RX7link, I agree 100% with almost all that you said, but one thing I wanted to correct-----the BNRs are actually all new CHRAs. Turbine wheels, Compressor wheels, shafts, the works. 20% larger to be exact. They also have reverse-thread compressor wheel nuts so that they won't shoot off under high boost like the stockers are prone to do.

Peter, given that the turbos are larger and that I made a verified 350 rwhp at only 12 psi, I'm not sure I agree with you. Yes, I was non-seq, but my streetport is nothing outlandish (hell, it was the first motor I ported), and 12 psi is definitely conservative on pump gas......

 

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I hear you on the turbo internals Rich, but I made 344 @ 12 psi ... only 6 less.

that's with 99's, sequentially, w/ a 30k old KDR streetport (small), no intake cleanup as far as AWS or Double throttle, and blowing through a little PFS IC, no underdrive pulleys, and with a resonated midpipe and 6-month old plugs... in other words, nothing special, right off the street.

Where you made more was up top... 390 vs. 365 @ 15 psi. I'd say you've got to contribute some bit of that to a non-seq. manifold and a bigger (mucho overlap, I believe it was) port. I say that because I believe Rynberg has a similar setup to mine, but with BNR's and made 365 as well at that boost.

I'd be surprised if your setup spooled the way a sequential 99 would as well... though I know your car was hellaciously fast... or made the sort of torque a sequential would.

The point I'm making is not to disparage BNR's in any way... just that with a stock sequential manifold, 99's may be sized more appropriately (or at least as good)because they make similar/same peak HP despite being a smaller turbo(s), thus you'd expect they'd spool quicker as a result. I know mine are like lightning. Certainly better than an OE set... at least in my opinion and experience... and I wouldn't discount them as a nice upgrade to the OE's with the sort of setup I outlined.

I've no question, for a setup more like yours, the BNR advantages are clear.

 

I have the 99's in sequential and from my observations the 93-95's have better torque characteristics, at least from low to mid boost pressures. After 10 psi, the 99s definitely feel like they're pushing harder.

 

Don, that's most likely a result of having fresh turbos. The 99s are virtually identical to the 93-95 stock twins, with a few minor exceptions. Actually, they're supposed to be unable to run as high of boost at the 93-95s--someone out in Japan (daioni i think) has posted that the tuners out there only run the 99 specs to 0.9 bar/13 psi due to their inefficiencies after that boost level......

 

This completely disagrees with the compressor maps that DaleClark posted last year. Those maps clearly showed that 99 specs should perform better at the higher boost levels than the 93-95s.

Of course, cold hard experience and dyno time means more than some chart, but I find it hard to believe the charts would be that inaccurate.

Dave

 

Dave, maybe someone from J-land with firsthand experience will post. I do that that for power levels around 300 rwhp the 99 specs are a great choice....Ihor and I installed them on a customer's car earlier this year and I was surprised by how nice they were. Brand new, go figure

 

I couldn't find the thread I was thinking about.

I did read though that the 99 spec have the same compressor wheels, just set in the abradable 'zero-tolerance' housing. FWIW.

Dave

 

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They are essentially the same compessor wheels, but with better sealing, which of course is "better" per my claim.... the point i'm making is, what I'm hearing is that "they aren't an upgrade, because they aren't any bigger", and I don't think that's correct. What they are is more efficient, and since the manifold is the bottleneck anyway, going bigger won't do much for you. You could bolt two T78's to the stock manifold, and probably not push much more power.

With the bottleneck present, it would seem the best thing would be to size the turbos to the bottleneck, and then look for improvements in efficiency and spool up, which the 99's DO deliver.

 

Dgeesaman, I believe this is the original post you're talking about that has the map on it.

https://www.rx7club.com/showthread.p...compressor+map

Edited to add that I've always seen higher numbers associated with the '99 twins in older posts.

 

http://www.catenet.net/dyno.php

The proof is in the dyno plot. Unfortunately no one has tuned identical cars side by side with all 3 sets of turbos and various boost levels but I'm with most of you: BNRs gain their advantage above 15 psi (or so). '99s seem to provide small gains across the powerband with the biggest gains at very low RPM. One thing to keep in mind is a bigger turbo doesn't always mean more power, it has to be run in its efficiency range. If you ran a T78 at stock boost levels it would probably lose out to stock turbos across the entire powerband, just check out some of the big turbos on that site at low boost: not so impressive.

 

There's something interesting to note though. If you go to the website and compare Rich's graph to a graph of '99s on 13 psi (1 psi more than what Rich ran, but Rich had full exhaust while the '99s had only downpipe and intake, cars 75 & 142 on the list), the BNR's made less power throughout the band up until about 6k. I'm sure if they were cranked up more they'd be heads and feet above the '99s, but it's still interesting none the less. There are some more impressive numbers from the '99s on that site, but they have more supporting mods and a lot more boost, most notably the ones running 16psi and hitting around 365hp. There's another set running 14psi and hitting 355 with the same mods I'll have, so I'm hoping for good things. Only time will tell I suppose.

 

Those guys were most likely seq while I was non, so that makes some sense. Also, that 12 psi dyno was on a dynojet at RP in texas on a 100 degree summer day. If those 99 twins runs were on a different brand dyno in different weather, it's tough to make direct comparisons.

 

I hadn't thought about ambient temperatures, different dynos, or elevation. There's a lot of variable left out on that site, but it's the closest thing we have so far. Hopefully I'll be able to get my car running well, have all of my stuff put on, get it put on a dyno, and then swap out the stock twins for the '99s twins. That's if this transmission problem works itself out.

 

Of course there are tons of vriables... but in terms of peak HP, I don't see where anyone anywhere is going to come up with much more than 365-385 rwhp with anyone's twins running sequentially at 15 psi. It's the manifold.

That being said, and having actually owned 99 turbos, I think saying they aren't an upgrade over OE isn't correct. No, they won't produce a massive peak HP increase, but I don't think anyone's will in those conditions... BUT, with the right setup they're a very nice match that produce alot of usable power under the curve—great spool up and torque.

 

Which is why I said:

Which is pretty much true. Most people when they are looking for an "upgrade", they are generally looking for more performance. i.e. would a midpipe be an upgrade over the stock cat if it only provided the same performance? Not really.

Unfortunately, there haven't really been a lot of back to back tests with stock based turbos. However, I have yet to see the '99s honestly produce numbers the stock 93-95s couldn't do, sequential or non. Not saying that they might not spool quicker, just staying if someone's looking for a big dyno numbers, the 99's aren't going to get them there over the stock 93-95s.

 

I've never seen the stock twins make over 330 in seq. form, unlike a few graphs of the '99s that are on that site that are in the 350-370 range. As far as non-seq. go, I've never seen anybody use '99s for that, so there's basically no information for that at all.

 

Many people have, however most of them have moved on or never provided a dyno to Wargasm's dyno page.

https://www.rx7club.com/showpost.php...5&postcount=15

357rwhp stock turbos sequential. He has since went non-seq over the last year. There are just few people who keep the stock twins sequential when getting their motors ported and such as they are generally after "big power". At 15 PSI, you basically need a ported motor to get more than 335-340'ish. Stock ports on stock twins will put you about 330 at 15 PSI. One member (oakridgerx7) did 341rwhp at 16 PSI.

 

^ Holy post count

 

1 So if I were to run pump gas, would that limit me too 15psi on BNR's? and if so, 2 Would that make more power then stockers?
3 ...though it would be more reliable correct?
Basic bolt-ons only