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Old 04-06-2008, 07:40 AM   #1
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Default Jerking Problems

Ride is a 93 miata roadster 1.6 running on a td04 13L turbo.
Currently its running on a piggyback ECU (something like Emanage) tuned by a shop.

Somehow though, the car seems to jerk around the 5.5k rpm to 6k rpm range. The motor will rev higher then that if continued to do so but the jerking still exsists.

Anyone of you have the problem? Its a problem i want to get rid of asap!!
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Old 04-06-2008, 07:49 AM   #2
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Jerking around? Um maybe its your tire spinning.
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Old 04-06-2008, 08:03 AM   #3
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i dun think so bro, it feels quite obvious its because of the engine
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Old 04-06-2008, 12:07 PM   #4
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ping? knock? do u have a wide band?
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Old 04-06-2008, 12:51 PM   #5
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bro by wideband do u mean engine management?

if so, yes its a dastek unichip piggyback (similar to emanage) and got it tuned by a shop..
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Old 04-06-2008, 01:04 PM   #6
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by wide band i mean like aem ugo, a gauge to tell u what is going on when u get on the throttle

post some pics of ur setup, tell us exactly whats happeneing, the conditions it happens in
im sure someone here can help

maybe post the map u use for u car
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Old 04-06-2008, 01:41 PM   #7
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I don't think this is the place to discuss jerking problems.

But really, did anything happen before the problem started?
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Old 04-06-2008, 01:57 PM   #8
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my guess is it's going lean
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Old 04-06-2008, 02:08 PM   #9
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Originally Posted by Mach929 View Post
my guess is it's going lean
thats what i was getting at, also y i asked if he has a wide band
ide say check the map, and check fueling
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Old 04-06-2008, 02:57 PM   #10
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My vote is running out of fuel (maybe poor grounding).

Crazy, we need to know every single piece of your setup. What exhaust, what injectors, what fuel pump, what IC, what BOV, what boost etc... Pics would be awesome (use photobucket).

I'd be very interested to know where exactly the Piggyback is grounded.

I just looked up the Dastek piece and it looks fairly capable... pretty standard piggyback. The website doesn't really tell any specifics about it, like table resolution or injector handling or the speed of it's processor. It's also out of the UK so I assume you're there too, running a UKspec 1.6?
http://www.dastek.co.uk/features_unichip.htm

If this thing was tuned at a shop, then I assume you got the graphs of the various pulls? Can you scan the Dyno-sheets for us to look at.

My strong feeling is that you're on the stock fuel injectors and trying to run too much boost... the piggyback is adding as much fuel as it can and it's not enough. Since you can almost always load the car more on the street than you can on a standard dyno, you're probably just in need of some slightly larger fuel injectors. For now, stay out of boost.

You're also going to want to invest in a wideband AF gauge. It tells you how much oxygen is left in your exhaust gas.
Too little oxygen = too much fuel = rich = poor mileage = loss of power.
Too much oxygen = not enough fuel = lean = knock = blown engine.
Either the AEM UEGO, or the INNOVATE LC-1 will serve you well.
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Old 04-06-2008, 05:09 PM   #11
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Hey thanks for the feedback guys..

More info....
Currently here are the mods

TD04L from a subaru wrx
Custom Top Mount Manifold
2.5 inch Custom Downpipe and Exhaust
2.5 inch Charge Pipes
Mitsubishi Vr4 FMIC
4 Standard Injectors
1 Extra External Injector
Walbro 255L HP Fuel Pump
Greddy Type Rs BOV
HKS Mushroom Filter
Boost Master MBC (Replaced this with an Apexi Electronic unit)
Dastek Unichip 128-bits

Here is the current dyno graph....
Name:  crazydyno.jpg
Views: 3
Size:  53.0 KB
This is currently boosting around 11.8 psi
As you guys can see... the jerking occurs coincidentally with the dip during 5k to 5.5k rpm... any idea whys that?

I will post more pictures of the setup when it is done...


Im going down to the shop tommorrow and get them to solve the problem, jerking during boost really isnt no fun at all
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Old 04-06-2008, 05:16 PM   #12
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Hey compy, sorry but am i in the wrong folder? Where should i move this to ? I assumed that i could create a new thread here as my setup is a DIY setup.
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Old 04-06-2008, 06:25 PM   #13
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is running out of fuel and boost.
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Old 04-06-2008, 07:27 PM   #14
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I see that you had a manual boost control...did it start to jerk and run poor after you changed to the electronic boost control?


Tony
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Old 04-06-2008, 08:09 PM   #15
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YOU ARE WAY OUT OF FUEL on the stock injectors.

The Walbro255 is known to overpower the stock FPR and cause idle and tuning problems. An aftermarket fuel pump is not needed when running an ECU or Piggyback. Swap back to the stock fuel pump. Get yourself a set of these:
Toyota 3SGE 295cc Green Top
89-92 Toyota Supra 7MGE NA 305cc Light Green Top #23250-70080
93-95 Toyota Supra 3.0L 312cc - Maroon Top #23250-46030
Toyota 3SGE 315cc Pink Top
90-92 MX6/626/Probe Turbo 326cc - Gray Top #195500-2150
89-91 B2600 Truck 326cc - Gray Top #195500-2150

Then go back to the dyno and beat them severely. There's no possible way they were getting decent AF's at 12psi on the stock injectors. I can't imagine you're running any richer than mid 13's and that's just not cool. Do you have the AF graphs with the dyno sheets?

You need to turn the boost down in the meantime.
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Old 04-06-2008, 08:59 PM   #16
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ops... i always forget to add that i have :

255 walbro fuel pump,
Sard Fuel Pressure Regulator,
1 External injector.... (Evo 510cc)

Even with these, i do not know whether the total provided fuel will be enough... Is it really advisable to run the stock fuel pump at these kind of boost and power??

Anyway, im going to the shop soon, hopefully they will be able to solve my problems....
Thanks for the feedback guys, the miata community is so much more friendlier then the honda community

oh and btw Tony, we were having problem with the mbc as it was abit difficult to tune, that was why i swapped the mbc for an electronic one... Going back to the shop to tune the ebc in a few hours time.. hopefully they can do something about the overall running of the car.

Last edited by crazymiata; 04-06-2008 at 09:09 PM.
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Old 04-06-2008, 09:25 PM   #17
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Quote:
Originally Posted by crazymiata View Post
Hey compy, sorry but am i in the wrong folder? Where should i move this to ? I assumed that i could create a new thread here as my setup is a DIY setup.

No, it was a joke... jerking issues...
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Old 04-06-2008, 09:31 PM   #18
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Hey compy bro, haha, i did not get it at first...

Btw to answer ur first question, no problems at all before the tune as the turbo setup was just complete physically, and we did not boost the car before the tune.
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Old 04-06-2008, 09:42 PM   #19
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Quote:
Originally Posted by crazymiata View Post
ops... i always forget to add that i have :

255 walbro fuel pump,
Sard Fuel Pressure Regulator,
1 External injector.... (Evo 510cc)

Even with these, i do not know whether the total provided fuel will be enough... Is it really advisable to run the stock fuel pump at these kind of boost and power??
That extra injector changes everything and completely removes me from the discussion. I don't know anything about the mechanics of "extra injecting" so I will gracefully shut up now.
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Old 04-06-2008, 10:15 PM   #20
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well still, 4 stock 205cc injectors plus 1 510cc injectors equates to 1330cc of fueling....divided by 4= 332.5cc injectors. still not enough fuel for big power. Plus i think the stock ecu is interjecting at that 5-5.5K spot where it always does.
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