ECU - closed loop / open loop

[Gelf]

Im been doing some testing using an accelerometer at WOT, ive seen reductions in bhp and torgue, mainly because the ecu's cutting boost.

Im using the smallest jets ive got 0.4 (manifold) and 0.5 (pre turbo) triggering at about 14 psi. Ive tested both jets individually or both together now with similar results.

When the throttle is at WOT in open loop, the ecu ignores all the input from sensors, why does it cut boost ? The ecu wont know the air is cooler and make adjustments, but the air should be denser, so make more power. I didnt expect much of an increase at this stage, but not a reduction.

Im thinkin i may need to move the jets further back from the throttle plate and the turbo for better mixing. (See gallery)

I have an issue with my generic remap at the moment, which seems to make maximum boost and so maximum torgue and power at 3/4 throttle, and feels very flat after that point. Dont get me wrong, the car has been Dyno'd without any issues, the AFR was said to be fine, bhp is up from 190 to 230 at WOT.

I intend to prove this with the accelerometer, by sticking shims under the pedal to reduce pedal travel and comparing the results. Its a fly by wire throttle by the way (no cable).

With a higher flowing exhaust, the K04 turbo can push to 260 bhp on this car, without WI.

Will the ecu learn not retard the ignition and not richen the fuel in closed loop mode when boosting at partial (3/4) throttle, with continued WI use and with Dyno tuning required to adjust the maps for WOT :?: Which i have booked for the near future.

Richard, can you turn the water pressure switches to far clockwise, or will the pumps just remain on constantly at 10 bar :?:

[Richard L]

Some car has an ignition system that will only give a constant energy to ignite the charge, at higher power, the spark will not have enough energy and resulting in slight misfire - reducing the spark gap will proof this theory.

Nice way to control your fly-by-wire angle - paddle to shim metal!

Please do not turn the water pressure up tp 10bar as it is the limit of the pressure switch, you will endanger the pump because ot might not switch off. 9.5 bar is fine.

[Gelf]

I will take the plugs out and inspect them. When the car was remapped, colder plugs were fitted. Would the introduction of WI mean that the origonal plug rating could be used :?:

Can plugs run too cold :?:

[Richard L]

I would run normal plug for sure for the time being.

[Gelf]

Can plugs run too cold :?:

Did some research and the answers yes, too cold and fouling occurs.

[Richard L]

Do you know what I am going to suggest next? increase your boost and bring some more heat into the engine. :twisted:

[Gelf]

Do you know what I am going to suggest next? increase your boost and bring some more heat into the engine. :twisted:

I dont think the stock turbo has much more to give,

Standard, 9 psi and 13 psi overboost

Now, 14 or 15 psi and 19 psi overboost

I think 20 psi is its limit :evil:

I will check the plugs and see if the gap is out of tolerance, hopefully that will cure my flat spot.

[Richard L]

Can you close the spark gap at all?

[Gelf]

I had a flat last night, found a nail in my tyre, got the narrow spare on at the moment, i will look at the plugs at the weekend. No more testing until ive got the tyre back from being repaired next week :sad:

[SaabTuner]

"Proper Plug Gapping:

* Proper gapping of the spark plug is necessary to get maximum spark energy, lowest RFI release as well as what is best for the longevity of the secondary ignition components (coil, cap, rotor, wires, plugs).
* When checking plug gaps, the correct way is to use ONLY wire gauges, though many of us are using the slider style gapping tools. These flat or feeler gauge style gauges do not accurately measure true width of spark plug gap.
* When increasing the gap size for our high performance applications utilizing advanced ignition systems such as Mallory, Accel, Jacobs, Crane and Holley ... it is important never to go more than plus or minus .008". This is to maintain parallel surfaces between ground and the center electrodes.
* Something many do not know, is that with Higher Compression ratios and Superchargers as well as Nitrous, in many cases smaller spark plug gaps must be used as well as the use of a much hotter ignition system (see above). These higher cylinder pressures require more energy to jump the spark plug gap.
* The rule of thumb on plug gaps is to open them up in .002" increments at a time. When the car (race vehicle) begins to lose power or slow down then go back .001-.002" and this in most cases is the optimum gap."

Stole that from here: http://www.centuryperformance.com/spark.asp

So I'd say either close the gap, or increase the spark voltage!

Adrian~

[Gelf]

Richard, Adrian

Thanks for the advice :D

Andy

[Gelf]

I reduced the gaps down from wellover 0.7 until i just couldnt get the 0.7 gauge in the gap.

Been driving today, there is a difference. Plugs were a biscuit brown colour, but a bit sooty also.

[Richard L]

I learnt from the past that the rallycross cars ran between 0.4 to 0.45mm plug gap when tuned to produce 700-800 BHP.

Your result was consistant with plug gap. If the plugs were biscuit brown with some black markings, it appeared that the fuel didn't have enough time to finish burning before exhaust valve was opened. It could be ignition timing related or still a small amount of mis-fire.

Do you have means of advancing the ignition or reduce the plug gap further?

[Gelf]

I learnt from the past that the rallycross cars ran between 0.4 to 0.45mm plug gap when tuned to produce 700-800 BHP.

Your result was consistant with plug gap. If the plugs were biscuit brown with some black markings, it appeared that the fuel didn't have enough time to finish burning before exhaust valve was opened. It could be ignition timing related or still a small amount of mis-fire.

Do you have means of advancing the ignition or reduce the plug gap further?

No way of advancing ignition as im aware, with altering the map that is. Ive got a distributorless, direct ignition system.

[TurboGTi]

Your result was consistant with plug gap. If the plugs were biscuit brown with some black markings, it appeared that the fuel didn't have enough time to finish burning before exhaust valve was opened. It could be ignition timing related or still a small amount of mis-fire.



Richard the above statement made me realise how much fuel i'm wasting ... my spark plugs are always sooty ... hmmmm ii've already reduced my spark gap to about 0.6 or so so i'll try and pull some mS from the fuel injector opening time and also fiddle with the timing ....

Thanks its great to be apart of this

[Gelf]

Just ordered some Denso Iridium plugs to replace my Bosch 3 earth electrode plugs.

Standard plug gap is supposed to be 0.8mm / 1.0mm, which is probably where it was before i reduced them.

Anyways, Denso Iridium plugs are claimed to require at least 5000 volts less for the spark to jump the standard electrode gap.

[Richard L]

Just ordered some Denso Iridium plugs to replace my Bosch 3 earth electrode plugs.

Standard plug gap is supposed to be 0.8mm / 1.0mm, which is probably where it was before i reduced them.

Anyways, Denso Iridium plugs are claimed to require at least 5000 volts less for the spark to jump the standard electrode gap.

I am not really an expert on plugs, all I could remember it when I was playing with engine some five to six years ago, a standard plug is fine. I used to use get the single electrode type and I can play with the gaps easily. I rerely used the cold plugs because it fouled so easily.

These day, there are some many choices but as far as an engine's point of view, thery all work equally well.

It will be entirely up to you what plug is most suitable for you, but please before spending out a great deal of money just try the typical commercial low cost ones- you may be pleasantly surprised.