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View Full Version : SR20det GT2871r ignition timing and high dutycycle? Ideas?



Laurelturbo
03-31-2009, 08:27 AM
Hi,

Ive got a SR20det with the following mods:

Tubular manifold
GT2871r .86
Large intercooler
Walbro fuelpump
Megasquirt stand alone
740cc injectors
Stock cams
Stock internals
Oil cooler
Upgraded clutch


My timing map is basicly just the enthalpy basemap with some extra timing too it, as posted in a picture:

http://i601.photobucket.com/albums/tt96/Laurelturbo/sr20DETIGNITIONTIMING.jpg

Now first off, I had my own timing map before I stumbled over enthalpy`s one day. I had about 5 hours of tuning on it, and it was much the same as the enthalpy map, except for less timing i low\mid range.. had just tuned all the "surrounding" functions, like crank pulsewid, getting a good idle, making it run properly, and so on. I use a simple headset on the Knock sensor, and had yet too come across any knock.

I then uploaded a enthalpy timing map, that really helped my spool up and low rpm power, thanks alot to enthalpy!

Now, I just upped my timing in the max boost area a little, and works like a charm, but I think Im using way much fuel? The 740cc injectors are at 75% at ~20 PSI!! Isnt that a bit much?

Does someone else have setups like me and can post experiences, maybee timing maps and pulsewidts?

Im doing some more tuning next weekend (waiting for some parts now), and hoped to get fresh Ideas to try out with. Also ill hit the dyno one of the next days after that, and Ill definetly upload my dyno sheet!

Kingtal0n
04-01-2009, 03:28 PM
around 15-20psi of boost I would run no more than 10-11* of timing. If you like do this on a dyno and watch you probably wont lose any power and the safety margin gets much better. If you have an EGT gauge you can dial it even closer to ideal...

always time it first then pull fuel for your a/f. if you see lots of fuel going in for what seems like not enough power you may be needlessly wasting it to keep the engine out of knock range. IDC what the gauge says, if you do the equation (HPXBSFC=lb/hr) and you see your bsfc is really bad, then you know either A: your fuel pump is giving up or B: your tune needs help

Laurelturbo
04-01-2009, 05:36 PM
around 15-20psi of boost I would run no more than 10-11* of timing. If you like do this on a dyno and watch you probably wont lose any power and the safety margin gets much better. If you have an EGT gauge you can dial it even closer to ideal...

always time it first then pull fuel for your a/f. if you see lots of fuel going in for what seems like not enough power you may be needlessly wasting it to keep the engine out of knock range. IDC what the gauge says, if you do the equation (HPXBSFC=lb/hr) and you see your bsfc is really bad, then you know either A: your fuel pump is giving up or B: your tune needs help


Hi,

thanks for your reply. As Im yet to dyno it, I dont know the power or if anything goes to "waste" here....

I see where you are going though, but my AF ratings are not as low as you should think. At ~20PSI its at ~11.5. No knock and ~16.8 degrees timing.
Now, taking it all the way down to 10-11 is something I can try if you really think its a good idea, but Im sceptic too that making the same power? Ive felt that for every degree I raise it, its given more power..?

If you on the other hand talk of the tuning method of less ignition timing with a leaner mixture, giving the same pressure peak as a more advanced, but richer mixture, then I understand you better. But if so, I would like water injection for cooling.

Can you explain your background for the lower timing better please?

PS - Im running 98RON Pump gas.

The fuel pump issue.. Well, maybee its getting week, but its not old, and a walbro 255 is quite solid? Ill look into it!

Laurelturbo
04-02-2009, 06:34 AM
I figured I could give your formula a fast try. As I hope to reach ~350-370 flywheel hp, I had some numbers to play with:


HPXBSFC=lb/hr

740cc \ 10.5 = ~70.4 70*0.7= ~50Lb\hr *4 = ~200 --->>> Injected fuel at 70%

HP X BSFC = LBhr

BSFC = LBhr \ hp

BSFC = ~200 \ ~370 = 0.54 -- Not bad

Lets say 350 FHP 200 \ 350 = .57 --->> More realistic

So is there a BSFC to compare with out there? Whats "~Normal" on similar setups?