HardHitter

I have been looking and researching the Greddy Turbo since it hit the market, and I was wondering if I should go ahead and pull for this kit or wait another 3-4 months when hopefully more aftermarket turbo's come out for the RX-8. I know of atleast 1-2 other companies working on a turbo kit, and then a couple others working on a supercharger.

I know that the Greddy will only push out around 60-70HP (to the wheels?) for about $5000 including kit, BOV, guages, installation.

I've read on these upcoming turbo's that are costing $5000 for just the kit and it isn't even a complete kit or something? The results so far are greater than the Greddy kit in comparison.

Basically, I am a 19 years old and want some more HP/torque in the car, but I don't want to break my bank too hard.

What I'm basically asking is the Greddy worth the $5000 and it is upgradable (correct?) or should I shell out the extra $1000-$2000 to get another kit that will push out more HP?

devious12

I don't know alot about turbos but I do know that you need to look at the most reliable kit out there due to the fact that more boost may get you more power, but in our engines more boost may get you a blown engine as well.

Maybe you can chime Rotarygod in on this he would know more about it or there may be another thread about it I'm not sure.

IZoomZoomI

rule of thumb is usuall don't get a turbo until you can afford a new motor. This would completly void your warranty so you might need some extra cash just in case. Other than that go for it

o yeah and there are a lot of threads about this already...

rotarygod

This is really a judgement call that only you can make. The Greddy kit is only capable of about 300 hp. You will get no more ever from it. The turbo is far too small.

PTP and others are working on other turbo kits that may have more inherent potential left in them. As always how fast you want to go is directly proportionate to how much money you want to spend. How much power you add will also determine how much reliability you want to sacrifice but on average you'll still get about 90% of your engine life out of a properly designed one. Your right foot will determine how accurate that is.

There are also a couple of supercharger kits in development that look very promising. The axial flow supercharger and Hymee's twin screw supercharger both look like they will be nice when they are finished. I would be impossible to tell you which is better as that is just an opinion.

You can go out and get the Greddy kit now and get a little performance updgrade or you can wait and see what else hits the market later. If you wait, you know you'll end up with one you like as you'll have choices. If you get one now, you may like it or you may see an alternative at a later date that you wished you had instead. I suspect almost any kit out there can make most people happy in some form or fashion. Personally I want to see both of the supercharger kits but again, that is my opinion and personal taste.

devious12

I'm sure this was asked before Rotarygod, but do you think that the superchargers will be more efficent and or better in which ways for the 8?

I am also waiting, I'd rather keep my engine N/A although not many compainies, unless someone wants to que me in on who is doing it, are doing lots of internal work. As I understand it not many gains can be made with porting an header work, although I'd love to see it happen.

Also can that greddy kit be tuned to run without the cat and just a straight pipe or will is pose too much boost for the engine to handle?

Fanman

Yeah, I agree with what the posters above said. I was looking for a kit that would get me to 275-300 whp, daily driven car. I was also not willing to spend $10,000 to make a kit functional on a $30,000 car. The Greddy was a good solution to me. It was relatively inexpensive, even with gauges, surrounding equipment, installation it was around $5,000-$6,000. If you are looking to get to 350-400 whp then another kit might make sense to you. Keep in mind that with the Greddy you can get the kit & pretty much stay stock (with everything else), with the other kits it would seem that you would need to upgrade the clutch, get bigger injectors, etc. Just depends where you want to be & how much you are willing to spend on your ride. For me the extra $3000 was not worth it.

Greddyturbo1

I agree with Fanman, but would also like to add, the Greddy kit is a damn good turbo and you can tweak it more ways if you need more power as alot of us have... As also would like to add my 2-cents about waiting- usually those who wait, usually wait and wait and wait and never do anything, how long do you want to wait 2-years 3-years , who knows if you will even have the car then.. maybe the RX-7 will be out or something altogether different, then you will have to start waiting all over again til the better or bigger FI system comes out again..

Do you see what I'am saying, enjoy you sure can't say that Greddy doesn't make a good product.

cretinx

This is pure bullshit.

First off, the GReddy turbo is an 18g compressor inside of a TD06 housing (they call it the T618Z), its good for AT LEAST 400 hp so long as you can keep the fuel flowing and the engine can tolerate the boost (stock internal RX-8 in Puerto Rico pushing 19 lbs of boost says it can, especially if you look at the compressor maps).

ALSO - the GReddy kit uses a Mitsubishi TD06 housing and Mitsubishi series flange - this is good because Mitsubishi guys have been adding turbos to their cars since about 1990 - there's a SHITLOAD of upgraded turbos you can get that are physically the same size but have more efficient compressors and spool faster due to dual ball bearings and whatnot - AGP (AGPL3R), SlowBoyRacing (SBR GT35R), Forced Performance (FP3065) all make turbos that can easily put out 500-750 horsepower with spool characteristics faster or in the very least equal to the GReddy T618Z.

As far as superchargers, I know there's big advancements in supercharger technology, but generally you will have to pay more to make as much power as a turbo, and with the GReddy turbo full boost occurs basically as soon as you mash the gas in first gear - the advantage of the supercharger would be that boost would be on even in 6th gear below 3000 rpm.

However, another great thing about the GReddy kit is that the torque curve is pure, absolutely flat, just like a superchargers would be once the turbo is on, and this makes for lots of fun when paired with our tightly geared 6-speed (especially in 4th and 5th gears on the highway).

Finally, with the other turbo kits, you have to upgrade injectors, and this generally means you're going to take a huge hit in fuel economy. My fuel economy stayed the same in city and actually improved on highway with the turbo.

HardHitter

Like I said, I'm basically going for show and go. I want the car to look good, but when I need to power, it is there for me. I go to the races a lot and there are a lot of my friends cars pushing over 400-500HP to the wheels, yet it seems like they are always selling them because something always goes wrong with the engine. I just want something that will bring the 8 faster than what it is, quicker, and a lot more peppier than it is, but not need to deal with engines blowing up or seals breaking etc etc.

Basically needed for a daily driver, but every now and then when I want to have fun at the races, it'll be fast enough to stay up with some of the supe'd up cars.

HardHitter

RotaryGod and Cretinx,

Thank you for both your views on the turbo. I want to keep this thread on topic, so if you two feel as though you need to explain something else to each other, please go ahead and do it, yet keep it on topic.

I want to pull atleast 300hp to the wheels as a daily driver without any problems. I've heard a lot of complaints about the e-manage being locked with the kit, however, I'm probably going to purchase another emanage and tune the turbo if I can get better HP out of it than the preloaded maps on the emanage.

Creatix, I see that you have the turbo, how much HP are you pushing right now? How much boost are you pushing and when does the boost start in the rpm scale? Do you feel as though the 8 is a considerable amount quicker than it was stock? What can you compare it too? Also, did you have to buy any other upgrades or did you just bolt the kit on?

P.S. I also want to add that I have a RP High-Flow Cat pipe and the Greddy SP2 exhaust. I've heard some bad things about someone with a pipe and a lot of back firing, he put the stock pipe back on and it was okay. I cannot remember if it was a straight through pipe or if it was a high-flow cat, but if someone could tell me if I would be safe with my Hi-Flow Cat, I'd appreciate it.

Fanman

HH,

1) You can easily wipe the stock Greddy map. There are updated maps floating on this board, that will allow you to go to higher boost levels.

2) If you are looking for 300 whp on your car, the Greddy kit should be fine. It has that power potential. If the T618Z is theoretically large enough to give you up to 375-400 hp, but the honest truth is no one has done it yet. No one wants to be the first to blow the engine in their car.

3) My RX8 is quite a bit quicker than when I was stock. But the best thing I love about the Greddy turbo is that you have much more midrange tq on the car. Literally from 2500 rpm up you feel more push. It does kind've die off on the top end though.

4) I'm having problems with my hi-flow cat. The person that pulled his unit off & put the stock cat back on had a hi-flow cat (not a straight pipe).

I'm located in the LA area. If you want to drive my car sometime, or if you can make it to one of the Malibu drives (except for the next one) you can check out the difference.

rotarygod

First of all before you call bs on me, learn what you are talking about in terms of how a rotary uses airflow vs how other engines use it to make power.

First off before I get into that part, don't EVER quote boost pressure in an argument for power. The amount of pressure in the engine is irrelevant in determining power output. It is the amount of actual flow in cfm that makes power. I have an air compressor tank in my garage sitting at 120 psi right now. It is at 0 cfm of flow and isn't making any power. Pressure is irrelevant flow is not. I somehow seem to have to mention this every month or so for people. There are 2 different types of compression ratio in an engine. The first is the static compression ratio which we all know as 10.0:1. The other type of compression ratio is known as the effective compression ratio. This is a combination of the staic compression ratio combined with the volumetric efficency. Your effective compression ratio is only equal to the static compression ratio at 100% volumetric efficiency. The effective ratio is what determines power potential, not the static. The extra amount of air that enters the engine determines this. Notice I said the amount and not the pressure that it is at. If 1 turbo can supply an engine at 10 psi with a total of 100 lbs of air (in weight not pressure) and another can do 100 lbs of air at 15 psi, they both moved the same amount of air. Don't say that "as long as the engine can tolerate the boost". It can but can it tolerate the extra amount of air entering it and can you tune it right? You're probably wondering why I mentioned moving 100 lbs of air in weight? It's just an example number but I'll explain why it is relevant.

Basically what you are saying is that the T618Z "is good for at least 400 hp". That may apply to a piston engine but not to a rotary. The key that you don't know is in how much air a rotary needs to make a horsepower vs a piston motor to make the same power. On average (that's the key word) a piston motor uses 7 lbs of air to make 1 hp. A rotary on average uses 10 lbs of air to make 1 hp. According to this fact, that means that the rotary only uses air on the average about 70% as efficiently as a piston motor. What is 70% of 400? I end up with 280. Basically you are saying without even knowing it that this turbo can do at least 280 hp on a rotary. I won't argue with that as it fits the facts and is very true. I don't see it going usably much beyond 300 hp on a rotary. It could but it is very near its peak potential on this car. A ported motor would make this even worse. If it has to supply this volume of air at 19 psi, that's not terribly efficent. The 1st RX-7 turbo that I ever built ran at 15 psi and did 425 rwhp. 15psi in itself is irrelevant but the point is that my turbo supplied an awful lot more air at the same pressures. If you spin a turbo up to 19 psi, it is going to be very hot air.

There is so much more to turbo compressor wheels, exhaust trims, a/r ratios, etc.. that you are leaving out. To say that another turbo can outspool a T618Z or make more power than it is irrelevant because you are completely ignoring all of the above details. I will raise the bs flag very quickly that there is a turbo out there that will spool faster than the one in the Greddy kit that will make 500-750 hp(350-525 on a rotary). In order to make more top end power, you need to have a better flowing hotside. A better flowing hotside is a slower flowing hotside. Even in turbos nothing is free and spool rate vs ultimate power is the tradeoff. If you can find me a turbo that will spool as fast and make more power, you will have found a specially made VATN turbo (variable area turbine nozzle) that will work perfect on a rotary. Aerocharger is no longer around but many auto manufacturers such as GM, Ford, and Daimler Chrysler are using these on diesels. Too bad they aren't rated over about 1300 degrees F.

Still think it's bullshit?

shaolin

Pwn3d

cretinx

You can't just spout out numbers as far as our cars are concerned on the dyno. They simply won't dyno properly. You can start with baseline numbers and work from there, but you can't compare it to other cars. Mazda claims 238 at the crank but the car dynos around 180, and GReddy claism 303 at the crank but the cars are only dynoing around 220 (240 with exhaust). I dynoed 220. I have 285/35/18 wheels in the rear which I'm positive has something to do with this, plus conservative tuning.

As far as tuning the e-manage, go to a shop that's licensed by GReddy and get them to custom tune it.

Boost is full by 3000 rpm but dips off after 6250 rpm - I'm told a boost controller fixes this completely (but make sure you have colder plugs). The car didn't feel that fast until I started playing around with it against other cars - this is probably because the torque curve is flat flat flat so you don't get the sensation of acceleration even though you're flying. I absolutely obliterated my buddy's Celica GT-S (intake/header/exhaust . . about 185 whp on a 2500lb car - he used to beat up on me stock and can run a 13.9 with slicks and the rear seats out), beat an E36 M3 sedan easily and also managed to pull from an E46 M3 convertible. Butt dyno feels like 13.7. This is just with the kit bolted on. I have no traction problems either (max-performance summer 285s in the rear and Tein coilovers). The car just squats and goes.

I already have a midpipe that's not installed, and I plan on going with a custom 80mm exhaust because the 60 and 65mm exhausts that you can buy on the market aren't designed for turbos - they're not straight through and the diameter is too small to deal with any reasonable amount of boost.

If you tune the car you won't get backfire - its ALL about tune tune tune - do everything custom, don't just run GReddy's map and then slap on bolt-ons - that's how the RX-7 got a bad reputation - people would just bolt stuff on and it would run lean and detonate. The stock RX-7 seals were good for 700 whp if you knew what you were doing.

dmp

One piece of advice - if a car will be a true daily-driver, don't tune to a imagined HP Magic Number...like:

"I want 300whp!"

What you'd be better off hoping for is:

"As much HP as your car can safely make".

If that's 250 - fine. 215? Okay. 350? Go for it. Tune for reliability and Safety, again, if it's your true 'daily-driver'.

cretinx

Ok - a few things.

FIRST - My GT3540R on my RX-7 spooled up JUST AS FAST as my GReddy does now, and that turbo was rated at 750 horsepower. 11 psi got me 308 whp. The design on this GReddy turbo is ANCIENT. Compared to the GTxxRs, or even the Garrett GT series, its volumetric efficiency is pathetic.

SECOND - You have to realize that turbos spool up about 3 times faster in a rotary engine than in a comparable displacement piston engine. This has an effect on the turbo's behavior and the power its pushing - if you can start making power earlier and have the room to flow the air, you can keep making power. That's probably why our turbo 8s drop off in power around 7500 rpm (aside from the lower boost) - the engine simply can't flow as much air as the turbo can push - with porting this should cure things (just like cams - I put a set of cams into my GSX and instead of power dipping out at 6000 rpm it pulled all the way to fuel cut at 7000 rpm and had more to go - same with my RX-7 - after the porting it was still pulling at redline).

SO - a simple (of course, expensive) porting should definately open up the engine and with the right turbo and enough fuel, make power until fuel cut.

Finally, we've got to pick a set of horsepower figures to use - we've got RX-8 horsepower figures, regular car dyno figures, or manufacturer figures - seeing 400 whp dynoed from an RX-8 the way they dyno is ridiculous, but if they dynoed like a regular car that really shouldn't be much of a problem.

As far as the GReddy turbo being good only for 280 RX-8-dyno hp, there's a GReddy turbo in Puerto Rico that's in this forum making 273 RX-8-dyno hp on stock boost (and one making close to 400 rx-8-dyno-hp on a different turbo) - add a boost controller, colder plugs, and a 3" exhaust (something I'm getting made custom since nobody makes one, and what I see as a big big big hindrance to making power on the car aside from the unported engine) and you should see above 300 rx-8-dyno hp - add injectors, tune the **** out of it and hit 18 or 19 lbs of boost with a turbo porting and you should start to approach 400 rx-8-dyno hp on the crappy mitsubishi 18g compressor.

In summary - this turbo is good for quick response and city driving and yes, under 300 rx-8-dyno horsepower with pretty much bolt ons - you CAN make more power from it if you want, but its going to be a bit harder than if you just put in a bigger turbo and gave it the fuel it wants.

I don't think making power is going to be a problem with this car and the selection of parts and engine modifications I see coming out - the real limiter is going to be traction.

Ajax

1. I'll agree with you that compared to the GT turbos, the greddy turbo is old.. It saddens me to see so many of these companies still using T-04E's as well. I realize they're the good and cheap and a workhorse, but seriously... let's get somethin current!

2. We were discussing this second fact in tulsa at the OKC bbq. You have to remember that the air moving out of the renesis is going to be slower than the air moving out of any other 13b because of the side ports. Who knows what the pulse train looks like for the exhaust pulses. I certainly don't.

3. As far as the 6250 power dip, I was thinking that that was due to the opposite of what you're stating. The aux ports open on the 6 port at 6250. The turbo seems like it's not flowing enough CFM to maintain the pressure at the high end, not that the motor can't flow enough air. I could have it backwards though. Maybe it is because the exhaust isnt flowing fast enough out of the renesis to build enough pressure to keep it that high once those ports open. Fred?

tuj

RG's right in my book. The key thing to getting the engine to breathe better is to increase the VELOCITY of the air going in and going out of the engine. Given the rpm, there is an ideal port shape that will maximize the amount of flow into the engine. If the ports are too small at some point in their opening, velocity will slow. Likewise, if any part of the ports are too big, the pressure inside the engine will equalize with the intake runners before the port is closed, stalling intake flow. The ideal situation is to completely fill the engine with high velocity air right before the port closes, maximizing efficiency. Of course, this ideal port shape changes with rpms, but we do have some things on our side; the 3 sets of ports and the electronic throttlebody.

With FI, its the same issue. The key is to shove as much air into the engine before it equalizes pressure with the intake runner. Because of the rotary's charging effect at high rpm's, it can be more than 100% volumetric efficient.

I don't doubt that the Greddy unit is capable of adding near 150+ extra hp if these things are considered (ie porting) and proper tuning is done. Just consider where you want your powerband to be. Remember: bigger ports and bigger runners are not always better!

RX-8fan01

If you want a 300 + daily driver go buy a ford lighting or a cobra for that matter ...

cretinx

Now that's just ridiculous.

The GReddy kit already makes 303 bhp according to their press.

MassiveAttack

cretinx -- what's your Turbo'd RX-8 dyno at?

cretinx

220 rx-8-dyno horsepower.
stock boost (6 psi, then down around 4 after 6250 rpm)
no exhaust whatsoever
285/35/18 on 18s in the rear.

When I get back from China in July we're adding the rotary performance catless 76.3mm midpipe, custom straight through 80mm exhaust, GReddy pressure sensor and harness tuned to boost rather than throttle/rpm signals (which will get rid of the hesitation/stumble and make the car behave like a factory-turboed car), 1-step colder spark plugs, and the TurboXS High-Performance boost controller which should maintain a steady boost level even after 6250 rpm. We're turning the boost up until the stock injectors tell us to go **** ourselves (and according to the sticky article at the top of this forum there's a good deal of fuel left) - I don't want to swap injectors, so whatever I get out of that is going to be the end of my engine mods, and it'll be weight reduction from then on (cuz I have the suspension under control).

rotarygod

The peripheral exhaust ports of the 13B engines lend themselves better to turbocharging since there is a very strong and powerful exhaust pulse from the exhaust ports opening instantly. This pulse is more of an impact on the turbo and it spools very fast. The Renesis exhaust ports open more gradually like a piston engines valves do. The initial impact is not as strong and exhaust sizing in a turbo will consequently be smaller. This isn't to say that a Renesis would not be a good candidate for a turbo. Any engine can be.

As I said earlier, just because a turbo (or more appropriately a certain family of turbo) is rated at a high horsepower such as 750, doesn't mean that the exact one that is being used will hit it on that engine. Thost numbers are solely for advertising use and selling product. If a turbo at 11 psi hit 308 rwhp on a rotary and spooled up fast, you can not honestly tell me that just cranking up the boost will maintain your spool rate and give you 750 hp. It will not happen. The exhaust turbine wheel or a/r housing would have to be changed to accomodate the extra flow. This will effect spool up rate. It is absolutely impossible to find a turbo that will hit that high of a power number and still spool up as fast as a small one such as the Greddy. The compressor wheel may be rated at a certain flow level (assuming you can tune it to that and ward off detonation) but the exhaust side will have to change depending on the intended use. Turbo companies will sell a turbo saying that a turbo is rated to a certain horsepower level. That may be fine for selling product but it tells us nothing. There is no detail. On what engine? At what boost level? With what trim exhaust wheel? With which exhaust housing? On what type of exhaust manifold (yes it matters!)? With what type of intake/exhaust? That's like saying a T-04 can do 550 hp. Some of them can. A T-04B can't. It still ignores most of the above details. Stop believing every manufacturers claim that you read. By your own admission the kit did 220 rwhp. There have been a couple of others higher but don't expect that number to do much more than about 300. To accomplish this you will have some pretty high intake temperatures. Just as a bit of caution, rotaries do not like intake temperatures over 190 degrees or so. That seems to be the threshold of detonation. Just watch out at high boost after heatsoak sets in. The ecu will automatically pull back the power at this level anyways. Whe it does, the piggybacks no longer compensate correctly.