# Raising boost manually, N75 delete questions...



## URIN 2ND (Oct 29, 2001)

Hey gang,

First off - adult owner here, not new to turbocharging - but I AM new to the 1.8T! I've read a few threads, and I'm trying to get a clear answer.

New-to-me Mk2 w/ an early 1.8T swap. All stock. As I've done on several other brands of vehicles that use a solenoid to control wastegate pressure, the first mod I am planning to do is to *bypass the boost control solenoid* (you call them N75's here) and *run directly off the wastegate for boost pressure*, adjusting the rod to approximately 11-12psi. This is how pretty much all turbo cars controlled boost in the 70's and 80's before electronic solenoids. I'm not crazy. 

On other cars I'm familiar with, you leave the "N75" connector plugged in, but bypass the vacuum lines, connecting the compressor directly to the wastegate. This keeps the ECU happy. Then, you adjust the wastegate rod to your desired boost pressure, being careful not to run more boost than your fuel system can handle (or so much that you trigger limp mode from overboost on a stock ECU).

My question is two-fold:

1) I've read a few threads suggesting this will work just fine to gain a couple PSI before deciding on the right tune, but can anyone here confirm with 100% certainty?

2) What's the maximum boost pressure I can plan to run before the ECU hits limp mode from overboosting? I understand ~8.9psi is the factory pressure...would 12psi be a fair goal?

Any info is appreciated. Thanks in advance! :wave:


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## ExtremeVR6 (Sep 6, 2001)

I'm imagining you're talking about an AEB that was swapped in. That's good, AEB's (that are drive by cable) handle not using the n75 better than the drive by wire cars (later 1.8ts). With that said, I'd recommend leaving the n75 plugged in, but not installed in the intake pipe. Instead, put the relief side of a MBC in its place. Since fueling, spark timing, etc are all based off of the signal from the mass air flow, it important to retain as much of the metered air as possible. 

Additionally, if you leave the n75 in place but without any boost/vac lines going to it, you are leaving a potential inlet for additional air intake, after the MAF sensor, which will screw with your air/fuel mixture from idle to WOT and back again. 

Now, to your questions. 1: yes you CAN use a MBC to get a few extra psi from the system, of them all AEB handles that the easiest. However, 12psi is the max before the system puts things in lock down due to "overboosting". Since the stock turbo is so small, it is very prone to spiking before settling to the specified boost. If you use the MBC to raise it to say 10psi and you end up spiking to 13... You'll quickly end up in limp mode. In which case the n75 stays open and you end up running strictly off of wastegate pressure which is typically somewhere between 4-6psi dependent on how fresh/worn your wastegate is. 

I think I ended up answering both questions at once... 1: yes it will definitely work. 2: the max I would do would be 10, bc of the aforementioned possible boost spikes. It is worth mentioning that if your MBC is quick enough/good enough, you could possibly run 11psi as it would vent it back into the intake before the spike would happen... Maybe. 


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## 04v-dubGLI (Sep 29, 2011)

Mk2 with a 1.8t swap sounds awesome.
1) you will most likely throw it into limp mode right away.
2)you should really just leave thr n75 ajs get the ecu tuned (remapped) so fueling and everything is adjusted. That would be the best way to increase boost to 20+ lbs safely without throwing it into limp mode 

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## ExtremeVR6 (Sep 6, 2001)

Oh and adjusting the wastegate rod is typically done when someone is trying to maintain higher boost levels, like 20+. So they'll "crank" the wastegate by tightening he adjustment nuts so that there is more preload on the actuator. 

Ultimately, you'd be much better served by picking up a stage 1 tune. That'd put you at about 15psi and you wouldn't really need to do any other mods.


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## URIN 2ND (Oct 29, 2001)

ExtremeVR6 said:


> I'm imagining you're talking about an AEB that was swapped in. That's good, AEB's (that are drive by cable) handle not using the n75 better than the drive by wire cars (later 1.8ts). With that said, I'd recommend leaving the n75 plugged in, but not installed in the intake pipe. Instead, put the relief side of a MBC in its place. Since fueling, spark timing, etc are all based off of the signal from the mass air flow, it important to retain as much of the metered air as possible.
> 
> Additionally, if you leave the n75 in place but without any boost/vac lines going to it, you are leaving a potential inlet for additional air intake, after the MAF sensor, which will screw with your air/fuel mixture from idle to WOT and back again.
> 
> ...


Awesome, thank you.

With the stock ~8psi wastegate actuators on the Mitsubishi turbos I'm used to, you can adjust them to as much as 20psi reliably. You simply screw the rod in as far as it will go, usually requiring you to pull pretty hard on the rod to get it back on to the wastegate flapper arm. I always found mechanical boost control superior to electronic boost control, simply because electronic control always seems to have issues and feels "different" from day to day, whereas the mechanical setup was always more consistent (for me).

That's why my first choice is to NOT use the N75 solenoid to regulate boost, and instead use the wastegate actuator directly. This also eliminates the need for a MBC. It takes a few extra seconds to adjust, but I usually set it and forget it. At any rate, I'll try both methods and see how she does.

Thank you again! :wave:


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## URIN 2ND (Oct 29, 2001)

ExtremeVR6 said:


> Oh and adjusting the wastegate rod is typically done when someone is trying to maintain higher boost levels, like 20+. So they'll "crank" the wastegate by tightening he adjustment nuts so that there is more preload on the actuator.
> 
> Ultimately, you'd be much better served by picking up a stage 1 tune. That'd put you at about 15psi and you wouldn't really need to do any other mods.
> 
> ...


I will do this eventually. Just curious about cheap/free stuff I can do over a weekend for the time being. No smog here also, and I've read about people deleting the N249 and such. The cat will also be tossed. It's just a weekend/track build. And while I don't want the FWD overpowered (I've had spin-monsters and too much power actually gets boring), I will want a little more eventually.

I'm probably going to go for around 2200 lbs curb and 220 crank HP. Should be fun without being useless. lol.


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## ExtremeVR6 (Sep 6, 2001)

No problem... I'm not sure how accessible the wastegate is on the mitsu cars... But on my Audi I can get to the wastegate without taking the turbo off. 

I can appreciate going that route, and honestly, without the n75 in place, you are free to run what ever you like now that I think on it... It's the later ones that freak out more. However, this does put you in a precarious situation where other systems and preventative measures can't work because the n75 isn't there. For example, if your MAF sensor goes out and if throwing wonky numbers to the ecu... Your cranked wastegate will be letting the turbo push up to 20psi... Meanwhile the fueling is running itself light because the MAF is saying there's only 150g/min going in, when in reality it's more like 250g/min... Hello melted piston. I prefer to let the ecu do its work and ruin my fun if something is going wrong... But that's just me.


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## URIN 2ND (Oct 29, 2001)

04v-dubGLI said:


> Mk2 with a 1.8t swap sounds awesome.
> 1) you will most likely throw it into limp mode right away.
> 2)you should really just leave thr n75 ajs get the ecu tuned (remapped) so fueling and everything is adjusted. That would be the best way to increase boost to 20+ lbs safely without throwing it into limp mode
> 
> Sent from my SAMSUNG-SM-G900A using Tapatalk


I guess it has good potential, but in stock form, it's really not all that impressive. A VR6 swap is most certainly faster. 2,500 lbs and 150hp...any Civic hatch with a B16 swap would kill it. Badly. But, a little bit of weight loss, and a couple bolt-ons, and it should be plenty of fun.


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## ExtremeVR6 (Sep 6, 2001)

URIN 2ND said:


> I will do this eventually. Just curious about cheap/free stuff I can do over a weekend for the time being. No smog here also, and I've read about people deleting the N249 and such. The cat will also be tossed. It's just a weekend/track build. And while I don't want the FWD overpowered (I've had spin-monsters and too much power actually gets boring), I will want a little more eventually.
> 
> I'm probably going to go for around 2200 lbs curb and 220 crank HP. Should be fun without being useless. lol.


That'll be easy without even upgrading the turbo. A 1+ tune will get you to 220crank pretty easily! 

And dudes right, that'll be a blast to drive!


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## ExtremeVR6 (Sep 6, 2001)

URIN 2ND said:


> I guess it has good potential, but in stock form, it's really not all that impressive. A VR6 swap is most certainly faster. 2,500 lbs and 150hp...any Civic hatch with a B16 swap would kill it. Badly. But, a little bit of weight loss, and a couple bolt-ons, and it should be plenty of fun.


You're right, and a turbo vr6 is just plain ballsy. The 1.8t engine is a stout engine though... MANY people push it up to 350hp before doing any internal mods. It's lighter than the vr6 which lets it retain some handling benefit... Of course the vr6 and a diff will just pull the back end where ever you want it to go!


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## URIN 2ND (Oct 29, 2001)

ExtremeVR6 said:


> No problem... I'm not sure how accessible the wastegate is on the mitsu cars... But on my Audi I can get to the wastegate without taking the turbo off.
> 
> I can appreciate going that route, and honestly, without the n75 in place, you are free to run what ever you like now that I think on it... It's the later ones that freak out more. However, this does put you in a precarious situation where other systems and preventative measures can't work because the n75 isn't there. For example, if your MAF sensor goes out and if throwing wonky numbers to the ecu... Your cranked wastegate will be letting the turbo push up to 20psi... Meanwhile the fueling is running itself light because the MAF is saying there's only 150g/min going in, when in reality it's more like 250g/min... Hello melted piston. I prefer to let the ecu do its work and ruin my fun if something is going wrong... But that's just me.
> 
> ...


Oh, absolutely. That's why I'd only tighten the WG rod to about 12-13psi (just before limp mode). I'm not going to try to go for tuned-ECU boost pressures or anything. I will get a tune eventually. Just want to wake it up for the time being. There really isn't anything that could cause a 20psi+ "spike" short of the vac line to the WGA coming off...but I'd see/hear/feel it I'm sure. Had a few 30+psi spikes when dialing in the MBC on my last Volvo, and it definitely catches your attention. Old intercooler hoses are a good fuse, though - I find they burst at high boost pressure, preventing other further damage. LOL!


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## ExtremeVR6 (Sep 6, 2001)

Whatever works lol... BOV, intercooler hose! LOL


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## URIN 2ND (Oct 29, 2001)

ExtremeVR6 said:


> That'll be easy without even upgrading the turbo. A 1+ tune will get you to 220crank pretty easily!
> 
> And dudes right, that'll be a blast to drive!
> 
> ...


That's my target for this build...stock turbo. Quick spool. I wanted it to feel more like a larger motor without a turbo on it...nothing laggy. I actually started a build with a Mk1 Rocco that I'm parting out. It got overbudget in a hurry, and this was a more cost-effective route. Mk1 Rocco windshields can cost $1000. They are extremely hard to find these days...and mine was cracked.  It also turns out, at 6'1", I'm too tall for a Mk1 Rocco, so there was another $600 in racing seat and side mounts. A couple other similar surprises made me say "screw it - I'm going to a Mk2 Golf instead!"

And the rest is history.

Incidentally, I have a ton of Mk1 performance parts, ABA swap, built Peloquin 020, etc for sale in the classifieds if you know anyone interested! :wave:


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## 04v-dubGLI (Sep 29, 2011)

URIN 2ND said:


> I guess it has good potential, but in stock form, it's really not all that impressive. A VR6 swap is most certainly faster. 2,500 lbs and 150hp...any Civic hatch with a B16 swap would kill it. Badly. But, a little bit of weight loss, and a couple bolt-ons, and it should be plenty of fun.


Depending on the 1.8t that's in there, you could get 235hp with just a tune and exhaust. Much more than you could get out of a vr6 without boosting it

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## ExtremeVR6 (Sep 6, 2001)

URIN 2ND said:


> That's my target for this build...stock turbo. Quick spool. I wanted it to feel more like a larger motor without a turbo on it...nothing laggy. I actually started a build with a Mk1 Rocco that I'm parting out. It got overbudget in a hurry, and this was a more cost-effective route. Mk1 Rocco windshields can cost $1000. They are extremely hard to find these days...and mine was cracked.  It also turns out, at 6'1", I'm too tall for a Mk1 Rocco, so there was another $600 in racing seat and side mounts. A couple other similar surprises made me say "screw it - I'm going to a Mk2 Golf instead!"
> 
> And the rest is history.
> 
> Incidentally, I have a ton of Mk1 performance parts, ABA swap, built Peloquin 020, etc for sale in the classifieds if you know anyone interested! :wave:


Be sure to drop that stuff in the mk1 and engine classifieds. 

You might do some research on all motor, with port/polish and solid management, I've seen some ridiculous power from all motor 2liter 16v.


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## cmdshft (Oct 17, 2011)

You're not going to get that much boost from the wastegate on the 1.8T, the wastegate will likely only give you max 7psi adjusting the flapper arm. The default spring rate is 5psi anyway so you're barking up the wrong tree here.

Your best bet is to get a tune and keep the n75. The turbos on the 1.8T don't really like MBCs and will flutter and surge like mad. The ME7 and ME7.5 ECUs are really good at controlling things than mechanical can.


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## URIN 2ND (Oct 29, 2001)

cmdshft said:


> You're not going to get that much boost from the wastegate on the 1.8T, the wastegate will likely only give you max 7psi adjusting the flapper arm. The default spring rate is 5psi anyway so you're barking up the wrong tree here.
> 
> Your best bet is to get a tune and keep the n75. The turbos on the 1.8T don't really like MBCs and will flutter and surge like mad. The ME7 and ME7.5 ECUs are really good at controlling things than mechanical can.


Every other brand of ~5 to ~7psi wastegate I've ever adjusted has been able to yield AT LEAST 12-15psi. Sometimes in excess of 20 - reliably, consistently, and rock solid - as long as the diaphragm inside wasn't damaged. Usually, these were TD04 Mitsus or generic Garretts. I'd be very surprised if this was significantly different! You have to introduce excessive pressure against the spring...sometimes even using washers to space out the actuator bracket further away from the turbo (if you run out of room on the threaded rod), thus making the rod pull harder (against the spring inside) on the WG flapper arm. Usually, they were too tight to stretch out by hand, and you would have to use pliers to pull the rod on to the flapper arm. Usually the hole on the rod end would end up close to 3/4" too short to reach the flapper arm - this is the amount you would have to forcefully pull the rod out in order to attach it. That resistance is what raises the boost WAY beyond the factory setting of the wastegate.

At any rate, I WILL eventually get a tune!  I just want some time to research the different tunes available. The above method is a very common method for getting a quick ~15hp or so on MOST cars where the ECU controls boost via a solenoid, and it works just fine as long as you aren't too greedy. You just need to know the limits of the system you're working with.

Thank you for the feedback!


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## spartiati (May 19, 2008)

Tightening the waste gate to increase boost also limits how far the waste gate flap opens. That will make the turbo run much hotter. Also running directly off waste gate typically has a slower spool response. 

Now on a k03 it may not be all that noticeable, but a MBC will keep the boost source from reaching the waste gate until your target boost is met. Running a line straight to the waste gate will have the waste gate start opening prior to hitting your set boost which will in turn slow down how quickly it does spool up.


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## URIN 2ND (Oct 29, 2001)

spartiati said:


> Tightening the waste gate to increase boost also limits how far the waste gate flap opens. That will make the turbo run much hotter. Also running directly off waste gate typically has a slower spool response.
> 
> Now on a k03 it may not be all that noticeable, but a MBC will keep the boost source from reaching the waste gate until your target boost is met. Running a line straight to the waste gate will have the waste gate start opening prior to hitting your set boost which will in turn slow down how quickly it does spool up.


It does normally, but not when it's pulled that tight. Spools like it has an MBC. But yeah, the opposite side of the coin is watching out for spikes because there's less room for the flap to open and relieve pressure. I dunno...I'll try it out and see what happens.

I was just trying to avoid buying more than one tune because I didn't get what I wanted with the first one, or overpaying because I wasn't aware of all of the options out there.

Who offers the most affordable tune?

And a mechanic friend of mine mentioned Lemmiwinks software...is there a source online for shared tune parameters for use with Lemmiwinks?


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## ExtremeVR6 (Sep 6, 2001)

Part of what he's saying is that to crank it tight enough to try to get 20 or even 15 psi may effectively lock the wastegate close due to there being no travel left for the actuator to move. 

Also, you will also run out of threads to adjust the wastegate to that point. 

An MBC would reasonably inexpensive and far more easily adjustable than the wastegate actuator if things weren't quite right with your first adjustment.


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## cmdshft (Oct 17, 2011)

I seriously wouldn't waste your time with adjusting the wastegate arm for boost. Just get a tune. I have a stage 2 tune with the supporting mods that yields about 230-240hp on my k03s. Wasn't terribly expensive in and of itself, it's more the supporting mods.

Get yourself an upgraded intercooler and a 3" downpipe and an upgraded diverter valve and it's still easier than messing with a wastegate arm.


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## l88m22vette (Mar 2, 2006)

I was never patient enough to get it to work but with an MBC like the TurboXS HPBC, you can adjust both boost levels and onset behavior, I'll sell you mine if you want since its sitting in a toolbox drawer. Here is a thread with all the ways to ghetto-boost the 1.8T. I'd still get a wbo2 and a tune, my N75K makes me happy  With a little searching, you can also find a lot on how an N75/MBC hybrid setup works as well...

http://www.audiforums.com/forum/audi-tt-7/diode-mod-boost-guage-mbc-install-57086/


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## URIN 2ND (Oct 29, 2001)

cmdshft said:


> I seriously wouldn't waste your time with adjusting the wastegate arm for boost. Just get a tune. I have a stage 2 tune with the supporting mods that yields about 230-240hp on my k03s. Wasn't terribly expensive in and of itself, it's more the supporting mods.
> 
> Get yourself an upgraded intercooler and a 3" downpipe and an upgraded diverter valve and it's still easier than messing with a wastegate arm.


It's got a Spearco air/water setup...I'll probably buy the off the shelf 2.5" DP from TT...need to do more research on setups for Mk2 1.8t swaps.


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## spartiati (May 19, 2008)

URIN 2ND said:


> It's got a Spearco air/water setup...I'll probably buy the off the shelf 2.5" DP from TT...need to do more research on setups for Mk2 1.8t swaps.


Skip the 2.5". Get a 3" downpipe and save the upgrade later. After the downpipe you can neck it back down to 2.t" if you really wanted to.


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