John V

Hi guys,



I'm in the planning phase of a Prepared-class autocross car that will see zero street use. Because of the class rules, the most effective motor will end up being a 13B PP. I've never built a PP motor before and have only built a couple of stock side port motors. The car has to weigh 1,962lbs with this motor. Comparable cars in class weigh 2100lbs and make about 250hp to the wheels.



My thoughts so far are as follows:



New racing beat peripheral housings

New stock Mazda intermediate and end housings (with ports filled)

RB lightened and side-clearanced rotors

New stock RX-8 E-shaft

5.5" clutch and flywheel with the entire rotating assembly balanced

RB machined and heat treated stat gears

Custom slide throttles

MoTeC or other aftermarket EFI

Not planning on going dry-sump since autocross doesn't have many sustained cornering events.



This motor will normally be operated from 6,000-9,500 RPM with an occasional trip to 10,000 as dictated by course design.





* What apex seals and springs should be used? I've heard everything from using Rotary Aviation seals to stock Mazda seals to RB Carbons to Ianetti ceramics.

* What intake runner length should be used? What kind of torque output can I expect?

* I have to meet a sound limit of 100 dBA at 75'. How many and what type mufflers will I likely have to run?

* Are there any particular things different about assembling one of these motors versus a stock motor?

* Any particular oil system mods that need to be done?



hoping some of you experienced folks can help me out. Thanks very much,



John V

fc3sboy1

dont bother waisting the money on the RB gears, just use the rx8 gears they are hardend and multi window and clearanced from mazda. as far as apex seals i have had great luck with 2mm NRS ceramic seals or the ceramic seals from mazda motorsports wich are Einettis or how ever you spell his name. i sugest if using the mazda motorsports ceramics to get the NRS spring kit though as they are more durable and wont ware the bottom side of the seal near as bad.



also with your induction system, read the rule book very closly on that because you may be forced to a limited size ie 42mm or something. and also read and make sure your allowed to use aftermarket rotor housings ie the machined and built RB housings and not the MFR housings. I had read a stupid rule someplace in a SCCA GCR about the housings at one time and dont know if that rule will apply to you or if it was even lifted since then.



a very well prepped 13bPP can make well over 350hp and have a bunch of rpm so this is why i question the rule with your competion being 2100# and 250hp.



randy

fc3sboy1

also about your 100db noise restriction, we have be under 103db with the EP car owerselves and what we do is run 2 inline mufflers and angle the tip slighly down and to the right facing away from the sound test equipment that all tracks have on drivers left.

John V

Thanks for the tips, especially with regard to the RX-8 stat gears. As for the housings, the RB housings are legal but the MFR ones are not.



I do not have an inlet restrictor requirement under my rule set. The rules regulate vehicle weight by limiting displacement. A side port intake rotary is listed as 2616cc and the factor is 0.7 so min weight is 1831, but gets bumped to 1900 as that is the class minimum. For a peripheral port motor it's 0.75 * 2616 = 1962 lbs.



John

Maxt

Even FC stat gears are good to 11,000 rpm. You can use the production oiling system with an FD oil pressure regulator, you need to run a baffle plate in the oil pan though to de-air the oil and maintain oil pressure. I have been running stock steel seals, they make power up to 10,200. The carbon seals are the most cost effective. I think you will find that on the track you are going to want your shift rpm to not drop you below 7500 rpm. I always got my fastest track times running the car above 7500 to 10,000. You will have a hard time making power and keeping it quiet. My car with 2 mufflers was 116 db at the starting line at 2000 rpm,, putting the baffles back in the muffler killed 30 rwhp. Realistic real hp for a 2 rotor p-port in a track legal configuration built with non exotic parts is probably 200-225 rwhp max. Keep in mind even the mazdaspeed prepared 13b p-ports were 300-310ps FLYWHEEL with no accessories driven and open header. Chassis dyno numbers are so damned random, you can't really go by whats out there for numbers as real world comparisons as I know on my own dyno I could have made more power and more impressive dyno sheet just by changing the rear wheels.

Long intake runner works better for a corked up exhaust, Short runner for uncorked. If your noise is an issue I would actually consider running a renesis motor, sadly, corked up they will make more power than a p-port.

John V

Hm. That's pretty different from some of the experts I've talked to on the subject. None of them have said the stock seals will track well past 8500 RPM, and none of them have said the power will drop that severely when properly muffled. I'm not expecting it to be quiet - 100dBA is not quiet.



Was hoping Mr. Hanover would weigh in on this topic, I assume his interest in aviation has had him building at least one peripheral intake motor.

Maxt

Hmm, I dunno what these experts are experts on then, mazda wrote enough papers on Pport exhaust results , it should be common knowledge. I tested it on my dyno to see what mufflers and backpressure does, and mazda is right, it just kills power, fast and hard... If it werent so, you still see alot more rotaries raceing, not being able to be competitive and quiet is what kicked rotary racing in the groin.

The stock seals are good balance between price and life, the carbon are not bad, but they take no abuse. I don't see a torque drop off with the stock seals till 10,000 rpm, its also about how you clearance them to. Re amemiya uses the stock seals in his 20 b pport in super gt, he doesn't rev to 10000, but it does over 9k. If you have a grand spare for seals, by all means go ceramic... But steel seals do work, I have over 4 years of track time on mine, and street driven miles, its never been apart.

John V

The two guys I've talked to so far are Craig Nagler and Daryl Drummond... I think these guys know their stuff.

fc3sboy1

maxt, we are getting 202 to 205whp on a mustang MD1100 on a 6 port street port motor threw 2 mufflers and on an engine dyno with a single muffler and one of my headers i saw 245 bhp on a street port motor. the 245bhp motor was the only steal seal motor.



on the PP motor again i have seen over 350bhp threw mufflers on a 2 rotor PP motor. all 1 piece ceramic seal motors. there has been alot of minor changes in induction and header design and ports since mazda casted the FMR housings.



on the gear front i break s5 t2 gears easy. specialy at high rpm and also had major bearing failure. but since going to the rx8 stuff thoughs problems have lessend. also no longer take oil from the front cover, that is compleatly blocked off and now just take it out the side of the iron and plug the feed holes to the front cover and over to the OMP.



personaly to me for if nothing else piece of mind ceramic seals are a cheap insurance policy for the investment of a very high strung motor.

Maxt

That doesn't mean anything, like I said before about dyno's the numbers are not neccesarily true numbers... They are comparison tools to themselves, not each other.. I could make my p-port read 300 rwhp on mine, does that make me think 2 rotor p-ports make 300wheel hp? no... because I know they don't, when Mazda uses calibrated instruments for R&D worth 30 times what we use and says they are 200 ish hp engines at the wheel, I will defer to mazda for the true number..

There is piles and piles of info on this stuff in the mazda papers and people continually think they are breaking new ground on this stuff, it just ain't so..

Look at sanctioned racing, amemiyas car , 300 flywheel hp allowed, ever wonder why he runs with the extra weight of a 20b to make 300 flywheel hp? Ever wonder why rotaries suddenly became non competitive when noise levels on tracks were lowered, and the started to dissappear al together?

As for the FC stat gears, if you had a problem in an n/a application, something besides the gear was the problem, most likely a balance issue.