Jump to content
SAU Community

Recommended Posts

hey all, just acquired my car off a fellow forum member:) anyways after owning it for a couple of weeks am stoked with it couldn't be happier.

Anyways after taking it for a couple of spirited drives, i'm finding the car is overboosting in 3rd gear +.

Car has the following

RB25 motor

Power FC

AVC-R

250-270rwkw

The car has 2 settings 1bar and .5 bar

When i set it at 1 bar it goes to 1.1 bar in second holds then once i go to third boost keeps rising seen it go to 1.4 bar each time but don't know if it will keep going, as i dont wanna be cleaning bits of turbo out of my cat(if it has one) still to check this.

When i have it on .5 bar 2nd gear goes to .7 bar then holds, once go in to third it seems to go up to 1.4 bar again.

Clutch is on its way out so in third it generally just slips and boost goes up

BOV is blocked off which is the next thing to change(unsure if this could be doing this)

I'm unsure to why it is doing this, and really want to fix the problem,

Any help or experiences would be appreciated.

Thanks all in advance

Nath

Link to comment
https://www.sau.com.au/forums/topic/315578-overboosting-issue/
Share on other sites

The obvious area to investigate is the AVCR. I would suggest taking it to your local dyno and trying to run the car just on wastegate to see what it is doing, then tune the avcr on its low and high setting. Also, is it just recording a peak of 1.4bar or is it holding that throughout the rev range?

Boost can be different in the higher gears, as it allows the engine to load up, which in turn works the turbo harder creating more boost on the same boost controller solenoid rate.

agree retune the AVCR

there is a detailed video on youtube on how to tune the AVCR correctly

the old HKS controllers did a self learn mode when you take off in 3rd gear and run to redline 3 times

it would then during this process watch the wastegate pressure and manifold pressure and how long it took to boost build

so i suggest when setting up your AVCR you base it off 3rd gear runs

ie dont tune boost in 1st or 2nd, too much ramp, too much roadspeed for accurate control

thanks paul, i will look in to retuning the AVC-r. in relation to it hitting peak at 1.4bar. not sure if it will keep going but when i record on the defi controller and hit the recent button it states 1.4bar peak. dont know if this helps.

Turn down the gains on the AVC-R, the previous owner must have the gain set too high.. The AVC-R also allows you to graph the boost vs time. You will see that it might spike to 1.4bar but then drops to 1.1/1.0

Keep on lowering the gain till you get good results, I tend to have my gain set so it spikes 0.1bar past my desired boost as it brings on boost a tad quicker.

Don't use these settings as gospel, each turbo/actuator is different.

Set using PowerFC Boost kit:

0.8 bar 40 gain / spikes to 1.0 bar

1.0 bar 48 gain / spikes to 1.1 bar in 3rd

1.15 bar 54 gain / spikes to 1.2 bar in 3rd

1.30 bar 62 gain / spikes to 1.38 bar in 3rd

i've had alook at tutorials but they are all for the newer avc-r. mine is an old school item no adjustable features.

Power FC doesnt seem to be set up for boost as when monitoring shows ---- nothing.

I'm starting to think it's a wastegate/actuator problem as it is internally gated.

What does evri1 else think?

Turn down the gains on the AVC-R, the previous owner must have the gain set too high.. The AVC-R also allows you to graph the boost vs time. You will see that it might spike to 1.4bar but then drops to 1.1/1.0

Keep on lowering the gain till you get good results, I tend to have my gain set so it spikes 0.1bar past my desired boost as it brings on boost a tad quicker.

Don't use these settings as gospel, each turbo/actuator is different.

Set using PowerFC Boost kit:

0.8 bar 40 gain / spikes to 1.0 bar

1.0 bar 48 gain / spikes to 1.1 bar in 3rd

1.15 bar 54 gain / spikes to 1.2 bar in 3rd

1.30 bar 62 gain / spikes to 1.38 bar in 3rd

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now


  • Similar Content

  • Latest Posts

    • I know why it happened and I’m embarrassed to say but I was testing the polarity of one of the led bulb to see which side was positive with a 12v battery and that’s when it decided to fry hoping I didn’t damage anything else
    • I came here to note that is a zener diode too base on the info there. Based on that, I'd also be suspicious that replacing it, and it's likely to do the same. A lot of use cases will see it used as either voltage protection, or to create a cheap but relatively stable fixed voltage supply. That would mean it has seen more voltage than it should, and has gone into voltage melt down. If there is something else in the circuit dumping out higher than it should voltages, that needs to be found too. It's quite likely they're trying to use the Zener to limit the voltage that is hitting through to the transistor beside it, so what ever goes to the zener is likely a signal, and they're using the transistor in that circuit to amplify it. Especially as it seems they've also got a capacitor across the zener. Looks like there is meant to be something "noisy" to that zener, and what ever it was, had a melt down. Looking at that picture, it also looks like there's some solder joints that really need redoing, and it might be worth having the whole board properly inspected.  Unfortunately, without being able to stick a multimeter on it, and start tracing it all out, I'm pretty much at a loss now to help. I don't even believe I have a climate control board from an R33 around here to pull apart and see if any of the circuit appears similar to give some ideas.
    • Nah - but you won't find anything on dismantling the seats in any such thing anyway.
    • Could be. Could also be that they sit around broken more. To be fair, you almost never see one driving around. I see more R chassis GTRs than the Renault ones.
    • Yeah. Nah. This is why I said My bold for my double emphasis. We're not talking about cars tuned to the edge of det here. We're talking about normal cars. Flame propagation speed and the amount of energy required to ignite the fuel are not significant factors when running at 1500-4000 rpm, and medium to light loads, like nearly every car on the road (except twin cab utes which are driven at 6k and 100% load all the time). There is no shortage of ignition energy available in any petrol engine. If there was, we'd all be in deep shit. The calorific value, on a volume basis, is significantly different, between 98 and 91, and that turns up immediately in consumption numbers. You can see the signal easily if you control for the other variables well enough, and/or collect enough stats. As to not seeing any benefit - we had a couple of EF and EL Falcons in the company fleet back in the late 90s and early 2000s. The EEC IV ECU in those things was particularly good at adding in timing as soon as knock headroom improved, which typically came from putting in some 95 or 98. The responsiveness and power improved noticeably, and the fuel consumption dropped considerably, just from going to 95. Less delta from there to 98 - almost not noticeable, compared to the big differences seen between 91 and 95. Way back in the day, when supermarkets first started selling fuel from their own stations, I did thousands of km in FNQ in a small Toyota. I can't remember if it was a Starlet or an early Yaris. Anyway - the supermarket servos were bringing in cheap fuel from Indonesia, and the other servos were still using locally refined gear. The fuel consumption was typically at least 5%, often as much as 8% worse on the Indo shit, presumably because they had a lot more oxygenated component in the brew, and were probably barely meeting the octane spec. Around the same time or maybe a bit later (like 25 years ago), I could tell the difference between Shell 98 and BP 98, and typically preferred to only use Shell then because the Skyline ran so much better on it. Years later I found the realtionship between them had swapped, as a consequence of yet more refinery closures. So I've only used BP 98 since. Although, I must say that I could not fault the odd tank of United 98 that I've run. It's probably the same stuff. It is also very important to remember that these findings are often dependent on region. With most of the refineries in Oz now dead, there's less variability in local stuff, and he majority of our fuels are not even refined here any more anyway. It probably depends more on which SE Asian refinery is currently cheapest to operate.
×
×
  • Create New...