Hi guys,i want to do a boost leak test on my 300zx tt,I was wondering is it possible to make one up and where would i connect it,may take of the MAF?Also what psi should i do up to while doing the test.Any help would be great guys

Yes take off the MAF and replace it with a 80mm bung with hose.

 

I don't know what psi but I would suggest about 20psi as you won't go over that on normal driving and you don't want to blow vacuum lines off.

http://www.thumper300zx.com/z32/boostleaks/boost_leak_guide.htm

Above ^^^ document and note "you run the risk of popping seals out if you pressurize your intake tract above 5 psi"

Above ^^^ document and note "you run the risk of popping seals out if you pressurize your intake tract above 5 psi"

Ah well I did say 20psi was a guess [emoji38]

Ok guys i have another leak but i cannot find it,the leak seems to be at the back of the engine,down beside the plenum,anyone know what this might be?

Which side of the plenum - drivers or passenger?

Which side of the plenum - drivers or passenger?

 

Hi mate it seems to be passanger side,but not quite sure,i can see bubbles around the red mark in the pic but down very low

https://ibb.co/gEtg2o

Which side of the plenum - drivers or passenger?

 

You mean right or left :rolleyes:.

Hi mate it seems to be passanger side,but not quite sure,i can see bubbles around the red mark in the pic but down very low

https://ibb.co/gEtg2o

 

Do you mean between the plenum runners or between the plenum runner and firewall?

You mean right or left :rolleyes:.

 

Can’t inagine there are many wrong hand drive Z32s in the UK.

Do you mean between the plenum runners or between the plenum runner and firewall?

Between plenum runners,

Above ^^^ document and note "you run the risk of popping seals out if you pressurize your intake tract above 5 psi"

 

Erm... what seals cannot take more than 5 psi ?? never ever, ever had that happen and unless you charge it with a full volume at good pressure it is really will be difficult to find any leaks.

 

Jeff

The reason for the 5psi limit is in Ash Power's "6P" writeup (scroll down to DO NOT EXCEED 5PSI DURING A BOOST LEAK TEST):

 

http://www.twinturbo.net/nissan/300zx/forums/main/view/922678/The-6-Ps-Proper-Preparation-Prevents-Piss-Poor-Performancegt.html

Edited July 6, 20187 yr by AndrewG

The reason for the 5psi limit is in Ash Power's "6P" writeup (scroll down to DO NOT EXCEED 5PSI DURING A BOOST LEAK TEST):

 

http://www.twinturbo.net/nissan/300zx/forums/main/view/922678/The-6-Ps-Proper-Preparation-Prevents-Piss-Poor-Performancegt.html

 

So let me look at this from a practical point of view, for 18 years or so I did boost and air leak checks on maybe 2000 zeds could even be more, I used a correctly manufactured alloy housing with the garage air line system that was regulated to 110 psi via a 250 litre tank, the air volume and cfm of professional air tools require both high volume and a sustainable reserve of air. do you really think I was using 5psi to find boost leaks, can tell you I was not, but what I can tell you was when even a moderate leak was evident on the car then the top of that 250 litre tank soon triggered the motor to kick in soon enough.

 

The problem with using 5 psi is loose turbo or inter cooler cuffs can seal at that sort of pressure but blow at 10 psi, you would miss most leak that way, a fully sealed system is obvious from the first squeeze on the air line trigger, the leaking one`s will need way more volume to fill the leak first and then pressure the system, exactly what happens to the turbo`s when there is a leak and why you get lag and low performance.

 

I understand the difference between inlet tract and the rest, but its a case of what works and what does not, can tell you I always found the boost leaks and never damaged any that did not have leaks.

 

Jeff

You asked for the reason behind the 5psi limit and I've provided members with an authoritative reference.

Jeff, how certain are you that all of your customers cars that you charged up to your chosen pressure didn’t develop an oil leak? A latent defect introduced that was probably not discovered for a considerable amount of time, if at all.

You asked for the reason behind the 5psi limit and I've provided members with an authoritative reference.

 

So are you saying that a near decade of working EVERY DAY in a workshop on these cars is NOT an authoritative reference ? please expand, I am interested

 

Jeff, how certain are you that all of your customers cars that you charged up to your chosen pressure didn’t develop an oil leak? A latent defect introduced that was probably not discovered for a considerable amount of time, if at all.

 

Given that most of my customers from when I started remained customers till I retired then I am confident, and remember when I say customer, I mean the car, because when owners changed the cars still came back for service work etc.

 

Jeff

When I was last doing mine, I was doing about 7psi. Under 5 didn't seem to help me find the issue sadly. Turned out to be an O ring on the oil dipstick lol

I believe the 5psi thing has its origins in the FSM. Whilst I appreciate what your saying Jeff and common sense is a factor we must remember that someone could read this via the search function, take it as red and throw 60 PSI at it because well, you said it was “ok”. You didn’t but it could be read that way. A reasonable leak can be found by throwing 5psi in, its what’s recommended in the manual and is the safe advice to give those not in the know. Don’t you think?

So are you saying that a near decade of working EVERY DAY in a workshop on these cars is NOT an authoritative reference ? please expand, I am interested Jeff

 

 

No reply Andrew G ?... waiting buddy

 

 

I believe the 5psi thing has its origins in the FSM. Whilst I appreciate what your saying Jeff and common sense is a factor we must remember that someone could read this via the search function, take it as red and throw 60 PSI at it because well, you said it was “ok”. You didn’t but it could be read that way. A reasonable leak can be found by throwing 5psi in, its what’s recommended in the manual and is the safe advice to give those not in the know. Don’t you think?

 

Mmm ... I guess so, maybe? see remember all of this was new 20 + years ago and whilst been around these parts for a big part of that the tech and tricks if you like behind it all is really quite well known now and published all over the net, kind makes me think anyone who would contemplate 60psi really is a numptie rather than a newbie, but still I would argue that the 5 psi leak test will fail to find possible issues that seal below that, but leak above it, as I said before, a cuff left loose is still a good enough fit to hold 5 psi, get that car down the road and boost up and build then boom lost down the leak, boost up and lost again, boost now regulated by leak rather than the turbo actuator.

 

So how about we say a max of 15psi but this is not what I was really saying, its recoverable volume that is needed ie via an air tank with consistent pressure.

 

I do not post tech stuff here that I am not 100% sure of and experienced about over a substantial period I was in business, that remember only stopped as I retired to the sun.

Edited July 7, 20187 yr by JeffTT

Use a smoke tester to find the leak. No need for high pressure being charged into the system. Ash Powers is a infamous name in the world of zeds along with others like Nick Letsom and Kyle Puckett. Having been to a highly rated tuner recently they do not charge the system but use a smoke tester to find leaks just the easiest way to find a leak.

Use a smoke tester to find the leak. No need for high pressure being charged into the system. Ash Powers is a infamous name in the world of zeds along with others like Nick Letsom and Kyle Puckett. Having been to a highly rated tuner recently they do not charge the system but use a smoke tester to find leaks just the easiest way to find a leak.

 

Ok agree smoke test can be very useful looking for small low level leaks rather than by listening out for them, but a below 5 psi sealed cuff regardless of smoke or not is still sealed.... until its not... on the road.

 

Jeff

I'm certainly no mechanic, and probably know less than everyone else here. So no one take any of my words as gospel.... But when I was trying to find a leak, 5 psi just wasn't doing it. May be due to what Jeff is saying, or possibly if it's too big of a leak. So I went up to about 7psi and found it in minutes.

 

Also found stuff easily in the past, but with smoke matches and then the air