For Newbies:

Info from tuning an 88 Vette after swapping to a 730 ECM.

So I thought I was being smart and playing with my injector constant until I got several BLMs over and under 128. I figured the middle ground was a good place to start tuning.

Well I have been working my way up in RPMs and get to about 3200 at 60 MAP. I'm running lean, so I need to adjust the VE up. Well the value is already so high that I don't have enough adjustment to make it high enough. I need a value of about 105. 100 is the max. I then looked at several other nearby areas and I am in the same boat.

Since in the default table your lowest VE values are proably in the 60's and your highest are in the 80's - you have a lot more room to take out fuel than to add it.

In hindsight, it would probably be better to have be universally rich so you have more room to take fuel out by lowering the VE tables.

So basically, this is a "Don't do what I did." I now need to reduce my injector constant and start all over.

For gurus:
Any disagreement on the above comments?
Also, since my basic VE shape for that areas I have tuned should be right, is there a correlation between the injector constant and the VE tables? Like could I drop the injector constant by 10% and scale all the VE values by 10% and be close?

 

have you tried to raise your fuel psi up a few points? You could do that, then check your BLM/INT values.

 

Thought about that, but I'm already at 50. Don't really wanna go much higher. Its not a big deal to drop the constant, run some logs and rough it out again.

 

There is no easy answer on this on.
Being al 50 and still lean, not a good place to be.
I'd manipulate the injector size, and reduce the FP some and see where you're at.

I generally will do a calibration about 2/3s, and look at where I'm at as far as VE and injector size.

If things seem OK (and this is just something that comes with doing them), I'll either finish that call, or start over using a different injector constant (but save the *bad* .bin for future reference).
Then again at what would be 2/3 done see where I'm at.

You just have to experiment (spend time) to see what you engine wants, and how to give it that.

Just as a FWIW, right now I'm at least 30 chips into balancing the PE vs RPM, and PE vs TPS to balance out what my engine likes best. And I'd bet no one would have complained about what it was like before I started, but the engine is letting me know what it likes.
Just a lil secret, in using the PE RPM more so now, I've been able to decay out the throttle follower some, which has really crispened up the blip the gas in gear, *pounce* the car can do.

YMMV

 

I had the same thing to happen to me a real good 406.Had 30pd
svo at 48 psi,every thing work pretty good up to about 3400 rpm.
Good not get rich enought.was max inj,And thanks to Grumpy he
posted on inj. about GM useing 22pd inj on 350 about 250 hp I guess.I thought I need to double,so I got some 43.5 and things or looking good so far.By the way the 30 had contant set at 26.

Grumpy have any opinion on 09 inj.

Dale

 

009's

Actually, I've never meet an injector I didn't like.
Some folks bad mouth certain injectors becuase of there short PW opening times, and how they canget errattic, at idle. Often these same folks don't know to work with the battery voltage corrrection to account for that.

NOTICE:
The battery voltage corrrection is to account for opening times on the injector, so if you change injectors, don't be at all surprised if you have to modify them SLIGHTLY to get the prefect idle. If you trying to get a saturated iinjector run at 1.0 msec or less at idle you will have problems, but that is a wrong selection issue, not an injector problem. This is a generic answer and applies to the 009s as well as any injector

 

Grumpy,

I have been in the process of tuning a split set of 80/90# injectors on a Xfire with good results. How can you tune for smoother idle on a 7747 using the battery voltage correction factor. Using Tunercat, I don't see that table available. Is it available using some other tuner?

 

There is always something missing on commercial editors. They just have to make them manageable.

When I'm doing a recal., I always, try to have a hac, and perferably a commented hac handy.

On thing really nice on GMEPro is that there is a direct edit for hex editing. So if I run into something not in his editor I break out the hac and find what I need.

How can you get the idle even back to bank with two ifferent sized injectors?. Hint, GM couldn't.
That's why I went to parrarel routing of the fuel lines.

 

Grumpy,

The Xfire has always had different size injectors on front and rear TBI's. 62#front/66#rear. GM counted on the fuel pressure differential as a means of equalizing fuel output between the two different sized injectors. Based on some calculations I did, GM must have determined that the fuel pressure drop between front and rear was .5psi. However, the stock injectors were running lean at WOT given the modifications I have made and I needed more fuel. I will most likely go to parallel plumbing of the TB's as you have done, but thought I would exhaust this option first. I am on my 11th iteration of a bin file and idle appears to be good at 800rpm with INT(currently tuning with BLM's locked) averaging 123 at MAP voltage of 1.7-1.9. IAC counts are 13-15. I am using a 92 BPW constant for the bin. Seems to work better than 100 for my setup. So far the INT has proven to be much more consistent throughout all rpm ranges than when I had installed 90#injectors in both TB's. But I haven't done the plug reads yet, so the jury is still out.
I am certain you are right about the parallel plumbing on the TB's, but as you have said yourself, this tweaking can be addictive. And some of the fun is the journey of discovering things on your own. You did it when there was no other choice and no one else around to help. And we are all indebted to you for that.