Maximum boost on unleaded / super?

[Nick_Walczak]

What is the maximum boost achievable on a S14 without lowering the compression ratio? On unleaded and on super unleaded?

I just wonder why the manufacturer limits the boost to 10psi when you could crank it up higher without any problems...?

[Bean]

I believe Tom bought this point up recently, from the compression ratio on the S14 it doesn't look wise to increase the boost much.

Has someone got a way of calculating this?



------------------
Red 1995/S14
K&N, Private Plate

Any views expressed in this message are based solely on personal opinion.

[Nick_Walczak]

Well the ND website talks about merrily cranking up the boost to 15psi without any problems. It doesn't mention using octane boosters or anything. Confused now http://300zx.co.uk/200sx/ubb/frown.gif

[Daniel san]

It's safe to raise the boost to 15psi and still use normal 95octane.

Personally, I wouldn't be happy running it much higher than that anyway and I think others would agree...(Ben??).

But if you've got some nice HKS forged pistons........Damn I need my boost controller in NOW!!

------------------
Dan
www.puresx.co.uk

'98 Saphire Blue S14 (manual of course)
Blitz Induction
Blitz Dump valve
Blitz Exhaust
Blitz MSTT
No CAT
30mm Drop
Skyline style front spoiler
18" Kosie Snipers
Racelogic Adjustable Traction Control
Launch Control
Full Throttle Shift
Clear Indicators
Several MELTED Spark Plugs, resulting in
HKS Forged Pistons
HKS 1.2mm Metal Head Gasket
Trust Iridium Spark Plugs
Done me 1000 miles, now just waiting for Abbey to give me the go ahead before I drop the hammer again!
Credit cards would be more popular if you didn't have to pay the bill every month!
Do not take offence to anything I might say, I am completely mad. So jus chill de feck oooot, ok!

[Nick_Walczak]

Dan - do your pistons lower the CR? Not cheap, I imagine... http://300zx.co.uk/200sx/ubb/eek.gif

[Daniel san]

in conjunction with the 1.2mm gasket, yeah they do and no, they aint cheap.

------------------
Dan
www.puresx.co.uk

'98 Saphire Blue S14 (manual of course)
Blitz Induction
Blitz Dump valve
Blitz Exhaust
Blitz MSTT
No CAT
30mm Drop
Skyline style front spoiler
18" Kosie Snipers
Racelogic Adjustable Traction Control
Launch Control
Full Throttle Shift
Clear Indicators
Several MELTED Spark Plugs, resulting in
HKS Forged Pistons
HKS 1.2mm Metal Head Gasket
Trust Iridium Spark Plugs
Done me 1000 miles, now just waiting for Abbey to give me the go ahead before I drop the hammer again!
Credit cards would be more popular if you didn't have to pay the bill every month!
Do not take offence to anything I might say, I am completely mad. So jus chill de feck oooot, ok!

[Tom_S14]

Hi,
Yeah, this octane thing has had me puzzled for a while really.
There's a quite well respected turbo outfit in australia run by Ray Hall. He's got some java calculators on his site for working out this kind of thing... let me see now... http://www.turbofast.com.au/TFcompB.html
give that a go... I typed in some numbers after converting to imperial http://300zx.co.uk/200sx/ubb/frown.gif save you some time here they are, 75% V.E. (reasonable guess ?)
0.5 Bar (7.5psi) std 197bhp 94Octane
0.7 Bar (10psi) 218bhp 97 Octane (Super UL ?)
1 Bar (15psi) 260bhp 103 Octane (Space shuttle fuel ?)

I was encouraged by this because it gave the exact stock power output for standard boost. More luck with the V.E guess than anything though http://300zx.co.uk/200sx/ubb/smile.gif
Water injection seems a good way forward on this one.

Tom

[Nick_Walczak]

Tom, I thought stock boost was 10psi? Maybe you could tweak VE until you get 197hp @ 10psi and then see what the figures would be. I would expect about 230hp @ 15psi...

[Tom_S14]

Well, I know it says on the ND site that stock boost is 10psi, but my understanding was that this is a mistake !
My boost gauge shows 0.6bar peak boost guages sometimes, but is obviously set up to mantain 0.5bar continuous. I think the S13 runs 10psi standard, not the S14. I'm sure I've read this somewhere too...
Or maybe my boost guage is a bit crap ?

Tom

[Daniel san]

The S14 does run 10psi standard.

------------------
Dan
www.puresx.co.uk

'98 Saphire Blue S14 (manual of course)
Blitz Induction
Blitz Dump valve
Blitz Exhaust
Blitz MSTT
No CAT
30mm Drop
Skyline style front spoiler
18" Kosie Snipers
Racelogic Adjustable Traction Control
Launch Control
Full Throttle Shift
Clear Indicators
Several MELTED Spark Plugs, resulting in
HKS Forged Pistons
HKS 1.2mm Metal Head Gasket
Trust Iridium Spark Plugs
Done me 1000 miles, now just waiting for Abbey to give me the go ahead before I drop the hammer again!
Credit cards would be more popular if you didn't have to pay the bill every month!
Do not take offence to anything I might say, I am completely mad. So jus chill de feck oooot, ok!

[Tom_S14]

Hmm, well I'll get a new boost guage. It does indicate negative pressure with the engine off, and it was a tad on the cheapo side. I've definitely read it runs 0.5 bar though.
I'd be suprised if the VE of the S14 engine was much under 75% - 16v engines these days shouldn't really be much less.
One thing I've been told is that engines rarely achieve the theoretical compression ratio in practise due to less than optimum "cylinder filling" - but with a turbo charged engine, I can't really understand how this holds up ?

Tom

[Actual_Ben_Taylor]

S14 does run 0.7bar. It'll hold 0.5 happily until you push it over 6+k, then it'll peak at 0.7.
The factory boost cut is apparently set at about 1.3bar.

Ben

------------------
http://forums.evilnet.net/ubb/smilies/pc1.gif
Black '98 S14

[Nick_Walczak]

Tom what input figures did you use for the Java applet? I'd like to give it a go. It did say something about how VE was lower at high rpm (ie: where we are measuring peak power)

[Tom_S14]

Hi,
The stroke and bore are 86mm each - 3.38" ?
rpm I set to 7000, optimistic - maybe peak power would be more like 6500 standard ? 4 cylinders http://300zx.co.uk/200sx/ubb/smile.gif Intercooler efficiency I set to 75% too... comes out not far off 197bhp. Ambient didn't seem to make much difference, as you'd expect compared to the massive temp increase you get from compressing the air. I put in 20.
It's quite good, it gives the likely temp after the intercooler and stuff - quite interesting.

Tom

[Nick_Walczak]

Yup, seems very accurate.

My initial parameters @10psi gave me 201 hp. 14psi (typical initial boost upgrade) gives 230ish. 18psi (max with new intercooler) gives 260.

These figures are be consistent with ND's claims for their ND240 and ND270 packages if you assume that the extra 10hp is got from the filter and zorst (most expensive bits!)

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http://members.home.nl/spawnagain/toohappy.gif Hi!

[Tom_S14]

Yeah, it's not bad is it ? There's a more detailed power output one here http://www.turbofast.com.au/tfcalc.html which is worth trying. Thing is now, what anout the octane issue ? I can't understand how normal 95 octane unleaded is good enough for higher boost pressures ! If the V.E or compression drops off loads at high revs, it wouldn't cause detonation, but then you wouldn't get the power output either !
Bit concerned as my S14 has clocked up 110k miles now, still going very strong, no problems at all and I'd like to keep it that way http://300zx.co.uk/200sx/ubb/smile.gif

tom

[Nick_Walczak]

Umm, I only used the power output one, I didn't consider octane... I don't know really, ND website says unleaded is fine at 15psi. I hope so.

[Bean]

If and when I up the Boost on my S14 I'll run Superunleaded to avoid engine problems.

The only problem is that it's 10p more per litre, but if you afford the car you should be able to afford the petrol!

I suppose?

------------------
Red 1995/S14
K&N, Private Plate

Any views expressed in this message are based solely on personal opinion.

[Tom_S14]

I sometimes tell myself this... but I can only just afford to run the car. I'd love to find a cheap plentiful source of toluene or something to pour down the tank...

Might be worth working out how much extra you'd pay in fuel running super unleaded for the next 5 years (assuming price difference stays roughly constant) - in comparison to forking out some dosh to get water injection fitted ? I think it would probably just come out in favour of water injection myself.

The other thing is...how well can the stock intercooler cope with higher boost pressures ? According to ND, 15psi is right on the margin.

Tom

[kerfumph]

10p more a litre? at esso its 2p more!

------------------
Graham
90' s13
Trust me, I know everything.

[Nick_Walczak]

Originally posted by Tom_S14:

The other thing is...how well can the stock intercooler cope with higher boost pressures ? According to ND, 15psi is right on the margin.

Tom

Have a read of the intercooler page on ND website. It says that the stock intercooler causes internal pressure loss which is the limiting factor @ 15psi. If you get a replacement wing mounter IC, you can get 17psi. The extra cooling gives you more than just a pressure increase too. On that Java applet, it would be an increase in the internal efficiency of the IC. Front mounts are only necessary for 300+bhp.

[Daniel san]

Front mounted ic needed then I reckon http://300zx.co.uk/200sx/ubb/smile.gif http://300zx.co.uk/200sx/ubb/smile.gif

------------------
Dan
www.puresx.co.uk

'98 Saphire Blue S14 (manual of course)
Blitz Induction
Blitz Dump valve
Blitz Exhaust
Blitz MSTT
No CAT
30mm Drop
Skyline style front spoiler
18" Kosie Snipers
Racelogic Adjustable Traction Control (For Girlies my ARSE, there's no denying it anymore. Give in to temptation. Give in to your desire, you know you want to. You know you want it. You can't live without it. You must have it NOW NOW NOW. AAAAAARRRRGGGGGHHHH!!!!)
Launch Control
Full Throttle Shift
Clear Indicators
Several MELTED Spark Plugs, resulting in
HKS Forged Pistons
HKS 1.2mm Metal Head Gasket
HKS Super AFR
NEW Lambda sensor due to old one being more than ****ed!
Trust Iridium Spark Plugs
Done me 1000 miles, taken it to Abbey, got it back from Abbey, now got less than no money in my bank account and the guys at the credit card co still reckon I should pay them each month! What's that all about then eh???
Credit cards would be more popular if you didn't have to pay the bill every month!
Do not take offence to anything I might say, I am completely mad. So jus chill de feck oooot, ok!