Engine mods, what should I do?

I disagree. Here is the stock turbo compressor map. You'll note that at the right flow rate it is 70% efficient at 23 psi. Not saying you should run that but the point is the stock turbos are not heat pumps after 14psi.



I haven't run anything less than 18 psi since 12/07/2013. I have been going wide open throttle at least once or twice a day every day since then. No issued at all. My turbos are stock so is my engine. I have stock injectors + FPR.

(Run 18psi on the wrong tune such as the stock tune and you will have trouble of course. I certainly wouldn't go over 14psi without a tune on a dyno by someone who knows what they are doing...personally I wouldn't go over stock 9.5 psi boost without a tune to match)

 

As long as we are on the topic of what turbos can do:

I have stock turbos and won the "Highest Stock Turbo" class in the UAS July 2013 Z32 Dyno comp with 252.1 rwkw at 18psi.

That's me at position 02.



Here is my dyno graph from that comp.



Being stock turbos it can't hold 18psi all the way to redline but that's OK it has the torque where I need it for everyday driving. Personally I've never been temped to upgrade from stock turbos.

 

are u sure yours arent high flowed, 252 rwkw at 15.5psi is very rare for stock turbos

 

Rare but possible. I got around the same on a mainline dyno at the same boost... well 16psi actually. Its not impossible if your motor is in good shape..... Mine has only done 20k in 10 years though and had excellent compression numbers. Might be worth checking the condition of the motor while your at it... Most ppl cars these days are over 150k + mark so these days its harder to find stock turbo TT's pulling high numbers

 

This is my car still with stock engine and turbos after another tune (and a few more minor mods - dump pipe or something can't remember)



My full mode list is:

- Stock (not rebuilt 23y old) engine.
- Stock (rebuilt) turbos.
- Stock injectors + FPR.
- Walbro E85 400 litre ph Fuel Pump
- Specialty Z 3" expansion dumps
- 3" stainless steel exhaust from turbos.
- UAS 3" center mufflers and 3" straight through mufflers.
- Turbosmart manual boost controller.
- Z1 BA SMICs (biggest SMICs available for the Z or so they claim)
- Nistune ECU
- Selin translator with dual MAFs and dual 3A racing pods.

PS: I always use Shell VPower 98 octane and every single tank I add Nulon total fuel system cleaner to raise octane to 100 (its not sold as an octane booster but it is quite an effective one according to this study http://www.pexcom.com.au/z32cms/e107_plugins/content/content.php?content.13). (Also note that after 130 bottles the NTFS cleaner has not damaged my injectors nor should it).

I'll also add that I run more than 18psi now (with less timimg) with no problems but this being the internet I don't want to give the wrong people bad ideas so won't say how much more.

 

How much base fuel pressure do you run? My zed at 16psi boost and 54psi fuel pressure hits 97% duty cycle. 1 degree of timing more and they max out.

 

if its stock fuel pressure they must be off the map

 

Yeah they are stock. Yeah that's rare. I'll admit most get around 230 rwkw. Depends how far the tuner is willing to push it I guess.

That was with Dave Aspery who has since left UAS.

Actually the new (or old) guy there Ben retuned it on 20/6/2014 and turned it down to 230 rwkw (after a year at +250). No doubt pulled a ton of timing.

So to make up for the lost power I turned the boost up to 24 psi (This is crazy land - don't anyone copy me.).

The acceleration is absolutely amazing though. Motor hasn't blown up yet and I thrash it a lot.

I'm not the only one running stockies at 1.7 bar so does this guy NOZ who is a tuner in the UK http://www.300zx.co.uk/forums/showthread.php?179724-Newbie-from-newcastle&p=1851043#post1851043



For the record I didn't just turn the boost up one day and hope for the best (well I sort of did but there was a bit of method to my madness). The story of my boost increase is as follows:

I originally turned my boost from 15 to 18 psi for the dyno comp not being aware that on my boost controller 1 click appears to be equal to 1 psi. I thought I was only giving a minor boost increase for the dyno comp and was shocked to see the boost rise from the previous 15psi to 18psi on the dyno for the comp as shown in the previous dyno graph. So I realised apparently 3 clicks equals 3psi. The motor survived so I left it at 18psi since then.

Nearly a year later on 20/6/2014 Ben turned the power down to 230 kw at 18psi (he was tuning without my usual octane booster though and after replacing the crank angle sensor that had been playing up). He also replaced the stock fuel pump with a Walbro as there was apparently no fuel in the return line (a stock pump shouldn't be a problem so obviously was an old stock pump). Ben also added an FPR to my setup after finding I was running lean at high rpm. (That explains the mad wheel spinning power gain I had been getting at high rpm).

Knowing the motor had survived a year at the 271 rwkw level including many WOT runs on 30 deg days I reasoned with so much timing pulled (judging by the massive power loss) and with a less lean AFR thanks to my new FPR it could handle at least another 2 more psi. So to try and recoup some of my lost power I turned the boost up to 20 psi (2 clicks past the 18psi setting). I know where the 18psi setting is because after the dyno comp I used a grinder to notch that location into the boost wheel.

Some months later I discovered I had accidently set the boost to 22psi (18psi + 4 clicks). I think it might have happened when I tried to turn the boost down to 18psi before giving it to my mechanic (don't want him blowing the motor on a test drive). I may have turned the direction wrong and set it to 22 psi instead of 18psi then. I'm sure Andrew wouldn't have turned it up to 22psi. Anyway as I had driven it around for a probably a month at 22psi without the motor destructing I decided to leave it there.

Some months later being inspired by the post of the afore mentioned NOZ on the UK forum I decided to turn the boost up to 24psi (18psi + 6 clicks).

I had previously driven the car Sydney to Brisbane and back and Coonabarabran and back with many 5th gear WOT overtakes on 15 psi + 3 full boost wheel turns (back when I thought one turn not 1 click was 1 psi). So I had previously accidently driven about 3K on what ever the turbos max out at and the motor had survived albeit that time it did rattle on every overtake (this had been with Nistune fitted but without a tune because the clutch had been slipping and Dave wanted me to get a knew clutch before he finished the tune).

Anyway knowing the car had already survived that much boost previously i.e. it didn't immediately destruct - albeit it was too much boost for the tune at the time and believing I now probably had a tune suitable for it and based on a tuner in the UK thinking you can run 1.7 bar I decided to live dangerously and turn the boost up to 24 psi.

Actually I don't really know if its 24 psi, its 18psi + 6 licks of the boost wheel. The turbos may not even make that (they certainly don't make more than 17psi after 5K rpm) but according to the afore posted turbo compressor map they can in theory make it momentarily in the mid range.

What ever boost they make the car is damn fast, damn fun and so far quite reliable. And every car is different so if anyone tries to copy me they may destroy their motor. So don't copy me this post is purely for entertainment purposes (Also did I mention I always run 100 octane not 98).

 

Maybe they were off the map but the AFR in the 271 rwkw dyno graph looks OK to me. Those dyno graphs I posted are without an FPR - so they were at stock fuel pressure.

But it's not stock fuel pressure anymore thanks to my FPR. Its higher or so UAS told me, I can't remember the pressure if they told me. But they did install the FPR specifically to raise the pressure above stock. - but in the dyno graph I posted it was at stock pressure.

 

One important point I should mention (although people rarely do) is I am running cold plugs (NGK Iridium 8 heat range) that match the boost I am running.

You don't want a hot spark plug to ignite your mixture too soon and put a hole in your piston.



To quote specialty Z

 

You're misreading that map, the bottom axis is pounds (mass) of air per minute, not pounds per square inch of manifold pressure.

Using the approximations from Garrett's turbo tech 10lbs/min of air will make ball-park 100hp at the flywheel, two turbos flowing 20lbs/min gives 400hp ~250rwkw then you need to choose the right combination of manifold pressure and engine volume to actually achieve that flow.

For pressure, the y-axis is the pressure ratio which is [(absolute manifold pressure) plus (atmospheric pressure) minus (absolute pressure at compressor inducer)] divided by atmospheric pressure.

Guessing 2psi drop between the filter and compressor housing gives you a pressure ratio of 2.08 at 14psi at sea level and 2.36 at 18psi, 2.7 at 23psi. So at 14psi you're running through the 74% island just before you make 400hp, at 18psi you're just keeping within 72%, ramp it up to 23psi and you're running through 65-68% and what's worse you're tightly squeezed between the surge, choke and overspeed lines. Any gain in elevation will reduce atmospheric pressure and make the pressure ratio higher.

Efficiency is a measure of how much air you've packed in compared to how much heat you've generated so you are indeed making notably more heat after leaving the 14-16psi bracket, combine that with how restrictive the little turbine housing is and it makes sense very few people have had much success with the stock turbos going that hard. With only quick hits here and there the intercoolers probably do a good job of getting rid of that heat but you'd want a very good intercooler to keep it safe on the track or running up the mountains.

 

I was not looking at x axis at all. I am very well aware that the x axis is flow rate and it is pounds (mass) of air per minute as you state. I was talking about the y-axis not the x-axis.

What I was doing was saying the y axis is approx ratio of air pressure from the turbo to atmospheric. I think you give the correct def (too late at night to understand your bit) but that is essentially what it is (with a minor correction that you state).

So 70% peak efficiency at 2.6 on the y axis (and whatever x-axis flow rate) means (boost + atmospheric) / atmospheric = 2.6

Therefor boost = atmospheric * 2.6 - atmospheric.

As atmospheric = 14.7 psi that means boost = 23.5psi


As you point out its not exactly total turbo pressure divided by atmospheric (there is pressure drops and things) but that the approximation I was using. Does it make that much difference?

Yes I do have massively big intercoolers - had to modify turn signals so they would fit.

 

Fair enough but yeah that correction does make a bit of a difference, changes to atmospheric pressure makes an even bigger one though.
(24+14.7)/14.7 = 2.63 without correction, at sea level
(24+14.7+2)/14.7 = 2.77 with 2psi correction at sea level
(24+13)/13 = 2.85 without correction towards the top of the blue mountains
(24+13+2)/13 = 3.00 with correction towards the top of the blue mountains

I think 2psi is probably fair if not conservative for the design of standard intake pipes, a 2.5" intake kit would help that so if you want to do full intake mods and not leave the coast then 23-24psi is on the map. 18psi seems to stay on the map but you're still seeing diminishing returns once you push past 250kw.

 

Thanks every one for the very informative discussion. Looks like I'll try to push the stockies as far as they go.

If for arguments sake, I was unlucky with my turbos and the wastegates can't hold enough back pressure at high rpm, is it possible to install stronger wastegate springs to keep it closed, or does it not work like that?

If I was stuck with 16psi boost, can you get around that by just switching to e85 and use more timing to make up for the lack of boost?

Lastly, what is this... and can I delete it? (I want to rattle can black the engine bay.)

Coolant over flow bottle if I use a waterless coolant?

This thing that had tubes all connected up to the plenum etc


This thing tucked under the intake pipe.


This cylindrical thing


Factory boost controller? Happy to strip whats not needed when the nistune and EBC is installed.


Any other crap around the EGR that I can chuck in the bin?


Can I get rid of any of these water/etc tubes from under the plenum?


I somehow get the feeling that the Nissan engineers are trolling us when they designed this T.T;

 

I've added comments in the quote for each question.

 

Awesome info! Thanks heaps!

Just by looking at most of these things I could tell they were a waste of space. As of now I pretty much have the whole front end stripped. Intake tubes etc are gone.

Tomorrow I'll make a call to see if I can get replacement intake pipework. Higher flowing maybe? I'll look into BOV springs as well as a silicone tubing upgrade kit. All these rubber hoses are a PITA. The more junk I can get rid of, the easier my life will be when putting it back together... and if I need to do more work on it. Engine bay is way too over crowded its a struggle to even swing a spanner

 

Cheers for the replies guys

Made a solid effort in the last few days. Today I finally managed to finish the egr delete with the motor still in. I swear it has been one of the worst mechanical jobs I have ever done. Just about every bolt was stuck and with zero space. What really had me worried though was the bung on the exhaust manifold. Weird size (21.5mm) and it was seized hard. No room to get an adjustable in there and I didn't have a spanner the right size either... so tried cutting the steel pipe with a dremel, but too thick. Grinder would never fit either, so used a cold chisel to cut the steel tube off and got some heat onto it with a butane torch. 22mm socket was slipping a bit as it was starting to round the hex. With all the leverage of my 1/2" breaker bar and a 1" ring end spanner on the end of that I was very lucky it finally turned but still gave a fight to the bitter end (the last thread).

I here declare the z32 the worst car in the world to work on lol



Also another delete question: there is this solenoid thing that connects to the turbo compressors inlet & outlet and connects to the waste gate actuator. Would this be boost cut? Factory boost control? would an ECB use this or would it become redundant? Its taking up valuable space lol.

 

Knock Sensor

If you want boost & add more timing make sure you replace the Knock Sensor and loom. I would do it for sure because you can bet it will be stuffed anyway.

 

That is indeed the stock boost solenoid (one of two, should be another on the other side), if you're installing an EBC then you want to get rid of these and block the vacuum nipple you can see in the picture, the other hose comes off a T between the intercooler cold pipe beside the radiator (just underneath where pipe to the throttle body connects) and the wastegate.

These diagrams are useful http://z32.wikispaces.com/Vacuum+Diagrams