I've decided that i will block of the wastegate on my s4 turbo since i'll be making a custom manifold to clear the stock intake manifold and frame rails. Since i'll be running a external wastegate what size should i go with? I'll be using an s4 NA motor and trying to keep boost down to 6-7 psi at first.

 

You don't need big. 35-38MM would certainly do the job.

 

Awesome, would going too big be bad? I want room to grow, what kind of boost levels can expect to start having problems with that size? it won't be any time soon but i'd like to buy one once and just reuse it when i upgrade to a larger turbo

 

There aren't too many people who've done it, but BlueTII on here has a 60mm on his and I believe he still has some boost creep problems. Thats with a big exhaust system however. Big waste gates are expensive though, a Tial 38mm is almost 3x less than a Tial 60..

 

Anyone know anything about the ebay wastegates? a 38mm for like 40 bucks. To good to be true or a deal?

 

Whats cheaper, a good wastegate or engine rebuild?

 

Big wastegates, like big injectors, can be harder to control down low. You may end up with the wastegate chattering to maintain low boost levels.

 

Sorry to ask... but relatively how do you know how big to go? What's overkill, and what's perfectly sized?

 

of course the good wastegate thts why i asked. just because they are cheap doesn't mean they are bad that's why i was wondering if anyone here had ever used on of those 50 dollar ebay wastegates, if they are crap i won't get one. I don't want a bunch of crap about being cheap, i'm on a very tight budget and wanna save money anywhere i can

 

It depends on your setup. What turbo, what engine, how much boost, etc.?

 

Don't skrimp on essential stuff.

In fact, speaking from experience, you either buy good products now and build it once, or you buy cheap stuff now, put it together and break a bunch of **** THEN buy the good stuff and build it again. Thats how it'll happen 99% of the time.

Cheap will BITE YOU IN THE ***.

Don't buy the 40 dollar wastegate please. If you want to save money somewhere, build the rest of it yourself (manifold intercooler plumbing etc)

 

how true this is... You really do get what you pay for. I know a guy that built a turbo AE86 with almost all ebay parts and ran into nothing but problems until he blew a cheap head gasket and then his motor.

 

strange, i didn't know rotary engines had these

 

thats why he said AE86

38mm should be good enough for the kind of boost going through your setup, personally though, i would not skimp on the wastegate as that is going to be one of the most integral parts to your build. on the MX6 im building i went through speed clinic (i think) for a genuine Tial, i have heard nothing but good reviews about that one. ive always heard about the cheap ebay knockoffs not lasting.

 

Do not buy cheap wategates!!!!

My buddy got one of those cheap ones of Ebay. The wastegate got stuck and blew the engine up..You won't have much room for errors being your running a higher compression ratio than most.

 

Good enough for me, i'll get a decent one. Thanks for the help guys

 

Yes, don't buy inexpensive wastegates.

A wastegate is just too complex of a device for just any manufacturer to get right. Theres a spring, a diaphragm, a valve and who knows how many countless other parts inside of it that could go wrong!

Its just like building a house-- contracters know to never skimp and buy cheap, non-brand name nails at the Home Depot. The nails are the core of what keeps the home from falling down and high quality nails are inexpensive compared to rebuilding a fallen house. Thats why the really good houses are put together with name brand, billet-machined super-alloy color anodized nails where each nail is made in America and hand inspected for quality.

 

Show us a sketch of how your manifold will be designed. How are the wastegate runners going to be placed? You are going to bleed off both rotors right? Where are you going to get the flange for the tubine inlet? You really should get an s5 turbo and make a fully divided setup

If you have a full 3 inch exhaust I don't think a 38mm will do it. my HKS 40mm was woefully inadequate on my T04S setup. It could even keep boost down to 10psi, at least not when it was colder than about 50 F out.

you need to go to the single turbo forum and and the fabrication forum and look through pictures of custom manifolds. the design of the wastegate runners is really important. that's one of the reasons why the HKS log manifold is bad for controlling boost

 

Really??! Each nail hand inspected for quality? Billet-machined nails? Do you even have any concept how a nail is made?

You are either full of s**t or you are a nail salesman.

 

yea i have never seen these nails or the contractors that use them and i know lots of contractors.


If they were a real contractor they would go to Lowe's too. lol

 

lol i have framed million dollar houses and never seen these awesome machined nails you are talking ab

 

And these million dollar houses haven't fallen down yet? Thats amazing.

There's a reason all the houses built throughout history have always been falling down. Its because they haven't always had access to the latest in 21st century nail technology. Being a cheapskate on the precise technology that keeps your roof from falling on your head at night is just ridiculous.

 

You have odd building codes in the US. In Canada, we use these things called "screws" to hold our houses together.

Off topic, but I always think "WTF?" when I see people nailing frames together.

 

I didn't think I'd have to, but by some of these replies I feel I should point out I've been being facetious. There is no such thing as designer brand super nails, bolts, or screws.

I don't know anything about US home construction, but I do know construction professionals are very pragmatic and as a whole would not fall for overpriced gimmicky screws/nails the way the way we all seem to fall for overpriced gimmicky exhaust valves.

What I would advocate is getting one of these cheapo $60 knockoffs of the HKS racing wastegate, rebuild it with a genuine replacement diaphragm and spring from the $670 HKS version if you're concerned about quality, and use the money you save for a pop-off valve and keep the spare diaphragm in the garage. A OEM Corvette engine exhaust valve is like $10, so its not rocket science to make one of these.

 

i knew you were being facetious because no one would ever buy them and "billet-machined super-alloy color anodized nails". andonizing is for aluminum which would be too soft to make nails out of even 7075 aircraft aluminum would be too soft. Plus the "hand inspected" thing wouldnt work either or the nails would be $1+ each