Aftermarket Intake + Bog Issues - Read Here

[Jidonsu]

Specs: Scion FR-S with Visconti's Ecutek Tune and Injen intake. 3900 miles on the odometer.

Summary of problem:

A. When rolling in 1st gear at 5mph (because of slow traffic, uphill, etc), and you go near WOT or WOT, the engine and car jerks/bogs and hesitates to climb above 1800rpm. The engine eventually settles and climbs pass 2000rpm. The problem goes away once you pass 2000rpm.

B. Same thing happens in 2nd gear in low RPMS, i.e. below 2000rpm.

Video of Problem:

Watch what happens when the car reaches around 1800rpm. It doesn't look that bad in this video, but the car stops accelerating for a moment and jerks as a result. It has been worse where the jerkiness lasted longer before climbing through 1800rpm.

[ame="http://www.youtube.com/watch?v=4msZh8MIjos"]Injen - YouTube[/ame]

Testing Procedure:

Put car in 1st gear, let car accelerate to 5mph. Foot off gas pedal and let car settle around 5mph, which for me is around 800rpm or so. Quickly increase throttle. Observe whether the revs climb steadily and smoothly to 2000rpm and beyond or not.

Results:

Test Situation 1: Injen intake installed + Snorkel inside bumper - Problem exists

Test Situation 2: Injen intake installed - no snorkel - Problem exists

Test Situation 3: Stock intake installed - no snorkel - Problem exists

Test Situation 4: Stock intake installed WITH snorkel - Problem goes away


Other Stock Cars:

For further testing, I rode with 3 stock BRZs and one stock FRS today at a get together, all manual transmissions.

Observations: All four cars did not jerk at all. All four climbed steadily pass 2000rpm and continued to build power. All four cars were stock with no engine modifications or tunes. The mileage on the cars ranged from 500 to over 3000.



If you have an aftermarket intake installed, or even the snorkel removed, please repeat the testing procedure stated above and report back. Please let us know if you have any other modifications to the engine or ecu. Please vote in the poll and also post details if you answer yes and have modifications. Please also post details if you answer no and have modifications.

I forgot to add options of

Yes - I have a tune only
and
No - I have a tune only.

Please just post in the thread if either of those are true.

NOTE: DO NOT vote no if you haven't done the test. The issue only shows up under specific conditions. It doesn't happen to me until unless I'm in those conditions, which is rare, but it's a very repeatable problem. I've done it at least 20 times now on different days, in different temperatures, and in different road conditions (flat, incline, etc), and it happens each time. It look me a few weeks to realize that there was a pattern and come to where I am today. Unless you did the test as I said, your vote won't count.

[ft86-UAE]

its a tune issue only check the your tuner and he can fix it.

[dabocx]

Originally Posted by ft86-UAE

its a tune issue only check the your tuner and he can fix it.

Non tuned cars have reported the problem as well.
Nor has anyone that is stock other than a tune reported a problem.

[Jidonsu]

Originally Posted by ft86-UAE

its a tune issue only check the your tuner and he can fix it.

It's also happening with cars that have the stock tune and an aftermarket intake. Let's hear back from others to see if we can isolate what exactly is causing the problem or exacerbating it.

[elchote]

I had a Mazda 3 a few years ago, and when I put an intake on it eventually I had very similar problems. In that case it was because with the intake the MAF wires had less slack than stock, and if you are familiar with Mazda 3s you know that they have very soft engine mounts, so the movement of the engine coupled with the extra tension on the MAF wires ended up breaking them. I'm afraid this kind of looks like a similar situation. If it is the same thing, the problem will get worse over time. I would say it is showing up only in first gear right now because first gear is when the engine moves the most.

I should add that I installed my Airaid intake today, and don't have the problem, but am concerned with how the MAF wires look pulled under this application.

[Jidonsu]

Originally Posted by elchote

I had a Mazda 3 a few years ago, and when I put an intake on it eventually I had very similar problems. In that case it was because with the intake the MAF wires had less slack than stock, and if you are familiar with Mazda 3s you know that they have very soft engine mounts, so the movement of the engine coupled with the extra tension on the MAF wires ended up breaking them. I'm afraid this kind of looks like a similar situation. If it is the same thing, the problem will get worse over time. I would say it is showing up only in first gear right now because first gear is when the engine moves the most.

I should add that I installed my Airaid intake today, and don't have the problem, but am concerned with how the MAF wires look pulled under this application.

Did you do exactly what I did in the test above? It only shows up under specific conditions.

[Symbiont]

This probably has to do with excess turbulence at low RPM and high throttle causing the MAF voltage to freak out.

Probably emphasized with a tune, but affecting some people without.

[Jidonsu]

If you voted no and has an intake or tune, please clarify whether you actually repeated the testing procedures. If not, it doesn't really count unless you happen to mash the throttle from a low rpm state frequently. It took me about 2000 miles of driving to come across situations where it occurs.

[Foobar]

Just tested this tonight. It doesn't happen all the time, so I'm not sure if I'm doing this consistently enough, or if the culprit is intermittent.

[xjohnx]

have you done a datalog yet while replicating the condition? I'm sure that with a datalog, @Visconti would be able to pinpoint the issue fairly quickly.

[Jidonsu]

Originally Posted by xjohnx

have you done a datalog yet while replicating the condition? I'm sure that with a datalog, @Visconti would be able to pinpoint the issue fairly quickly.

Thanks for the tip. I believe someone else already did. I'll check with him when he's less busy.

To those who said no and have intakes, please post to let us know if you've actually tested it per the original post.

[2forme]

First, some back ground info

I have a 6MT BRZ Limited with just over 2000 miles.

My mods thus far are Perrin crank pulley, SRT HB Exhaust, and Visconti STG1 e85 tune. With these mods, I've never experienced any issues.

After installing the AIRAID intake, I immediately noticed a loss of low end throttle response. I originally thought it was just the ECU going through it's learning process. However, the car started occasionally cutting power and jerking while pulling away from a stop or accelerating heavily from low RPM. I managed to capture this on a log seen here:



Under heavy throttle, the MAF reading started spiking up and down. As a result, the ECU cut all the ignition timing. I sent the log to @Visconti and am waiting to hear what he says.

Now, Cobb uses "air straighteners" in all of their subaru intakes right before the MAF. The stock intake also uses these. An example is here:



I'm willing to bet, the stock MAF is tuned to use these and having the MAF so close to the velocity stack is messing with out readings. I'm surprised aftermarket companies overlook these. Especially with these molded plastic parts, it would be entirely easy, and cheap to implement.

That's my theory anyway.

[JACK 8URT0N]

I am going to hold off on installing the Airaid intake I purchased, and keep an eye on this thread. Hopefully, there will be a fix coming, as it seems enough people are experiencing issues with the MAF.

[TyperRspec789]

I have the Injen intake installed as well, WITHOUT a tune. I have not had any issues with a low rpm take off in 1st gear.

I'm kindof worried now, i participated in the Visconti stage 1 tune group buy... I'll definitely report back if I experience issues once I do the tune.