Timing set at 10 degrees
Fuel pressure set at 38psi
Idle at 950-1000
New IAC and O2 sensors
Car ran great idled perfectly prior to the new air box. Surged after. How come? A/F showed pig rich. Tuned to pull A/F back down. Problem solved. What logical and reasonable alternative was there?
You're right. I'm wrong despite the tuner having fixed the surging and explaining to me what the issue was.The elephant in the room is turbulence over the mass air sensor.
Other possible solutions:
Change the shape of the intake tract
Screen the sensor
re-clock the sensor
change the sensor
change the housing
Scale the sensor and housing assembly
change the distance between the MAF and TB
etc..
There are a number of things that can induce and support a surging idle in a closed system.
You're right. I'm wrong despite the tuner having fixed the surging and explaining to me what the issue was.
Honesty, tuning seems like a far better option than working down that laundry list.The elephant in the room is turbulence over the mass air sensor.
Other possible solutions:
Change the shape of the intake tract
Screen the sensor
re-clock the sensor
change the sensor
change the housing
Scale the sensor and housing assembly
change the distance between the MAF and TB
etc..
There are a number of things that can induce and support a surging idle in a closed system.
Honesty, tuning seems like a far better option than working down that laundry list.
I forgot the third option: A mixture of 1 and 2.Change the tune in the computer to match the new parts that are given.
or
Fool the computer into thinking that the original parts are still there.
I read it.You clearly didn't read the part I wrote about air velocity through the MAF and how it was altered due to the new air box. But by all means flame away.
Cars with cams usually don’t idle well at the stock idle rpm even when I had the tfs1 cam mine liked the idle bump .Now we have a discussion!!!
Only 10 degrees timing? Bump it up to 12, hell 14*
Idle at 950-1000rpms kinda high I would think but not unheard of, don't remember what cam Habu is running, also don't know what size injectors, moot point though.
38 psi fuel pressure, back it down to say 32 psi.
What size maf, tb?
Now did 'tuning' this combo work? Apparently yes. Could it have been resolved without 'tuning' , well it depends on your definition of 'tuning' .
Manipulating timing and fuel pressure, setting idle would be considered 'tuning'. You just need basic eec tools.
I think no one is saying your tuner didn't fix your issue, I will say I think you could have 'tuned' it your self.
This is not factoring in a big assed tb, maf and/or cam which was not listed.
I feel nobody is right or wrong here, it's a discussion, bench racing.
And I prolly have the slowest bench here.
Cars with cams usually don’t idle well at the stock idle rpm even when I had the tfs1 cam mine liked the idle bump .
My car idles 980-1000rpm but for conversations sake it’s probably radical for a typical street car in here and this conversation. Oh and it has Holley efi in it
Verses cars without cams that can't idle at all?Cars with cams usually don’t idle well
Mine makes over 300 HP, but my mileage is in the 16 mpg range...I'm envious!I think the question is where is that line is when a street/strip car needs a tune, so your combo is definitely relevant.
Old school reply-
I do not mind the lumpy idle the letter cam gives my 325-350 Hp (calculated from track time slips) 5.0. It also gets 21.5 mpg on the highway with the AC on. The surging idle checklist was all the tuning it really needed to be streetable, although installing the adjustable IAC spacer I have from an F-150 might still be a good idea.
When I upgrade to new aluminum heads and get the @tmoss ported intake on, I might as well pick a newer cam to match. I hope Rhodes has a set of roller lifters for a 5.0 roller block at that point. The other engine builds I have used them on have benefitted as advertised, but without excess noise. So a better idle with more vacuum should help move the limit at which a tune is needed. If so, they will definitely be worth the money. If not, a wider power band will still be worth it.
Mine makes over 300 HP, but my mileage is in the 16 mpg range...I'm envious!
Sounds like it’s a blast to drive still ! Tom and Matt did my intake , I think Matt does most of the porting now . I’m happy with it they did real nice workI think the question is where is that line is when a street/strip car needs a tune, so your combo is definitely relevant.
Old school reply-
I do not mind the lumpy idle the letter cam gives my 325-350 Hp (calculated from track time slips) 5.0. It also gets 21.5 mpg on the highway with the AC on. The surging idle checklist was all the tuning it really needed to be streetable, although installing the adjustable IAC spacer I have from an F-150 might still be a good idea.
When I upgrade to new aluminum heads and get the @tmoss ported intake on, I might as well pick a newer cam to match. I hope Rhodes has a set of roller lifters for a 5.0 roller block at that point. The other engine builds I have used them on have benefitted as advertised, but without excess noise. So a better idle with more vacuum should help move the limit at which a tune is needed. If so, they will definitely be worth the money. If not, a wider power band will still be worth it.
So I may have misunderstood you so if I have please feel free to correct me but in this post are you saying that your car was tuned. You did the valve job and went back to the smaller factory airbox setup and picked up surging and required a tune? Further more you lay claim to yes a tune is necessary? Do I have that correct?Exactly. I have an aftermarket BBK MAF. The car had been tuned with a 3" ID intake tube and open element air filter. If you look at photos of my car you'll see that. I swapped over to a stock style intake box and the outlet of the box is a smaller ID than the inlet side of the MAF. Apparently that caused some kind of velocity issue for the MAF and the car was highly rich.
I'll ad that the car dyno'd at 299/301 with that setup. Since then I had a valve job done and installed the new LMR stock intake box, but the idle surging didnt occur until I installed the intake box. Now, it's possible that the compression was raised slightly as a result of the valve job head milling, but I do believe the intake is good for a few hp. I was not told that my heads were milled at all. Overall I was surprised I gained 12/10.
Back in the day this tune stuff didn't exist. A bunch of people did mods and installed camshafts ( alphabet cams were just about the only ones back then ). People did use ( what we called RV cams ). There were " work arounds " for most of the drivability issues. Bumping idle up...timing changes...plug gaps....indexing the MAF....larger injectors....all these things worked to a degree. Those cars ran but it was rare to see a fox mustang street car with EFI running faster than a 12 second quarter mile pass....breaking 11 seconds was just about unheard of in a street car.
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