All of a sudden not boosting as high

[Sasso]

Last night I was out for a quick drive to see how my new tyres were. I have two problems, one is that when I hit my rev limiter and then shift the engine doesn't accelerate at anywhere near the rate it should and the idle is very lumy and misfires (runs rich) until it "clears" which could be a few seconds to a minute. Normally.
Anyway this time after doing hitting the rev limiter a few times (my tacho isnt working atm) the max boost isn't as high anymore. Used to boost to 15psi now jumps to 14 then goes back to 13psi. Boost controller is a turbosmart street. Turbo system is a begi S1. ECU is a wolf3D V500

What on earth could be going on? If there was a boost leak it would act differently wouldn't it?
Would there be any reason I'd have to change the SP setting on the boost controller?
Could I have damaged the turbo by hitting the rev limiter? (it causes back fires).

thanks for any help

[PT]

Sounds like you may have a leak in the intake system. Check for hoses that me not be completely on connectors, tears in any of the pipes etc..

[Benny]

Could be something's up with your boost controller.
I had a similar problem in that my car dropped its maximum boost from 14lbs down to 8 lbs for no apparent reason.

Played around with the boost controller and the boost came back.

Check the connections, both electrical and physical, and see if something's not quite right.

[Sasso]

thanks guys. Had a quick play at lunch time, i turned off the boost controller to see if it was that and its only boosting to 10, normally its at 12 with only the waste gate spring so something's up. I am getting an aweful rattling sound coming from somewhere but its hard to find. I would have thought with a boost leak that you'd still get the same max boost it would just be lagged.

[bruce]

Rattling sounds like a bit of the compressor wheel is now in your exhaust? I certainly hope not.

[Juffa]

Do you have a WBO2 gauge? If so, what is the AFR doing under full boost? I assume the you have a MAP sensor for the wolf rather than using the original AFM? Where is the MAP sensor getting its readings from i.e. before or after intercooler?
It could be that the wastegate is either opening early, or not closing properly thereby leaking boost.

Good luck.

J.

[Sasso]

The rattle is only at certain conditions and rpm, like when the engine's below idle it will rattle, and started before I was getting these problems. So I certainly hope its not the case. The turbo and engine sound perfectly fine, thats the thing. Its almost like the waste gates bent or something requiring a stronger/shorter spring arm.


Yeah have a wb, the afrs I think are around the 12.5 mark, which is normal. Yes map sensor, taken just past the throttle body (it has to be doesn't it?).
If the waste gate is opening early that would explain what's going on. Not closing properly, well if it wasnt then changing the ebc profiles shouldn't increase the boost right? Question is, is it common to suddenly have a wastegate that opens early, could burning fuel in the exhaust manifold blend the waste gate?

[Fatty]

i had similar symptoms when i had a boost leak.

my avo intercooler had a threaded hole on one of the end tanks, for a bolt that held the intercooler onto a bracket. anyway the bolt came out thus boost was leaking out. a loose bracket could also cause a rattling noise too, i suppose. probably a long shot but maybe your intercooler or pipework has some brackets somewhere that may have come loose, or a loose hose clamp etc..

oh yeh, i didn't have an ebc tho.

[Juffa]

^^^^ What Fatty said.

I had a the odd pipe clamp come loose,the pipe would slip off and I would leak boost, but usually I would suffer total boot loss, not partial.

Are you using a blow off valve.....it may not be sealing properly or the wastgate actuator diaphragm could be gone/going and allowing the wastegate to open early.

I have read on either the big forum or on the Miata Turbo forum that someone had problems with a wastegate not closing fully due to the plate being damaged or out of specification....but I think this was a problem that began as soon as the turbo had been installed....not later down the line.


J

[NMX516]

Back in the day, wastegate's were known to break if they were slammed open and shut too harshly. Could be a possibility if you've been hitting the rev limiter... A broken wastegate flap would then leak exhaust gas past the exhaust wheel, resulting in lower peak boost pressures.

[Sasso]

Juffa, yeah im using a bosch bov that begi provides with teh kit. I need to make a boost leak tester.

hmm more challenges for you...

I pulled the cat out today and the insides were crumbled. I cleaned it out, only one section of honeycomb material was left in tact. However I put it back in and still have the same problem. I still have yet to try undoing the bolts and running it like that, I couldn't see much light through the cat, lots of the holes were filled with carbon deposits, not sure if that will have a great effect or if they're cleared easily. Need a new cat now.

Next I suppose I have to check the waste gate to see if its broken.

Perhaps if I could get to the bottom of the whole rev limiter problem the boost loss cause might become apparent. I've set it to hard cut ign, hard cut fuel and hard cut both, and I think I've tried the soft cut too. It still does the same thing.

Does anyone know what could possibly be happening? I hit the rev limiter even in neutral for a few seconds (boost builds up is that normal?). And I take my foot off the throttle and the car idles like crap (like on 3 cyl) runs very rich and then dies.
Then its hard to start it again (makes a strange whining noise when cranking), need to use some throttle, and then the car runs on 3 cyl for a few minutes and eventually returns to its normal smoothness. I pulled the injector plugs off one at a time, and it seems that when I take off injector 4 the engine does not change where as with the rest the rpm drops. I pulled off the spark lead for #4 at the coil pack and the spark jumps to the plate at the back and a few seconds later the car dies.

If i hit the rev limiter when driving the car backfires (probably what blew the cat) and when I shift and accelerate in the next gear the car is very slow as if it was, i suppose, running on 3 cylinders (the boost gauge reads the right amount but the car accelerates relatively slowly). Then half a minute later the car runs fine again. Well except this time where its permanently slower.

One thing I noticed is that if i set the rev limiter to say 4krpm there isn't a problem, but at 7250 there is.

What could be happening? What I think it could be, the spark plugs are heat range 7 and gapped to less than 1mm. THe engine is either flooding or one of the cylinders spark or injectors is not working after/during hitting the limiter causing the engine to run like crap until it recovers, and for some reason backfiring.
So perhaps its not sparking and the fuel that is supposed to be burning during rev limit is being thrown into the exhaust. What could be the cause of that? Bad coil packs? Need of Iridium or platinum spark plugs?

Anyone have ideas? I'm seriously considering selling the turbo and buying a GTR (which I know I'll regret), I've yet to pass an emissions test and get it engineered but there's so many bugs on the way I'm losing patience.

[spikey]

Take out your spark plugs,see if one of them is fouling up more than the others,gap the plugs to .8mm,it could be one of the injectors sticking, so they may need a clean.

[tbro]

Sasso,
Sounds like you have a coil pack on the way out, Scooter did it to me and sh*t I had some fun checking it out(diesel mechanics hate petrol motors),does it seem to be worse after a good run and then let the car cool down?? Pull out the multi meter and test H and L voltage sides.

Terry

[Sasso]

Fixed it! well the lack of boost/power part, still have rev limiter problem.GRRR
It was my cat as we thought. The broken bits clogged up the bit still in tact and was restricting flow. I bashed it out and the car runs beautifully again. But now I have to buy a new cat.

Take out your spark plugs,see if one of them is fouling up more than the others,gap the plugs to .8mm,it could be one of the injectors sticking, so they may need a clean.

Yep checked them and they look fine. hmm yeah, thing is i think its spark related since the car goes rich after I hit the limiter so the injector might be injecting fuel but its not being burnt in that cylinder

Sasso,
Sounds like you have a coil pack on the way out, Scooter did it to me and sh*t I had some fun checking it out(diesel mechanics hate petrol motors),does it seem to be worse after a good run and then let the car cool down?? Pull out the multi meter and test H and L voltage sides.

Terry

I'll check it out. I want to see if I can reduce the gain on the rev limiter so it doesn't bounce so fast, that might help the situation.