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Discussion Starter #1
Hi guys!

I've recently boosted my 2L G4GC Tib using an Evo 4 TD05 and have a question or two.

So I've been doing a lot of research here as wow there is sooo much info but there is just one thing that I can't seem to find an answer to and that is the EVAP purge system and boost! Is the purge valve able to handle boost?

And the other is I have installed the Sonata 290/310cc injectors and dialed the piggyback (Ecumaster DET3) in by originally putting -34 across the closed loop part of the map. Still tuning this part...

I found that since the injector install, the car is running great and AFR's are looking decent but one problem that I seem to have now is a bit of rev hang when changing gear at low RPM ~2000-3500. Now is this a symptom of too much fuel or too little? Or maybe a vacuum leak?

Also a side note, this rev hang doesn't happen while the car is warming up in the morning...

Any ideas?

Craig
 

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The evap solenoid will be fine as it only opens under vacuum. Are you hitting positive pressure at that low of rpm? It could that the IAC is fighting against boost. Also is the car MAF or map?
 

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Discussion Starter #3
Ah good to know about the EVAP valve, couldn't find any posts about it so thought that was the case!

I seem to be hitting boost at about 2800-3000 rpm, I did install a thin plate with 2x 1/4" holes (from memory!) on the IAC a couple years ago to stop the standard rev hang which did the trick perfectly but now since the injector install it seems to be back...

Oh I also did slacken the accel cable and clean the IAC recently as I thought it might be sticking but made no difference at all.

The car is MAF, had it just before the TB (blow though) for some time with the crank breather inlet to atmosphere with a little filter and suspected that that was the unmetered air coming in causing this but have since changed to a recirc BOV with a catch can system taking clean air from after the MAF and moved the MAF pre turbo but changed absolutely nothing.
 

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I had a problem with rev hanging and a strange idle with my car, the culprit turned out to be a vacuum leak where the brake booster vacuum hose attaches to the rear of the upper intake manifold. Apparently somebody before me over tightened the hose clamp and smashed the metal fitting kinda flat shaped.

You can find a vacuum leak with a propane torch, turn on the gas and obviously don't ignite it and run the tip around all your vacuum lines, if you have a leak it will make your engine increase RPM's when you find it. Its probably not very safe, but it works.
 

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Discussion Starter #5
Yeah thats what I was thinking but I did spray a little industrial IPA around areas I thought might cause a leak a while back and nothing. Only thing left could have been the EVAP system but seems it cant be that.

I did check the brake booster pipe as I have tapped into that for my vacuum manifold but its all secure.

I reckon I need to try some propane! :smile2:
 

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Yeah thats what I was thinking but I did spray a little industrial IPA around areas I thought might cause a leak a while back and nothing. Only thing left could have been the EVAP system but seems it cant be that.

I did check the brake booster pipe as I have tapped into that for my vacuum manifold but its all secure.

I reckon I need to try some propane! :smile2:
I would rather suggest brake or carb cleaner, they are a fuel that is a bit more tame than propane.
 

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I use propane because its a gas and its pretty easy to run the nozzle around the lines rather than aiming and spraying fluid everywhere.
 

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Discussion Starter #10
I think I'll still go with the brake/carb cleaner as its easier to come by here in the UK.

I've put a brass T in the brake booster pipe before the check valve and all the connections have miniature T-bolt style clamps so shouldn't be leaking. I was thinking of drilling and tapping the intake manifold for a dedicated barb for the vacuum manifold - might do this sooner!

I'll have a look around that area again just in case I've missed something.

Thanks for all the suggestions guys!
 

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Discussion Starter #12
Before meaning in between the check valve and booster? Or in between the check valve and manifold?
I have the T in between the check valve and manifold.

I have been thinking...dangerous I know! :smile2: so the rev hang started almost immediately after the 290cc injector install so it must be fueling issue surely!

The plan is to try the suggestions here and search for a vacuum leak and if nothing is found then check the throttle body to make sure its closing 100% and then make some changes with off throttle fueling and see if I can clear it up.

If all else fails then I'll live with it until summer as its pretty much brought the stock rev hang back and the cars running fine in all other areas.

Oh one last thing before I forget, it def seems to do it more around 3000-3500rpm when I lift off the throttle as boost is climbing - don't know if that means anything haha
 

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Where does your recirc line go? It should go in between maf and turbo inlet. How is your catch can plumbed? You should be using one in between the PCV valve and intake manifold and it should be one that can be pressurized. You can also have one on the breather line and that one can go to the same place as the recirc line. I don't recommend that though as you can pressurize the cylinder head with the air from the bov. I also recommend a PCV valve from an evo 9 since it's designed to hold boost pressure.
 

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Discussion Starter #14
Yeah the recirc is between maf and turbo inlet.

One of the things I made sure was to get the Evo PCV part no. MD152772 - hopefully thats the right one, funny enough the Hyundai PCV looked identical!

My catch can setup is a bit weird but I have found it works well and takes fresh air after the MAF, the cam cover has a straight barb so no restriction.

The idea of this sealed catch can is to pull vacuum from the intake until the PCV closes then the turbo intake starts to pull vacuum.

Don't forget I had the rev hang issue before I installed the catch can with this design, it was also there with the blow through MAF hence why I thought changing to this setup might solve it as all air is now metered.
 

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The turbo will not generate enough vacuum to open the PCV, especially not the EVO one as it has a stiffer spring in side. As long as your PCV catch tank is good then you only need the lines from the cam cover and intake manifold. The line to the turbo inlet does nothing. Also remember your boosting a motor than never came that way. At best the MAF sensor will read 2-3psi before pegging its voltage range. What are you clamping the MAF voltage to in the DET3?

Also remember that unless your forcing open loop under boost or modifying the O2 signal under boost the OEM ECU will attempt to trim fuel out to reach its closed loop AFR targets.

Another thing to consider is how long the vac hose is to the DET3. I recommend no longer than 3ft otherwise you'll get slow response time from the DET3's internal MAP sensor. This could cause issues like your seeing. Are you intercepting or just tapping the crank sensor?
 

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Discussion Starter #16
Sorry the diagram isn't as clear as it should be, the two one way valves coming from/to the intake piping are actually brake servo type check valves that I bought on a whim and found they open VERY easily but close very securely the other way around. The only valve that I feel isn't really required is the one going towards the cam cover. The EVO PCV is only between the intake manifold and catch can.

One of the catch can lines is right at the turbo intake so as to have the best vacuum and the fresh air line to the cam cover is right after the MAF further down the intake piping so as to cause a greater pressure difference - the catch can seems to be filling up a little quicker since doing this, thats what made me think its working better now.

These are the one way valves I am using: https://www.ebay.co.uk/itm/6-8-10-12mm-Brake-Servo-Booster-No-Return-Inline-Check-Valve-Vacuum-One-Way-Hose/292626047848?ssPageName=STRK:MEBIDX:IT&_trksid=p2057872.m2749.l2649

MAF voltage is clamped at 4.7v and at WOT boost is 0.23 bar/3.3psi @ 6500rpm its about 4.5 volts but the DET3 is currently scaling down to 4.2v

Strange thing is boost is 0.42 bar/ 6psi from 2800-4700rpm and tapers down to 0.23bar @6500rpm as above - should it not be constant to redline?

The vacuum hose is 2 foot away from the DET3 and I'm intercepting the crank. I had the DET3 wired up for a good 6 months when I was still NA just to make sure all was working ok before the turbo install. During that time I did advance the timing slightly in the lower rpms as I found it increased torque nicely with 98 octane fuel here in the UK. Since the turbo I did zero out the values to put it back to standard timing.

With regards to open closed loop, I have tuned the open loop area of the map but have yet to sort out the closed loop. I have been making sure I don't sit in boost at closed loop due to the AFR being way too lean ( I change gear before then!) I only drive about 10 miles a day currently in heavy traffic so for a short time should be ok.

The plan in next week or two is to have a small relay that gives the TPS a 4.7v signal to force open loop just before I hit boost. I'll be using an output on the DET that will activate the relay just before positive pressure comes in. Then I'll tune that area.
 

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In the future lead with info like that. 😉
I'm assuming you have a 6psi wastegate? If so than your loss of pressure higher up could be due to too much back pressure or an improperly adjusted actuator arm. What size is your down pipe and exhaust? Did you port match the manifold to the head? An Evo manifolds ports don't exactly line up so they must be port matched.
 

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In the future lead with info like that. 😉
I'll try my best! :grin2:

I have a 0.3bar/4.4psi spring in a Kinugawa wastegate but have tweaked the boost up with a manual boost controller teed into the boost line to the wastegate. I did originally adjust the wastegate to hold closed a bit more according to online advice so should be fine - pin sits halfway on the eye of the wastegate from memory...

Exhaust is 2.75" downpipe to the resonator and then 2.5" right to the aftermarket backboxes (large bore)

I did port match the exhaust manifold a "little" but must admit its not perfect and could well be the cause of the boost dropping in that case. I have another EVO 8 manifold here that will be getting ported a bit better in future.
 

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If the actuator arm fits easily over the flapper arm pin the that's your problem. You should have to pull it out a bit to get it on. Otherwise it will open too easily. It needs a certain preload on the spring. Also make sure your boost source for the controller comes from the intake manifold and not the compressor housing.
 

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Yeah I had to pull on it a bit to get it over the flapper pin, will try the actuator piping to the intake manifold first before anything else - makes sense as thats after the IC where you could get pressure drops and thats the actual pressure being put on the engine.



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