It's not perfect, as you can see on my datalog I do still lose about 1 psi from peak of boost point to redline but with the wastegate vac line ran the way it was before I was getting almost a 4 psi drop over the same range. 1 psi overshoot and then a solid X target psi to redline is pretty damn near spot on optimal.
-Ryan

Knowing you're losing 2.5-3 psi in your intercooler and plumbing should be annoying you now. 20-25 percent of the compressor's work being thrown away is not good.

If it helps, for every pound of boost you are losing, your charge air temperature is also dropping :)

Garrett Actuator
 

I just put on a Garrett actuator from ATP.

WG-ACT-28RS-14PSI: atpturbo.com

Made a bracket, used a 2" extension (also from ATP), and tightened it down. It ran 1Bar falling to only .98Bar on the first run. So it's as simple as a better WG, something closer to the boost levels you actually want to run. I'll hopefully have new dyno chart in a week or two running 1Bar. It pulls like a BEAST!!! It's back to being SCARY to drive. Even my wife shit herself, and she was only doing about 1/2 throttle.

"I can't drive that, it's too fucking fast!"

She's been driving it around at 240whp (last tune) and never complained.

Let me bump this thread with a bit of manufacturer information for internal and external wastegates (disregarding the compressor outlet for the sake of this thread).

I was in the middle of trying to figure out what I was going to do for a source, but after reading Joe's explanation and seeing ThePass' information (good job btw!), I'll be installing a fitting post-IC/pre-TB.
Magnamx-5, I also took what you said into consideration because of Pat running his source off of the back of the intake manifold and because it makes sense, but after reading that quote from Garrett and a couple other places saying that vacuum can hurt the diaphragm, I'd rather be safe than sorry.

*edit* I just had a thought, what if one were to run a check valve so that the diaphragm is never exposed to vacuum?...

From what i see Vac hasnt hurt my diaphragm but the check valve would be a very workable solution for those who are worried.

does your seat still smell from your wifes shit?

Ray, this passenger-shit-effect, let me get this right, Greddy turbo, 1 bar boost, 1.6 with rods/pistons? Curious as I'd like to duplicate the effect eventually.

dont forget that he's using the aem. therefore his 240whp is way faster than a megasquirted 240whp. dont even think about disagreeing, its a fact.

Nah, she didn't get any on the seat.

It's still a stock 1.6l.

...the difference is the boost level that power was reached at.

What did you do to plug the source on the compressor housing ?

I just ziptied a little rubber cap on mine. So far so good.

1991 Eunos 1.6, t25 turbo, home made tubular manifold, home made 3" exhaust, 2" and 1 1/4" from turbo, intercooler, waste gate set to 5psi with switchable MBC 10psi.

Found this topic interesting I have sourced pressure for the waste gate/MBC from the cruise control port back of inlet manifold for the last 2 years. Didn't appreciate the potential problem with vacuum being applied to the actuator diaphram or the issue of potential over boosting/heat build up pre throttle body.

So I thought I would check things out. Does the pressure go high post compressor pre throttle body through the intercooler in part throttle situations as Joe suggests? Yesterday fitted take off point pre throttle body post intercooler and fitted second boost gauge to find out.

In part throttle running with the boost set to 5psi I was seeing almost 10psi on occasions from the pre throttle body gauge. On 10psi boost I was seeing over 15psi on a number of occasions. On each occasion I was not on anything like a real hill just a gentle incline. So Joe you got it right.... And of course with the extra pressure would have come unnecessary and unwanted additional heat.

So guess where I've now conected the take off for my boost control - yep post intercooler pre throttle body.


Malcolm

Having this second gauge fitted also showed something I hadn't appreciated - when you're running in vacuum (boost gauge showing this) there is already +ve pressure in the inlet pre throttle body. This fits in with why when a turbo is fitted and even driving technically off boost the engine feels more torquey, could this be because there is better cylinder filling.??

I think I'm going to give this a try today.

I currently take the boost signal from the compresser and have problems with boost overshoot, and holding boost until the redline.

I'm going to blank it off, then drill and tap the charge pipe pre throttle body and see what results I get.

I didn't realise taking the boost source from the manifold was a problem. I do now though! Good thread.

This was easy enough to fit so I had a go of it... but it was a bloody mess to make any sense of what was going on cuz in full boost, looking at two gauges was not too easy/useful.

THis sounded much better, so of course I asked Joe how to do it and thankfully he told me...

Logs attached... The first one is brief and includes a 2nd to 3rd shift WOT. THe second log is a boring mix of driving but includes a bit at WOT and also a part-throttle full-boost situation at about the 880 second mark, and some other dubious data for those much smarter than I to hopefully interpret.

Ideally, I suppose I should have tried a 4th gear pull from 2k rpm to redline but I didn't have the road for it. If you lot are interested, I can give it another go. I also may try to reference MBC post throttle just to see what's what.

Intercooler is a big Bell unit, MBC is set to ~10 with a reference just prior to throttle. THis was at sea level and the rest of the hardware is in my sig.


To overlay curves, "aux pressure" is what I called the second MAP sensor in MLV. The second MAP sensor is sourced at point "A" (compressor).

Enjoy.