G_Sleigh_STi

From thsi graph below is there a way to see where the most power is and where is best to change gear?

Basically wanting to get the best 1/4 mile time i can and this is pretty much the map i have on my car.

I want to know what RPM to change into each gear at and what the launch at?

leonpoole

A little off topic but what mods have you done to get that figure

G_Sleigh_STi

These guys took it for the day, its all listed here:

http://www.tsl-motorsport.co.uk/engine.html

I have got my starts sorted i think at around 5500-6000rpms, it seems to go well. I just want to learn the best place to change to bring my times down!

FLAT ERIC

iTrader: (1)

To keep your times down you need to keep the torque at its optimum level for as long as you can. Yours peaks @ 3610 but then only holds to around 4500 before it starts to drop off.Then by 6000 its on it's way.

So going beyond 6k isn't going to achieve much & you had best not allow it to drop below 3600 after you have changed gear.

Although my figures are a lot lower, my "sweet spot" is over a much wider rev range.So my gear change is easier to make at the "right" time, with a bigger margin for error.The torque is still reasonably near to peaked at the same time that the power peaks as well.



Mark

G_Sleigh_STi

Mark those graphs on first glance look very simlar, but i can see what your saying now. Your torque line is equal for longer before it starts to really drop off, where as mine drops quicker.

Where the BHP and TORQUE lines cross? is that important in any way?

So if i never let my car drop below 3250rpm.... When i change gear i want the revs to drop to around 3400rpm? to get the optimal performance for longer? And i never want to take it over 6000rpm? Because its wasted RPMS which are not really generating any extra power?

Am i on the right lines with that thinking?

At Santa pod when i was running my 13.5's i was taking it all the way around to 7000rpm in every gear.

JohnS

iTrader: (1)

Your forgetting about gearing. Although the torque may drop off above a certain revs, when multiplied through the gearbox and diffs, there will in most cases be more torque/power at the wheels higher up the rev range in a lower gear, than at peak torque in a higher gear.

To get maximum acceleration, you should generally be looking to take the car to the red line in each gear before changing up, though depending on the gearing, you could probably change from 5th to 6 at less than peak revs and not lose/gain much (academic for 1/4 mile sprints anyway).

John

G_Sleigh_STi

Blimey. Well thats completely different to what i was thinking. So your saying change just before you start bouncing off the top end?

I want to see times from people running the same power and upgrade as me at Santa pod and see what we are doing differently!

Jay m A

iTrader: (2)

You need to plot your gearchange rpm points at certain speeds in certain gears to see how much area under the Power curve you can get in.

for example if at xx mph the geearchange from 3rd to 4th is a rpm difference of 2000rpm, then you'd want to shift at approx 7250 to get 5250 upon lifting the clutch. That will give you the biggest area under the power curve for that gear change.

For lower gears the band might be 1500 rpm, so the shift point will move a little bit to 6600 or so.

But remember that power plot was for 4th or 5th gear, so bear that in mind!!

Jay m A

iTrader: (2)

Just note its th Power curve that you need to go by, which is a function of torque and revs

If it was the torque curve that determined shift points then there'd be a load of chipped TDi's at TOTB

Pavlo

Your peak power is a quite symetrical(sp) around the peak. So you need to check what your RPM drop is like. If it's a 2000rpm drop on each gear change (it will vary a little) then you would want to change 1000rpm past peak power, so you run through peak power as you run.

If the power dropped off much more quickly, then you wouldn't push it much pas peak power at all.

If you were to have a 2000rpm drop, and change at around 7200, putting you back in at 5200, you would be running over 300hp throughout each gear. If you changed at 5500, it would only just get over 300hp, and when you got into the next gear you would only be at around 240hp, with less RPM to spool the turbo back up after the gearchange.

Paul

G_Sleigh_STi

Right o.k...

So if i take her out and give her a bit of a booting and report back how many revs i lose on each gear change then i will be able to try and narrow down the best time to change. I will get that done and report back

Is there anyone on here who wants to take my car on the strip at Santa Pod whos extremely experienced with scoobies and quarter miles to test her and see how they would react to it.

You cant beat advice from the best If anyone is up for it!

Pavlo

What is the car? I should be able to tell you the RPM drop for each gear.

Paul

G_Sleigh_STi

STI8 new age, 04 plate.

I just took her out and i can tell you the following if this helps:

All these figures are drops from 6000RPM

1st to 2nd gear = 1000RPM drop
2nd to 3rd gear = 1100 RPM drop
3rd to 4th gear = 1200 RPM drop
4th to 5th gear = 1500 RPM drop

i tested her over and over and they seemed pretty constant drops.

Does this help figure out where to change?

Jay m A

iTrader: (2)

Yes

looking at your graph it seems peak power is 6250, perhaps other data on the printout can tell you better.

As Paul says, the curve is pretty symetrical around peak, so to get the best shift point, divide the rpm differences by 2, and add that to peak power rpm. That is your shift point for each gear.

The shift rpm will increase as you go through the box.

However, things happen pretty rapidly in the low gears, plus there is less engine load to help boost/spool/torque - so with that in mind and (I assume) the OE shift light is not gear configurable, I'd set it at 700rpm past peak power rpm and see how it goes.

Edit, doh, just seen the massive 333@6100 power written over the plot. Is this the plot for your car, or is it the one on the TSL website?

If 6100 is applicable to your car, set the shift light to 6800

Pavlo

As above!

G_Sleigh_STi

Well this is the one taken of their website, but i have been told i have the exact same tune up with pretty much the exact same map from Richard. So the differences are going to be unnoticable.

Obviously every car reacts differently to modifications and mapping but its pretty spot on.

So i got a bit confused by your post...

I am still learning about engines and this lark...

So i want to set my shift light to 6800RPM.

And i want to change at that in each gear?

Or start changing lower and move up to that?

Gutmann pug

TSL are pretty good and if Richard Bulmer did the work your on to a good thing. I too run a TSL333 mapped car and on the rollers it hits 329bhp with 319ib/ft torque. The power curve is slightly different from the TSL one from memory. So if your using the curve to work out what to do then I would get YOUR car on the rollers and see what your curve looks like.

Oh and on another thread I advised you on tyres. I didnt realise you meant your 1,000 miles were on the booooooring drag strip i'm off to edit any advice I gave

If it aint got corners it aint worth driving.


Gary

Floyd

iTrader: (9)

I hate to agree with Gary but I still don't get the drag thing. I'd also be worried about stressing everything to the hilt for each run - seems like a good way to bust expensive stuff

F

G_Sleigh_STi

Hey chap.

I dont just use it for 1/4 mile. I am up for everything from 0-60's to 1/4 mile and track days.

I love it all! I mean it ALL!

Yea i want to get mine on a rolling road SO MUCH! ASAP i tell you

Hoppy

Just to be controversial...

Forget torque. It means nothing until tranlated to bhp by your gearbox. What makes you go is how much bhp you can lay down, the more the better, and the longer the better. Obviously. Just look at the bhp plot and ignore the torque for this purpose.

Hence you need to select gearchange points which deliver as much bhp as possible until you hook the next gear. As ratio differences change between gears, so your shift points will also change between gears.

Having said that, unless you are a very serious drag artists ( ) revving it to the redline in each gear will probably be a pretty good guide, then work on your start and shift technique. Once they are as good as they're gonna get, maybe that's the time you'll see the benefits of changing up at exactly the right point.

There's a lot of technique in dragging but I find the high heels are best left at home

Richard.

G_Sleigh_STi

My gear changes i think are as fast as i am ever going to get, its one thing that i am pretty good at. My reaction time to changing and popping the clutch up and down is pretty good.

My starts are getting much much much better so i am on the way their.

I am going to go to Santa pod and test aload of different theories about when to change.

I will try:

changes all at 6000RPM
changes all at 6500RPM
changes all at 7000RPM
changes all just before the limiter

Try each theory over and over again and see which one pulls the better times. Suppose you cant beat testing it for real.

Hoppy

That's probably a pretty good compromise, but if your bhp plot is accurate, particularly with regard to power/rpm, you should be able to work out exactly where to shift each gear for max go - as has been said earlier.

Can you check if the rpm shown is accurate? I only say this because a) it's absolutely vital, and b) sometimes this is set manually on the dyno by the operator who presses a switch when the needle passes x rpm. If he's 200rpm out, then you'll have lost a couple of tenths before you start

Cheers,

Richard.

G_Sleigh_STi

I am going to go get her dyno'ed at WRC developements and find out my true graph

Floyd

iTrader: (9)

How about this http://bbs.scoobynet.co.uk/showthread.php?t=434616 cheap RR day soon at WRC tech?

F

G_Sleigh_STi

Oh hell yea! I am there