Ok so i have this problem now with my new turbo. I ended up taking my cheap egay turbo off an went with a holset he351ve vgt housing. Its about a 22cm2 housing maybe a little bigger. But anyway heres my set up as of right now. Half bridge posted exhaust. 2.5" exhaust manifold with 50mm wastegate. 3" exhaust 2.5 intercooler piping. an megasquirt ems.

But whats going on is that ill shift an loost pretty much all my boost. then have to build it up agian. I was reading around that a smaller wastegate will help this but is more prone to spiking. Also i was reading that for a car with higher boost a smaller wastegate would aid in keeping the wheel spining faster. Please let me know cause i got beat by a ******* evo. i get full boost around 4500-4800 in first then 4000 in second

 

the effective area of the housing depends on the position of the sliding nozzle on Holsets or the position of the vanes on other designs.

This is why I don't see much of a point in running a variable geometry turbo on an application it wasn't designed for. These turbos are supposed to be run without a wastegate, using only the variable geometry system to control boost.

That's wishful thinking. Or maybe internet engineering. When you close the throttle, there is no exhaust driving the turbo. Boost is going to drop, at least on these ancient cars. Some newer turbo cars with electronic throttles don't close the throttle valve between shifts. BMW N54 engines keep the throttle open and just pull timing when you let off the gas pedal between shifts. They lose much less boost (this is the manual transmission engines).

Now, how quickly you build the boost back up after the shift depends on how the boost control is set up (gate spring pressure, adjustment of the boost controller, etc) but also the exhaust manifold, turbine housing, and all those other factors that affect spool.

And you think that's bad? It's not amazing spool but there are certainly people here running laggier setups. How are you falling below 4000rpm between shifts though considering the gearing of turbo Rx-7 transmissions? When are you shifting.

No offense, but it sounds like your car doesn't have the power you think it does.

 

I have the vgt welded shut so thats not the problem i have the vanes in the right holes also. Im not using the electronic wastegate. I never said anything about the power of the car i know it has the power to do what i want it to do. My biggest problem is just building boost after i shift.

 

post a datalog which shows boost as you shift

 

i figured it out i just turned my boost controller up. Now it holds an spins through second. That big of a turbo i guess needed more boost to keep it spinning. But im pretty sure that evo was not stock cause i spank stock/modded evos alot.

 

What do you mean by VGT welded shut, what position were the vanes in when you welded it?

 

curious as well, the holset vgts are very good turbos but I dont know if its the best turbo for our engines, in fact I doubt it is since the VGT is not being used.

 

Forcing the VGT system into one position and then running a wastegate defeats the whole purpose of a VGT turbo.

 

the lever on the side is so the vanes are pushed closed. I just have the level tached i dont think i would have the skills to weld the vanes ahahaha. But thats why i did that i know i defeted the purpose of the vgt. I just wanted the turbo for the size. What we did was wired it shut as far as we could get it with out breaking it an tached it in that position. Now that i upped my boost i really dont have much problem i still wanna try an experiment with smaller wastegates see how or what it changes.