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Old 10-22-2012, 02:28 PM
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Originally Posted by F-BIRD'88 View Post
If you cannot under stand locked fixed timing that does not move 36deg BTDC for start up. How the fug do you think you will understand and program the computer timing tables???

The timing required will stay near 0 change right up untill boost is add at which point the motor needs LESS timing

same at idle as at WOT but must retard as blower boost comes in to avoid detonation on pump gas.
What is frigginhard to understand.???? the computer has to have a reference point.
It has to be somewhere inorder to move from that somewhere.
That somewhere is 36deg BTDC. Since you do not have a pressure sensor to sence blowermanifold boost to retard the timing in reference too, the computer is as dumb as you are.
So then RESET the ignition timing (fixed) at 26deg BTDC to start testing under boost @WOT on the dyno and creep up on the tune up.. 26 to 32deg BTDC

You have something that you don;t need and have no concept on how it needs to be programed.
The only processor you need is a spark retard box. Go buy the jets nd the power valve plugs I listed before testing. Get someone wit a clue to set them ignition timng. set all tables to 0.
No change. Run the engine at 36deg BTDC. Then move the crank mag pickup so the timing is 26deg BTDC. (using a timing light) Now you are reay to start WOT testing. The computer tables do no tneed to be set up because YOu don;t have a clue what the tables should be anyways.
A roots blower motor is not like other motors.
You wil make tmore power and it will run better with blower carbs and a simple ignition system with boost retard.
FOR A fraction of the money. and a fraction of the bother. YOU DON:T HAVE MONTHS of engine dyno time and chassis dyno time AND $10000000 's to spend on dyno ,drive mode testing to create a fuel map or a timing map etc etc etc.
You are wasting your timing and money for nothing and are hell bound to end up witha damged burned up motor. Find someone who has a clue as to how these roots blown motors actually run.

I don't have the time or patience or the 10pages of text to explain how the world works, how engines run, how roots blower motors run and why they need 36deg timing at idle. ( Stick you head near the carbs and wack the throttles open when the blower is cold with the timing set as you think it should be and you will get lesson #1 on blower motors.
You will have all that time till your hair and skin grows back to think about what just happended. (if you don;t damage the blower rotors from blower back fire. You will then run out of money and buying pistons trying to figure out why I say to start timing at 26deg BTDC under boost on pump gas. @ some 14lbs boost. ( a really dumb boost level to start tuning at.
GET SOME RACE GAS. Consider yourself for---warned ...

36deg BTDC for start up/warm up 26 to 32 dg BTDC for testing under BOOST.

Get a distributor ....lock out its mechanical advance curve and stick it in the motor.
A computer is just a dumb machine unless you have a clue how and why to program its.
cheers t bird , think we will have to agree to disagree on some of that . from what you have posted i do thank you for the figures and timing numbers. having not known each of our back grounds or knowing each other personally its hard to just read something off of a post and take it the way its meant . ( or how you mean it ) i feel i may have angered you . sorry if thats the case , i did ask you for some exact figures on timing. i do know how to progrmme the ecu and if you knew my back ground you would know i could. i do have a boost gauge in the manifold ( thanks for asking before presuming i didnt ) currently the ecu reads firstly from the tps and then the boost. this may be changed when the dyno shop tune it . these guys at the dyno shop do know how to tune blowers - they tune the drag cars for the uk santa pod market . the reason why i am asking is so I know and not some shop where i spend lots of money.

today i visited a friend who is building a ex formula 1 engine for a swiss client that was run at moanco and lemand this year. he also had a v12 aston martin engine on the bench for a rebuild. and numerous methanol tunning engines to service for next season. he also backed up all of yours and others timing figures.

if you can give me some exact figures like others are trying to do that would be most appreciated. as i said before i will not run this until its set up correctly and something the ecu will not allow and will turn off ,

the below is a rough guide as each engine will require what it wants

i have been told to crank from 0 to 450 rpm ( start up programme ) @ 10d then 10d to 20d up to 1000 rpm being the start of my ign curve- then a sharp curve from 1000rpm to 1500rpm @ around 28d then from 28d @ 1500 rpm to 2000rpm at 32 d then a flat curve ( which you refer to as locked out ? ) the reason why i am reading tps first is so when the boost builds we can dial in the boost paramter reading to scale down the ign to compinsate for the given amount of boost we have , also sometimes engines will be under boost but no throttle ( load ) how does a engine ign deal with that ? so thats why the tps is read first then backed up by the boost guage under the blower.

this all may change but its how its running now.

cheers shaun
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