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Discussion Starter · #1 ·
Ok, I am not 100% clear on this subject, but here goes... I have a HKS Super SQV, which has been on the car along time. Ever since it was fitted, it has always been responsible for stuttering when lifting off, e.g. in a gear change.

I am aware that a VTA bov is not ideal when you have an airflow meter, but as I am about to get a map sensor with my GEMS, that isn't an issue for me. What I want to know is what is the best solution for me, to get rid of the stuttering. It is ok on smooth changes, not on fast changes.

I am also aware that the HKS is a vacuum operated, and not boost operated bov, so slower than others - and not ideal for a race/track car.

1) Put the original bov back on - but without any recirculating bits (can't recirculate with my new turbo I believe)
2) Get a new bov such as the Blitz or HKS racing one.
3) Take the bov off, and bung up the hole as racing cars don't have bov's anyway.

I am tempted to go for option 3 at the moment, but am willing to hear arguments for and against! Custard - interested on your opinion particularly.
 
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Discussion Starter · #2 ·
Blade, options discussed as below...

1. I'm interested as to why you can't recirculate with your new turbo. All you are doing is taking air from after the turbo and putting it back into the feed air stream. Why does a change in turbo not allow you to do this anymore?

2. Not sure on comments for this as I haven't looked at them. ;)

3. Running without a BOV may cause shorter turbo life due to the reverse pressure pulse of air hitting the blades and spinning them in reverse. This may also mean you get a bit more lag after changing gear.

Anyway onto the main part of my reply.
If you're going for a MAP sensor then won't this solve the stuttering problem anyway? I'm not sure but isn't the stuttering caused by the air that is no longer in the intake and has been vented out so causing the ECU to overfuel. This is a problem because the MAF sensor has 'seen' the air that has been vented.
With a MAP sensor you will be working off pressure and not flow and so this won't be a problem anymore.
Then again, I might be talking ######## but someone will correct me if I'm wrong. ;)

For what it's worth, why not plumb the existing dump valve into the exhaust manifold via the secondary air system connections and then run a mild antilag that you can program with the Gems. This is the setup on the WRC cars. This will solve the problems with the stuttering gear changes and make them even quicker due to having the boost available. You know it makes sense really :D:D:D

Andy
 
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Discussion Starter · #3 ·
Andy, the recirculation comment was because I presume I will need to drill the new manifold, and as it is on the car - it is a big job.

Thinking about your MAP comments, that does sound very reasonable. There are not sas connections, different manifold, and according to Steve Simpson running anti-lag on the GEMS involves jacking the throttle wide open, which makes it not as nice to drive in the rest of the rev range. And that will definitely shorten turbo life!

Maybe I will try the GEMS and see how things are then.
 
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Discussion Starter · #4 ·
explain stuttering
i believe you have the same problem as me,which is abrupt deceleration of the motor when lifting the throttle,like fuel cut in reverse
but
i get this on part throttle,for example,on a bumpy road....change from 4th into 5th,blend out of throttle to regulate road speed,
but if i come off the throttle to much,(or maybe too quick) its like a split second dead stop before normal deceleration
(or rather ,maintaining chosen cruise speed)

this is hard to explain in words

had put this down to the fse regulator shutting quickly,
but after reading your post im not so sure.

anyway,with gems,it wont matter.....although it would be interesting to try without a bov at all
are you still going to use the secondary air system ?
what exhaust manifold are you using ?
 
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Discussion Starter · #5 ·
heres my thoughts

map sense didn't really fix, main problem i think is hks reluctant to open when running higher boost as more boost shutting than vacum opening, not for high boost apps, hence judder, jolt

custord - maybe injectors shut off as air flow stall due to backflow giving low reading on meter hence 'catch'??

blanking off the bov makes the car turn into a bucking bronko if u lift slightly from big boost say 1.7, goes into a real violent oscillation might be ok for drag racing, possibly track, undrivable on the road i didn't like it at all

standard bov v nice and it doesn't leak provided throttle is wide open (and leaking when not is actually a plus as turbo keeps up a good head of steam)

i have tried the rest (incl hks) and now use the standard one venting to air (am running 1.7 bar)

not sure how it will work with anti lag though, im sure the sas can make a nicer system than jacking the throttle open if its programmed right, still waiting for the phone call to say the software has been changed

andrew
 
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Discussion Starter · #6 ·
Tony,
A few more comments then....

Why do you have to drill any manifold to recirc the air from the dump valve. All you have to do is recirc it back into the intake pipework before the turbo therefore, if anything, all you'll have to drill is the intake pipework so that you can fit a return point.

I know that the GEMS jacks the throttle open for anti lag but using the SAS gets around this. Rather than jacking open the throttle to provide the air for anti lag, you use the SAS to provide the air straight into the exhaust manifold and you can keep the throttle as standard. This also means that you still retain a vacuum in the plenum chamber (because the throttle is closed) and so keep the servo assistance to the brakes.

The only problem I can see with putting the standard one back on and venting it to atmosphere is that it will leak open on part throttle (due to the differential pressure across the diaphragm) and so you won't have an instant part throttle response as you'll be losing some boost pressure before the BOV closes again.

Whatever you decide, let us know how you get on

Andy
 
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Discussion Starter · #7 ·
Andy,
I would have thought that the SAS couldn't provide enough air for ALS. I don't know the air flow figures for the SAS or what is required for the ALS, do you actually think the SAS can provide enough air then?

R
 
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Discussion Starter · #8 ·
Ryan,
It may not provide enough air for a full on anti lag setup but it wil provide an amount of air which combined with retarded ignition and overfuelling will combust in the exhaust manifold and keep the turbo spinning.

Looking at the WRC cars at Ralliart, this was the setup that they were using and so I would assume that it is possible to do.

Andy
 
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Discussion Starter · #9 ·
So I guess that you could also do this with an ECU that does have true ALS built in, I wonder how much over fueling you would need to do to get it to work :D

could be something for Claudius or Barry to try with the Apexi FC :D that way you could turn it on and off! :D

R
 
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Discussion Starter · #10 ·
Ryan,
In order to do it, you also need to be able to retard the ignition so that it fires when the exhaust valve is open. Therefore just having the AFC won't allow you to do it. You'd need the ITC as well.
An alternative to this is to do the anti lag old style i.e. run with an extra spark plug in the exhaust manifold linked to a switch and then overfuel and ignite the mixture using the extra spark plug.

Andy
 
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Discussion Starter · #11 ·
Original Post:
Ryan,
In order to do it, you also need to be able to retard the ignition so that it fires when the exhaust valve is open. Therefore just having the AFC won't allow you to do it. You'd need the ITC as well.

Andy
He didnt mean the current setup with the S-AFC, but the future setup with the Power FC ECU!
 
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Discussion Starter · #13 ·
You almost made out with Barry but find it sad to admit I'm right!? ;) Anybody who can read knows that i'm right
 
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Discussion Starter · #14 ·
I think the description by custard is accurate. I actually now think i have several problems after Cadwell yesterday, chatting with Barny, Custard, Clive at RC etc.

Certainly my cam timing is wrong, and mapping is all over the place, but there is something mechanically wrong too. The abrupt lift-off behaviour is the dump valve, and I will try a standard bov venting to atmosphere at Oulton on tuesday.

I also think there may be a wastegate or boost controller associated problem. Why? The stuttering and shuddering actually improves if I turn the boost controller off! In fact it drives nicely (except for the BOV related stuttering.

Could be the new external wastegate, or a vacuum leak in the boost controller plumbing. Needs looking at. Even running the car at low boost (0.7 bar) I have the problems. I get the same boost switching the controller off, but the not the hesitation problems.
 
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Discussion Starter · #16 ·
not totally familiar with this controller but maybe the gain is too high, ie the control circut is too underdamped, standard actuator is 'soft' so the response time can be set faster but if the new waste gate has a stiffer spring then what can happen is that you get oscillation ie boost rises quickly and over shoots then controller over compensates so undershoots, controller over compensates so over shoots, etc. etc

like over correcting after a slide and doing a tanks slapper, but anyway like you say could well be something else just a thought

once you have map sense i cant see any point in recirculating, will just muck up the air flow into the turbo, if you are still on af meter then off course it wont idle too well with standard vta but should be ok once rolling

throttle response will be different but it just that its more linear ie need full throttle to get full boost rather than half throttle, this might give the impression that the car is slower but its not, just more drivable

i data logged the boost rise (with it floored) with the standard one vs an adjustable with it screwed down tight and there was no difference

andrew
 
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Discussion Starter · #17 ·
evotrak, I think you are right. What I am going to do for now is simply adjust the wastegate and leave the boost fixed at 1.3 bar, which is what the car is mapped for at the moment, and take the boost controller out of the loop. It isn't doing rpm mapped boost, so I won't be losing anything I think, and I am going to put the standard bov on, venting to atmosphere, like you. Straight fit I assume, nothing fiddly? Just take the HKS off, and put this one on? I do have different piping...
 
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Discussion Starter · #18 ·


should just fit on, use a peice of hose for the control line (red in pic) with a good inside diameter - anyway remove that silly inline filter thing, might stuff things up, might stop boost getting to the standard one which you need to shut it quick
not necessarily the final answer see how u go every car is different, if it is black hose for the main pipe to bov then warm the car up and then retighten hose clip as can come loose

not sure how your boost control circut looks with the controller switched off but u may be losing spool by having nothing ie it will 'lean' on the waste gate and it will start to crack open below your target boost what you really want is nothing to the waste gate until target is reached then it should open to the waste gate but should do this gradually because if it responds too much then you will oscillate

btw still have air flow meter in my car but have removed honeycomb because it is unused

andrew
 
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Discussion Starter · #19 ·
Once you ditch the MAF stick with the HKS BOV - the standard one will leak under pressure - the HKS will close under pressure.
 
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