Tial 44mm. However the fact that it is not even opening... sort of negates it from the equation don't you think?

I would think that if the crossover pressure were excessive that the wg would open off of spring pressure. And that my manifold pressure would be high (if it felt chocked I could see this not being the case but it's not), also I should see more knock counts.

??? IDK..... I will just measure it through the o2 bung this next weekend. Until then I'll just run low boost. I'm thinking about getting a high pressure MAP sensor and toggling between the two to data log it.

truly though, it just feels better so I am at a loss.

 

Good info guys!

sid why only one wg and not two? Space? keep us updated with this.

 

There really isn't a need for 2 wastegates. the only time you'll need something larger or dual 38mm gates is when running real high boost with alot of back pressure. people are running 38mm wastegates on 3L twincam engines and still havn't out flowed the wastegate.

 

So the exhaust flow in one pipe on a two pipe crossover doesnt get disturbed by the two pipes going into one wastegate? Like gases from one crossover pipe going into the other. Is that even possible? Sorry for the noob questions lol

 

Space is the issue. It is tied together with a plate separating the pipe. At this point I'm not even sure I'd need to tie it together other then to equalize the exhaust.

I will let everyone know what the crossover pressure is once I get time. I think I'm going to just use a max hold pressure gauge rather tgsn go through the trouble of adding a map sensor.

 

Got any pics of your crossover setup?

 

https://rennlist.com/forums/944-turb...oll-setup.html

 

In fact, you need a larger wastegate if you run less boost. High compression, large capacity and low boost requires the largest wastegate.

 

Higher backpressure with larger piping sounds fishy indeed
It's heat that drives the turbo, the large piping might loose enough heat to limit boost.
Maybe you should just get a smaller turbine.

 

Sid you might have something else going on there, I forgot you had that wastegate setup.
I am not familiar with that turbine housing so it may behave a little differently to the gt30 t3's that I have used, but as for the pipes yes bigger equals more back pressure, 2x2" perform well but slightly smaller is even better(on a T3 divided).Believe me we were surprised.

 

Sorry, yes thats true. late nights do something to your head


Sorry you have a good point. in blown's Xover his got a waste gate to 1 pipe only. the other pipe has nothing from what i see. I totally forgot he had a twin xover pipe when i answered it.

 

Larger pipe, same flow = lower velocity, less pressure drop

 

Not really, since when would a larger exhaust give more back pressure than a small exhaust....

Thingo, I appreciate real life results but generally speaking:

A given amount of gas need to flow from point A (headers) to point B (turbine).
To transport X liters of gas in Y distance, velocity needs to be doubled if the flow is reduced to half.
Increase the flow capacity by 100% and the pressure can be reduced to 50% for the same amount of gas transportation in the same time period.

That said, different tubing setups can yield different results but I don't see anyway around what I'm saying above. Larger diameter gives lower back pressure. Thingo, did you really use the same turbine housing after the diameter switch?

 

I am quite familiar with the theory that is why I had the larger pipes made, but 2x2'' pipes had about 3 psi more back pressure than 2x1.75, the smaller pipes spooled about 200rpm sooner, and the the small pipes have more 'snap' on the road(more responsive) no power difference. Same turbo same headers(sfr stage 1).T3 1.06 divided housing.
As the exhaust eventually tapers down to the nozzle at the turbine wheel I think there is an optimum size pipe(though it could be overall volume), and it may different to what I am running even.

 

Very interesting indeed. Clearly a case of where real life testing shows that the many more parameters in a real life situation can give unexpected results compared to a basic calculation.