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View Full Version : Overboost Elim - 25+psi!



gmx
12-10-2009, 04:51 AM
Unitronic 415cc file
4bar FPR
All supporting mods
71R elim

My gauge only goes up to 25psi, and it's pretty much hitting that limit.
It says preset for 20-21psi controlled by N75. And when I filled out the form with my local dealer we specifically selected for N75 controlled file.
I retained the N75 and don't have a MBC/EBC (and don't want one).

I tried searching and didnt get much.
I read about faulty N75s, but these would usually vary in boost(regulation) or just restrict it far below requested.

What could be up?
Faulty N75 ? This only happened after the turbo swap.
The wastegate spring on the 71r elim is 1bar AFAIK.


Don't know where to go from here.

Obviously I don't want to continue driving it like this. I've been keeping it part throttle/trying not to go into boost at all.

lowandslow4now
12-10-2009, 05:25 AM
Bypass the N75 and run a line directly to wastegate if you are still spiking that high than your wastegate actuator may be bad. If it runs the proper wastegate setting then I would scan and check for any N75 codes.

Wet0willy01
12-10-2009, 05:28 AM
Did you verify the wastegate spring pressure? The linkage is adjustable to vary the pressure. I was told by Uni to set mine at 10lbs versus 14.7lbs(had to specify on order sheet) to prevent possible overboost issues. Don't know if this is 100% relevant to you or not?

Dan[FN]6262
12-10-2009, 06:32 AM
i run 25psi on my GT71R eliminator. in fifth gear if i roll onto it'll peak at 27psi lol

97a41.8t
12-10-2009, 06:39 AM
When i filled in my form, I also specified to retain the N75. However, they scrapped that and the N75 stays closed the entire time.

I went with a Hybrid MBC and didn't want to deal with shipping my ECU to their HQ again.

Also like Wetwilly said, check to see if it requires a specific wastegate setting. Good Luck.

Shhmaudi
12-10-2009, 10:17 AM
Damn Im running unitronics w/ 440 injectors and vr6 maf with only 18psi of boost... I feel like I should turn my Mbc to at least 20-21 now lol..

Would there be any harmful effects???

Gaberossi
12-10-2009, 10:24 AM
I'm on a K04 and i have the same problem...but im running soo rich on this file that at 30psi it feels freaking amazing...def feels like something is gonna break tho....i was told it was my ecu that had to be rebuilt by Unitronics bc they sent me a corrupted file....it only hits 30 psi when i shift gears...but if i am in one gear then go WOT it goes to 24psi and tapers back to 19-20psi

gmx
12-11-2009, 06:01 PM
I've bypassed the N75 for the time being and am running it off the wastegate @ 15psi.

Can I keep running it like this? Part throttle doesn't seem too bad at all.
What's bad about it apart from missing out on 5 more psi?

Yup, my mech said the N75 duty cycle was such that it was requesting boost even at 20psi and even at 25psi. So we checked everything N75 related (didn't try another one, but no codes and usually they don't fault like that I believe), and we believe it's the file.

I don't see the relation to the wastegate spring rating, the N75 duty cycle is still going nuts at 25+.

gmx
12-13-2009, 02:32 AM
Response on the above???


Just a thought.
Could my plugs be causing the crazy spike - spark blowout?? They are BKR6E(-11) @ .032 IIRC.
30C weather here.

maybe I"ll try other plugs and reconnect the N75. What do you guys recommend to just try quickly?

97a41.8t
12-13-2009, 09:02 AM
You can keep it at 15psi, but you are missing out on a lot more power.

Get a EBC/MBC and call it a day.

gmx
12-14-2009, 04:39 AM
You can keep it at 15psi, but you are missing out on a lot more power.

Get a EBC/MBC and call it a day.

hmm, i might do this, but = more $$
The partial throttle N75 thing is overrated imo - & I'm a big supporter of drivability = performance.
EDIT: I"ll have to send the ECU back anyway for the bigger TB, so... may not be worthwhile.


We have the N75 disconnected electronically. On the CORRECT(N75 controlled file), this would mean it would through a CEL? Or just a code?
I hope they didn't give me a totally different file, ie 440ccs @ 3bar or something.

gmx
01-07-2010, 07:42 AM
The problem actually is the tune is programmed for a 10lbs spring.
I remember I put 14.7 on the form originally, oh well.

I'm still on the lookout for a profec b spec II (anyone know where to get one cheap or have one used??)


97a41.8t, can you show me your install of the EBC?

97a41.8t
01-07-2010, 08:11 PM
I have a hybrid MBC.

You can purchase the TurboXS Hybrid or make your own. I was cheap so I made a custom setup using a bleed valve in series with a ball & Spring following the write up at

http://autospeed.com/A_111348/cms/article.html

Using my AWESOME MS Paint skills, I created a drawing below.

http://i197.photobucket.com/albums/aa121/byronc_14/Series.jpg

-Ball/spring MBC allows boost to build for the first (X)psi which I would recommend to be below 10psi to avoid bucking.
-Bleed valve is adjusted for maximum allowable charge pressure

So at low (2k-2.5k) rpm I still get about 5lbs of boost from the ball/spring mbc and full 23lbs at ~3400rpm. At partial throttle bucking is pretty much eliminated.

B5A4Kevin
01-07-2010, 09:55 PM
is the elim enough for you or are you starting to feel the need to go bigger like most other ppl on here?

only reason i ask is because i really like the idea of the elim as theres less supporting mods needed compared to BAT, but i just cant make up my mind between that and a fullframe setup (hta3076r)

B5A4Kevin
01-07-2010, 09:58 PM
if you get your software sorted out to where it isnt requesting boost still at 25psi, you can also run your n75 and ebc/mbc in parallel. when properly dialed in, it completely eliminates boost spikes/surging and is inherently a safety net. if either the mbc or the n75 fails, the other will still function normally.

gmx
01-08-2010, 03:24 AM
if you get your software sorted out to where it isnt requesting boost still at 25psi, you can also run your n75 and ebc/mbc in parallel. when properly dialed in, it completely eliminates boost spikes/surging and is inherently a safety net. if either the mbc or the n75 fails, the other will still function normally.

Thinking of getting rid of the N75 entirely (or just close circuit it). Been hearing more and more that EBCs/MBCs build boost slightly faster than all versions of N75 out there.

As for choosing the Elim.
I need a stock looking engine bay - only other choice was finding a APR Stage3 mani and building a setup around that.
I prefer response instead of ballistic top end power.

The power is good. Even only @ 13-14psi, it's more than enough for the street honestly. Could use far more tq at low rpm, but that's what a 4 cylinder is pretty much limited to. THe power really completes the rest of chassis setup. It's really a breeze to drive in the higher speed (ie not a hairpin lol) corners/flowing sections.

I'm still on the lookout for the APR mani and/or kit... Would love to try that kit with the uni tune.