EOIT on a TSP 228R. Is my thinking right??

[FC3S Murray]

Sorry for not getting back sooner.

Went out last week and attempted an EOIT of 5.71 & 5.89. Both numbers required more fuel, brought back some minor low rpm bucking and fuel smell was worse.

I loaded my original EOIT of 5.29 from the year before and it ran perfect.

Just to experiment I even ran the 5.29 EOIT on the already adjusted VE for an EOIT of 5.89 and the AFR's turned rich and I had to reduce my low RPM VE by about 3%. Bucking vanished.

So with the 228r and my particular engine set-up an earlier EOIT than the stock 5.55 was beneficial.

[kingtal0n]

Sorry for not getting back sooner.

Went out last week and attempted an EOIT of 5.71 & 5.89. Both numbers required more fuel, brought back some minor low rpm bucking and fuel smell was worse.

I loaded my original EOIT of 5.29 from the year before and it ran perfect.

Just to experiment I even ran the 5.29 EOIT on the already adjusted VE for an EOIT of 5.89 and the AFR's turned rich and I had to reduce my low RPM VE by about 3%. Bucking vanished.

So with the 228r and my particular engine set-up an earlier EOIT than the stock 5.55 was beneficial.

Did you change the boundary from 6.5?

Interesting results I wonder if it means your crank reluctor has moved or something like that. Unless you also changed boundary

[anniversaryss]

That cam doesn't have a lot of overlap so you shouldn't have to do to much with EOIT but i love messing with tables to learn. That being said if you advanced the IT and the car ran better and less smelly you did it right.

From the great Ed from ERMperformance.

Take the difference in IVO from new cam to the stock cam and divide it by 90. Take that number and subtract it from the Normal. You are now taking advantage of the evaporation technique that GM uses. You should see your AFR richen up from better combustion quality (hence less smell).

Now you say this helped and you have better quality and less smell. So this worked for you and I wouldn't even worry about.

But

Say it didn't and you have to adjust for cam overlap.
Whay you want to do is movie your start of injection timing to peak piston velocity (PPV). This will spray fuel after the exhaust is closed and use piston velocity to mix the fuel and air better. That means moving Soit to about 430 degrees. This will require a larger injector from what he says.

I am not an expert at this but ed was and it seems to work well.

[FC3S Murray]

Yeah, like I said in my original post, an earlier EOIT worked.

I have a bad habit of doing adjustments very extensively and once they work I seem to brain dump the memory after about a year. I am glad I went back and reconfirmed my findings were correct even after reading more about injector timing and my particular cam set up.

I am obviously taking advantage of GM’s method of fuel evap on the back of the intake valve.

[kingtal0n]

When I briefly tested this feature I found a somewhat linear relationship moving from the OEM value of 5.55 to around 6.0 with respect to wideband readings richening up.

The exhaust valve close point is exactly 1 place in time, we could say it is roughly centered around some number of degrees of revolution I suppose (closed but not quite closed is still kind of closed) this leads me to believe the richening up effect I was seeing has nothing to do with exhaust valve closure.

In other words, if the exhaust valve close point has something to do with the richer a/f ratio then it would happen suddenly at some specific narrow range of EOIT number settings, and we would NOT see a linear increase in richness while moving from the OEM valve towards a 6+ setting.

Realizing this I came to a conclusion that the real reason the engine is richening up is because the fuel isn't being allowed to leave the intake valve area and travel back up into the plenum before the valve can open.

In other words the later EOIT is giving a linear increase in rich a/f ratio because by injecting later and later we are keeping more fuel near the intake valve.

As fuel boils from the valve while the valve is still closed, it can move back into the plenum and is lost in the dynamic and turbulent environment probably enriching all cylinders somewhat and displacing some air there. Which means later EOIT also should improve air density in the plenum some minor 0.00X% or whatever.
$0.02

[kingtal0n]

Meh I just log the a/f and compare EOIT with new a/f ratios

New EOIT causes rich areas



Re-tuned for new EOIT to cruise 15.1's steady state


Looks like it costs some power on the big end, but added torque low end and saved some fuel by making 2000-2800rpm more efficient?
Looking forward to a dyno in July to compare

[kingtal0n]

Thanks... I Started off in biological science, medicine, bacteriology, viruses, anatomy, chemistry, orgo/inorg etc... Then after I'd taken almost every science/chemistry and bio course at university decided to try my hand at engineering. I went for bioengineering at first, to combine the biological aspects. Eventually after the MS realized I needed much more engineering background to understand space ships larger machinery than cars and boats, and I started over from Mechanical engineering undergrad courses and took the statics, dynamics, thermodynamics, fluid mechanics, dynamical systems, calc 2 3 diff EQ etc... to get my foot into doctor of mechanical engineering courses, which leads to mathematical methods, ocean engineering, advanced mechanics of materials, advanced control theory, vibrations, fluid dynamics... and now I feel pretty confident in my ability to describe both mechanical and biological inner-workings and can work with either as a stand-alone concept or combined. I teach mechanical engineering and biological science courses on and off as a teaching assistant to pay for the degree work, pays for itself. And I tend to learn as much by teaching as actually being a student, its funny how trying to explain something to students can often lead to a deeper understanding for yourself. Thanks for checking out my build