I am looking to optimize the power/torque of the GTUs. It’s a toy, driven weekends, occasional autox or track day event.

Engine:
- 15k on Rotary Resurrection build
- Mild ‘6-port streetport’
- 3rd gen housings
- pineapple racing inserts
- stock air pump actuating 5/6 ports
- ‘cold air box’ with Apexi air filter on MAF
- RB header, dual RB exhaust all the way back, no cats
- Mallory HyFire 6 CDI ignition box (same as Jacobs IIRC)
- SAFC (1st gen iirc)
- T2 fuel pump
- Wideband O2 sensor just after the header, before the presilencers, on 1 rotor only
- Tuning consisting of 3rd gear WOT pulls on the street (holding the car with the brakes), aiming for about 13 AFR from about 4000rpm up. This is based on old threads on this forum. Worked out to 10-18% fuel reduction, it was running 11’s before the tune.

Motor seems to be in very good condition, no intake leaks, smooth idle etc. No 3800 rpm hesitation, nice feel @ 5800rpm as the 5/6 ports open. Good plugs, wires, filters, etc.

Anything else I can do to maximize the engine potential, working with what I’ve got?

- I’ve seen a lot of Rtek threads recently – worth going to Rteck vs. sticking with SAFC?
- p.o. included a modded intake manifold, some butterflies removed I assume. Worth investigating? I hear this can help top end at expense of bottom end and smoothness.
- Timing: I have not checked or adjusted. p.o. was a detail freak and I suspect it is set to stock per FSM. I’ve heard S5 does not respond much to timing.
- Thinner oil: currently running GTX 20w50, I hear going to 10w30 is ok. We have hot summers so this makes me nervous. How much potential does this really have? I am running stock OMP plus premix
- Anything else to consider before some dyno pulls? I'm reasonably close to Rotary Performance, was planning to use them.

Glad to see a few NA tuning threads here recently. I was afraid we were a dying breed

 

1. the Rtek might be nice, give you control of timing and fuel. you're getting 90% of the gain with the SAFC, but there is a little more on the table.

2. intake might be worth looking at, depends on what they did.

3. i've advanced the timing on a few of the S5's NA's ive had and they actually will ping a little in the midrange, and not gain anything up top. also the stock timing map has surfaced, so we know it runs 26 BTDC up top, which is basically what we ran in the race car which was dyno tuned with a full ecu. that being said there might be some gains at part throttle and in the midrange, especially if you remove the 6 ports and VDI.

4. Idemitsu did a full oil study, and there is a reasonable gain with lower viscosity oil, however wear goes up, so you have to balance the two. they were doing Lemans, so they picked the heavy oil with no wear, but in a street car, which makes less power AND sees less load, you could pick an oil that wears more. the Rx8 runs 5w-20, without problems too.



5. other things? the port match from the FC exhaust port to the RB header is horrible. the exhaust port is actually too big, but its much easier to just port the header a little. other than that i'd just hit the dyno. since you have CDI ignition start with the car rich, and see what it likes. you could try either the race or the Rx8 spark plugs too.

 

I saw the mismatch picture from the RB header to the exhaust port somewhere. Is there enough meat to open it up enough or is it a case of building new headers?

Eric

 

Thanks or the info, much appreciated. I will probably stick with the SAFC - doesn't sound like it's very cost effective to go to Rtek to chase the last couple hp. Probably stick with thickish oil as well, just for peace of mind. Maybe move down to 10w30 or so. I run Castrol 'German' 0w30 Synth in the piston cars and like it a lot, but would not run synth in the 7 without disabling the OMP.

Port matching the header: this motor has 3rd gen housings. make a difference?

Sounds like it's dyno time! I'd like to see what some rotorheads who do this for a living think of the car.

Track day the 16th, I'll see if I can have it done by then

 

i understand that this is nitpicking a general statement, so i hope offense is not taken, but there are problems with the thinner oil. from all the stuff i've read it's generally long-term, but it exists - at least with the Series 1 cars. personally, i wouldn't run less than 10W40. me, myself, i run the diesel 15W40 in my rotaries.

fortunately, my engine is still going strong at 80,000+ (but unfortunately my pockets are not) so i haven't pulled mine apart to see, but i saw a few photos of others and while i'm sure many people are revving the **** out of these Renesis' motors, i think Mazda is partially at fault, too.

 

yep, plenty of meat to give a nice bevel. ideally the exhaust sleeve is too big, but its just simpler to match the header.

nope, still a 48mm hole into a 44mm pipe....

well the trade off with lighter oil is better fuel economy vs bearing wear. in the race car (787B) they chose no wear, and no fuel economy. for the Rx8 they seem to have chosen fuel economy and were willing to accept some wear.

i would have done the same i think, and we're used to pulling apart 150K engines and seeing the bearings in good shape, but maybe with the Rx8 we pull apart a 150k engine and its worn out....

 

Dyno tuning went well!
It was running a bit ragged due to fuel pump o-ring misplacement and lowish fuel pressure (my bad). They fixed the issue, played with timing and pulling fuel out using the safc, and yeilded 158hp/120tq. Not bad. other than the fuel pump issue, they said the car is really well sorted, very solid. Good to hear.



This is before and after tuning.


Plans are to extrude hone and remove 2nd throttle plates from intake, and do a little port matching on the header. They said it could be good for anothe 8-12hp. I think that's as far as I'll go.

 

good job!

 

TB Mod:

Worth it or not? There is a lot of conflicting info on the site...

I have a spare stock TB and gasket set. Rotary Perf. suggested removing throttle plates and extrude hone, I'd leave BAC, thermowax etc alone. I don't want to do it unless worth it.

 

i'd remove the second set of throttle plates and call it done, gains are really small

 

yes, less parts to fail, miniscule power gains (if any) but 100% throttle response improvement.

 

I am going back to RP next week to dyno tune again. The plastic t-stat neck broke on a 110F track day, instant overheat, rebuild by Kevin Landers.

Engine now has a 'full' 6 port streetport instead of just 5/6ports, port matched the RB header, and removed 2nd throttle plates.

Care to guess what the dyno will say? Hoping 170, 175 would be awesome, 180 would be heavenly. It feels pretty stout.

 

I would hope in the 180's. My S4 I unprofessionally built and ported made 185 at the wheels and has room for improvement