ReV2ReD

So, i'm prepared to get grief from people on this one, as i'm still doing my research at this point. My plan is to have a full race spec time attack car ready for the 2015 season, so i'm already gathering parts, but my big one is the engine and power.

It will be running a traight through exhaust, literally as shot as possible as i have no noise restriction, so it will be a side exit exhaust somewhere behind the front passenger wheel depending on routing, and full bolt ons, (ignition pulleys, flywheel, intake etc..) I will also be running high octane sunoco race gas, 105 or 107 cant remember exactly the specs of it right now.

My question is, would it be worth going the porting route on the engine, or would i still be better off with FI? I'm looking to get 350hp out of the engine in NA form if that's even possible!

I ask, because weight is a very big factor in the build, and i wouldn't want to offset the weight loss from the A/C system up front with FI if i dont have to.

So if any of you have any experience with that sort of thing, or if you can point me in the right direction as who to ask, then that would be greatly appreciated.

Thanks guys.

stinksause

iTrader: (5)

Welll .. I mean if you run Velocity Stacks and P ports, it could be possible .... OP if you are set on keeping it NA, look into getting an FC 6 port,

Join the 2nd and third intake ports, add a full P-Port, and that should get you close to those power figures. It will be peaky as all hell though

ReV2ReD

Well, after doing a bit more research, this could be financially ruining. Ok for a full blown race team but i'm on my own (unless someone wants to sponsor me ).

There's a company in Oz that does roller bearing cranks enabling me to spin it up to 14,000 rpm, and with a peripheral port, then i dont see why i wouldnt be able to reach those numbers, but my god its gonna be expensive! I could buy a whole lot of dry carbon for that sort of money. Not to mention the reliability issues and loads on a 14,000 rpm PP rotor. I dont want to have to be rebuilding the engine after every hour of running!

I think the best route is going to be FI. I'm still going to do an extended port on the engine, and run the smallest turbo and intercooler that i can to keep the turbo lag and weight to a minimum (safely of course), and i'll just have to offset the weight in other areas i reckon.

I'll probably have to make the turbo kit myself to keep the weight down to a minimum.
Hmmmm. decisions, decisions.

RIWWP

iTrader: (2)

...and I lost that post. Bleh.

Keep in mind that just making the engine able to spin to 14,000rpm doesn't solve anything. The fueling, porting, intake design, etc... is all designed for our ~5,000rpm torque band. You aren't going to just increase that band, so you will have to move that band up to be from ~9,000rpm to ~14,000rpm, WITHOUT losing torque in the band. Sub 9,000rpm would be crippling to our car at this point, making any brake check or slow speed corner kill your entire race as you try to get the engine wound back up into your power band. And then there is the question of if you can actually get a solid air/fuel mixture and flame propagation at that RPM. And the problem of how much heat you will be generating. There is already a dramatic climb in heat from 8,000rpm to 9,000rpm without an increase in power. The cooling solutions you would have to have would be significant, and probably more weight than a turbo setup would add. Water pump redesign to handle that speed without cavitation and complete failure.

ReV2ReD

All very good points, i had completely forgotten about the supporting mods required simply to support that kind of RPM.

It could definitely be that even going FI would be lighter (or at least the same). At that sort of RPM, the windage would be horrific so a dry sump would be a must aswell. Definitely talking a lot of added weight.

FI it is i think.

bse50

The only way to make more power to justify the expenses is with peripheral exhaust ports and a different intake manifold.
FI seems like the cheaper route.

d walker

just my .02, but you will be FAR better off using tried and true technology. Were it me doing this project it would be a 20B NA for 350hp, or a turbo 20B for a little more. Alternatively I would use a 13B-RE with a good turbo and try and make an honest 450 hp and just keep the weight down.
The problem is not in the powerplant, it is the transmission, differential, etc to support the power in your application, and all the bits you need are not cheap. They are not hideously expensive, just not cheap. Lets take a look shall we?

Engine- 20B with 350pluswhp
Engine management- MOTEC or the new AEM "Infinity" box
Trans- Recommend a Sainz, Quaife, or similar. Real race car parts, not terribly expensive and nearly unlimited gear ratios etc. Doesnt hurt it can be rebuilt trackside
Rear diff- would look into a Ford 8.8" swap, parts are cheap and the diff will hold up, many gear ratios are even more attractive
Clutch- Tilton. Period.

And then of course you have brakes, suspension, aero, etc. to deal with. You really will not have much RX8 left when your done but it will be a blast.

BTW, I am considering building a time attack RX8 myself, and these are along the lines of my thoughts

stinksause

iTrader: (5)

Buy a greddy kit, slap on a GT3076 and you are there ... you will be rebuilding the engine around every 20k miles.

If you want to be more reliable, run a custom manifold with a bigger flange, T3 or T4 if you can fit that to keep the backpressure down. With a less restrictive manifold design, it should last closer to 30k miles, maybe even 50k. All depends on tuning and power levels.

Obviously you need to consider fueling, ECU, Greddy Manifold Modification, etc, but that is the gist of it ... turbo lag with a lowmount system is very small.

What less turbo lag? Run a V mount intercooler

tranny and diff should hold up, get better axles ... if you have the $, rebuild trans with tighter clearances ... our transmission isn't weak, just sloppy

As an alternative, consider making one from scratch, with the economy down in Spain, it should be fairly easy finding a good fabricator for cheap

As another alternative, supercharge it ... there will be no lag and engine will last longer because less back pressure exists to cook your side seals

ReV2ReD

Thanks for all the input guys!

So, it will be FI, but it will be a custom setup. I'm hoping to find a used Greddy manifold and modify it, otherwise make one from scratch. It will definitely be a V-mount setup, as everything in the front of the engine bay is either getting binned or relocated. As i'm only shooting for around 450 at the crank, which is about 380 at the wheels, im hoping to achieve this with as little boost as possible (remember i'm running race gas), so as to run the smallest intercooler and turbo i can. I'm looking at using the GT2876R, as its still uses an internal wastegate so as to keep a less complicated exhaust setup, and according to garrett should be good enough for the power levels im looking at. The only thing i'm worried about is that im not good at reading compressor and turbine maps, so i dont know if im going to have to run that turbo at high boost to achieve it, whereas with a larger turbo i can run it at lower boost and achieve the same numbers. I'm hoping with the race gas ill get away with the smaller turbo and relatively low boost.

As for the rest of the car, i'm still doing the leg work, but i think suspension wise i'm goig to run a setup from Fatcat.
Brakes wise i'm looking at keep the stck dimesions, but running 2 piece rotors, and if i can get AP racing to make a four pot caliper for the right price and weight i'll go with that for the front, and i think, but still not sure, i'll run a 2 pot caliper for the rear and use a hydraulic handbrake, but the only people to make a 2 pot caliper that i know of are wilwood and stoptech, so i'm not sure how the brake balance will be affected when sourcing calipers from two different companies. The jury is still out on that one.
The trans and diff will definitely be upgraded. Theres a company in Oz that rebuilds the stock transmission with dog gears for not too much, and that saves me the headache of adapting a transmission to the renesis engine. It will just be a bolt on affair.
Clutch and diff dont know yet, still plenty of time to decide.

The one thing that the car is going to have lots of is Aero aids. Aero is a big hobby of mine, and this thing is going to have lots of it. Think german DTM style. That's all i'm going to say about that.

D walker, i'd definitely like to talk about what your thoughts are on what your going to do. I think these cars are fantastic handling things, and there a great platform to start from. I just hope when its all done it meets my expectations.

From what i can gather, even the japanese are starting to look at the RX8 with more interest. You definitely see more of them on the timeattack scene over there now, compared to three or four years ago.

Arca_ex

iTrader: (10)

For the tranny are you referring to PPG? Because last time I checked a dog box from them is like 10 grand for our car...

Wish I had that kind of money to blow lmao.

stinksause

iTrader: (5)

GT28 is still too small for 380 whp ... better run a bigger intercooler to deal with the shitload of heat you are going to generate, or a gt30 (at least) ... your turbo will need to flow at least 50 lb/min of air ... probably closer to 60lb/min ... Think about that when looking at those compressor maps. Rotaries need more air than piston motors to achieve the same power levels.

Don't run it on a T25 flange ... go for T3

you will find the greddy to be too restrictive in two places at those power levels.

1. The manifold

2. The 90 degree bend at the exit of the turbo compressor as well as the piping size....


Good Luck

Arca_ex

iTrader: (10)

Sorry I just read you're going to try and race the car at this power level... all I can say is good luck man. You're going to blow up a lot of turbos and a lot of engines, just be prepared for it lol.

At the rate of money you're going to be dropping I'm tempted to suggest doing a 13b-REW swap from an FD and going about it that way. You can pull 400RWHP out of those relatively easy compared to the renesis.

ReV2ReD

Hey Arca, the company is not PPG, its another company, that i saw just a couple of days ago on this forum. The sell a fully rebuilt dog box in the factory casing for about 6k, which seemed fairly resonable considering what your getting.

I will be racing the car yes, but remember its time attack, so they are only short stints, 3 - 4 laps at a time. As long as all the supporting mods are there i dont see why 380 at the wheels would be catastrophic for engines and turbos. The engine is going to be a built and ported unit from a reputable engine builder, and i'm going to make sure the turbo is big enough for the job so as to not be overspinning it all the time, but at the same time not going overkill.



Stinksause, thanks for the info on the greddy manifold. I'll make one from scratch then.
Just looking at my turbo options, and realistically the only one that would seem small and light enough and still flow close to 60lbs would be the GTX3071R. Either that or run the GT3076R. It doesnt flow as much as the GTX, but should still be adequate and not so expensive.

Either that or bring the power down to about 420 at the crank and maybe then run the GT28? I much rather try and run an internally wastegated turbo if i can.

bse50

When speaking of turbos and rotaries keep in mind 2 things:

Our engines are less efficient: The claimed power "output" for a turbo should be reduced by roughly 30%

The 13b-msp is not a REW\RE. Different exhaust ports location means different exhaust pulses. This translate to the need for differently shaped compressor blades.

It's all documented here somewhere

ReV2ReD

I'll see if i can do a search on that. Unfortunately the search engine on this site isn't the best.

Also, i understand that rotaries need more air, but surely the fact that i'm running race gas should compensate for that no?

bse50

Race gas will maybe give you a little advantage, mostly on the tuning you can run. I wouldn't think about it as a solution to the wankel's low efficiency.

The number and shape of the turbine blades is directly related to our engine's exhaust pulses.

ReV2ReD

Well, after shopping around it seems the GT3076R is actually cheaper than the 71R. ?????
I guess that's probably my best bet. I'll have to figure out the wastegate plumbing later. Shame i was hoping to run an internal wastegate, but they just dont make them that big!

ReV2ReD

Seeing as nobody likes to divulge the full details of the turbos they use on their kits, does anyone know what AR i should be shooting for? higher or lower? The 76R come with three different AR's for the turbine, and from what i understand the higher the AR the better the spool, and the lower the AR the greater the top end power. As its going to be power that i'm looking for i would have thought i should go for the lowest AR, but i dont want to then find out that its too low and completely inadequate for our engine.

d walker

First- even a time attack Renny is going to live a very short life under boost, and it is going to be a PITA to make the power you want to make. This is why I would say if its a TA car, go back to the 20B or 13B-RE and make all the power you want without too much problem.

The trans is the easiest thing. A Sainz 6spd sequential race box is about 8-10K depending on what part of the world you buy it in, and adapting it to the rotary is no issue at all.
the 2009-up OEM gearbozes are fine, the 04-08 are not. Would not even attempt to use one in a TA car. The 09-up box is better but still would not want to use it in behind big power.

As far as turbos, I used a 3582R on my last S6 13B and made 480whp and spooled like a demon. Were I to do it over again I would use exactly the same turbo. On a Renny I think you will have much better response if you can create a proper "long tube" collector style turbo manifold.

However I say again- I am considering the same project- I already have two RX-8's we race professionally and after this year there is a strong possibility those two cars will be relegated to club racer status. Since we have already built several, there is no issue building another, or two, or more with different purposes.

Power is not going to be your issue, rotary engines have a long history of making power and there are certainly a lot of people the world over who will be able to help. The one thing I think you will need to really pay attention to is the suspension. IMHO I would use Koni, AST/Moton, or Ohilins and forget everything else I know the of a couple cars using Penskes with good results, but doubt that those will be easily obtained, serviced, or repaired in Europe.

stinksause

iTrader: (5)

OP, unless you can figure out the OMP issue in boost, I strongly recommend looking into an RE swap.

Go for RE, not REW.

use this http://www.rx8performance.com/products/engine-mount

as far as housings sizes go ... smaller will provide better spool, but cut top end
http://www.moddedmustangs.com/forums...ze-r-trim.html

or read garret's tutorials ... they are quite good

bse50

d walker nailed it anyway: Saenz also has distributors in europe and a swap is probably the most reliable thing.

However i'd go the RE or REW route vs the NA 20b option just for ease of build. 20b engines are designed to be turbo and building a good NA performer may become a big headache for a builder that's not used to it. Internals and porting aside both the intake and exhaust would have to be custom made in that case. R&D costs both time and money and tuning may be difficult for somebody who never tuned a 20b before.
The easy way to get a properly built NA 20b would be willing to sell some spare organs and contact Mazmart.

ReV2ReD

Ok, but if i go for an RE swap, then how will i go about wiring and control. I mean, is it literally a bolt in affair and hey presto everything wires up and runs?

I just cant understand how the Renesis cant handle 420hp at the crank. That's only just over 350 at the wheels. There's people on this forum running that all day long with this engine aren't they? What about 400? would that be a safe number to run on this engine?

Forgive me for questioning it, its just that one thing i have learned is that its always best to keep things as simple as possible, and if i do an RE swap that's going to involve re-wiring and what not, then i feel i'm going to start complicating things.

My understanding is that the renesis is still a strong motor, it just needs a very good tune to make sure everything is sweet.

bse50

Wiring? For a race car i'd only consider a full standalone...
The renesis can handle that amount of power but it just won't last that long in race conditions for one reason or the other.

ReV2ReD

The transmission i'm fine with. The company in Oz has a great price and any gear ratios i choose. Its more than capable of running the power i need.

However! If i run the 13B-RE i get a few more sequential boxes open up to me from what i gather, as its a more established motorsport engine. Am i right?

ReV2ReD

Yeah i agree, but what about the ESP and ABS. I know most people like to look hard and say "i dont need that crap" but they are after all helpfull when your running at the very edge as you do in timeattack. I know you drive the fastest without those aids, but when you do **** up its nice to know they might be able to rescue you from a hairy situation. No?????

Then again maybe i'm just being a chicken ****.

I think i'm going to have to expand my budget!