rxmadness

iTrader: (1)

ok so i picked up a t3 turbo the otherday with an internal wastegate that opens fully at 7psi, so im pretty sure but not possative this is how it works....I connect my manual boost controller in line between the turbo output and wastegate, with the boost controller turned all the way out and NO restriction on the boost/vaccum line the wastegate will open at 7psi fully but if i turn in the boost controller valve a little bit so its restriction how much boost goes into the wastegate it take more boost to open the 7psi gate therfore creating more boost into the engine.......is this about right? i mean it makes the most sense to me but idk im just tryin to figure this all out.
thanks

rxmadness

iTrader: (1)

p.s sorry for the stupid question, its not normaly my style

Verneuil

The only way to know is to have a boost guage and when ur at full boost adjust it to where you want it. You could look up the specs for the turbo you have and find out what the Max boost itll produce, Least you know the min and max and you can do anything inbetween

Oneiros

The wastegate is a flapper valve inside the turbo, the part with the diaphragm, rod and hose is the wastegate actuator, this controls when the wastegate opens

the actuator has a spring rated at whatever e.g. 7psi, this is the amount of boost required to open the wastegate fully. The boost signal is taken from the hose generally connected to the turbo compressor outlet

your manual boost controller basically tricks the actuator by lowering the amount of boost it sees, simply by restricting the hose.. So the actuator still sees 7psi, but the boost at the compressor outlet is higher because of the restriction in the hose lowering the signal

manual boost control can only give you more boost than without one, for less boost you need a softer spring in the actuator

hope that helps, if not google it

rxmadness

iTrader: (1)

perfect! i was 100% correct then. and yes i have a boost gauge, i figured getting the t3 with a 7psi wastegate is perfect because i will mostly be running 7psi, so ill have the boost controller screwed all the way out, but if i ever felt like going to 10 or so psi all i have to do is turn it in a bit to where i want it! awesome

question: the stock t3 from a 87 tii fc is what i have, how bad is the boost creep on this unit? i did port the wastegate already i was just wonder how bad the creep is with a stock sized one

j9fd3s

iTrader: (3)

the stock FC turbo isn't a t3, it is a hitachi HT-18S

it might be similar in size to a t3, but the flange and wastgate are different

boost creep depends more on the engine/intake/exhaust, than anything else so its hard to say.

its kind of like the relationship of the engine power to turbo size, if that makes any sense. on a stock 13BT the turbo is "big" enough to make 13-14-15psi around 4500rpms, but @7000 its tough to get more than 6psi.

rxmadness

iTrader: (1)

oh i see, well ya mine is a ht18s-2s it will be on a large streetport 12a with blowthrough nikki, and 2.5" straight exhaust with one magnaflow straigh through muffler

mikeric

iTrader: (20)

Boost creep on the S4 is famously terrible and destroys engines. Get that wastegate ported yourself (there is a great link on how to do this in the FC forum) or start with an S5 turbo and manifold.

Lazy people (like myself) have had the porting done at BNR. However, I have found that this does not work as well with bigger compressors (duh), which is why I finally went with a T04 and an external waste gate.

In addition, due to the 6lb-7lb or so spring in the actuator, you will not be able to hold 10 psi too well. Even with the vacuum "tricked" the pressure from the boost will start bleed. Once the turbo really starts spinning, you will not be able to bleed enough air through the stock wastegate...

If you don't have one, I highly recommend a wideband 02 as you will quickly see if you are driving a time bomb.

The Hitachi turbos do not have good internal wastegates in general. However, the S5 is a much better choice and most S4 FC guys have upgraded to the better designed S5 setup.

bad 83

iTrader: (3)

Here's a good link for you that will show you how to port either the S4 or S5 series turbo.
http://fc3spro.com/TECH/MODS/TURBO/wgp.htm
As far as stock versus stock, the S5 turbo is better. BUT, with large unrestricted exhaust and engine porting, the S4 turbo housing can be ported WAY more than S5 to eliminate the boost creep. I always use the S4 hot side housings when I make my TO4E hybrid turbos. I take the wastegate porting a step further and port the wastegate hole to 40mm. I then have to weld a large washer to the original flapper door to close the wastegate hole. I NEVER have any boost creep issues with my 3" exhaust.

j9fd3s

iTrader: (3)

the lazy man says; just set the car up to run @15psi, that way you have to work to keep the boost UP

vs

getting the die grinder out to make the car slower, its way too much work....

rxmadness

iTrader: (1)

great info guys!! looking at that porting page it doesnnt look like i ported enough off, and sam i really like your idea with the washer, ill deffinatly give it a try, i have a mig and a hell of a nice rotary file. and BTW guys i have a wideband ill be using, dont worry i am taking NO shortcuts here, already spend 1,400 on new parts in one day twas like christmas times 10000 haha

so far i have or will have very soon, s4 turbo, walbarro255, adjustable FPR with gauge, boost gauge, oil temp gauge, exhaust temp gauge, wideband 02, pillar gauge pod, air filter(cone) manual boost controller, blitz BOV, fmic and piping, oil filter block(for turbo oil line)

the only things i still need are to get my nikki prepped, make or buy a carb hat, exhaust manifold(i preffer to make my own for the challange), make a downpipe, get larger fuel line, im sure there will be more im forgetting....oh ya and im going to rebuild the s4 turbo with a kit so it has fresh bearings and seals(it has a little shaft play, and i dont know much at all about turbos but a rebuild seems fairly straight forward) hopefully lol

arghx

iTrader: (3)

With the s4 turbo you are going to be missing some low end response without the twin scroll system working properly. It's that big actuator thing (not the wastegate). It uses a vacuum solenoid with check valve to keep one of the passageways in the turbine housing shut until 2800 rpm.

The s5 turbo has a better and simpler manifold design. You will have less lag with an s5 compared to an improperly functioning s4 turbo.

rxmadness

iTrader: (1)

i know, its depressing right AFTER i buy an s4 is when everyone starts telling me about how much better the s5 is lol i got a rebuild kit coming in the mail for it and i just spent the day polishing the cold side and heat painting the hot side...idk maybe when the kit gets here ill rebuild it and sell it to buy an s5 lol. anyone got one for cheap? i paid 75 for my s4 plus 40 for the kit

it does have a wastegate acuator and the nipple for the boost line, they where just off when i took the pic

arghx

iTrader: (3)

You can hook up the twin scroll with an rpm switch and an OEM solenoid if you want to

rxmadness

iTrader: (1)

but at any rate tomorrow if i have time ill port that sum bitch out and take some pics

rxmadness

iTrader: (1)

whoa whoa back up, twin scroll? does my turbo have this? or are you talking about the s5 turbo cuz if then, ya that makes perfect sense but that just seems like too much work

rxmadness

iTrader: (1)

nevermind i did a google search, i should start doing the more often than blabing stupid questions haha so what im reading is the s4 had a twin scroll flapper setup inside the manifold, so to make this thing work properly i would have to buy a s4 manifold and find a way to hook up the twinscroll? how about a few scenarios here, what if i put the s4 turbo on a aftermarket manifold with no twin scroll, what would be the effect? or is it just better to sell it and get a s5 turbo?

arghx

iTrader: (3)

There are basically no manifolds that will work with the Hitachi turbos. You really should just sell the s4 turbo and manifold then get the s5 unless you are really really broke or something. But technically you have three options and I will put them in order from best to worst. Oh and FYI:



S5 turbine housing on the left, s4 on the right

1) s5 turbo and manifold.



the divided manifold is best for spool and it has the least backpressure, because the exhaust pulses from the two rotors do not interfere with each other. The dual wastegate passages are a better design for boost control. see this thread: https://www.rx7club.com/single-turbo-rx-7s-23/mazda-scientifically-tests-single-scroll-vs-twin-scroll-turbos-903210/

2) s4 turbo and manifold with properly working twin scroll actuator



That flapper is designed to stay shut until ~2700 rpm to improve spool and give you more torque off the line. I imagine that's even more important on a 12A because of the lower displacement. Vacuum is supplied to the twin scroll actuator to hold the flapper shut until around 2700 rpm, at which point the vacuum is relieved from the actuator and the flap opens.

arghx

iTrader: (3)

To get the twin scroll to work like factory, you need an rpm switch, a regular old OEM vacuum solenoid with a filter on one side, a check valve (a working OEM one is fine), and a relay.



Here's how it works. The solenoid will be ON as long as rpms are below 2700 or whatever rpm you want (you could try testing on a dyno to see what the 12A likes best). With the solenoid ON vacuum from the intake manifold will pull the flapper shut. At 2700 rpm the rpm switch will engage the relay by supplying a ground. The relay will cut the ground signal to the solenoid, and the solenoid will turn OFF. The vacuum will be relieved from the twin scroll actuator, flowing out through the filtered port on the solenoid. The flap will be open. From the factory the twin scroll solenoid is controlled by the ECU, but you are carb'd so that's not really an option.

Wiring this up will probably cost you around $50-$60 dollars. You need to find an rpm switch (Summit for example) and you need a solenoid valve (OEM being the cheapest) plus a 5 pin relay.

3) s4 turbo and manifold with the flapper open all the time. This will hurt low end torque and make the car less responsive in normal driving. Since you already have an s4 turbo in your possession, this is the path of least resistance but also the path of least performance and enjoyment. It's pretty much the lazy/cheap bastard choice.

The best/simplest option is still an s5 turbo and manifold with a mild wastegate port. It will be the simplest way to do things for good performance.

mikeric

iTrader: (20)

S4 turbos are a hair above worthless as no one wants them and the reason you got it for so cheap. Remember, you get what you pay for--sometimes less.

If you go to the FC used parts section of this forum, you should be able to pick up a S5 turbo and manifold for a couple of hundred. However, you will find it hard to sell your S4. I had an S4 manifold with the flapper door removed, but I think I threw it away. If you want it and I still have it, I can send it to you.

I would save the rebuild kit and use it on the S5 turbo instead (not sure if it will work or if you need to buy an S5 kit).

Also, that paint is a fire hazard. It WILL burn off almost immediately and if you are stopped or driving at low speeds, it will burst into flames (I do not care what the can if came out of said).

rxmadness

iTrader: (1)

arghx thats a really cool diagram i appreciate it but like you said i would rather just sell this and get an s5 turbo.

but let me get this right quick, now say i did use the s4 and the manifold from the link below with no twin scroll it would spool up slow below 3k rpms, but after 3k it would be boosting just fine, or in otherwords below 3k it would have turbo lag therfore acting like a N/A motor until about 3k then it would be booting...correct?
http://cgi.ebay.com/ebaymotors/ws/eB...K%3AMEWAX%3AIT

rxmadness

iTrader: (1)

and i hear ya on the paint i thought about it last night and said **** it i sprayed a bunch of brake cleaner on it and got it all off, better to be safe than pretty

rxmadness

iTrader: (1)

btw i like this manifold because it puts the turbo right where i want it rather than the stock mani, and it should fit either an s4 or s5 with a little modification to teh adapter plate which is easy to do and i can run a big 52mm wastegate. but i am concerned about the way the pipes collect, does it look ok? if it does im buying it
http://cgi.ebay.com/ebaymotors/ws/eB...K%3AMEWAX%3AIT
heres teh same thing but with pics at different angles
http://cgi.ebay.com/ebaymotors/86-88...item2a0713d8bb