Maximum boost to run with my set up?

[Calgary280ZT]

Hey guys. Well, I'm finally getting my Wolf V500 dialed in. Next step is to turn up the boost. You can see in my sig all the mods I've made. Even at its current 10 psi it pulls hard. Haven't had it on a dyno yet, but JimCanuck and I estimate torque at 300+ ft lbs., hp probably in same range.

 

The other mechanic who works on the car with me is a Nissan trained tech who is the 300zx TT guy to go to in Calgary. When I told him I wanted to turn the boost up to 15 lbs, he recommended against it, saying 12.5-13 is all the L28 can really handle. I know ktm and bernardd and other are running way more than that on a stock bottom end (which is what I've got), but this is my daily driver and reliability is also important.

 

When I built the car I took TonyD's advice and started my mods by improving the engine's breathing as much as I could within my budget. You can see the IC, Rebello head, Isky and Lonewolf ported intake. With all that work it should be able to handle more boost pretty easily, right?

 

I know this issue has been dealt with in the archives, but I wanted members' opinion on my specific set up. What do you think guys? 12.5 vs 15 lbs of boost, which one would you go with?

 

Oh, and my block is low mileage (around 100k) and in pretty good shape.

[softopz]

I think you can run up to 2o psi its all the tune , boost doesnt kill detonation kills. With a decent tune you should and can run 15 lbs no problem again its all in the tune. Anything over 17 I would run methanol for more cooling and and increase in octane will run more cleaner too. Have you shaved or decked block and head? If this has been done numerous times I would not recommend going over 13 psi all depends on your compression. Good luck. Happy boosting

[S130Z]

I run 15psi all day long on my daily driver ZX. What turbo are you running? You need to figure out what your turbo can flow to help you get a better idea of when it starts to blow hot air.

[johnc]

Why focus on a psi number? I just don't understand turbo guys focusing on a specific psi. Tune the engine and the boost pressure together to get the most performance while keeping the engine out of detonation. It doesn't matter if the boost psi number is 10 or 20, your engine will perform the best at some combination of tune and boost pressure. Turing the boost up or down from that optimal setting to achieve some Internet Approved number is foolish.

 

Tune the frickin' engine!

[Calgary280ZT]

softtopz: to the best of my knowledge, the head has not been shaved. I know the block is bone stock. We're working on the assumption that the cr is the stock 7.4:1.

 

s130z: turbo is a T3/T4E. I assume .50 trim but can't confirm it because I bought it from a member here and although he never installed it, he couldn't remember the specs.

 

johnc: ....lol. Message received loud and clear. I started with a base tune from ktm and I've had a couple of members (inc. bernardd) tell me the timing table is pretty conservative. Thus far I've concentrated my tuning efforts on the bottom part of the fuel map in order to increase off-boost driveability and mileage. Last week on a 700 mile trip from Calgary to White Rock I got between 20 and 26 mpg, car ran strong in the mountains...pulled the plugs the next day and they were nice and toasty brown, didn't look too lean. Having trouble logging at the moment (either wideband is dead or a problem with the aux box), so plan to put the car on the dyno next week and start tuning under boost. Plan to go nice and slow and avoid blowing up stuff.

 

Thanks guys. Plan is still to go with 15 lbs boost, will report back on how the tuning goes.

[Tony D]

I second John C's comments.

 

It's not the PSI, it's wether or not you are satisfied with the performance you are getting.

 

Do you want MORE power? If so, turn up the boost.

 

If not, leave it alone.

 

My bet is that at 10psi you are now making more than most with a stock turbo and 15psi. I forget which turbo you ended up using, but rest assured you are making far more horsepower than you think you are.

 

Boost is like Horsepower: People get fixated on a number and end up doing stoopid crap.

 

I'd concentrate on really getting tuning proper, and figuring out if everything else you have is up to the power you are making...or think you will be making.

 

My thoughts are that you are dangerously close to overwhelming the power capability of the S30 in race trim. Guys with 450+ hp on an S30 aren't using that power in a corner...and in most cases it's sketchy to use in a straight line.

 

Like I said at the beginning, I had all these delusions when I built my first turbo car. had the adjustable boost controller with infinite adjustments and all that crap. Long and short of it I ended up running it in one of two boost pressures. 10psi for everyday commuting, and 17psi for when I had to run away from something fast.

 

160mph in a street height Z-Car is moving. 17psi will get you there. Fast.

 

You may want to consider what you really want, or WHY you are looking for more boost. To say you're running it? Do you really feel the need to have it? Is the car underperforming in some aspect?

[Calgary280ZT]

Tony, your vote for getting the tune right is noted...working on it, will report back. But you've raised a couple of questions worth considering.

 

1. Why do I want more power? For the same reason every boost addict wants more...I've become used to 300ish hp, I think I can handle the power and I want to try more. After all, I took your advice when I started this project...the engine can breathe pretty damn well, now I want to try more boost and see how I like it. Do I REALLY need it? No. This is the car I drive up to clients' office in or up to a news shoot. It's my DD. But would I like a little more oomph when I pull up beside one of those German cars on the Deerfoot? You bet.

 

2. Can my build handle more boost? There may be some weak areas, I think. I'm not 100% confident in my Chinese IC (so far my IAT are in the 26-30C range, which I gather from posts is pretty good under boost). I think I have pretty good control of fuel, but not so sure about spark.

 

3. Can the car handle more power? This is an area that needs some work. I'm running the stock suspension with KYB shocks and poly bushings. I'm pretty careful about not pushing it too hard around those Rocky Mountain corners. JimCanuck's 73 is my benchmark and he is soooo far ahead of me. So that is my 2011 project. What do you think about stiffening the chassis with some Bad Dog rails?

[Lazeum]

Regarding turbos & boost, I would try to find the compressor map of your turbo and get the boost were it should be to get the most of your turbo (injectors, IC & fuel system should follow as well obviously)

 

Then, I'll get the ignition tuned up properly with a close eye (or ear!!) on detonation, ignition is where you'll find the most of the power. For this matter, I've made a DIY detcan for less than $15.

 

A dyno session or some pulls on highway ramps & some steady states log sessions with a friend to help would do the trick.

 

 

[LoneStarS30Z]

I'd like to ask a question too since it relates with the OP's original concern.

 

I base how much PSI my high and low settings are based on my narrowband air/fuel ratio gauge and on my injector duty cycle reading on my SDS.

 

I've run my Profec B's setting to 100% and had a buddy watch my the SDS controller's readings while I paid attention to the reading from the A/F gauge. The duty cycle never ran over 80% and the narrowband's reading stayed in the green. I can't remember off the top of my head how much PSI that was as its been a while since I've driven the car. The turbo is a T3/4 with a 60ar inlet and 64ar outlet.

 

Bottom line though, how "safe" is this way of measuring if that's a safe setting?

 

Getting it professionally tuned is one of the things on the long to-do list, but I just wanted make sure my train of thinking isn't wrong.

Edited September 5, 2010 by LoneStarS30Z

[Tony D]

I think it's time for suspension work to handle it and keep it stuck to the ground, personally.

 

I don't recall the cam specs but cast pistons will limit you to 7K and that means boost is your rout to HP unfortunately.

 

Running the compressor within it's map at 8psi and running to 8000rpms will give you a nice bump in horsepower if set up right. And will not be your 'typical boosted car feel'...

 

Breathing helps all around performance, but when you're saddled with cast pistons boost is the only answer.

 

Also remember my other thoughts on the subject: I ran my car for well over 40K miles with NARY A PROBLEM.

 

I ACCEPTED a performance level which retained my 100,000+ mile reliability. I have not gone through a single head gasket since boosting.

 

If you refuse to ACCEPT a REASONABLE performance level for the money put into the engine....

 

Expect to spend a lot more money in short order. Remember my corollary about a stock bottom end: "WHEN you blow it up learning how to tune your system, your replacement is cheap and you need a core to build the GOOD engine anyway."

 

You are now stepping into the 'core production' realm. Have a second short block ready to put in there. Tune away. Hopefully you will 'get it right' at the higher boost on only one block, leaving you golden to build one for higher RPMS and more power at the same level of boost that you finally settle upon.

 

Me, I was happy with 10/17 on a switch. I still am. Anything more than that and it's getting expensive to build bottom ends for longevity. Remember what was made at 9 and realize you will need 300# of ballast or some WIDE STICKY tires to actually USE the hp that will let you accelerate from 70 to 120 in less than 4 seconds (if you don't light them up and slow down, that is!)

[Tony D]

Also, for those recommending on-road testing...

 

Forgetaboutit!

 

The on-boost response has to be tuned in the on-boost, on-load range. In 4th gear than means as mentioned above, dashes from 70 to 120mph.

 

Thats what for our Canadian Friends? 120 to 200 kph?

 

I'm sure the RCMP will TOTALLY understand your need to 'get the tune right' and exceed the speed limits in that range.

 

Add to that, watching for the errant moose or other wildlife doesn't lend itself to a concentration on the gauges (which is where it should be doing this tuning!)

 

You won't do it alone. And who will you find to saddle up and strap in while you blast from 70-120 repeatedly....who is competent with the system to do the tuning?

 

A dyno, for Turbos at this level, is really the only practical alternative. The road ceases to be at around 8-10 psi.

[Lazeum]

Even it is "possible" to do it on the road, I agree with Tony, best solution is a dyno  

[roger280zx]

Why focus on a psi number? I just don't understand turbo guys focusing on a specific psi. Tune the engine and the boost pressure together to get the most performance while keeping the engine out of detonation. It doesn't matter if the boost psi number is 10 or 20, your engine will perform the best at some combination of tune and boost pressure. Turing the boost up or down from that optimal setting to achieve some Internet Approved number is foolish.

 

Tune the frickin' engine!

As usual good sound engine advice from a guy who says "I'm not an engine guy". As Johnc and others have said, turbo engines are all about the tune. Keep the AFR right, the air cool, and detonation at bay. Other variables (like boost pressure) are just that, variables. Power is in the TUNE. Longevity is in the TUNE. Economy is in the TUNE. Take your time boosting it up and it should be a very fun engine for a long time.

[Zmanco]

I'll add 2 comments:

 

1) at the last track day I limited MAP to 1.5 bar and had a blast at the track. Any more than that and my skills as a driver would not keep up. My suspension is more track oriented than yours and yet I still don't have stiff enough springs nor enough caster/camber to fully use the power I made. I did have a fun run with some LS2 GTOs where I was dead even with them in the straights and all over their butts in the corners. Candidly, the car is more fun to drive at this power level.

 

2) if you haven't already added a knock sensor, you need to before turning things up further. I added a knocksense module using the stock factory 280zxt sensor and was surprised to find spots where I was getting detonation and could not hear it at all. Tuning for detonation with our ears is just not a safe way to do it, especially as you turn the boost up.

[Lazeum]

After some discussions with some skilled tuners, it appears an independant knock sensor is a "must have".

 

On Silvias with SR20det (my DD), knock sensor is very inefficient so relying on stock system is a mistake. Thus, I have made my own based on tuners input. I did not have the opportunity to try it yet but this solution seems to be one of the most reliable.

Electronic versions have to filter signals to extract knock from white noise. Being an NVH engineer, I know it is not an easy task. It is perfectly doable but it requires some time and skills (=$$$ for final customer) from manufacturers. The filtering can be done naturally with your ears on mechanical versions (I once found on youtube some clip of knock to ear it)

 

[Tony D]

Rather than the Peltor 'hose snorkel sthescope' approach, has anybody outside of me and Dan investigated the conversion of the VW Piezieoelectric knock sensors to headphones for knowkc monitoring when tuning?

 

All the guys at the TurboMopars forum seem to think this is "The Duck's Guts" and it really helps with amplicifation and picking up of the knock signature while on-boost.

 

Sorry I don't have a link, but the thread I read there seemed to me to be the way to go: electronic ears with variable amplification via any conventional circuitry. Apparently the VW sensor will work as a 'microphone' and is very high resolution when listening for knock in these situations.

 

I have used the garden hose earphones, and they work well, but an electronic microphone tuned for this duty seems it's a no-brainer to use in the application!

[Zmanco]

I'm running this KnockSense with the factory piezo sensor and so far it's worked well. It does pick up some false positives above 6500 rpm now and then, but other than that, it has helped me find spots under partial boost where there was detonation that I didn't hear. For less than $100 (closer to $50 if you use an existing sensor), it's cheap insurance. If you're running megasquirt, the knocksense output can be datalogged, as well as be used to retard timing on the fly.