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Discussion Starter #1
I've had my r34 gtr at a tuning shop (in australia) for quite a while now. They are an HKS place. It is a crate motor, with 2530kai, f-con vpro and the stage 1 vcam kit and supporting mods.

It has no problem making power, and all the other issues are sorted however I had the first opportunity to test drive it today and both me and the tuner agree it is undriveable. Partial throttle is great, feels stock. All good. However give it some welly in 2nd or 3rd and it goes nuts all of a sudden, shortly after 3000rpm, and breaks traction. This is with the boost controller set to low boost @ 15psi ! not the 380kw+ available on the dyno at the high boost setting..

Boost goes straight from 1psi to everything in FAR too short an interval.. tuner says it is v-cam and is trying to tame it in the software, but I am starting to think he is in over his head. I thought the car was great with N1s, @ 280kw, smooth progressive even in 2nd gear. Now it is just .. stupid ..

vcam controller has quite a small 2d grid for load maps and cam profile, or so he says .. if you focus on the top end, there are no points for the bottom, and vice versa. I'm thinking if they can't sort it out, to just rip it out and go back to normal ? But I read vcam should rock .. I've seen the best motoring clips.. it would be a shame.

oil pressure on this motor is high, because it uses a tomei pump. Not sure but I think oil pressure drives the cam profile change? maybe that is an issue?
 

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Just to clarify, where is your problem? It could be read that when you put your foot down at anything over 3000rpm the thing goes nuts and you aren't happy with it, which is a bit contradictory to the fact that you clearly must have gone for V-Cam and GT2530s etc to get good power with plenty from down low.

I can only assume that maybe up until it goes nuts there is proportionally little grunt? Ie, its dead up until 3000rpm then it suddenly erupts into life? Is it throttle control or the range of power or what exactly you aren't happy with how it happens? Or do you actually want it to be more gutless down low?
 

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Discussion Starter #4
Sorry I wasn't clear.
It goes nuts in a bad way. There is no problem off boost, not gutless, nope ..

the problem is the boost ramp is now ridiculously steep - not usable, because the transition from no boost to all boost, perhaps encouraged by the vcam, feels (and sounds) uncontrolled and the tires will let go I don't even think the attesa system has a chance to divert power to the front. On a track it would be dangerous (and slow). On the road, isn't accessible because of the transition is literally like dumping a clutch.

I'm told a regular 2530 rb26 doesn't feel like this at all: progressive just like GT-SS or N1s, but doesn't get breathless at the top.

I thought the idea of v-cam is to flesh out the mid range a bit more.. thus make it feel more like a 2.8.. but as it stands on my car, in its current setup, it appears to just screw up the boost transition, making it really hard to select partial boost with your foot and turning the tune into an on/off switch.

Honestly if this is how vcam is supposed to feel, I don't think anyone would be impressed.. but maybe someone who has it can explain what it does & how it ramps, when done right.
 

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Discussion Starter #5
& sorry yeah the attesa was fine prior to the work. All green, all ok. No reason to think it has gone weird on me. New clutch as well, feels great. New 265 profile tires. Ohlins.

I should have spent some more seat time, try WOT in 3rd or 4th, watch the torque meter and PSI hold. etc. But tuner said, yeah it sucks doesn't it, lemme work on it some more (it has been weeks already) and try to calm down the valcon. When I got the vcam it CAME with a sheet of recommended settings for 2530s with bigger exhaust cam. I ASSumed it would be bolt-on. makes me wonder..
 

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& sorry yeah the attesa was fine prior to the work. All green, all ok. No reason to think it has gone weird on me. New clutch as well, feels great. New 265 profile tires. Ohlins.

I should have spent some more seat time, try WOT in 3rd or 4th, watch the torque meter and PSI hold. etc. But tuner said, yeah it sucks doesn't it, lemme work on it some more (it has been weeks already) and try to calm down the valcon. When I got the vcam it CAME with a sheet of recommended settings for 2530s with bigger exhaust cam. I ASSumed it would be bolt-on. makes me wonder..
if the clutch was changed they may have forgot to bleed the attesa when they put the box back in.

sounds like the tuner is stalling, who is the tuner? pm if you like.

what boost controller is it running, has this been set up correctly aswell?
what are the current settings of the vcam, is the tuner using hks supplied specs?
 

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Discussion Starter #8
well, update: it was bled and new transfer case oil went in because they also wanted to make sure it wasn't stuck in rwd mode .. no dash warnings either.

vcam settings are now:

LOAD/RPM 600 1200 2000 5000 8000
600 125 125 125 125 125
800 125 125 120 110 125
1100 125 125 95 110 125
1400 95 95 95 110 125
3000 95 95 95 110 125

Which are not too far off recommended settings..
 

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if the boost is freaking out like that, to me that says more boost controller than V-Cam. Variable valve timing helps, but not THAT much, to where the car is an uncontrollable monster. Having sealed off wastegates however, will produce exactly the effect you describe.

I generally view fast boost as a good thing (I've got 2860-5s) - it takes longer to build from 0.2 bar to 0.7 bar than to go from 0.7 to 2 bars, more than twice as long. In 1st gear, 0.7bar to 2 bars happens in what can't be more than a half second. I mean, it's nuts.

ATTESA sure works. Laying down that kind of power - for the past couple days Korea's been getting the monsoon rains, and with little traction on the roads...I decide to take the car out and do some clutch drops :D The front wheels are engaged straightaway and all four wheels are spinning. It's rather quite controlled in a straight line, I have to say. Never really aquaplaned either, even with 255 tires, but that may be due to the same effect as why a brick will never float on water :chuckle:
 

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btw, how much is "everything" when you're talking about your boost? If it instantly hits 15psi and then stays there locked in, congratulations! You've got a car most of us would die for. With that kind of instant boost and power, you then merely limit your power with your right foot (poor man's traction control) :)
 

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Discussion Starter #11
Having sealed off wastegates however, will produce exactly the effect you describe.
they said they tried it running on the stock (hks) wastegates, no boost controller trying to do anything, and it was still the same issue.

they said on the 4wd dyno there are "no issues". wtf.

I think I'm gonna have to get a 2nd opinion, even if the shop has no ability to fiddle with the fcon maps.
 

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Discussion Starter #13
btw, how much is "everything" when you're talking about your boost? If it instantly hits 15psi and then stays there locked in, congratulations!
Dunno man I guess I have to drive back and take it out for a more extended test.

Basically they told me it was too hard to drive and there was something still wrong, then I jumped in and verified that, yep, in 2nd it goes from normal to scary in a second but immediately let off, because I didn't want to end in the ditch :(

Thing is, when it was peaking @ ~290kw, getting 1 bar by 4000 or so, and hitting 1.3 bar, it was all nice and controllable:
in 1st: no problem, no time to make much boost before redline anyway
in 2nd: no problem, boost would ramp
in 3rd: I was relaxed enough to watch it ramp.

now at 15psi, I doubt it is making any more power. But it appears to be too tricky to use.. acting like a motorbike.
 

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Discussion Starter #14
another tidbit:

they said on the dyno power does get routed to front, but boost goes
almost vertical. Within a few hundred RPM. Which on the road is
probably going to be, er, challenging.
 

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call me crazy but every thread about 2530s ive read on here was a flamefest about how 2530s are spooling up way too late. insta max boost at 3k rpm sounds a bit.. impossible?
 

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Discussion Starter #16
I'll get hold of a dyno plot

no, it isn't insta-boost @ 3000, but it fills up quick at whatever .. somewhere between 3500 and 4000 I guess - (I've found out before that the tacho isn't to be trusted).
Perhaps the only problem is in 2nd gear and maybe 3rd. I used to enjoy 2nd gear, now it isn't fun anymore.

This is proving difficult to explain. I'll spend half a day in the car and try to figure out exactly what is irritating me. My first reaction was: this sucks, not what I expected at all. Tuner agrees with me. Maybe we are both wimps.
 

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The V-Cam is an incredible piece of kit, but a black art to calibrate. The F-Con V Pro has a 32 point map, while the V-Cam alone has a 16x16 matrix, if used fully.

I think your mapper is out of his depth, but I am also sure that the problems you are describing are definately not down to the V-Cam alone.

Mapped correctly, the car should do everything you expect, just with V-Cam it should do it about 1000rpm earlier and be much easier to drive at lower revs and speeds.

Major question of your tuner: Has he installed a V-Cam system before? No prevarication, it is a yes or no scenario. If he has, good. If he hasn't, get him to get help direct from HKS AU if possible. The unit is not a PFC and cannot be just thrown in.

Before you ask, yes, I have a V-Cam set up on my GTR. It is superb. Worth every penny.
 

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Discussion Starter #18
thanks.
I don't think there are any other vcam gtrs in australia.. and no he hasn't done one before (for that reason), but he isn't a power-fc guy, he is an fcon vpro guy and an HKS guy. He gets his help direct from HKS Japan when required.

Already I see a difference you are saying it is a 16x16 map but he is showing me a 5x5 map. That seems quite a fundamental difference :) do you know what your 16x16 ended up to be? can you copy/paste it?

Off boost it is all really smooth and driveable, AFRs are all good as well (have the knock amp and AFR display in the dash). I don't think there is a problem with the f-con tune, but maybe some combination of the two is leading them astray.
 

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I am afraid that Abbey Motorsport handle the spanners and magic on my car, so I cannot help. You could drop Mark an email, [email protected] and he may be able to give you some pointers. Then again, if your guy gets help direct from HKS Japan, you need a HKS mapping tech with V-Cam experience on the end of a phone or in person to unravel the issue.

Given what you paid, they should be happy to help. I also believe that an HKS Power Writer is entitiled to serious levels of support. Possibly time to invoke the 'send the cavalry' clause?
 

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i would like to see what the gain settings are on the boost controller

but having a quick look throught the vcam manual it looks like the vcam step one only has a 5x5 grid
 
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