Gen 5 GT - Bang for Buck Mods / Tune

[KiDo_Tuning]

Comparing a stock LGT 5EAT, it made 141Kw@wheels and went 173Kw tune only.

Even a 3psi boost increase(to 16.4psi) will see 30Kw gain in a manual without even leaning out the AFR's or modifying timing too much and the dump should see closer to 200Kw.

Oh look another unbacked-up claim.

And wait, yet MORE "evidence" of your claims by using a non-relevant car that doesn't actually back up your claim...you know, like claiming a stock 4EAT SH Forester with just your tune can do 0-100 in sub-5s with ease, then showing a LGT with a bigger turbo, not actually doing what you claimed

Fish, If you're not entirely happy with the tune, take it back and talk to them.
I'm not a customer of Mercury because I don't like ECUtek and am happy using the tuner I do, but the couple of times I have called them, they have been awesomely helpful, so their customer service, I can vouch for

Same EJ257 Dual AVCS motor as STi Sean. The turbo looks more compact due to location but it outflows VF52's and needs less boost than an 09+ WRX to make the same power. 14.7psi at peak power when tuned and 13.2psi by redline is enough to make it a monster

Just like stock MY10 LGT running 13psi can run a flat 5 with less area under the acceleraion curve than a 4 speed with a TD04?

[Fish Jetski]

Fish, If you're not entirely happy with the tune, take it back and talk to them.
I'm not a customer of Mercury because I don't like ECUtek and am happy using the tuner I do, but the couple of times I have called them, they have been awesomely helpful, so their customer service, I can vouch for

Who is your tuner Sean?

[Sean82]

Comparing a stock LGT 5EAT, it made 141Kw@wheels and went 173Kw tune only.

Even a 3psi boost increase(to 16.4psi) will see 30Kw gain in a manual without even leaning out the AFR's or modifying timing too much and the dump should see closer to 200Kw.

Oh look another unbacked-up claim.

And wait, yet MORE "evidence" of your claims by using a non-relevant car that doesn't actually back up your claim...you know, like claiming a stock 4EAT SH Forester with just your tune can do 0-100 in sub-5s with ease, then showing a LGT with a bigger turbo, not actually doing what you claimed

Fish, If you're not entirely happy with the tune, take it back and talk to them.
I'm not a customer of Mercury because I don't like ECUtek and am happy using the tuner I do, but the couple of times I have called them, they have been awesomely helpful, so their customer service, I can vouch for

Same EJ257 Dual AVCS motor as STi Sean. The turbo looks more compact due to location but it outflows VF52's and needs less boost than an 09+ WRX to make the same power. 14.7psi at peak power when tuned and 13.2psi by redline is enough to make it a monster

Just like stock MY10 LGT running 13psi can run a flat 5 with less area under the acceleraion curve than a 4 speed with a TD04?

What are you trying to say there Matt? That doesn't make sense...

[KiDo_Tuning]

Physics...

What makes a car move? Getting the most area under the torque curve improves 0-100kph times.

On a TD04, why would you rev the engine out where the stock exhaust strangles the airflow, when you can force a gearchange to occur earlier to keep the engine under peak torque. For example, Rev to 6600rpm in 1st gear, let the auto change into 2nd gear and then power through from 4000rpm up to rev limiter to get to 100kph.

However, TD04 has a LOT to offer at low rpm(as does the fast spooling VF54) so if on the TD04 Forester example, you find where the acceleration starts to slow at say 4500rpm, then force a gear change into 2nd gear where engine revs drop to 2800rpm and you have more torque giving more acceleration thus a faster 0-100kph time.

[Sean82]

One; not what you said earlier.

and,
B. Where's this Forester that does the 0-100 sprint in under 5s with just a tune??? (You post LGTs as your "examples" on OzFoz, why not post a Foz here on a Liberty forum?)

[Fish Jetski]

Physics...

What makes a car move? Getting the most area under the torque curve improves 0-100kph times.

On a TD04, why would you rev the engine out where the stock exhaust strangles the airflow, when you can force a gearchange to occur earlier to keep the engine under peak torque. For example, Rev to 6600rpm in 1st gear, let the auto change into 2nd gear and then power through from 4000rpm up to rev limiter to get to 100kph.

However, TD04 has a LOT to offer at low rpm(as does the fast spooling VF54) so if on the TD04 Forester example, you find where the acceleration starts to slow at say 4500rpm, then force a gear change into 2nd gear where engine revs drop to 2800rpm and you have more torque giving more acceleration thus a faster 0-100kph time.

It isn't torque that produces fast 0-100km/h times. It is AVERAGE power over time. Therefore acceleration occurs quicker at 4500RPM at slightly less torque than at 2800RPM due to the gearing of the vehicle. The reason why a wide torque engine is better than a peaky engine is because it gives a higher AVERAGE power over time even if the peaky engine creates better MAXIMUM power at a particular point in time (or rev level).

To say that an engine spinning at 2800RPM with Torque of 400NM ATW is creating faster acceleration than an engine at 4000RPM with Torque of 350NM is against the laws of physics. Power is important - just look at F1 cars from last year which had max torque of less than 300NM, but were pretty quick due to higher revs (ie up to 20,000RPM).

[KiDo_Tuning]

It isn't torque that produces fast 0-100km/h times. It is AVERAGE power over time. Therefore acceleration occurs quicker at 4500RPM at slightly less torque than at 2800RPM due to the gearing of the vehicle. The reason why a wide torque engine is better than a peaky engine is because it gives a higher AVERAGE power over time even if the peaky engine creates better MAXIMUM power at a particular point in time (or rev level).

To say that an engine spinning at 2800RPM with Torque of 400NM ATW is creating faster acceleration than an engine at 4000RPM with Torque of 350NM is against the laws of physics. Power is important - just look at F1 cars from last year which had max torque of less than 300NM, but were pretty quick due to higher revs (ie up to 20,000RPM).

Torque is the average power over time(revolutions per MINUTE), since Hp = (RPM x FtLbs) / 5252 hence why the area under the torque curve indicates the most amount of effort being applied. Since the TD04 as an example can only maintain around 12psi above 4800rpm, by the time you have changed into 2nd gear for the power curve as torque is falling away Vs 15psi at 2000rpm as your carrying over the boost from 1st gear since it is not dropping to 12psi up top and then having to wind up the boost again once it changes gears. Falling torque is slowing momentum due to less force being applied... number one reason why any VF4x/5x can hold that momentum and thus acceleration.

Other thing to consider is turbo heat as you wind out the engine rpm as it becomes inefficient then that heat affecting the next gear.

So if you did an entire torque curve and plotted Vs RPM with an engine RPM sub X Axis in 1st gear then again in 2nd gear, then move the two torque graphs onto a single Speed axis, you can then find where the most amount of effort is applied over time and distance.

FYI: Torque curve applied for the longest in gear acceleration is what a CVT is all about It changes the ratio and keeps the torque constant while road speed increases

[Fish Jetski]

Torque is the average power over time(revolutions per MINUTE)

Torque is not the average power over time. Torque is the amount of 'twist' at a moment in time. Power is the multiplication of that torque over time (ie how many times that twist force is effected in a unit of time). See http://en.wikipedia.org/wiki/Torque

You do have valid points about boost, and heat and so forth, but short shifting before 6000RPM does not increase acceleration in a tuned Subaru 2.5T in 1st to 2nd or 2nd to 3rd period. The gap between the ratios is such that the drop off from peak power at higher revs in the lower gear is never enough to make up for the increase in torque in the higher gear.

Your comment regarding CVT is precisely why the torque curve is critical for the Gen V Liberty GT Manual - an agricultural, widely spaced transmission.

I know about the difference in feel of the two turbos. I drive the TD04 and the VF54 (both in manual with a 3" Dump Pipe mod only) tuned by the same tuner back to back daily in 2 cars that are within 20kg's in weight (MY09 Forester XT and Liberty GT). At the moment the extra 20KW ATW of the Liberty is nowhere near the daily benefit of the bottom end response of the Forester - it's a beast. I want that response in the Liberty!

[<GB>]

^^ love when people don't understand what torque is, we used to call it twisting moment in uni

[Sean82]

"/5252"
Who was the guy that came up with that? I'll bet he had a pocket protector.


Matt: yeah totally get the short shift idea. I do it in my lib because VF38=small. (Sometimes, I still haven't overcome the thrill of hitting the rev limiter with the 5EAT)

Can you post up a graph or Dyno log of a TD04 to explain clearer why you'd short shift it?

[dr20t]

Didnt want to buy into this debate but Matt is spot on with his argument about smaller turbos on bigger capacity engines performing worse as revs climb

Td04 or vf46 on a 2.5 Shifting at 6000 plus rpm will actually hurt your acceleration for many reasons. One being peak torque is well and truly over, and power then means nothing because power is the constant here and won't change unless you miraculously have a volumetric efficiency improvement in the upper rev range with a hot intake of compressed air from the lethargic turbo, which could be achieved with a water/meth injection or some sort of avcs kick (on dual avcs motor)

Short shifting into the meat of the torque curve is far more advantageous than wringing its neck to 6500 for no reason

My torque curve stops at 7800rpm. Revving past that is only a good thing if shifting at 7800 into the next gear drops me out of the peak torque zone (which it doesn't). Eg. If a motor makes peak torque between 3000 and 4800 rpm, and Shifting at 4800 brings next gear to 2500, then that's not shifting into the peak torque curve. So you would shift at say 5200rpm and next gear is smack bang in the meat of the torque curve

Torque is what gets you accelerating not power

Mick

[alexeiwoody]

Torque and Power are only separated by a constant and RPM. The statement that increasing the torque improves acceleration is of course true (and of course the wider this torque across the RPM available - the more power and the better acceleration). Everything Mick said about the "meaty torque zone" is also true...but you guys are missing each others' points.

As fish said - a stock tuned 2.5T is not going to have a major difference from shifting ealier. A tuned 2.5T does not rev to 7800/9000 like yours Mick and neither does it produce 350kwatw and whatever insane torque you're pushing. On my stock block - I would be lucky to see 0.1 of a second of a difference in a 0-100 sprint. Just watch the videos I posted in the other thread, you'll see both early and late shifting.

Even though it's a little off in this topic, I do very much like reading your drag expertise, Mick

Hopefully Matt can supply us with a graph of a tuned gen 5. That turbo location is sweet and a decent tuner should be able to see some very early (or just-on-timely) torque and power, compared to most other Subarus.

[dr20t]

It's the rate of change that's important

If you look at a dyno graph, the part of the power graph that climbs at the steepest gradient is where you wanna be to accelerate faster

If that rate of change is held for a consistent period (flatter torque curve) then when / where to shift becomes largely irrelevant.

Its when you have a turbo that runs out of puff early that the argument for short shifting becomes important

A vf54 is not a tiny turbo but its also not huge by any stretch of the imagination. Especially on a 2.5.

So saying that short shifting is advantageous is not outlandish. I would still like Matt to post a dyno chart or 0-100 run of a gen 5 with a vf54 or a foz with td04 and tune to back up the claims. But what I'm saying is his theory is correct

Mick

[dr20t]

And lets be serious I do like revving to 8800rpm just to hear that sweet exhaust sing, despite it not making any real sense to do so. Just like some of the engine noises I find myself making sometimes

[alexeiwoody]

It's the rate of change that's important

If you look at a dyno graph, the part of the power graph that climbs at the steepest gradient is where you wanna be to accelerate faster

If that rate of change is held for a consistent period (flatter torque curve) then when / where to shift becomes largely irrelevant.

Its when you have a turbo that runs out of puff early that the argument for short shifting becomes important

A vf54 is not a tiny turbo but its also not huge by any stretch of the imagination. Especially on a 2.5.

So saying that short shifting is advantageous is not outlandish. I would still like Matt to post a dyno chart or 0-100 run of a gen 5 with a vf54 or a foz with td04 and tune to back up the claims. But what I'm saying is his theory is correct

Mick

I agree, and it was very apparent on my last bike when drag racing friends. There is a sweetspot for shifting and it's not at the redline. I didn't see major gains on the lib though. When I compared the videos and logs I had on ethanol, there was maybe 0.1s difference, and that was even with a crappy redline shift by the box in one.

This is 0-100 though (which is over in 5 secs), and as I commented in that '0-100 tuning' thread awhile back - the earlier shift was making a visible difference once I was past 100