12a rotary, a GSXR TB and megasquirt?

[Rallywagon]

Hey everyone. I'm hoping to pick some peoples brains. I am hoping some tuners hang around these parts that are as savvy as some of the computer guys here.
Here is the skiny, I have an 85 Rx-7 with a 12a that I will be making a custom FI TBI for. I plan on getting an intake flange from RB, some peices of tube for runners, which I will cut and bend to mimic the length of a weber DCOE intake, then attach the throttle bodies from a liter bike, either a GSXR or Busa. I'll be using a megasquirt as the ECU.
So, I was wondering if anyone here has experience with tuning any sort of engine using both or either a megasquirt or aftermarket TBI. I think there are only like 2 rotaries done in this fashion, both 13b's, so I'll be venturing into some unknown waters. But an knowledge would be useful, particularly tuning with MS with ITB.

 

[Eunos_Cosmo]

Extremely unlikely anyone on here will be able to offer any insight.

You might message this guy, he's on rx7 club too, but I can't recall his screen name.



Aside from that, perhaps try http://www.nopistons.com/ or http://www.rx7club.com/

 

[Rallywagon]

yeah, I am a member of Rx-7club. think I went over ten years as a member there a couple months ago. I've searched there,a couple of threads were made, but no one really knew much, other than "this guy did that, but I don't know where or who" or the always outstanding "why would you want to do that, just do this instead." maybe I should hop onto nopistons though. The have a better crowd I believe. Got a feeling I'll be "pioneering" this one. I was hoping mosting just to find someone that perhaps has set one up on a old VW or honda or something, to pick their brain on tuning a GSXR type intake. I know it is far more common to find them on those sort of cars. Such as like this one...

 

[niky]

Some experience tweaking maps... but building a map completely from scratch? That will take a hell of a lot of time.

If your car was already EFI, it would be simpler. You'd simply have to adjust the signal from a custom-fitted MAP sensor to match the output of the stock MAF. Something you can do with an emulator.

Doing it completely custom means writing the entire map from scratch, which can take weeks or months to perfect.

Then there's trumpet (venturi) dimensions and design to consider, yada yada yada... if I were you, I'd stick with carbs. But then, I'm chicken.

 

[Rallywagon]

No sticking to carbs for this guy. I've modified the stock nikki, replaced with weber DCOE's, ran a holley, time for something new. the venturis aren't quite as important in a TBI as it is in a carb. Though it is my understanding that most liter bikes run somewhere between 28 and 32mm. Should be just fine. Maybe I should hit up the megasquirt forum. Didn't think about that. The trumpet, at least that as I know it, is separate from the venturi, its the horn looking part on the top of the carb. The venturi is a sleeve of sorts that fits into the carb barrel. I won't be running trumpets, but rather, will be building, or finding and modifying a plenum. Once I get the engine running N/A, I plan on boosting the car. Another reason I want to run EFI. Sealing carbs sucks.

 

[TouringBubble]

I helped a friend set up an MS3 on his FC a while back. We were both kinda learning at the time, so I can't remember exactly where we ended up. I know he went MS3 so he could run a secondary trigger to simulate a cam angle sensor. He also ended up going with sequential injection in order to get the staged injectors to function properly.

We went back and forth a lot on how to set up the ignition and fuel based on the rotation of each rotor. I don't remember all of the conversations, but you essentially have two 360º motors working as one 720º motor, which is confusing as anything to wrap your head around. I can ask him about his settings and such. I'm sure he still has a map or two saved on his computer.

His car was already EFI, so he had the EFI manifold with primary and secondary injectors. From what I know ... and that's not much ... primary and secondary injectors are nearly required on a Wankel rotary to cope with the large VE shifts from idle to high RPM. The primaries are smaller and deal with idle cruise well, then secondaries kick in at higher RPM to pick up where the primaries can't handle it.

The Megasquirt forums are good for learning. From what I know, one of the original founder of the MS project is a rotary guy, so there is some support there.

Running ITBs is going to cause some issues with getting a common vacuum source to reference for the MAP signal. You could get a vacuum manifold and source vacuum from each runner to get a common reading and facilitate a little flow balancing.

You are correct on venturi v. trumpet. TBs shouldn't have venturis. The venturi, I believe, is the part of the carb that increases fuel flow as intake speeds rise. Air passes over it and pulls a vacuum, causing more fuel to be delivered. The trumpet is there to smooth airflow in to the carb/TB. Both a carb and throttle body can have intake trumpets, but only the carb has a venturi.

One thing to consider ... how to you plan to route air from a turbo to the ITB setup in the future? You'd have to build a manifold of some sort to make that happen, negating several of the gains of the ITB setup in the first place. You still get throttle control on each individual runner, but routing throttle cables and such to the TBs inside a sealed chamber to hold pressurized air is a pain. The trumpets are nearly negated as well as you are then forcing in air and not relying on the trumpet to smooth the air pulled in from the engine.