JohnA Posted July 18, 2005 Share Posted July 18, 2005 I need to experiment briefly with boost pressures over 1 bar, and I found a new, cheap HKS FCD on eBay. I see on mkiv.com that they are labelled as "not recommended", anybody know exactly why? Do they remove the boost cut completely, simply raise it a bit, or do they create weird problems with fuelling/ignition/what-have-you? cheers guys Link to comment Share on other sites More sharing options...
GeordieSteve Posted July 18, 2005 Share Posted July 18, 2005 Do they remove the boost cut completely... Think that's why they're not recommended. TRL FCD's just raise the boost cut Link to comment Share on other sites More sharing options...
Nic Posted July 18, 2005 Share Posted July 18, 2005 I need to experiment briefly with boost pressures over 1 bar, and I found a new, cheap HKS FCD on eBay. I see on mkiv.com that they are labelled as "not recommended", anybody know exactly why? Do they remove the boost cut completely, simply raise it a bit, or do they create weird problems with fuelling/ignition/what-have-you? cheers guys I had one on mine with absolutely no problems. It removes cut completely. Link to comment Share on other sites More sharing options...
JohnA Posted July 18, 2005 Author Share Posted July 18, 2005 Thanks guys. Nic, yours is JSpec though, isn't it? I wonder if the UK/US spec behaves differently. Link to comment Share on other sites More sharing options...
JohnA Posted July 18, 2005 Author Share Posted July 18, 2005 Shoite , I've just found a full explanation on .com, by LanceW (under GReddy notes, go figure...) ...The HKS unit reduces the signal coming from the turbo pressure sensor at a fixed percentage, which means that all the data coming from this sensor is corrupt... The EBV won't be too happy, among other users of the boost pressure signal. Makes you think twice about the repercussions of such (simple at first glance) mods, brrrr..... Link to comment Share on other sites More sharing options...
Nic Posted July 18, 2005 Share Posted July 18, 2005 Thanks guys. Nic, yours is JSpec though, isn't it? I wonder if the UK/US spec behaves differently. Yes J-spec. It is listed on the HKS US site so should be compatible see HERE Link to comment Share on other sites More sharing options...
Bobbeh Posted July 18, 2005 Share Posted July 18, 2005 Gonna tell us what those reprocussions are then? Link to comment Share on other sites More sharing options...
JohnA Posted July 18, 2005 Author Share Posted July 18, 2005 look here mate Link to comment Share on other sites More sharing options...
Bobbeh Posted July 18, 2005 Share Posted July 18, 2005 Im a believer of spreading the knowledge ie next time someone looks up the issue they dont have to go clicking all over the place for it. Ta for the link tho Link to comment Share on other sites More sharing options...
JohnA Posted July 18, 2005 Author Share Posted July 18, 2005 I ain't gonna copy/paste something longer than half a screenshot. MKIV.COM ain't gonna disappear overnight either. I know what you mean though, lots of intersting stuff disappears from the net, server failures, free webspaces withdrawn, paid services stopped etc...I've had this problem with links on my website, so many drowned without a trace through the last couple of years. Now I make an effort to keep local copies as well, so when (not IF) they go missing the info is still available. It takes up a LOT of webspace though, and that costs money. Link to comment Share on other sites More sharing options...
JohnA Posted July 18, 2005 Author Share Posted July 18, 2005 The way they describe the operation of the FCD in mkiv.com is not dissimilar to that of fitting a bleed valve on the MAP sensor's hose. Except it is not a pneumatic method, it is electronic. That's not satisfactory at all What I'd like is something that leaves the signal intact unti 1bar, then simply caps the output to 4.3V or whatever the value is for 0.98bar. Link to comment Share on other sites More sharing options...
slick Posted July 18, 2005 Share Posted July 18, 2005 Greddy BCC then or Thor's version which has a great rep, in Thor's case the 'cap' can be adjusted further up the scale to allow some form of protection. Link to comment Share on other sites More sharing options...
JohnA Posted July 18, 2005 Author Share Posted July 18, 2005 Yes but do they leave the signal intact until that point? Link to comment Share on other sites More sharing options...
Matt Harwood Posted July 18, 2005 Share Posted July 18, 2005 Yes but do they leave the signal intact until that point? Thor's ones do. They simply cap at a desired voltage. John, as far as I can make out, you should be OK with the HKS one as I'm fairly sure the MAP sensor is ONLY used for fuel cut on a UK spec. - Although I'd be interested, and happy to be proved wrong. It's undoubtably the MAF that controls all the fuelling on a UK car.... Link to comment Share on other sites More sharing options...
slick Posted July 18, 2005 Share Posted July 18, 2005 Yes but do they leave the signal intact until that point? Well for the Greddy: Factory Settings: Unit under test provides 2 millivolts gain to the signal, which equates to 0.016 psi, across all test voltages. This is insignificant. The unit clamped @ 3.94 vdc which equates to 0.71 kg/cm2 or 10.12 psi gauge according to measurements taken on my OEM turbo pressure sensor. I reset the clamp voltage to 4.31 vdc to simulate 1.95 kg/cm2 absolute pressure, since the manual states that fuel cut occurs at 2.00 kg/cm2 absolute. This clamp setting equates to 0.92 kg/cm2 gauge or 13.04 psig. I think we can safely forget about 2mv gain. Thor's version according to the site info here an FCD that leaves the boost signal alone until it approaches the cutoff level, and then kicks in, holding the signal below the critical level. So uses a similar 'clamp' method like the greddy that doesn't interfere untill the preset point but with the addition of overboost protection. This is why I mentioned those 2 in reply to your question. Link to comment Share on other sites More sharing options...
Alex Posted July 18, 2005 Share Posted July 18, 2005 Thor's ones do. They simply cap at a desired voltage. John, as far as I can make out, you should be OK with the HKS one as I'm fairly sure the MAP sensor is ONLY used for fuel cut on a UK spec. - Although I'd be interested, and happy to be proved wrong. It's undoubtably the MAF that controls all the fuelling on a UK car.... My MAP's disconnected so it' can't hurt that much Link to comment Share on other sites More sharing options...
JohnA Posted July 18, 2005 Author Share Posted July 18, 2005 Thor's ones do. They simply cap at a desired voltage. So if I were to go for one, it would have to be one of those then. ..the MAP sensor is ONLY used for fuel cut on a UK spec. How about pulsing the EBV VSV? that's based on boost isn't it? (sod the wastegate VSV, that I control pneumatically) It's undoubtably the MAF that controls all the fuelling on a UK car.... As I'm experimenting in general, I'm not sure how long the MAF will be sitting there strangulating the intake. However MKIV.COM is geared around US-spec, which in this respect is similar to UKSpec, is it not? Link to comment Share on other sites More sharing options...
carl0s Posted July 18, 2005 Share Posted July 18, 2005 However MKIV.COM is geared around US-spec, which in this respect is similar to UKSpec, is it not? yep. Link to comment Share on other sites More sharing options...
Guest ChrisB__1 Posted July 23, 2005 Share Posted July 23, 2005 I have evaluated both over a period of months - HKS and Thor VFCC. Firstly, you run rich at 1 bar. The HKS scales the output ("corrupting" it's written, but it's a scaling in reality) which means the ECU sees the output increasing all the time up until your boost maxes out. Note that the boost cut IS retained - depending on your setting, 9 for Supra's. This leans out the mixture slightly, only when on boost. To put this in perspective, the Thor VFCC leans out the mixture above 1bar by holding/capping at 4.3v (or whatever) when in reality the boost is higher. Visually, the car puts out black smoke puffs when using VFCC and no smoke with HKS (fuelling closer to ideal). On dyno, the fuelling was fine even at 1.1 bar with setting 6 on the HKS (lower setting equals leaner, recommended is setting 9 out of 12). VFCC is *just* suitable for 1JZ, as has a different map sensor to 2jz - 1jz is only to 1bar, hence setting F or E is needed. HKS is *just* suitable also for 1JZ - using the recommended setting from 2JZ. The problem here is that the 2jz map sensor outputs a lower voltage (greater range of map sensor) when boost just about starts coming on. So the leaning out is WORSE with 1jz, but ONLY low-down rev-range when spooling, around 3k on mine. I see a lean spot on my A/F ratios' around here and then all hell breaks loose. In summary, I sold my VFCC and kept the HKS. If you're going above 1.2 bar, I don't recommend use of FCD alone in either case. However, I'd add that neither is really suitable for the 1JZ. It should be remembered that an FCD is really acting as a fuel controller, and it's possible to build/buy a cheap (but very effective) fuel controller for a similar price (read Link to comment Share on other sites More sharing options...
JohnA Posted July 23, 2005 Author Share Posted July 23, 2005 I went for the VFCC in the end, despite the price being double (the other one was new from eBay) I *did* consider this HKS's gradual 'leaning off' as a potential boon, because boy does my ECU run rich from 10psi upwards. In my case I am experimenting with higher air masses over 12 psi, so when my boost gauge shows 17psi it will really be more air molecules compared to stock twins pushing hot air. Hence the need for more fuel to pair them up. ...so I decided to play it safe and go for the one that leans out the mixture as little as possible. Maybe over 1 bar they both lean it out the same, can't we just tell from the 'final' signal they allow for the MAP? Link to comment Share on other sites More sharing options...
Recommended Posts
Please sign in to comment
You will be able to leave a comment after signing in
Sign In Now