Quote:
Originally Posted by hotrod
I agree I think trying to run ideal ignition timing is not as popular as it was in the past. I still think you should try to stay as close to ideal timing as possible.
Food for thought, the aircraft folks probably have done more testing and development on high performance piston engine in high load environments than all the automotive folks combined.
Many of them have timing fixed near ideal timing for max power. The way they handle max power for take off is they richen the mixture until the engine runs rough and then crank up the boost to the maximum recommended manifold pressure ( just short of det).
I think we should look more at managing boost pressure curves and less with playing games with the ignition timing.
I think the issue is it is much easier from a control system point of view to solve problems by pushing the timing values all over the map. It is much more difficlult to get fast acting stable boost control with enough head room so you can reach knock limited performance at high rpm with boost rather than ignition timing.
Most street turbos simply can't deliver knock limited boost at high rpm.
So they fake it by jacking in a lot of ignition advance, and create an electronic variable compression ratio by lighting the fire a bit early. It works to a point, but in theory it should not produce as much power as maintaining ideal timing and running the boost necessary to reach the knock limit.
Larry
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I just wanted to highlight what I believe happens with the Mark 5/6 VW Golf GTI and the Focus ST; both have the Borg-Warner K03 turbo charger.
With the stock wastage and stock inter-cooler (those would like to believe) is poor are cooling the stock turbo when average off the shelf tunes are employed that removes the timed over-boost and makes that max boost (21 psi in the Focus ST's case).
I am running the car right now when drag racing with 40% Ethanol mixed with 91 octane fuel (California). I've seen max of 26 degrees of timing. Once the car reaches 210 degrees coolant temp, it reduces timing by 9-10 degrees and I loose about 1.5 mph in trap speed.
With an aftermarket internal wastgate, it's no so much how much more boost you run, but how long you hold it. On the stock WG that's about to 4100 rpm at my tuned boost of 23 psi and bleed down to 15 psi, a product of the stock spring in the WG.
With a Turbo Smart IWG with the standard spring for this car, it will hold 20 psi. The problem is that the turbo creates much more heat doing that. To combat this I know of two tuners of the car that tried this -
One complained about having to use increasing amounts of ethanol mixed with the fuel in order to keep the timing they increased initially (tuned car), at that point 30% (E30) and still got some knock, so they kept turning the boost down via the wastgate solenoid until they reached about 16 psi.
That's ironic because that's about where I am know. I maxed out the pre-load on my OE wastegate to about 3 mm. The car will hold 23 psi about 700 rpm longer.
The result is I picked up 1.7 mph with full timing restored (car about 200 degrees after my burnout). I know exactly that much because I did another pass about 30 mins later which is not enough time to let the car cool, and it went 100.44 mph when it previously went 101.96 mph.
I should mention the car is stock ATM, it only has a tune. A car with a 91 octane tune will barely crack the century mark at the drag strip, but most run 98-99 mph.
I did that with my base E30 tune (99.82 mph) and with a bit more timing advance on 40% ethanol it's run 100.25 mph. The truth is the car could have run 100+ mph at any time. I've only had five months and it has 30+ passes on it but I am just figuring out the proper shift points.
Anyway, the other tuner runs a Turbo Smart IWG and has achieved the elusive 300 whp mark with 35% Ethanol.
He won't divulge how much boost he's running or how much boost he's holding (I asked). He sent me a message that if I replaced my current tuner with his services he would spill the beans but to only paying customers. He didn't say the last bit like that but it was implied.
I purchased the same IWG and added W/I (AEM) to be able to push the stock turbo at least as far as he was able too. It's also the reason I went pre-turbo and post inter-cooler with my W/I system.