CAI, turbo and surge

[Rainman]

With my CAI installed I notice that the engine surges alot with throttle transitions. Jersey explained in another post that it was from air bouncing off the closed TB back onto the turbo. I only noticed this problem after the CAI install and not with the stock airbox. How do you avoid this unpleasantness?

R

[mspdfreak]

Easy, just never let of the throttle!(wrc)

[Crock]

(lol) The only way to drive.

Seriously though, how do you do it. I'm considering a CAI in the future and don't want any "unpleasntness."

[Rainman]

On a 550 km drive home from the inlaws I tried to pinpoint when I get the surge. First, I realized that it only happens when the engine is under load and then I mash it. If I used a steady progression of throttle input I didn't get the surge to any noticeable degree. Second, I noticed that it seemed to happen mostly at peak boost. It would surge initially and then I would let off the throttle momentarily. This would be followed by one or two "after-surges" when I got back on the throttle even if I was gentle thereafter. After the boost pressure dropped then everything was normal again.

After thinking about what Jersey previously wrote and about the timing of the surges I now believe that it is a function of the CAI design. Mine I designed by myself so it is a trial and error thing. This may have been explained in the forum previously, but I didn't have a chance to look for it. My thought is that since our BOV is recirculating with a CAI there is limited amount of area where the recirulating port can be located. In all the designs that I have noted, the port has entered the CAI at a right angle. Under load and with WOT, the turbo attempts to spool up quickly. In so doing it reaches its peak turbo outlet pressure (stock = 6.5 PSI). Once this happens the BOV opens and recirculates the excess air, under pressure, into the CAI. Since this air is already under pressure it rushes into the CAI quickly disrupting the streamlined flow of air already present in the CAI. This turbulent air hits the turbo fins and causes a momentary loss of power.

The obvious solution is to place the recirculating bung as far from the turbo inlet as possible. However, the farther it gets from the turbo inlet on such a short length of pipe as the CAI, and the closer it gets to the MAF. I have read on the forums that turbulent air close to the MAF, such as with some aftermarket CAIs, also causes problems. The trick is to find the sweet spot where neither the MAF or the turbo inlet flow are affected. Check out our stock intake and you will find that the recirculating bung is quite far (12-18 inches) from the turbo inlet. Maybe the funky Mazda design of the intake was for a reason...LOL!

I will have to tinker with the design of the CAI to see if a different placement of the port makes a difference. I also wonder if it makes a difference whether the bung enters the CAI at less steep angle (e.g. 30 degrees) rather than the right angle that is typical.

This is my own thoughts about the issue and it may be completely wrong, but it seems to make sense to me. If someone thinks or know otherwise, I am happy to learn.

R

[jflo]

turkey. it happens.

[mspeed101]

Serves you right for putting a cai on a turbo car what were you thinking (lol2)

[Emode]

its there stock too, just muffled

[rocketspeed]

This has been thoroughly covered. The surge isn't any different with the stock box, you just can't hear it as well. Just like your turbo isn't as loud spooling up with the stock box. Its a pretty good sound damper.

[Rainman]

I thought that the turkey was just the sound from the BOV. The sound I can live with. The stalling was taken care of by recirculating rather than atmospheric vent (since I wasn't going to go right out and do the dual BOV/BPV setup). But the surging is a different beast altogether. I just took it out again and there seems to be two different types of surges. One that comes on right away once into boost with moderate load. Minor hesitation. No real loss of power but it feels as if it just isn't accelerating as hard. The other more annoying surge is the one that comes on with WOT that causes the car to almost buck if I don't let up. This I didn't expect and have never equated with the "turkey." If this is the turkey then I can understand why lots of people don't like it.

If this is the turkey, why are there two different types of surge. Also, does the turkey happen with every car that vents atmospheric?

R

[rocketspeed]

The BPV does not cause the turkey sound, but its involved in it. What happens is that the BPV blows built up pressure back into the intake when appropriate (like when you shift, or let off the throttle after boosting). This air goes into the intake and runs into the turbo, which is whizzing along doing its own thing- this causes all kinds of turbulence in the intake as the air runs into the compressor. That's the turkey noise you hear. People don't like it because its not good for the turbo itself. Really won't cause problems at the low boost levels of stock, but would likely become an issue if you raised boost enough.

Blowing off the pressure to the outside would be the easiest fix, except for one problem- our cars have MAF meters, which only know how much air has passed by them in one direction (toward the engine). If you vent out ot the aptmosphere, you'll trick the MAF into thinking there's more air in the system than there really is, which will cause too much fuel to be delivered. This is why folks who tried venting out to the aptmosphere had no turkey noice, but stalling problems. Folks figured out that the dual system would reduce pressure enough in the intake to get rid of the turkey noise, but still provide acceptable drivability because enough air is recirculating to prevent the stalling. This is still less than optimal, however, because you're still fooling the MAF- it still thinks there's more air in the system than there really is, you've just narrowed the difference in the amount between the two to a level where it runs OK.

The other thing you're describing has nothing to do with what I just talked about. I haven't seen your car to know if there's anything wrong with it, but the hesitation you describe is common and its because the car runs overly rich. The bucking and lash you'll feel through the drivetrain are due to the engine twisting around it its mounts, which are too soft. The more extreme version of what you describe doesn't match my experience, though- do you have the boost turned up? You may be hitting the fuel cut.

[thunder]

People get the turkey even when they use atmospheric bovs (ex. Forge bov)....

[ONRAILS]

Yep... I get (used to) get the same thing. It's not turkey related. I'm not sure if you have a FCD, but that's what worked for me. Once I installed and adjusted it, I no longer got those symtoms.




I thought that the turkey was just the sound from the BOV. The sound I can live with. The stalling was taken care of by recirculating rather than atmospheric vent (since I wasn't going to go right out and do the dual BOV/BPV setup). But the surging is a different beast altogether. I just took it out again and there seems to be two different types of surges. One that comes on right away once into boost with moderate load. Minor hesitation. No real loss of power but it feels as if it just isn't accelerating as hard. The other more annoying surge is the one that comes on with WOT that causes the car to almost buck if I don't let up. This I didn't expect and have never equated with the "turkey." If this is the turkey then I can understand why lots of people don't like it.

If this is the turkey, why are there two different types of surge. Also, does the turkey happen with every car that vents atmospheric?

R

[Geezer000]

If all you "TURKEY" fans read his posts properly you will notice that he is talking about the FEELING of the surges, Not the SOUND of the surges. I'm not trying to start something here, just trying to get this post going on the right track....
I think Rainman has the right idea, but I also get it with my stock airbox just not as predominantly as with your cai. So I don't think it's FCD fixable. That just fixes the fuel cut (or whatever you want to call it) because he said he also got it before full throttle.

[ONRAILS]

Yes... I realize that the FCD is specifically to correct the fuel cut, but it also helps with the drivability issues (surges, burps, hesitation...), at least it did for me. Not sure how it does it, but it did. Maybe because it also "tricks" the maf.




If all you "TURKEY" fans read his posts properly you will notice that he is talking about the FEELING of the surges, Not the SOUND of the surges. I'm not trying to start something here, just trying to get this post going on the right track....
I think Rainman has the right idea, but I also get it with my stock airbox just not as predominantly as with your cai. So I don't think it's FCD fixable. That just fixes the fuel cut (or whatever you want to call it) because he said he also got it before full throttle.

[Rainman]

Thanks Geezer. Let me just say that I am Purple and Proud brother...LOL!

Anyway, the surging sensation is more of the issue here. I will post pix of my setup. At the present I have a custom 2.5" CAI recirculated, a custom 3" mandrel-bent exhaust with single hi-flow cat. I am running stock boost. I have a Joe P MBC and FPR, but have not installed either yet. I am still waiting to receive my FPR from Joe (see my other threads for that story). When I mash it I hit 7 PSI peak and then return to 6.5 PSI steady. I have been flashed, but prior to the exhaust and CAI install. I have reset my ECU twice since the CAI install to try to resolve the issue. I really should have dynoed the car before the CAI install as it is really hard to get a sense of whether I have made any HP/TQ gains. With the surging it almost feels slower, but it is hard to clearly tell. My wife says that it is faster, but that is only because the CAI whooshing and turkey sound scare the shit out of her....LOL! Of course, while I was on vacation and I took it by Essential Speed to have Ian take a look at it, it never once misbehaved, even though it was hot and humid and we did 4-5 WOT runs. Ian thought I was smoking something or spending too much time in the sun.

When I first installed the CAI, it was not recirculating. I had the usual stalling issues. However, I also had this surging sensation on heavy load then as I do now. I think that it might have been a bit worse when I was vented atmospheric than it is now, but then again it just might have felt worse as it was totally unexpected then and now I have become a bit used to it. I have had to adjust my driving style a bit to avoid it, but it still does happen. At normal city speeds it isn't a problem, but it is a bit disconcerting when you are cruising along at 140 kmh at the front of a line of cars on an incline and then your car starts to buck when you step on the gas harder. Surging might not be a good way to describe it as it seems to ? "backfire/burp" (for lack of a better description as I do get true backfires that are completely different) and falter BEFORE it momentarily surges.

I also wondered about the fuel cut issue, but with only a 3" exhaust and the CAI that seemed unlikely. The sensation is almost like hitting fuel cut as it is as if the engine momentarily dies, but it is also different as it usually happens 3-4 times very quickly (within 1-2 sec) before it settles when I lift off. Sometimes I can lift off slightly and it resolves. Other times I have to get off the gas completely.

I hear everyone's argument about the turkey sound. This I see and have noticed like everyone else, but here I am talking more about the sensation although it does have a sound associated with it. It is also different than the drivetrain lash that people mention although if you put your car into 1st and depress and release the gas pedal quickly 3-4 times in 1 second you will get a rough idea of what I experience although when it happens in my car my foot is not moving on the pedal. I will try to take a video of it happening so that everyone can see what I am talking about.

R




If all you "TURKEY" fans read his posts properly you will notice that he is talking about the FEELING of the surges, Not the SOUND of the surges. I'm not trying to start something here, just trying to get this post going on the right track....
I think Rainman has the right idea, but I also get it with my stock airbox just not as predominantly as with your cai. So I don't think it's FCD fixable. That just fixes the fuel cut (or whatever you want to call it) because he said he also got it before full throttle.

[rocketspeed]

People get the turkey even when they use atmospheric bovs (ex. Forge bov)....
How did they set it up? Did they plug the nipple on the intake side that the BPV formerly emptied into and vent 100% to the aptmosphere?

As for the bucking stuff being reported, it seems to me that it still boils down to overly rich conditions. Really sounds like the hesitation that folks experience, but worse than most folks get- perhaps due to the combination of mods. I don't think its compressor surge related.

[thunder]

Well, there are hundreds (!!) of pages on the subject... One thread explains how to kill the turkey with a dual setup, that is a BOV on the IC-TB pipe while retaining the stock BVP. But it's such a long story.......
Sorry :)

[ricenudles]

there are tons of threads discussing whether or not turkey is really compressor surge or not. Honestly, I don't think it is, but thats just my opinion. I've read that relocating the bov/bpv will do the trick. A friend of mine with a GTI had the same turkey flutter, and he now has a clean "pssht" sound.

plus turkey isn't so bad. all the crazy jdm cars on best motoring vids have it.:p

[thunder]

See also:
http://www.msprotege.com/forum/showthread.php?t=56075

[rocketspeed]

Well, there are hundreds (!!) of pages on the subject... One thread explains how to kill the turkey with a dual setup, that is a BOV on the IC-TB pipe while retaining the stock BVP. But it's such a long story.......
Sorry :)
I've seen most of them. Anyway, I digress. My primary points to the original poster were a two- - that the drivability issues that he's experiencing aren't likely related to the turkey noise and that if you do try to get rid of it, any turkey solution that has you venting air to the aptmosphere is a less than optimal solution.

[thunder]

I agree. There is no performance benefit from venting to atmoshere. Ideally, a better quality BVP is all we should need. Unless if we move the MAF to the pressure side, but that's another topic....

[chrisjw85]

not to threadjack too much here but does the MSM have the turkey?

[Rich24km]

i've noticed my car bucking only a few times and thats when i hit full boost and then let off almost immediately as it hits. It just kinda jerks the car. But I did it on purpose. I get no surges with a CAI?

[Rainman]

Took it for a run this evening and had my son film. I will post the vid after I compress it to a manageable size. I also discovered that it doesn't happen at WOT, but rather about 3/4 throttle. If I mash it to the floor I get only a slight hesitation as I did before the CAI. However, if I leave it at 3/4 throttle, I get the bucking sensation. No turkey sound, but momentary loss of, and then recovery of power/acceleration (almost as if the car had hiccups). The sound that occurs here is more like burping than the turkey which I clearly hear when the BOV goes off. The car is NOT stalling here as my RPM do not change and I do NOT lose power steering or brakes. Just the bucking.

In the 2506 vid you can clearly hear the turkey under acceleration midway thru the clip. All turkey sound, NO bucking. However, in the 2514 vid you can hear the sound of the engine cutting in and out momentarily. Unfortunately, you can't really get a sense of the bucking too much, but it is fairly evident when you are riding in the car. I agree with Rocketspeed in that I don't think that the bucking is related to the turkey. Your thoughts are welcome.

R

[rocketspeed]

The turkey sounds should only happen when you let off throttle, like when you shift or just let off the gas- it doesn't happen as you accelerate that I've ever seen. You aren't saying you're hearing this while accelerating, are you?

I'm guessing its the combo of mods you are running coupled with the engine management. I'd have to physically see your car to help more than that- maybe others can help more.

[Dr.Sound]

To most of you new turbo guys your like "what the hell is that sound?" But Gents before the days of this huge aftermarket support we have now with the advances in BOV design the Turkey or "Turbo flutter" is all you heard. Its the vacume source versus the mechanics of the particular BOV/BPV used. It simply the gate of the valve opining and closing very quikly. What everone hears with the MSP's is the air of the stock BPV opening and closing inside the intake piping. Get a SRI or CAI and it will become more evident. Go with a different BOV or share the work with say a stock and an aftermarket BOV or duel chanber BOV and the flutter will disapear all together. As the after market BOV choice would be doing almost all the work.



In turboed autos, turbo flutter is very hard to lose in any advent. In order to change fluttering It has been said that it is the choice of BOV's, but its more contingent to the spring setting versus the vacume pressure the choice valves are seeing.



And yes till around 6 years ago all turbo cars were using very different designs in venting the intake pressure, yeah you had fluttering but with 20+ psi believe me it sounded fkg crazy. Watch some footage from Subaru WRX's of the Colin McRea late 90's era and you would hear what I'm talking about.



Like I said to most of you new guys this Flutter, gobble, turkey is a strange sound but to the old the only strange sound is Pshsssss!

[Rainman]

I have a better vid that I will try to compress tomorrow. As I, and others have said, I am not talking about the turkey sound. The sound that occurs with my bucking is different than the turkey. More importantly, it is not the sound that I am concerned with. The turkey doesn't bother me, nor does the sound that occurs with the bucking. It is the bucking, that noticeably shakes the car, that concerns me.

What I have discovered:
1. It only happens on acceleration.
2. It only happens on partial load (approx. 2/3-3/4 throttle).
3. It happens after the whistling of the intake is heard with partial load
4. It only happens on a roll. It has yet to happen on acceleration from a stop.
5. It does not happen on deceleration. However, if I accelerate hard, then let off the throttle, and then jump back on it at partial throttle I can induce the bucking which I can only stop by letting off the gas completely and then getting back on the gas much more gradually. I have not tried to power through it as the bucking gets progressively worse the longer I hold the throttle partially open.
6. It does not happen with full load. If I floor it then I get the regular MSP hesitation at 3700 RPM and then all is good to redline.
7. My boost seems to be OK as I spike at 7 PSI and then settle at 6.5 PSI steady.
8. My EGTs are normal and unchanged from pre-CAI.

Not sure what is going on, but I think that I will change the design of the CAI slightly so that the recirculating bung enters the CAI at an acute angle rather than at 90 degrees.

R

[Dr.Sound]

^ seems like the car is not flashed.....

[Rainman]

The car has been flashed, but the ecu has been reset. Do you lose the ecu reprogramming when you reset it? That is, is the ecu flash a firmware upgrade or does it simply change a preference file? This is an issue that I wondered about as well.

R


^ seems like the car is not flashed.....

[rocketspeed]

The car has been flashed, but the ecu has been reset. Do you lose the ecu reprogramming when you reset it? That is, is the ecu flash a firmware upgrade or does it simply change a preference file? This is an issue that I wondered about as well.

R
The flash stays with you no matter what. Only way to get rid of it it to install a new non-flashed ECU.

[Rainman]

Fairly cool morning today on the way to work. It seems that it does it more freqeuntly when the weather is cool or when the car is moving at speed. It did it several times this morning. However, it was much warmer this afternoon (~29 degrees celsius) and it didn't do it at all. I drove in the same manner this morning and this afternoon.

This makes me wonder if it isn't a fuel-cut issue. Twice before I got the car flashed in the winter the car bucked violently (once only each time) under heavy accelaration when it was really, really cold (-30 degress celsius) right when the car hit around 3500 RPM and the turbo was in full stride. It scared the shit out of me as I wasn't sure what had happened. I let off the throttle assuming it was either detonation from going lean (no mods at the time) or fuel cut. But it seemed rather violent for fuel cut which I have experienced once in the MSP at redline and several times in other cars without the same theatrics. The present bucking reminds me of the previous two experiences except that each time it occurs now it happens 3-4 times in very quick succession before I can let off and it only becomes violent if I don't let up on the throttle. I haven't checked my plugs to see if I am running lean, but my EGTs are OK, and my exhaust is as sooty as ever. The only thing that is out of the ordinary on my setup at the present is the fact that I have an third open 02 sensor bung from when my exhaust was corrected that I haven't filled with a plug yet. I don't think that this could be the cause because all the sensors are in their proper place and this sensor is downstream from the cat, however, I will get a plug tomorrow to see if it makes a difference. Any other suggestions or ideas?

R

[Rainman]

Here is an update on the surge business. I discussed this problem with one of the service guys at Mazda who is also a local tuner. With the combination of CAI and the 3" exhaust, I am now bringing in more air than the ECU can compensate for under conditions of light load. This causes tip-in detonation as the ECU struggles to keep up with the influx of air. The initial throttle tip-in causes an air/fuel excursion lean enough to result in a "misfire" before boost comes on. This results in a momentary loss of power and the dreaded "bucking/surging" that I am experiencing. It also causes a consequent super-rich state that then gets burned off creating sooty deposits, which I have noticed along the back end of the car since I installed the CAI, and especially after my 1000km roadtrip last week.

Guess I have some work ahead. Gotta get the car tuned, but I'll have to get bigger injectors, a bigger fuel pump, and a fuel management unit. Since I was planning to do a FMIC and hardpipes it would probably be most cost efficient to do all these things and then get the car tuned. It is hard to believe that with only the exhaust and the CAI I have reached the capacity of our fuel delivery system. Perhaps the flash is aggravating the issue? Don't know.

Now I am paranoid of the bucking/surging. I don't want to be running lean all the time. Funny thing though, because my EGT values are normal, although I have to admit that I haven't checked them out right at the time that the bucking/surging occurs.

This is the explanation as I understand it. If I have mis-stated something or made an error I am open to correction.

R

[rocketspeed]

The black sooty deposits on the tailpipe are universal to MSP's, we all run nutty rich when you're mashing the pedal.

He could be right, though, but your experiences don't seem to jive with what other MSP owners with the same mods have seen. There are a TON of MSP's with intake and exhaust running trouble free. There is a lot of variation among these cars.

The more violent bucking you describe I'm almost certain is fuel cut- its a rude awakening. Less violent hesitation- perhaps detonation. I do think that your combo of mods is causing something funky. The CAI is custom, right?

[Rainman]

The sooty deposits are now "over and above" what is normal for our beloved cars. It was there before, but NOT to the same degree.

I was wondering about why my mods might be acting this way, when as you mention, lots of others are running with the same combo. The CAI and exhaust are both custom. Exhaust 3" from S-pipe back, 1 hi-flow cat, crush bends, aluminized steel. The CAI is a temporary measure until my CF CAI (God forbid the CF guys should actually get the damn thing finished). It is 2.5" crush-bent aluminzed steel based in principal on the INJEN MSP intake. It has a single port for the BOV. The return from the valve cover is T-ed into the BOV recirculating line since the MSP didn't like atmospheric vent and I am not going to do a double set-up right now.

The more I think about it, the more I think that it is fuel-cut. I took it up to redline intentionally once the other evening to remind myself of the sensation of fuel-cut. The bucking feels almost the same, but it happens in such quick succession (three or four very quick bucks of increasing instensity, this being different than the one-time dying of fuel cut) that I got the impression that it might be something else. Furthermore, the fact that it only seems to happen at partial-load/throttle mystifies me. I would have thought that I would hit fuel-cut more readily when I mashed it to the floor.

The other idea that I considered was the angle at which the BOV port enters the intake. Like every other intake, it enters at a right angle, but I wondered if the air entry might be more streamlined if it entered at a slight angle. Anyway, now that I have heard another explanation for the bucking, I don't think that it is related to turbulent air re-entry.

R