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Really really weird!

Old 11-04-2018, 08:01 PM
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Really really weird!

Im have THE WEIRDEST issue. When I put it into drive, it idles fine but when i go to step on the accelerator (from completely stopped only) it acts as if it wants to die, the rpms drop really low. Its only when i let off the gas that it goes back to idling fine. But its only when on a hill. From take off the car hesitates to pick up speed, it builds up then takes off like a bat outta hell. Any thoughts?
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Old 11-04-2018, 09:00 PM
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are you getting a check engine light
any lights flashing on your dash?


can we get additional information on the vehicle? I take it it's an automatic. year? mileage?
igntion system: OEM? Aftermarket? Last time coils or plugs were changed ?
catalytic converter still on the vehicle?
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Old 11-04-2018, 09:26 PM
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Originally Posted by Jedi54 View Post
are you getting a check engine light
any lights flashing on your dash?


can we get additional information on the vehicle? I take it it's an automatic. year? mileage?
igntion system: OEM? Aftermarket? Last time coils or plugs were changed ?
catalytic converter still on the vehicle?
Its automatic 2004 114k (jdm replaced engine done myself)
-new corvette coils
-new ngk spark pulgs
-catless
-new secondary air valve
-new fuel pump
-new alternator
-all new air hoses
-cold air intake made from 4inch pvc and rubber couplings
All parts are only 4months old.
Im getting intake air temperature, secondary air injection

Last edited by Darius Obo Thomas; 11-04-2018 at 09:28 PM.
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Old 11-04-2018, 11:32 PM
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Originally Posted by Darius Obo Thomas View Post
Its automatic 2004 114k (jdm replaced engine done myself)
-new corvette coils
-new ngk spark pulgs
-catless
-new secondary air valve
-new fuel pump
-new alternator
-all new air hoses
-cold air intake made from 4inch pvc and rubber couplings
All parts are only 4months old.
Im getting intake air temperature, secondary air injection
My money is on this one.

The OEM intake on this car is one of the best options. The only ones that are proven to be better are the AEM intake and Revi intake. Everything else is likely to cost you power.

Reinstall the stock intake and see if it goes away. If it does, keep it that way unless you have the money for an AEM or Revi.

For reference, air intake design is a lot more than "put a pipe on it"... Lots of things have to be considered. The OEM intake filter actually helps straighten the airflow so you won't have turbulence. The OEM intake is also already a CAI by definition - it pulls air from outside of the engine bay.
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Old 11-05-2018, 08:29 AM
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Yikes. Yeah. Put the stock intake back on there. Even if it's not the root cause of this issue (which it probably is), odds are it's reducing the engine's performance.

​​​​​
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Old 11-06-2018, 12:51 AM
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Originally Posted by Loki View Post
Yikes. Yeah. Put the stock intake back on there. Even if it's not the root cause of this issue (which it probably is), odds are it's reducing the engine's performance.

​​​​​
I legit have the same size air filter that comes with the AEM one and the car dies when the intake is routed outside the car (its located in the engine bay atm).
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Old 11-06-2018, 01:00 AM
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theres more to our intakes as others have mentioned. placement of maf, daimeter, screens in the tube. vac lines etc. return it to stock.
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Old 11-06-2018, 06:39 AM
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Originally Posted by Darius Obo Thomas View Post
I legit have the same size air filter that comes with the AEM one and the car dies when the intake is routed outside the car (its located in the engine bay atm).
Ah. So a hot air intake then
Do you, for example, have the airflow strightener screens before the MAF? Small things that make a big difference.
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Old 11-06-2018, 07:08 AM
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Dude, put the OEM intake back in. It's better than anything you've fabricobbled together.

You need to smooth and homogenize the airflow before it goes across the MAF.
You need to consider the Helmholtz tuning Mazda exploit to improve performance.
You should to pull air in from outside the engine bay if you care about intake air temperature (though, as you say, this is unlikely to be the cause of your problem).

Do some data logging and post your MAF rate, STFT, LTFT, IAT and RPM. I'd bet you have some really wacky MAF numbers and fuel trims.
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Old 11-06-2018, 07:32 AM
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Old 02-13-2019, 01:16 AM
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Okl sorry for late late reply, im a business owner and im just now getting time to work on the 8 again. But im back at it again. Ive done my research and Ive completely duplicated the BHR cool air intake, which is leading outside the bay in the exact location. It only hesitates from fresh start. Once its warm and driving it get up and goes from everywhere no problem. Apparently, with the 8 the location and size of the filter matters. But now, another issue has surfaced. Beside that issue the car runs fine, except now, (when its warm) it randomly dies at idle (sometimes not all the time) but starts right back up and stays on for 10secs then dies. It will stay on an drive at this point but I have to launch from neutral for it to stay on (it died in the middle of a traffic light, no cops came thank god) lol. Any suggestions on what it can be? Still thinking its the intake?
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Old 02-13-2019, 03:21 AM
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Bhr doesn't produce an intake. Can you show us what you've built?

The size and position of the intake do not matter, but straight airflow through the MAF does. As everyone in this thread pointed out, the stock intake and good replacements include mesh screens before the MAF for this reason. Do you have those?
​​​​​
So yes it's still the intake. This is exactly the kind of problems cheap intakes like the K&N cause.
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Old 02-13-2019, 06:43 AM
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As I (and everybody else) said last year:
Put the stock intake back in, you muppet.

It performs better than anything you can fabricobble together.
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Old 02-13-2019, 11:02 AM
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I think the 4" PVC intake is a great idea as it perfectly feeds the rx8's 100mm throttle body....
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Old 02-13-2019, 01:17 PM
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Also, PVC is not a very good material to use under the hood of a car.

It's a thermoplastic so it gets softer and more pliable as it heats up (eventually melting). Depending on the grade of PVC being used, it may begin to deform as low as 140F.
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Old 02-13-2019, 02:28 PM
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Ok, so what are some other options if it's not the intake?
https://cimg3.ibsrv.net/gimg/www.rx8...88320b9a31.jpg
My bay
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Old 02-13-2019, 04:14 PM
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That intake? Holy ghetto-fabulous, Batman! The electrical tape as a joint compound is just... nothing, I have no words.

You have a bend immediately before the MAF. If you don't have something in the tube after the bend to smooth out the airflow, it's probably that.
https://en.wikipedia.org/wiki/Flow_straightener

Look at the MazdaSpeed/AEM intake. See how it's a straight shot up the pipe from the bumper to the MAF?
Now look at the Racing Beat REVi intake. See how air will enter the MAF tube nice and laminar?
This is the primary reason why these two intakes are the only aftermarket intakes that don't cause problems. They provide clean, smooth, non-turbulent air to the MAF.

If you're going to insist on having an awful intake from off-cuts in the bargain bin at the hardware store, set it up so it's a straight shot from the bumper to the MAF and then put the bend to accommodate the throttle body angle afterwards. Also, put a flow straightener in the tube directly after the air filter.

Also, even if that intake isn't the cause of the problem, I'd bet sex to donuts that you're losing power because of it.

But I already you know aren't going to fix that because, well, you've ignored the advice of everybody who knows anything about these cars, soooooo...
What codes are you getting with your check engine light?

Edit: I just got why you refuse to return it to stock... You hacked up your OEM intake for the MAF tube, didn't you?
Also, tie your battery down. Its a really bad plan to have it weeble-wobbling around freely.

Edit 2: I just re-read the thread to try to make sense of, well, you and noticed you typed " Im getting intake air temperature, secondary air injection ".
Do you mean you're getting codes for those? If so, the intake air temperature code is a clue. What is the specific code? The IAT sensor is inside the MAF and the ECU uses it in it's calculations to keep the car running. Either your IAT sensor is bad (in which case, you need a new MAF), your wiring is bad (in which case, it's time to start splicing), or your intake has screwed things up enough that IATs aren't feasible.

Seriously, post the actual pcode for the IAT.

Last edited by NotAPreppie; 02-13-2019 at 04:44 PM.
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Old 02-13-2019, 04:29 PM
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it really sucks 8s arent worth anything anymore, they are quickly becoming civics
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Old 02-13-2019, 04:31 PM
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Originally Posted by 200.mph View Post
it really sucks 8s arent worth anything anymore, they are quickly becoming civics
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Old 02-13-2019, 05:22 PM
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What NAP said has a lot of truth to it.

I am actually designing an intake for a kart for a school club, and I ran a few simulations for different designs with SolidWorks Flow Simulations. You can actually see the turbulence in the pipe right after a bend like that in a flow sim. The side on the inner edge is gonna have some nasty turbulent flow in a design like this.
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Old 02-13-2019, 05:24 PM
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"it's the intake"
"ok but what are some options if it's not the intake "
"...."
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Old 02-13-2019, 05:44 PM
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Old 02-13-2019, 06:59 PM
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Originally Posted by UnknownJinX View Post
What NAP said has a lot of truth to it.

I am actually designing an intake for a kart for a school club, and I ran a few simulations for different designs with SolidWorks Flow Simulations. You can actually see the turbulence in the pipe right after a bend like that in a flow sim. The side on the inner edge is gonna have some nasty turbulent flow in a design like this.
Yes sir - same for plug flow reactors with injection ports - watch thy turbulence and Reynolds numbers.
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Old 02-13-2019, 09:50 PM
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Originally Posted by wannawankel View Post
Yes sir - same for plug flow reactors with injection ports - watch thy turbulence and Reynolds numbers.
I set the sim to show the velocity arrows and plots throughout the intake, and it's pretty apparent why that design sucked(not literally; that would have been good).

But your experiment is a lot better since it's using real gas, versus some general assumptions I made for my sim. Good enough for my purpose.

Either way, many arguments to show why OP's intake isn't a great idea.

Last edited by UnknownJinX; 02-13-2019 at 09:54 PM.
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Old 02-14-2019, 12:36 AM
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it sounds to me like a trans issue honestly. the intake is a big issue for our cars but its not gonna cause that issue. autos are crap cus if their fluid isnt right or its old or whatever it can have all sorts of funky issues. id make sure ur torque converters good and ur fluids good and filters fine and such.
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