Power Power Power

Any form of normally aspirated power mods.
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chris-rx8
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Power Power Power

Post by chris-rx8 » Sun Apr 12, 2015 12:00 am

So I'm sure this is something that's been asked a million times before but I can't find a clear answer on it......what sort of bhp can a 231 make without forced induction or porting?

Also I've read a few times that rx8s don't make the power Mazda claims they should have as standard, how much on average are they down on power?

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Re: Power Power Power

Post by DanBass » Sun Apr 12, 2015 10:15 am

The short answer to the first question is not many. Maybe 10-15hp, with all breather mods and a remap.



If a 231 dyno'd 180-190 you should be quite happy, if you put much stock in that kind of thing.
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Re: Power Power Power

Post by Biguns » Sun Apr 12, 2015 12:18 pm

I've come to realise if you want power the rx8 is the wrong car, it's all about the handling, I have a rx7 which is quick but I know on a spirited run my rx8 can be driven quicker and be more fun
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Re: Power Power Power

Post by chris-rx8 » Sun Apr 12, 2015 12:29 pm

so a 231 you would be lucky to get 190bhp? That is pretty poor ive heard of manufacturers exaggerating figures but that's a massive difference.

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Re: Power Power Power

Post by Biguns » Sun Apr 12, 2015 12:44 pm

What they mean is because of the great handling it feels like 231 lol
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Re: Power Power Power

Post by Sakeiru » Sun Apr 12, 2015 1:07 pm

I don't believe 231 was a figure quoted at the wheels by Mazda. Waiting for correction on that :lol:

If it's correct then you gotta bear in mind that in RWD cars, you'll lose a chunk of power after it has been transmitted from the engine to the gearbox, prop shaft, differential, driveshafts, then finally to the wheels. I'm told lighter wheels and flywheel makes a noticeable difference down the road.
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Re: Power Power Power

Post by chris-rx8 » Sun Apr 12, 2015 5:29 pm

ok so are we saying they make 180-190 at the wheels? if so that makes it alot better, figures quoted by Mazda would have been at the flywheel surely, that's the figure that's usually quoted.

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Re: Power Power Power

Post by DanBass » Sun Apr 12, 2015 5:32 pm

They make 180-190 at the flywheel I believe.
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Re: Power Power Power

Post by chris-rx8 » Sun Apr 12, 2015 9:41 pm

Yeh if it was 180-190 at the wheels they would be making around standard power at the flywheel which would be good but looks like that's not the case, more likely around 150bhp at the wheels

So basically if you spend a couple of grand on exhaust, intake, remap etc you still wouldn't make standard power let alone power gains

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Re: Power Power Power

Post by Biguns » Sun Apr 12, 2015 10:30 pm

That correct I'm afraid hence why a few of us have rx7's for the days you want more power
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Re: Power Power Power

Post by Pettit Racing UK » Mon Apr 13, 2015 6:14 pm

Our demo car / development car on a independent hub dyno as part of its role as Banzai mags project car for this year:

It shows small gains add up, if you do things properly. Mind you its not cheap tuning an RX8 compared to the easy and cheap gains on some other car makes and models, especially turbo ones, but I do LOVE this car!
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Re: Power Power Power

Post by chris-rx8 » Mon Apr 13, 2015 6:29 pm

Thanks, that look good, what did this car have done to it?
Also are you guys likely to offer a supercharger again in the future? :-k

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Re: Power Power Power

Post by Pettit Racing UK » Mon Apr 13, 2015 7:37 pm

Its a Pettit engine, plus our full exhaust system, plus our ANP remap, plus K&N (or HKS, I cant remember currently) Panel filter, and heat shielded airbox and various other bits of heat protection.

Things like the light flywheel, light wheels and removing aircon pulley all help eliminate drag and parasitic loss, and increase responsiveness, but don't actually add power. I would say that a light flywheel is a grade A essential mod for any performance seeking RX8 owner, especially when they do a clutch replacement.

Regarding the supercharger, nothing currently planned, but some stuff in the works. Don't hold your breathe though!
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Re: Power Power Power

Post by chris-rx8 » Mon Apr 13, 2015 7:49 pm

Thanks, i think exhaust might have to be my next step, and if I need a clutch replacement in the future will upgrade my flywheel :thumleft:

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Re: Power Power Power

Post by MadTaz » Tue Apr 14, 2015 9:10 am

I got 211 on the dyno on a very hot day with Pettits exhaust and a few other mods. Not including a lightweight flywheel

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Re: Power Power Power

Post by Pettit Racing UK » Tue Apr 14, 2015 12:49 pm

No worries. Let me know when ready Chris, we usually have them on the shelf....
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Re: Power Power Power

Post by J2daG1990 » Tue Apr 14, 2015 2:13 pm

In terms of increasing natural power while staying NA there are a number of mods you could do but the gains will be minimal:

Exhaust system: mainfold - midpipe (de-cat will give you the most BHP) and aftermarket backbox
Intake system
Upgrade your ignition system
Get your engine re-mapped
Engine rebuild and look at ported/bridged options

The problem is that there are loads of different makes and manufacturers out there. Some will gain BHP, others may lose you BHP. Most make high BHP claims but take these with a pinch of salt. It's all about doing the research and picking the best of the bunch :thumright:

You can also look at making your car lighter in order to increase the BHP/Weight ratio.

Other mods such as a lightweight flywheel, Under-driven pulley kits, etc. won't increase actual BHP but will make your engine more responsive.

Petit Racing's ANP package covers most of the above which they have mentioned.
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Re: Power Power Power

Post by cib24 » Fri Apr 24, 2015 3:42 pm

RX-8s are not one of those cars that dyno very well and it comes down to two reasons: (i) operator error and (ii) the Renesis doesn't make as much power as Mazda claimed. According to Carl at Hayward Rotary, the reason that the RX-8 often puts down much lower power than expected on a dyno has to do with the ECU. He claims that in order to get the most consistent and highest results from the RX-8 on the dyno you need to literally do 10 or more wide open throttle pulls because the ECU needs time to adjust the air/fuel and timing tables. In reality you probably don't need that many pulls but I think what he is trying to get at is that the ECU is adaptive. For example, let's say you drive like miss daisy for 50 miles trying to get the best mpg, and then you decide to floor it. Well, the car will usually feel pretty sluggish the first few times you go wide open throttle to redline. However, let's say you have just finished a track day where you were flooring it all day. In this case the car will feel very responsive and eager afterwards for a few miles until it settles back down into "fuel saving" mode (or whatever you want to call it). I think it's the same concept with the RX-8 on the dyno. Wake the ECU up and you will get better and more consistent results.

Of course, what I just said could be BS so more knowledgeable people that understand the ECU better please feel free to correct me.

Getting back to modifications to increase power and make the car faster, in my experience the RX-8 does respond decently to mods but I can't comment on how much of a difference each individual mod makes since most of my modifications were all done at once. In terms of best bang for your buck (or pound) for power only (not handling) I would advise that you should do them in the following order:
  1. make sure your engine is healthy and make sure your oil, spark plugs, ignition wires and coils are top notch as this makes a HUGE difference;
  2. if you need a rebuild get it ported as this provides the largest gain especially higher in the rev range;
  3. if getting it rebuilt throw on a lightened flywheel as the car will feel much more responsive;
  4. full exhaust, i.e. header (I think it helps but probably only do it if you have the engine out already), midpipe/high flow cat, and cat-back. I think the Racing Beat and Pettit systems are the best for quality and performance unless you are willing to fork out the cash for the BHR long tube header;
  5. get a remap. Although I don't have experience with this I have seen enough dyno's online showing good increases in performance;
  6. 4.77 gears if you can find them or afford to buy and install them;
  7. lightened wheels and if you are really hardcore make sure they are 17's; and
  8. K&N filter or Racing Beat intake although I'm not sure if these really do much.
My car has most of these modifications and I can tell you it is noticeably quicker than a non-ported RX-8 as I am able to reel in non-ported cars quite easily on circuit (although my driving in the corners leaves a lot to be desired but that's my fault and not the car). I had a little battle with a lightly modified Honda S2000 at Oulton Park last year and my car was pulling on him on the straights and keeping up in the corners. Of course circuit driving is like 80% driver but on the straights the Honda was slower and that comes down to the car. For your information, Honda S2000s typically dyno around 210 wheel horsepower stock on a generous dynojet in the USA, so probably around 195-200 wheel horsepower on the dynos over here which is about 240 brake horsepower as advertised (plus, they are a lighter car).

In a nutshell, don't believe everything you read on a dyno sheet, especially when it comes to RX-8s.
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Re: Power Power Power

Post by Harrizone » Sat Apr 25, 2015 9:46 am

cib24 wrote: In a nutshell, don't believe everything you read on a dyno sheet, especially when it comes to RX-8s.
I have faith in the one I sit on. :lol:
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Re: Power Power Power

Post by Elektix » Sat Apr 25, 2015 12:37 pm

My car has every mod Cib24 has plus more. I have put my girlfriends PZ aside mine, same gear, gave her a small head start each time and then I absolutely pissed off.

The only I don't have as Carl is adamant they will not yield any gains is a remap and D585's.

I will look out the quick video of my car at Donington last year, even with my dodgy clutch (MRP's basic OEM item which I was recommended to buy - please don't. Get the Exedy item if you are upgrading as it is shocking under pressure)

I stormed past three Rx8's on the straight.

Also, whoever on here owns the white R3 on track at Jap fest 2. If someone is pushing you along, get out of the way!! I wasn't flashing you to let you know how great my headlights were. You were MASSIVELY holding me and everyone behind me up!

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Re: Power Power Power

Post by Will66 » Sat Apr 25, 2015 1:13 pm

They probably knew about your sunroof Nick! :P
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Re: Power Power Power

Post by Dave-B » Sat Apr 25, 2015 1:38 pm

Remaps produce gains. Fact. In black and white!

But I don't think I'd want to void my rebuild warranty if that was the cost of one.
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Re: Power Power Power

Post by chris-rx8 » Sun Apr 26, 2015 8:12 pm

I'm certainly going to look into the Petitt ANP package looks good and hopefully see some gains, big question is do i get for the petitt or racing beat cat back #-o

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Re: Power Power Power

Post by Elektix » Sun Apr 26, 2015 8:22 pm

We have both the Pettit and RB in our household. I prefer the RB hands down. The Pettit is incredible loud.

But then my missus loves it, and she bought the car simply for how loud it was! If she added a manifold and intake it would be unstreetable.

Can't comment on the ANP, as I don't know if they have changed the package from when I looked.

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Re: Power Power Power

Post by chris-rx8 » Sun Apr 26, 2015 8:58 pm

cool thanks for that, i want something that sounds really nice but not silly loud, also might look at doing some trsack days and my local track Castle Combe have quite strict noise restrictions

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