First a little background on what I am doing. I race an FC in basically World Challenge trim in the Touring GT Series here in Ontario. We have had some success, but always a bit down on power. Been held back a bit over the last year or so with my bone stock, though new, S5 Mazda Reman motor. Last spring the engine ate up its bearings due to a combination of too much throttle on really cold oil (less than 150 degrees oil and water) and the fact that it was pulling over a G in cornering loads. Gotta love co-drivers. Anyways the time has come to rebuild this motor and give it more pop.

So this is the new package. The engine will be a half bridge on the outer 5th and 6th ports using the new S5 housings. All other ports will be a large street port. I will not be using the sleeve inserts, but will be using a larger wedge (like a Pineapple insert). The exhaust will be a large Racing Beat Street port. I will be using clipped S5 rotors and FD Bearings. A bit of discussion is taking place on 2 piece or Racing Beat 1 piece carbon seals. The exhaust is a Racing Beat Road Race header with 120 inch primaries merging into a single 3 inch pipe through a Borla muffler.

The intake will be created using Hayabusa throttle bodies (46mm) with 30 mm velocity stacks drawing from a cold airbox drawing from in front of the front fascia. I will be creating the intake from a 1 inch thick motor flange that will be flowed from a 50mm pipe to the motor's port diameter. The intake stubs will be mandrel bent at a 45 degree angle (to clear the shock tower) to allow me to reach a 11 to 13 inch intake runner length. I will be using the stock S4 fuel rails (primary and secondary) and have both the stock 460's and 550's available to run.

Enough background I think. The question I have is how do I tune this? All the throttle bodies will open at once so do I still use the dual stage map. I only want to pull 8500 rpm and operate at full throttle about 80% of the time and rarely, if ever, ask the engine to pull below 4,000 rpm. I will be using the MS N S Extra setup with the stock RX7 coils and ignitors as well as the CAS, again thanks to Renns, Muythaibar and all for all of their hard work and skill.

I have an electrical engineer on my team, as well as a crew chief with over 20 years of race experience, so I am not concerned with reliability, just tuning. Looking for your ideas on the best way to get this handled and mapped so we don't waste a bunch of dyno time trying to work out basic issues.

Thanks in advance.

Eric

(hoping to drag Bill Shurvington out of the woods for his advice as well)

 

I don't know how you'd go about calculating a table with those parameters on a ported rotary, but I would think the base timing map should work to get you started. What HP are you looking to get out of it? 250 at the crank? Are 550s enough for that?
With ITBs, the only advice I can think of is to use MAPdot accel. enrichment and your accel time parameter may need some additional tuning..

 

Thanks for the advice. I am looking to create at least 200 rwhp or 230hp at the eccentric shaft. Anything more will be a welcome bonus and means I can just go faster. Yeah, no more massive outbraving efforts, just stomp past on the straight.

My main concerns are just as you stated, are the 460's enough to fuel this and do I need a staged delivery or should I just fire both to each chamber at once with the fuel level or pulsewidth cut in half? I know that this is more theoretical but my existing throttlebody was modified to open primary and secondaries at the same time and the stock Mazda S4 ECU worked fine.

 

Eric,

You could try batch-firing all four injectors, but you may have trouble at idle. I'd suggest setting up staged injection, and fire primaries only at low power settings as most others are doing. On the track you'll be running continuously above the staging point anyways, so the transition is of no consequence. The plus side is that when you come off the track you'll have a pulse width on primaries only that's high enough to tune a decent idle.

As for injector size, 460's won't cut it at that hp and rpm. I'd recommend using a set of high impedance 550's, or low impedance with the stock Mazda resistor pack. Add an Innovate LC-1 wideband or equivalent, and your tuning should come together very quickly. Plan on adding a full-span TPS while you are fabricating the custom TB/intake. You could get away without it, but it's likely much easier to add now than later.

If you haven't already purchased, get the V3.0 board and kit, and knock opposite teeth off the 24-tooth CAS wheel. That'll give you the most straightforward, and reliable install. Be aware, though, that there aren't many people running the FC ignition via MS yet. I've got many 1000's of miles on MS running fuel and spark, but it's using my own custom coil-per-plug setup. The stock FC setup is simpler by far. Hopefully there'll be some serious in-car testing starting soon.

I've still got an FC CAS/coil test setup in my shop that can be used to simulate all inputs including the CAS signal. Drop me a line if you'd like to give your box a run on the bench prior to sticking it in the car.

Roger.

 

any more updates on this? i'm interested to see how this works out

 

renns: We have thousands of miles on the stock FC system with the MS. It's pretty well tested. Tofuball uses it in his daily driver, and aside from his own tuning mistakes, it has been very reliable.

23racer: I agree completely with the rest of what renns said.

 

Just a quick update. We are still fabbing the intake and we got the daughterboard stuff from Glen's Garage and the velocity stacks from Orient Express. I will be picking up the Filter medium sometime this week. I have been very busy with real work (just got back from LA, visited Racing Beat), making a new glass hood mould, racing the Cobra R and family life.......I know, I know burn candle at both ends, blah blah blah..... We hope to have the intake fully welded up by mid April and be over at Renns to check out the Megasquirt we assembled on his bench top. Renns is a great guy, very willing to help. Hopefully we can place a base map in the 'squirt to get the car running so we can tune it.

Once that is done then a quick install and off to the dyno for tuning. Feds has offered his WB O2 sensor to help in the tuning process. Thanks for the tip as I am planning on using some TII injectors we have to give us the duty cycle margin we need.

We just have to get our collective finger out and get moving. The target is to have the intake on the mule motor by the end of April and to the dyno as soon as possible after that. We also need a test day before the first race over the May 22nd weekend

Eric