Rick Carter

Subscribing.

victor25

I personally believe that if someone was to take the time to install a modern fully adjustable ECU, then measure O2 and or gas temps for each cylinder there could be huge gains on the stock S4 engine. It would take a lot of time and work, but it could be done, and actually kind of has been done. With the different intake and exhaust lengths each cylinder has to be quite different. But if each cylinder could be finely tuned with a sequential system, then the ignition could then be advanced across the range, giving us much better torque and even gas mileage

ptuomov

Main issue is fueling in the knock sensing S4. My computations (=wild a$$ guess) are that there's something like 7% variation at worst rpms in the fueling between the rich and lean cylinders. So if you are on average 13.0, then the lean cylinder could be 13.5 and rich cylinder could be 12.5. Porken and others with a lot of NA tuning experience could give us some indication whether being 0.5 point off from the ideal fueling is going to rob many horses.

FBIII

Having an engine that has an intake system that creates a situation where cylindesr are going to generate different amounts of hp and torque can't be a good thing from a logical standpoint. I would imagine the higher hp cylinders are going to bear more of the load and wear over time.

GregBBRD

That is seriously funny!

DKWalser

Assuming that is true. The next two questions are: How replicable would the set up be for other S4 engines? And, are the benefits worth the approximate $2k in cost? Ken's chips are premised on the assumption that his updated programming will apply to other engines. As for the benefits, if there were material benefits in torque, gas mileage, and (I would assume) reliability, $2k would seem to be more than worth the cost.

DKWalser

Glad I made you smile.

Seriously, I understood moving to true sequential injection would require a lot of work and would require upgraded spark management. I didn't know if you would need o2 sensors for each cylinder, or if it would be possible to mount knock sensors (temporarily) above each cylinder. (Do knock sensors that sensitive exist?) Whatever approach you take, it would obviously take a lot of work.

PorKen

I reckon the best starting point for more power is using CNP or COP (to allow a larger spark-plug gap).


On the dyno I haven't seen a difference in output between 12.5 and 13.25 (assuming the engine temps are consistent).

Much above (an average of) 13.0 and I haven't been able to run as much advance w/o knocking. AFRs in the mid 12's produce few knocks. It's easy to put in too much advance if you tune there, though. Better to tune at >13.0 and richen when done. Get into the 11's and knocks come back. (I have a theory the compression ratio goes up with all that fuel in there.)

I see a difference in logged MAF units at high rpm depending on AFR. Get into the 12's and airflow drops off.

victor25

LOL we should probably get the thread back on track... Greg do you have any more pictures of that sweet *** exhaust manifold setup. And when do we get to see the after dyno charts!!!

Pfc. Parts

subscribed

Randy V

Just an FYI you can subscribe to a thread by clicking on the 'thread tools' link located at the top of the thread.

ptuomov

Density of air is 1.2kg/m^3. At 100% VE, 928 cylinder gets 625cc or 0.75g of air per cycle. At 12.5 air fuel ratio by weight, we'll also put 0.06g of fuel in the cylinder. If we increase fueling to say 10.5 AFR, we'll be putting in 0.071g instead, or 0.011g more. Fuel from memory is something like 0.8g per cubic centimeter, so the additional fuel will take 0.014 cc of space. At 10:1 compression ratio, the combustion chamber volume is 69.5cc. The 0.014cc taken by fuel would increase the compression ratio to 10.0018, an increase of 0.0018 points of compression ratio.

If I did the math right (always a big if), then the knocks probably aren't caused by a simple increase of compression ratio.

RKD in OKC

If you run too rich the cylinder gets hotter just like when running too lean.

GregBBRD

Updated photos:





Ground clearance.....not the lowest thing on the vehicle!



Obviously, the center section will be available with and without cats, for those of you that are running on race tracks.

Rob Edwards

Purdy! What time is lunch today?