Time to upgrade TB/MAF/Injectors?

Zero Signal said:

I did some datalogging recently and recorded a few runs to 90mph. The MAF is up to 4.75V which equates to about 700cfm with the stock transfer curve. Assuming the stock transfer curve is accurate, does it look like it's time to start upgrading the MAF and TB? The FAQ section says the stock TB is rated at 515 CFM, so will it be worth the investment at this point? The MAF still has another 120 or so CFM left in it, but will I want more headroom and a new MAF? Is the stock one very restrictive?

I'm also logging about 85% DC on the stock injectors so I'm starting to think if I upgrade the TB and MAF, the injectors are gonna need to go too I thought the 19# injectors were supposed to be good to 300hp and I know I'm not at 300hp, so what's up with that?

EDIT: Come to think of it, Grady has the stock TB and MAF and he pulled 293hp/300+tq so maybe it's not worth it yet I'd honestly rather save the money to convert the rearend to a 3-link.

Click to expand...

My first thoughts about your concerns would be to point out that often quoted statement of "19lb inj's will support 300 hp thing" is very misleading. Those formulas deal with FWHP and we folks in the Mustang community tend to think with a RWHP mindset.

My feelings about the importance of the stock inj's, maf, & tb when modding our Stangs are along these lines.

In order of priority I would upgrade them like this:
1) inj's * 19's will become inadequate before maf or tb
2) maf * it supports the same air flow as a Cobra with 24's
3) tb * * until a great deal of air flow is generated, gain will be small

If you don't tune, then of course, you will do 1 & 2 together.

You talked about me using the stock maf and even though that is true

The main reason I could do it was self tuning gave me access to all options available which then allowed me to get the most from the stock parts.

Some of those options to consider are the following:

Remember #1 from above
1) I could use 30's for plenty of fuel
2) I could gain more head room in the maximum maf voltage value
Remember #2 from above
3) I could use the GT maf curve with the Cobra file for greater flow
4) I could gain more maf curve flow with these two methods.
* a) Kill the high speed fuel enrichment
* b) Lean out the high end of the fuel table

You talk about cfm a lot and in the past, I've tried to point out to peeps the maf is all about air flow and not about fuel so ............

Air flow is most certainly important here
but
After you deal with the things we talked about above, that air flow is gonna change from the perspective of the pcm ..............

Don't You See

ANYBODY that can't see what I am trying to say here PLEASE PLEASE feel free to speak up or DON'T FEEL INTIMIDATED or anything like that
because
This stuff we are talking about here is one of the most miss understood topics about our hobby IMHO and we can always hash it out it if we need to.

Now ... While the cfm or KgHr air flow is important ..........
we can and most likely will change those values when we setup our desired final af ratio.

What we CAN'T change is the maf voltage range of 0.0 to 5.0 volts!

That is were I started to feel the pinch from the little stocker maf. Doing everything I could do to optimize the tune I still pegged or was right at the door of pegging the little maf with a mv value of around 4.9xxx volts.

You said you were at about 4.75 mv at max rpm's and I'd be willing to bet you could drop that down a good bit if you had your wb. So you could very well gain some head room with the stock maf.

Summing up here ..............

Some of this stuff will not be available to those who don't tune
however
If you can grasp the basic principles of what is going on here ...
You will understand why your car behaves like it does after mods that affect fuel, and airflow.

I hope I've been able to put this stuff up in such a fashion that makes sense to everybody and again, if anybody wants to talk more about it ..... we can do it.

Grady