Weird boost happenings after I/C install (long)

[Guest bastaad525]

Got my I/C in yesterday, and since then, there have been some odd things going on with my boost settings.

 

 

I'm using a grainger ball valve style DIY manual boost controller. It's currently getting it's signal from the two stock locations on the compressor housing, and is connected by very short hoses from there and to the wastegate actuator to keep spiking to a minimum.

 

Before the I/C install, I had it set to run at 10psi. It was very consistent... it would always spike to about 11psi very very briefly, and settle at 10psi + or - .5 psi, regardless of gear or speed.

 

After installing the I/C, boost is all over the place. I had some weird problems that led me to believe the ball valve was sticking open, causing the car to run at stock boost. Removed it and cleaned it, things went back to normal. Then it acted up again on the way to work. Cleaned it again, now it's back to normal (well okay not normal, but at least running somewhat at the boost I set it too as opposed to just stock boost) and stayed that way the whole drive home and a few trips around the block. There was no dirt that I could see on the inside, when I opened it to clean it.

 

Now the odd stuff.

 

For one, lag has gotten horrible, BUT, ONLY in FIRST GEAR. Doing a rolling start I could always get full boost at 10psi, by 3000rpm, before the I/C. Now it takes a lonnnnnnnng time to hit full boost from a rolling start, somewhere between 4000-5000rpm... basically it bogs, then boost hits, and I almost immediately have to shift after.

 

But in any other gear, lag is only barely increased at all from before. If I'm cruising in any other gear, even decellerating, foot off the pedal, and floor it, boost comes on just about as fast as it always has, maybe a half second slower... barely noticeable.

 

The second oddity.... boost level now varies greatly with RPM at WOT. Lets say I'm in 3rd, cruising at 2500rpm, and floor it. Boost will 'spike' up to somewhere around 10psi, but it's a prolonged spike... way prolonged. It will stay up at that level, only slowly tapering off, by 4000rpm it will be at 9-10, and by 5000-5500rpm it will have settled at about 8, which was my target boost all along. In higher gears it's even more noticeable, and final boost level is a bit higher in each higher gear (9ish in 4th, dont know in 5th because I wont go fast enough for the revs to get that high). If I floor it in fifth at 2500rpm, it will go up to 11psi, maybe even 12, and of course it will stay there for a while as revs are climbing much more slowly in 5th, but it does slowly taper off to around 10 before I just wont stay on it any longer.

 

By the way, I did check how much of a pressure drop there is now with the I/C, by pulling out the boost controller. Before I originally installed the boost controller, stock boost was at 7psi on the nose, with the I/C and no boost controller, it's at 5.5, so 1.5psi pressure drop.

 

This has me wondering, should I switch over the boost controller so that it gets it's signal from the intake manifold instead and sees true boost at the manifold? If I were going to do that, I'd need to tee it in with another vacum line, as I don't have any open ports. I can either tee it in with the FPR, or I can tee it in with the BOV. Which would be better?

 

One part of me doesn't want to fix this problem. This boost curve seems perfectly suited to my fuel curve when I tested on the dyno. On the dyno, before the I/C, at 10psi, the motor would be at 12:1 when boost hit at 2400rpm, then would slowly richen to an A/F ratio of 10:1 by 3500rpm, then slowly start leaning out back to about 12.5:1 by 4400rpm, flat from there to 5000rpm, then start leaning out, up to 13:1 by 5500rpm, which is where I have my redline/shift point set. So it seems to work out perfectly... the boost is higher at those points where the fuel curve is richer, but then boost goes down right at the same time fuel leans out. I"m still tuning the boost to try to get 8psi as my target at 5000rpm. I know there's no way to know w/o dynoing, if all this is safe, but I figured if I could safely have gotten away with 10psi before, 8psi after the intercooler should be safe... and at 10:1 AFR, I would think the 10psi 'spiking' in the midrange should be safe as well with the I/C

 

It's so weird, because I was actually looking at electronic boost controllers that could create a boost curve like this, but now that it's happening, it just seems like a problem to me that needs to be solved.

 

So, what do you guys think?? Why would the I/C be causing this weird 'spiking'/boost curve? Why the horrible lag only in first gear? Should I switch the boost controllers signal from the compressor housing to the intake manifold? Which line to tee it in with?

[ZR8ED]

Hey I have noticed silmilar things since my i/c install 2 years ago.

 

as of this writing, I am getting 10psi in first 13 or so in second, and 14 psi in 4th and 5th.

 

I am using a turbosmart manual boost controller. I had the same issues with a home made boost controller, except a bit more extreme.

 

I ran 18 psi in 1, 2, 3 gear, and I had to feather the throttle in 4 and 5th gear to keep it from seeing 20 psi plus (I hit 20 once or twice, thats how I know, and why I'm on a new motor.hehe)

 

Not sure the reasoning.

 

I did end up with more turbo lag, but I expected that.. 1st gear more than 2, and 2nd more than 3rd etc...

 

In first gear, I hit full boost in the 4000+ range, and once it hits, I have to shift right away..

 

in 5th, my boost comes on slower and at a lower rpm.. slower ie 2500rpm...but takes longer because of the low engine speed.. say at 65mph...

 

Sorry I don't have an answer for you, but I can tell you that it doesn't appear to be uncommon.

[Tony D]

Question:

Where are you taking your boost gauge signal from?

 

I have my wastegate signal taken from a port I tapped in the intake manifold. I used an old turbo fitting, and a hole for an M6 bolt that was there no more, greased up a drill, sunk a hole, greased up a tap, and tapped it.

 

So it takes pressure reading from the intake plenum.

 

But I'm curious as to where you are reading boost pressure from on you gauge.

[Guest bastaad525]

TonyD - my boost gauge reads from the intake manifold, a hole tapped right next to where the brake booster hooks up. My boost controller gets it's signal from the turbo compressor housing.

 

 

Would it be okay for me to tee off the line that currently goes to the BOV and run another line to the boost controller/wastegate from there? I really, really would prefer not to have to remove the intake manifold to tap a new hole.

 

 

ZR8ED - yep exactly the same symptoms I'm getting now. You didn't mention if boost was falling off as revs go up though? Boost will drop off by 2 or 3 psi as revs go up to about 5500rpm. Are you getting signal off of the compressor housing for the boost controller as well? I have a feeling that switching over to getting signal from the intake manifold will solve the problem. Also keep in mind, the longer your hoses going to the turbo controller and back to the wastegate are, the more spiking you'll get. My hoses are each only a few inches long.

[Tony D]

A "T" in the line should work fine, be quick to install and easily answer your questions.

Do it and see what you get.

[Guest bastaad525]

*smacks forhead*

 

Was at auto zone today picking up some bolts I needed... totally forgot the vacuum tee along with some other items I needed as well.

 

 

Okay I'll pick up a tee sooner or later and tee the line to run to the BOV and the boost controller.

 

 

I gotta admit... part of me really wants to leave it the way it is. Maybe my logic is flawed here, but it seems to my advantage that it wants to run higher boost at lower rpms, where the fuel curve is much richer, and then the boost drops off to about 8psi as the fuel curve leans out. I had always wanted to run a boost curve like that since the first time I dynoed and saw what the fuel ratio was doing.... again, hoping my logic isn't flawed here, but I like the extra safety of lower boost past 4000rpm. But I will end up trying the tee sooner or later just to see if that does make any difference.

 

 

I'm also going to TRY to get to the dyno by this wednesday to see for sure if it's okay and adjust accordingly.

[stony]

An electronic booste controler will solve your problems. you will see less lag and more power down low. I to used a manual controller until i bought my profec B. I gained 80 HP in spots just using this booste controller. a manual booste controller just uses different size orifices to limit booste to the Waste gate act. where an electronic booste controller keeps teh wastegate shut until your preselected booste level is met then bam it opens and shuts to maintain it. If you have never used one you will not believe the difference. I didnt think it could make a difference but was drastically mistaken.

[cygnusx1]

Actually, there are two types of mechanical boost controllers that I know of. One type bleeds signal according to a predetermined "leak", the other type, what I use, is a ball/spring type(grainger). The ball spring type will prevent the wastegate from getting ANY signal to open until the set boost level is achieved. This type keeps the wastegate totally shut until you reach your full set boost. Either changing the spring or compressing the spring with a spacer or turning a screw onto the spring will change the peak boost setting. They can stick open or shut so always monitor your gauge. As far as boost going haywire after installing the I/C, mine did too but it was because the ball/spring jammed open allowing only stock boost. Once I fixed the jam, I had to raise the boost just a bit and all has been fine ever since.

 

Bast, just for old time sake, clean your connectors.... oh and experiment with your BOV. Eliminate it and see if the boost ghost goes away.

 

EDIT: I am not so sure taking boost signal for the wastegate actuator from the intake manifold is a good idea. I don't know why but just a hunch.

[Guest bastaad525]

Yep using a grainger valve here as well. It definately cuts lag down a LOT, even over running no boost controller at all. I did want to switch to the profec B, for the same reason I'm kinda liking the weird boost pattern I'm experiencing now. Basically... every 280zxt motor I've seen dynoed on a stock EFI has shown the same A/F ratio pattern. They all go super rich in the midrange, and then lean out towards the top. I wanted a profec to take advantage of this, by using the boost to 'adjust' my A/F ratio. I was going to try to program in a boost curve that would flatten the A/F ratio to 12:1 all the way up, taking full advantage of the rich midrange, but still leaving the lean top end safe. Now my grainger seems to be doing just about that same thing. I do believe mine was sticking open as well, though I find it very odd that it happened right after installing the I/C. I could only hit stock boost, even after tightening and tightening it, finally I removed and cleaned it, reinstalled it and boost was at 15-18psi . Since then I've had no problems.

 

 

Tony D - Last night right before leaving for work I spotted a vacuum tee (actually it's more like a vacuum F) laying on a table by my door, so I figured what the heck and took a minute before going to work to move things around a bit. I ended up teeing the boost controller to the same port as the FPR is on, the BOV's port is way to big diameter. I plugged the hoses off the compressor body. As suspected, the varying boost went away, it was acting just like it did before the I/C. A little 1 or 2psi spike, very brief, then settle on the set PSI and stay there all the way to 5500rpm. Odd things... the car seemed more laggy like this, really weird, I was expecting the exact opposite to happen. I figured with it hooked up to the intake manifold, the controller wouldn't open until my target boost was reached AT THE MANIFOLD, as opposed to reading boost at the turbo, which obviously should peak much faster, opening the wastegate sooner. Doesn't make sense to be more laggy that way, maybe I"m imagining it?It also didn't feel as punchy... like it was straining a little or something. So I put it back the way it was. But at least now I know, and eventually when I have more fuel and start running a higher amount of boost, I wont want that prolonged 'spike' anymore as it will probably be TOO high at that point, so will go back to running it off the intake manifold.

 

 

So, the question now is, can anyone explain WHY with the controller getting signal from the turbo, why is it behaving the way it is, i.e.: hitting and holding a higher boost level and then slowly falling off approximately 1psi for every 1000rpm?

 

Are there any advantages or disadvantages that you should be able to expect from getting the controllers signal from the manifold as opposed to the turbo? I expected less lag and more of a spike hooking up to the manifold and seemed to get neither. Any other reason I should run it one way or the other?

[Guest bastaad525]

I've also noticed that my exhaust seems to stink a lot more after driving it hard, than before the I/C install...

 

Oddly, it smells like it's now running super rich....

[Guest Cronic]

I've been using a profec B for about 4 years now, Great product, but it wont go over 20psi anymore, and it tends to spike a lot more then it used to. So I think it's going the way of the dodo bird. Time for a Spec II

[Tony D]

Welcome to the realm of "The Turbo Group Fueler"

It was a device that used the conecpt that if you can supply fuel for 10psi at 6000 rpm, then your system can supply enough fuel for 20psi at 3000 rpms...

I could not get one of the unit,s despite knowing some of the development guys from being stationed near them on Okinawa in the 80's.

Was an interesting little device, and really gave (as you put it) really punchy low-end response.

[Guest bastaad525]

Heh...

 

 

well, I did get to the dyno yesterday... really weird stuff happening there as well. Will try to get the sheet scanned and posted later.

 

The short version of the good news, is that torque was up almost 40lbft, whereas hp only crept up about 10. The bad news was my fuel curve... well... was making no sense at all.

[Guest 240Zdragon72]

Bastaad525, your I/C is a Trust one. Isent that the same as GReaddy in the states? What are the dementions, and if I'm not being rude, how much was it?

Thanks

[Guest bastaad525]

dimensions... hmm I had them posted somewhere, I forget now... I think it was like 23" long, about 9" high, and 3" thick? yeah I have been told by several people that Trust and Greddy are the same. And mine was free it was in a pile of police evidence at my job, which was later to be thrown away, and I was able to save the I/C thanks to a friend of mine noticing it and knowing what it was. I think if you were to buy one it'd go for $300-500?