View Full Version : Free mod: faster 0-60
Actual_Ben_Taylor
25-09-2001, 08:15
Anyone want faster acceleration for absolutely sod all cash?
As you probably know the S14 has the boost limited in first and second gears (no boost in first, 0.4bar in second), well I've just found an increadibly easy way to turn this off! All you need to do is look in the engine bay next to the turbo and you'll see a metal solenoid/valve/thingy with 2 hoses coming in/out of it (one reads pressure from the turbo, the other bleeds it off to the inlet). Disconnect these hoses and block them up. Voila, full boost in first and second!
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Black '98 S14
With some mods!
Hmm, I was waiting for someone to try this out. I've also heard of people just disconnecting the wiring from the solendoid - have you tried this ?
Bear in mind the ECU uses this solenoid to limit boost in cases of bad detonation, so you're removing a potentially useful device.
So how much quicker do you reckon it is ?
Tom
Actual_Ben_Taylor
25-09-2001, 11:48
Tried disconnecting the wiring, but it didn't seem to do anything. I'm currently just using the DSBC boost controller to limit the boost to 1 bar, but I'm looking into a way to make the bleed solenoid switchable.
As you can easily hit 60 in second, I reckon it could shave a few tenths off the time. Would also be usefull on the quarter mile (especially if you're using launch control and traction control).
One more thing, are you sure that the ECU uses that soleniod to trigger fuel cut? I know that the S13 doesn't have one, but still has fuel cut...
It sounds like a fun thing to try out, but I'm scared of blowing up my engine or turbo or something. Generally when I try to do something on the cheap (or free..) it goes horribly wrong :O
If it's the "wastegate valve control solenoid valve" as nissan call it, then the ECU definitely varies the duty cycle of this solenoid to limit boost if for example the knock sensor says hello. Although this might be down to poor fuel, it doesn't have anything to do with fuel cut. It's supposed to be governed by engine speed, throttle position, knock sensor, vehicle speed, and boost pressure (if your car has a sensor).
If we take "slow response" to mean low boost and "quick response" to mean higher boost, then according to the service manual. It'll go for lower boost in gears 1-3 IF the speed is under 29mph. Otherwise it'll give full boost.
So by the time you're doing over 30mph in 1st, you should be able to hit full boost (at around 40mph ?).
According to this... the boost limit really shouldn't be much of an issue unless the limit contributes to lag in someway ?
Tom
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1996 Blue/Green S14 (manual)
K&N cone filter
2.5" Tube-torque Cat Back Exhaust.
TechTom MDM-100
Race-Technology AP-22
http://tom.marshall.tripod.com
........... because you'd be pretty lucky to lay down full torque in first anyway. There ya go, a bit of launch control thrown in for free ! And some of you lot are out there paying for it http://300zx.co.uk/200sx/ubb/biggrin.gif
Get the impression an S14 SHOULD be able to hit 30mph in 2s from comparing it with other test results of rwd cars done in places like santa pod (where the tarmac is 90% rubber). Best I've done on my normal private runway officer is 2.4s... which is a little interesting really, because 2.4s to 30 and 6 to 6 would give a very respectable 60 time if only I got to shave that 0.4 off my 0-30 time - the rest follows !? http://300zx.co.uk/200sx/ubb/smile.gif But I digress.
Tom
Actual_Ben_Taylor
26-09-2001, 08:03
Even nailing it up to 5.5k in 2nd I could only get 0.4bar with the solenoid connected. Think I need to look closer at this one, as I know people who've completely removed this solenoid and don't get any problems.
When I got my motor a few years ago I couldn't get above 55 - 58 in second. Then earlier on this year when heading back to see the folks in Wales I fractured on of the turbo inlet pipes. After getting it fixed the car would accelerate well past sixty in second. Now to cut to the chase, after delving under the bonnet last night and disconnecting the solonoid thing I noticed that the jubilee clip holding the rubber hose on to the metal thing bit that eventually fits on to the air filter box was loose. So could it be possible that I'm sucking air from the engine bay by passing the filter and all the restrictions that involves and getting higher boost that way?
Oh yes disconnecting wires didnt seem to make much if any improvement, but I did have big boots on that might have slowed down gear changes. just love the way the front end lifts up when you boot it.
Got blown away by a boy racer in a fiesta van today, shat on my bumper all the way to 95 mpr then I pulled over http://300zx.co.uk/200sx/ubb/frown.gif
Daniel san
26-09-2001, 22:42
Haven't bothered to read all this thread guys but from the bits I have read some of you are on the right track. I was talking to Tony at Abbey about this today (after a 2 1/2 hr train journey to pick my car up!! Ben!! http://300zx.co.uk/200sx/ubb/wink.gif)By removing this solenoid you are taking away the Knock sensor, so if the worst was about to happen, the ECU wouldn't know about it and therefore wouldn't retard the engine at all, so it's a risk you take. They have removed the same thing from some of the Skylines with no problems but although they know exactly what they're doing when you take a 200sx to them, they don't have a lot of experience with them, so they wouldn't like to say that this would be an ok thing to do. Which is hairy muff I spose! http://300zx.co.uk/200sx/ubb/smile.gif
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Dan
www.puresx.co.uk
'98 Saphire Blue S14 (manual of course)
Far too many mods to list here, it takes up far too much space and after being asked very nicely I've decided to shorten the sig (Is that a WOOHOO I hear??)
I, have NO SMELLY TREE, have no plans for a smelly tree and do not want a smelly tree, EVER!!!
Do not take offence to anything I say, even though I probably mean it. I am more than slightly mad, so just chill de feck oooot, ok!
Paul_S13
26-09-2001, 23:24
Boost limiter in 1st and 2nd.......aahhhhhh bless. http://300zx.co.uk/200sx/ubb/tongue.gif http://300zx.co.uk/200sx/ubb/wink.gif
[This message has been edited by paul_s13 (edited 27-09-2001).]
Disconnecting the feed pipes to the solonoid seems a bit drastic to me. The ECU must have sensors on the gearbox to indicate that you are in 1st or 2nd gear, can't these be disconnected?
Actual_Ben_Taylor
29-09-2001, 18:28
Don't know if there are sensors on the box, it could always work it out from speed/revs or something...
As far as I know there's a reverse sensor and a sensor which goes high/low when neutral is selected. Wouldn't be hard for it to work out which gear is engaged from revs, speed and this neutral sensor.
What about what it says in the service manual though ? I'm not at all convinced it's going to make any difference. You need about 4k revs to launch the car in the first place to get anything like a decent time off the mark, you've got to hit 7k revs in first - which is over 29mph - which SHOULD give full boost. A short change to 2nd is going to give a crap time too. You have to redline it in each gear, it's daft not to because the extra torque the gearing gives you is much much more than a bit of boost lost here or there !
Tom
Daniel san
01-10-2001, 20:59
Personally I don't think there's any point in redlining it, cos the max power output is at 6400-6500 (unless you've done some nice mods inc a set of new cams http://300zx.co.uk/200sx/ubb/biggrin.gif). If you rev it right into the red then the power band just drops off. I think about 6700-6800 is about right.
Oh, and yes, you do need about 4K to launch. which is exactly what my Launch Control is set to http://300zx.co.uk/200sx/ubb/biggrin.gif
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Dan
www.puresx.co.uk
'98 Saphire Blue S14 (manual of course)
Far too many mods to list here, it takes up far too much space and after being asked very nicely I've decided to shorten the sig (Is that a WOOHOO I hear??)
I, have NO SMELLY TREE, have no plans for a smelly tree and do not want a smelly tree, EVER!!!
Do not take offence to anything I say, even though I probably mean it. I am more than slightly mad, so just chill de feck oooot, ok!
Dan,
I see what you're saying, but even if the power does drop off, you might find that there's still more torque at the wheels in the lower gear than you get from changing to the next one !
But if we're just talking the difference between 6k8 and 7k then.. well.. I agree it isn't going to make a huge amount of difference http://300zx.co.uk/200sx/ubb/smile.gif
Tom
JonnyBoy
02-10-2001, 09:02
Im not the brightest tool in the box when it comes to mechanics, but just wondering - you say boost is limited in 2nd, is that a fixed amnount or if you put a bigger turbo in will you get a proportional increase in boost in 2nd gear?
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Nearly there, nearly there ....
Heh?
The knock sensor (if anything like the S13) is fitted to the block!
This is a boost limiting device that Ben is talking about.
I would have thought that if you remove this all your doing is removing the ECU's ability to restrict the boost for "limp home" mode. I think the ECU would still retard the timing though - same as on the S13.
Matt
Yeah, but the knock sensor has nothing to do with the boost limit in lower gears. True, the knock sensor will limit boost too (in all gears I think), but as you say only for "limp home" mode.
Why would you be in 2nd gear under 29mph ? It does say in the service manual the boost limit is ONLY active under 29mph.
Seriously, as far as I can make out if you're doing a sprint up the road you'd definitely be in 1st gear under 29mph and it would be doubtful if you could get full power down in any case.
I suppose if you have to slow right down for a corner it's a pain in the arse to ram it into 1st, and a 2nd gear exit wouldn't be as quick as it could be.
I'll have to test this, maybe the service manual is wrong or misleading, unless I'm missing the point.
Tom
Has anyone actually done this mod on a standard s14a, and is there any noticable improvement, or indeed problem like putting down the power?
Originally posted by Ben:
Has anyone actually done this mod on a standard s14a, and is there any noticable improvement, or indeed problem like putting down the power?
Me .... I dunnit ! ..... with permission from ND
What happened was I upped the boost to 17psi got a FMIC and the boost suddenly started fluctuating ALL over the place 14-13-17-18-14-15- ... wouldnt stay still, turned out to be, that solenoid was shagged, so had it completely removed and now controll the boost totally off the actuator.
Made a difference ???
I get a little more boost in 1st and second, but not that much as the gearing is very low and thus puts no real load on the car to be able to build the boost up, you dont get a chance to get to full boost before you change gear.
The only difference is it has made is the car seem a little more responsive in all gears, seems the boost comes on a little quicker.
all though I was driving around with the problem for 3 months, this new responsiveness may be imaginary.
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'97 S14a Manual
K&N pod, Mongoose, HKS FMIC, Eibach springs, uprated disks &pads, boost 17psi. ND dump valve, Giant pigeon wastegate noise
Ahh .. re-read your post "STANDARD S14a" ... erm nope ... I dunnit on a modded one.
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'97 S14a Manual
K&N pod, Mongoose, HKS FMIC, Eibach springs, uprated disks &pads, boost 17psi. ND dump valve, Giant pigeon wastegate noise
wouldn't a replacement hi-flow IC be pretty stealthy.
Once it gets crudded up who'd know it wasn't the original. Would the car be checked to that detail after a crash?
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Emerald S14a
I HATE SEAGULLS!!
Please ignore the above it was meant to be a reply to the insurance invisable post (only had 1 bottle of Becks!)
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Emerald S14a
I HATE SEAGULLS!!
It's not a particularly common car is it ? I'd doubt they could tell the difference.
Tom
Nick_Walczak
08-10-2001, 11:58
Originally posted by Dai D:
Please ignore the above it was meant to be a reply to the insurance invisable post (only had 1 bottle of Becks!)
Yeah, I don't know what difference it would make though. I thought that the reason you fitted the improved IC was to remove the bottleneck that prevents you from dialing the boost up over 15psi. So without a boost upgrade it prolly won't do that much.
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