Hi,

I need a little advice (stock car with TBE):

I can reach high max boost in 3-5k rpm (27 psi, with lowered WGDC set to 25-26), but after 5k RPM it falls REALLY quickly down to 18 psi.

Would removing the pill allow increased boost it the higher RPM?

Thanks for advice.

 

While trying to increase the high RPM bost I have found that retarding exhaust valve to like -5 in the cells where boost drops (5-7 k rpm 200-240 load) can increase it. Now I can get 19-20 at redline, before only 18 psi.

Can someone confirm it?

 

Which direction are you coming from? 0 or -10.

 

From zero, I have forgotten to mention

 

yes but you will not be able to hold it.

 

need to crush the stock bov and get a new wastegate

 

or just tighten up the stock wastegate for free

 

hmmm, what are risks of doing this? I am an IT person and usually prefer SW changes to HW

 

The WGA is not the reason for not holding boost. It's the turbo. There are only 2 ways the stock turbo will hold more boost in the upper RPM range.

1. Create some form of restriction in the engine so that air has a harder time entering or exiting the engine. Examples would be smaller valves, bad cam timing, restrictive exhaust...

2. Create more heat after the turbo. That will cause the air to expand and create more pressure. This will cause a loss of power and possible detonation.

Notice that no where in there did I say that you could increase the flow of the stock turbo. You can't. Sorry. Upgrade the turbo if you are not happy. I did.

 

Umm I went from holding 17.5 psi at 7k to 20 psi at 7k just by tightening up the wastegate. Proved by before and after logs so take that how you wish.

 

Then you are doing a combination of both 1 and 2.

PSI does not equal power.

 

This is true.

I can hit max psi at 3k RPM with boost dipping untill 4k. Even though I feel while doing the WOT pull that "torque seems much lower" in 3-4k, TQ curve in VDR goes up even with boost going down, despite the personal feeling.

 

I'm not sure that is correct. Tightening the wastegate is generally akin to getting a stiffer spring in there... that doesn't mean there is a restriction in the engine. It may mean there is more heat post-turbo, but that would have an inverse effect.

Sometimes there can be enough pressure in the turbo to blow the wastegate open... even if you are preventing any positive boost pressure from opening it.

Will this effect be reduced over time if the spring wears out? ...possibly, but it definitely works as a mechanical advantage to gain more boost (and hopefully... power). I agree that more PSI does not equal more power, but if you use it to attain the same boost level I imagine it would mean a slightly cooler charge and possibly slightly more power.

 

Not to mention I picked up PSI through out the entire boost curve on top of holding more boost at red line. With the addition of a FMIC I picked up 4 tenths in the 1/4 mile two weeks apart and I doubt very much it was only from the FMIC so there is power to be gained. The mod itself takes an hour to do so very much worth it IMO

 

You explain #2 perfectly.

My reasoning for #1 is that I've tuned many, many stock turbos. They don't hit 20 PSI at 7000 RPM on the Stock Turbo without some kind of serious restriction. Even if you weld the Waste Gate shut, you won't see that on a normal X. And by normal I mean normal mods.

You cannot make the stock turbo flow more air, therefor there must be something restricting flow at 7000 RPM preventing air flow. As soon as the engine flows less air than the turbo can push, you will see pressure build up between the engine and turbo... aka boost pressure in the intake manifold.