rev limiter / shift light / ATTENTION pod boys maybe?

[mikeoxford]

Right. 8)

people from experience or with wise knowledge required :P

My maximum BHP is at 6158 RPM
My maximum lbft torque is at 4375 RPM and continues steadily in a straight line until the BHP drops off.

My BHP and torque curve cross at 5250 RPM

where do i set the rev limiter? and where do i want to shift / change gear?

the rev limiter and shift light can be incremented every 100 RPM

as standard the rev limiter and shift light are 500 RPM apart, for example rev limiter is at 6000 RPM and shift point is 5,500 RPM

There is a soft cut rev limit function also (BUT IS NOT PROGRAMMABLE - this kicks in 200 RPM before the hard cut)

my perception of it.....

i set the rev limiter to 6600 RPM
this will automatically set my shift point at 6100RPM

have i understood correctly? (i change on peak BHP power? and take no notice of torque?)

[Ste_Nova]

no cause it will drop you much lower down the power band...

on mig it was decided that on a standard xe you needed to change right on the limiter!

[mikeoxford]

no cause it will drop you much lower down the power band...

on mig it was decided that on a standard xe you needed to change right on the limiter!

so you would suggest raising all the limits and shift points?

or making the gap between shift light and rev limiter smaller?

dont forget i propse to set the limiter higher than peak power....

[loggyboy]

My understanding of it is this..
each time u change gear the revs decrease by a certain amount (dictated by the gear ratios) this is likely to be about 1000-1500 revs depending on the gear.
ie if u change at 5000 revs from 2nd to 3rd ur revs would drop to 3500, or if u got from 4th to 5th at 5000 it may go down to 4000 revs.
this range is the range u should be aiming to use. So you want the middle of the range to be (and this is where my knowlege runs short) wither where ur peak crosssover is or where there is most power and torque combined.
with the figures u qouted id set it limit at 6500 therefore change at 6000 and ur 'range' being 4500-6000 revs there for slap in ur best area

ps all above revs and ranges are estimates only and not based on anythin but the weird shit in my head! lol

[mikeyredtop]

its not an xe its a 1.6t40 with cr f13 and 4.18 diff, use one off them gear ratio sites to work out where in ur power band u will be droppin to as if u drop too far down the rev range then u need diffrent ratios...or a higher rpm shift

[Dan]

hmmmmm, i went through all this rubbish last year as some of you know. and still didnt suss it tbh, i set it at a certain rpm and had limiter at 7k blah blah. When on pod the car felt good, so i continued through my shift light on every gear and ignored it completely and just drove it by feel on all three runs :lol: .

I think the best advice is, you know what the car feels like and can tell when its starting to drop off etc. Set it to how you feel the car is at its best.

obv alot will disagree but thats my way of doing it lol :P .

[Snowface]

where bouts did you put your shiflt light mike? Inside your clocks somehow? or somewhere on the dash?

[CP]

Set your rev limiter to what you expect is the max safe working range of your engine - prob around 6500 - 7000 k.

Set your shift light according to feel - you will know when the car has stopped pulling and needs to change. In any event it needs to be way above max power / torque outputs cos as others have mentioned you lose revs on a gear change. You will find that the engine still pulls well after max power cos the figures dont fall away that quickly.

[mikeoxford]

having closely examined my rrgraph, and played with aragorns spreadsheet. i have come up with a number of issues as charles, quite rightly (and others) pointed out

if i change everytime on the shift light at 6200 RPM

from 1st -> 2nd my RPM will be just short of 4k
from 2nd -> 3rd my RPM will be just over 4k
from 3rd -> 4th my RPM will be 4.5k
from 4th - > 5th my rpm will be 5k

as i said before, my torque curve peaks at 4375 RPM

from about 4k -> 6k my torque curve is pretty much horizontal :!:

and from 6k RPM my BHP curve is pretty much horizontal :!:

my plan....

rev limit at 6500 (which limits my top speed to 113.89 MPH :o )

and shift light at 6200 RPM

for anyone intrested they can examine my graph and advise me on the following link, selecting mike oxford, 138 bhp graph at the bottom.

http://www.totalwebsystems.co.uk/webspace/rrgraphs

looking at the graph what ive outlined above makes most sense to me.... probly not right though :lol:


Set your rev limiter to what you expect is the max safe working range of your engine - prob around 6500 - 7000 k.

Set your shift light according to feel - you will know when the car has stopped pulling and needs to change. In any event it needs to be way above max power / torque outputs cos as others have mentioned you lose revs on a gear change. You will find that the engine still pulls well after max power cos the figures dont fall away that quickly.

[peester]

When on pod the car felt good, so i continued through my shift light on every gear and ignored it completely and just drove it by feel on all three runs :lol: .

I think the best advice is, you know what the car feels like and can tell when its starting to drop off etc. Set it to how you feel the car is at its best.

obv alot will disagree but thats my way of doing it lol :P .

i agree mate; who needs driver aids? guts.

[Jim]

The real driver doesn't need poxy shift lights and rev limiters. You should know when to change gear ;)

Jim

[MC]

I agree, and to be harsh, if you need to ask when is best to change gear, you'll probably never get it spot on.

You have to feel the car!

[loggyboy]

wen driving thats fine, but wen ur bein timed and when 10th and 100ths of seconds means more than wen ur caning on the roads u need to take a calcualted approach to get the most u can out of ur car.

[loggyboy]

heres the rev ranges u stated with a change at 6500, i think they would use the most of the power/torque ratios
http://www.roybacer.net/gallery/albums/userpics/mike138curve.jpg

[mikeoxford]

I agree, and to be harsh, if you need to ask when is best to change gear, you'll probably never get it spot on.

You have to feel the car!

well the rev limiter is just a safegaurd. driver aid it may be or whatever - but i want to know im going to be safe. - thats my choice.

and as for shift light. i can tell when the power is dropping off, but when racing or whatever im too busy paying attention to the road - i cant check speedo or rev counter. im conentrating to much on the car / engine.

i change gear just as i feel the power drops off, the engine gets a bit of a whistle to it, and i must be changing around the 6000 RPM mark easily. i bet im not changing until 6500.

driving willy nilly on the road or down pod is fine. but i want the most calculated approach to get the most out of it i can. i havent got thousands to spend on turbos or big blocks. im trying to squeeze the best times out of this as i can. i havent even had quite enough money to do the final spec i wanted on the engine!

just like pie man..... once its on the car i will probably drive through it if i still feel the power is there.

its just a toy. but at the end of the day to me i feel its a a useful one

[Jim]

Best way to see when you need to change gear is to get your ass on the strip. Keep adjusting your gear changes for each run. Adjust the revs at the start, experiment with gear changes and revs. I was fortunate that I managed to get within .1sec on each of my 3 runs, so I must have been doing something right :) Either way, the best thing is to experience it first hand. True, a limiter is a safe gaurd, but you'll soon learn when the best time to change gear is.

Jim