what’s the safe boost on the s13 blacktop sr20det? i’m scare there is not enough fuel at the high end. i had a intercooler, cone air filter, walbro fuel pump, 3" test pipe, 3" cat back exhaust. thanks!
There’s no such thing as safe boost. All depenedent on the rest of your
components (air, fuel, cooling, etc.).
If you just did your swap, start low boost (3psi to 5psi) and work your
way up slowly (7psi to 10psi).
Your ‘average’ SR swap will run most likely between 7psi and 10psi on
91+ octane.
At least this is what I’ve learned. But don’t take my word for it. I still
have a worthless KA. 
I wouldn’t take it beyond 13 or 14 psi. You should be good to that with the FMIC and 255 Fuel Pump. Just make sure you are running high Octane (91 or up).
Yes this I would say is safe too, with the proper components…
Wouldnt you need bigger injectors to run with the walbro 255 at 14 psi?
With proper Air/Fuel and Ignition Management on a Stock t25
with FMIC 14psi is where the turbo then becomes inefficient.
13- 14 psi on 94 octane is fine on the street…
But if u track ure car…once a week say…for the whole summer and drive at 13-14 psi on the track 9 hours straight…you will 100% for sure do damage to the crankshaft bearings and piston rings over one or two seasons max…On the track…dont run over 9psi, just to increase the life of ure motor. …
12-14 psi and youre putting down 240 whp or so…pretty good numbers if you ask me. 
Depending on your breathability and tuning with that
boost you can make anywhere from 200whp - 260whp.
What are you talking about? You cannot reduce the boost pressure below the stock wastegate setting. Not even with a boost controller. Stock wastegate setting on an SR is 7 psi, not 10 psi. If you’re running 10 psi on a stock wastegate without a boost controller, there is something wrong with your wastegate.
As for safe boost, like mentioned before, the T25’s efficiency peaks at about 14 psi. Beyond that, you’re blowing too much hot air to make it worthwhile.
:roll: Alright, we’ll see how worthless my KA is with my T3 in 4 weeks.
We will see how worthless the KA is when it walks your fully built SR 
How much boost? I will be running a T3/T4 as well with plenty of yummy boost. But don’t bet me on this, anything can happen and I may not have
an SR at all. 
We will see how worthless the KA is when it walks your fully built SR [/quote]
You’re on mister. And I will do it cheaper then you too. Ha!
(see msg above).
the problem is the T25 drops off in the high end, so 15psi below 4000rpm, slowly falling to 12psi is about as much juice as you’ll get out of it. Still good enough for a 12second car if you know what you’re doing.
I daily drove my SR at 1 bar. I really wouldn’t reccomend it. I’d say stay at .8-.9 then if the situation calls bump to 1 bar.
AHAH my problem was that I had a HKS EVC IV and the HKS wastgate actuator upgrade…don’t get the upgrade. It really wasn’t meant for a S13. It basically is a 1 bar spring. So besides a more stable boost curve my boost controller really didn’t do much.
FYI mods included:
HKS DP
HKS Dual Dragger
HKS FMIC Type S
HKS Racing Suction
HKS Plugs
HKS EVC IV
HKS SSQBOV Type II
HKS Wastegate Actuator
Hyper Grounding System
Koyo Racing Radiator
ACT Clutch
J30 VLSD
Whiteline swaybars F/R
Cusco Strut bars F/R
HKS Springs
HKS Upper Pillowball Mounts
Koni Shocks
300zx Fuel Pump
I think that’s it. It’s been a year since I got rid of it.
Yeah, the T25 sucks. The T28 isn’t much better either.
Which T3 are we talking?
T3/04 … great for drag. That’s a lot of air for 2.0L to displace though.
Safe boost level? Uh, you do know that PSI is a pressure rating right? It doesn’t tell you anything about how much air you’re moving.
T25 at 14 psi is not = T3 @ 14psi
14 PSI out of a T2 series turbo is basically the equivalent of a warm breeze through your trousers.
I am surprised the boost is falling off though. I know the T2 is bad for it … never seen a T25 that didn’t hold 1 BAR all day long. I used to spike to 16, settle to 14, then drop to about 11 with the T2. Again, that’s on a smaller displacement SOHC motor ~ 215 whp.
I think but can’t really remember for sure, but the T25 is a ~300cfm turbo. An that’s at 1 BAR of pressure over atmosphere, its max efficiency.
The standard T3 is a bit higher, but still, not exactly a smart turbo. It all depends on which T3 you have too. If it’s a rebuilt used passenger car turbo, and you were lucky enough to get one that’s oil and coolant cooled, you’re still lucky if you can crack 400cfm.
Mine is a T3 from a Z31. It is also freshly rebuilt.
I’m not going for tremendous power as of yet, I’ll start at the stock setting of ~5.5 psi, then work up with confidence. The nice thing about this T3 is that an intercooler is usless under 8 psi considering how efficient the turbo is in that range. Hello throttle respone.
Mr200- I’m glad that someone actually brought up CFM. Sadly alot of people thing boost is boost not matter the turbo sizing. How many idiots think that a more boost means a faster car not bringing in to consideration the size of a turbo.
I think the original question was based off the stock turbo for the S13 which is pretty much maxed at 1 bar. One reason I never got rid of the stock T2small turbo to go to a GT-RS was I really didn’t want to mess with engine management or other fuel issues. The SR I built was a beater car something to have fun with. Upgrading turbos would have put me in to more of an investment that I wanted.
I know … try moderating a board where turbo engines were relatively common from the factory.
I think Garett builds some decent pass. car and industrial turbos, but from a performance standpoint … not always the best route to go.
The t3/04 (again, depending entirely on which one) is a race or dyno queen turbo. Major major CFM if you can turn it. It’s easy to build boost on the rollers in 4th gear. It’s also virtually a no-load condition.
A T3 from a Z31 is a decent turbo … I think they’re the standard .63/.63.
There aren’t many turbos that need an IC at 8 psi. But unless you plan on building a serious boost motor, you’ll never appreciate the T3. They don’t spool very fast at all. The KA might move enough air, but keep in mind, Garett loosely rates their turbos by displacement. As in the T2 series is designed for under 2.0 of displacement. The T3 is for 3.0 and up. Some motors, like the 4G63 will move enough air (have you seen the head?) to spool a T3 … but with the wealth of TD05 upgrades available, the T3 is just a cheap solution.
I’d still pick a TDO5H-14B or small 16 for an SR or KA build.
Think about it, Mitsubishi dropped the 14B for a T25 because customers felt the boost “engaged to harshly.” End result, the cars were slower.
The TDOs spool lightning quick and can easily pump out 1.5+BAR of boost all day long. The 14B still outflows the standard T3 (405cfm to 360) and the small 16 is pushing over 500cfm.
A 14B rebuilt can be snapped up for under $300. The 16G center section is $100. Then you just need to port or buy a ported turbine housing.
And if that’s not enough air to send your conrods into orbit, there’s always the big 16 (550cfm … EVO turbo), then the 18G or big bad 20.
But that’s just my opinion after all.
HKS came out with their Garrett based GT-rs. It’s honestly a great turbo for the SR application. It got great dyno numbers with a really flat curve(ballbearing turbo). I might be able to find the graph that HKS got at their US facility.
I agree a T3/T4 was a great “look how much hp I got” turbo but the curve was bad and really not very fun to drive.
Some people were opting for the HKS GT2835 which didn’t do too bad. But with the introduction of the GT-RS it’s been the golden set up from what I’ve heard.
I come from more of a rotary background and we all know how rotaries are dirty motors that spit out tons of exhaust. I was running a To4S with a stock motor. 411rwhp which wasn’t too bad. Next set up was supposed to be HKS’ T04R cutback with a street port but things happen cars get stolen.
Cars get stolen, little pieces of your factory POS exhaust manifold collector come off, meet your turbo at high speed. You think you’re playing Spy Hunter limping it home.
:x
The GT turbos (HKS or otherwise) are very efficient turbos. Again, I don’t pay much attention to them, because there’s no way I’m putting a $3000 turbo on a $300 car.
Do they have the ceramic wheels? One of our members has a very sweet T28 with ceramic wheels. Spools ludicrously fast … but apparently running it over 1 BAR can shatter the wheels. All I know is it’s something to do with a potato. Disco Potato?
gt28rs turbo is the “disco potato” capable of handling up to 350hp.