Hi,

Seeing that I started my RX-7 ownership with a second gen I'll start by saying I've searched, and read...and read some more, and haven't found *exactly* what I'm looking for.

If you made it this far, I'm looking to get advice on turbo selection for an FD that is mostly going to see road courses and spirited weekend driving.

I'd like the broadest, most predictable power band possible, which obviously depends a lot on tuning, but it has to start with the right turbo. I'm willing to street port the motor, nothing more I'd like to keep it reasonably street-able. I'd like 400 lb-ft of torque, or thereabouts and 400 hp (I won't complain if it makes more )

I've been looking at GT35Rs and GT40Rs both of a-spec's kits and it looks like I can make that power with either turbo. I'm curious to hear owners thoughts on when they see positive boost, when they see full boost and when (if ever) it starts running out of breath.

The other option I'm looking at is this nice looking Innovative GT66 dual ball bearing that's been in the for sale section for a while. The previous owner supposedly made 400/400 (approx) at 14 or 15psi and also road coursed the car.

I've considered stage 3s but I'd like the linearity, less heat, less complex engine bay, weight loss etc of going single.

Obviously I'm open to even more options that you turbo gurus might have.

Thanks in advance for your comments

 

It sounds like you want an LSX motor...lol Rotary motors generally make a lot less torque than hp. Those are both good turbos for your hp goals.

 

Keep in mind that engine port and tune will also effect torque, Im hard pressed to believe someone ran same hp and torque numbers. Having good response and a nice flat torque curve is what you are after though. I would talk to Damian on here as he has some pretty good track time behind running one of our setups.

 

You need a 3rotor! I'll be tuning again next week and upping the boost a little, but here's my dynosheet on a Turbonetics T76 @ 11psi, also for roadrace use:

 

Sean, I know what you are saying about the torque/hp numbers, we talked about this, but even so if it did make 397 like they said, that's good enough for me

3 rotors, lsx swaps haha I'm open to these on a different project hehe

Sean, out of curiosity can you tell me what kit Damian is running

 

Damian is running a 500R.....

I thought those numbers sounded familiar, sorry I talk to so many people daily about the same questions I get them mixed up at times and can't keep up. I'm not doubting 397 on torque it's having equal torque to hp numbers I find questionable.
Ray at PFS does a nice job of using port work and timing to pull nice torque numbers, even still when you look at say Ernie's older dyno runs since that was a Sp motor, he did 706whp and 564trq. That is far from equal HP/trq numbers.

I would say if you can get 200ft/lbs by or before 4k you'll do good. We've had customers cars get 200ftlbs by 35-3600rpm. You can get torque sooner the issue then is smallish turbo and then you will not make the power up top. 440whp and 350+ftlbs is possible at moderate boost levels 15-17psi. 400/400 at 15lbs is a bit of a stretch on a 13B.

 

Sean, I believe you, all the searching and reading I've done indicates that rotaries don't tend to do that too often either, but I'd be more than delighted with that torque number.

When you said 440rwhp and 350+lb-ft, would that come from your 500R kit? I thought that would be too big for that low end kick...but it seems if Damian is having success with it...and I think Rich is running that as well..hmmm

 

Check out Atihun's 35 setup:
https://www.rx7club.com/showpost.php...&postcount=252

CrispyRX7 and GooRoo also run the 35

 

personally id go with a street-port (even a large one) and do a 67mm turbo like a T04Z itll hav more than enough power for a spirited drive and will be awsome on a road race track, that turbo will spool pretty quick and youll have alot of boost coming out of the turns, couple that with good suspenion and you can put porsches to shame in the turns and still have plenty for the straights

 

The 500R on Broken09's FD made 450 horse at 15 psi and 503 horse at 20 psi, not sure on torque figures. He's also running a full 4 inch turboback exhaust, I basically copied his setup. I havent road raced in a long time (which should change soon), but I think this setup is pretty well suited for it. I can tell ya I see 15 psi by between 3500 and 3700 depending on the gear.

 

I have something new I'm working on that will be very nice. Depending on the the way you size it it will either give you 500R performance with better response or good response with more up top than your 500R or TO4Z if your looking for more power than the those without the lag of say a 4088R or 4094R

 

Id say get the GT35R, Mine puts out 220ftlb trq @ 3800rpm and 442ftlb @ 5500rpm. Im runing 20psi 10% ethanol and water injection and it makes over 500rwhp.

I do track sprint timed events with my car, its good fun. On the dyno is see full 20psi at 4000rpm in 4th gear pull. Im yet to record some boost logs on the datalogit on the road in different gears to see where max boost is achived in 1st 2nd & 3rd.

 

If you're a highway car torque should be irrelevant. Highway cars use horsepower. Torque is suited for that 0-60 jazz. Horsepower is what makes the car GO at high RPM's.

One ft/lb of torque is like applying 1lb of pressure to the end of a 12" wrench. The bolt the wrench is attached to will feel 1ftlb of torque. RPM is rotations per minute, 3000rpm mean the motor will turn 3000 times in 60 seconds. HP is a combination of the two and represents the actual power produced. Imagine being on a bike, you put 100lbs pressure (torque) on the petals, now multiply that pressure by how fast you pedal to get the power. If you pedal twice as fast you will make twice the power. If you hold the brakes at a dead stop and apply the 100lbs pressure you are making torque but not any HP.

Imagine putting a torque wrench on the crank and applying 100ft/lbs torque. You just made 100ft/lbs torque! Now try to do that AND turn that wrench at 3000rpm. That's a little tougher but that's exactly that the motor does. Torque x rpm is how you get HP, there is no magical shift from torque to HP as rpms rise. If a motor makes 300ft/lbs tq @ 2000rpm and can still make 300ftlbs @ 4000rpm, it will be making exactly twice the HP at 4K that it did at 2K. Normally an engine makes peak torque at around 2000-4000, but peak HP at a higher rpm. Torque will drop off as rpm rises beyond that peak mark, but since it is in fact spinning faster it will actually be making more power. At some point about 2000rpm or so beyond peak tq, the tq will really drop off, at this point the tq will be so low that additional rpm will no longer be enough to make power. Zero x 7000 is still zero. So somewhere between 4k and 7k there is going to be a happy spot where the combination of tq and rpm will make the most HP. If you look at the power graphs you will see the pattern between tq, rpm and HP.

Hope I made some sense and didn't make things worse.

 

stock port (maybe mild streetport), a-spec gt35r 1.06a/r with long-runner manifold, and 4in exhaust.

I have this setup but streetported and 3in exhaust and wow. Boost is almost instantaneous. I can only imagine what torqure would be like on a smaller streetported motor with a 4in exhaust.

 

My vote goes to the 500r. I run a gt35r with a streetport on a road race car and LOVE it. However I bought it just before sean came out with the 500r or I would definately be running that turbo. That thing is just badass, it is the PERFECT turbo for a 13b period.

 

I have the 500R kit from A-spec with a 1.06, here are my torque numbers at 16-17psi with a very CONSERVATIVE tune on 91 octane, 3" exhaust, resonated midpipe and RB duals, large street port.

3000rpm = 150ft/lbs
3600rpm = 200ft/lbs
4000rpm = 250ft/lbs
4200rpm = 275ft/lbs
4800rpm = 290ft/lbs
5400rpm = 300ft/lbs
5800rpm = 310ft/lbs
6200rpm = 327ft/lbs
6600rpm = 326ft/lbs
7000rpm = 320ft/lbs
7200rpm = 305ft/lbs

 

Oh Yeah,? What might this new turbo be called eh?

 

Not quite sure yet, I may just sell it as a improved 500R. The issue is if I call it a updated version people will ask if I can update my 500R, and they can't, it is a completely different turbo. If I sell it as a new setup it will present it's own issues as well so I'm not so sure yet.

Currently I have three new options I am getting ready for market.

The new BB unit that will come in two flavors....

One will offer the same or better response than the current 500R with a bit more up top and be focused primarily on SP engines or street driven cars. Damian's track car would do very well with this turbo. It will be better designed for maximum power/response at 20psi or less, (though you could run it up to 30psi as far as comp eff. on a SP motor. Just wouldn't be ideal) most bang for 450whp car.

Two will be the same but will be setup strictly for those who are after higher flow or more power up top than say a T04Z in the same size package with basically the same overall response. Very good for HBP engines.

The third is a updated version of the GT3574. It will offer better flow with minimal sacrifice in response. This will be offered along side the current version for roughly another $100 to cover the higher parts cost, and will be the best bang for the buck non-BB unit available for your rotary.

Those three new turbo's will cover 99% of your street, road race needs on your rotary. Highway monsters, dyno queens, or drag, need to look at something entirely different.

Hope that helps

 

Yes, the first option sounds so awesome.

Please keep me posted Sean, you've got my contact info

 

Grrrrr you're like the prom queen that wants to "wait" with posts like that. lol. any ideas when it will be available? you should call it the 550R with sp and hp variations for spool and horse power

 

Agreed I am waiting to order this new turbo kit as well! Its getting worse because the weather is starting to warm up here in the North!

 

This idea I like, I may use some of it. The issue I have is it is called a 500R because it is capable of 500hp. So I'm kinda stuck with 500R. But I like the SP and HP idea.

 

I like the idea of this kit hitting the market!LOL

 

I am worried about about buying this new turbo you are talking about. because the second I buy it, you will come out with something bigger and better. lol keep up the good work.

 

Yes you may lol