Twin Turbos
 

So i want to put twin turbos on my rx-8; similar to the 97 supras. Is this possible. Sorry if i sound retarded, I dont know much about rotary engines.

Before you get bashed dude....use the search function. This topic has been brought up more than once before ;)

It won't fit without extensive modification.

a single would be fine. +twenty five characters.

Why do you want twins? Just to be like Supras? Two isn't necessarily better than 1 although it can be. On a rotary there really isn't a reason to use 2 unless you just want to be different. From a power standpoint there isn't an advantage and it costs much more.

Supra guys make many design mistakes just to make huge peak power numbers on a dyno. If ANY of them would actually design a total system properly, they could get much more usable powerbands and still keep high numbers. Don't copy them if you want smooth predictable performance.

I like twins.
I could see going to some kind of uber complicated sequential/staged setup if you wanted to crank out 500 whp up top and have boost down low. Then again, it kind of goes with the saying, "if you have to ask, you can't afford it." But if you have piles of money laying around, it's certainly doable.

Isn't Maddog doing a custom twin turbo setup on his 8?

Unless you want to be different, there is almost no reason to go twin. Single turbos now spool quickly and have near the same responce. Not to mention that we are working towards around 330-rwhp, maybe a tad more, and a single turbo can accoomplish that with ease and virtually no spool time.

There's a reason a lot of the RX-7 guys took out their twin turbo's and went with a larger / single turbo.

that is mainly because the system was overly complicated and failed often, not because the twins suck. But in the qwest for huge rwhp numbers a single turbo is used for packaging mainly. But companies like BNR have twin turbo kits for the FD that work flawlessly.

Exactly how fast can a single turbo start producing boost?
 

For street, I'm not 100% sold on how a large turbo will improve the car overall where the majority of time is spent below 3.5-4k rpms. So here's a question. At what RPM does a 'large turbo' kick in at? It would be nice to see a comparison between 250, 300, 350, and 400 rwhp.

its all in the tuning and which turbo you choose. there are many variables

I'm just going to get one of those fake BOV things from ebay.... It'll sound like I've got twin turbo's. :rofl: I think N rider already has some...

good point, plus look at the new 3 series 330 bmw, though i'm unfamiliar to its exact setup

Boosting below 3-4k really isn't needed. When you need power, the amount of time you'll be under 3k is non existant.

If you want to see how the 270 vs 330 whp turbos compare, look for the dyno sticky in the major hp forum.

Buy a supra. Problem solved! :spank:

Or swap a 2jz in our car, it will be pretty amazing, but will ruin the purpose of the car.:puke:

Did someone say 2JZ swap???


http://i32.photobucket.com/albums/d3...54/2jzswap.jpg

How much does this cost? Can you get 3 JZ's? :)

Somehow I don't believe that the time spent under 3k is shorter than the time spent between the last 1k rpms to redline. Think about it the other way around.... waiting for boost to kick in takes an eternity when you're under 3-4k.

I had a MR-2 with a large aftermarket turbo and have aquired a skill which takes care of this problem...it's called "down shifting". Works like a charm.:lol2:

You get to 3500 rpm pretty quick. You only have to worry about 1st gear, too. Once you're past that if you're goen fast you're above 4 grand, or you downshift.

And we're only talking about 9-12 psi of boost here. It doesn't take that long for a properly sized dual ball-bearing CHRA-equipped turbo to reach that boost

That's news to me, since I happen to have a turbo on my car and don't recall sitting around for an eternity for boost to show up.

As I said, if I wanted power, the last thing I'm going to do is slowly accelerate from 900 rpm. If I'm driving on the highway in 6th gear, the rpms are going to be around 4,000 anyway. Boost is INSTANT the second I mash the throttle.


For those who think throttle at low rpm is going to take forever to build boost...

http://youtube.com/watch?v=vTFWJiHOGv0

watch at 42 secs in. I'm accelerating from about 2,500 rpm in second gear (you can hear the crappy stock boot making noises every time I move the shifter).

just keep in mind this is an old video, before it was dyno tuned, so it made about 30 whp less than now.

Thanks for posting the video. Is that a stock flywheel on there?

When I made my comment, I stated large turbo, and while the Greddy may be fast, I don't consider it to be a large turbo. So does anyone know at what rpms boost kicks in for larger turbos (than the Greddy)?

yes, stock flywheel, stock pulleys.

far as larger turbos go, look at the graphs here:

https://www.rx8club.com/series-i-major-horsepower-upgrades-93/dyno-comparison-rx-8-turbo-supercharger-etc-115447/

Everything besides the DNA supercharger makes more hp than stock by 3500 - enough that you would feel. Looks like the larger turbos start to really shine by 4300 rpm though.

If you are going for a land speed record, then multiple turbocharged rotors would do the trick. If you just want to go to the store, save your money for gas this summer.

If you are under 4k rpms in anything other than 1st gear, are you actually driving hard?

Also, I believe the Greddy is a bushing turbo. You could increase the turbo size and upgrade to ball bearing and not lose on the spool speed.

Looks like really good boost from 3K+ and full boost right b4 5K.....not bad



I dont have an rx-8....but ur free reving seemed slower than what i thought rotaries should be....am i just ignorant of how they are orrrrr?????

Actually at that time I had the boost controller setup to slowly move the wastegate. On a quick setting, you'll see full boost by 2800 rpm or so, but then you can easily spin your tires from a dead stop.

mysql.. just a comment.. lol.. the sound of your BOV drives me nuts every time i watch one of your videos. That thing is obnoxious!
Otherwise, your car is hawt! Lol.

the bov doesn't sound too bad normally, in the videos the camera is right up at the bumper or with the hood open.

I've been thinking about getting a tidal or type-RS, but it's not high on my list since it doesn't do anything besides change the sound. I can always set it to recirculate and completely remove any noise (pipes already setup for it)

1.) What are you doing owning an RX-8 is the majority of your driving time is spent belwo 3500 rpms?

2.) You do realize the RX-8 is a total dog below 4k rpms right now in stock form, right? Would it really make a difference if the turbo didn't spool til 4k rpms?

3.) If you're talking 250-400whp on the large majority of cars that's not a "large" turbo. There are road race and time attack guys that use GT35-37R turbos, and they need good powerbands, not big power. Yet even with that turbo some cars can make over 700whp.

Not on a 13B.

And sizing smaller to get boost below 4K would be ideal so the car isn't as much of a "dog".

Wow. Someone woke up on the wrong side of the bed. Mad props for deteriorating this thread.

1. Yes, most of my time is spent around 3500rpm as it's my daily driver now -- I totaled my motorcycle in a really bad crash recently. I've slowed down a lot ever since gas started +$3/gal! However, that doesn't mean that I don't drive this puppy balls to the wall. :)

2. I brought this up, so I don't see how your question is relevant.

3. We're not talking about 'the large majority of cars'; we're talking about Rx8. This thread is about twin-turbos. Therefore, we're not talking about pure racing applications, but moreso street applications.

-jc

I shift by 3000 rpm's daily driving a Civic! It's easier to drive like that in an RX-8 so i don't see what the issue is.

I think the more important point is, if you are driving at 3500 rpms, what do you need boost for? At 3500 rpms, if you want to accelerate quick you are going to down shift if not one then 2 gears. At the lower gear, your RPMS would be way over 3500. If you look at the dyno comparison thread, you'll see the different power bands people are getting with different kits. A twin tc is not going to alter the fundamentals of the engine so you are going to get similar characterstics as the other kits but possibly a different combination than they do.


The general mechanics of air + fuel -> power apply to all engines which why someone can claim a turbo to be a "400 hp" turbo without knowing what engine it might go on. It'll flow a high enough mass of air to produce 400 hp at a generic bsfc to get to 400 hp. The point is is that the goals and properties of what used to be a twin turbo system can now be accomplished with a single turbo system in many cases. The additional cost and complexity of a twin turbo then becomes moot unless your application specifically demands it.

And yes, sometimes Ike is a touch unfriendly. Watch your fingers. He does bite.

HERE IN PUERTO RICO SOME RACE CARS ON 13B REACH 1100 RWHP AND 7.20 @180 MPH IN 1/4 mile:fingersx:

They probably also get 4 gallons to the mile and will never go more than about 10 miles in their entire life (if they are lucky!) before they need to be rebuilt or replaced.

I meant on a GT35 for the 700whp mark, which is why I put it in bold when I quoted Ike.

I don't tend to bite unless I'm provoked, but then again, I do have my days. :)