Just finished installing my custom 3" dual exhuast on my z and man i never thought id see that boost guage reach 1.0 bar!!..Most i have seen before the install was 0.8 and thats after dyno tuning with the local unichip dealer. However i seem to be running into a problem because the car will go into limp mode after reaching 1 bar and i cant rev past 3000 rpm. I then have to restart the car for it to be normal again. Although my engine is not built i have been using the car for almost a year now and have done around 6000 miles, bear in mind that they where done in the scorching summer months of dubai, and the car proved to be ultra reliable with no problems whatsoever untill i changed the exhaust!! Anybody have any ideas of what might have happened??

 

Take it back to whoever built your car and did the install.

 

i dont think it has anything to do with the exhaust install. It might be the unichip trying to prevent me from overboosting and causing the car to go into "safe mode". i need somebody whos experienced somthing like this to comment!!

 

That MAF sensor is seeing too much air, you'll need to pull more voltage from the MAF sensor to prevent it from going in to limp mode. I am not sure if the Unichip will be capable of pull from the MAF, but adding to injector pulsewidth.

 

Yeah i thought it might be the maf, i dunno though if its got to do with the injector pulsewidth. I wonder what the guys that have the APS tt's do to overcome this. Please chime in guys!

 

are you getting a SES light at all?

when you changed the exhaust, you free'd up all that back pressure you had, allowing the car to boost higher.

I would take it in and have it retuned. Exhaust plays a crucial role in the amount of boost you run. You need to be retuned

 

I have been able to get the car to run higher boost levels with the Emanage Ultimate. The UTEC should be capable of doing this as well. I am not sure how it would work with the Unichip as it modifies the amount of fuel injected by tweaking the MAF voltage (only). Please correct me if I am wrong...

 

hmm my understanding of the unichip is very limited, However i do know that it has the ability of controlling boost. I will take it to have it tuned as soon as possible. I hope that i will be able to attain atleast 0.9 bar though!

 

hmm my understanding of the unichip is very limited, However i do know that it has the ability of controlling boost. I will take it to have it tuned as soon as possible. I hope that i will be able to attain atleast 0.9 bar though!

 

That definitely sounds like the MAF is seeing too much air and going into limp mode but I thought the Unichip clamped the voltage so I have no idea why it would be doing that. Maybe the shop forgot to hook up the MAF intercept wire? I say take it back..

 

it's not a factor of wheather or not it can control boost. You are basically in need of a tune. Opening up the exhaust the way you did, releaved the back pressure and it is allowing the car to create more boost. Your car was tuned with the previous exhaust you had on it. Now that you changed it, you need a retune, simple as that.

In addition to that, Mia's explanation may be right as well, either way, you need to take it in and have it ran on the dyno.

 

Now that I think about it the Unichip has a plug and play harness so not hooking up the wire is a non issue unless the MAF wire is not part of the harness like the CAS wire but I don't think thats the case. Its possible the MAF pin got pulled out of the harness though.. I'm 90% sure your issue is a case of the MAF going over voltage as these are the exact symptoms of that. No CEL, hit boost car goes into limp, cleared by cycling power to the car... Theres a SLIGHT chance the Unichip is faulty...in the end this all leads to you going back to the shop that installed it. If they are an APS authorized dealer they should be able to swap or fix whatever is wrong..

 

Thanx for the help guys, i dont think the unichip is faulty, as the limp mode started occuring just after i did a WOT run in 3rd directly after installing the exhaust. Ill get a retune and see what happens.

 

That's exactly what I meant, was trying to say, You just said it better....

 

Booomshaakalaka

 

If you are boosting 1 bar (14.7psi) and have stock interals you are headed for trouble! Every book I have read that a compression ratio of 10.5:1 it is safe to boost up to 9psi w/ a A/F ratio of less than 12, unless you run higher octane (race fuel) or water injection!

The APS TT is designed for 9PSI boost on our cars!!! I would lay off the HP until I made sure the boost and A/F ratio is corrected!

 

Well if he's in Dubai I'm pretty sure he's not worried about his engine blowing. It'll probably give him an excuse to build a 800-1000hp Z to whip up on all those 800-1000hp Skylines and everything else over there

 

its not the skylines and supras im after its the lambo gallardo's and ferrari f430's im racing...and im already whoopin those with the stock engine.

 

I just got some insight into the EMS and maf/map on the APS setups:

- The tuning solution included in the APS ST & TT systems clamps the MAF signal and uses a MAP sensor to modulate fuel delivery past the point where the MAF is overwhelmed.

 

Yeah that was kind of assumed already...so either the Unichip dumped, is not setup to clamp voltage soon enough (assuming that is even adjsutable), or the MAF intercept wire is shorted or pulled from the harness.