ACE A-350 dyno results - Did it deliver?

[Lantanafrs2]

I would love to see your car dynoed closer to sea level. Seems like they start wheezing when oxygen content is off even a little. Lol

[Irace86.2.0]

I posted this in another thread, but Mazda talks about how high compression motors typically require a torque dip at low rpms to avoid engine knock. High temperatures at low rpms when flow is poorer results in increased knock risk, so they adopted a long 4-2-1 manifold, which increased exhaust flow, lowering temperatures in the cylinder, reducing knock. That allowed for more power at lower rpms through having better flow or through the ability to tune more aggressively or both. The problem is emissions at startup because the catalytic converter takes longer to heat up. They resolved this issue with a piston cavity and a stratified flame front, which allowed for them to safely retard timing.

http://www.mazda.com/en/innovation/t...iv/skyactiv-g/

Obviously this isn’t a concern for anyone removing the precat anyways, but it kinda gives reason behind the torque dip and the “crappy tune” Subaru and Toyota use. And it shouldn’t be a surprise a long 4-2-1 header will make a difference.

[RJasonKlein]

Originally Posted by justinco

From stock to ACE, yes total transformation for sure. From my previous setup to ACE, it is a pretty dang good improvement, but not a transformation.

Understood. I was coming from a completely stock car, and a ‘transformation’ is exactly what I got. @churchx makes a point a few posts back that the low and mid-range bump is probably what’s most noticeable, and in my opinion he’s dead on - the top-end pull is very strong, but the low and mid-range improvement is what makes the car a joy to drive now. Where it used to feel limp and flat, it now swells with torque...so much so, that I often select a gear higher than I would have previously. It’s very, very impressive, that’s all I can say.

[RJasonKlein]

Originally Posted by Summerwolf

I see the midrange difference, obviously. It SHOULD produce more power for the reasons @churchx brings up. I was just surprised the revworks performed so well in comparison (both being tuned for the header used). Would be interested to see a comparison like this to a "better" header. I have read through the whole ACE header thread and never seen a comparison quite like this one.

I agree, it was a very useful comparison.

[CSG Mike]

Originally Posted by Harey

Impressive result! $1700USD though ouch

gains per dollar are actually quote good, when you consider:

- Ace + ecutek cable/dongle + license + tune

vs

- Other header + ecutek cable/dongle + license + tune.

[churchx]

Mike: & .. + overpipe to other header.

[CSG Mike]

Originally Posted by churchx

Mike: & .. + overpipe to other header.

While the overpipe is mandatory with the Ace (and included), I don't consider it mandatory with other headers, although most people with a header also get an aftermarket overpipe, so I totally get where you're going...

[bfrank1972]

Originally Posted by RJasonKlein

Understood. I was coming from a completely stock car, and a ‘transformation’ is exactly what I got. @churchx makes a point a few posts back that the low and mid-range bump is probably what’s most noticeable, and in my opinion he’s dead on - the top-end pull is very strong, but the low and mid-range improvement is what makes the car a joy to drive now. Where it used to feel limp and flat, it now swells with torque...so much so, that I often select a gear higher than I would have previously. It’s very, very impressive, that’s all I can say.

Yup I think a lot of people feel that way about "good" headers in general. A well designed header (of any brand) plus a good time can really transform this car. If you have a pre-optimized tune with tons of time put into it, that's even better, it's a good idea for a header company to partner up with a good tuner for this.

Sent from my SM-N920V using Tapatalk

[gtengr]

Originally Posted by Irace86.2.0

I posted this in another thread, but Mazda talks about how high compression motors typically require a torque dip at low rpms to avoid engine knock. High temperatures at low rpms when flow is poorer results in increased knock risk, so they adopted a long 4-2-1 manifold, which increased exhaust flow, lowering temperatures in the cylinder, reducing knock. That allowed for more power at lower rpms through having better flow or through the ability to tune more aggressively or both. The problem is emissions at startup because the catalytic converter takes longer to heat up. They resolved this issue with a piston cavity and a stratified flame front, which allowed for them to safely retard timing.

http://www.mazda.com/en/innovation/t...iv/skyactiv-g/

Obviously this isn’t a concern for anyone removing the precat anyways, but it kinda gives reason behind the torque dip and the “crappy tune” Subaru and Toyota use. And it shouldn’t be a surprise a long 4-2-1 header will make a difference.

It's not really the same thing as the FA20. The sky-g doesn't really have a huge dip, it's more of a delayed onset of torque. The FA20 makes nearly peak torque very early, crashes hard, then comes back up to actual peak. The skyactive g also has much more compression (14:1) than the FA20, so if compression was a key factor to the dip then the sky-g should have it even worse.

[Lantanafrs2]

Imo that revworks tune was well done. Probably some still to be had with the ace.

[bfrank1972]

Originally Posted by Lantanafrs2

Imo that revworks tune was well done. Probably some still to be had with the ace.

I'd agree overall - although that top end drops like a rock, that doesn't look quite normal to me.

[Irace86.2.0]

Originally Posted by gtengr

It's not really the same thing as the FA20. The sky-g doesn't really have a huge dip, it's more of a delayed onset of torque. The FA20 makes nearly peak torque very early, crashes hard, then comes back up to actual peak. The skyactive g also has much more compression (14:1) than the FA20, so if compression was a key factor to the dip then the sky-g should have it even worse.

Right, so, the SkyActivG is an inline 4 vs a flat four, with a different firing order, balancing characteristics, and probably a number of other factors. The firing order alone would make for a difference in exhaust characteristics, which could explain the difference between a torque dip and a torque delay. Regardless, your last statement was confusing...

The skyactive g also has much more compression (14:1) than the FA20, so if compression was a key factor to the dip then the sky-g should have it even worse.

It seems like you didn't read the article in my link and/or missed the point completely. Mazda's engine doesn't have a dip/delay because they managed the inherent problem that exists with high compression engines, which is what their article was addressing:

In summary...

-The world’s first gasoline engine for mass production vehicles to achieve a high compression ratio of 14.0:1
-Improved everyday driving thanks to increased torque at low- to mid-engine speeds
-A 4-2-1 exhaust system, cavity pistons, multihole injectors and other innovations enable the high compression ratio

Some detailed quotes...

However, one of the reasons preventing the spread of high compression ratio gas engines is the large torque drop due to knocking (Fig.1).

Knocking is abnormal combustion in which the air-fuel mixture ignites prematurely due to exposure to high temperature

This reduction of residual gas was focused on for SKYACTIV-G, enabling the realization of a high compression ratio gasoline engine.

One option to significantly reduce residual gas is the adoption of a 4-2-1 exhaust system

Again, read the article, but essentially they used a number of different features to eliminate the risk of knock, which allowed for them to make a really high compression motor that doesn't have of any torque dips/delays.

[gtengr]

Originally Posted by Irace86.2.0

Again, read the article, but essentially they used a number of different features to eliminate the risk of knock, which allowed for them to make a really high compression motor that doesn't have of any torque dips/delays.

Right, but the assertion that high compression has a strong correlation to the FA20's dip is still off base. You're relying on Mazda's very simple comment about a "drop" to mean a "dip" when they could mean that the torque drops off altogether in lower rpms, which is the more plausible scenario with extremely high compression, 87 octane, and low rpm knock problems. Look at something like the BMW S65. It has high compression, port-only injection, and 4-1 headers and it's one of the flattest NA torque curves out there. This is probably not the thread for continuing this tangent, but if you'd like to discuss more I'd be glad to in your engine thread.

[NoHaveMSG]

That chart looks way better then the ones that I have seen for the nameless header, and what my butt feels.