As for the injectors, that has been covered previously in the thread. If you do want to run staged like factory, you need to fabricate a fuel rail and purchase the injector bung to be welded on to your manifold or wherever you choose to mount them.


Also, you need a different intake manifold such as RB. Something that has a weber carb style flange.

 

My question wasn't on how to run them. It was if it effected anyway the car ran. If it would be any different from stock etc.


I know, I was just double checking the RHD listing.

I was looking at keeping the 6-port lower and using a RB upper.

 

Driving is a blast, my half assed tune runs well enough for me to drive where ever I want. I need some tweeks but over all it hauls ***.

 

It makes for better drivability. You can't allow the bridges to get a lot of vacuum, which is what would happen if you drove it on the primaries with the secondaries shut. Tnen you would get a lot of exhaust gas pulled up.

I proved this years ago with my half bridge engines where I modified the (stock FC) throttle body to mostly idle on the secondary side.

My current engine is a full bridge and all four throttles open equally. Drivability is excellent.


notes: Lots of clutch slip because it had been raining, I was limping home with a broken axle, and my street tires are ten year old all-seasons that are hard like granite. And I was towing ~600lb worth of trailer. So I was trying very hard to not let the tire spin. As it was, any slight incline was difficult and I actually got stuck at one point. So I was driving with just the bare amount of throttle needed to accelerate gently. But remember, bridge ports are awful beasts that don't make any power below 5000rpm and idle at 2000 and can't be driven on the street...

 

Peejay, I just love how you use the heel of your right hand to shift into 1st when you release the hill holder arm (at least that's what I think it is). Great dexterity, LOL!

Car runs very smooth.

Eric

 

I would love a close up of your throttle bracket. Mine doesn't keep enough tension on the cable.

 

This is my intake that I'm starting to fab will have the runners on in a few days. But it a start on the flang porting it down

 

Very nice! Looking forward to the progress.

 

Well got around to getting abit more done

 

Nice, I needed this thread. Im about to order the Borla ITB kit. It seems reasonable in price plus I don't have to ship something from AUS. I wanted to know if anyone has welded an injector boss into the racing beat manifold and how was the performance. as previously stated on this thread it may be better to have the primaries close to the port?

 

What sort of realistic power gains are we looking at with ITB's ? Can it match the numbers the 13B-RE Cosmo engines can put out and what kind of porting is recommended ? I have a 91 GXL currently and while 200 rwhp would be nice 180ish rwhp would make me seriously consider this mod.

 

ITBs don't really add peak power, but they are great for drivability with heavily ported engines since they keep intake reversion from killing chamber filling at low RPM/low throttle opening. They also are great for keeping exhaust gases from blowing up the intake during the overlap period on a heavily ported engine, again at low RPM/small throttle opening conditions.

A plenum manifold with a single throttle body is best for big power but you lose low throttle drivability.

My full bridge is MORE DRIVABLE than any plenum manifold street port or half bridge engine I've had!

 

Peejay, I totally agree on the driveability part. Ever since I put the 4 throat ITB's on, the throttle response has been immediate and the torque at lower rpm has been far better. I tried to compensate some on the more power side by using 4x50mm throats. The car really hauls with this setup. I can't compare to a single body setup as I never had the car on one.

Eric

 

To all running ITB's, how is your gas mileage? My afrs seem good and I'm averaging 12.5 mpg all highway. City is terrible lol. I know, I know, I own an rx7. However, I remember reading somewhere that better fuel economy was possible. Any thoughts?

 

I generally see 18-22mpg highway depending on the weather, but I've seen around 29mpg under perfect conditions (HOT, flat Michigan roads not Ohio hills) When the engine was new I barely had time to break it in and get it rough tuned and then it was off on a near 1000mi trip to Tulsa and I would get 300mi for every 12-13 gallon tank of fuel.

This is the full bridge 13B 4-port with 4.78s, and true mileage not the way-incorrect odometer readings.

Something is seriously amiss if you're only getting 12mpg! What is "good AFRs"? With a stockport or even streetport I could cruise at around 15-16:1 before it would lean misfire, with the bridge it is a solid "it depends" and at light load it needs as rich as 12:1 but as I feed in more throttle it is happier at 14-15:1. Where is your ignition timing? Are you running any kind of vacuum/low-load advance like you should be doing? Why not?

 

That's a great question. Afrs under cruise are around 13.5-14. WOT is in the 11.4 region. Idle is high 11's usually.

Timing is as follows:

 

If it will run cleanly with a leaner air/fuel, trying pulling some fuel out. But if the engine ever feels like it's starting to stutter every now and then, putthe fuel right back. Misfires waste fuel, and they also train you to drive through the weak points. That is why I'm as rich as 12:1 under really light loads, that is what it takes to keep it from missing every now and then when the engine is choking on its own exhaust gases Running leaner makes it start to stumble and stumbling is fuel thrown out the tailpipe.

If I am reading this right you are cruising at 35-38 degrees. That seems a little HIGH to me, with N/A rotors anyway, it might be worth driving steady state and pulling timing out and seeing what that does for the real duty cycle to maintain a 65mph cruise or whatever. The trick is you also need to tune the areas around that, if you pull timing away, you will also have less vacuum, so you'll be in a different cell...

Basically a lot of experimentation is in order. Don't feed the engine an arbitrary number, feed it what makes it happy. (And IMO 11.anything is waaaay rich for N/A at WOT... I thought I was running silly rich at 12.5:1!)

 

Pulled some more fuel out of the richer areas and the car still runs fine. I was under the impression that 11-12 afr at WOT was ideal? I can definitely lean it up more.

As for the timing, that's what I thought was curious. I'm not sure I was reading it correctly as my text engine data page shows that it never goes above 27 degrees. So, I'm unclear on how the text view correlates. Timing is one of the things that I'm hesitant to adjust myself.

 

That's definitely curious... I'm unfamiliar with whatever computer you are using, so I don't know if there is an additional map of multipliers or offsets or something. 27-30 degrees at cruise sounds about right from my timing experiments on stock/street port engines. (Bridges are... odd... and I'll leave it at that. Certain not necessarily intuitive things happen)

I have "heard" that if you have proper atomization and injection timing, you can make best power right up close to stoich on a rotary. I would hate to see what the EGTs look like though. But you don't have to worry about melting a piston or taco-ing an exhaust valve or three, so there's that. I found a minimal power difference between 12.5 and 13.5 so I run towards the richer end to hopefully keep the engine a little cooler at WOT.

 

Good info. I leaned out the map a bit and we'll see if mileage improves. And hopefully power.

 

I also realized that I don't have close loop enabled. Probably not helping the fuel economy.

 

I've never used it. If the tune is good, you don't really need it.

 

Meh. There's to false hope lol

 

I just realized that I'm calculating my mileage based off of a full 16 gallon tank. Assuming that I never get the tank completely full, I'm wondering if I should base this off mileage. With a "full" tank, I'm getting 200 miles. This is mostly highway with some city. When I'm driving primarily city, I usually get around 150.

 

Dude, you fill up and record milage (or just hit the trip odometer, if so equipped), then the next time you fill up you look at the pump for the gallons it took to fill, record new mileage on odometer, and divide the difference in the od readings by the gallons to fill. Best to do over a few fill-ups and average. If you frequent the same gas station by habit, try to use the same pump each time to get a very accurate combined mileage number.