yourself a bit? hehe..

Power = Horsepower/Watts/Joules. Horsepower is the results of torque over TIME.

The ideal shift point will change with every gear because they have different ratios.

The ideal shift point I read (and it makes total sense) is when you make just as much HP at the shift point and where you land in the next gear. Example : 5800 RPM shows as much HP as 4350 RPM. You NEED the gear ratio and do a mathematical formula to find that ideal spot.

Your theory is flawed as the 5s-fe makes its top HP at 5400 RPM...use it!...for any given engine, even high reving honda's, the HP/TQ curve will meet around 5200 RPM...Now you don't want to shift at 6000 RPM in a B16 don't you?

Here's a BMW M3 dyno...the M3 has that extremely nice flat torque curve that is ideal.


This post has been edited by Rayme: Aug 14, 2008 - 8:54 AM

[Terracar]

The power produced by an engine is defined by two units of measure, HP and TQ.

The ideal shift point will change with every gear because they have different ratios.

I will agree with the above logic somewhat - the ideal point does change with each gear due to gearing ratios. In a perfect world you would want to shift just after reaching max power while not bogging the engine - this way you/the engine is constantly accelerating as opposed to accelerate/choke/fall off.

I didn't see the point to adding the dyno of an M3 - offered nothing for the post IMO.

[Rayme]

The power produced by an engine is defined by two units of measure, HP and TQ.

The ideal shift point will change with every gear because they have different ratios.

I will agree with the above logic somewhat - the ideal point does change with each gear due to gearing ratios. In a perfect world you would want to shift just after reaching max power while not bogging the engine - this way you/the engine is constantly accelerating as opposed to accelerate/choke/fall off.

I didn't see the point to adding the dyno of an M3 - offered nothing for the post IMO.

"The PERFECT kind of setup has HP and TQ distributed equally throughout the whole rpm range.
good luck finding/making one."

That graph was to show that some car do have a greatly distributed torque curve, most of those cars are high end cars though.

[enderswift]

what i meant by finding a car with equal tq and hp throughout the curve was just that. your bmw chart still shows two separate lines. im talking about one line representing both measures... THAT would be sick. I think the tesla roadster with its electric motors is able to come close....

either way, I agree with the idea that shift point heavily rely on gear ratios, but I still think 5200-5300 is the rpm to shift at simply because its the best balance reguardless of the gear your in.

why would I shift at 5400 rpm when at that moment the engine is producing 109 hp and 109 tq.Granted its the most efficient, but If you look a few hundred rpm back to 5200, the hp is like 108 while the tq is 120! in a heavy car like this the extra tq matters and since the hp is the same as at 5400, why rev higher and rob yourself of time? If this car weighed less I would say sure go ahead shoot for that extra horse, but the trade off of 10 ft/lb for one hp doesnt make sense. its better to have 108 hp working with 120 ftlb than 109 hp working with 109ft/lb. Again if this car weighed less horsepower would matter more, but in this case you want the torque.

This post has been edited by enderswift: Aug 14, 2008 - 12:37 PM

[Rayme]

what i meant by finding a car with equal tq and hp throughout the curve was just that. your bmw chart still shows two separate lines. im talking about one line representing both measures... THAT would be sick. I think the tesla roadster with its electric motors is able to come close....

either way, I agree with the idea that shift point heavily rely on gear ratios, but I still think 5200-5300 is the rpm to shift at simply because its the best balance reguardless of the gear your in.

why would I shift at 5400 rpm when at that moment the engine is producing 109 hp and 109 tq.Granted its the most efficient, but If you look a few hundred rpm back to 5200, the hp is like 108 while the tq is 120! in a heavy car like this the extra tq matters and since the hp is the same as at 5400, why rev higher and rob yourself of time? If this car weighed less I would say sure go ahead shoot for that extra horse, but the trade off of 10 ft/lb for one hp doesnt make sense. its better to have 108 hp working with 120 ftlb than 109 hp working with 109ft/lb. Again if this car weighed less horsepower would matter more, but in this case you want the torque.

You idea is flawed, its impossible to have a horsepower and torque curve following themselves. The Horsepower curves is calculated from the torque curve.

I know what you mean by "shifting to get back in the torque"...but you are shifting ! Even though the engine only makes 109 tq @ 5400 RPM, shifting to land @ 4200(You typed 5200 but I see you meant 4200) with 120 tq will results in LESS torque to the wheel because you just changed the mutliplication ratio by changing gear.

torque without counting final drive:
1st gear with 3.2 ratio @ 5200 rpm @ 109 tq = 348 @ wheel
2nd gear with 1.9 ratio @ 4200 rpm @ 120 tq = 228 @ wheel

that's why you should look at the HP curve to check your shift point.

This post has been edited by Rayme: Aug 14, 2008 - 1:09 PM

[808celica]

^cams aren't really going to help outside of a FI application.

i have a turbo from a 93 mr2 along with some goodies so maybe i'll be boosted soon.........or not

This post has been edited by 808celica: Aug 14, 2008 - 1:08 PM

[enderswift]

i know its impossible. That would be ideal though. I didnt mean 4200 rpm i meant 5200. If you look at my original chart, the "ideal power range" is what im trying to shift for. usually shifting at 5200-5300 lands me in the middle of that range. I dont think your giving me enough credit, anyone can tell that shifting at 4200 is horrible just by how it feels and I would have to be really stupid to think otherwise. what im talking about is utilizing the power range i marked off in the chart above. anything below that range cant be used because of the gear ratios. I think we both have the same idea in mind but keep misunderstanding each other. Back to what you said before "5s-fe makes its top HP at 5400 RPM...use it!"; I'm not very far off: "To make up for our transmission gearing, shifting at 5200 brings the revs right into the meat of the 46-51 range. this = most power". very similar no? I think we're just splitting hairs.

[Rayme]

i know its impossible. That would be ideal though. I didnt mean 4200 rpm i meant 5200. If you look at my original chart, the "ideal power range" is what im trying to shift for. usually shifting at 5200-5300 lands me in the middle of that range. I dont think your giving me enough credit, anyone can tell that shifting at 4200 is horrible just by how it feels and I would have to be really stupid to think otherwise. what im talking about is utilizing the power range i marked off in the chart above. anything below that range cant be used because of the gear ratios. I think we both have the same idea in mind but keep misunderstanding each other. Back to what you said before "5s-fe makes its top HP at 5400 RPM...use it!"; I'm not very far off: "To make up for our transmission gearing, shifting at 5200 brings the revs right into the meat of the 46-51 range. this = most power". very similar no? I think we're just splitting hairs.

I understand what you mean, but you seem to make a little too much focus on the torque (read your first post!). Check your graph and ignore the torque, and base your shifting around the HP curve . You are not far, but then most gasoline engine will need to be shifted near the redline anyway to get the best acceleration. I thought you're highest efficieny was where you thought the engine should be, not where you landed.

This post has been edited by Rayme: Aug 14, 2008 - 3:35 PM

[enderswift]

i guess it all depends where you place the emphasis hp or torque. like i mentioned before it really depends on the application, heavy cars with alot of mass benefit from the additional torque while light cars enjoy the rush of HP. I just like to shift so that the rpm guage falls right back into the area with the best hp/tq ratio. the best of both worlds. granted its not perfect but i feel it gives the best combination for our particular car. This is something I could talk about for days

[Rusty]

Power = Horsepower/Watts/Joules. Horsepower is the results of torque over TIME.

that is the best piece of info I have heard in a while

[goferris]

found this and thought I would post it

shinydonuts

[RickJamesBish]

To OP, I think you're on the right track. The point where TQ/HP always overtake each other is 5250 RPM.

[SlickRick]

Power = Horsepower/Watts/Joules. Horsepower is the results of torque over TIME.

that is the best piece of info I have heard in a while

i dont think so. HP is simply a measure of time, without HP TQ is nothing. It sounds a little backwards. HP is simply the WORK it take to move 550 pounds 1 foot in 1 sec. TQ is a rotational force but HP is the TIME is tame 2 make that force measured in revolutions of the crankshaft.

[enderswift]

its a tricky subject for sure. one that my calc and phys classes will take care of eventually till then my celica is stored away in my garage for the winter