Fd3BOOST

I have searched and searched and I have many gaps in my understanding of engine tunning. I can put together and disassmble cars with the best of them but I am totally lost when it come to tunning. I mean some **** seems to be be so basic and yet I don't know it so please help me understand some simple concepts. I want to understand so i may learn it for myself.



Ok 11:1, 11 is fuel and the 1 is air?

What is the significance of knowing what the a/f is as exactly.

Is 11:1 universally the standard for all engines?

What would be the diffenrec between 11:1 and 10:1?

Pretend I don't know **** for a second.



Ok next the basic theory to tunning a rotary is....



advancing the timing and subtracting fuel till you detect detonation.

Then retarding the timing a few degrees and adding fuel in 2% incraments until detonation is no longer present correct?



Also when adjust maps, What exactky is the procedure?

Do all rpm ranges need to be adjusted?

Are the adjustments made only in idle/part throttle and WOT?

Does the fuel curve have a set guide line that needs to be followed?

If so please explain.



Does anyone understand what the hell i am trying to say?

Where the hell is Steve Kan when you need him

Please help me not feel like such a dumbass..



-D.

tfhuth

I'll start .





11 is the air and 1 is the fuel .



Tom

tfhuth

I think Tony ( Badog ) would be a great wealth of info, it he were willing to post here.





Tony ?





Tom

j9fd3s

11:1 is the ratio of air to fuel. so its 11lbs of air to 1 lbs of fuel. this is measured by the oxygen sensor in the exhaust. although there are other ways to measure it.



the afr number by itself doesnt mean a lot, basically on a motor with no detonation you want the mixture to give either the best power or economy, on an rx7 we also have to think about safety.

different motors will want a different afr. the nice thing about afr's though is that it gives you a number to compare lean vs rich vs something in the middle.





when you play with maps if you have all the tools you wanna tune the fuel first and then tune the ignition with an egt.



the fuel and ingnition does not have a set curve to follow, it will depends on the power curve of the motor. vosko was telling me about that the other day, his car wants a ton more fuel over 6k than it does under it. you just want to give the engine the afr that its happiest at



the idea behind ignition timing is to get the biggest part of the pressure rise in the chamber to happen right after the piston/rotor passes tdc. if the timing is retarded you loose efficency because the chamber volume goes up and you dont get as big of a "push". too much timing and the piston will have to push against the pressure in the chamber.



if you can, play with this stuff at idle and light load see what it does, if youre not under boost its hard to do any damage



mike

Fd3BOOST

So mike is TDC, exactly that?

Top dead center of the apex seal straight up at 90degrees?

If not then how does one determine top dead center?

How is an EGT used to tune ignition specifically?

And am I to understand that 11:1 is a more lean condition than 10:1?

And how do you determine afr's?





Also,



Thanks for helping. I'm gonna be asking alot of retorihcal questions so bear with me.

rfreeman27

yes, 11:1 is more lean then 10:1

j9fd3s

tdc is the point where the face of the rotor is closest to the spark plugs.



if the timing is too retarded combustion happens too late, thus its still burning in the manifold = higher egts.

if its too advanced you get hight egts too but i dont know why, i'm gonna tyr and dig up a couple of articles, i dont know everything either



yes 11:1 is leaner than 10:1



you can determine afrs at least 3 ways



1. with an oxygen sensor in the exhaust. this picks up oxygen in the exhaust gas and generates a voltage. it can be fooled by misfires, a misfire looks like full lean to an 02 sensor.



2. on an engine dyno they can measure the air and the amount of fuel going into the engine. i dont know a lot about how this is done but it strikes me as better bcause o2 is not the only thing coming out of the tailpipe.



3. with a smog machine, it gives you all the data if you know how to read it



dont worry about it, the more you know the better off you are



mike

RussellTT94

on an dyno, they use a wideband o2. it's a five wire o2, which is much more accurate than a 2 wire. i believe thats the only difference from a regular o2.

j9fd3s

on an dyno, they use a wideband o2. it's a five wire o2, which is much more accurate than a 2 wire. i believe thats the only difference from a regular o2. [/quote]

oh sorry i meant engine dyno, where they can acutally measure the air and fuel as its going in to the engine



mike

RussellTT94

ah, i have no idea how those work