both of the turbo's make 10 psi in stock trim so regardless of the rpm (unless under 1800) the car is running 10 psi at WOT

 

180? lol. Aerodynamics make a huge difference at alot lower speeds than that. Don't believe it? Get behind a car that's got about 40hp on you, both of you punch it at the same time & see how close you can stay to him up to 130mph, Then do the same test but be beside him instead.

Consider the 99-04 mustang has a Cd of around .36 vs the 3rd gen rx7's of around .29, that's a .07 difference, which is quite big when talking about speeds above 60mph.

Hp/litre mean nothing as far as this goes. We're just talking about the two individual cars. As far as torque being what it's all about I don't agree. While torque is important, you're forgetting hp is just a way of measuring torque. Without torque, there would be no hp. I'm not going to argue with you about torque vs hp anyone that knows anything about physics realizes they're both very much related to eachother.
Well for one. I'm not a big fan of wrong wheel drive, but they're a nice daily driver car. All of my friends thought it was pretty quick in stock form, I'll admit it's better than the average car in a straight line, but nothing special. If you ever get to test drive a manual one, keep the rpms up & take it around some corners that's where they shine IMO Very very good handling cars & very good stopping power. I can't say about the 1st gens, i'm talking about the 2nd gens only (93-97). I bought one for my first car & build my first twin turbo kit on it using two used eclipse turbos.

I would never buy one again just because of the FWD & i like playing around in my cars (sliding corners every now & then, ect...) + upgrades are cheaper for the mustang They're fun cars though.

 

So the stock trim TT's aren't sequential they're concurrent? Hrrmmm.. Still, it be damn hard for a bolt on new edge GT to beat a TT RX7, especially with a tune.. That's just me though..

 

no they are sequential the smaller turbo provides 10 psi from 1800-3500 rpms there is a transition period 3500-4000 at 8 psi then the larger turbo takes over from 4000 on also providing 10 psi

also there has never been a front wheel drive RX7 they are all front engine rear wheel drive

 

Ahhh.. I had thought they were, I just don't know all that much about how Mazda does/did their TT set up's transition wise. There ARE some TT kits that have a larger differential between turbos PSI wise during the transition. I.E. 10psi from the smaller turbo isn't as much boost as 10psi from the larger turbo, at least from what I understand of turbo mechanics, and say spooling the second turbo at say 4psi, with 10psi from the smaller turbo through 3,500 RPM's, and 10psi from the larger turbo and 2psi from the smaller turbo from 3,500 through redline, provides a more even power curve I would think.. So essentially what you're saying is that in the stocker TT RX7's that ratio is closer together to even out the power curve?

And yah, I knew the RX7's weren't FWD..

 

yeah you got it that time, and the FWD comment was for one of the previous posts i just didnt want two massive qoutes in the same reply

 

10psi from either turbo is the exact same. The reason for the different sized turbos is because of the exhaust housing size. A smaller exhaust housing will spool faster, but will drag the engine down at higher rpm. Likewise A big exhaust housing won't have enough exhaust energy to spool at a lower rpm, but at higher rpm it won't create as much of a restriction in the exhaust.

If both turbos are producing 10psi, it's still 10psig total. They do not compound they way they're setup. Most compound turbocharging is used on diesels trucks, not gasoline engines.

At lower rpm the smaller turbo is getting all of the exhaust gasses while the bigger turbo is completely blocked off, when boost hits 10psi from the smaller turbo some of the exhaust gasses start to vent & the 2nd turbo starts to spool, but the pressure is just venting, it isn't going into the intake.
At around 4600rpm the gate to the 2nd turbo is opened completely & the gate on the compressor side is closed so both turbos are pushing into the intake, & both turbos are producing 10psi after the small pressure drop.
The smaller turbo is always producing pressure while the big one is.

Most factory twin turbo cars using an inline setup operate the same way as the rotary does including the supra & skyline, the skyline however uses two turbos that are sized the same, but they spool the same, one is blocked until the 1st one achieves full boost, then it starts to let the 2nd spool.

 

Hrrmm.. see I understand that much, I guess I'm trying to wrap my brain around how 10-psi from from two differently sized turbos is the same. 10lbs per sq in boost through a G35 is not the same as 10lbs per sq in through a GT60 is not the same. The larger turbo running the same pressure, pushes more air, or in this case, exhaust.. Now the way you explained it, I'd agree that the TT setups in most factory turbo cars don't compound.. But just physics-wise, pushing the same pressure air through a larger pipe is going to move more air than a smaller pipe.. The question is, how, if one turbo is larger than the other, is 10psi still moving the same amount of air? I would have to say that it's not as far as I know.. Now both may be RUNNING 10psi, and indeed the boost would not be compounded, as the larger turbo taking over at higher rpms could move MORE air, at the SAME boost level, but as you said, lag in the lower rpms which is what the smaller turbo is for.. Regardless, the larger turbo still moves more air per lb of boost than the smaller one does..

 

Volume would be different, pressure would be the same if the compressor trims were different. The compressors on the rx7's tt setup are the exact same size & trim.

To my knowledge I was fairly sure the exhaust were the same size aswell on both it & the supra, but I've heard that they used two differently sized ones. The source wasn't very reliable, but I'm not going to claim they're the same when I'm not 100% sure. I havn't looked into the exhaust side, but I do know compressors are identical sizes. The exhaust housing is a little more difficult to tell due to being in a big clump rather than separated.

Before I had heard that I was fairly certain all sequential turbos were the same trim & a/r exhaust & intake, but they routed all exhaust energy into one until a certain rpm then vented to the 2nd.

I could find out later tonight if I manage to run into someone at the strip that used to own one.

Edit: didn't run into him, but found someone else that helped on his car.

 

See now there I'm 90% sure you would be correct because the compressor housings are not the same trim size on the RB25DETT, and they do shunt from one compressor to the next. The shunt point is usually controlled by the PCM, but can be controlled with a boost controller and a tune. At least the way I've seen it done in the past.

On the Mazda TT setup, I was pretty sure they were different trim, however I could easily be wrong there. As you're right, the volume would be different, but the pressure would remain the same. Though I'm failing to see what the benefit of a TT setup would be over a single turbo if all you're going to do is sequence between two turbo's exactly the same size. The RX7's powerband is so high up there in the RPM range with that rotary it would just make sense to go with one small, on slightly larger at least to make up the difference in incoming air volume required at speed.

The 2JZ's in the Supra I'm pretty sure are set up to spool at the same time, as the GTE block can handle absolutely insane amounts of boost. I guess over all it just makes more sense for a sequential TT setup to spool two different trim units, otherwise it's just inefficient unless you're going to run them concurrently. That's just me though.