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RB20 Boost question

Cool Hand Luke
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Cool Hand Luke Community Regular

Cool Hand Luke

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I just fitted up a boost guage to my RB20 and was told that standard they run 8-9psi. Ive been having detonation problems once i get into higher gears but thought it was related to the standard intercooler (its in a 93 180sx so it gets almost no air flow). I was suprised that when the guage was hooked up it reads around 11.5psi or there abouts and slowly drops down at higher revs as i expected it to with the std turbo. Is this the standard levels? Im getting a PWR front mount on friday so im interested to see if the pinging is from that, or something like the fuel pump going because its currently fitted with a VL turbo pump which i would have thought it would be sufficient with the standard turbo... Is the VL pump that crap, or is it more likely the cooler, because if i take off it only starts to ping at higher revs in 3rd gear.

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MR R32 Experienced

MR R32

Posted
Posted

I have an R32 GTSt with a 3 inch exhaust from the turbo back and a pod filter. I recently fitted a boost gauge and found that the car runs at exactly 11psi, but I have not noticed it dropping off at the top of the range.

To be nonest, I dont really drive the car that hard, so I haven't had much of a chance to notice.

red17 Experienced

red17

Posted
Posted

Checked your timing? This can be a major cause of detonation and may mean you fuel pump is not "rooted" . Simple things first.

As for boost pressure, mine hits peak boost at about 11.5 psi around the 4300rpm mark (or it did when i had my stock dump pipe, rpm is probably lower now). Anyway it seems to be a standard sort of boost level for GTSt's running a semi decent cat back exhaust. Boost level can increase just from the increase in airflow the exhaust provides. Its normal for it to start dropping off toward about 9.5psi at peak rpm. The stock turbo is simply running out of puff.

Red17

Roy Grand Master

Roy

Posted
Posted

My vote is that there is nothing wrong with the fuel pump. Dont go replacing until you at lest throw a gauge on to see what rail pressure you have.

My RB runs about 12/13 psi with IC/filter and exhaust.

Do you still have std dump, front pipe, cat??? A slight drop of 1-2 psi up top could easily be an exhaust restriction.

My car pings and i think it has more to do with ignition advance of the OE ECU with Aus fuel, then the inlet air temp.

Even with my HKS (so i assume its reasonably effecient) intercooler im getting a bit of pinging from time to time. The good IC helps increase boost by 1-2psi due to the reduction in restriction, but, if the ignition advance is too aggressive for Aus fuels then irrespective of how low inlet temps are, it will still ping.

Its perhaps possible that by putting an IC on your car and witnessing the subsequent 1-2psi increase, that pinging may actually gets worse.

When i go to the track and want to be sure it doesnt ping, i use a 20-25% mix of Toluene with BP Ultimate. My experience is that this eliminates detonation, so tells me its more about ignition and crappy fuel then inlet temps.

Cool Hand Luke Community Regular

Cool Hand Luke

Posted
  • Author
Posted

I still have the standard cooler, but have a different filter, 3" exhaust from the turbo back with seperate dump pipe. It runs at 11-11.5psi then slowly drops off. I have a PWR front mount coming on friday. Has anyone had experience with octane boosters etc? It really makes me cringe when i hear it ping.... not knowing how much detonation the standard pistons will take.

justified2.4 - i havent run it yet, and wont till i get the detonation sorted out. But they run flat 14's or so with standard cooler, boost and with a nice exhaust. Nothing a bigger turbo wouldnt fix though :P.

Roy Grand Master

Roy

Posted
Posted

I hope your cooler fixes the pinging prob, and the drop off in boost at high rpms.

If your like me though you will find you have 1-2psi more boost, but engine still occasionally pings under load in 3rd and 4th gear.

The only time i really drive my car hard enough to notice pinging is the track, and so now normally run a toluene mix. I have found it to be pretty hard on plugs so dont use it on the street. (The pinging could also be contrbuting to short life of spark plugs, 10-15,000kms)

Roy Grand Master

Roy

Posted
Posted

I have tried Nulon and Wynns Race Formula.

My car doesnt ping that bad that i need it day to day... its only when i know im going to give it some stick like at a track day that i bother. Day to day im lucky to take it over 4000rpm!!!

Its just that with the toluene i actually feel a bit more top end performance and helps eliminate pinging. At $50 for 20L its pretty cheap too, but not entirely legal. (hence track only)

Mr R32 M-Spec Experienced

Mr R32 M-Spec

Posted
Posted

How much boost can the standard RB20 turbo take anyways, I have a dual stage BC ready to go in and have just ordered the the FMIC for the car. just want to know how much it will run before it dies. could it do 15PSI for example or is that too much for the standard one

Roy Grand Master

Roy

Posted
Posted

General rule of thumb is 1 bar is about as high as you want to venture. Some blow at 12psi, some last at 16psi.

It seems to depend on age/condition, quality of air filter, where you take your boost reading from (plenum or turbo etc).

My car is running 0.85 bar with the boost controller turned off. (measured at the plenum) Three years and 80,000kms, and countless track days she is still going strong.

If you need the turbo to last i would stick with freeing up the inlet and exhaust and run the resultant standard wastegate actuator boost level of about 12-14psi.

If you can afford to have a turbo let go on you , then you can run them a little harder. I dont personally know anyone that has blown a RB20/25 turbo so i for one dont believe they are actually that fragile.

Sydneykid Grand Master

Sydneykid

Posted
Posted

Hi Roy, 5 laps at Wakefield at 12 psi, rattle, rattle white smoke, no turbine in the housing, found it in the cat in 3 pieces. It is not only too much boost that kills them, but excess heat as well. It had been running at 12 psi for a couple of months on the road, no problems, but the heat after 5 laps was too much at that boost level.

It had a good airfilter and intercooler, nice exhaust, big fuel pump and it was properly tuned with a PFC. So it was not the support systems that caused the ceramic turbine to fail. I have seen 3 RB turbos do exactly the same thing.

So it does happen.

Mr R32 M-Spec Experienced

Mr R32 M-Spec

Posted
Posted

Nice!

thanx guys, I just wanted to know how much it will run. I have a new turbo sitting at home (Garret 500HP application) but don't want to spend the money getting it on till the other one bites the dust. I am fitting a D/S boost controller with the new cooler

I get the new cat today and the new cooler will be before the next track day. I have a standard airbox but a K&N Panel filter. it runs good at the moment, but as usual you feel the need for more power.

Roy Grand Master

Roy

Posted
Posted

Sydneykid

I dont disagree with the fact that the turbines do let go.

But , i can only speak for my car which has done 20-30 track days at Eastern Creek and Wakefield. One day at Eastern Creek (Plenty of full throttle) i ran 1 bar all day with a tank of toluene. (i think thats 6 x 20min sessions)

Never done it since as it didnt really make the car any quicker so why run more boost.

But that still makes for plenty of times at the track where i have run 0.85bar (thats what the car runs with the AVC-R turned off)

The car your referring to, is that the Ben Ellis R34? Did he not still have the factory dump pipe on his car when the turbo let go. Also do you know if he was measuring boost at the inlet manifold or turbo outlet?

Out of interest would you put that down as bad luck, or common for that boost level and Skylines at the track.

Luckily im still to see a Skylines turbo let go at the track.

My thoughts are if you need your turbo to hang together, dont boost them, if you must use an EBC to get them to ramp up on boost a little quicker, but dont increase the peak boost.

For me and my car (other cars could well be different) there is not really a difference in performance between 0.85 and 1bar. When i get my Power Fc tuned im going to tune it for 1bar and see how it goes. Hopefully when its properly tuned, running a little more boost may actually yield more hp.

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