That’s the best bit of info I’ve seen on the VHPD! Nice one Rox.
So theory goes that when you change as long as you don’t drop below 5500rpm (max torque) then you’ll be OK?
Also intersting they specify 0w40 oil… I alwasy thought it wanted higher high temp viscosities like 10w60 or something…
Have to agree that sometimes changing sooner does help, was at the track on wednesday and exiting a sweeper onto an uphill section i found the best results shifting at +/- 7500 as it dropped the revs back into the the torquier band going up the hill and you could actually feel the car strugling for the last few hundred rpm, on the flat stuff depending on wether you have a close ratio box or not it is propably better to try and get it quite close to red line as you would drop into a higher torque band, theoretically , had my car mapped on monday when they fitted the vernier pulleys i will graph the torque curve this evening but a quick glance reveals virtually the same torque within 2nm between 5000 and 6000 which would make the drop in revs from the ucr box spot on changing at 7800, dropping it right in the max torque range.
As an aside my sister hits the limiter about 217 times per lap so a shift light does help when you are in the thick of things concentrating on catching the car in front of you as hitting the limiter on lets say 6 gearchanges for 1/2 a second costs you 3 seconds a lap, whereas perhaps shifting 200 rpm to early could not cost nearly as much time.
As an aside my sister hits the limiter about 217 times per lap
PMSL!!! Classic!
Mark, But thats not the engine graph of the Exige 190, Lotus only have 127 Ftlbs of torque
Okay, picture the scenes:
It’s a gorgeous day in Anglesey, little fluffy white clouds hang in a sunny blue sky. It’s mid morning and you’re back in the groove of the smashing little circuit. You come around the flowing complex of bends that leads to the start finish and the revs build in third, a thrilling engine scream building to a crescendo…na-na-na-na-na - BUGGER! Hit the limiter, up to third with a frown. Next couple of bends effected by the thought of the little bit of damage you may have just caused your engine.
It’s a gorgeous day in Anglesey, little fluffy white clouds hang in a sunny blue sky. It’s mid morning and you’re back in the groove of the smashing little circuit. You come around the flowing complex of bends that leads to the start finish and the revs build in third, a thrilling engine scream building to a crescendo, subtitled by those little lights posh race cars on the tele have…2nd green…amber…RED…change up! Glance over at the pit wall and give Pesky the thumbs-up, check the right hand wing mirror for a fast approaching Uldis , brake late for turn 1, slight slide, trail brake into 2, hang the back end out…MAGIC!
I know my favourite ending!
Ian
Link doesn’t seem to work?
link okay for me IDG
And for me now.
Thanks Jason.
Ian
Jason,
That only works out at 120 Ft Lbs
Here is mine…
Although its nowhere near that now
Okay, picture the scenes:
It’s a gorgeous day in Anglesey, little fluffy white clouds hang in a sunny blue sky. It’s mid morning and you’re back in the groove of the smashing little circuit. You come around the flowing complex of bends that leads to the start finish and the revs build in third, a thrilling engine scream building to a crescendo…na-na-na-na-na - BUGGER! Hit the limiter, up to third with a frown. Next couple of bends effected by the thought of the little bit of damage you may have just caused your engine.
It’s a gorgeous day in Anglesey, little fluffy white clouds hang in a sunny blue sky. It’s mid morning and you’re back in the groove of the smashing little circuit. You come around the flowing complex of bends that leads to the start finish and the revs build in third, a thrilling engine scream building to a crescendo, subtitled by those little lights posh race cars on the tele have…2nd green…amber…RED…change up! Glance over at the pit wall and give Pesky the thumbs-up, check the right hand wing mirror for a fast approaching Uldis , brake late for turn 1, slight slide, trail brake into 2, hang the back end out…MAGIC!
I know my favourite ending!
Ian
I like the picture.
Uldis comes on charging, sporting a new (although unneeded) shiftlight in his dashboard.
…Ian brakes late, foreseeing Uldis possible brave late braking maneouver as well, but is suddenly surprised seeing that as he brakes…
…Uldis flies by without even braking!
He looks as if he couldn’t possibly make it and will soon dissapear in the sea, but somehow deifes physics and stays in a perfeclty logical but seemingly impossible line, and fast approaches the outside apex, Ian now stuck like glue to Uldis rear, both cars braking at the same point on a synchronized swim-like choreography.
They enter together the next right hander, both cars drifting slightly whilst Uldis starts distancing slowly, starting acceleration impossibly early…
Ian/Uldis
Jason,
That only works out at 120 Ft Lbs
Phil, i have spent some time on your site, top pics and info. And must admit i was slightly dissapointed but the dyno it was on is renowned as being ultra conservative, so i am not very concerned about the figures, as for altitude the figures are not to bad. I am busy deciding what to do about the head as the m/sport head was really so much better at the top it’s unbeleivable.
Uldis, you forgot to mention the 36-20-36 blonde in a bikini marshalling at Radar!
Changing at 7700 drops to about 5800, so I’ll try an acceleration test (with the AP-22), when I can be bothered, changing at 7700 and 7000 and see what gives.
Ian
Uldis, you forgot to mention the 36-20-36 blonde in a bikini marshalling at Radar!
Ok, that’s me pulling over at radar then…
Can i add my thoughts to this discussion ?
…Brendan, i’m not sure i agree this… it will depend on what you are wanting (speed or acceleration). As Uldis said above, maximum acceleration will be achieved at Peak Torque… but this is true IN ANY GEAR. Also torque is a function of revs and horsepower, so the way i see it gearing won’t actually make any difference to the shape of an engines torque/power curves…
Rox, it took me a long time to really get my head around this, but I think I now have a fairly good understanding of the subject. You’re nearly right. Peak torque is where you get maximum acceleration in each gear, but you must remember that the gearbox is a torque multiplyer. The torque at the wheels is engine torque multiplied by the gear ratio. If you’re at peak engine torque, you’re getting the best out of the current gear, but selecting a lower gear may well increase the torque at the wheels, and therefore, your acceleration.
For example, take a look at Phil’s graph above.
His peak torque looks to be roughly 146 lb ft @ 6240 rpm.
Lets imagine we’re running at that engine speed (6240rpm) in fifth. Would we accelerate faster if we dropped down to fourth?
We have the gear ratios for the standard exige box:
4th = 1.033
5th = 0.848
final drive = 4.214
Multiply the ratios by the final drive to get the true gearing.
4th = 1.033 * 4.214 = 4.353
5th = 0.848 * 4.214 = 3.573
If we’re in 5th gear at 6240rpm, we can calculate the new engine speed for the drop to 4th gear thusly:
(revs * new ratio / current ratio)
6240 * 4.353 / 3.573 = 7601 rpm (a bit high, but this is just an example. Bear with me )
Referring to the graph again, we can see that Phil’s engine seems to produce about 138 lb feet of torque at 7601 rpm.
Now we can compare the torque at the wheels for each case.
Wheel torque is engine torque multiplied by the gear ratio:
5th gear:
Engine torque is 146, ratio is 3.573
Torque at wheels = 146 * 3.573 = 516.4
4th gear:
Engine torque is 138, ratio is 4.353
Torque at wheels = 138 * 4.353 = 600.7!
Result? Fourth gear is better at this speed than fifth even though you’re getting less engine torque.
This means that in fourth gear, you don’t want to change up at the point where you will drop onto the torque peak, you’ll need to rev it up a bit further before selecting fifth.
When accelerating in a straight line in this car, you will probably never want to use the peak engine torque, you should always keep the revs as high as possible.
However, corners are a different matter. sometimes, using a higher gear out of a corner might reduce the acceleration fractionally, but will eliminate the need for a time sapping gear change.
Blime Brendan! You’re clearly as thorough over maths as you are when painting model Exiges!
And yippee, my shift light is back in play as a useful as well as cool tool.
I await further debate.
Ian
ps. I’m not ignoring the corners points either (which I was already aware of).
Look, can we forget about the models now, please
I must admit I’d quite like a shift light in my car. Just for the cool gadget factor
I had to get thorough with the maths in order to get my head around the subject. For years I wanted to really understand the difference between power and torque, and their relevance. Nobody seemed able to explain it to me, so I had to work it all out for myself.
Brendan,
I’d say you’re right on your calculations there, but you’re forgetting the fact that although a lower gear will give you better acceleration (and that can hardly be disputed, seat of the pants will confirm), the lower gear will only take you so far, you’ll hit redline!
There is no other option but to change gears. So now we only have to select where.
And this could be when on the next gear you have the highest torque, or when the track layout will let you.
Like mentioned above, there will be cases when you NEED to shortshift, and some cases when you’ll just prefer to hold on the low gear for a fraction longer.
But I say, to achieve the best acceleration, you don’t NEED to hit redline everythiime.
On our cars, as mentioned above, I agree, this tends to be up there, between 7.2K and 8K, depends on the engine.
I’ve experienced needing to shift in my engine anything from 7.2 (bone stock) to 8K later tune with all steps in between.
So there you go, depends on your car
