How Much Power Is To Much

[Roy]

Unigroup...lol all the greatest engineering minds were produced by UTS, what a fine establishment

[Deano 1]

get it tuned to the safest max power the engine makes and than just drive it man, you can ether have 20kw or 400kw your right foot decides..... thats what i would do.

[Neil]

I don't think it really matters if it's a Turbo or N/A. I think you need to shift within the maximum torque rang. If the engine is going to detonate,,,then you have built rubbish and the builder should sell home vacuum cleaners door to door.

That where the power is,,,so use it!!!.

The Radical is a prime example,,,Eastern Creek is a pain in the arse. While I need as much straight line speed as I can get,,,the biggest corner I have trouble with is turn 6. I come out of 5 flat out and either need to change to 5th or hold 4th way past what I should. My fastest laps are when I change to 5th because it's in my torque range. Basically I've used all my pulling power and no amount of revs are going to get me there any quicker,,,sure it sounds like it is,,,but that's a crap lap.

So in summary,,,there's a lot to be said about not only using the torque curve,,,but also your diff ratio's. Skylines would be much quicker if you could change them to suit both E/C and Wakie of which I'll bet nobody does.

Cheers

Neil.

[MrStabby]

IIRC You want to shift for the maximum torque AT THE WHEELS, so the shift point will depend on how fast the engine torque curve is dropping off, and how much multiplication factor you will loose by shifting up to the next gear. You could plot the wheel torque for each gear (from the engine torque and gearing) then the intersection points will be where you want to shift. I would guess the shift point will be slightly different for each gear (unless that's how gear ratios are chosen)

Re Tune, detonation at peak torque just means that not enough timing has been pulled out, so its just a bad tune. There's no reason to avoid chasing max torque. More boost (or greater volumetric efficiency) = less timing.

[Roy]

SO just grabbing the first dyno sheet i could off Forced Induction...

Am i right in understanding that people are saying the thing should be changing gears at 6,000rpm to make sure its in the meat of the torque curve when it falls a few rpm for the next gear? I dont agree...but thats fine...

[Strik3r]

almost. My understanding is that you want to drive your car so that you spend the most amount of time with the most amount of torque.

My car makes peak torque at 5000rpm and holds it till 6500 before starting to taper off. So i shift at just past 7500 because that puts me back into peak torque for most gears

For my car with my gear/diff ratio's/tyres:

Gear Change RPM drop (change @7200) RPM drop (change @7500)

-------------------------------------------------------------

1 -> 2 -3023 (to 4177) -3149 (to 4351)

2 -> 3 -2486 (to 4714) -2589 (to 4911)

3 -> 4 -1906 (to 5294) -1985 (to 5515)

4 -> 5 -1728 (to 5472) -1800 (to 5700)

Gear Change RPM drop (change @7700) RPM drop (change @8500)

-------------------------------------------------------------

1 -> 2 -3233 (to 4467) -3569 (to 4931)

2 -> 3 -2658 (to 5042) -2934 (to 5566)

3 -> 4 -2038 (to 5662) -2250 (to 6250)

4 -> 5 -1848 (to 5852) -2040 (to 6460)

Remember power and torque have a direct relationship. P = (Torque x RPM) / 5252. You aren't going to be in your peak torque range without having most of your power coming on. For the dyno sheet you posted, it makes peak torque at 4000rpm and holds most of it until about 5600 when it starts to slowly taper off. It also makes 75% of its power at 4krpm. So the most effective powerband would be 4000 -> just shy of 7krpm (pretty obvious for what looks to be a mildly modified engine). You then pick your shift points so that you stay in that power band.

Well, thats what i've been taught anyway

[Roy]

Hey it may be right. But looking at G traces and speed traces off my data logger I know what works for my car.

[Strik3r]

post your dyno sheet !

[Roy]

I will have to print out the torque graph... I never bothered as when I was comparing my plot with a a built SR20 running the same turbo from teh same workshop I almost cried at how little and pathetic the shape of my torque curve is ....

[Duncan]

you don't have enough power until you can chirp second

seriously? get them to tune it to maximum mid range power at whatever boost that is, then set the boost 30% lower and enjoy years of trouble free track days

[BOZ22N]

Just go for a nice linear curve at about 16psi on std pulp with minimal knock. Then make sure you always run it on fresh pulp with some octane booster as a buffer and you will have the engine for a long time if you look after it.

[VB-]

where is this idea coming from that the tune will change where the motor makes power? your setup will determine the toruqe curve, tune it to make sure its safe, while still making decent torque.

how much power on the street? depends entirely on your ability to steer

power @ track: take from a race car driver whose name eludes me atm: "you have enough power when you can leave two black lines from the corner exit to the braking point of the next corner".

drag strip: you can only have too little traction, never too much hp

[Neil]

power @ track: take from a race car driver whose name eludes me atm: "you have enough power when you can leave two black lines from the corner exit to the braking point of the next corner".

Tlley in his Camaro would be the only driver that comes to my mind.

Cheers

Neil.

[old mate]

dont forget though its not all about power. the fastest silvia around lakeside has 275kw. i would just tune it to whats usable and safe.

have fun.

[badhairdave]

where is this idea coming from that the tune will change where the motor makes power? your setup will determine the toruqe curve, tune it to make sure its safe, while still making decent torque.

That would be the adjustable cam gears...

[Harey]

almost. My understanding is that you want to drive your car so that you spend the most amount of time with the most amount of torque.

My car makes peak torque at 5000rpm and holds it till 6500 before starting to taper off. So i shift at just past 7500 because that puts me back into peak torque for most gears

For my car with my gear/diff ratio's/tyres:

Gear Change RPM drop (change @7200) RPM drop (change @7500)

-------------------------------------------------------------

1 -> 2 -3023 (to 4177) -3149 (to 4351)

2 -> 3 -2486 (to 4714) -2589 (to 4911)

3 -> 4 -1906 (to 5294) -1985 (to 5515)

4 -> 5 -1728 (to 5472) -1800 (to 5700)

Gear Change RPM drop (change @7700) RPM drop (change @8500)

-------------------------------------------------------------

1 -> 2 -3233 (to 4467) -3569 (to 4931)

2 -> 3 -2658 (to 5042) -2934 (to 5566)

3 -> 4 -2038 (to 5662) -2250 (to 6250)

4 -> 5 -1848 (to 5852) -2040 (to 6460)

Remember power and torque have a direct relationship. P = (Torque x RPM) / 5252. You aren't going to be in your peak torque range without having most of your power coming on. For the dyno sheet you posted, it makes peak torque at 4000rpm and holds most of it until about 5600 when it starts to slowly taper off. It also makes 75% of its power at 4krpm. So the most effective powerband would be 4000 -> just shy of 7krpm (pretty obvious for what looks to be a mildly modified engine). You then pick your shift points so that you stay in that power band.

Well, thats what i've been taught anyway

Perfect summary here:

http://www.allpar.com/eek/hp-vs-torque.html

[The Bogan]

FYI @15lb

2.5 cat is holding it back, with a better sized exhaust it should hold the torque better Ive been told, 3.5 inch from dump back will be coming over the next few days.

Thanks for all the info guys.

[Deano 1]

thats a nice outcome man, now just to get some track time cranking

[Sunkist]

and you said it was a nooby question!

Good work! thats my goal to hit 300awkw in the stag. almost there too! I think anything above that for me is pointless. its a wagon FFS!

have you got a write up of mods anywhere??

[grippy]

You'll have to drive and see. There is simply no other way to know what will be right. Tune it, track it and you will find a whole pile of issues that you will want to address.

Suspension will play a major part as will weight, power, torque, lag, brakes etc.

But you will enjoy getting it sorted so start enjoying!!