Hi all,

Got my car back off the dyno last week and before I get into the issues, its actually running really well now.

The car has had the turbo replaced after an exhaust manifold fell apart on me so I took it to get a clean up on the tune.

Initially, the tuner had to add a fair bit of fuel which raised eyebrows. He checked the plugs and the car was running leaner on the rear rotor then the front.

Sent the injectors away to be tested and they were perfect. After checking wireing and setup etc on the ecu, they found no fault.

Added about 5% more fuel to the rear and the car is making more power then it ever has and the plugs look even.

Now this problem never used to be there. The plugs always looked even. The only thing that has changed is the manifold is now an open manifold when it used to be devided (its not a devided exhaust housing on the turbo so there wasn't any point in the devided mani), and the turbo has had a new exhaust wheel/shaft and ceramic bearings installed.


Anyone got any ideas what could cause a difference in mixtures in the two rotors?

Car specs:
13B Bridge port - fairly fresh build
HKS T51R SPL turbo
Microtech
1000cc top feed primaries
1680cc top feed secondaries

Things we have checked:
Injectors - tested fine
Wiring - all perfect
Compression - prefect
Nothing has changed other then the manifold and turbo since it was last on the dyno

 

how did he manage to add fuel to the rear bank with the microtech?

 

How is he determining its lean on the rear rotor? Assuming he's looking at EGT's you might want to have him swap sensors or ensure its not the sensor.

 

im with karack on this one......... how he was able to add fuel to just the rear rotor, kinda perplexes me.

 

put a bigger injector in ??? (JK)

 

engineer a front and rear chamber pair of fuel rails and run the rear rail reg at a few more psi ?

or weld in an injector bung on the rear runner of the LIM and piggyback another injector there from r2 secondary injector ?

put a rag in the front runner plenum to tune the front runners airflow ?

increase the voltage to the rear injector clips ?

 

yeah right.. sounds like his tuner is bullshitting him or there was a big miscommunication. most basic standalones(microtech is very basic) do not have capability of adjusting induvidual injector pulsewidth, not referring to you but for the OP to understand that what he is telling us is not possible.

basically if he's reading AFRs off the plugs i would guess you have low compression on your front rotor if it is reading darker, if the injectors were balanced properly. that or you are eating oil in the front rotor.

 

From memory screen 30 has the cylinder trims. Trim 1 controls front rotor fuel, and Trim 2 rear rotor fuel.

In my experience there are two causes of a mixture differential like that. 1) an intake manifold leak, and 2) bent or damaged apex seals on one rotor.

You said compression is fine so look at the intake. Look for a leaking gasket, or a vacuum hose off.

A friend had a leaking upper to lower intake gasket on the rear rotor and his Microtech had to be trimmed 10% to get EGT's roughly the same. Once the gasket was replaced the trim was not needed.

 

if it was fine before, and the only thing that was changed is the manifold, then therefore it must be some difference in the new manifold that is causing the lean rear rotor

 

I'm fairly sure you can make cylinder adjustments with the microtech as JZG has said.

The manifold was an open port manifold that some IDIOT has welded a divider into to make it a divided manifold. The mix was fine with it running divided, and the only thing I have changed, was removing the divider and cleaning it up. Its still the same manifold, nothing major like runner length has changed and its always been a non divided exhaust housing on the turbo.

Is this likly to be the cause of the difference? Or should I be looking for another cause?

 

ive always noticed rotor egt inconsistant with an external dumped wastegate. best way around it is 1. add fuel to X rotor if possible as some cars are very lean from all the exhaust shooting out the gate, 2. run a re-routed wastegate, 3. run dual wastegates. i personally run a re-routed wastegate as i like the extra tq and the whistle of a turbo.

 

what lower intake are you using, the stock lower 3rd gen has flow imbalance witch is why xcessive manifolds exist.

 

Yeah it is the stock 3rd gen LIM. But this has always been on there, and it was never a problem before now so I doubt this has anything to do with it.