Opinions on my charge temps/ AFR please

[luke85]

Im fairly new to engine tuning and am eager to get into it a little more. I drive a Corsa with the vauxhall C20LET engine in, Currently running 1bar of boost with charge temps of about 30 degrees (at about 7 degrees outside), A/F ratio is in the low 11s. Im using a 25%M 75%W mix with the 2D system and i was looking to turn up the boost, my target is 1.2-1.3 bar.

What are the things I should be looking out for and listening for? Is knock obvious to hear? I will be taking it to the rolling road fairly soon but I dont really like it because I dont learn anything, they dont even let you sit in the same room.

Thanks for any opinions/advice

[keithmac]

Knock and AFR are the things I monitor most, if you haven`t got a good wideband AFR gauge in the car already it`s a good investment.

You can here knock on some engines, on my Mitsubishi if I heard audible knock the engine would be a gonner already though, I tuned the Golf for audible knock and that worked pretty well so it`s swings and roundabouts to some extent.

I prefer road tuning to rolling road tuning to be honest, 1/4 mile running is a good option for datalogging and tuning at higher loads/speeds.

[luke85]

Thanks a lot for that keith, Im using a innovate LM-1 at the moment to look at the AFR. Just had it up to 1.2 bar and it looked as if it was hovering about 12.0 but until I get home and look at the log I cant be sure, its a case of hold on and try to keep it straight in 4th gear.

The engine sounded perfectly sweet to me but I am concerned about listening out for the knock, I think i might leave it as it is and let the RR guys have a look

The charge temps still seemed about 25 degrees C but its a cold night tonight, about 5 degrees outside. Does this mean that if we have a 30 degree day in summer I will be seeing 50 degree temps?

[keithmac]

WI works to better effect when the ambient temperature is higher and the IC`s are less efficient at dropping the charge temps, if you`re using methanol as an octane booster the change in temp may be less of a factor?.

I tuned for 12:1 afr on the supercharged Golf with WI active and tuned for audible knock (or lack of it!), the car with that tune did a full trackday at Donnington and lived, you`ll never hammer a car as hard on the road so it was a good solid tune.

You can rig a knock sensor up to a laptop or amplifier and listen for knock through headphones, or if you have access to diagnostics on the cars ECU you can keep an eye on the knock sum which is a better way in some respects.

If you tune in winter you need to keep an eye on things as the ambient temps get higher in summer and may need to retard the timing slightly or up the water/methanol rate to keep knock at bay.

Another good way to check the tune of the engine is to pull the sparkplugs after a hard run and check the tips, I believe specks of metal on the electrodes are a good indicator of knock, it`s a bit of the piston top stuck to the plug!.

Another point is not to completely go with what the Rolling Road guys say unless you have proof they have good reliable tunes on the same engines, I read recently a lad with a GTO had a RR tune done with no knock monitoring at all, just AFR and that`s near on fatal for one of these engines..

If you can do it safely road tuning is a good way to set your car up, you can spend as along as you like to get it perfect and all it costs is time and petrol.

[JohnA]

Luke,

When I was tuning my LET it hit peaks of 2 bar with no detonation - on standard compression ratio.
This would be impossible without WI.

The trick was to make sure that everything else worked as it should: injector flows matched, cylinders having similar leakdown figures, that sort of thing.
Then add water mist in a way that all cylinders receive the same under load conditions. You need even distribution of fuel, air and water mist. So nozzle locations become very important.

Charge temps can be deceptive - you see 30C and feel safe, while cyl #3 (or whatever!) is running AFRs 15:1 (and the wideband is showing 12:1, which is an average) :wink:

Precompressor injection works very well too, without it I doubt that my engine would have survived over 1.5 bar for long.