What's up, i thought i would seek out you turbo guys to help me out with a couple of questions. I have owned my NA for about 2 years now and pretty much know it inside and out, but my brother just bought a tII and i need to give him some advice.

First of all, he bought an 88 TII thats got an hks 3"dp and a cone intake. It also has a jocobs ignition system and an s5 turbo. I figure that's about 230 hp at the crank? does that seem right?

Anyway, as far as getting a mp and a cat back goes, can he get both without any further mods (like injectors or wastegate porting)?

Also i have a quick question about porting the wastegate on the turbo. If you go ahead and do the port so that the wastegate is actually wider than the little flapper does that cause you to reach full boost at a later rpm? since the wastegate is leaking it seems like it would... but then again i am no turbo expert.

I welcome any advice as far as setting this car up. there is a local guy with a 5.0 who thinks he is hot ****, and i was hoping we could set up this rex to tear him a new one.

we also have a greddy type s bov, and anything else not mentioned on the car is stock. Thanks guys and i'm sorry if my post was painful to read because i'm retarded when it comes to turboes!!!!

oh yeah, its got 70 k on a mazda rebuild


Craig

 

if he is a stock 5.0, he should already have a new one ripped.

 

he's not....
he claims 265 at the wheels, they are heavy though ...

 

your brother should run okay with full exhaust and intake BUT... i'd get a A/F gauge to measure the mixture. Running a full exhaust and intake will make his car more suspectible to detonating.. meaning... BOOM... POPCORN.. whenever he's under full boost.

To be safe, tell him to buy a A/F gauge and 720cc secondary injectors from Greddy. I believe they're $125 a piece from the rx7store and he'll only need two. He'll be running rich after that, so his mileage per gallon will drop slightly. To fix his MPG, he can buy a S-AFC to lean it out a bit for conservative driving and richen the mixture for full out race.

- Kevin

 

cool, that's what i've heard, but does he also need a better fuel pump if he's gonna get the injectors? it seems like they'd need to be fed by a bigger pump. As far as the detonating with the full exhaust, is this serious detonation? basically what i'm asking is if he runs with a full exhaust and races, is he asking to blow his motor everytime he gets on it ?

do the s5 wasgates need porting?

 

I'd port it just to be sure. Do NOT go bigger than the flapper.

 

It would be a good Idea to get a walbro 255 fuel pump, S-AFC, FCD and if ur tight on the cash buy the injectors later, if not buy em all at once. Full exhaust, TID and cone filter with proper fuel mods should put u in the 240-250rwhp range. Oh and instead of a A/F gauge I would get a EGT gauge alot more acurate but its gonna cost a bit more to.

 

you can port the wastegate to roughly 25% larger than the flapper door. That is a rough rule of thumb, and I am sure someone on here is gonna say not to, but none-the-less it is acceptable.

 

do you have any reasoning behind that? i didnt think so.


its perfectly fine to port the wastegate hole bigger than the flapper. what that does is keep the boost from building too high and gets rid of almost all of the boost creep. however it will lower your boost a little bit (which is probably a good thing)

 

boostmotorsport ported his wastegate to just under the size of a H22 (honda motor) exhaust valve, and then used the exhaust valve as his wastegate flapper door

from what i remember the valve is pretty big so should help out with creep quite a bit

 

hey jacob whats up i'm jacob.

 

The S5 turbo fasthack said the car has usually does not have the same boost creep problem as the S4 turbos since it has dual wastegate passages stock. Probably not worth taking it off to port, unless you notice boost creep.

 

Get an exhaust valve of any engine and weld it onto the wastegate arm. You can go way larger than stock. BNR does 35mm ported wastegates.

 

you can make the whole wider than the flapper without hurting anything.

 

how long do you think it will take me to get my turbo out. S4. I have it ported to the edge of the flapper, but I now got a RB turbo back, and will probably need to port it more.

so how long?

 

you shouldnt need to go much farther than the edge of the flapper... if you're already ported it once, i wouldnt port it again.

 

but if you must... it took us about a half hour to get the turbo out (we obviously took off the downpipe and took off the upper intake) and about an hour to get it back in place. i would advise taking the lower intake off as well cause it gives you a little more room to work and stuff, but do whatever. feel free to ask any more questions.

 

next time I have my turbo out... I will make it larger. my turbo has 130k on it, so I expect it to go out the window in the next couple thou.

 

oh. well you didnt tell us that

 

yea I am hoping to rebuild it with a 60-1 wheel. any idea where I can get a rebuild kit like that.

 

i wouldn't waste cash on an a/f gauge, it fluctuates so much that you won't know what's going on. you'll need a boost gauge, and an egt gauge may not be a bad idea either. 720cc secondaries will be enough along with a walbro, but you may need a s-afc to control all of that. basically he's starting a money pit as one thing leads to another.

 

if anyone wants to buy a walbro, i still have mine (i had it out of the car when my car blew up)
i used it for about two weeks then took it out and put my regular TII pump back in.

 

1. On S4's, it is a good idea to port larger. A lot of aftermarket wastegates are built as such.

2. On S5's, there are two wastegate feeds, so you cannot port it larger anyway.

 

ok so i here's what i think now....There is no need to port the wastegate on the turbo unless we notice boost creep (which we probably won't?)

and if we want to go full exhaust, we pretty much have to do the injectors and pump along with it, and then end up running rich. Then we have to get the safc or something similar to turn down the fuel ratio.

how does an egt tell you your a/f mixture, i never learned about that one.

 

but wait, hypothetically, if we were to go full exhaust and no injectors, would that be an open invitation for the motor to go POP? has that happened to anyone here?