CAI/ OFT questions
 

Hey all, so I have the Perrin 2.5" CAI on my car right now. I bought it for the sound really, knew there wasn't much power increase on it. I'm thinking about switching to a 3" big MAF intake (or a comparable) but Perrins website says that with it the car must be tuned, in fact they say its "REQUIRED".

I have a bit of an understanding about running rich/lean, but I don't understand why it would be a REQUIREMENT. I get that it would need tuned to yield the maximum power out of it, but would the engine have some failure or increased wear if its not tuned specifically to the 3"?

Also, I have an OFT which has the pre-loaded stage 1 & 2 tuned to the stock intake, or comparable, like the Perrin 2.5" CAI.. So would this be good enough for the 3" big MAF as well? Would it still need a specific tune for the larger diameter CAI?

....or would it just be a waste of money upgrading the CAI if I have to get a custom tune (not a discussion about the various prices of them lol) for the 5-10hp increase that the 3" claims to give??? :cheers:

Does the 3" even give those kind of gains on a NA engine?

Its purely down to the MAF housing being larger means that the sensor readings will be thrown out. They have the sensor scaling on the website, just correct it and you're good to go.

The OFT stages are not tuned for "comparable" intakes. They are tuned around the stock intake with a cut and widened front air scoop and with or without a drop in filter. Not sure where you got the idea that running an intake would be fine without tuning since the OFT release notes specifically say stock intake.

The reason why its not a good idea to run an intake without tuning is because anytime you increase the diameter of the intake track or move the MAF sensor from its stock location, you change what the MAF is reading. This is especially true when you increase the diameter of the intake because the MAF scaling is drastically different than stock.

Will you be "fine" running the perrin 2.5" cold air intake without a tune? Probably. But you are also ideally making exactly the same HP as stock ideally and probably making less without tuning for the intake.

Running the 3" Big MAF perrin intake without tuning would be a recipe for disaster since the engine will not know exactly how much air is coming into the engine and that affects the fueling.


As for HP gains from intakes. I'm highly skeptical of any HP claims on intakes from dyno charts that are provided by the manufacture. Its been proven time and time again that the vast majority of intakes made for this car don't make any power and most actually lose power or are unsafe. Any gains shown on a chart are most likely there by leaning out (unsafely mind you) the engine, which gets corrected after several miles of driving by adjusting LTFT's. Once you get your car tuned to operate safely with the intake, the majority (if not all) of the gains come from the tune and not the intake. My advice would be to sell the intake you have and go back to stock.

This is a direct quote from an email exchange I had with sales@vishnutuning.com:

Me: So with a Perrin cold air intake and bolt on I would currently use stage 1, and when the header is replaced, go to 2. Right?

Vishnutuning.com: Yes that is correct.

And again on a second occasion, when I asked about the Big MAF:

Me: Hi, I might be switching from a Perrin 2.5" CAI to the Perrin 3" Big MAF CAI, and I'm curious if I would be using the same map?

Vishnutuning.com: You should be fine using the same map. We haven't release a dedicated map for the 3inch intake yet.

So what got me started on all this was their use of the word "should" lol. And I say that the Perrin CAI is comparable to the stock box precisely because it makes no more power, but I understand what you're saying.

Yeahhh thats kind of where I was leaning. The sound from the CAI is great but I'd really rather have the performance.. and I figured "hey! why not try getting both with a 3" intake!" :lol:

But that all makes perfect sense. :thanks:

I guess what your definition of fine is. Will the standard off the shelf tunes be able to handle the trim adjustments needed for the 2.5" CAI from perrin? Sure, but your LTFT's may be all out of wack. Will it run? Yep. Is it ideal? Nope.

As for the 3" intake, I find it hard to believe that @shiv@vishnu would say that running the 3" intake on a standard OTS map would be fine without some form of MAF scaling adjustments. Even if you only modified the maps with the provided scales from perrin, that would be better than nothing at all. I'm fairly certain he's getting married this weekend so I wouldn't expect an answer directly from him for a bit but maybe he can chime in here when he gets a chance to clarify.

@jamesm made a very good point the other day that the MAF scale isn't just used for airflow, its also used for load calculations. If the MAF isn't corrected:
- The ECU sees less airflow
- The car will run leaner on OL
- The ECU will see less load thus putting you higher up the relevant tables
- That will mean increased timing and leaner operation

You can see why its not idea.

OP if you have an OFT and Perrin supply MAF scalings for both 2.5 and 3 inch intakes its only about 10 minutes work to copy in the perrin scalings to your oft tune and flash the now correct tune.

Hey so what did you end up doing?

^^ To run the 3" MAF, you need a properly change MAF scale. Perrin supplies one for free, but it needs to be applied to whatever tune you're running.

Their's isn't perfect, but it's much closer than the stock scaling will be.

I thought you might want to hear from someone who is already doing what you want to do. While I don't have the perrin 3" intake, I do have the Skunk2 intake without insert which is about 3 - 3.25 ". They don't have a maf scale for it yet, so I've been doing my own maf scaling. I've compared with and without the .75" insert to see if I can feel the difference, and I can tell for certain that without insert has better "snap" throttle response. So, bigger is better for short term throttle response.