Torque Dip

[b.e]

Originally Posted by sierra

Blue injection volume curve?

The problem with that is if it's showing the total fuel being injected at full throttle? Then why is it only showing another 10% of fuel being used at 5,600rpm than is being used at 3,500rpm? Or almost the same fuel at 7,600rpm as at 4,900rpm?

Blue-green on my screen.

I think it's the volume per cylinder, not volume per second. That would make it much less dependent on RPM.

[IMOA]

You can be more aggressive with the tune when you're only running direct injection as it's fundamentally more detonation resistant. My read is that the combination of the intake and the cams have been designed to give a big hump in torque low down for daily driving and a hump up top for when you're driving hard. This leaves a hole in the middle which they have been really aggressive in the tune in an attempt to minimise as much as possible.

[Grip Ronin]

Originally Posted by sierra

Just googled AEM tuning and found a whole new world!

you didnt know about them? i been running one in my civic for years. best ecu ever. closes think to a motec and a sub normal price

[pheoxs]

@Visconti perhaps he could comment on adjusting the direct/port injection overlap and its affects on the torque dip in his tunes?

[Synack]

Originally Posted by sierra

No, turbocharging always fills the torque dip too.
Do you know if Ecutek can turn the port injection back on?

At the time we were using ProEFI.

[sierra]

Originally Posted by b.e

Blue-green on my screen.

I think it's the volume per cylinder, not volume per second. That would make it much less dependent on RPM.

The Mass Airflow is green but it's the only one without a trace on the chart.
I've been picked up many times by women for the blue/green border, they have a better sensitivity to colour so who knows?

Good point with the volume. If that's the case then the chart should indicate volumetric efficiency. The only problem with that is that the lines climbs from just below 3,000rpm to 3,600rpm when it's losing power?

[sierra]

Originally Posted by IMOA

You can be more aggressive with the tune when you're only running direct injection as it's fundamentally more detonation resistant. My read is that the combination of the intake and the cams have been designed to give a big hump in torque low down for daily driving and a hump up top for when you're driving hard. This leaves a hole in the middle which they have been really aggressive in the tune in an attempt to minimise as much as possible.

It still makes no sense that they would have left the gap. The only thing that makes sense is emissions at say 50% of the max rpm which is 3,700rpm and they turned off the port injection to keep it super clean at the expense of some torque.

[sierra]

Originally Posted by pheoxs

@Visconti perhaps he could comment on adjusting the direct/port injection overlap and its affects on the torque dip in his tunes?

That would be very interesting. I'm wondering if Ecutek has the ability to turn it back on?

[sierra]

Originally Posted by Grip Ronin

you didnt know about them? i been running one in my civic for years. best ecu ever. closes think to a motec and a sub normal price

No, never heard of them before. The warranty is only 3 years here so i'll save that for later. What do they sell for?

[IMOA]

Originally Posted by sierra

It still makes no sense that they would have left the gap. The only thing that makes sense is emissions at say 50% of the max rpm which is 3,700rpm and they turned off the port injection to keep it super clean at the expense of some torque.

I think you're underestimating how hard it is to get a flat torque curve! The engine has variable valve timing but lift is fixed and intake length is fixed, you're going to end up with a hole somewhere as you just don't have the adjustability in the intake to maximise VE everywhere. It's a sportscar so it needs to work up top but it is intended as a road car so it needs bottom end to cope with DD. That leaves the lower/midrange which you don't really need for either duties as the one which is the least important. It's not a matter of choosing to leave a hole, it's a matter of not being able to fit the more expensive intake/cam technologies in the price target and then selecting the other items (intake length, cam lift and duration etc) so that they are their most efficient where it matters and least efficient where it doesn't.

You also have to remember that direct injection only gives better torque, not worse. As it's able to deliver the fuel charge very close to the plug the flamefront propogates through the fuel charge quicker minimising the risk of detonation, this lets you run more timing to maximise torque. A number of tuners have remarked that the tune is very aggressive through this area in the maps which re-inforce that the issue is intake harmonics, not tune. The fact that no-one has been able to tune this out even though they have contol over when the port injectors are used also tells you that the problem is harmonics, not tune.

Everything in an engine is about compromise and to me it screams that they've compromised on cost by not using variable lift or variable length intakes (also a reliability issue for that one) which will result in losing VE somewhere which they've placed at the least important spot in the rev range. To minimise this they've gone aggressive in the tune however you can only make up for a lack of air so much in the tune so we're still left with a hole.

[Flat Black VW]

Very interesting thread...

Hoping one of the guys who has been able to mess with the tuning on this car can shed some light...

[sierra]

Originally Posted by IMOA

I think you're underestimating how hard it is to get a flat torque curve! The engine has variable valve timing but lift is fixed and intake length is fixed, you're going to end up with a hole somewhere as you just don't have the adjustability in the intake to maximise VE everywhere. It's a sportscar so it needs to work up top but it is intended as a road car so it needs bottom end to cope with DD. That leaves the lower/midrange which you don't really need for either duties as the one which is the least important. It's not a matter of choosing to leave a hole, it's a matter of not being able to fit the more expensive intake/cam technologies in the price target and then selecting the other items (intake length, cam lift and duration etc) so that they are their most efficient where it matters and least efficient where it doesn't.

You also have to remember that direct injection only gives better torque, not worse. As it's able to deliver the fuel charge very close to the plug the flamefront propogates through the fuel charge quicker minimising the risk of detonation, this lets you run more timing to maximise torque. A number of tuners have remarked that the tune is very aggressive through this area in the maps which re-inforce that the issue is intake harmonics, not tune. The fact that no-one has been able to tune this out even though they have contol over when the port injectors are used also tells you that the problem is harmonics, not tune.

Everything in an engine is about compromise and to me it screams that they've compromised on cost by not using variable lift or variable length intakes (also a reliability issue for that one) which will result in losing VE somewhere which they've placed at the least important spot in the rev range. To minimise this they've gone aggressive in the tune however you can only make up for a lack of air so much in the tune so we're still left with a hole.

Are you are suggesting the port injection was turned off in that rpm range so that purely direct injection could maximise the torque to compensate for a lack of air? That it's nothing to do with an emission target?

[Acree]

Originally Posted by sierra

Are you are suggesting the port injection was turned off in that rpm range so that purely direct injection could maximise the torque to compensate for a lack of air? That it's nothing to do with an emission target?

That is absolutely correct. The torque dip has absolutely nothing to do with fueling. It's all about VE of the engine across the rpm band. The torque dip is due to a combination of intake manifold and head design. Otherwise, they would have tuned it out from the factory and we wouldn't be having this discussion.

-Acree

[sierra]

Originally Posted by Acree

That is absolutely correct. The torque dip has absolutely nothing to do with fueling. It's all about VE of the engine across the rpm band. The torque dip is due to a combination of intake manifold and head design. Otherwise, they would have tuned it out from the factory and we wouldn't be having this discussion.

-Acree

Apart from turbo or supercharging, what would be the best modifications to minimise it or would it be a combination of exhaust, intake and ECU tuning across the board?

On the positive side it gives it character. Even at less than 1/2 throttle it lights up at 5,000rpm giving great performance while literally sipping fuel.

The only way I can think to get more air in there is by blowing it in. A free flowing panel filter will maximise the air at those rpm's.