August 4, 2008

Gaining Power With A Renesis

A lot of people are displeased with the "lack of power" that the RX-8 provides, especially because of the fact that it is not twin turbo charged like its predecessor. Essentially, there are three ways that one can go about getting the most power out of the engine, and they are the Super Charge, the Turbo Charge, and the Exhaust Modification.

Now, I truly believe that the RX-8 is a balanced car, straight off the line. It handles well, has decent horsepower, brakes well, and has sporty looks complimented by a handsome interior. I believe it should be left for the owner to decide where to go with the car, thus why I like the fact that it's not turbo charged. Granted, turbos make the car faster, but I'm an "au natural" kind of guy. In addition, a lot of people lean towards the TRUST turbo kit or non Japanese brands for their parts, and I stray from that crowd. I've seen a few super charge owners, but not as many as those with a turbo. I'd prefer to see what the Japanese tuners have running under their hoods.

One of my favorite companies is Knight Sports due to their amazing, sleek looks, in addition to the great performance of their RX-8s. RE Amemiya has always been a favorite, but mostly for RX-7's, as well as Fujita Engineering. Knight Sports (correct me if I'm wrong) won in a RX-8 battle that was held not too long ago in Japan. Knight Sports is running a 13B from an RX-7, peripheral ported. Their lineup of parts for the stock Renesis engine in my car includes headers, a sports cat, and some really good exhausts. They claim that there is a 30HP gain with the whole system in use. Now, if you top that off with a Cobb AccessPort to change the mappings, along with some pulleys, you come close to 15HP gain. For just under $4000, you get a mean sounding RX-8 with a great power increase, bringing you close to 300HP (at the crank, not wheels). That's less than what a turbo kit costs, with added exhaust essentials and more. I have yet to see anyone go this route, so it's something I'd really like to try out. There's no worrying about possibly breaking the turbo, turbo lag (if that even still exists), or the entire setup. It is raw NA engine power.

RX Reviews gives great advice as he has tested a lot of the JDM exhaust parts. I'm just not sure why anyone would want to turbo this car when Mazda did not bother to do it themselves. I think they kept it NA for a reason; we just have to do the rest and make the exhaust system monstrous.


James said...

lets say you actually get the 40 hp out of those mods. and lets say your putting really good numbers on a dyno stock.. (175whp) that still will only put you a 215 to the wheels. Still a long way to go to your 300whp goal. Where for about 700 more than your initial budget, you can get 292WHP from a greddy kit.. check out this link.

Zelse said...

Good point, and good link. I edited my blog post to state I didn't mean WHP though. I know that no way in hell could I get 300 WHP with just exhaust and all that. Thanks for the input James.

Anonymous said...

The N/A gains are not necessarily cumulative, so 10hp w/ COBB on top of 30hp may not happen. Also, stock RX-8s have a bunch of variation in injector sizes and what not, so some run leaner than others. Those that run leaner (and thus stronger) stock will experience smaller gains with the AP.

Also, aftermarket intakes for the RX-8 may change the size of the MAF tube. The stock MAF tube is not perfectly round, so all the aftermarket intakes with round tubes are approximations of the stock MAF tube size. Some intakes may have a slightly larger MAF tube size, causing the ECU to think that less air is coming in (and thus leaning things out a touch). In that case, the gains from leaning out on top of the intake won't be quite as great.

Anyways, I would like to see some dynos for headers.

You should consider all your mods in terms of the whp. I bet the companies that advertise "bhp" gains are interpolating them from "whp"--I doubt they use an engine dyno.

I think the bhp of the car is still overstated at 232hp. Racing Beat dynoed the RX-8 13B-MSP engine at 212hp (on an engine dyno, source). This means that a typical stock RX-8 dynojet reading of 180whp is a 15% drivetrain loss, which is much more sensible than 22% if the bhp really was 232. So with all your proposed mods, you may get into true 250bhp territory, but no way are you getting close to 300bhp N/A.

I would recommend ECU tuning followed by an RP SuperCat for best bang for the buck gain (dyno from this thread, manufacturer link).

Zelse said...

Good point ILP, but upon doing some more look up, plus some small things I had forgotten to add... What about FEED's NA setup? As I mentioned before Knight Sports sells a lot of similar things to FEED, but Knight Sport's race car runs a 13B out of a 2001 RX-7, NA with Peripheral port. FEED runs a normal Renesis, with their headers, ECU, sports cat, exhaust, pulleys, Their intake, their intake duct, their oil, and their final drive gearing. So I guess it makes me wonder how they're keeping up to a 300 WHP RX-8 (the Knight Sports) if supposedly the mods I listed will only get you around 220 WHP?