setup:
98 accord 5 speed
drag kit
tial wastegate
AFC hack w/ DSM 450's
turboXS HP MBC (and previously cheap *** ebay MBC)

when I get into the gas HARD from a slow speed (full throttle), my boost spikes over 10-11 lbs, causing the map sensor to put the car into limp mode. (stupid AFC hack)

when being more gentle w/ the throttle, it never spikes at all, just goes up to ~8 psi and pulls hard

the boost controller is off the compressor housing on the turbo (previously was off the intake manifold, same prob.). 1/4" I.D. lines and fittings from compressor --> MBC --> wastegate. tried moving the MBC as close as to the wastegate as possible, same problem.

when I take the MBC out of the equation, works perfectly, no spiking

two different MBC's and the same issue occurs.

I'm about to throw the MBC in the trash and just use the wastegate spring again.

can anyone offer some insight, or is this common w/ MBC's? would smaller lines/fittings help at all?? thanks to all. -B

 

i would like to know too... i have the same problem with my bros 95 sohc civic no external waste gate though. Boost will spike to 11-12lbs when going from low rpms to redline. Any other time it runs around 7-8lbs.

 

yeah that use to happen with me . . . a lot say that manual boost controllers will do that for some reason. Try a electronic boost controller and see if that works. BTW what kind of MBC's are you guys running?

 

crappy one that comes with the greddy kit...

 

I've used a crappy ebay style and also a nice turboXS high performance b.c. both with the exact same results.

 

yo b, give me a couple of hours and i'll post a pic of my MBC. i never have spike problems. post a picture of ur MBC too if u can.

 

btw, i'm also running mine off of the compressor housing.

 

just thought i'd throw in a pic of my heat shield too, i know u have the same under the hood issues too. just gotta get my turbo and my down pipe wrapped.

 

is it a ball and spring setup??

Landon

 

I've seen too many MBCs boost spike real bad to consider using one myself.

Electronic boost controllers rarely, if ever, seem to have this problem.

 

looks like the same thing that i have i think that i am just going to upgrade up to an electronic thank though

 

for those who dont know what a mbc is, its a manual boost controller.

 

ball and spring type.
3rd gear pull from as low of rpm, i think it was around 2,000rpms but dont quote me on it.

blue=boost
violet=throttle
green=air/fuel
red=rpms
light blue=raw knock sensor voltage

 

mine's ball & spring w/ bleed valve too

what's that heat shield made of b_ron? I had one over my turbine housing but it broke, I got it replaced, and the new one promptly broke.

I just can't understand the spike I get, and it's only when just jumping on the throttle HARD, it just happened 3 times just on the way home. I think I'm gonna just ditch the MBC & get a slightly stonger wastegate spring and be done with it.

 

thick sheet metal....bolts on through one of the turbine bolts. how the hell did ur shields break? just to hot?

i have experienced real bad spikes before, when i first installed my AEM EMS....i was still running the missing link and FMU on a NA base accord map. it happened only when it went lean. i got spikes of 11psi but i backed off real quick, kinda the same way ur saying it's happening to you.

according to the EMS at 10psi i am about maxing out my injectors......90% injector duty. i took off my adj. FPR like a dummy trying to trouble shoot...gotta reinstall it.
any ways....maybe ur maxing out the injectors with the stock ecu? we have the same setup turbo kit wise.......was it always spiking? even on the FMU n stock ecu i never spiked.....it went to 8psi then droped to 7.8 psi.
what wastegate do u have?

i say....if ur spiking and it never did it before......i bet it's running lean, thats what mine did....n only when it went lean. add more fuel with the AFC.

let me know how it goes.

 

the heatshield broke due to crappy welds I think

I'm definitely NOT running lean. It's a boost spike due to the MBC. I don't spike w/o the MBC.

Anyone have any insight on this?? C'mon honda-tech'ers!!

 

Anyone who has alot of experience w/ manual and electronic boost controllers can tell you that manual boost controllers offer much much more consistant and stable boost pressure even w/ the boost spike problem.

MBC's bleed off boost to regulate the pressure going to the spring. What happens is when you floor it in a real low gear or you floor it half way in a high gear and then lay into it, you build up pressure so fast that the mbc cannot bleed off boost fast enough to control your wastegate spring.. You get an initial spike and then it quickly settles down to a stable boost level once your mbc catches up.

Since you already have the mbc as close to the wastegate and boost source as possible, you dont really have any options that i am aware of.

I always just delt w/ the boost spike on my car. A couple extra psi for 1000rpm's isn't going to hurt you. (as long as ur tuned right) It's nice when it helps get you out in front though hehe.. In your case you are hitting map limit so thats really not an option for you.

If you do get an electronic boost controller let me reccomend the Greddy profec B. This is the only electronic boost controller ive ever used that does exactly what you tell it too.. Although it does fluctuate a little bit w/ weather, and sometimes creeps in the high gears, it is still much better then the AVCR boost uncontrollable everyone seems to be all about these days..

 

how bout you try drilling out ur bleeder hole?
maybe urs is too small. u said u was gonna chunk it, minus well give that a shot.

does urs look to be about the same size(bleeder hole)?

 

might wanan check that you installed the MBC right. if its the ball n spring type. the other end of your adjustment **** is where the ball is. and that shoudl be your vac source/ nipple on the turbo. and the other side is the side that goes to the wastegate.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by project dc2 &raquo;</TD></TR><TR><TD CLASS="quote">might wanan check that you installed the MBC right. if its the ball n spring type. the other end of your adjustment **** is where the ball is. and that shoudl be your vac source/ nipple on the turbo. and the other side is the side that goes to the wastegate. </TD></TR></TABLE>

keep in mind that if its backwards it won't control boost at all..

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by DIRep972 &raquo;</TD></TR><TR><TD CLASS="quote">Anyone who has alot of experience w/ manual and electronic boost controllers can tell you that manual boost controllers offer much much more consistant and stable boost pressure even w/ the boost spike problem.

MBC's bleed off boost to regulate the pressure going to the spring. What happens is when you floor it in a real low gear or you floor it half way in a high gear and then lay into it, you build up pressure so fast that the mbc cannot bleed off boost fast enough to control your wastegate spring.. You get an initial spike and then it quickly settles down to a stable boost level once your mbc catches up.

Since you already have the mbc as close to the wastegate and boost source as possible, you dont really have any options that i am aware of.
</TD></TR></TABLE>

thanks!! I thought it was probably something along those lines. Since I'm just trying to gain 2-3 extra psi over the spring I won't be bothering w/ an electronic one. Sounds like a different wastegate spring is in my future. That's the info I was looking for, I appreciate the response.

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by B_RON007 &raquo;</TD></TR><TR><TD CLASS="quote">how bout you try drilling out ur bleeder hole?</TD></TR></TABLE>

It's a turboXS MBC, I'll probably either sell it or just hang onto it for future use when I get better fuel management.

and LOL it's not hooked up backwards! I'd be doing more than spiking a couple psi...

 

Hmm, I am just about to install one similar, a diy mbc, ball and spring type. I hope I don't run into too much boost spiking. I would be going from 5psi to 8psi on an internaly gated T3. I would try and place the mbc as close to the turbo as possible, so there is less hose as possible....