Jump to content
SAU Community

Recommended Posts

Hi,

Although I am usually cautious, the other day I experimented with removing the boost restrictor on my R32 GTR to see what would happen. Car is mostly stock engine-wise, with only apexi pods and a 3.5" full exhaust (and perhaps what sounds suspiciously like an after-market fuel pump).

Some observations:

  • With the restrictor in, boost was peaking at 12.5psi
  • With the restrictor out, boost came on much quicker (:)) but peaked at just over 15psi (:P)

Some questions:

  • 12.5psi with the restrictor in seems pretty high compared to what I thought stock was (ie around 10?). Presume that this is just due to the free-er flowing exhaust?
  • I know people tend to be conservative with advising people against overboosting 15-year-old-ceramic-wheeled gtr turbos, but does anyone have insight as to what the safe limit is and whether peaking over 15psi is just stupid?
  • Rather than smash the old turbs, I am considering doing a full upgrade, but reckon that once I factor in turbos (~3k 2nd hand), a PFC (~$1k), injectors (~$0.7k) and a decent oil cooler (~$0.7k) I'm looking at around $6k plus $1k of labour. Is that the ballpark?

Cheers

Some questions:

  • 12.5psi with the restrictor in seems pretty high compared to what I thought stock was (ie around 10?). Presume that this is just due to the free-er flowing exhaust?
  • I know people tend to be conservative with advising people against overboosting 15-year-old-ceramic-wheeled gtr turbos, but does anyone have insight as to what the safe limit is and whether peaking over 15psi is just stupid?
  • Rather than smash the old turbs, I am considering doing a full upgrade, but reckon that once I factor in turbos (~3k 2nd hand), a PFC (~$1k), injectors (~$0.7k) and a decent oil cooler (~$0.7k) I'm looking at around $6k plus $1k of labour. Is that the ballpark?

Cheers

An R32 GTR is 20 years old - if you don't have $10,000 for a rebuild run it at the 12.5psi (exhaust raises stock boost).

For the upgrade - factor in $1000 for tune as well but you might get injectors & cooler cheaper & turbo price would depend.

point taken. I do have $10k but would rather spend it on a build rather than a rebuild :P

Another question: Can anyone explain the theoretical function of the boost restrictor to me? I've been studying the vacuum diagram, and it looks like the restrictor is in the line that goes to the wastegate actuators. To me it seems counter-intuitive that removing the restrictor works the way it does,

my brain says:

  • restrictor in => actuator sees pressure lower/later => wastegate opens later => more/earlier boost
  • restrictor out => actuator sees pressure higher/earlier => wastegate opens earlier => less/later boost

but the car says

  • restrictor in => ...? => less/later boost
  • restrictor out => ...? => more/earlier boost

Edited by semislickR32
What are you using to measure the boost pressure? Just wondering if it is a gauge issue as I have had one do the same.

i'm using a turbosmart eBoost2 controller gauge, which should be relatively accurate I guess.

And just in case you're wondering "why don't you just use the eBoost2 to control the boost instead of removing the restrictor?", it's because I haven't figured out how to hook it up yet - it was much easier on my old S15 with one turbo, non-cram-packed engine bay and an easy-to-understand vacuum diagram.

The R32GTR diagram in the manual is difficult to interpret to figure out where to get the boost signal from and how to get the solenoid control signal to the actuators... and previous forum searches and questions haven't been answered - poor me :P

With the EBC, you can use the existing wastegate actuator hose that goes to the stock boost controller, but you can't use the manifold pressure source the factory hose uses as it's from an already bled location at the rear near the clutch, need a new hose ran from the intake manifold to the EBC (and the bled source one blanked off). It's how Boostworx did the piping to my Gizzmo MS-IBC's actuator.

With the EBC, you can use the existing wastegate actuator hose that goes to the stock boost controller, but you can't use the manifold pressure source the factory hose uses as it's from an already bled location at the rear near the clutch, need a new hose ran from the intake manifold to the EBC (and the bled source one blanked off). It's how Boostworx did the piping to my Gizzmo MS-IBC's actuator.

thanks for the tip, that makes sense from looking at the diagram which shows that bleed. Do you happen to know whether the take-off from the intake manifold was from the fuel pressure reg signal line, or is there a better safer place to T in?

Thanks again...

FWIW my 120,000km old turbos let go at 13.5 psi on a very conservative tune. Factory turbo replacement interval is 100,000km and that's standard setup. Get the turbos changed now, the other stuff can wait until whenever you like.

New garrets will cost around $2600 for the pair - no need to go second hand. I'd guess installation would be at least $500, maybe a bit more. Do o2s at the same time, and if you're ever going to do the dumps do it at the same time.

thanks for the tip, that makes sense from looking at the diagram which shows that bleed. Do you happen to know whether the take-off from the intake manifold was from the fuel pressure reg signal line, or is there a better safer place to T in?

Thanks again...

You know that black box in the enginebay on the firewall on the drivers side, thats the MAP sensor that feeds the triple gauge boost reading, I tee'd in there as the pressure source for the PSI reading. You can tee off at the FPR directly, it will technically be less laggy than tee'ing into what I used. The stock MAP sensor gets pressure reading from the FPR anyway, it just enters the balance tube first, and a hose comes out the other end to it, then connects to that black box.

With the engine pressure source (stock one is the bled source), I can't remember if mine is before or after the throttle bodies.

You know that black box in the enginebay on the firewall on the drivers side, thats the MAP sensor that feeds the triple gauge boost reading, I tee'd in there as the pressure source for the PSI reading. You can tee off at the FPR directly, it will technically be less laggy than tee'ing into what I used. The stock MAP sensor gets pressure reading from the FPR anyway, it just enters the balance tube first, and a hose comes out the other end to it, then connects to that black box.

yep that's where I've got the PSI reading too.

With the engine pressure source (stock one is the bled source), I can't remember if mine is before or after the throttle bodies.

so I take it you didn't use the MAP sensor lines or the FPR lines for the solenoid pressure source... but in theory could you? I guess the only post-throttle-body source would be off the balance tube anyway,

My understanding is that the best place for getting the signal for the solenoid is pre-throttle and pre-intercooler if possible, but I assume that would require drilling into the hotpipe - not my preference by a long shot.

That is where my solenoid feed is connected, a small barb threaded into the 'twin turbo' pipe just before the large hose going to the intercooler.. Signal is coming from the same point as the map sensor.

  • 2 months later...

i recently took out my boost restrictor after i fitted my front pipe and high flow cat, and my boost didnt increase after the restrictor was removed !

im still only getting around 11ish psi !

what can be the problem??

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...