as our FDs start their fourth decade, if they have been driven, a single turbo system makes more and more sense. not necessarily from the go faster concept, but primarily for the benefits of replacing the cracked and poorly designed turbo manifolding. single turbo equals less backpressure and a happier motor.

in the "while you are at it" category take a good look at the dreadful OE lower intake manifold. most 13BREW internal failures occur in the rear rotor area. not helping the situation is the OE LIM. even a quick look at it leads one to conclude the concept of equal flow to the two rotors is folly.

Xcessive offers significant help for the rear rotor.

availability has been spotty over the years but things are on the uptick. the company is doing well and recently moved to new quarters and has uprated their casting capability both from a quality and volume aspect. i can vouch for the quality improvement... i received two for engine customers yesterday. better finish and a bit less need for some finish porting.

Full Function Engineering is the sole distributor. if you want an Xcessive LIM i suggest you call FFE and get on the list. i paid regular retail for each manifold (currently $695) so i am presenting this info simply to be of help to the community..

 

The amount of material I had to remove to match my 20B Xcessive manifold was absolutely bonkers for a a 'performance' product. I wish I had before and after photos but it was probably in the realm of dropping it down .25 on every port and then hogging out the actual runners a pretty significant amount for me to feel comfortable using it as an 'upgrade'.

That said, I really do like the fixes to the FD runners - and I hope either I got a one off mistake, or they've fixed the casting process/mould on the 'short' 20B manifolds (I'm assuming this isn't an issue with the FDs as well due to the glowing reviews)

 

^^“Excessive” might apply in some regards

I can see why people might have wanted to stick with an OE style manifold back in the day, but an going to suggest there’s a missed opportunity sticking with it now. People go on about the original secondary resonance feature and such, but what was applicable on the twins with the factory staged TB is pretty much out the window on a single turbo and a single open inlet TB as is prevalent now

Even the Turblown version still in progress is missing the boat some from my own perspective. It was recognized at one point, but seems to have been lost in history and is not that unusual of a situation really. Below is a custom Tri-Point Eng. manifold from the past that demonstrates a different perspective. It was used in a chassis that could accommodate the secondary piping as indicated with the long plenum. The plenum itself is not ideal wrt to the TB and distribution. Swinging the secondaries in towards the primaries like on the Xcessive/Elite/etc UIMs is easy enough and so is a better plenum/TB design.

I’m not in anyway suggesting that in this form it’s ideal, only that it points toward a direction to consider for those who might be less inclined to the herding instinct …




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i just returned from looking at the manifold from a "does it need to be ported" aspect and am very impressed. all prior manifolds that passed thru my hands did need, and get, some port work.

not so here... since i find it hard to leave things be i will be spending less than half an hour on each manifold but they are significantly improved. you could easily decide to run them right out of the box.

 

The issue with these is that the non cast runners take up a lot of real estate. That's why the cast really shines.

 

Should change the title to Xcessive AND Excessive. I have some welding to do haha. You’ll also notice I’m doing the opposite of what Howard needs these for. I’m actually restricting the 2 end runners down to the size of all the other runners so I get equal flow.

 

The stock 13B-REW is bad, That is why I basically went through the complete intake and port matched and lightly polished all to remove the gross casting errors.

 

I had the same problem, they used the FD port on the 20B manifold. They told me they were changing the mold so I sent it back and waited on a new one. That arrived, it was better but still needed porting . I talked about 14 years ago in this thread https://www.rx7club.com/20b-forum-95...d-lim-1011598/

original vs OEM, ports were REW

 

Thanks for letting me know I wasn't being overly persnickety

 

yeah, 20B would be the Cosmo port that comes in steeper and then appears to larger due to the longer cross cut

funny enough I just stumbled across this, which is on a 26B, and is pretty much how I suggested to Twin Charged in his build thread, including splitting an elbow & pipe down the centerline to fabricate the plenum exactly as shown in this pic. For a 13B I’d just bring the outer secondary tubes in toward the primary tubes similar to the excessively Xcessive et al manifolds for a more compact fitment relative to the firewall. Note the oil fill tube as well.


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and no, it doesn’t really take up much more area than a cast manifold, that comes down to how it’s fabricated. Hope to demonstrate it in the future, God willing …
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this was interesting

https://www.mdpi.com/sustainability/...15809-g007.png

in summary; D/L = 0.6 provided the best rotary intake result, while 0.8 was the worst


Conical entrance into wankel intake port
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inlet cone angle vs intake cycle rotor position, middle 0.6 angle is best, 0.8 angle on right is worst.
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That does look interesting, but it's probably best to link to the entire paper. https://www.mdpi.com/2071-1050/14/23/15809
As best as I can tell, they are relying very heavily on simulation results with very little experimental validation. They are making a lot of claims based on computer models, which can be helpful if the models are proven to be accurate. But generally the best way to perform research like that is to build at least two prototypes to confirm that the 'best performance' and 'average performance' simulation results reflect reality. Also, their simulated engine looks to have peripheral intake ports while the Excessive LIM is designed to work with factory intake ports.

 

re: last half of last sentence - that’s kind of arguable imo … Omar at RaceOnly has stated otherwise against the Mazda LIM based on his own dyno results in the single turbo forum area. I’ve seen a lot of evidence that indicates better performance gains hogging the REW ports out to the Cosmo sizes.
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What I meant in the last half of my last sentence is the Xcessive LIM is not designed for fully peripheral-ported engines. The research paper you referenced is modeling a peripheral-ported engine without any side intake ports.
It's still very interesting and I agree the concept of tapering the runners near the intake ports seems like a good idea. If you haven't seen this set of videos, I think it's very interesting that he pulled a mold/plug of the intake port for various Mazda engine generations in order to find the cross-sectional area.

 

the misunderstanding was my error, thank you for clarifying.

yes, I saw those videos way back when they came out. I believe they were all centered around NA use the same as the study we’re discussing, but there is information for turbo that can be gleaned from them both.

the comment I referenced:

https://www.rx7club.com/single-turbo.../#post12562954
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Checking in 5 months later, all mentions of the 13b and 20b lower intake manifolds have been removed from Xcessive's site as well as FFE and every other distributor. Are they officially done with these? It would suck because I was really in need of one for my REW, maybe @Howard Coleman can provide more insight as it seems like you were at least somewhat close with them over at Xcessive?

 

Just call them. They are pretty responsive.