RPM drops fast and low during gear shift
 

hi all,

i am currently driving a JDM Evo7 with the following mods:
1) SARD Fuel Regulator
2) Walbro 255lph fuel pump
3) Apexi Air Filter
4) HKS SSQV BOV (2nd edition without valve spring to control soft/hard)
5) Custom 3" downpipe and de-cat
6) HKS Silent Hi-Power cat-back exhaust system
7) Apexi RSM and AVCR
8) Exedy Twin-Plate
9) HKS Ground Wires
10) Blitz R-Fit (air fuel control)

previously i was experiencing issue with engine getting cut-off when switching gears during idle (legs on clutch) then after additional upgrades i no longer have that problem; but then recently i have been experiencing almost the same problem except the rpm drops really fast and low (sometimes below 700) but engine doesn't cut off.

any idea what could be the problem? i was told it could be caused by my SQV which is a newer edition without valve spring to control hard/soft but i would like to find out if i am looking at the wrong place.

Are you running it VTA?

VTA + MAF = problems. The SSQV is one of the only ones that will work with any reliability at all, but it still does some geeky stuff like that. I have the same one.

using VTA, don't think they have recirc kit for SSQV.

u guys think its my SQV too?

i'm sorry but whats MAF?

MAF is the air sensor that your airfilter is connected to.

my MAF is still there and just got it cleaned yesterday

did the revs start acting funny before or after the MAF was cleaned??

and did the cleaning help???

Yes, they have a recirc kit, and this problem is the very reason why :)

before; cleaning didn't help much.

haven't seen any of them in my country; u believe its because of VTA which is giving me this prob? if VTA is the prob then i would have to replace it with some other BOV which recirc back to air-intake like Greddy TypeRS?

Well we can never say %100...but It is almost certainly the VTA configuration causing the issue. The valve is a good valve overall. I would suggest trying to find the Recirc kit from a vendor that will ship to you there.

Of course, if you don't want that hassle then get a recirc valve like the Greddy Type S (used), RS, APS dual vent (a very nice valve that is VTA and recirc), or even a JDM Evo MR factory valve. Try a recirc setup and see if that clears it up :cool:

thanks for the tip.

i removed my SQV and fitted back the original BOV which came with the car and it fixed the problem; so i guess its clear that VTA is the main cause of it.

i actually like VTA sound (most of us would) so i am wondering if fitting a VTA BOV which has 'spring stiffness adjustment screw' (soft/hard) would resolve this issue since my SQV doesn't have such option? The Greddy Type RS has 2 models, recirc or VTA; the recirc model looks exactly the same ori BOV except its made of metal.

I had the Greddy RS, but even in Full Recirc, I had a lot of issues with it, mainly with it fluttering. I returned it and kept my stock one.

when you say fluttering, do you mean engine feels like it was going to stall (low rpm) but then up and running again?

If you want the best of both VTA and recirc, then I have read that the APS Twin Vent is the best valve on the market. It will recirc and VTA simultaneously...I would research the APS if it were me...