Jump to content
SAU Community

Recommended Posts

What vacume are you seeing with your r33 at idle?

Im trying to work out if i have boost leak that could cause my R33 GTST car to be overboosting to around 13psi with the std actuator.

It was giving me 20psi vacume at idle but after checking some pipes its now 15psi vacume, the serario of boost leak cause overboosting is confussing me but it makes sence if the actuator doesnt get pressure?yet still im confussed lol

Im still learning with turbo cars and pressure turbo systems so please correct my thinking if its wrong?

I have worked out i am hitting boost cut at around 12 psi but what i cant work out is why im boosting that hard, no boost controller(directly hooked up to motor for min boost) Actuator feel free and shuts ok.

It was running ok for one day and held 10psi firm with no issues but now issues back.

I think its boost leak giving me boost creep from 10 to 12-13?

Link to comment
https://www.sau.com.au/forums/topic/407086-what-is-your-vacume-of-your-rb25det/
Share on other sites

boost creep is not to do with boost leaks its to do with the wastegate setup,

if you have a leak in the hose that connects to the wastgate then yes you'll have more boost,

did you hook it up correctly yet???

Edited by SliverS2

Not yet as only the std nipples are there(one in incooler pipe before throttle body im currently using and one nipple on bov return line i have blocked off)

im planning to tap the pipe just after the turbo soon as i buy a nipple and some epoxy type stuff..

What is annoying is that it was running ok the other day.

My blitz intercooler uses the std top engine pipes and crosses over under the cooler so top pipes are all still standard.

You can't really measure vacuum in psi.

Oh come on! That is not true. You can use any pressure unit you like to measure any positive or sub atmospheric pressure you like. There is no difference. The only argument that you can make is that psi is a stupid pressure unit that we should have stopped using in Australia in 1966 when we adopted the self consistent SI unit system.

Oh, and to the OP, the pressure you were seeing at -20 or -15 "units" was almost certainly not psi. Have a closer look at your guage. The boost side will probably be in psi, but the vacuum side will be in some other unit. FWIW, if your vacuum is only about 15-20 inches of Mercury (another stupid f*kking pressure unit) then you either have a sloppy motor or a leak.

Oh, and to the OP, the pressure you were seeing at -20 or -15 "units" was almost certainly not psi. Have a closer look at your guage. The boost side will probably be in psi, but the vacuum side will be in some other unit. FWIW, if your vacuum is only about 15-20 inches of Mercury (another stupid f*kking pressure unit) then you either have a sloppy motor or a leak.

This is more what I was getting at. People often put -15psi vacuum, when as far as I'm aware it would be more like a fraction of 1 psi, or a positive measurement in PSIa. I'm not going to start off the whole PSIa vs PSIg argument again. I dont like using -psi because theres not really any manufacturer, aftermarket or OEM that uses it

mmHg or inHg is used because it has a neutral, a positive and a negative. I've used a mmH20 gauge to measure blowby (From memory) on a diesel engine and it works really well, even if it doesnt make sense to alot of people.

Most gauges now are digital anyway, which makes it easier then carrying around a long mmH20 gauge everywhere

But most I've seen will change units when measuring boost vs vacuum. kPa negative, Kgcm^2 positive

Anyway back on topic:

As I said theres not alot of point in comparing setups as its to varied. Mine gauge will sit on -14 in summer and -16 in winter, and adjusting timing I can get it to sit anywhere between -18 and -12. I'm also running 3" Cooler piping which will make some difference

Not yet as only the std nipples are there(one in incooler pipe before throttle body im currently using and one nipple on bov return line i have blocked off)

im planning to tap the pipe just after the turbo soon as i buy a nipple and some epoxy type stuff..

What is annoying is that it was running ok the other day.

My blitz intercooler uses the std top engine pipes and crosses over under the cooler so top pipes are all still standard.

Never mind the epoxy just drill and tap the turbo housing.

This is more what I was getting at. People often put -15psi vacuum, when as far as I'm aware it would be more like a fraction of 1 psi, or a positive measurement in PSIa. I'm not going to start off the whole PSIa vs PSIg argument again. I dont like using -psi because theres not really any manufacturer, aftermarket or OEM that uses it

mmHg or inHg is used because it has a neutral, a positive and a negative. I've used a mmH20 gauge to measure blowby (From memory) on a diesel engine and it works really well, even if it doesnt make sense to alot of people.

Have you ever stopped to wonder what happens to "mm of arbitrary liquid" pressure units when the local gravity field is not 9.807 m/s^2 ?

There is only one pressure unit that we should be using. That is the Pascal, and its SI multiples and fractions.

I'm not arguing what we should and shouldnt use. I'm just saying what I have seen

Shouldn't have opened up that can of worms.

I'm not turning this into an argument, especially seen as I gave up physics years ago.

It's all good

think OP has disappeared anyway

Have you ever stopped to wonder what happens to "mm of arbitrary liquid" pressure units when the local gravity field is not 9.807 m/s^2 ?

There is only one pressure unit that we should be using. That is the Pascal, and its SI multiples and fractions.

i hope you also take into account change in local barometric pressure then if your getting that accurate

pretty sure most boost guages also work in psi or bar for positive pressure and mm/inHg for negative (mm/inches of mercury)

pretty sure most of the cars i've had have been around 10-15 inHg at idle

you are also not likely to detect a boost leak at idle as the silicone joiners that usually leak will be under vacuum and seal themselves against the pipe

but i have heard of people spraying start-ya-bastard on the joiners as you can head the engine pickup if some spray gets in

i hope you also take into account change in local barometric pressure then if your getting that accurate

pretty sure most boost guages also work in psi or bar for positive pressure and mm/inHg for negative (mm/inches of mercury)

Some people design equipment that gets used outside the Earth's local environment. If they were so backward as to use units of pressure that relied on the height of a column of liquid, then there was be at least 2 ways that they could have spectacular calculational failures. Just like when the Mars probe smacked into Mars instead of landing on it because one group of engineers was using SI units and the other was using US customary units. It is 2012. Time to give up on shithouse units. All I'm saying.

As to me correcting for local barrometric pressure....yes, in fact, when I am doing pitot measurements of air flows in industrial equipment (and various related exercises) I do in fact calculate the actual air density based on the actual local pressure (and elevation) and temperature. Of course I do. Anyone who doesn't is just being lazy.

Some people design equipment that gets used outside the Earth's local environment. If they were so backward as to use units of pressure that relied on the height of a column of liquid, then there was be at least 2 ways that they could have spectacular calculational failures. Just like when the Mars probe smacked into Mars instead of landing on it because one group of engineers was using SI units and the other was using US customary units. It is 2012. Time to give up on shithouse units. All I'm saying.

As to me correcting for local barrometric pressure....yes, in fact, when I am doing pitot measurements of air flows in industrial equipment (and various related exercises) I do in fact calculate the actual air density based on the actual local pressure (and elevation) and temperature. Of course I do. Anyone who doesn't is just being lazy.

fair enough if its something important and a variance in pressure is actually a big deal

i thought we were talking about boost gauges

i still don't get why jap boost gauges come in american units too

i'm all for metric units, it makes my life a lot easier

Hey guys, yeah i was not think right and yeah it's obvious now i think about it, boost pressure is way more than vacume would ever be,

The whole reason i was asking about vacume was seeing if it could be a diagnosis for boost leak, well good story today as i think my fmic was leaking.

One $4 clamp and no more overboost, coil pack type missfire feeling.

My car has actually never felt so crisp or fast, it boost well to around 9psi.

Before my car had a very soft but loud feeling, it would boost fast but i think it was free boosting?, with the air leak the power was very on or off, it felt sluggish and the exhaust was loud.

Anyway thankyou everyone for your input, ive now learned about the mercury system lol,hope my car cotinues to run well but fnger crossed.

I plead to everyone to check there car for air leaks, your car might be lagging and you dont even realise it, i thought my issue was coilpacks but now im thinking it wasnt even electrical.

If we do a forum catch up ,beers on me :)

Edited by cosworth1971

good to hear its fixed, but i would of thought the boost would of gone even higher after a boost leak was fixed...

when i fixed my boost leak it didnt drop in boost.

you sure you didnt just find a hidden boost controller or somthing?? :P

Edited by SliverS2

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

    • The other problem was one of those "oh shit we are going to die moments". Basically the high spec Q50s have a full electric steering rack, and the povo ones had a regular hydraulic rack with an electric pump.  So couple of laps into session 5 as I came into turn 2 (big run off now, happily), the dash turned into a christmas tree and the steering became super heavy and I went well off. I assumed it was a tyre failure so limped to the pits, but everything was OK. But....the master warning light was still on so I checked the DTCs and saw – C13E6 “Heat Protection”. Yes, that bloody steering rack computer sitting where the oil cooler should be has its own sensors and error logic, and decided I was using the steering wheel too much. I really appreciated the helpful information in the manual (my bold) POSSIBLE CAUSE • Continuing the overloading steering (Sports driving in the circuit etc,) “DATA MONITOR” >> “C/M TEMPERATURE”. The rise of steering force motor internal temperature caused the protection function to operate. This is not a system malfunction. INSPECTION END So, basically the electric motor in the steering rack got to 150c, and it decided to shut down without warning for my safety. Didn't feel safe. Short term I'll see if I can duct some air to that motor (the engine bay is sealed pretty tight). Long term, depending on how often this happens, I'll look into swapping the povo spec electric/hydraulic rack in. While the rack should be fine the power supply to the pump will be a pain and might be best to deal with it when I add a PDM.
    • And finally, 2 problems I really need to sort.  Firstly as Matt said the auto trans is not happy as it gets hot - I couldn't log the temps but the gauge showed 90o. On the first day I took it out back in Feb, because the coolant was getting hot I never got to any auto trans issues; but on this day by late session 3 and then really clearly in 4 and 5 as it got hotter it just would not shift up. You can hear the issue really clearly at 12:55 and 16:20 on the vid. So the good news is, literally this week Ecutek finally released tuning for the jatco 7 speed. I'll have a chat to Racebox and see what they can do electrically to keep it cooler and to get the gears, if anything. That will likely take some R&D and can only really happen on track as it never gets even warm with road use. I've also picked up some eye wateringly expensive Redline D6 ATF to try, it had the highest viscosity I could find at 100o so we will see if that helps (just waiting for some oil pan gaskets so I can change it properly). If neither of those work I need to remove the coolant/trans interwarmer and the radiator cooler and go to an external cooler....somewhere.....(goodbye washer reservoir?), and if that fails give up on this mad idea and wait for Nissan to release the manual 400R
    • So, what else.... Power. I don't know what it is making because I haven't done a post tune dyno run yet; I will when I get a chance. It was 240rwkw dead stock. Conclusion from the day....it does not need a single kw more until I sort some other stuff. It comes on so hard that I could hear the twin N1 turbos on the R32 crying, and I just can't use what it has around a tight track with the current setup. Brakes. They are perfect. Hit them hard all day and they never felt like having an issue; you can see in the video we were making ground on much lighter cars on better tyres under brakes. They are standard (red sport) calipers, standard size discs in DBA5000 2 piece, Winmax pads and Motul RBF600 fluid, all from Matty at Racebrakes Sydney. Keeping in mind the car is more powerful than my R32 and weighs 1780, he clearly knows his shit. Suspension. This is one of the first areas I need to change. It has electronically controlled dampers from factory, but everything is just way too soft for track work even on the hardest setting (it is nice when hustling on country roads though). In particular it rolls into oversteer mid corner and pitches too much under hard braking so it becomes unstable eg in the turn 1 kink I need to brake early, turn through the kink then brake again so I don't pirouette like an AE86. I need to get some decent shocks with matched springs and sway bars ASAP, even if it is just a v1 setup until I work out a proper race/rally setup later. Tyres. I am running Yoko A052 in 235/45/18 all round, because that was what I could get in approximately the right height on wheels I had in the shed (Rays/Nismo 18x8 off the old Leaf actually!). As track tyres they are pretty poor; I note GTSBoy recently posted a porker comparo video including them where they were about the same as AD09.....that is nothing like a top line track tyre. I'll start getting that sorted but realistically I should get proper sized wheels first (likely 9.5 +38 front and 11 +55 at the rear, so a custom order, and I can't rotate them like the R32), then work out what the best tyre option is. BTW on that, Targa Tas had gone to road tyres instead of semi slicks now so that is a whole other world of choices to sort. Diff. This is the other thing that urgently needs to be addressed. It left massive 1s out of the fish hook all day, even when I was trying not too (you can also hear it reving on the video, and see the RPM rising too fast compared to speed in the data). It has an open diff that Infiniti optimistically called a B-LSD for "Brake Limited Slip Diff". It does good straight line standing start 11s but it is woeful on the track. Nismo seem to make a 2 way for it.
    • Also, I logged some data from the ECU for each session (mostly oil pressures and various temps, but also speed, revs etc, can't believe I forgot accelerator position). The Ecutek data loads nicely to datazap, I got good data from sessions 2, 3 and 4: https://datazap.me/u/duncanhandleyhgeconsultingcomau/250813-wakefield-session-2?log=0&data=7 https://datazap.me/u/duncanhandleyhgeconsultingcomau/250813-wakefield-session-3?log=0&data=6 https://datazap.me/u/duncanhandleyhgeconsultingcomau/250813-wakefield-session-4?log=0&data=6 Each session is cut into 3 files but loaded together, you can change between them in the top left. As the test sessions are mostly about the car, not me, I basically start by checking the oil pressure (good, or at least consistent all day). These have an electrically controlled oil pump which targets 25psi(!) at low load and 50 at high. I'm running a much thicker oil than recommended by nissan (they said 0w20, I'm running 10w40) so its a little higher. The main thing is that it doesn't drop too far, eg in the long left hand fish hook, or under brakes so I know I'm not getting oil surge. Good start. Then Oil and Coolant temp, plus intercooler and intake temps, like this: Keeping in mind ambient was about 5o at session 2, I'd say the oil temp is good. The coolant temp as OK but a big worry for hot days (it was getting to 110 back in Feb when it was 35o) so I need to keep addressing that. The water to air intercooler is working totally backwards where we get 5o air in the intake, squish/warm it in the turbos (unknown temp) then run it through the intercoolers which are say 65o max in this case, then the result is 20o air into the engine......the day was too atypical to draw a conclusion on that I think, in the united states of freedom they do a lot of upsizing the intercooler and heat exchanger cores to get those temps down but they were OK this time. The other interesting (but not concerning) part for me was the turbo speed vs boost graph: I circled an example from the main straight. With the tune boost peaks at around 18psi but it deliberately drops to about 14psi at redline because the turbos are tiny - they choke at high revs and just create more heat than power if you run them hard all the way. But you can also see the turbo speed at the same time; it raises from about 180,000rpm to 210,000rpm which the boost falls....imagine the turbine speed if they held 18psi to redline. The wastegates are electrically controlled so there is a heap of logic about boost target, actual boost, delta etc etc but it all seems to work well
    • hahah when youtube subscribers are faster than my updates here. Yes some vid from the day is up, here:  Note that as with all track day videos it is boring watching after the bloopers at the start.  The off was a genuine surprise to me, I've literally done a thousand laps around the place and I've never had instability there; basically it rolled into oversteer, slipped, gripped and spat me out. On the way off I mowed down one of the instructor's cones and it sat there all day looking at me with accusing cone eyes as I drove past. 1:13:20 was my fastest lap, and it was in the second session, 3rd lap.  It (or me!) got slower throughout the day as it got hotter.      
×
×
  • Create New...