im sorryto bring this back, but in doing a little research i found on one website this quote "The sum total of all these changes were a faster responding turbo, better efficiency and higher boost capability."

yet from what I heard, they cannot boost as high as the stock twins due to what they are made of. can any one explain this a little better please.

 

im pretty sure that they hyave the same boost capabilities, they do spool a little faster tho...

 

oh come on this topic is covered once a day.

the consensus is that there is minimal difference. it is beleived that the 99s will spool quicker but have a DISadvantage when u up the boost.

 

Been running them for a few years. Only diff is quicker spool. Hit 15psi just like the regular twins do. I think that supposed disadvantage that they can't handle higher boost is mis-information (aka bullshit).

 

From what I understand its the induction system thats diffirent on teh 99s and one of the things no one knows is that there vacume system is run from one box. There are alot of little diffirences that come together in the 99 setup.

 

If you dig around, DaleClark posted the compressor maps for the 99s and pre-99 spec turbos.

The maps are different and the 99 has more room on the high power end of the chart. It's not a huge difference, but it's not made up.

Dave

 

Well, these are my own observations of the USDM turbos vs. the 99s. FWIW, I have a stock motor and I boost anywhere from 13-15psi. The 99s hit noticeably harder after say 7-10psi. The USDMs, to me, seemed to have spooled better from 0 to around 8psi. Or maybe it was just the torque they generated at that level was better. But up top, the didnt feel as good as these 99s. It's a slight difference but still noticeable. They definitely are have louder than my USDMS!

I plan to concentrate purely on autocross next season and actually would prefer the USDMs for better response. IMO, if you want more power from STOCK UNMODIFIED twins, go with 99s. I'm not exactly sure, but you may actually get them cheaper too.

 

Damn cant find it, i remember that thread.

 

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

 

(better to call them 280PS turbos btw - as 99-spec is a much worse misnomer, though not as bad as 'efini')

According to Japanese magazines, they ARE less reliable under conditions of sustained high boost (for example, circuit racing) - due to seal failure.

280PS FDs make *less* torque and 2500rpm and *more* at 5000rpm - this is also a fact. I had assumed that this was just a set difference in the OEM map - but it sounds like it might be directly related to the turbos.