680cc+stock computer?

[89turbosupra]

Can the stock computer handle 680cc injectors in closed loop? I will use a safc for my tuning but the computer will compensate for my changes is my understanding. I will be running a sp67 and rather not go to a standalone yet. Will the maft pro handle these better then the lex and a safc?

 

[MDCmotorsports]

If you go lex & safc you should do fine, but I also suggest a good quality AFPR and at LEAST a walbro.

 

[89turbosupra]

Yes, there will be a walboro (maybe 2) and a AFPR, but I was just worried about it idling bad because it couldnt control the large injectors. I dont really want to use 550's because that would be pushing them past the recomended duty cycle, but I know the computer can handle those with the lex afm.

 

[Doward]

I, personally, wouldn't. That will skew your timing even further than the Lex/550 mod. Also, part throttle, under boost, you will find the ECU doesn't think you are boosting - so you'll be holding that 14.7 AFR under 8-10-12psi of boost.

Think about it, before deciding.

 

[Zazzn]

Scaling isn't as bad as you think doward.

you could use emanage to do an injector sizing fix which basically rescales all signals down what ever you have set automatticall.

 

[Doward]

It's really in a very narrow scale it bothers me - the larger the injectors you use, the further you can push the turbo at part throttle, before actually getting open loop mode + boost enrichment

 

[dbsupra90]

part throttle boosting is a bad idea to me anyway. regardless of what size injectors you are using. small turbo and small boost you can get away with it. but put on a big turbo and run 15psi at 14.7:1 and you are gonna have some issues.

with that being said, ive ran a few diff supras w/ 680cc + piggybacks for years. best thing to do is use an adjustable fuel pressure regulator to set base fuel pressure for mainscale adjustment. that will not effect the ecu/timing/etc.

 

[89turbosupra]

So what would you recomend doward? A full standalone?

 

[89turbosupra]

dbsupra- From what Ive heard you never want to scale +or- 15%. Any other fuel adjustments you need should be by fuel pressure and not the piggyback.

 

[bountykilla0118]

dbsupra- From what Ive heard you never want to scale +or- 15%. Any other fuel adjustments you need should be by fuel pressure and not the piggyback.

I agree reduce the fuel pressure across the board and then add fuel with a piggyback

 

[dbsupra90]

the way i tune is do a baseline run. then i see how far off i am from having a flat a/f. at this point, im not real concerned what the a/f is so long as its safe. i shoot for flat first. if its way off, i do some tuning on the piggyback to try and flatten it out. then i use base fuel pressure to move the entire curve to range i want it. then finally tweak the piggyback to fine tune. i try to keep the piggyback scaling under 20%, but usually shoot for 10-12% range. be careful cranking fuel pressure too much. if it is too low or too high you can run into fuel pattern problems.

 

[Doward]

Even when you reduce the fuel pressure (which reduces the effectiveness of the atomization of the fuel nozzle, btw), you'll be adding more fuel per unit airflow vs stock.

I like that the MAFT-Pro allows you to adjust the timing as well as monitor it - I feel this is safe for 550s or 680s. Is it optimal? No. But it's FAR better than the Lex/550s + SAFC, IMHO!

A standalone should be looked into, when you are pushing 500 or greater hp, as a general rule of thumb, imho. The MAFT-Pro will handle all normal needs - and this is what I would recommend to you. You can just scale and go (ala Lex/550s) or you can be safe, monitor timing, and find out how much timing you need to pull, to bring it back in line with stock (this is the route I am currently on)

 

[Supracentral]

Can work.

Should work.

Have seen it work.

The path Doward describes is the safe path. It will work. Everytime, without fail, and without risking the integrity of your engine.

The other methods, all can/will work. But they are less safe, to one degree or another.

I've seen guys may 21 psi passes on the dyno @ 15:1 or leaner and not blow a motor. That can work too, but I'll be damned if I'd ever try it intentionally...

 

[89turbosupra]

I was not aware that the maft pro can adjust timing. I thought it could only moniter it. If I adjust timing through the maft pro will it also affect it in closed loop or would the computer take control and override my changes?

 

[MK3Brent]

What's the record for the lex afm and whatever cc injector?

 

[Supracentral]

What's the record for the lex afm and whatever cc injector?

Eric Varah here in Atlanta.

720 cc injectors
Lexus AFM
S-AFC

622 RWHP

 

[MK3Brent]

Okay.

I thought it was in the 600's... but wasn't sure.

thanks.


Yeah this one: