Face to ******* palm.


Probably half the turbo setups in here....

 

But you would realize this if you had collected any real world data instead of just talking to talk talk talk to talk

 

Probably 90% of the boosted 5.3s on the site fit this criteria jackass. Why are you arguing with the veteran members here that go out of their way to help the novices get their cars going safely and reliably.

 

Let me take a crack at this and to the rest of you, if I am wrong, be gentle. The after market manufactures don't adjust the diameters of their valves based on boost pressure. I think you are assuming they do. The 14 lb spring on a smaller waste gate is going to be less stiff than the 14 lb spring on a larger gate. I think you are assuming they are the same. One of the reasons they have larger gates is to allow for the higher flow of a larger engine. If you are not making these assumptions, then I have no idea what you are talking about.

 

Well I had no idea. I said I didn't pretend to have any real world data. This comes as a shock to me, to be honest. Ill have to think about it. The book clearly says that a traditional 900 horsepower V8 engine would have 10psi more in the intake manifold than in the exhaust, when operating effectively. I thought that was a kind of standard.

So a new interesting question. If all of the V8's running around 7psi in the intake manifold have 14psi in their exhaust systems, and this is such a big problem, why dont they need 14psi wastegates to achieve 7psi? Or do they.

 

Forget my previous. I had no idea you did not understand that.

 

Did I do that? Urkle said

 

This right here is your problem, library warrior

 

I was getting to what you posted,


I am really happen to see this kind of thinking and it is something I brought up a few times. The influence the exhaust system has (the leverage exhaust pressure has on the WG valve) is related to the surface area of the valve itself- am I right? Thinking along these lines, larger wastegates would be easier to open. So engines that flow more, which need larger gates, have more trouble keeping them shut and need higher spring pressures. That is, the larger the gate, the more influence each 1psi of exhaust gas pressure will have at opening the valve. Since the larger gates are usually reserved for 500+horsepower applications (I could use internal gates at 600 on a twin setup easily) I thought it best to leave these out of our novice discussion, vaguely aware in the back of my mind that at some point, exhaust gas pressure does need to be considered.

Once I pass about 400-500rwhp I stop thinking about novice applications. I feel like 500 is about it for the OEM bottom end of various V8s in production. That said, to hit 500 or just 480rwhp is not difficult with 10-12psi of boost on any random OEM V8 of 5L-6L. To me, this is novice territory. These guys want to run 10psi, they completely ignore their exhaust gas pressure estimations and buy a 10psi wastegate, and it works to provide 10psi of boost.

Thanks to the manufacturer of the spring, and the calculations done involving the diamter of the valve and it's diaphragm, it should tolerates a wide range of exhaust pressures (perhaps from 5 to 10 extra psi?) and still, by referencing the atmosphere, provide a consistent performance holding its advertised boost pressure. Now, if I am wrong about that, and people are indeed using 15psi gates on their 7psi setups because of the 15psi of exhaust gas backpressure, then so sue me im wrong. But I do not think that is the case. I like to believe that anyone running 7psi in their intake manifold has a 7psi gate installed, even if their exhaust gas pressure really is 14psi. If t he valve cracks too early you hold it down with a profec B spec-II or something. It really isn't a big deal, there is no need to consider exhaust gas pressure (to care about it when selecting a gate at this level) in my opinion, but I'd really like to hear from someone who has a 7psi V8 with 14psi in the exhaust for confirmation as to what gate solutions work.

 

And this is true, if you are running a 1.5L turbo indycar motor that is .7-.8:1 backpressure at 40-60+# of boost.

There are VERY few members on this site that are even in the 1-1.5:1 BP ratio and I can probably count on one hand (rotary1307cc being one of them) those who have figured out how to get below 1:1.

 

Hard pressed to see that even in max effort, max efficiency stuff


This isn't like the small displacement stuff.

Think of it this way


Small displacement motors, to change the mass flow out the exhaust boost pressure and drive pressure increase alot and together

With large displacement, a relatively small change in boost pressure can increase the exhaust mass flow a ton.

 

They don't buy 14psi wastegates. They aren't rated in psi. They are rated in size of valve. You get a gate that is large enough and put the 14psi spring for that gate in. Once again, to the rest of you, if I am wrong, be gentle.

 

So to follow this logic. If I am moving 450 horsepower. I buy a gate for 500horsepower~ and put in my 15psi spring.

Now my engine operates at 15psi off the wastegate. However my exhaust gas pressure is 30psi? Isn't this kind of what I was saying earlier, how even though the owner never cared about the exhaust gas pressure, he/she still purchased the correct gate because it still works to provide 15psi even if the exhaust gas pressure is rising significantly? If it cracks too early I just hold it down with an electronic boost controller?

 

you pick your gate size based on how much mass flow it can handle and the amount of boost you need to run.

a 6.0L running at 5# needs a gate to flow much more than a 6.0L at 15#.

by the same token you want to run the smallest gate you can as they are much faster to react and have less surface area, leading to less of a impact from exhaust pressure. This is why it is better to use two smaller gates rather than 1 larger one

 

If you buy a 15 psi spring and you have a 2:1 ratio you will have 7.5 psi on the intake. Gates are not rated in hp.

 

So anyone using 15psi on the intake manifold of a 2:1 ratio combination has 30psi in their exhaust system, and is using a 30psi wastegate spring? For some reason this sounds absurd, and you say this is pretty common?! I just find it hard to believe. Wouldn't folks be complaining left and right that their 15psi spring only supports 7psi if the 2:1 ratio problem is so common? I just, don't see it.

 

Ever heard of applying pressure to the top of the dome??

 

You referenced injecting CO2 for this. Boost controllers connect here on an external gate, plumbed to the top to limit pressure from a source to help keep the WG shut longer. I am still curious about the wastegates people are choosing for their setups, are they seriously buying springs with double the rating for their V8 turbo engines in prediction of high backpressure troubles? I want to get the scoop on this. Can we make a poll? Something like, "On your turbo V8, did a 15psi wastegate spring give you 15psi or 10psi or 5psi" etc... because this is really something to be aware of it, if its as big of a deal (over half of turbo setups promoted on this site are 2:1, double spring pressure gated?)

On a more light topic, I have been able to watch 6+ males trying to close the wastegate for a 900rwhp 2.6L engine, using all of them piled up together on a block of wood after about 30 minutes they managed to get it sealed shut. The spring is serious sometimes.

 

No it doesn't need to be co2

Can take a simple 4 port solenoid and use it to remove the lower reference while adding ontop of the diaphragm.

You can run a 2lb spring and run anywhere from spring pressure all the way to flat out on that light spring..... Using nothing more than a simple solenoid and boost as your supply

 

You must have missed this thread...

https://ls1tech.com/forums/forced-in...asurement.html

In a conversation I had with a Garret engineer, back in 05 or so, we discussed exhaust/ intake pressure to some extent & the new turbine wheels they had released in the GT series turbos.

It revolved around Ford Powerstroke engine development. Ford found issue with their new turbine wheels impacting EGR function as exhaust BP was less than intake pressure. Ford wanted them to use "Less efficient" wheels & Garret told them to pound sand & find a way around it. Nemo's Axiom was supposedly turned on its ear at this point.

The recent turbo exhaust back pressure thread had me wondering how many have logged an actual under axiom event.