Longer runners are good for low(er) rpm power - there is a direct correlating loss at high(er) rpm typically. I vaguely recall less impact with e85, so there's something in there that may allow more timing as well. Also don't remember noticing that power blocks do anything with the torque dip. That said, I'd not anticipate it causing timing to be pulled over time. I had a car with dual runners, and the longer runner ran from ~3000-5600rpm and the short runners everywhere else. At low rpm I guess runner length wasn't the primary benefit, but the volume change helped. Short runners were valved, long side not (always open).

I do suspect the torque dip is harmonics related based on the handful of things observed to change it, but I don't have the experience or background to be particularly confident.

I wonder if a dual catted Ace 4-2-1 would perform nearly as well, but that's a wild curiosity that'll never be answered. :)

These Toyota cars were a long time ago. There wasn't any real sports car offering before our platform. Why do you think they contact Subaru? At that time they were selling mainly small cars, hybrids, mini-vans and they had a strong ecological heritage. I don't consider Lexus a performance brand, but mainly a premium or luxury brand. The LFA is an exemption and the motor was developed with the help of Yamaha. So, not entirely a Toyota product.

Right, most of those models ended in the early to mid 2000’s after the Asian market crisis in the late 90’s and then the 2008 market collapse made sure sports cars would be rare, hence sport luxury sedans. The Lexus F line is like BMW’s M line, so pretty sporty, and they have been produced through the sports car hiatus.

Regardless, your point is that going forward Toyota will be producing sports cars with torque dips designed in their motors to give those motors economy and performance. I guess we will see when the new Supra comes out if there is a dip.

Of course the other explanation is that the torque dip is there as a byproduct of the other engineered components, and that the easiest thing to do is to market the dip as an intentional design to maximize fuel efficiency around town.

Longer runners effectively compress the power band, one thing you'll see is the torque dip will get a little narrower, which helps with normal shift points as well as overall less rpm range where the engine is down on power. I suspect the thing with e85 and power blocks is that it can't take advantage of some of the changes as timing can always pretty much be optimal with e85. With pump, timing retard near the top end can be lessened when adding power blocks - above 6500 rpm you're starting to get out of optimal VE, cylinder pressures are less, which gives more room to advance timing from where it was before the blocks. That's where with careful tuning you can regain nearly all the top end losses introduced by the longer runners.

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I don't understand how this is still a discussion?? 100% standard car, remove internals of cat in header and torque dip is gone.

If its tuned correctly the ecu should rarely have to intervene to pull timing, during normal operation with correct fuel

Steve, are you running f.i. now? I'm thinking about doing it eventually and try to follow your posts because you know your business.

I'm pretty sure the new supra is literally a re-skinned BMW M4

They contacted Subaru because they want to minimize their cost and maximize their profits.

Wow... this thread escalated so badly. From header and tune to blaming toyota. To keep on topic, a paper with a graph mean shit to op as long he is pleased on real scenario, in his case autocross. So im waiting patiently for his impressions /video

We are exploring the possible source of the torque dip, while addressing the fact that this header and tune fixes it, while considering other means of sorting out the torque dip. It is not a one dimensional conversation, that is true, but it is good conversation nevertheless.

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Anyone have the other Ace headers dyno tuned side by side?

I'm pretty sure you are dead wrong.

There is a decent chance it will have the B58 inline turbo 6 the current m240i has in it.

Other than that its a new platform that is shared with the z4/5

OH SHIT! Somebody on the internet is wrong.

You are in LA, I'm in LA... Hahahah lets make this happen.

I've owned my fair share of all the popular ones. Tomei, JDL, Nameless.

I've driven others, Ft86speedfactory, Borla, Fujitsubo etc.

I should've changed my statement from all other to just the popular ones. I have not driven some crazy rare japanese headers or every single header out there, but definitely the most popular ones :)