TurboMiata

At what point do you need to take the next step up to the 44mm wastegate? Is it by CFM, by boost, by HP? Whatever measurement it is, at what point do you need to make the jump?

Thanks

Civicman86

From what I have heard its more about how much pressure your running. Low boost then can get away with the smaller wastegate. Higher boost needs bigger. What is considered high and low Im not sure.

TurboMiata

Well, boost is relative. Running 6psi of boost on a viper V12 is not the same CFM/HP as 6psi on a B16a. I'm almost positive I'll hear that its CFM/HP related. None the less, what point is that at?

Blackack26

I think it also depends on the location of the wastegate, and the type of manifold you're using. I'm not 100% sure so I don't want to spread misinformation, just wanted to throw that idea up there.

seen4ever

it is related to CFMs...but i've never hear a clear cut line.

but Dustin you have it backwards, if you only plan to run big boost numbers on a big turbo (see t4..... or large t3 or big gt turbo on a big engine) then you won't have to vent off that much of the charge, so a 38mm will be fine. If you want to run 7psi on a gt4088r then you will need to vent off more gases, than at 44psi, so you'd need a 44mm gate.

Another consideration is if you wnat to run like 15psi and spray a big nitrous shot, you'd need bigger.

but if we are talking about a miata with a 1.8l engine, i'd think unless you plan to throw a big t3 or t4 on it, you could get away with a 38mm gate. just depends on your plans.

TurboMiata

I already have the old 35mm tial(and all the turbo components from the blue miata) for when the miata gets its boosting after classes end this spring and I graduate

In all honesty, we are talking about a turbo LS1. However, I suspected it was related to CFM or HP, thus it *shouldnt* matter what the app. 600hp on a honda is the same CFM as 600HP on a turbo Ls1. I do imagine pressure would come into play though, since more CFM is going to force its way through a 38mm hole @ 14psi than it would through that identical hole @ 6psi.

Lots of interesting thoughts. Keep them coming please guys.

dpetro1

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Turbosmart Website &raquo;</TD></TR><TR><TD CLASS="quote">
Big Turbo/Low Boost = Bigger Wastegate
Big Turbo/High Boost = Smaller Wastegate
Small Turbo/High Boost = Smaller Wastegate
Small Turbo/Low Boost = Bigger Wastegate </TD></TR></TABLE>

i pulled this little chart off the turbosmart website. it mirrors seen4ever's comment and looks like power doesnt have too much to do with wastegate size. what the cutoffs are for high/low boost and big/small turbos are im not too sure but hopefully this helps.

they also mention some stuff about how the valve lift plays a role in flow, instead of solely the valve diameter.

raene

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by TurboMiata &raquo;</TD></TR><TR><TD CLASS="quote">
I do imagine pressure would come into play though, since more CFM is going to force its way through a 38mm hole @ 14psi than it would through that identical hole @ 6psi. </TD></TR></TABLE>

You're thinking about intake pressure here. High TIP (turbine inlet pressure) will more easily vent as was stated earlier. But TIP is dependent on many many things... exhaust design, mani design, wastegate and turbine placement, head flow, yadda yadda... You can have the wonderful situation where you get higher intake mani pressure than TIP, even... The two somewhat go hand in hand but a more "efficient" setup will have lower TIP at the same boost pressure. The wastegate plays a role in this as well, keeping TIP low by having a straighter shot at the wastegate...

If you're at all worried I would upgrade. A big turbo will hit hard and fast, and a small wastegate won't be able to vent enough gas so you'll get a spike that tapers back down.

seen4ever

i would think if you go to a single turbo on a ls1, and i'd expect a t67 or so, t4 base, i'd get a 44mm gate, as if you just try to run 8psi or something low, you'd need to vent all that pressure as that big turbo spools up faster, it will spike. on a stock block ls1.....i'd not wanting a big spike to occur. hell look at dave's engine, 2.4l h22a with a t3/t61 and an offset wastegate position, it wouldn't hold 10psi, it would creep to 19psi and hold steady on a 35mm gate. all due to trying to run low boost, with the turbo coming on so hard, yet the gate not being able to vent off the air fast enough.

TurboMiata

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by raene &raquo;</TD></TR><TR><TD CLASS="quote">You're thinking about intake pressure here. High TIP (turbine inlet pressure) will more easily vent as was stated earlier. But TIP is dependent on many many things... exhaust design, mani design, wastegate and turbine placement, head flow, yadda yadda... You can have the wonderful situation where you get higher intake mani pressure than TIP, even... The two somewhat go hand in hand but a more "efficient" setup will have lower TIP at the same boost pressure. The wastegate plays a role in this as well, keeping TIP low by having a straighter shot at the wastegate...

If you're at all worried I would upgrade. A big turbo will hit hard and fast, and a small wastegate won't be able to vent enough gas so you'll get a spike that tapers back down. </TD></TR></TABLE>

Actually, I was thinking about the exhaust pressure. Running 14psi vs 6psi will result in more exhaust gas going out the exhaust valves. This in turn ends up with more pressure between the turbo and the exhaust valves, since pressure is simply a resistance to flow. It may not (and probably isnt) the difference of 8psi like 14vs6 is, but it most assuredly is a higher pressure just based solely on the CFM thats moving through a fixed size system. So more CFM would move through the fixed wastegate diameter size when running more boost based on this. Thats what I was getting at. Perhaps I worded it poor

Either way, with that stated, it just goes to reinforce the need for a larger wastegate @ low boost because the smaller diameter wastegate wouldnt be able to redirect around the turbo nearly as much gases because its a lower pressure. So... we are left with the previous of "a bigger hole is needed". At least thats my understanding of the reasoning?

Again guys, I appreciate the feedback here on this. Its echoing information I'm finding other places that say the same thing. Its a shame there isnt some clear cut answer...