READ THIS! for CAI/MAF/AF tuning info

I have previously posted issues with pegged MAF (5.0 volts) when I changed the blower pulley. Most have felt this should not have been possible and I had some other issue. On the dyno, using a data logger and voltmeter this condition was verified.

I have now found the culprit for this condition and wanted to share the information.

I went to spend some time with Blake Walker at Walker dyno tune. Blake has 3 race cars and has spent time working with C&L and other manufacturers in devloping and testing aftermarket products. Blake showed me some of the dyno results from the testing they had done with MAF meters and CAI. In this testing if became obvious that the position of the MAF sensor and the shape of the pipe near the inlet to the meter had a drastic impact to the "measured" air flow. Each time the "measured" air flow changed there was a resultant change in AF (some of these large from 11 to 15). One of the things they had noted was a change in CAI pipe size near the meter inlet created large changes in "measured" air flow.

The issue for my car is with my MAC CAI. The MAC CAI has a change in pipe size (gets larger) just before the MAF meter, causing a disturbance in the flow/pressure. The distubance makes the "measured "flow higher than actual flow. This was compensated for in the custom tune to correct the AF out to the time the MAF reached 5.0 volts where the AF would then default to rich. We tested this theory by putting the stock air box back on and now could pull to redline without pegging the meter (as expected it was much leaner with the stock box because the custom tune had be adjusted for the misreading with the MAC CAI)


From this I think we definitely proved the CAI can drastically change the AF by changing the "measured" air flow even when the airflow has not changed.

Thanks to Blake Walker at Walker dyno tune for helping on this.

Wow, that is interesting. I dyno'd my car before and after the K&N FIPK and exhaust primarily because I was concerned about the A/F ratio change (reading some posts here made me paranoid, lol). With the K&N and a Borla 14858 the ratio only changed an average of .2 (two tenths).

This just seems to reinforce the practice of dynoing for A/F after any mod that could effect A/F.

Chameleon said:

Wow, that is interesting. I dyno'd my car before and after the K&N FIPK and exhaust primarily because I was concerned about the A/F ratio change (reading some posts here made me paranoid, lol). With the K&N and a Borla 14858 the ratio only changed an average of .2 (two tenths).

This just seems to reinforce the practice of dynoing for A/F after any mod that could effect A/F.

Click to expand...

I agree with the need for dyno, can never be too safe.
Not all CAIs will have bends or changes in pipe size that will create a problem, as yours does not, but some, like mine, may.

anybody else seen this?

I think that this is pretty common with Mac CAI kits.

this is why I stay away from any kits that relocate the Maf.
Just give me a huge free flowing filter and a shield and I am happy

peace

yes, i have seen the same problem with the 90 degree thru the fender style cai's. it creates turbulance in the flow therefore causing a lean condition that has to be compensated for

My new JLT is here now I just got to get over to the dyno, put it on and tune it.

Good info on the MAC CAI and the change in pipe diameter prior to the MAF. I am presently installing an '03 Cobra motor in my GT that I am running a MAC CAI... I would like to avoid buying a new unit and as I will be doing a custom tune for the 2.93 pulley does the MAC 90 degree CAI in the fender unit make good power and have good driveability as long as you tune for it?
Thanks

SoCalHarley said:

Good info on the MAC CAI and the change in pipe diameter prior to the MAF. I am presently installing an '03 Cobra motor in my GT that I am running a MAC CAI... I would like to avoid buying a new unit and as I will be doing a custom tune for the 2.93 pulley does the MAC 90 degree CAI in the fender unit make good power and have good driveability as long as you tune for it?
Thanks

Click to expand...

MY MAC CAI made good power until 430 RWHP, then it stopped.
At that point the MAF was at 5.0 volts and limits the fuel and timing. If you plan to make 430 RWHP or less you can use the MAC and tune for it's issues. If you want to make more HP you will have to change the CAI or use a different meter or a MAFextenter. I have chose to change the CAI. I hope to post the results of my change within the next week or so.

Uhhh..well...The MAC CAI worked fine on a car that made 451 rwhp with an unported Eaton/2.8 combo.The other mod was an accufab oval T/B & a predator 'box' tune.Im not saying you dont have a valid point..you backed up what you said with testing..Very good detective work.
But I'm just saying we experienced no such issues.The MAC is still on the car,but it has an SCT MAF & a Whipple..
Runs perfect..

Tat03Cobra said:

this is why I stay away from any kits that relocate the Maf.
Just give me a huge free flowing filter and a shield and I am happy

peace

Click to expand...

:shrug: Funny you say this. Your FIPK relocates the MAF.
12:00 isn't the stock position, is it???

This does make a difference.

Tucker said:

:shrug: Funny you say this. Your FIPK relocates the MAF.
12:00 isn't the stock position, is it???

This does make a difference.

Click to expand...

You're a funny guy Tucker.
ok, so the fipk rotates the maf a FROM 10 TO 12 -, but it stays in the stock location - I.e, same distance from the tb.
Your JLT physically moves the whole unit into the fender well. Which was the purpose of this whole thread. Nice try though. You should have stayed out of this thread, now everyone can make the connection between how drastically your JLT alters A/F.
op:

peace

Tat03Cobra said:

You're a funny guy Tucker.
ok, so the fipk rotates the maf a FROM 10 TO 12 -, but it stays in the stock location - I.e, same distance from the tb.
Your JLT physically moves the whole unit into the fender well. Which was the purpose of this whole thread. Nice try though. You should have stayed out of this thread, now everyone can make the connection between how drastically your JLT alters A/F.
op:

peace

Click to expand...

You need to do more research as the rotation of the MAF plays a huge role in A/F. You are mistaken if you don't think so.
You don't see threads about the JLT leaning out cars. do you?
The thread is about the pipe dia. and bends in front of the MAF. Read it again. The thread starter just bought a JLT.
Moving the MAF to the fenderwell is to keep the filter on the MAF as the factory intended and in the vertical rotation doesn't play as big of a role.
Thank you.
Jay

9A Pilot said:

Uhhh..well...The MAC CAI worked fine on a car that made 451 rwhp with an unported Eaton/2.8 combo.The other mod was an accufab oval T/B & a predator 'box' tune.Im not saying you dont have a valid point..you backed up what you said with testing..Very good detective work.
But I'm just saying we experienced no such issues.The MAC is still on the car,but it has an SCT MAF & a Whipple..
Runs perfect..

Click to expand...

Your SCT MAF is the difference, you have more range with SCT before you get to 5.0 volts. I still have the stock MAF meter.

Walker Dyno tune, with C&L, did quite a bit of testing by just rotating the sensor to different clock positions. It made large differences in the AF ratio, with no other changes.
The main thing is to get things (CAI, MAF, etc) where you want them, tune for that configuration, making sure the MAF does not reach 5.0 volts.

for almost 3 years we have seen that these cars prefer a straight in air source..bringing air in from the fender well causes turbulence in the laminar air flow and will cause stalling,surging and tuning issues.. the only exception to the fact is the JLT unit. we very rarily see any issues with it..
pegging the MAF is common place these days with all the options for more power. There are a few solutions.. The SCT 2400, Zone 5 MAFEXTender and soon the Diablosport MAFia...pegging MAFs can be tuned around but it is not advisable to do that because one colder day and the car will go into a different load table and you may damage the motor..it is always better to address your pegging MAF issues than tune around it.

Thanks Linn, this means alot coming from a reputable tuner/shop like you have.

Remember that the MAF is the majorload calculator. Anything moving/distorting air meter causes major load changes. Some good, some bad. ( provided your car is/has been tuned for this) THis is the reason for a custom tune, a true street tune (not a mail order tune).
A true street tune is SSSOOOOOOO much better than a dyno pull tune anyday.
Vince

Update on my car. I changed the MAC for JLT CAI. The MAF is no longer pegged and the HP increased from 424 to 448. The AF looks better and the idle is much better.