This article made me paranoid

[Juxtapositron]

Warning !! Before you change that tune read this!


Should I be as concerned as this guy seems to think I should be? I'm throwing some longtubes on my gt500 tomorrow and I'm going to need a tune afterwards, so I was doing some research when I stumbled upon this article.

I'm really a newbie when it comes to tuning... and by newbie I mean I have as little knowledge as possible, aside from a conceptual understanding. Can someone give me the basics so that I'm not longer worried about my motor blowing up? Any info would be appreciated. Obviously, I'm going to have this professionally done but I'm concerned that my lack of knowledge will bite me in the ass.


-Jux

 

[01yellercobra]

I wouldn't worry. When the people that design the tuning software (SCT, Diablosport, etc.) teach classes showing how to adjust the MAF curve I think you're ok.

And it's not like you can put a MAF on a flow bench and then expect it to act the exact same way once on a motor. Everything is going to need to be adjusted.

 

[encasedmetal]

what the author of the article left out- is that when adjusting the maf transfer function, you also adjust according injector slope- etc, and all the other stuff that is associated with the MAF. a good example of this are the issues that most 4v cobra owners have with the SCT software, in that there is a hard count limit, and so a ratio of .47 must be multiplied against a ton of values in the tune. I did a write up for myseld with this problem-
The 63.9 #/min problem or finding the limit on a #mass/tic car: You have a high HP car and cannot keep it from going lean at WOT. You do not need to extend the 5v limit of the EEC but rather allow higher airflow within that limit. You need to determine a correction factor.
Select “Fuel injector” check box, then scalar. Highlight “breakpoint, high injector slope, and low injector slope” and multiply them by the % you determined you need to change. If you want a 20% change- mult. These factors by 0.80.
Select “MAF”, then “MAF transfer function”. Multiply all of the #/min (or #mass/tic) column by the same factor as you did in the “fuel injector” section .
Select the “Fuel” check box, then scalar. Scroll to the bottom and highlight the value for “manifold volume”. Multiply this by the same factor as well.
Select “Misc.”, then scalar. Scroll ¾ of the way down, and highlight the value for “engine displacement”. Multiply by the same factor as well.
anyways- with only having added longtubes- your biggest concern is enlongating the O2 sensor delay in seconds.

 

[HotStart]

Encased Metal: I think they are speaking more to 05 and up CAN processors (since they are referencing the DBW results, and posting in a GT500 forum) which do not have the XX#/min limit and do not need to be scaled for such. They are talking about cases where you put on a new mass air meter, and do not have a flow bench derived MTF.


I applaud Jim for writing that article, as it is always good to educate people, especially with the importance DBW cars have of having accurate air models. Everything he said is a fact, but I regret that it was presented in which in my opinion produces as much fear as it does knowledge. When I first came across the article, I thought maybe that was just my interpretation, or the way I was reading it. Since then I've seen a lot of posts using this article as a basis. I think on one forum it was posted on someone said something along the lines of "because they created their own mtf rather than a flow bench, you might really be running 35* of spark instead of the 20* you should, and blow your engine." I don't know if that poster realizes how far off the MTF would have to be for that to occur.

There is also some separation needed between those people who "tune without a flowbench". There is a big difference in the accuracy I would expect from someone making street pulls in a low gear datalogging from their new $100 wideband, compared with a properly calibrated load bearing steady state dyno using an AFM1000. The results are only has good as the equipment you use to produce them. I wouldn't expect to see a great difference between an MTF calibrated using top of the line tuning equipment(including the tuner), versus one from a flow bench. The Tooner vs Tuner debate is nothing new.

The article also does not point out that even though you had your mass air meter flowed in a lab, the MTF may still need to be adjusted on the car. this can occur from a variety of of reasons, and for non slot style meters, the way in which they are clocked is very important.

Now with that said, I do agree that a flowbench should be used to create the transfer function, but I do not agree that adjusting the MTF instantly makes someone a hack, and I do not agree with blanket statements like "you should never bring your car to someone who adjusts the MTF".

 

[encasedmetal]

for sure- I was just giving an example of how general I thought the article to be- sorry for the added confusion.

 

[Black Cobra]

...but I do not agree that adjusting the MTF instantly makes someone a hack, and I do not agree with blanket statements like "you should never bring your car to someone who adjusts the MTF".

Possible case in point. I bought the JLT 12" CAI high boost; which JLT states, "Note: Tuning is required with this kit!"

Now what possible tuning could be required here? In my mind the only thing that could be updated here would be the MTF.