Another way to answer this without 5 sentences:
If you search, you will find there are different schools of thought, and no one right way is the right way.

http://www.evolutionm.net/forums/evo...l#post11547918

Quote:

Originally Posted by Ted B

I don't know if that is the situation in your case, but be advised there is no reason to use a WG spring combination that works out to a pressure of any less than what you expect to run on base fuel. In my case, that works out to ~1.5 bar, and that is the tension of my WG spring combo. On pump fuel, the only means of boost control I need is the base tension of the WG springs.

Using less WG spring pressure only invites issues, including less boost control at high pressures.

"Controlling boost with the wastegate spring.

http://www.sr20-forum.com/informatio...-up-boost.html

One, expensive, complicated, limiting way of raising the amount of pressure the turbo outputs involves swapping the low pressure spring in an external wastegate to a higher pressure spring. This gets expensive and time consuming if you're looking to move from low pressure to high pressure in stages as most tuners like to tune in stages. Once the high pressure spring is in, there's no simple/quick way to run lower boost pressure either (valet mode, etc).
All in all, it's a pain in my opinion, and most people don't do it this way. They get the lowest pressure spring they can (to allow for low boost) or they just work with what ever comes with the wastegate."


If we consider the sources, evolution forum folks are more likely to want to keep 20+ psi under the hood for their daily drivers, whereas the sr20 folks are more likely to keep their low boost setting around 7 or 10psi, with 20 being a death sentence in many cases. Both are correct. I suspect rx7 fellow feels more like an evolution guy, where I feel more conservative and actually do own an sr20det in fact, and it is set to 7psi for daily.

 

Trust me I use from 4lbs to everything on the street and make it work

 

Haha. Thanks. No point in posting anymore, all it does is confuse people because he will post a 10000 word thesis

 

This is getting deep

EGP = [Spring Seat pressure - (Intake manifold pressure * diaphargm area"^2)] / wgexhaustvalvearea"^2

Example:

EGP = ([150psi - (15.4psi * 7.5)] / 2.2)
EGP = 15.6psi

For an intake manifold final pressure of 15.4psi, with a spring seat pressure of 150psi, diaphragm area of 7.5"sq, and wg exhaust valve area of 2.2"sq, there is an exhaust gas pressure of 15.6psi


Because of the enormous diaphragm area compared to wg exhaust valve area, the intake pressure will have a much greater influence opening the wastegate than exhaust pressure. I suggest a novice ignore exhaust gas pressure influences for his/her first spring, as there are much more important influences on wastegate performance, such as pre-load, boost controller settings, position, size, manufacturer, etc... is my opinion.

Yes EGP plays a role in when the gate will open. But a novice will have little control over EGP, without data collection and fabrication skills/spending money on new parts and further testing. Instead, they should use those things they can control easily, such as pre-load, or buying a high quality product, for maintaining the performance of their gate. This is an advanced tuning subject. If this isn't the heart of my position I don't know how else to put it. it's nearly one of the most difficult parts of the vehicle to achieve any semblance of beauty and elegance (turbo plumbing in general).

dat egp aint gonna matta in the end of thing for da beginner.

The last thing this guy needs to worry about is his egp. Hes gonna a hard enough time sealing up all the new plumbing and keeping it cool, writing new ignition maps and upgrading fuel system, preparing drivetrain parts for the rigors of boost. Aint nobody got time for egp!

 

I'm sorry but you aren't even ballpark with the ratios.

Tial mvs 38 is valve face is 70% of the diaphragm in surface area

 

You are welcome to plug any numbers you wish into the formula- you can easily add a weight to your own spring (if you would like an example I will make one) and get the spring rate, then work through above formula to get egp without needing a gauge. And it accents an important aspect of wastegates in general, that is, they all seem to be different sizes and designs, just like turbo plumbing.

It sounds crazy to tell a guy who is designing his first ever turbo setup to try to calculate his egp before buying his first gate, filling his head with worry that his first wastegate is going to be too soft. That is absolutely ridiculous.

If anything we should be telling him to wire the gate full open, so he can go WOT without a drip of boost, allowing him to gain tuning knowledge at safer pressure ratios first. THEN go for the 7psi spring, tune more, learn more.

And finally, if you think the engine will handle it, choose your best guess max spring for the fuel you are using and anticipated environment. If I want 25psi I will choose a 15 or 17psi spring. 25psi on pump gas methanol injection is a safe 550bhp bet for many V8 engines IMO, easily above the OEM piston limitation for a reliable 150,000miles daily driver. That is my favorite part and have more experience with it than exhaust gas pressure monitoring but it is off topic.


extra info--> I never specify displacement, year, make, model of the V8 in question. In my mind, I was thinking worst case scenario, new enough to have modern EFI. The MAIN IDEA of the paragraph was how you choose a wastegate spring, not how much power an engine could make, I paid very little attention to the fast example I worked up in my head for minimal power output when providing it, for choosing a 25psi spring as an example. I am always tuning 400rwhp with 18psi on 2.0L engines and I am well aware that 18psi used 100% effectively by 5.0L~ displacement spinning 7k~ is going to be 800-1000 horsepower.

I have the simple calculation here,
CID X RPM / 3456 = CFM @ 100% VE

Using 1992 TPI L98,
350 x 5800 / 3456 = 587CFM

587CFM * .069 = 40.5lb/min @ 100% VE (400 horsepower, "turbocharged" with 0psi of boost)
The TPI engine actually produces 296 horsepower @ 5600rpm
source:
https://www.eecis.udel.edu/~davis/z2...age021105.html

Even with such poor VE, 15psi should still nearly double you to 600 horsepower:

Here is another V8 turbo example more close to what is in question:
http://www.theturboforums.com/thread...k-TPI-How-fast

And there is also somebody using 12psi on the TPI engine, making 350-400 horsepower:
http://www.thirdgen.org/forums/power...ngle-60mm.html

Yeah they could probably get pretty close to 500 with 18, where the other guy only needs 11. Because of this variability, I use 500rwhp (550bhp) as a minimum, since if I said the opposite (that 13psi always gives us 600bhp) that could also be laughed at. The OEM camshaft is really a serious bottleneck, my example holds in these situations using the OEM valvetrain and TPI because of it, and the fact I never specify displacement or year, since we are discussing wastegates, not engine VE. My central idea was "25psi is more than a novice will ever need since his OEM bottom end limitation prevents the use of such high boost pressure" making the spring selection for 25psi (15 to 17psi wg spring) a little too much, but useful for the example of how to choose the spring, nonetheless.

 

Yup I'm done responding to a block of wood

 

25psi and 550bhp for many V8 engines, lol. You have more experience with it than monitoring back pressure? Every post you've had in this thread has been a joke. That one just proves how full of **** you are.

 

You can't fix stupid no matter how hard you try.

 

Well yes...if your V8 was maybe a 2.3- 2.5 or something.

Whilst everything you say is not dumb....you dont help yourself either.

And writing bucket loads of text which does contain a lot of dumb, doesnt help either when really you end up making it all sound dumb.

Really, this thread needs to end.

 

A bone stock 5.7L V8 89-93 with support 550bhp @ 24-25psi of boost, with turbo maxing/pressing just off the right of compressor map (55lb/min~)

I also said it is "above" the oem piston limit, by which I meant too much. I wouldnt try more than 10-14psi if I wanted 100,000 more miles. That could also be 500-550bhp, depending on which OEM engine we are talking about (newer engines).

Are you trying to say it will make less? because it definitely will not make less, even the old ones. That is why I posted the minimum number, along with "safe bet" because the minimum is always a safe bet. It is not wrong you just cant read. maybe its my lack of puncuat, punctian... opunctuation. and peeling. Or maybe everyone is women? Women has problems following logic like this, whilst i can has cheese.


You should be able to pull 600 out of 10psi of boost, or even without boost if you have a say in your parts combinations and choose well, the sky is the limit really, since an engine can be built to maximize RPM, say 9,000rpm, or 19,000rpm, or 190,000rpm, or 1,900,000rpm, I am using dramatic examples in my posts which I think is throwing you practical minded people off. By showing the extreme edges of a system (a graph for example) I am detailing the behavior at those extreme edges- the bottom line may or may not include these situations but they still stand as examples.

 

Dude, you're seriously on drugs if you think any 5.7L V8 will take 25psi of boost to make 550hp, or if you think a turbo capable of flowing only 55lb will create anywhere near 25psi boost on that same engine.

The statement and then an attempt to back it up....really, words almost fail me.

Stop posting.

 

It is a minimum number, a safe bet. Why cant you see that? I wasn't going to imply on a public forum, without specifying year/model, than any random V8 would make 600+, because many will fail internally, and others still may have too anemic of a camshaft/valvetrain for that kind of service, and I feel that is beyond the OEM Head gaskets limitation in many cases as well. I also wasn't going to put down 500 or less, because lets face it, 25psi even on it's worst day from the worst blower will produce more than 500. So I settled on a nice safe bridge between them, 550. The turbo I supplied as a hard limitation at 55~lb/min. The ~ implies a variable. I would never install a 55lb/min turbo by itself on any V8 engine, it was just to cap the power output for the sake of example. Some Evolutions run 45lb/min turbos and squeeze 520+ horsepower from them, so it really doesn't matter anyways.

 

What in the name of ****......

 

Back to EMAP discussion,

I asked evo owners about real world gates (I dont have a real gate to test), to which I received the best reply,


1. If my target boost max was 20psi, and I anticipate buying a 10psi spring and turning it up, how much exhaust gas pressure would it take to start interfering with my intake manifold pressure? Is there an anticipatory ratio of drive pressure like 2:1 I should be concerned about?


2. Would a good electronic boost controller be able to remove alot of that issue?


3. Does an early opening gate due to high EGP contribute to lower intake manifold pressures, or only slower boost rising rates, or both? i.e. if I buy a 15psi gate spring, and my combo has a LOT of EGP, will it deny me a full 15psi of intake manifold pressure? If so, how much lower could it become?


4. Doesn't a larger diaphragm allow for a larger spring to be used, and thus larger springs/diaphragm combos (although slower) able to resist more Exhaust gas pressure? Is there any company that offers a special "robust diaphragm/spring" combo for this situation?



5. Lets say I buy a 15psi gate but it comes on very very slow due to an early crack because of high EGP. If I buy a stiffer spring, isn't that the same as raising the boost pressure? In other words, if I ever have an EGP problem, buying a stiffer spring will just increase the boost pressure on me- it isn't really a good solution because now I am over boosting (compared to before). How can I buy a stiffer spring without getting more max boost?


cliffs: buy a spring that fits the wastegate for your application, play with pre-load and Electronic boost controller, profit.

 

Seriously dude STFU it's getting old.

 

I am contributing information to the thread. Until the day moderation includes preventing people from posting relevant information, I should not stop for it is free technical perspective and entertainment. You do not have to read it! Why are you reading this right now? Stop reading it!




381,420 people be acting like I am forcing them to read what I write

 

The forum is supposed to be for help, for useful technical information.

Not for people to type tons of bullshit to readers who may not appreciate it is bullshit and then confuse them as they havent a clue what to believe.

In this thread, you are falling into the typing tons of bullshit category. Other than to make people laugh at you, it serves no purpose here.

Simplified and correct answers have already been given. This thread needs to end to prevent further contamination with bullshit.

 

Here is your chance to laugh. In a hypothetical situation where a guy bought a China gate which was supplied with 2 sets of springs with neither labeled--where would he go from there. Chunk it in the garbage and go spend mega bucks on a good name brand or just wait until he gets the engine going and see what happens with a gauge or try to find a spring with a label.

 

What part of that didn't you understand?