I'm positive this same topic was covered numerous times but among the 100's of threads I found while searching, I wasn't able to find anything answering my question. I simply want to know how much PSI the stock turbo's can handle under optimum conditions, such as an upgraded intercooler, upgraded fuel pump, bigger injectors, etc. Just curious.

-Neal

 

14-15psi seems to be the norm for some longevity -assuming you have a low pressure drop from the turbos to your motor.

 

I ran 15lbs and I think max efficiency is 14lbs (but you are also maxed out on fuel as well). I thought on one of the threads someone said 12lbs. I just wanted to mention I ran 15lbs with a Greddy SMIC which also was at it's max efficency level. Stay under 15 is my advice.

 

Yes GoRacer is definetally right~~ I have non sequential stock turbos and they seen to sustain the 14-15 psi range pretty good.... but make sure you have a power FC or fuel computer to compensate the pressure loads. I think if you go over 12 psi you need a fuel comp.... I think... I'm not sure... but its real good to get one.

 

Anything over stock boost is reducing turbo lifespan. Running 14-15 psi and boosting all of the time is typically going to dramatically shorten turbo life. Above 16 psi the stockers start falling way out of their efficiency range.

There is really no reason to push the stockers so hard. If 14 psi or so isn't enough power, then you need to look at upgraded twins or going single turbo.

 

Thanks for the info, do you happan to have any idea how much HP is gained from boosting from 10 to 14 PSI?

 

http://dyno.zeroglabs.com/dyno.php

 

Im intrested in this aswell, how much horse power does each 1psi generate ( i know its gonna deppend on exactly what other mods you got but if you took a complete stadard RX7 how much we talking?????)
,,,, I used to have a ford escort turbo standard boost was 8psi,,,,i used to run 17psi was awsome.. just seems hardly worth boosting 2psi on ym mazda unless its gonna make a big difference, thanks

 

thats a cool site, nice idea on the comparsions and whatnot.

 

To give you a rough idea, atmospheric pressure is about 15psi. So add 10psi of boost, the stock system intakes oxygen at up to 25psi absolute. Add 2psi boost, and it's 27psia. That's 8% more than stock. 8% more than the stock 225rwhp is 243rwhp.

In reality, the gain will be somewhat less due to thermal inefficiencies, and the more you raise the boost the more the error will be.

Dave

 

When my car was being tuned the second time, basically it seemed the efficiency of the stock turbos was up to about 12psi roughly, over that not much power was gained but it seemed to raise torque at that point. It was tuned to 14psi. The power gain from 12 to 14psi was not even comparable to the power gained from 10 to 12psi. So I think they are really only "efficient" up to about 12-13psi I would say from my experience.
My power mods:
Pettit large race port
3mm seals
supra fuel pump
1300 sec. inj.
FMIC
Intake
DP, MP, CB
PowerFC
Aem Ign.

 

is this true twin triangles,,,because i see so many people running 14psi on there stock twins,,, from 12ps to 14ps,,,there was very little power increase, sounds dissapointing,,,,maybe BNR3s for me then

 

I have the 99' spec and can tell you there is a noticeable difference between 12psi and 14psi. My tuner told me about 10-20 hp per pound. There are some dyno charts around the net that seem to confirm that.

 

At the drag strip get 17-18 libs out of mine but they probably blow a lot of hot air. I run stock injectors with room to spare but do have an upgraded fuel pump.

The new BNRs look like a winner.

 

jd on the forum got his turbos to spool at 17-20 lbs efficiently but they wouldnt last but so long.....buuttt he beats the ish out of his car!

 

Gotta remember that Mazda/Hitachi designed these turbo's back in the late 80's when 10-psi was considered high.

Although you guys couldn't buy your FD RX-7 until 1992, Mazda had already had the 13B-REW + 20B-REW engines running in the JC Cosmo series from 1990 - 95. A few tweaks here & there for the FD series of 1992 had the RX-7 version but the basic design was settled on several years before hand with the Cosmo.

The highest any Japanese tuning shop will take the turbo's boost to is 14psi as they know that anything over that mark is chewing into reliability real quick.. Many set them to 13-psi just to be safe.

I have a series-8 RX-7 (99-02) & dont run more than 13-psi as a general rule as I would like to the turbo's to last as long as the engine.

REgards

 

I remember seeing you run last year, sorry we missed you last month at Budds Creek. Did you run race gas on that setup? I don't know how you do that on stock injectors. We have similar mods but you got a full second on me! Brian