flynnstudio

My wrx 300 with ppp has a power and torque curve that brings all the power (261BHP) in like a jack hammer at 3000rpm and drops it off like the pepsi 'big one' at blackpool pleasure beach at 5500rpm.

To this end I basically never exceed 5500rpm as there is 100% no point whatsoever.

my question is this -

Has prodrive/subaru intentionally mapped it this way to create long term engine reliability by removing the need to rev the engine to 7000rpm with 'high power/high torque' or is it just 'the way it is' and it 'really needs a new remap to extend that power up to the limit ?

Is this what third party remappers are doing - simply using this 'fat' left in the map by prodrive 'at your own risk' ???

Gear Head

iTrader: (2)

It's just the characterists of the TD04 turbo that you have.
Most dyno read outs all show this turbo tailing of toward 5500-6000rpm.
Just the price you pay for the super fast spool up!
Exactly the same on my 1999 UK Turbo, running 277bhp.
I understand that I TD04 Hybrid from www.andyforrestperformance.co.uk, should help extend the turbo rpm range right upto the limiter.

C2forWRX

your right like. in my wrx300 i dont see the point going up to 6k and past as there is not much pull and doesnt sound as good. get the sense your doing more damage than good above 6k

flynnstudio

Thanks chris - so it's the turbo running out of puff rather than any other reason - mmh very interesting - so that means that for a few hundred quid I should be able to bolt on a replacement turbo and have a very different level of sustained power.

I take it this is the case with all WRX both with and without PPP....

I must say it is kind of reaaaallly annoying now that I know......

yeah C2 - unless your in 5th it's always best to change up before 5500rpm and get back on full power/full torque and avoid the last crappy 1500rpms...

Fizz

iTrader: (1)

you'll still need some sort of re-map with a new turbo anyhow.. so not worth having PPP. . .

flynnstudio

I've already got the PPP - came standard with the WRX300 - ...but now I'm sort of realising that what you really get is a 'off the shelf' chip map and a fattish back box and a slightly bigger TMIC hose...when really what the package needs is a new turbo as well...

I mean 225 to 261 is a rather miserly 36BHP for £1600...really don't know why insurance companies get so hot about it when it actually needs a new turbo to make anything of it...

Shark Man

Yeah, the TD04 starts to run out of puff at 5500rpm. never found it an issue as mine still pulls cleanly way past 6000rpm...just I hit full boost at 2800rpm and half boost at 1500rpm...which is still far far too high IMO, but then, there is no such thing as a TD03 to suit my tastes and hate of lag

ZEN Performance

Just because the torque drops off at 5500 it doesn't mean that the power does. FOr instance, it will probably pull harder at 6000rpm in 3rd than it would if you changed up to 4th and pulling from around 4000rpm.

flynnstudio

...yes your right now that I look at it - according to the graph the power does hold steady to 6500rpm but the torque drops off sharply at 4800rpm.

I'm assuming this graph which came from the WRX300 brochure is the same for all WRX PPP regardless of them being a WRX300 or not...

So the real question is that until you reach 5th gear will more speed and more pace be attained from changing up and using the higher torque in the higher gear than sticking in a lower gear for say 1500rpms with obviously sharply declining torque ???

C2forWRX

change no later than 6k and you will be getting the best of the performance.

Gear Head

iTrader: (2)

I have to say though m8, your torque does drop off rather quickly.

flynnstudio

This brings us back to the old 'torque vs horsepower' thing again.

If torque is the 'turning force' that does all the work in overcoming the intertia of a stationary mass then when this drops off the 'muscle' that creates blistering acceleration goes into terminal decline immediately after 4800rpm...

Horsepower at this point takes over but I don't actually know what it's accomplishing for 1500rpms - is it really only now demonstrating the ability to 'maintain' the current speed (a measurement of work/watts?) and not actually gain speed ??

Is this map the same as the 05 sti or a stock wrx with ppp ???

MJW

It will be the same map as the WRX PPP as far as I know. There would be little point in having extra power beyond 6k rpms as you'd be bouncing off the limiter within a thousand revs. As stated above if you want to give it some beans, switch up at 6000

ru'

HP is just a function of torque and rpm...

flynnstudio

well that's what I thought but it's clearly not that straightforward since the hp is still rising and then stays consistently flat when the torque is going hard south.

HP is from what I understand 'work' or 'watts' as in it's the 'sustaining' power of the engine. ie it's ability to maintain a given speed once acquirred by torque but not able to actually increase it anymore...

On that graph there is a clear 1800rpm where hp is held tight at 261bhp whilst torque drops from 340 nm to 260nm in the same band so they are not so related as one might think.


I think the torque dies as others have pointed out 'because the turbo has run out of windage' and the small 2litre engine simply can't provide enough natural displacement 'oomph' on it's own to sustain the torque figure at increasing revs but it can keep the engine spinning which keeps the hp figure constant...

so were back to a new turbo whichever way you twist it...

Shark Man

You can feel where the torque drops off without looking at any graphs or guages just by driving it.

Using a G-force metre will also confirm that the rate of accelaration does drop off as the engine goes past 5.5K and approaches 6K rpm.

The turbo is still working and still delivering very useful pressure (still over 0.5bar ) and the engine is still producing useful torque to maintain good accelaration well past 6K, just not as much as in the 3K to 5K band.

Tidgy

mod a uk300 at your peril, will destroy resale value

ru'

Torque is the turning force, and is not related to 'time'.

Assuming the torque stays constant as rpm increases (which it doesn't, for a variety of reasons) the HP would increase.

Essentially, if the engine is doing 1rpm and producing 1Nm the amount of work it can do (the power) will be less than if it was doing 2rpm and still producing 1Nm - the torque's the same, but now the engine is 'producing the force' twice as much, as there are twice the 'power strokes'.

You could think of hp as 'torques per second', if you like (it'd be wrong, but hopefully it gives you an idea).

HP is torque x rpm, with a constant scaling factor. This is why all power graphs will have the torque curve and HP curve cross over at one point in the rpm range (between 5000 and 5500 rpm, assuming the graph scales are HP and Ftlbs).

Here's my 05 WRX PPP for an example:

Shark Man

It crosses at 5252:

Hp = (rpm x torque)/5252

Or:

Torque = (5252 x hp) /Rpm

flynnstudio

ok...let me put this into something I can understand..

your saying HP is the number of torques per second...

so lets say I'm with a very special lady I just met at a club and we are 'going for it' on her best friends living room carpet while she's upstairs with my mate....

Now, I'm basically thrusting 60 times a minute ( I've had a few beers and am well up for it!) and with each thrust I push her farther along the carpet. Now I can keep pushing her along the carpet until I reach 100 thrusts per minute at which point she stops moving and and starts shouting 'oh yes oh yes'....

(I should add for any lady readers that at 120 thrusts per minute I hit the red line and blow my engine but I'm a careful driver so I ease off on the throttle a little and keep the ride going - oh yeahh!!..)

...and so what your basically saying is that at 100 thrusts per minute my thrusts are less powerful but there are more of them which is why she's really digging the faster strokage and saying all kinds of dirty things..???

ru'

robsw

This is the best general thread I have read on this site for absolutly ages, most excellent!

hades

The other interesting thing is that torque at the wheels is torque at the flywheel multiplied by the gear ratio - so lower gear = more torque at the wheels. Therefore, you're potentially getting more torque at the wheels by revving higher and using a lower gear.

If you equate a bigger gear ratio (i.e. 1st has a bigger gear ratio than 5th) to a bigger something else, not only is flynn pleasuring his "very special lady" with more faster thrusts, he has extra size on his side too now!

TD04's are capable of holding fairly decent power to decent revs - mine (tuned more than a PPP ) has >280bhp from 5800-6800rpm. Doing the maths, I definitely do not want to change gear before 6k as suggested above, more like 6800rpm in my case.

However, no question that an Andy F hybrid TD04, or just a plain bigger turbo (FV34/35, TD05, TD0520G etc, giving more power but more lag as you move up in size) will give much more power and hold it better at the top end. Personally, I think a nice hybrid TD04 is about right for a WRX, not much lag, not enough extra torque to trash the WRX gearbox, but quite sizeable power/torque gains. Go for bigger = more torque, and don't expect the transmission will necessarily hold together.

ZEN Performance

Yes that is basically the whole torque/HP arguement in a very neat but nonetheless correct, shell of a nut.

One can only wonder at your explaination of the tradeoff of boost and power verses backpressure

Paul

New_scooby_04

iTrader: (4)

Well, yes and no! A bigger turbo will deliver more omph, but you'll need some supporting mods and it'll cost more than a few hundred if you want to do it properly.

Firstly, any bigger turbo will mean a higher spool threshold (the point at which the turbo really starts to deliver the goods) So, you'll want to offset this with other mods as much as you can. For you, this would mean a decat/sports cat down pipe, a decat up-pipe as IIRC the cat in the new age ones tend to disintergrate at higher boost than PPP and I'd also recommend porting the headers. You have the uprated intercooler hoses, but not the rest of the turbo hose kit, I'd get this off Samco. Also, since you're putting a lot more air into the engine, I'd want to go with the Walbro uprated fuel pump. As for the turbo, TD04 Hybrid gets good reviews, and the VF28,30,34,35 all work very well too. You WILL need a remap for the bigger turbo and I'd get a 3 port boost solenoid whilst you're at it to to better control the boost!

I recently did a turbo and supporting mods upgrade, read about it here

https://www.scoobynet.com/api-and-br....html?t=527345

Do it right and there is a very significant improvement in the car!! Delta dyno measured mine at 319 and 316 bhp ft/lbs respectively on a day with 30+ degree ambient temperature.


Ns04