After burner

The reason you get a benefit from a bridgeport on a REW is from all the additional port overlap which creates a scavenging affect at high RPM. The exhaust literally starts sucking the intake air in. Has nothing to do with air or fuel going into the exhaust manifold, that only helps the turbo spool but does nothing for power. But then with all that additional overlap, exhaust tuning becomes important even for turbo. The setup needs to have a nice free flowing exhaust and now the turbo needs a high A/R turbine housing to not choke it at high RPM where the scavenging starts to come into play which it can't do if the exhaust backpressure is going up. So unless you add a perry exhaust on a renny, a bridgeport is not going to do much.

thewird

If it helps the turbo spool as you say .............. then it is effectively making power at the same time .It takes power (aka pressure and heat ) to drive the turbine.
So if the engine doesn't have to provide as much power to drive the turbine ............... it makes more power at the crank !

The engine isn't providing anything. Once the exhaust is coming out, it doesn't matter where it goes. The only power your getting is from the boost thats coming earlier but once your at full boost, it does not matter. And because more overlap moves the engine efficiency (powerband) up, your making less torque down low where the turbo is getting more boost sooner now so you might not even be making any additional power down low either compared to a stock port despite the greater boost.

A typical bridgeport makes peak torque around 7000-8000 RPM depending on the size. Your turbo setup needs to be setup with that in mind (bigger exhaust, bigger turbine, and turbine housing a/r etc.) but I don't think the renny has enough overlap or exhaust flow to make it work without introducing a perry exhaust.

thewird

Exactly ........... the engine isn't providing all the power to drive the turbine ,some of it is coming from the air/fuel mix that is bypassing the combustion chamber .

agreed ........ there is no way that the renesis can bypass anywhere near as much air no matter how low the turbine backpressure is ..........due to the lack of exhaust overlap.

The issue of bypass due to overlap is moot if the turbo is too restrictive. If exhaust pressure is substantially higher than intake pressure you will not get very much air/fuel passing through in the overlap window, depending on how much back pressure and how poorly tuned the exhaust/intake are you could even get more EGR and lose power.

ALS systems only work at low load because that's the only time you can feed intake air into the turbo exhaust housing. At high load the back-pressure wont allow it, but that's also where you don't need it.

Also with a undersized turbo the bridgeport adds very little because the restriction is the turbo. If you are going to put a major restriction in an air line you put it last, because it increases the pressure, and decreases the velocity through all restrictions before it. This is also why you want to be as free flowing as possible after the turbo.

Yes , I was actually hoping to improve the midrange with the bridge . In that range I do have higher manifold pressure than exhaust . When this didn't happen I started thinking about why it does work on a PP and not a Renesis.


But ... with a PP engine you actually can feed intake air into the exhaust housing .If you have a spare housing and rotor around .......... have a look at what is happening at the point where the rotor has pretty much finished pushing the exhaust gases out . At this point the bridge and PP are fully open and the pressure within the chamber will be at its lowest point . The PP stays open for many degrees of rotation while in this state (whereas a Renesis exhaust port is already long closed). Where do you think all this extra flow a Bridgeported PP engine has , is actually going ?How can 40% or more air go into the next combustion cycle cycle when the area it has to go into is miniscule ?
At this point in the cycle there is only one place to go , and that is out of the exhaust port .

Hmm. At what RPM were you making 15psi, and was that measured at the turbo or at the manifold?

Also did you try pulling timing in the mid-range?

I do see your point, but something here still doesn't add up.

It makes 15 psi at around 3700rpm (manifold)... and you can see the turbine backpressure vs rpm on the previous page .

Not really concerned about the fact that mine didn't work . I just thought it interesting to look at my results vs the PP setups that do work.
My theory stacks up if you consider what happened in my case vs what happens on a PP bridge .

Well I commend you for trying it. Maybe it is as simple as that.

Cheers .
I would still have expected at least some small gains from doing it . Even if it just filled the dead area that is present after the exhaust closes, with clean air/fuel instead of exhaust gas . I haven't completely ruled out that possibility yet. The overlay of the before and after dyno is pretty much identical . But the AFrs on the bridgeport dyno were much leaner (11.5 vs 10.0) . Maybe if i had made afrs the same I would see some gain ....................... (running E50)

I think you need to pull timing then pull fuel. Then slowly add back timing,.

Holy shit man. The amount of Mathammer you've put into this is absurd. I love it.

I'm interested to see what you find when you play with your real time timing adjustments . Although my gut feeling is you will be disappointed with the results.

I don't disagree with you ... although I don't even know what a Mathammer is ...............

Maybe, but there is only one way to find out. Also I have basic ion sensing working now so I wont be flying blind.
I think there is still some magic hidden in the Renesis, but even if it is a waste of time it's my time to waste.

So ......... I got this little puppy installed :

https://cimg3.ibsrv.net/gimg/www.rx8...11a8e19ffa.jpg

Have it set to turn off boost controller on alarm . Seems to work well so far .

https://cimg6.ibsrv.net/gimg/www.rx8...0b169eb427.jpg

you got weird looking puppies down under

No, no, no... The point is moar bewst, not less... :nono:

What boost controller are you running? My HKS EVC-S cuts boost abruptly if you set it to cut 100%. But I have never pushed past 13psi.

I've been running one for a couple of years. I have it doing the same thing...works well. It safe moded me when my fuel pressure regulator decided to crap itself......well worth the cost. And it's a cool toy to play with 😎

Good to know . On the rare occasion that I take it to the track it will be good to have some piece of mind .

Have you tried getting the rpm sorted ? If so ............. how did you do it ?

It's a Greddy spec11 . The AEM just interrupts the wires to the solenoid , works the same way for any BC .

Great, you guys are convincing me I've got more stuff to buy :lol:

Your not going to get a benefit from a bridgeport unless you eliminate your backpressure. The only power gain comes from the exhaust siphoning the air in and flushing the chamber (cleaning excess exhaust gas), not wasted air/fuel going out the exhaust which only helps spool. The only way you can make turbo power on a bridge is by running large A/R turbo's which defeats the spool benefit but actually gives you the bridge mid to top-end power. There is zero benefit on a bridgeport in the low-end no matter what you do, its actually negative gains.

The AEM wideband failsafe works good but the their water/meth failsafe is garbage.

thewird