6G Celicas Forums

ok.. so the wastegate actuator on my ct20b is fubared.. i get boost creep like crazi...

i was going to get an external wastegate to replace it and weld the internal one shut.

i just hv a question about size.

i was planning on getting a tial 38mm w/ either .5(7.252psi) or .6(8.702psi) bar... i hv an mbc and plan to run probably 10psi neway tho...

however, the shop my car is at, a customer has a 48mm wastegate but wants a 38mm and he said that customer is asking if i want the 48mm turbosmart wastegate in exchange for a tial 38mm...

i'm assuming 38mm is a good size for a 5sfte...

would i b better off w/ the tial 38mm or the turbosmart 48mm?
the 48mm seems kinda big... i'd possibly get a lot of lag?
not sure what other pros/cons there would be between the 2?

any help? thnx

This post has been edited by elvasoshexai: Nov 28, 2007 - 12:59 PM

Why 38mm? A 35mm is cheaper and capable of supporting more than enough power. My Supra had a Tial 40mm and I got 530WHP out of it. You get it too big, or too small and you get creep, spikes or both. I have a 1st gen Tial 35mm in my Celica and it works like a charm.

ESIT: Silly new Logitech wireless keyboard.

This post has been edited by OOBE: Nov 28, 2007 - 2:03 PM

tial don't make 35mm no more

Get a 38mm then.

but if i get the 48mm there won't be any cons right?

just a dent in your wallet

Dude, a 48mm wastegate hole is huge. You'll probably get boost problems. You don't need it. It's overkill. There are Mirage 4G93 engines in the island pumping over 400 WHP on 35mm wastegates like mine. Why spend more money and risk getting in trouble, when you can go for the tried and tested route? Get a 38mm and be done.

Stop spreading misinformation. You can't get "boost problems" with a larger wastegate. You can never "overwastegate" a turbo setup. The larger the wastegate valve, the lesser it has to move to evacuate exhaust flow. This also means faster control of boost since the valve only has to crack ever so slightly to maintain boost.

The only downside is cost and finding room to install a larger wastegate. Other than that, there are no downside in the performance aspect.

Also, no one rates wastegate with "WHP". It goes with manifold design and exhaust pressures. The lower the exhaust pressures, the more wastegate it needs. Every engine is different in terms of exhaust pressures. Anyhow. larger turbos always use large turbines which greatly reduce exhaust pressures, thus, we commonly read about the need for larger wastegates for larger turbos. Lastly, manifold design, such as the wastegate placement has the largest impact on wastegate sizing. A wastegate placement that is opposing the direction of exhaust flow will have a hard time redirecting exhaust out of the wastegate. A manifold such as that, would need more wastegate.

Example of a poor wastegate design that requires a larger wastegate... Notice how exhaust needs to turn the opposite direction to exit the wastegate:



Example of a good wastegate placement that requires a smaller wastegate:


This post has been edited by Tony_the_Tiger: Dec 2, 2007 - 9:25 AM

Why dont you just replace the broken actuator with a Forge Upgrated Actuator. Problem solved for 100 bucks.
This one

http://www.forgemotorsport.com/content.asp...product=FMACGT4

X2
less hassle.

I checked Forge's website and that would be $100 euros not including $55 shipping they quoted.
The total cost appear to $200 USD plus applicable taxes (14% in Canada). Definitely not a $100 solution.

I have the Forge internal actuator for my GT2871R in my turbo Integra, and their units work great but they don't last. Their diaphragms always end up ripping in matter of months, and I believe I am already on my 4th replacement diaphragm in the past 2 years.

This post has been edited by Tony_the_Tiger: Dec 5, 2007 - 10:54 AM

check ebay for new and used forged products

Follow your own advice, and don't spread misinformation.

38mm works excellent for me.

How's your setup going?

Just take it like a man and hit a few books, build a few cars before deciding to share a "tech post" of your own

I would love to see you quote where I misinformed anyone.

i was just asking myself what different size wastegates were for and after this discussion, its clear.
LIKE diluted mud . Can someone re-word? i follow, but want to be sure

Here's how wastegate really works... All it does is vent and redirect exhaust away from the turbo and bypasses it to maintain boost. The few main factors to consider are manifold/wastegate design, exhaust back pressure and the amount of boost you plan to run. Don't even look at WHP at all because I had cars in here at 300 WHP needing a 50mm wastegate.

If your manifold has a wastegate location that is in clear path of all manifold runners, then you can mostly get away with a smaller wastegate. If you have a manifold that has a wastegate location that only vents out one or two runners only and has a nasty bend, etc, then you may want a larger one.

If you are running a turbo biased with a much larger turbine housing and wheel, such as most Garrett GT series turbos (smallest compressor trim within its family), then it has more "turbine" then "compressor". Turbos will larger turbines will dramatically lower exhaust back pressures, and therefore, it requires more wastegate. The natural least restriction path for exhaust to flow out is through the turbo instead (because of big turbine and lower back pressures between turbo and exhaust ports), and it would mostly likely keep going through the turbo instead of going out of the wastegate if the wastegate is too small. AKA boost creep

Another thing to look at is the amount of boost you plan to run. If you have a really large turbo say a GT35R, and you somehow want to run only 6 PSI, this would require a much larger wastegate too. Assume that 100% of flow going through the turbo equals max boost of 20 PSI for example.. Now you want to run 6 psi kinda puts it at 30% through the turbo and 70% out of the wastegate. The lower the boost, the bigger the wastegate.

So all this boils down to really... Run the largest wastegate vs price that you can afford and physically fit in your engine bay. That is why the Tial 44mm became so popular because it was compact and it is the largest wastegate in its size without breaking the bank =)

hmmm... i wanna see where this is going...

Now, now, Jeunesse dont go starting fights lol..... Thanks Tony that clears it up alot for me, how can you tell if your wastegate is going bad? car wont build boost right? I think i was having this problem with my 3s, i just started noticing it before i got into my accident.