FredR

There is the same amount of fuel in the tank but there is less energy to be liberated per unit volume consumed. 98 RON fuel is highly desirable in the stock S4 motor yet alone whatever you have concocted beneath the bonnet. The whole point of what you are doing is to get more air crammed into the motor and thus more fuel to get more power but that is not an economy measure. That you are using more fuel is probably more to do with your lack of self control -

I am not entirely sure how tuning with alcohol laced fuels works but my professional background tells this will change stoich for the fuel you are burning. Conventional gasolines run stoich at 14.7 and the 4 valve 928 motor seems to max out power at about 13. Thus if you have alcohol in the witches brew then those numbers will logically reduce thus why you will burn more fuel volumetrically speaking per BHP dropped on the tarmac.

Assuming you run something like E10 stoich will drop to 14.3 and I suspect max power output will be delivered around 12.5 so the first thing you need to know is what brew you are running.

Regarding the impact of alcohol on timing published data I have read suggest that iso-octane [that is the definitive HC with 100 RON] has an optimal timing of 29 degrees to achieve optimal piston pressure. For 100% alcohol that number drops to 24 degrees. This suggests that fuel with an alcohol content will need retarding to some extent. If you are running E10 I suspect that reduction will be about 1 degree. Doubtless we will have folks on the list who are knowledgeable in this regard.

Randy V

Strosek Ultra

I once converted a BMW six for E85. The ignition advance had to be increased to 43 degrees in order for the engine to make any power.
Åke

drnick

Hear attached should be the fuel map and ignition map pasted into XL for comment.

Both maps still need work and these are the results from tuning on the road - no dyno time. The top end is rich at 12.1:1 or lower from 4800rpm as I haven't spent much time beyond 5krpm so far. Theres lots of surprising aspects to the tuning process and its a learning curve for sure.

One thing that is surprising is the car going better with more advance - ive gotten to 28 degrees and that's as far as im happy to go by the seat of the pants but theres no doubt that it is faster with this much advance and not less.

drnick

I should add - so far zero knock at full load and only occasional knock at part throttle transients like lifting off and gear changing.

Also, for the shark tuner - it seems to want a map positively loaded at each startup rather than leaving the same instance running and editing it post hoc or disconnected from the car. It took me quite some time to figure this out.

And I cant get Sharkplotter to display values that fit with the higher loads on the ITB map - can this be done? Even so this programme is a really essential assist to the process.

I have noticed that when making a run with WOT from say 2krpm the load does not go to 100% but climbs from about 73% only reaching 100% by 4K - and the throttle is on the stops.

In terms of driving - it goes in fourth now like it did in third before.

FredR

Nick,

Sharktuner loads the maps in the PEM into the laptop upon startup.

Much appreciate if you post your maps as a PDF or JPG image document [this can be done using printscreen and MS paint].

Rgds

Fred

drnick

Sharktuner screenshots.

V2Rocket

there's an equation that outputs the "load number" taking into account TPS, RPM (dRPM/dT), MAF flow, etc.
if you go full throttle at the base of a long fairly steep hill you'll see different load numbers than on level ground/motorway.

drnick

FredR

Nick,
I can offer absolutely nothing on the fuelling map which I presume to be based on the MAP sensor addition that John made for ST2. I assume you are using the cruise map as your full load ignition map.

The thing that catches my eye is that the values in the high load range [83% to 100%] from 3k rpm to top end seem to have a somewhat narrow range. The advance required is intended to be tuned such that the max pressure in the cylinder occurs at 14 degrees after TDC. This of course is a virtual concept and cannot be measured directly without very sophisticated kit well beyond user resource- such timing is usually arrived at on a dyno. The ST2 approach is to dial in advance until we see the onset of knock. The expectation is that the faster the motor spins the more advance is needed and there may be some exceptions to the rule due to flow resonances.

On the one hand with a fast exhaust less advance is needed but on the other we look for the optimal advance the system can handle. If you have covered all the bases and that is what the dyno or testing tell you all well and good. With ITB's you probably do not have the issues the stock manifold presents due to different runner lengths. Perhaps your top end timing is a bit on the conservative side and to be fair, I do not know what to expect when using a MAP sensor albeit I have a feeling that the MAF approach to air measurement is flawed to some extent with readings influenced as may also be the case with knock sensor pings if induced by system noise that is incorrectly filtered.

Hopefully you will have some dyno numbers before too long- I suspect they will be very healthy.

drnick

FredR

Nick,

Your cam profile may well play a big part in the advance the motor wants if it is "well retarded". Just try adding advance in steps of 1 degree on the high load cells and set the knock retard step size to 1 degree whilst testing- I found that a useful feature when "experimenting". Just watch out for those funny white cars with blue flashing lights on top! My tuning was compromised by 95 RON and no dyno in the country. I understand there is now a dyno and after I did some "lobbying" a few garages now carry 98 RON- no idea if my lobbying contributed but...? I did know quite a bit about the gasoline here when I was the chief engineer at the local refinery some 15 years ago.

I am aware of the alpha N but thought it was the same as the MAP sensor- clearly not the case.

SwayBar

I think Cheburator's GTS ITB racer does 435 rwhp, so your guesstimate sounds reasonable.

V2Rocket

you've got that super cool intake manifold but i wonder if the length of those horns is tuning "in" at the RPM range you're seeing knock?
they do look fairly long.

drnick