looking at buying a vl turbo with engine upgrades. i asked the owner the power and his response was 200kw on 10psi with lots left in it, when it was dynoed only revved to 4grand because it was leaning out up high. i know this is probably a beginners questions. but could someone explain what leaning out up high means. the owner said to fix this i'd need 550cc or bigger injectors a new ECU and a new tune and should pull over 300kw easily sorry for the beginners questions, don't really know too much about the engine side of things

Its an oldie but what the hell, Im not doing anything this afternoon. For an engine to operate it needs something combustible to create energy to push pistons up and down the bore, rotating the crankshaft which makes your car go. Now as we all know, We need fuel, oxygen and heat to start a fire and its no different in an engine. OK, Air fuel ratio is the direct ratio of air vs fuel in the cylinder. so 13 to 1 is........ 13 parts air to 1 part fuel, 10.8 to 1 is.......... 10.8 parts air and 1 part fuel 15 to 1 is .............15 parts air to one part fuel... Now the fuel "value" stays the same, its the oxygen content changes so.... 15:1 has more oxygen than 13:1 .........so 15:1 is leaner. Now this is where it gets interesting.... at 14.7:1 (stoich for pump fuel dependant of the density of the fuel at the time) All the fuel and all the oxygen is burnt by the combustion. Leaving us with no hydrocarbons (unburnt fuel) at the tail pipe. Now if you run your mixtures leaner than 14.7:1 then you burn all the fuel, but have oxygen left over. This creates more heat due to the oxygen being so combustable. Having too much air (oxygen) or not enough fuel for the oxygen in the cylinder can increases the heat to points that may not be able to be maintained by the engine. Just think of an oxy torch, What happens when you add oxygen... it gets realy hot very quickly Now on the flip side, if you run 13:1 (richer) all the oxygen is burnt, and the added fuel not only help replace the oxygen with a mass that will help the engine run cooler than hotter, the evaporation of the fuel directly helps keep cylinder temps low. Now the magic question is..... how lean is too lean. Well really, its a case by case basis. 12:1 on a 300hp engine may leave you with an egt of 750c, where 12:1 on the same engine at 400hp egt may be 900c. Thats pretty easy to follow.... but EGT will rise and fall in direct relation to ignition timing. The more advance you run, the lower your egt will be. The more retard the higher your EGT will be. In saying that the more advance you run the more heat is consumed by the piston. So I hope that kinda makes sence, O yeah..... 550cc x 6 of fuel will not support 300rwkw. You need or should have 650cc of fuel for 100 crankshaft horse power. Now this is at a brake means fuel consumption (BMFC) of .65 so that means if you need to run 10:1 you can. if you need to run 11.3:1 you can. so 300rwkw = 400rwhp so add around 25% for crank HP and we are at 600. now if we need 650cc for every 100hp we have 3900cc all up. divide this by 6 cylinders and we have 650cc per fuel a min This is not.... run her at 100% duty, and look for 12:1 ish and hope for the best. The problem with this is if the car is tuned in a 35 deg dyno cell, and the air fuels are 12:1 then what happens on a 10 deg night when the air is more dense.... you guessed it... its now like 13.5:1... and at full noise at extended periods (hi way racing etc) your egt's will be up there.

Leaning out up high, refers to "high" in the engine rev range. So in very basic terms, the higher you rev engine, the more fuel it will need to keep running correctly at those high rev's. Your injectors are small and can't supply enough fuel to allow the engine to run "correctly" when "high" in the rev range, (once you pass 4000RPM, without the risk of blowing up) The solution is to fit bigger injectors to allow the engine to get the fuel it requires at higher RPMs (ie,over 4000RPM) A new ECU (aftermarket) may allow for better tuning once the bigger injectors are installed Quote: Originally Posted by HYPED6 The problem with this is if the car is tuned in a 35 deg dyno cell, and the air fuels are 12:1 then what happens on a 10 deg night when the air is more dense.... you guessed it... its now like 13.5:1... and at full noise at extended periods (hi way racing etc) your egt's will be up there. Just interested in if you use a set formula/values to compensate for this, such as set the ECU to add a certain percentage of fuel per deg/s drop in air temp ? MT

No set compensation, when setting up AFR' corrections, you need to take into consideration the temp of the block, the inlet manifold,cooler piping etc to get accurate and consistent reading. You really need a mix of engine temp and air temp to get it spot on. Or tune the car in a condition where there is more than enough fresh clean air than the engine can consume and contaminate with heat and exhaust emissions.

So how do you work out/estimate what all those temps (block,manifold etc) will be on a cold night when most cars are Dyno tuned in a single (hot temp) day ? MT

Well, you work on the side of caution, and tune every engine as it needs. Run the thing a little bit richer than necessary at heavy loads, As most tuners do. This shouldn't hamper the power to much, well not as much as incorrect timing. Some good EFI systems have setups like Fuel over speed over engine speed over throttle position over air temp.... With good setups like this a you can add x amount of fuel, at over 150kph, over 4000 rpm over 70% throttle, so when the car is being help at high load for extended periods it can add more fuel to help control combustion temps. Coolant temp is pretty much the big one for a turbo charged (or centrifugal supercharged) car. There is a small gap between the engine reaching operating temp and the inlet manifold heating up where the mixtures may be a little leaner than expected. This is only very noticable at very light loads, where milliseconds are quite small so 10% is a lot of fuel. At full throttle, like 16ms, The difference between 16.00 and 17.60 will be minimal. Measurable but minimal. Some supercharged cars can see inlet temps over 90-100deg C So with these they need to be setup correctly to ensure they dont over fuel massivly at light loads and high air temps but dont lean out at heavy loads and hi air temp. Can be a little tricky to setup, but once you have the correct correction for that air temp, it will be the same every time. Inlet air temp in some applications can be used for small alterations, A little leaner when hot, a little richer when cold to keep a consistent AFR. Both These should have safety margins in place too. Like, if the running coolant temp of an engine is 80 - 90 deg c then at 110 deg add 10% fuel, at 120 50% and 125 75%. This is Great if you blow a head gasket.... may just save your head Some original photos have not been recovered yet.

Quote: Originally Posted by HYPED6 Some good EFI systems have setups like Fuel over speed over engine speed over throttle position over air temp.... yes..i musn't have i good one i guess (ha) ...totally on the same page wth regard to the "high" air/intake temps and fuel, its the other end of the scale i am talking about, on my ECU the increments in the air temp map i found are not really practical (in the cooler end of the scale) I have found that i can see 10deg intake temps on a cold night on cruise, i run the eng slightly on the rich side so no need to add fuel. obviously if you are making boost you may wish to add more fuel at colder temps, but as soon as you even make a couple of pound under light pedal then obviously intake temps rise so again, no point adding fuel . so when you said "and at full noise at extended periods (hi way racing etc) your egt's will be up there" are you suggesting (use my car for example) my now 10deg intake temps on cruise ,(that will obviosly rise as i make boost), could actually "fall" if i stay on the pedal for extended hard periods/speeds, that the cold air may bring my intake temps down below 10deg at some stage (even though the engine is hard on boost ?) I can understand how if im "cruising" at speed (no or little boost) wind chill etc could bring down temps, but just wonder about at "full noise" if it could ever get that low unless i live in Antartica ? and if so ,knowing that i can't easy test what happens,what changes or % of fuel can i add for what deg of cold air, to ensure my engine wont lean out should i need to escape a volcanic eruption when im driving around Antartica (or melbourne) MT ps...... sorry 02DUBH for stealing your thread, HYPED6 and myself are just keeping it safe & warm so you can have it back should you return one day ..... honest! Did you end up buying the VL ? Some original photos have not been recovered yet.

I see what you are saying MT, but are you measuring inlet air temp pre turbo, or pre combustion chamber? With an inlet temp of 10c deg, pre intercooler of 80 deg, post cooler of 60, block temp of 90 and inlet manifold of 50-60...... your combustion temps are going to be pretty consistant, ECU's such as Autronic calculate "estimate intake temp wich can be very handy when setup correctly. Now if your block temp drops, as with your inlet manifold to say 60c engine and 30-40 inlet manifold, Then honestly the difference at full noise is going to noticable, But if your AFR's are going from say 11.1 to 11.4 and you gain 50c EGT from the AFR, but your EGT will also drop (minimaly) do to the lower intake temp. then really its not going to make much difference.... expect make more power I wouldnt be too worried about your engine grenading as we come into the winter months Some original photos have not been recovered yet.

My air temp probe is after the cooler ,about 6 inches before the throttle body Pyro probe is just after turbo o2 sensor is approx 150mm after turbo standard block/coolant temp sensor position All read from laptop/ECU programme (pyro has own gauge) I have with previous engine also seen high EGT from being "over rich" i put this down to un-burnt fuel combusting in the turbine housing,i don't recall ive seen my EGT ever go past 750c with this engine (am running heaps of timing) Quote: Originally Posted by HYPED6 Now if your block temp drops, as with your inlet manifold to say 60c engine If im reading that correct ...Could the block temp ever get down to 60c (if running a standard 90c thermostat) ? ive seen around 88c but doubt it would get almost 30c lower ? Quote: Originally Posted by HYPED6 I wouldnt be too worried about your engine grenading as we come into the winter months so i should be more worried more about my cabin heater working good then MT Some original photos have not been recovered yet.