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Old 11-21-2001, 08:31 PM   #1
FuZZyLoGiC
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Arrow Road trip with a day old Unichip...

OK the car runs great in 1,2,3rd, pulls like crazy, but If I have it on cruse control at about 65mph in 5th gear, about 2.5k rpm, its very jerkey, same for 4th gear. It seem to cut out really bad then it just kicks in and goes, very unstable acting. Its really hard to drive in 4th and 5th when its below 3krpm, lots of cutting in and out, acts really sick.

This is very disturbing to me and dont feel very healthy for the car at all. Any one have this problem?? Im thinking about taking a trip to TurboXs and having it tuned on a dyno. Im not sure but I think I could have got the same preformance gains with some other type of controler. Thanks for any info!!

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Old 11-21-2001, 08:49 PM   #2
mWRX
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Default I think I know the problem...

I have the TurboXS unichip as well and noticed the jerky throttle response as well. After doing some research I think this is caused by the boost cutout point being around 50% throttle. What happens is somewhere around 40% to 60% throttle the unichip is programmed to go full boost. So the engine goes from little to no boost to full boost, achieves it's speed, drops boost again, loses power at no boost, drops throttle and boost again, then slows down, gives a little more throttle, hits the full boost point and your in a boost no boost cycle. There are two types of solutions to this:
1 - Go to TurboXS for a dynotune and have the full boost level throttle position reprogrammed at that time.
-OR-
2 - Get an Electronic or Manual Boost Controller.

I think I am going to go the Manual Boost Controller route myself, I just got rid of mine thinking the Unichip would do a better job controlling this. Apparently I was wrong, but overall, I am still very pleased with the unichip.

FYI - there is a group buy for the TurboXS MBC for $60 here

http://www.groupbuycenter.com/main.a...14&fval=&arch=
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Old 11-21-2001, 08:55 PM   #3
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Thanks for the help. So just use a MBC set at aroung ~16.5? What is the use of haveing the Unichip if your useing the MBC to get the boost? Why not just ditch the Unichip and go with a MBC? What is the role of the Unichip then?
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Old 11-21-2001, 09:03 PM   #4
mWRX
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Default the role of the Unichip

Besides changing your boost level, it further advances the ignition timing for more power. It also leans out the Air Fuel ratio to make more power as well. It removes the fuel cutout if you hit boost levels above 17psi (which more important if you want to replace the stock turbo).

The main reason I went with the unichip was for the fuel and timing curves. They are much more performance oriented than the stock maps. If you are going to do many more mods in the future, having the altered fuel and timing curves are much more important since the stock ECU will just pull timing and dump more fuel and negate any benefit of some of the other mods.

Hope that helps.
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Old 11-21-2001, 10:29 PM   #5
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Are people just all getting there unichips in the last few weeks and noticing the problems or have they existed all along? I hadn't really read much of this until recently. I can see where the throttle hesitation problems occur since the unichip does bring on the boost faster and not linearly (I believe) like the stock ECU does. With a MBC vs. the factory solenoid you are going to get more boost at partial throttle, which probably isn't the best thing either... I'd guess a good ($$$) EBC like the avc-r would be great in conjunction with the unichip that way you could control partial throttle, low-rpm boost better. But then again you are spending twice as much money on that solution.
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Old 11-21-2001, 10:39 PM   #6
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I dont know but for the $700 bucks I droped for the Unichip I was expecting something that was going to operate smoother than it is. If I have to get a $70 MBC than the total goes to $770 for the mod. What is some alternatives to the Uinchip?
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Old 11-21-2001, 10:47 PM   #7
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Have you called Mark? I am sure he would be glad to help. I have the stage one unichip and the only time I get any jerk is when I let off the gas from over 90%. 60mph in 5th is fine. I don't think it is a good idea to use a MBC with the unichip.
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Old 11-21-2001, 11:02 PM   #8
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I havent had a chance to call him yet. I just had it installed yesterday, I'll contact him after the holiday. I think I'll just bite the bullet and head up that way, 581 miles, about 8hr trip. If I had the car dynoed and tuned it will be allot better solution to the problem, may even squeeze a little more hp out of it. Thanks for all the help and information. I dont mean to sound bitter just concerned.
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Old 11-21-2001, 11:18 PM   #9
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I know that this thread seems to be on the Turboxs side of the fence.. but here is an cut and paste from cobbtuning.com:

With some extremely helpful insight into the Unichip tuning from our Australian partners, the Apex AVC-R boost controller was quickly replaced with the Unichip boost controller. The result has been an improved boost response at lower RPM and much more precise control over our boost levels at various RPMs. For reliability and optimal performance, we run different boost levels at different RPMs. While the fancy Apex unit can do this as well, it never proved to be as consistent as we needed.

I just wanted to throw that out there.. since some are considering the various boost control options. I'm pretty sure that the AVC-R can adjust boost based on rpm's AND throttle position.. but I can't quite remember. I was surprised that cobb ditched it from their car though.
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Old 11-21-2001, 11:25 PM   #10
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I've had my Unichip installed for about three weeks now and have experienced the same hesitation/jerkiness with part throttle between 3500-4000 rpm. I spoke to Phil and Mark about it today. They said that it is to be expected because of the closed system, the boost coming on much quicker and the tumble generators, etc... Honestly, I didn't follow all the technobabble, but they are aware of the problem and may eventually have a s/w upgrade to eliminate it. So, either go easy on the pedal or WOT and you won't notice it.

Richard
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Old 11-21-2001, 11:28 PM   #11
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lenyx, thanks for the post. I was just looking at the AVC-R. I think the Unichip takes more into concideration when adjusting the boost, a good thing. Is there a single unit that can adjust the air/fule, boost and timing, something other than a chip? What do they use to map the Unichip? Is there something a user can get the adjust the maps? Thanks!!
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Old 11-21-2001, 11:37 PM   #12
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I had another thread asking if users of Cobb Unichips had a problem with boost spikes. They all said nothing like the 20 psi spikes some have reported, and there was nothing about hesitation. One difference I can point out is Cobb/APS' use of a "boost control module" on their Unichip. I'm not quite sure how it works, despite reading through APS' site and ScoobyNet.

The Cobb Unichip isn't the only one with a "boost control module". Nearly all the Unichips referred to by posters in ScoobyNet mention a boost control module that came with their Unichip. Many others use electronic boost controllers, although most feel that you may as well buy a Link then.

Another interesting thing is nearly everyone who uses some kind of engine management system (piggyback or replacement ECU) agrees that the car must be individually tuned. There seems to be wide agreement that the right tuner is better than the right computer mod. Problem is, that's a tough order here in the continental U.S. From NYC, the closest Unichip tuner I know of is TurboXS, about a 5 hour drive. Taking my car to Cobb in Texas or Shiv in California is out of the question.

At any rate, you really should do some Unichip searches in ScoobyNet and see what they're saying across the pond. They've had the turbo Impreza a whole lot longer than we have.

http://www.scoobynet.co.uk/bbs/
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Old 11-21-2001, 11:43 PM   #13
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Thanks for the link!! Anyone know what control module they may be useing?? Something like a MBC?
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Old 11-22-2001, 12:14 AM   #14
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Here are some threads worth reading from ScoobyNet. They're encountering some of the exact same Unichip (mis)behavior that folks here are. [In shaggy stoner voice] Geez Scoob, is that spooky or what?
http://www.scoobynet.co.uk/bbs/threa...ThreadID=29555

Review of Unichip with mystery boost controller:
http://www.scoobynet.co.uk/bbs/thread.asp?ThreadID=9273

Same guy (Deep Singh) now saying it didn't work on his STi:
http://www.scoobynet.co.uk/bbs/threa...ThreadID=30123

A thread about TurboXS' plug and play harness (note Prodrive guy's ominous statement):
http://www.scoobynet.co.uk/bbs/threa...ThreadID=13460

"Unichip boost controller is not somthing that's fiddled with under the bonnet, it's a small encapsulated module that plugs into the Unichip module, no user adjustments"
http://www.scoobynet.co.uk/bbs/threa...ThreadID=52510

And many more!

Happy Thanksgiving guys. Time for bed. Long drive tomorrow.
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Old 11-22-2001, 12:21 AM   #15
Ken Levin
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Question cruise control jerkiness

Has anyone else experienced the same jerky response while on CC as fuZZy? What about you, mid9s? This would be a big factor out here in the "wide open" west.
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Old 11-22-2001, 12:29 AM   #16
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What I experenced was while the CC was on it was set at ~65mph. It runs fine till it comes into a load, like moveing from level road to a slight grade where it meeds more power to keep the set speed. This is where it really starts to cut in and out, very jerky..
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Old 11-22-2001, 01:26 AM   #17
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I have not had the problem that yall are talking about. I set the cc at 60 and goto work everyday. I have had mine in for 5000 miles. But when I get to large hills I tend to tturn off the cc because I don't want it to hit the hi boost that can make hi EGTs. That is the way I drive. I do ot do that all the time and I still have not had the problem that yall are having. Do you have a boost gauge?
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Old 11-22-2001, 03:08 AM   #18
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Quote:
Originally posted by bedabi
Many others use electronic boost controllers, although most feel that you may as well buy a Link then.
Yes,
But then again (in the case of the AVC-R) you're also getting a top of the line electronic boost controller that doubles as a digital gauge for boost and various other things and it gives you the ability to switch between two different boost maps on the fly. That's worth it to me, especially since last I checked bottle was selling them for $399 shipped. I actually bought one from him but sold it after I realized I was way over my head with no tuners in the area. I need to pay off my exhaust anyway :P
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Old 11-22-2001, 03:16 AM   #19
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This is just a thought but I noticed that you said it was only a day old. A lot of people have posted that the ECU takes a few days to relearn with the Unichip and eventually it drives a lot better.

The MRT TMS2 boost control system is really starting to look good now!

BTW - My Unichip is just a day old too!

???????????

Punk

Last edited by PunksWRX; 11-22-2001 at 03:22 AM.
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Old 11-22-2001, 11:24 AM   #20
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It does seem to improve over the first few days. Needle valve install and CC testing tomorrow.

Cheers
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Old 11-22-2001, 12:06 PM   #21
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Default Boost control

What up fuzzy..

If you want the Apexi AVC-D (what I use)
Its about $330 retail
I found them though www.ARDperformance.com for only $240

The uni-chip is great if used with a good boost controller like the AVC-R or AVC-D, or so I hear...

Bill
13.6@98 11-18-01
-AVC-D Apexi
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Old 11-22-2001, 07:55 PM   #22
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Hey Grenneracer6,
Is there a 4wd dyno in your area? I was told my a friedn that there was, that would be killer. Have you been to Fastenough Preformance in Lexington? Who installed your AVC-D?
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Old 11-22-2001, 09:29 PM   #23
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Quote:
originally posted by Fuzzy
If I have it on cruse control at about 65mph in 5th gear, about 2.5k rpm, its very jerkey, same for 4th gear. It seem to cut out really bad then it just kicks in and goes, very unstable acting. Its really hard to drive in 4th and 5th when its below 3krpm, lots of cutting in and out, acts really sick.
I haven't experienced this sympton at all. I actually tried to duplicate Fuzzy's sympton on the highway today and the car ran beautifully with no jerkiness or hesitation. I'm starting to think that a lot of the problems most folks are having are mitigated by the thinner air up here at higher altitudes.
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Old 11-22-2001, 10:18 PM   #24
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Im at 1200 feet
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Old 11-22-2001, 11:18 PM   #25
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I'm at sea level. Will test tomorrow.
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