Two Level Boost

[Nicely]

If it was boost cut, why does boost surge up to 1.3+ bar in 6th when it passes through the hesitation if I don't back off?

Having run and tuned two SR20DET engines for three years, I'm fully aware of what boost/fuel cut feels like, having peeled my head off the windscreen many times after hitting it. It won't hit cut until somewhere around 1.3 bar in the current sub 10 degree UK climate and with the existing fuel and air ratio setup. I have an Emanage fitted, so could raise the cut limit if I wanted, however, I see it as a warning and heed it.

The hesitation I'm detecting is just that. You can feel it during boost and the boost continues after it.

All hoses clamps have been checked. Wastegate opens and shuts fine. Controller ruled out. Actuator ruled out. The only thing which hasn't been checked, as far as I know, is the cooler itself. Think I'm going to have to pressure test...

 

[Purpleline]

understood but your styptom just like many other GTT here...not all of them have this problem...some are ok but some are not ..chipped ECU or wise down gain fix the problem ...

 

[Brad]

Thats strange the Blitz manual saying a gain of 20 too, tuning place and some dyno time definately show 5 is the right ball-park figure to be at with the stock actuator and turbo.

Brad.

 

[yewei]

hey i have a problem with my boost setting? my fren is makin more hp with lower % of boost than i am? can u people share with me ur boost setting? my mods r pretty simple, apexi air intake, rsm, custom made exhaust system of 2.5" down pipe, 3" silencer then its all the way 3" till the 3" jun muffler. its kinda loud too? too free flow? help?

 

[KSW]

Hi nicely, think im having the same problem as you here, did you ever get to the bottom of it?

I just put a boost gauge in my s15 and its showing boost holding steady at 1 bar (which it is set to) up to around 4000 rpm under floored acceleration in low gears and then shooting over up to around 1.3 at higher revs.

I have a stock turbo with intercooler, fower fc and the apexi actuator boost kit (no ebc)
anyway ill go thru the car on the weekend and search for leaks in the piping. im wondering if a sdc idIII would help the situation.

cheers

 

[Nicely]

No, I haven't

I've got a replacement T28BB with only 3k miles on it to change over (when I'm motivated). My current turbo has got noticably more play than the newly new one. I'm hoping this is the reason. Run out of ideas as to what else it could be.

 

[KSW]

ok thanks anyway. i can imagine how frustrating this would be for you having this problem going on for a while. my understanding of turbos is pretty limited, im wondering if you think a boost leak in say the intercooler piping could cause a boost spike like this or do you think it would work the other way around and the car would struggle to produce enough boost?
the only thing i can think of at the moment is maybe its my BOV leaking cause i havnt had it that long and its a pretty cheap plumback, or maybe one of my hose clamps is sealing the ic piping well enough up to a certain pressuse but leaking at extremely high pressures.
cheers

 

[Nicely]

It depends on the size of the leak. If its a big leak, you'll get no boost. If its a small leak, it will leak up to a certain level, then the boost would be enough to overcome the leak and spool the turbo. Whether or not it would be to the degree that we are getting, I don't know. My investigations and instinct tell me its not a boost leak... However, I am wrong on occaisions...

 

[Nicely]

I found a very interesting article on Autospeed.

http://autospeed.drive.com.au/cms/A_1836/article.html?popularArticle

It details mid-range boost spiking caused by better flow. They explain that the in-built ECU boost control on many car is quite primitive and cannot work quick enough to cope with the very quick boost increases caused by better flow. This results in the turbo spooling dramatically before it can be brought under control (spiking). They recommend fitting a boost relief valve in a bypass circuit around the boost solenoid, and found it had very good results.

Now that is for the factory solenoid, not a boost controller solenoid (which should be able to manage this spiking). I'm thinking that maybe it can't? Might be worth trying what it suggests...

 

[Topper]

I think it would be worth a shot :thumbs:

 

[KSW]

Thanks Nicely. that is interesting. ill end up taking my car to a good tuner over the next week or two so ill see what he can find.

 

[KSW]

Got my car back from the tuner today + problem solved he thinks it was probably just an aftermarket manifold i put on making it boost quicker. he adjusted it on the dyno and it now only spikes to 1.1 when set at 1 bar(with no ebc). it wasnt detonating when going to 1.3-1.4 anyway so its all good.
have you changed anything since you last tuned yours Nicely?

 

[Nicely]

The thing is, that this is something the boost controller should be containing.

I've narrowed it down to the same issue you mention (as I said on ns.com). I've got a tubular mani, dump pipe (elbow), 3 inch front pipe, decat, and 3 inch system. The spool up causing the spiking is happening so quick that the controller can't react fast enough. This is why I want to try the relief valve. If this works as mentioned in Autospeed, it should stop the spiking altogether.

 

[Yakozan]

Any news on this?

I have encountered a problem which seems to be the same.

I run with the boost of the stock actuator. The Solenoid has been removed.
I get steady boost of 4.5Bar when going full throttle at low revs.
When going high-rev pedal to the metal, I get 0.82Bar at the most where my boost controller warning goes in and beeps.

I've got the dual solenoid Blitz Spec-R in off mode at the time as I havn't got time to set it up yet.

 

[Nicely]

I get no problem at that level of boost. Its only around 1.05 bar that it goes nuts.

To get to the bottom of this once and for all, I bought a specific flow control valve (like a precise manual boost controller which allows NO spiking). I ran it in parallel with the SBC iD3. The purpose of this was to allow the actuator to get just enough warning of the boost pressure to keep it under control and consistent (I suspected that the turbo was spooling so quickly, due to improved flow, that the controller couldn't react quick enough).

Unfortunately, this made no difference I have one final test to perform: running solely from the control valve, with the controller off but reading boost. I'm not optimistic....

Its all pointing firmly at it being a turbo issue, probably a bit tired. Not a huge problem, as I have a 3.5k mile BB turbo sat under my voluminous desk Just have to muster the motivation to remove the tubular manifold, as I know its going to be a bastard job due to the clearance...

BTW, if anyone wants a very cheap, rock solid manual boost controller, I have a spare. I got two... These are better (and cheaper) than the Apex 'Bren Devices'.

 

[Yakozan]

OK. I'l see how the boost react to the Boost controller.
But I find it strange that the car boost that high when I have the blitz unit in Off mode and the solenoid valve removed.

Could it be the stock BOV acting as a boost valve

 

[Nicely]

Well, that is essentially what happen on mine, just at higher boost. And it doesn't do it until peak power in 5th/6th.

It scares the shite out of the controller when its in self-learn mode. It allows the spike twice, then won't boost over 1 bar...

And that's with it set to 1.1 bar...

 

[Nicely]

Remember this one? :wack:

Finally fitted the spare turbo at the weekend. Right bastard job.

One front pipe nut wouldn't come undone (no clearance for a socket between the nut and pipe and no clearance to use a spanner). Had to undo the elbow/dump pipe.

Discovered why I was losing oil. Oil feed line had cracked (only one I hadn't yet replaced with a braided hose). Let this be a warning to anyone considering saving a little bit of money by not replacing the hard pipes. I've had a water feed AND oil feed crack now. Plus the oil feed cracked on my first S15.

The reason it cracked was because a couple of mani nuts had worked loose and the mani was vibrating and starting to leak. One of the turbo/mani nut had come off completely too This was down to the guy who replaced fitted the mani and change the gaskets last year failing to lock the nuts with the tabs on the plate lock :rant: So, the turbo gasket was also starting to leak and the turbo vibrate. All this movement caused the pipe to crack. However, everything else was casuing the weird noises I've been getting.

Oh, and the turbo central spindle needed rotating from the S13 position to the S14/15 position...AND the air intake bolt cores had to be transferred

All OK now though Still testing the boost. The spool up is more controlled. I've got the controller up higher than I ever could before. However, it seems reluctant to boost over 1 bar at the mo.

What settings do people have their Profecs or SBCs set to boost and gain-wise?

 

[kieran]

Oh, and the turbo central spindle needed rotating from the S13 position to the S14/15 position...AND the air intake bolt cores had to be transferred

? i dont get it nicely? what is adjustable? if you been getting leaking from the fanimold i would think this would create boost problems, sounds like you may have solved ya issues though nice one :thumbs:

iirc you have a after market manifold? you had any problems? i had one and it was dead within 2 months there wasnt a pipe that hadnt cracked? and it had the support bracket......also cracked

But i dont appear to have a down pipe to gear box brace like the s14? does the s15 have this?[/quote]

 

[Nicely]

None of those problems would have caused the spiking I had been experiencing. There was no problem with the manifold nor any of the gaskets. The spiking was down to play in the turbo, I expect. There was certainly noticeably more play in the old turbo than the new one. This **hopefully** was causing the uncontrollable spooling.

When you buy a new turbo, it will just been put together in the factory and that's it. The water and oil inlets/outlets could be pointing in any direction in relation to the turbo housing mounting points. Eg. when the turbo is on the block, the oil return could be too close to the block. What needs to be done is all the bolts on the INSIDE edges of both the hot and cold sides of the turbo (so, facing the middle of the turbo) have to be undone and both housings turned equally until it matches the existing turbo alignment. When this is done, the bolts are replaced. Its something you would never encounter unless you replaced the turbo.