Star Performance Testing Day – Pt4 N75s

[Ess_Three]

The factual bit:

I spent many hours down at Star Performance yesterday…12 hours in fact (08:45-20:45) having a play…testing a few things, having a load of work done, trying out a few things etc.

Firstly, thanks to Jim & Brian…12 hours and two meals later we were all knackered!
Credit where it’s due…anyone looking for decent service, advice and standard of work could do a lot worse than giving them a shout.

Secondly, none of this was free…labour rates, wheel alignment rates, dyno time, replacement parts…all paid for out of my pocket...I have the invoice for over £900 to prove it!!

Thirdly, these are our (mine, Jim’s and Brian’s) observations based upon our findings. All testing carried out with conditions kept as close to previous conditions as possible etc…some will disagree violently, some will agree…that’s your prerogative.

So, off we go:

Dead simple this one...swap the standard boost control solenoid valve (N75) for one off another model.

I've previously tried the 'H' valve...great on the road but gives 'soft limp' all the time on my car.

This time the 'J' valve...can't compare the results obtained last year with the standard vs 'H' testing for obvuous reasons - different day, different fuel, many parameters.

So, 'J' vs Standard.

Easy...over the runs we did (several) the results are thus:

You get 8BHP @ wheels and 20 lb-ft of torque out of the 'J' N75. Brilliant!
I've not proved if *I* can actually run the 'J' valve on the road yet without hitting limp mode...but it works.

And at about £30 from VAG parts...it's cheap.

The N75 adds about 0.2 bar of boost on my car...hence the 20 lb-ft increase. But it now means I'm running up at just under 1.9 bar peak boost! Scary!

Figures:
Standard N75 average yesterday was 196 BHP @ wheels and 310 lb-ft.
'J' N75 average yesterday was 204 BHP @ wheels and 330+ lb-ft.

forgive me for not posting the dyno graphs...I can't be ***** at the mo...I have them here...I'll maybe get round for it later on.

 

[Grant]

Glen

How did you find your drive home with the N75-J? Did you hit limp mode at anytime?

 

[Ess_Three]

I didn't drive home with it fitted...we ran out of time to log EGTs and mixture etc...it was quarter to 9 at night!!

And the N75 was 'borrowed' of Jim's Bora!...and besides, I never had my laptop with me to reset the faults if they'd come in!
(My N75 hasn't arrived yet!)

So I can't say for sure...In may not even test it...I'm really uncomfortable with running at around 1.9 bar peak boost...I think it's just too much and i'm not convinced the bottom end is capable to holding it.

I'm not concerned about the turbo...if it goes it goes.
I'm more bothered about bending a con rod...or worse!

 

[Mike.M]

I wonder how reliable this would be on a non chipped S3 like mine but with a Samco hose and DV fitted?

 

[RichA3Turbo]

Wonder what my torque is like after fitting my J valve... It definately made a noticable difference, and after 3 weeks of running, not a single problem.

Rich

 

[StephenBogan]

Are we talking about the actuator here folk? Little confused on this.

 

[RichA3Turbo]

No. The boost N75 is the boost pressure regulator... It tells the wastegate when to open/close.

Rich

 

[Ess_Three]

[ QUOTE ]
ScotSTHREE said:
Are we talking about the actuator here folk? Little confused on this.

[/ QUOTE ]

No we are talking about the boost control solenoid valve that bleeds off the pressure to / from the actuator...it's the little metal / black plastic thing that sits next to your DV and has 2 hoses going into / out of it and a third connection going into the turbo inlet hose.

 

[Neal_A3T]

Would this make any difference on a standard A3 Turbo?

Since as most of the people here own chipped A3/S3's, just wondered if it would make any noticable difference on a standard car.

Also would this N75 'J' regulator fit/work on on an A3? or would I need to look at another version?

Cheers

Neal.

 

[Ess_Three]

Any N75 will fit and work on any 1.8T.

But, whether or not it will give you 'soft limp' is the question...it'll surely give you a boost increase...of that there is no doubt.


Just a WARNING!!

N75s add boost...but DO NOT ADJUST FUELING.
It is possible that you can end up running lean using an alternative N75 valve on ANY map, CHIPPED OR NOT!

Beware...to be 100% sure I would want to measure exhaust gas temperatures (EGTs) and mixture under full load to make sure you are not running lean at the higher boost.

I would also suggest logging injector 'on' times...mine are pretty wall maxxed out at the minute...that is to say that they are prety much always on under full load / revs conditions...not ideal.

There are no hard and fast rules for who will jit 'soft limp' either...some will...some won't.

I hit soft limp with the 'H' valve...not sure about the 'J'



As long as people are aware of the damgers associated with taking boost / fuelling out with the control of the ECU...go on my son!


There are many people who will tell you how good this mod is...how much power you'll get etc.

Where will there said same people be if YOU destroy YOUR engine because the N75 mod ran it too close to the edge of the envelope?


Just be wary...the facts are there...make your informed decision based upon what you can find out / know...and go from there.

N75's swaps work. Period.
But at what cost for some people?


I end up with over 330 lb-ft of torque with either the 'H' or 'J' valves...and the car is an animal. To be honest it's easirt to drive quick with the satndard N75 in...wet nights + 330 lb-ft = 4 wheel power slides everywhere.

Great for impressing the little girlies. Crap for quick progress.
Good fun though! /ubbthreads/images/graemlins/grin.gif

 

[Gambba]

Great info Glen, it's so rare to find factual info on these smaller mods, as normal folk tend to do a load of mods and then get it run up....that god you're not normal. /ubbthreads/images/graemlins/beerchug.gif

And this is particularly relevant as recent discussions have been going on about this mod.

 

[RichA3Turbo]

[ QUOTE ]
Neal_A3T said:
Would this make any difference on a standard A3 Turbo?

Since as most of the people here own chipped A3/S3's, just wondered if it would make any noticable difference on a standard car.

Also would this N75 'J' regulator fit/work on on an A3? or would I need to look at another version?

Cheers

Neal.

[/ QUOTE ]

We tested it on my chipped A3 1.8T (AGU 1998), and on a 2001 AUM, and it works well on my car, but didnt work at all well on the AUM engine. Would keep dropping the boost then picking up again up through the revs... Felt terrible. The AUM is now chipped so we will try it again soon.

Rich

 

[Neal_A3T]

Thanks Rich...

Let us know how it performs on the chipped AUM engine.

Mine IIRC is also an AUM, so theres a chance it will do the same... Although still tempted to try it. /ubbthreads/images/graemlins/wink.gif

Neal.

 

[AndybS3]

Ive been looking at the specs for these valves to try and understand the differences, the only difference I can see between the valves is the resistances to check when fault finding. heres the results

Stock F 25-35 Ohms
H 25-45 Ohms
J 20-40 Ohms
Being that these resistances tie in to how the turbo reacts to these different valves could that be how they work, by some kind of variable resistance?

 

[gbhdavies]

I fairly new to this tuning game and very new to this Audi S3 game, but Glens dedication to the cause is very impressive. Top work fella. Does anyone one have a part number for the N75-J as I also have an APR chipped S3 and it looks like a worthwhile investment. Especially based on the comments Glen made about driving his car hard. I'm a bit of a wuss, so hopefully mine won't go limp on me (story of my life)!
Cheers
GBH

 

[Ess_Three]

[ QUOTE ]
Andy bS3 said:
Being that these resistances tie in to how the turbo reacts to these different valves could that be how they work, by some kind of variable resistance?

[/ QUOTE ]

I believe you may be fundamentally correct, but a large difference seems to be all together more simple...I believe different valves have different sized orifices which when conbined with the open / closed signal let differing amounts of air to pass through them.

A smaller orifice combined with the differing electrical reaction you are suggesting seem to do the trick!

 

[Ess_Three]

[ QUOTE ]
GBH said:
I fairly new to this tuning game and very new to this Audi S3 game, but Glens dedication to the cause is very impressive. Top work fella.


[/ QUOTE ]

Cheers! Glad to assist.


[ QUOTE ]

Does anyone one have a part number for the N75-J as I also have an APR chipped S3 and it looks like a worthwhile investment.


[/ QUOTE ]

034 906 283 J

I'm sure the nice chaps as VAG Parts will be able to sort you out for mucho cheapness.


[ QUOTE ]

Especially based on the comments Glen made about driving his car hard. I'm a bit of a wuss, so hopefully mine won't go limp on me (story of my life)!
Cheers
GBH

[/ QUOTE ]

Ah...the opposite in fact!!
Limp mode on mine is hit when taking it easy and allowing peak boost to spool up from low revs...then bang! Limp...no power...VAG Com required.
It's particularly noticable when accelerating under load in 4th, 5th and 6th.

If you hammer it everywhere you'll not hit soft limp as you'll alwaybe above the peak torque point....at least that's how it is for me.


Just remember all about the possible downsides though...

 

[s8n]

I have a APR chip too, but until Ive got a FMIC and its winter here, I dont think ill boost anymore than standard 1.4bar

1.6bar is withing the turbos efficenty but (0.74 efficenty) but if i remember the chart it was like 170,000rpm on the turbo input shaft (dats fffffffassst)

I think the turbo is most efficent at 1.1 bar (0.76 efficent)

 

[gbhdavies]

Again, forgive my ignorance, but is there any way that the fuelling can be controlled in line with the N75 so as to avoid the associated problems highlighted by Glen in his first post..

I'm all for cheap, "REAL" gains, but not overly up for my engine trying to exit stage left through my exhaust. /ubbthreads/images/graemlins/shocked.gif
Cheers
GBH

 

[DavidR]

[ QUOTE ]
GBH said:
Again, forgive my ignorance, but is there any way that the fuelling can be controlled in line with the N75 so as to avoid the associated problems highlighted by Glen in his first post..

[/ QUOTE ]

You could get a custom remap to alter fuelling for the revised valve, but given thats going to cost the thick end of £500 it makes the cheap mod look a litte dubious. Also as pointed out above, the OEM injectors are close to reaching the capacity of their duty cycle, so even with a custom map, you may still not get appropriate fuelling.

 

[Grant]

[ QUOTE ]
GBH said:
Especially based on the comments Glen made about driving his car hard.

[/ QUOTE ]
I was out to see Glen last night to compare S3s, and I can confirm that he does drive his car hard... /ubbthreads/images/graemlins/vomit.gif

I swear to god... I thought we were going to land up in a field as we went round a corner at an unknown speed because I was too petrified to check the speedo! I remember expecting the car to lose grip and head straight for the field, but the car went round the corner like it was on rails!

I have never driven my car to that extremes and personally do not want to - but it sort of gave me a warm feeling knowing that an S3 can be driven that hard and still hold the road.

I drove home quite sedately for a change last night! /ubbthreads/images/graemlins/lol.gif

 

[Ess_Three]

[ QUOTE ]
Imola S3 said:

I was out to see Glen last night to compare S3s, and I can confirm that he does drive his car hard... /ubbthreads/images/graemlins/vomit.gif

I swear to god... I thought we were going to land up in a field as we went round a corner at an unknown speed because I was too petrified to check the speedo! I remember expecting the car to lose grip and head straight for the field, but the car went round the corner like it was on rails!


[/ QUOTE ]

/ubbthreads/images/graemlins/grin.gif /ubbthreads/images/graemlins/grin.gif /ubbthreads/images/graemlins/grin.gif

All in the name of research, you know that don't you?

It wasn't on the edge of grip last night either...you know you've reached that point when you are sitting '**** out' halfway round a bend with all 4 tyres spinning. Nice.


I've completed a few more miles since then...this will bring me nicely on to reports 6, 7 and 8...these will be posted very soon!!

 

[Mike.M]

[ QUOTE ]
Imola S3 said:
I was out to see Glen last night to compare S3s, and I can confirm that he does drive his car hard... /ubbthreads/images/graemlins/vomit.gif
/ubbthreads/images/graemlins/lol.gif

[/ QUOTE ]

/ubbthreads/images/graemlins/laugh_roll.gif /ubbthreads/images/graemlins/laugh_roll.gif /ubbthreads/images/graemlins/laugh_roll.gif /ubbthreads/images/graemlins/laugh_roll.gif /ubbthreads/images/graemlins/laugh_roll.gif /ubbthreads/images/graemlins/laugh_roll.gif /ubbthreads/images/graemlins/laugh_roll.gif

 

[Mike.M]

has to be done once in a while............its what the car was built for............Zooooooommmmmmmmm!!!!

 

[Ryanc]

Just for reference the n75 /j is from the audi s2,here's a link;

http://www.s2central.net/ds_N75.html

hope this helps,Ryan

 

[manueltrigo]

I,ve tried three different N75 in my standard A3 1.8T 180 HP... and seems that works..... F, H and J.
Theoretically it works this way:
The N75 sends orders to the by-pass called waste-gate valve of when and how much it must open to release exhaust gasses, managed by the ECU (by PWD electronic signal), by a vacuum pipe that detected by the waste-gate through a pneumatic membrana/spring open/close the valve.
All the A3/S3 uses model "F", (the waste-gate actuates managed by the N75/ECU to provoke a by-pass releasing the excedent exhaust gasses). Modifying when and how much the waste-gate must open/close you can get different behaviour of the turbo and obviusly different performance.
It depends of the parameters of the N75 (thanks Andy bS3... your data could help me to modify some N75...), the vacuum detected, the PWM signal, and other parameters included in the waste-gate (pneumatic parts, springs, membrana,etc) and obvoiously must be managed by the "big brother" the ECU (different in each model
Due to the different calibration of the N75's you really can vary the performance. And it really works....
¿Safe? ¿Reliable?...... I`ve decide to use them but are not standard parts for the car... so.... yourself!!!! we went to the dyno and checked..... everything

The N75 installed in my car (AJQ-99) is model "F" (audi reference spare is 058906283-F) also installed in most A3/S3.
The N75-H (that belongs to some Audi A4&A6) increases a bit the turbo pressure in my car (180HP; std pressure is 0,75 bar), and really increases a bit the torque/power. Excellent. And mantains the torque over 4.500 as standard. The result is a different torque higher in mid-range and same power over 4.500. Bit better. No problem detected using it and the efficience increased reduced the consumption in normal use. No adjust is needed to install it. The "F" model and "H" model seem to be plenty compatible and can be installed directly to same connections in the car (pressure and vacum in the same position) but the "J" model is different.
"J" increases more the torque in mid-range: in my car, increases a little bit more than "H" the torque , in mid-range, from 2.500 is higher... and excellent, but, IN MY CAR (180 HP), beyond 5.000 rpm, the torque and power decreases a little bit (5 HP) respect H and F... not very significant, even very flat and usefull power up to 6.500 rpm..... incredible and amazing.... I don´t know what could happen in other cars... but read again the theory....the ECU manages a valve that moves the waste-gate trhough the vacuum sent to the pneumatic valve in the waste-gate... and all uses "F" model.... if in my car changes and works.....
But no fuel control is added... so be carefull in S3.
"J" model (Audi spare part is 034906283-J -audi quattro and audi 200- and H is 034906283-H -A4&A6-) changes the position of two pipes so when install the "J" you will install it up side down. It is easy, just detect in the old one witch pipe goes with each hose and check the differences between the pipes in N75 to determine wich goes where.
I`m very happy and satisfied with the "J", more than "H", and "F", although I lost 5 HP at max revs but mid range torque is incredible..... but after several days of use MY ECU HAS AUTOADAPPTED THE MAPPING and lost 15 Nm at 3.000 rev..... Still investigating what happened.... (the ECU is autoreprogramming itself....!!!!) and i´ll post it when test is finished...
All this N75 have different parameters and act different. although are designed and installed in different cars, works in the same way... so different orders are sent to the waste-gate and vary the turbo efficience.... But be carefull; the J (I think is an old model) changes the mid-range torque a lot.... and not sure, yet, what else....

Now, I´m using the "J" model and very satisfied....
More soon....!!!!

 

[mattyboy199]

Anymore info on this subject ?

 

[Stewart]

lol, how much more info do you need?

It's all there, Glen covers it comprehensively.

 

[mattyboy199]

if you read through the thread a couple of people have stated they would advise on further results etc. All i wanna know is if i can run the N75J on my standard bam engine with no problems & still get extra boost.

 

[Stewart]

And if you read through the posts thoroughly (and on other forums) you will realise there is NO definitive answer for your car.
As Glen says, it definitely DOES make a difference but there are too many factors to make an accurate estimation on how it will affect your car...

You can only suck it and see OR get a custom map done with a 'J' valve on but (and Mike at Jabba told me this personally) what is the point in doing that when all he would do is have to pull the map back because of the boost spike that the 'J' gives. He prefers to to use the 'C' valve or the 'F' and produce a more linear boost delivery.

As mentioned time and time again, this is a cheap way of 'possibly' gaining a few more BHP through increasing boost slightly.

Personally, I had a K04 equipped Golf (see my sig) and the 'J' valve produced a much faster spool/ramp up of boost but was quite violent and hit limp condition frequently.

So, again, in conclusion, you will NOT find a definitive answer to your question as it affects different cars in different ways.
As your car is standard I would put the forty odd quid towards a decent remap where you know the map (timing/fuelling/boost) are all at responsible and safer levels.
As Glen also states, there is a danger of running lean with a 'J' especially on chipped cars.

 

[JamS3]

Without Vagcom or putting the car into the dealers is there any way to tell that the car is running too lean or intake temps are too high?

Just don't want to cause damage by doing this mod.

 

[will_b]

If i run this with REVO stage 2 is there any way to increase the mixture setting to compensate as i dont want it to run lean and go bang!!

 

[Ess_Three]

I don't think so...not in certain areas anyway.
You'd need to run it on the dyno and measure mixture and EGT.

If you are running Revo St2, you may not be able to run any different N75 without hitting limp mode anyway...it'll run fine on the dyno...but not on the road, if that's the case.

 

[will_b]

Right i might NOT get it then

 

[M44 DUB]

Guys, if i fitted ones of these from a 225bhp TT and it made my A3 1.8T run limp would i just be able to pop the bonnet and unplug, plug in my new one and drive off again? Or would i need to get the fault cleared on VAGcom?

 

[JamS3]

I ran one of these with a AMD remap on my old 2003 S3 and it was brilliant for a week or so then the car started to hit limp mode all the time.

Beware if you fit these and already have a remap because it could be a waste of money!

 

[M44 DUB]

What about fitting them without a remap? Would it cause major problems?

 

[JamS3]

Not that Iv'e ever heard of, only seems to cause problems when used in conjunction with a remap.

 

[Prawn]

i was about to ask the same question as M44 DUB.

when you say VAG COM required when you hit limp mode Glen, is this to clear fault codes? or is it a form of limp mode which can only be reset using VAG COM?

our tdi A3 used to hit limp mode for no apparent reason seemingly, but it was always fixed by a quick off/on of the ignition. eventually cured with a new MAF.

im having my 1.8T A3 chipped in a month, and am considering fitting the J valve afterwards (i understand its pointless before the map?)

if it hits limp mode, can i just restart the engine and itll be ok? or will i need VAG com to get it running properly again?

 

[Stewart]

They have been used with unchipped/unmapped cars and is considered a cheap and cheerful mod that will give a touch extra performance.

ECS claim their 'Race' valve gives an extra 10hp. I'm dubious of the power claim and most people think this is just the J version.

I've not heard of anyone hitting limp with the J valve on an unmapped car...

Under certain driving conditions I used to hit limp with the J on a Jabba mapped Golf (AGU), as far as I can remember I just carried on driving, it didnt stay in limp mode, it just registered an overboost condition in VAG-COM.