Mitsubishi FTO Performance & Technical Information

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Power Graphs | Specification Data | Speed and Gearing | Octane Levels in Petrol
Torque and Horsepower explained | Rolling Roads

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If you're looking for something as simple as the engine output of the FTO range or maybe an in-depth explanation of how these figures come about, look no further! Go grab yourself a cup of tea and read on...


A comparison of the GPX and GR engines

This graph has been stolen from Richard Jenkins of FTO Derestricted (please visit his great site)

GR vs GPX
This is a plot of what Mitsubishi quote from the V6 engines. Note that the torque and power curves cross over themselves at 5,250rpm. For an explanation of this see below

The actual output of a GPX engine


This is an actual plot of the power output from my car. On February 24 2001 the UK FTO Owners Club visited the rolling road of Aldon Automotive in Brierly Hill. This plot was the best on the day with the flattest torque curve and the smoothest power line. Notice from the graph at the very top of this page that the curves from this graph follow very closely. In practive the torque curves on all the cars tested seem to tail off before Mitsubishi say they should.

According to Mitsubishi the MIVEC's peak torque should ocurr at 6,000rpm but see from my plot that peak torque is at a lower engine speed, 4,800rpm - probably brought about as a result of fitting the SuperChip. This gives better drivability and better acceleration.


This is me with the trophy for "Most Powerful Manual FTO"




The MIVEC V6 engine (GPX) The V6 engine (GR)
V6 Mivec engine V6 2.0 Engine
The 1.8 4-cylinder engine (GS)
1800 engine


FTO SPEC DATA
Running Type 2WD
Model Mitsubishi E-DE2A Mitsubishi E-DE3A
Type 1800 16V V6 2000 DOHC 24V V6 2000 MIVEC DOHC
GS GR GX SportsPackage GP Version-R GPX
HNUE HRUE HNHM HRHM HNXM HYXM HNFH3 HYFH3 HNGH HYGH
5M/T INVECS-II
SportsMode-4AT
5M/T INVECS-II
SportsMode-4AT
5M/T INVECS-II
SportsMode-5AT
5M/T INVECS-II
SportsMode-5AT
5M/T INVECS-II
SportsMode-5AT
*Performance
Minimum Turning Radius(m) 5.3
10.15 mode Petrol consumption
(km/l)
13.5 12.0 12.2 10.6 12.2 10.6 12.0 10.4 12.0 10.4
60km/h
(km/l)
22.0 20.5 20.9 19.0 20.9 19.9 20.5 19.7 20.5 19.7
*Engine
Engine Type 4G93 6A12
Valve System & Number of Cylinder SOHC16valve 4cylinders DOHC24valve V6
Size(mm) 81.0*89.0 78.4*69.0
Exhaust(cc) 1834 1998
Compression Ratio 9.5 10.0
PS/rpm 125/6000 180/7000 200/7500
Maximum Torque(kgf*m/rpm) 16.5/4500 19.5/4000 20.4/5000
Gas Capacity(l) 60
*Transmission Gear
Transmission Type Fwd 5speed Manual Fwd 4speed EUC Full Automatic Fwd 5speed Manual Fwd 4speed EUC Full Automatic Fwd 5speed Manual Fwd 5speed EUC Full Automatic Fwd 5speed Manual Fwd 5speed EUC Full Automatic Fwd 5speed Manual Fwd 5speed EUC Full Automatic
Gear Ratio 1speed 3.583 2.842 3.583 2.842 3.583 3.789 3.583 3.789 3.583 3.789
2speed 1.947 1.529 1.947 1.529 1.947 2.057 1.947 2.057 1.947 2.057
3speed 1.379 1.000 1.379 1.000 1.379 1.421 1.379 1.421 1.379 1.421
4speed 1.030 0.712 1.030 0.712 1.030 1.000 1.030 1.000 1.030 1.000
5speed 0.820 - 0.820 - 0.820 0.731 0.820 0.731 0.820 0.731
Reverse 3.363 2.480 3.363 2.480 3.363 3.865 3.363 3.865 3.363 3.865
Final Gear Ratio 4.312 4.626 4.312 4.407 4.312 3.735 4.312 3.735 4.312 3.735
*Running Gear
Steering Powered Steering
Suspension
Type
Front McPherson Strut
Rear Multi Link
Brake
Type
Front Ventilated Disc(14inch) Ventilated Disc(15inch)
Rear Solid Disc(14inch)
Camber Front 0°0'
Rear -1°0'
Toe-in Front 0mm
Rear 3mm
Caster Front 2°50'
Wheel offsets Width 6.5 Offset +20mm to +50mm (reg.*+38mm)
Width 7.0 Offset +25mmto +45mm
Width 7.5 Offset +30mm to +39mm
Width 8.0 Offset +35mm
Tyres (Standard) 185/70R14 88S 195/60R15 88H 205/50R16 87V

Speed in a selected gear, 5 speed manual gearbox

1st Gear
2nd Gear
3rd Gear
4th Gear
5th Gear
2k rpm
10mph
17mph
24mph
32mph
40mph
3k rpm
14mph
25mph
36mph
48mph
60mph
4k rpm
19mph
33mph
48mph
64mph
80mph
5k rpm
22mph
42mph
60mph
80mph
100mph
6k rpm
27mph
50mph
71mph
96mph
120mph
7k rpm
32mph
59mph
79mph
112mph
140mph
8k rpm
36mph
67mph
88mph
128mph
160mph

The above table and graph shows exactly how fast the FTO will go in a certain gear (manual gearbox). The figures in bold are actual readings which were taken electonically (not by using the rev counter or speedo) for greater accuracy. The wheel and tyre combination used was 215x40R17 which will give a +1.243% error reading.

The maximum speed that the FTO will ever reach is around 158mph which is on the rev limiter in 5th gear (of course it is unlikely that the FTO will attain this maximum speed - it's actual limit is around 140mph-145mph oweing to air and rolling resistance). Note - I found the FTO to limit the engine rpm at approximately 8,050rpm. This is an accurate figure which was taken electronically.

Tyre Size
Side Wall Height (mm)
Tyre Radius
Actual Speed (@70)
Percent
Error
195/60R15
117.0

307.5

70
0% - GR std
205/50R16
102.5
305.7
70
0% - GPX std
215/45R17
96.75
312.65
71.59
-2.273%
215/40R17
86.0
301.9
69.13
+1.243%

Thanks to Richard Jenkins for posting this information from the MR2 wehsite's calculator.

You can work this out! Vehicle speed in a particular gear is exactly linear to rpm. Maybe you'll go very slightly faster than linear at higher speeds due to balooning of the tyres, but that will be a very tiny effect.


A note about octane levels in petrol

The question is, should you always use Super-Unleaded? Could it make a difference? Should we try some petrol additives (ie. octane booster etc.)?

The definition of octane is "a numerical designation given to a fuel to express its ability to resist Detonation". That's it. No performance increases from a common misconception of a "bigger bang".

During the compression stroke, fuel and air are compressed rapidly and as they compress, the mixture heats up but this is usually not a problem. At TDC or just before it on most cars, the spark plug fires and the mixture is ignited, the fuel catches fire and begins to "burn very rapidly". Petrol does NOT explode in a combustion engine. As the "flame front" begins to travel away from the plug, the fuel air mixture at the far ends of the combustion chamber are compressed even higher and so begin to heat up even more. If the fuel being used does not have a octane rating high enough then the heat generated by this compression can cause the fuel to reach its flash point and ignite before the flame front reaches it. Now we have two flame fronts traveling across the combustion chamber in opposite directions and when they meet the the resultant crash is almost as explosive. THIS is Detonation. The sound you hear is the cylinder walls and head ringing from the pressure waves and the damage to an engine can be serious. So if a fuel can hold out against the heat generated by the oncomming flame front without self igniting the octane number is high enough. Turbo and high compression engines aggravate this by cramming more fuel and air into the cylinder at a given time and so raising the combustion chamber temperature more than other engines. Thus their need for fuels with higher octane and a high resistence to detonation.

The only reason that high-performance cars with normally-aspirated engines benefit from Super unleaded (higher octane petrol) is that the car is able to advance the ignition timing slightly (this is done automatically) with a recuced risk of detonation (pinking). Also you may notice a slight improvement in your fuel economy and sometimes the quality of petrol is better.

If you fit a device that modifes the timing (such as a Superchip or different ECU without a 95-octane map) then running a higher octane petrol is a must. Normally unmodified & non-turbo cars can happily run on standard good quality unleaded petrol. I hope this clears up a few rumors.


The relationship between torque and horsepower
Tech-heads only - get yourself a cup of tea, this is a biggie!

There's been a certain amount of discussion, in this and other files, about the concepts of horsepower and torque, how they relate to each other, and how they apply in terms of engine performance. I have observed that, although nearly everyone participating has a passion for cars, there is a huge variance in knowledge. It's clear that a bunch of folks have strong opinions (about this topic, and other things), but that has generally led to more heat than light, if you get my drift :-). I felt it deserved to be dealt with as a separate topic.

Here's the deal, in moderately plain english.
Force, Work and Time - If you have a one pound weight bolted to the floor, and try to lift it with one pound of force (or 10, or 50 pounds), you will have applied force and exerted energy, but no work will have been done. If you unbolt the weight, and apply a force sufficient to lift the weight one foot, then one foot pound of work will have been done. If that event takes a minute to accomplish, then you will be doing work at the rate of one foot pound per minute. If it takes one second to accomplish the task, then work will be done at the rate of 60 foot pounds per minute, and so on. In order to apply these measurements to cars and their performance (whether you're speaking of torque, horsepower, newton meters, watts, or any other terms), you need to address the three variables of force, work and time.

A while back, a gentleman by the name of Watt (the same gent who did all that neat stuff with steam engines) made some observations, and concluded that the average horse of the time could lift a 550 pound weight one foot in one second, thereby performing work at the rate of 550 foot pounds per second, or 33,000 foot pounds per minute, for an eight hour shift, more or less. He then published those observations, and stated that 33,000 foot pounds per minute of work was equivalent to the power of one horse, or, one horsepower. Everybody else said OK. :-) For purposes of this discussion, we need to measure units of force from rotating objects such as crankshafts, so we'll use terms which define a twisting force, such as foot pounds of torque. A foot pound of torque is the twisting force necessary to support a one pound weight on a weightless horizontal bar, one foot from the fulcrum. Now, it's important to understand that nobody on the planet ever actually measures horsepower from a running engine. What we actually measure (on a dynomometer) is torque, expressed in foot pounds (in the U.S.), and then we calculate actual horsepower by converting the twisting force of torque into the work units of horsepower.

A maths bit:
Visualize that one pound weight we mentioned, one foot from the fulcrum on its weightless bar. If we rotate that weight for one full revolution against a one pound resistance, we have moved it a total of 6.2832 feet (Pi * a two foot circle), and, incidently, we have done 6.2832 foot pounds of work. OK. Remember Watt? He said that 33,000 foot pounds of work per minute was equivalent to one horsepower. If we divide the 6.2832 foot pounds of work we've done per revolution of that weight into 33,000 foot pounds, we come up with the fact that one foot pound of torque at 5252 rpm is equal to 33,000 foot pounds per minute of work, and is the equivalent of one horsepower. If we only move that weight at the rate of 2626 rpm, it's the equivalent of 1/2 horsepower (16,500 foot pounds per minute), and so on. Therefore, the following formula applies for calculating horsepower from a torque measurement: Torque x RPM over Horsepower = 5252 This is not a debatable item. It's the way it's done. Period.

The Case For Torque Now, what does all this mean in carland? First of all, from a driver's perspective, torque, to use the vernacular, RULES. Any given car, in any given gear, will accelerate at a rate which exactly matches its torque curve (allowing for increased air and rolling resistance as speeds climb). Another way of saying this is that a car will accelerate hardest at its torque peak in any given gear, and will not accelerate as hard below that peak, or above it. Torque is the only thing that a driver feels, and horsepower is just sort of an esoteric measurement in that context. 300 foot pounds of torque will accelerate you just as hard at 2000 rpm as it would if you were making that torque at 4000 rpm in the same gear, yet, per the formula, the horsepower would be double at 4000 rpm. Therefore, horsepower isn't particularly meaningful from a driver's perspective, and the two numbers only get friendly at 5252 rpm, where horsepower and torque always come out the same. In contrast to a torque curve (and the matching pushback into your seat), horsepower rises rapidly with rpm, especially when torque values are also climbing. Horsepower will continue to climb, however, until well past the torque peak, and will continue to rise as engine speed climbs, until the torque curve really begins to plummet, faster than engine rpm is rising. However, as I said, horsepower has nothing to do with what a driver feels.

You don't believe all this? Fine. Take your non turbo car (turbo lag muddles the results) to its torque peak in first gear, and punch it. Notice the belt in the back? Now take it to the power peak, and punch it. Notice that the belt in the back is a bit weaker? Fine. Can we go on, now? :-) The Case For Horsepower OK. If torque is so all-fired important, why do we care about horsepower? Because (to quote a friend), "It is better to make torque at high rpm than at low rpm, because you can take advantage of gearing". For an extreme example of this, I'll leave carland for a moment, and describe a waterwheel I got to watch awhile ago. This was a pretty massive wheel (built a couple of hundred years ago), rotating lazily on a shaft which was connected to the works inside a flour mill. Working some things out from what the people in the mill said, I was able to determine that the wheel typically generated about 2,600(!) foot pounds of torque. I had clocked its speed, and determined that it was rotating at about 12 rpm. If we hooked that wheel to, say, the drivewheels of a car, that car would go from zero to twelve rpm in a flash, and the waterwheel would hardly notice :-). On the other hand, twelve rpm of the drivewheels is around one mph for the average car, and, in order to go faster, we'd need to gear it up. To get to 60 mph would require gearing the wheel up enough so that it would be effectively making a little over 43 foot pounds of torque at the output, which is not only a relatively small amount, it's less than what the average car would need in order to actually get to 60. Applying the conversion formula gives us the facts on this. 12 x 2,600 over 5,252 gives us: 6 HP. Oops. Now we see the rest of the story. While it's clearly true that the water wheel can exert a bunch of force, its power (ability to do work over time) is severely limited.

Back to carland, and some examples of how horsepower makes a major difference in how fast a car can accelerate, in spite of what torque on your backside tells you :-). A very good example would be to compare the current LT1 Corvette with the last of the L98 Vettes, built in 1991.
Figures as follows:

Engine Peak HP @ RPM Peak Torque @ RPM
L98 250 @ 4000 340 @ 3200
LT1 300 @ 5000 340 @ 3600


The cars are geared identically, and car weights are within a few pounds, so it's a good comparison. First, each car will push you back in the seat (the fun factor) with the same authority - at least at or near peak torque in each gear. One will tend to feel about as fast as the other to the driver, but the LT1 will actually be significantly faster than the L98, even though it won't pull any harder.

If we mess about with the formula, we can begin to discover exactly *why* the LT1 is faster. Here's another slice at that formula: Horsepower x 5252 over Torque = RPM. If we plug some numbers in, we can see that the L98 is making 328 foot pounds of torque at its power peak (250 hp @ 4000), and we can infer that it cannot be making any more than 263 pound feet of torque at 5000 rpm, or it would be making more than 250 hp at that engine speed, and would be so rated. In actuality, the L98 is probably making no more than around 210 pound feet or so at 5000 rpm, and anybody who owns one would shift it at around 46-4700 rpm, because more torque is available at the drive wheels in the next gear at that point. On the other hand, the LT1 is fairly happy making 315 pound feet at 5000 rpm, and is happy right up to its mid 5s redline. So, in a drag race, the cars would launch more or less together. The L98 might have a slight advantage due to its peak torque occuring a little earlier in the rev range, but that is debatable, since the LT1 has a wider, flatter curve (again pretty much by definition, looking at the figures). From somewhere in the mid range and up, however, the LT1 would begin to pull away. Where the L98 has to shift to second (and throw away torque multiplication for speed), the LT1 still has around another 1000 rpm to go in first, and thus begins to widen its lead, more and more as the speeds climb. As long as the revs are high, the LT1, by definition, has an advantage.

Another example would be the LT1 against the ZR-1. Same deal, only in reverse. The ZR-1 actually pulls a little harder than the LT1, although its torque advantage is softened somewhat by its extra weight. The real advantage, however, is that the ZR-1 has another 1500 rpm in hand at the point where the LT1 has to shift. There are numerous examples of this phenomenon. The Integra GS-R, for instance, is faster than the garden variety Integra, not because it pulls particularly harder (it doesn't), but because it pulls *longer*. It doesn't feel particularly faster, but it is.

A final example of this requires your imagination. Figure that we can tweak an LT1 engine so that it still makes peak torque of 340 foot pounds at 3600 rpm, but, instead of the curve dropping off to 315 pound feet at 5000, we extend the torque curve so much that it doesn't fall off to 315 pound feet until 15000 rpm. OK, so we'd need to have virtually all the moving parts made out of unobtanium :-), and some sort of turbocharging on demand that would make enough high-rpm boost to keep the curve from falling, but hey, bear with me. If you raced a stock LT1 with this car, they would launch together, but, somewhere around the 60 foot point, the stocker would begin to fade, and would have to grab second gear shortly thereafter. Not long after that, you'd see in your mirror that the stocker has grabbed third, and not too long after that, it would get fourth, but you'd wouldn't be able to see that due to the distance between you as you crossed the line, still in first gear, and pulling like crazy. I've got a computer simulation that models an LT1 Vette in a quarter mile pass, and it predicts a 13.38 second ET, at 104.5 mph. That's pretty close (actually a tiny bit conservative) to what a stock LT1 can do at 100% air density at a high traction drag strip, being powershifted. However, our modified car, while belting the driver in the back no harder than the stocker (at peak torque) does an 11.96, at 135.1 mph, all in first gear, of course. It doesn't pull any harder, but it sure as hell pulls longer :-). It's also making 900hp, at 15,000 rpm. Of course, folks who are knowledgeable about drag racing are now openly snickering, because they've read the preceeding paragraph, and it occurs to them that any self respecting car that can get to 135 mph in a quarter mile will just naturally be doing this in less than ten seconds. Of course that's true, but I remind these same folks that any self-respecting engine that propels a Vette into the nines is also making a whole bunch more than 340 foot pounds of torque.

That does bring up another point, though. Essentially, a more "real" Corvette running 135 mph in a quarter mile (maybe a mega big block) might be making 700-800 foot pounds of torque, and thus it would pull a whole bunch harder than my paper tiger would. It would need slicks and other modifications in order to turn that torque into forward motion, but it would also get from here to way over there a bunch quicker. On the other hand, as long as we're making quarter mile passes with fantasy engines, if we put a 10.35:1 final-drive gear (3.45 is stock) in our fantasy LT1, with slicks and other chassis mods, we'd be in the nines just as easily as the big block would, and thus save face :-). The mechanical advantage of such a nonsensical rear gear would allow our combination to pull just as hard as the big block, plus we'd get to do all that gear banging and such that real racers do, and finish in fourth gear, as God intends. :-) The only modification to the preceeding paragraph would be the polar moments of inertia (flywheel effect) argument brought about by such a stiff rear gear, and that argument is outside of the scope of this already massive document. Another time, maybe, if you can stand it :-).

At The Bonneville Salt Flats, Looking at top speed, horsepower wins again, in the sense that making more torque at high rpm means you can use a stiffer gear for any given car speed, and thus have more effective torque at the drive wheels. Finally, operating at the power peak means you are doing the absolute best you can at any given car speed, measuring torque at the drive wheels. I know I said that acceleration follows the torque curve in any given gear, but if you factor in gearing vs car speed, the power peak is it.

An example, yet again, The LT1 Vette will illustrate this. If you take it up to its torque peak (3600 rpm) in a gear, it will generate some level of torque (340 foot pounds times whatever overall gearing) at the drive wheels, which is the best it will do in that gear (meaning, that's where it is pulling hardest in that gear). However, if you re-gear the car so it is operating at the power peak (5000 rpm) at the same car speed, it will deliver more torque to the drive wheels, because you'll need to gear it up by nearly 39% (5000/3600), while engine torque has only dropped by a little over 7% (315/340). You'll net a 29% gain in drive wheel torque at the power peak vs the torque peak, at a given car speed. Any other rpm (other than the power peak) at a given car speed will net you a lower torque value at the drive wheels. This would be true of any car on the planet, so, theoretical "best" top speed will always occur when a given vehicle is operating at its power peak.

For the final-final point (Really, I Promise), what if we ditched that water wheel, and bolted an LT1 in its place? Now, no LT1 is going to be making over 2600 foot pounds of torque (except possibly for a single, glorious instant, running on nitromethane), but assuming we needed 12 rpm for an input to the mill, we could run the LT1 at 5000 rpm (where it's making 315 foot pounds of torque), and gear it down to a 12 rpm output. Result? We'd have over 131,000 foot pounds of torque to play with. We could probably twist the whole flour mill around the input shaft, if we needed to :-). The Only Thing You Really Need to Know Repeat after me. "It is better to make torque at high rpm than at low rpm, because you can take advantage of gearing" :-)

Torque and Horsepower - From Bruce Augenstein, rba@augenstein.ultranet.com


A word on Rolling Roads or "Chassis Dynometer's".

The car is driven onto a set of rollers so that the driving tyres are resting between two steel cylinders. The torque is measured at different speeds at the wheels. The same equation in the part above about torque / bhp can be used to calculate bhp at the rollers by knowing the torque and the rpm of the rollers. If the engine rpm is measured simultaneously then we can know roller speed at a particular engine speed. The BIG problem is that there is a possibility of tyre slip is taking place. Remember these are smooth steel rollers which over time get quite polished. As the effects of tyre slip are complex we'll not go into them here but what I do know is that you can get some really strange bhp figures from highly tuned engines on narrow tyres and the readings are invariably too high not too low.

 

 

What is transmission loss?
Well all mechanical systems suffer from friction and a proportion of the power fed into a system will get dissipated by friction and turn into heat and noise. Note the key phrase there - "power fed into a system". For there to be a loss there must be an input - simple and obvious yes but we'll see the relevance in a minute. When your car is parked overnight with the engine switched off, the transmission losses are obviously zero. When the car is running then some proportion of the flywheel power will be lost in the gearbox, final drive, drive shaft bearings, wheel bearings and tyres. For a given mechanical system these losses will usually stay close to a particular fixed percentage, let's say 10% for example, of the input power. So if the car is cruising and developing 20 bhp then 2 bhp will get absorbed as friction - under full power, say 100 bhp, then maybe 10 bhp will get absorbed. Now it is true that not every component in a transmission system absorbs a fixed percentage of the input power. Some components like oil seals and non driven meshed gears (as in a normal car multi speed gearbox) have frictional losses which are not affected by the input torque. These losses do increase with speed of course but at a given rpm can be taken to remain constant even if the engine is tuned to give more power. Finally, the biggest source of loss in the entire transmission system of a car is in the tyres - they account for half or more of the total losses between the flywheel and the rollers. Each set of driven gears, i.e. the final drive gear or the particular gearbox ratio that you happen to be testing the car in, only absorbs about 1% to 2% of the engine's power. Ok - so how do these software systems that supposedly measure transmission losses so as to "predict" back to the flywheel bhp work. The power curve at the wheels is taken in the usual way as explained above. Then, at peak rpm, the operator puts the car into neutral and lets the rollers slow down under the drag of the tyres and transmission. The software then measures this drag (or "coast down loss") as "negative" power and adds it to the wheel power to get back to the supposed flywheel power. BUT - and hopefully you've all spotted the problem now - the engine is not feeding any power into the drivetrain while the car is in neutral - in fact it isn't even connected to the drivetrain any more!! Whatever drag this is that's being measured it has nothing at all to do with the proportion of the flywheel power that gets lost as friction when the engine is powering the car in the normal way. The engine could now be an 800 bhp F1 engine or a 30 bhp mini engine for all it matters because it isn't connected to the gearbox or feeding any power into it. Obviously this "coast down loss" is something to do with the transmission and tyres but it is not the true transmission loss - in fact this coast down loss should never be expected to change for a given car at a particular rpm regardless of how much you tune the engine whereas a true transmission loss will increase as the engine power increases because it is dependent to a large extent on the amount of power being fed into the transmission. As the engine was tuned to give more power the "true" transmission losses must have also increased to some extent but these chassis dyno systems don't, and can't, show this happening.
So is there any way of really measuring the true transmission loss of a car?
Yes - only one - by measuring the flywheel power on an accurate engine dyno, the wheel power on an accurate chassis dyno and taking one away from the other. There is no way of finding out the true transmission loss just by measuring the power at the wheels. So hopefully that's got you all thinking a bit more now instead of just taking for granted the "flywheel" figure you were given last time you took your car to the rollers. Even worse is the fact that some of these software systems allow the operator to just programme in the percentage of transmission loss he wants the system to add to the wheel figures. So if that isn't a nice easy way to show some big fat flywheel bhp then I don't know of a better one. It's certainly a lot easier than actually doing some proper development work to make the engine perform better - just dial in a bigger transmission loss and there you go - the same wheel bhp now turns into a bigger flywheel bhp - happy customer, happy dyno man - just a shame it was all sleight of hand. See the end of this article if you doubt that this sort of thing really happens.
So what should you do when you take your car to a rolling road?
Firstly, make sure you get printouts that show the wheel bhp and not just the flywheel bhp. Then at least you can see if they look sensible in comparison. If you have a desperate need to know the flywheel bhp then you will have to estimate it - there's no other way short of using an engine dyno. The corrections you need to make for cars with manual gearboxes are these: The average front wheel drive road car with between 100 and 200 bhp loses about 15% of the engine bhp as transmission losses. The average rear wheel drive road car with between 100 and 200 bhp loses about 17% of the engine bhp as transmission losses. The increase in % loss over front wheel drive is because the differential has to turn the drive through 90 degrees at the back axle which soaks up a bit more of the engine's power. 4wd cars will have higher losses because of the extra differentials and other power transmission components. A reasonable estimate of an average 4wd car's losses might be 22% to 25% of the flywheel power but it isn't a subject I have sufficient data on to be definitive. What your own specific car loses is anyone's guess - yours is as good as mine - but it shouldn't be far from the figures above. For sure though, no car in the world, unless it has flat tyres and a gearbox full of sand, loses anything like 30% of the engine's power in the transmission and tyres as many rolling road operators would try to have you believe. So take the wheel figure and divide by 0.85 for FWD or 0.83 for RWD and that will get you as close to the true engine bhp as you are ever going to know. In general though it is fair to say that low powered cars have higher % losses than high powered cars. For example, a 60 bhp Fiesta will have around 14 to 15 bhp total transmission and tyre loss whereas a 90 bhp XR2 will only have about 17 to 18 bhp loss - a smaller % obviously. By the time you get to RWD cars with engines in the 300 to 500+ bhp range, losses can eventually drop to as little as 12 to 14% or so. Another rule of thumb I use which is quite accurate is to treat the losses as being 10% of the flywheel power plus 10 bhp for FWD and 12% plus 10 bhp for RWD cars. This equation "loads" low powered cars more than high powered cars which is more closely like what happens in reality. Remember, these percentages are not "gospel" - they are good realistic averages.

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The V6 MIVEC engine

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