1995 850 2.5 10V timing with lower exhaust backpressure

[radoKE]

hi all, looking for suggestions about timing setting. I put an ferrita sport exhaust on my 850 b5252fs engine and lost some power in comparsion with stock exhaust. IPD makes timing tool, there are degree marks for intake and exhaust cams and ipd in one suggestion say that both cam need be advanced or retarded the same amount. ( when trying shift power band in RPM range) But i thing this is suggestion for factory part configuration not for tuning parts. IPD suggestion about correct overlap amount is unclear, only that correct amount is tricky to find and experiments are required. So the question. Where should i start with ( intake or exhaust cam ) if i will add more overlap? Retarding exhaust cam ? VVT in modern engines is on exhaust cam, so i think that exhaust cam ist correct way ?

[hausmeister]

Did you install a catback (everything after the cat) or with downpipe and cat? Don't think a catback should matter so much. maybe you have another issue going on?
In any case if the exhaust is the reason I doubt you can get the losses back by messing with valve timing... but maybe someone here has the experience to provide help (I don't).

[radoKE]

i installed nothing more that this one: https://www.ferrita.com/en/products/car ... 25-10v-20v
maybe there is some other problem because yesterday after 400km trip lambda light start lighting and from diagnostic come out 231 error, "long term fuel mixture too rich in part load stage" Surplisingly after this modification i have better mileage, before it was 8.7l/100km yesterday it was 7.3l/100km. Morning i will check and set factory timing with cam tool, after that i will try move both cams to slight advanced position.

[scot850]

I have been looking at a more free flowing exhaust manifolds for my V8 Toyota 4Runner. One of the issues that a free'er flowing system is that is causes problems with the O2 sensors as more flow throws off what the sensors expect to see. The solution the supplier has is to weld in like thick washers onto the O2 sensor bung holes to move the sensors further out of the flow which then prevents the engine check lights going off and allows the ECU to calibrate correctly.

Be careful running the engine too lean or you could burn your valves. As you have done a long run, it may be worth removing some spark plugs and see how they look. It will give you an idea if it is running rich or lean.

Neil.

[hausmeister]

So, my limited understanding is that it should not affect the O2 sensor as you are not changing the exhaust gases. Just the pressure might be lower/more volume might be flowing. Usually these spacers are to pass emissions with cat removed or race cats. (places the sensor farther from the gasses, and it does not provide accurate readings any more)

In fact, when I upgraded the exhaust on my Volvo there was no issue with the O2 sensor readings.
I would start to diagnose the code... and not mess with other things until it is fixed. Just my opinion.

[radoKE]

Today a make factory timing alligment with factory tool. Engine run better, before alligment i put out sparks, two of then seems running lean, one normal and two rich. Injectors problem ? Will check sparks again after next trip, maybe new timing brings some difference...