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> RPM reading @ 110km/h, survey

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sleepwalker
post Aug 1 2008, 09:15 AM

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The lower the RPM, the more efficient the engine and hence better fuel consumption. However, it cannot be used as a comparison as the engine itself would be the main factor in the calculation of fuel consumption and not the gear ratio. Furthermore, there are no aftermarket parts to change gear ratios (too much work to be cost effective) and hence it is seldom a factor in the calculation of FC.

The gear ratio is only effective in calculation if you are comparing 2 cars of the same make, same engine but different gear ratios.
sleepwalker
post Aug 1 2008, 09:22 AM

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QUOTE(jlce10 @ Aug 1 2008, 09:15 AM)
proton waja
2.8k-3k RPM @ 110km/h
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How could you have a range of 2.8k to 3k for your RPM? RPM per km/h is always fixed per gear and never changes until you suffer clutch slippage.


Added on August 1, 2008, 9:23 am
QUOTE(joanalooidog @ Aug 1 2008, 09:19 AM)
persona high rev engine mah....................
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Actually, it's more of low power and need a shorter gear ratio to keep the car moving at high gear.

This post has been edited by sleepwalker: Aug 1 2008, 09:23 AM
sleepwalker
post Aug 1 2008, 09:33 AM

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QUOTE(Ultima @ Aug 1 2008, 09:24 AM)
maybe his car is going downhill, so at 2.8 oledi got 110km/h tongue.gif
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Which part of 'fixed RPM per km/h' that you don't quite understand? It's a constant and not a variable as the gear ratio is fixed per gear.
sleepwalker
post Aug 1 2008, 09:42 AM

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QUOTE(advanceNissan @ Aug 1 2008, 09:34 AM)
I think the valve timing mechanism will also affect the RPM reading. My Sentra 1.6 MT driving at 110km/h, the rpm will increase or decrease slightly a little bit, from 2800 to 3000 rpm.
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IT has nothing to do with the engine. Your RPM meter is screwed if it moves while you maintain constant speed, or that your clutch is slipping. Your RPM is calculated at the engine. It is transferred to the gearbox by a big flywheel and clutch and turns the gearbox. The gearbox has fixed gears that will change the RPM of the engine to the RPM of your wheel. Each gear has a fixed ratio.

I don't care even if you jack your car up and spin the wheels. If it is 3000rpm at 110km/h on the road, it is still 3000rpm at 110km/h when the car is jacked up in the air and the wheels spinning freely.


Added on August 1, 2008, 9:44 am
QUOTE(kcng @ Aug 1 2008, 09:36 AM)
different size rim will cause your speedo meter to over or under read and will make your rpm reading @ 110 km/h not accurate anymore

senario example
13" 110@3k
15" 120@3k <-- bigger rims cause the speedo meter to over read
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Wrong. Rusty nail is correct. Your RPM per KM/H on your dashboard will still remain the same. The only thing that will change is your actual speed and not speedo speed, meaning if the police shoots the laser camera at you, then you will be driving at 120km/h but speed still show 110km/h. That is how bigger wheel OD will affect you. It will not affect your speedo but affects your actual speed.

This post has been edited by sleepwalker: Aug 1 2008, 09:44 AM
sleepwalker
post Aug 1 2008, 10:02 AM

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QUOTE(LeVis_Jeans @ Aug 1 2008, 09:51 AM)
Bro, you are wrong.
He mean RPM vs KMH..
It really will change when u change bigger sport rim
Police laser camera will shoot on our KMH speed. but we also see the speed is correct.
Only the RMP change lower litter bit, but laser camera is capture our KMH meter, not RPM meter.

Use math calculation..You will get when u use
KM/H = meter per hour VS RP/M = Round per min
13" 110@3k (you will feel your car powerful, pickup damn good)
15" 120@3k (you will feel still power ok)
17" 125@3k (you will feel your car no power)
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You are wrong. It will not change. Your speedo comes from your gearbox. It is fixed. Changing the size of the wheel will not change the readings on your speedo meter. It does not matter whether you change to 20inch. If the rpm is 3000rpm at 110km/h on the respective tacho and speedo meter, it will remain at 3000rpm at 110km/h even if you change it to 20inch (even though you are travelling at 130km/h).

You have to remember that there are always 2 speeds.

1. KM/H on speedo meter (this cannot change as it is a fixed reading from the gearbox)
2. KM/H actual speed (this will change depending on the OD of your wheel)

What we are talking here is the reading on the speedo and tacho meter. Actual speed aka real speed aka speed captured by speed camera will change but not the reading on the speedo and tacho.

We are talking about the speed reading on the speedometer. That is the only speed that we know. You will NEVER know your actual speed until you get caught by the police or go through one of those speed indicators like the one on Kerinchi link.

This post has been edited by sleepwalker: Aug 1 2008, 10:04 AM
sleepwalker
post Aug 1 2008, 10:13 AM

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QUOTE(chitchat @ Aug 1 2008, 10:07 AM)
sleepwalker: can you explain a bit what is "clutch is slipping" ? Clutch want finish already, no teeth ?
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The clutch has no teeth. The clutch disc has materials similar to the brake pads. Once that wears out, it starts to slip.

Engine crankshaft -> Flywheel -> Clutch -> gearbox. IF clutch is working then..

3000rpm at crank -> 3000rpm at flywheel -> 3000rpm clutch -> 3000rpm gearbox

If clutch slipping then

3000rpm at crank -> 3000rpm at flywheel -> 2500rpm clutch (slipping, can't hold on to flywheel) -> 2500rpm gearbox.


THis is just a rough explanation. Go google for full explanation.

This post has been edited by sleepwalker: Aug 1 2008, 10:15 AM
sleepwalker
post Aug 1 2008, 10:25 AM

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QUOTE(sphiroth @ Aug 1 2008, 10:06 AM)
I feels that there is no difference in term of FC while cruising at 110km/h and 14km/h. Several CPS user also confirmed this.  hmm.gif
Correct. Only the actual speed will change when changing rims size. Can try to googled cars bible and use the provieded calculator to see how much the difference.
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FOr a moment there I thought you wrote 14km/h.. wait.. you did write 14km/h but you meant 140km/h right?

There would be a diffence. The other CPS users are wrong. For most road cars that is not aerodynamic in shape (like those lambo/Ferrari type), wind resistance becomes your number 1 fuel comsumption killer. For most cars, max efficiency is gain around 90-100km/h where the best rpm to speed ratio is gain and wind resistance is not an issue. Any slower and the rpm to speed ratio is no longer efficient as you take longer to reach your destination and any higher speed would encounter wind resistance that will require more fuel to keep the car running at that speed.
sleepwalker
post Aug 1 2008, 12:44 PM

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QUOTE(Cahill @ Aug 1 2008, 12:30 PM)
there are plenty of aftermarket 1-5 gear ratio and final drive. They even can custom made for you if your pocket is deep enough.

But you are right, the RPM at certain speed is all affected by the gear ratio and final drive.
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No there isn't and custom made ones are not considered as plenty in the market. Plenty in the market means you can walk into BROTHERS and say.. "I'd have that ratio mixed with this one and put them all into the gearbox while I go next door mamak for a teh tarik". That I would consider as plenty in the market.

Gear cogs are not something you find on the shelf in every shop. It is good info to have about RPM per KM/H but that is all.. just nice to have. It is not something we can change easily or even make use of in our daily course of driving and modding. It takes some serious 'moolah' to get it done and not worth it if it is just for FC.

This post has been edited by sleepwalker: Aug 1 2008, 12:45 PM
sleepwalker
post Aug 1 2008, 03:17 PM

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QUOTE(Ultima @ Aug 1 2008, 02:56 PM)
so lets say im using campro now n using this INVECSII (i think) gearbox from mitsu...

izzit possible to change to other gearbox? lets say from mitsu also, izzit possible?

btw, i still dun get it, in campro, got engine braking concept rite, the one which will lower ur gear when u going downhill..

will it consume petrol more? lets say i drive at 90km/h with around 2.6k rpm, n suddenly the engine braking activated when going downhill without pressing the pedal..

so should i press the pedal more lets say 110km/h at 3k rpm so the engine braking will not activated or juz let the engine braking lower the gear and make it whooping at around 4k rpm at 90km/h without pressing the pedal sweat.gif

which one consume less fuel? sweat.gif

sori if im talking crap here sweat.gif im no good in engrish sweat.gif
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Engine braking does not use fuel. At that moment, it is the wheels driving the engine and the throttle body is shut. There is no need for fuel to go into the engine until the idling control valve takes over when the RPM drops too low. So there is no waste of fuel.

Those people driving autos would appreciate the engine braking feature in the campro when they come down from Genting.


Added on August 1, 2008, 3:19 pm
QUOTE(phas3r @ Aug 1 2008, 02:41 PM)
Satria Neo 1.6(A) 110km/h = 3000rpm highest gear(4th)

so if the readings of the speedo are not affected by rim size, means say if 13" rims, 110km/h real speed,110km/h speedo speed, 3000rpm.....
n then use 16" rims 130km/h real speed, 110km/h speedo speed, 3000rpm..
means use bigger rims can make your car quieter??
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Most of the time the differences is maxed out at about 5% and not as much as you have mentioned. We were over exaggerating our examples before this to emphasis the point of the discussion.


Added on August 1, 2008, 3:22 pm
QUOTE(b00n @ Aug 1 2008, 02:44 PM)
Quieter?....... rclxub.gif
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He thinks that he could oversize his tyre to the point where he gains a 20% increment in speed difference so that he could actually travel at 3k rpm @ 110km/h (meter speed) but moving at 130km/h on his actual speed.

This post has been edited by sleepwalker: Aug 1 2008, 03:22 PM
sleepwalker
post Aug 1 2008, 03:39 PM

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QUOTE(LeVis_Jeans @ Aug 1 2008, 03:27 PM)
No use fuel no into engine will mati engine laa..haha


Added on August 1, 2008, 3:29 pm
Yes, you can change suitable gearbox.
But i dunno which gearbox can install in only.
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This shows how little you know about engines. Fuel is need to keep the engine alive when it is idle. You don't need fuel to keep the engine alive when it is driven by an external force.

On our car's ignition switch, there are 3 positions. First is OFF. Name me the other 2. If you don't know what they are, then there is no point continuing this discussion as you would not understand. Once you find out what they are, you would understand why I said that you don't need fuel to keep the engine alive.

Another hint.. Why can the car be pushed start when the battery is dead? There is no fuel in the engine and there is no battery to crank the starter but PRESTO... magically the car can start when it is pushed. If you get my hint, you would understand.


Added on August 1, 2008, 3:44 pm
QUOTE(Ultima @ Aug 1 2008, 03:34 PM)
so we can install gearbox diff from ours if compatible? no nid to change other things besides our gearbox only? so wat gearbox is suitable for this camtakpro engine besides wat we hav now la? sweat.gif
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The question now is what gearbox is the campro based on? I can't remember. I've lost track of Proton Campro developments as most parts are not related to Mitsu anymore.

It's always possible to change if it fits but why do you want to? Why change when there is nothing wrong with the gearbox?

This post has been edited by sleepwalker: Aug 1 2008, 03:44 PM
sleepwalker
post Aug 1 2008, 04:05 PM

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QUOTE(LeVis_Jeans @ Aug 1 2008, 03:48 PM)
Aiya i know that..
It use external force to turn on your engine.. but u forget after turn on the engine, the engine also need keep using fuel to keep alive.
You say down hill.. yes, engine still alive. But it will die when at flat road when u are no fuel !

Your example is use for battery dead. But when it push and get starter the car. you also need fuel..

No fuel go engine = engine dead.
Pls.... no engine will running will alive without fuel unless u force him by your self.  wink.gif
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You did not even read my reply properly. I said that there is no fuel used as you are going down hill until the idling controller takes over when the rpm is too low.

Once you hit flat road, the idling controller takes over and pumps fuel to keep the engine alive. While you are going down hill, fuel is not needed to keep the engine turning because it is being turned by the gearbox.
sleepwalker
post Aug 1 2008, 04:15 PM

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QUOTE(popnyat @ Aug 1 2008, 03:52 PM)
hahaha... engine still need fuel le.. its in idle even dragging by external force..  its preset by the fuel injector "engine management chip" and by manual twisting fuel screw beside my beloved bike carburetor..

no fuel engine mmg mati la.. hahaha.. internal combustion engine need momentum to stay continuous explosive..

penat engineer buat flywheel tu..
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Maybe I didn't make myself clear. Only engines with ECU will cut fuel to the engine when you are going down hill. Engine will not mati because your ignition is still in ON position. The spark plugs are still firing but there is no need for fuel as the engine has not mati yet because it is being driven by your gearbox.

If you are driving a car with ECU, here is a simple test you can do to. Rev your car on idle until 5000rpm. Let go of the throttle. As the RPM falls, there is actually no fuel going into the engine as the throttle body is closed and the rpm is driven by the spinning flywheel. Just as the RPM is about to drop to ZERO, the car engine suddenly shakes and RPM goes back up to 800-1000rpm (idling rpm). This is where the idling control valve takes over and pumps fuel into your engine to keep it alive.

IF you ever rev to 5000rpm and then turn off the engine, the RPM will not suddenly drop to zero, it will just fall like normal and if you turn on the engine (turn to postion ON (position 2), not ignition position (position 3)), the engine will come back to live again (if you can do it before the rpm drop to zero). You most probably won't understand what I'm talking about here. Some other would.. they might want to explain it better. What I'm trying to say is that your engine will not mati immediately when you turn off the fuel, as long as some else is turning the engine.
sleepwalker
post Aug 1 2008, 04:25 PM

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QUOTE(Ultima @ Aug 1 2008, 04:21 PM)
so if we off the engine at 5k rpm, it will make pop sound rite? like the mat rempit always do, rev hi then off engine, on it again, got pop sound tongue.gif

juz need a knowledge, no nid a car rite? whistling.gif tongue.gif
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Hahah.. the infamous carburator POP. This works only in carb engines as they don't have fuel injectors. Fuel is sucked into the engine by the vacuum, so they rev the engine and then turn off the ignition (no more spark from the sparkplug). Since the engine is still moving, it draws fuel into the combustion chamber from the carb and out into the enhaust. The moment you turn the igniton back on, the spark plugs fires and all the unburnt fuel explodes, giving you that POP sound macam gunshot.


Added on August 1, 2008, 4:27 pm
QUOTE(LeVis_Jeans @ Aug 1 2008, 04:23 PM)
U say no use fuel.  sweat.gif
But it still need use fuel to make it alive. But it auto control from valve only.

I told the guy is "fuel consume still maintain around RPM 1100 rate"
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Correct. So when people ask if engine braking at high rpm is wasting fuel or not, the answer is NO. Remember, the original question was about whether then engine use fuel while doing engine braking. Once you hit idling rpm, it is no longer engine braking and fuel will be required to keep the engine alive.

This post has been edited by sleepwalker: Aug 1 2008, 04:27 PM
sleepwalker
post Aug 1 2008, 04:35 PM

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QUOTE(Ultima @ Aug 1 2008, 04:30 PM)
so the pop sound only on carb? if efi no sound? dmn thts boring tongue.gif

but izzit harmful? damaged ur engine?
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Only carb. EFi ECU will not pump fuel once you turn off the ignition. No fuel will collect in the combustion chamber and exhaust. With such a big uncontrolled explosion in your engine and exhaust, what do you think? Harmful or not? I believe you can answer that question yourself.
sleepwalker
post Aug 1 2008, 06:11 PM

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QUOTE(b00n @ Aug 1 2008, 05:53 PM)
With turbo charging or forced induction the only difference is it will get you there much earlier. Nothing to do with RPMs.
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Ah.. yes.. "It's not how fast you can go but how quickly you can go fast" - quoted by Sleepwalker 1st August 2008 6:11pm... hahahahhaa..
sleepwalker
post Aug 1 2008, 06:46 PM

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QUOTE(alkt @ Aug 1 2008, 06:15 PM)
doh.gif
tonight how?
laugh.gif

my car is 110km/h at 3100 rpm sad.gif
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Tonight not free leh....

My car is 110km/h at 2700 rpm. tongue.gif


Added on August 1, 2008, 6:51 pm
QUOTE(imperialrealcs @ Aug 1 2008, 06:40 PM)
to all the pro, im a little dumb to comprehend all the super word here lol laugh.gif
so would like to ask..
if ori 13" rim can cover 1m per revolution
so a 15" can cover 1.15m per revolution correct?
that means in actual speed, taking 13" as relative figure
100km/h in 13" = 115km/h in 15" but the meter in 15" still showing 100km/h?
please dont bother about the actual figure, juz a sample
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Again, you are thinking about tyre. Speedometer takes the reading from gearbox, not the tyre. To the speedometer, your tyre only turned 1 revolution. It does not car how far you traveled because the calculation has been set by the manufacture to take the revolution of the tyre and calculate based on a preset of formula done by the manufacturer.

That is why when you change to a tyre that does not match your OEM overall diameter (OD), then your speedometer will no longer as accurate. The speedo will still show you the same speed (number of tyre revolutions still same) but you are traveling faster (if you have bigger tyres).

Understand now?

Edited: Going to use your formula..

if ori 13" rim can cover 1m per revolution
so a 15" can cover 1.15m per revolution correct?
-Correct but it is still 1 revolution of the tyre.

that means in actual speed, taking 13" as relative figure
100km/h in 13" = 115km/h in 15" but the meter in 15" still showing 100km/h?
please dont bother about the actual figure, juz a sample
-Correct because if it took 100 revolutions to reach 100km/h in 13 inch, it also takes 100 revolutions to reach 115km/h in 15".
-Your speedo is based on the 100 revolutions and not the distance.

-Understand now? (Ignore figures.. ahahha)

This post has been edited by sleepwalker: Aug 1 2008, 06:56 PM
sleepwalker
post Aug 1 2008, 07:35 PM

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QUOTE(imperialrealcs @ Aug 1 2008, 07:26 PM)
so where can i 're-calibrate' my speedo?
i changed to 4G92 MIVEC halfcut from Mirage Cyborg (or is it ASTI?)
anybody know what is the ori rim size?
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The difference would be so small that it would not matter. Furthermore, most Proton cars are based on the pre 96 Mitsu's and most likely use the similar tyre sizes. Even if there is a difference, it would be in the region of 1 to 2 percent. Not worth the effort.

 

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